text:
This action might not be possible to undo. Are you sure you want to continue?
Additional AIX Security Tools on
IBM pSeries, IBM RS/6000, and SP/Cluster
Customize the security of your pSeries systems Explore IBM, non-IBM, and freeware security tools Learn new approaches to security
Abbas Farazdel Marc Genty Bruno Kerouanton Chune Keat Khor
International Technical Support Organization Additional AIX Security Tools on IBM ^ pSeries, IBM RS/6000, and SP/Cluster December 2000
Take Note! Before using this information and the product it supports, be sure to read the general information in Appendix D, "Special notices" on page 211.
First Edition (December 2000) This edition applies to AIX 4.3.3. Comments may be addressed to: IBM Corporation, International Technical Support Organization Dept. JN9B Mail Station P099 2455 South Road Poughkeepsie, NY 12601-5400 When you send information to IBM, you grant IBM a non-exclusive right to use or distribute the information in any way it believes appropriate without incurring any obligation to you.
© Copyright International Business Machines Corporation 2000. All rights reserved. Note to U.S Government Users – Documentation related to restricted rights – Use, duplication or disclosure is subject to restrictions set forth in GSA ADP Schedule Contract with IBM Corp.
Preface . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . vii The team that wrote this redbook . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . viii Comments welcome . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . ix Chapter 1. Introduction . . . . . . . . . . . . . . 1.1 Security framework - Overview . . . . . . . 1.2 Security framework - Planning . . . . . . . 1.3 Security framework - Architecture . . . . . 1.4 Security framework - Implementation . . 1.5 Security framework - Monitoring . . . . . . 1.6 Security framework - Incident response 1.7 Next steps . . . . . . . . . . . . . . . . . . . . . . .. .. .. .. .. .. .. .. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .. .. .. .. .. .. .. .. . . . . . . . . . . . . . . . . . . . . . . . . .. .. .. .. .. .. .. .. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .. .. .. .. .. .. .. .. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .1 . .1 . .3 . .6 . .7 . .8 . 10 . 12 . 13 . 13 . 15 . 15 . 15 . 16 . 16 . 16 . 17 . 17 . 18 . 21 . 24 . 24 . 25 . 25 . 26 . 27 . 28 . 29 . 29 . 34 . 36 . 37 . 43
Chapter 2. Firewalls . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2.1 Misconceptions about firewalls . . . . . . . . . . . . . . . . . . 2.2 Types of firewalls . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2.2.1 Static packet filter firewalls . . . . . . . . . . . . . . . . . 2.2.2 Circuit level firewalls . . . . . . . . . . . . . . . . . . . . . . 2.2.3 Application layer (proxy) firewalls . . . . . . . . . . . . 2.2.4 Dynamic packet filter firewalls . . . . . . . . . . . . . . 2.2.5 Comparison between the different types . . . . . . . 2.3 Firewall designs . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2.3.1 Basic firewall design . . . . . . . . . . . . . . . . . . . . . . 2.3.2 Firewalls with demilitarized zone (DMZ) . . . . . . . 2.3.3 Compartmentalized firewall environment design . 2.4 Securing firewalls . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2.5 Firewalls on AIX . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Chapter 3. Check Point FireWall-1 . . . . . . . . . . . . . . 3.1 FireWall-1 features . . . . . . . . . . . . . . . . . . . . . . . . 3.2 Complementary software for FireWall-1 . . . . . . . . 3.3 Securing FireWall-1 . . . . . . . . . . . . . . . . . . . . . . . 3.3.1 Closing vulnerabilities during system startup 3.3.2 Managing FireWall-1 logs . . . . . . . . . . . . . . . 3.3.3 Securing FireWall-1 default configurations . . 3.3.4 Creating a useful rulebase . . . . . . . . . . . . . . 3.3.5 Viewing connections . . . . . . . . . . . . . . . . . . . 3.3.6 Enabling other defense mechanisms . . . . . . 3.4 List of ports that Check Point FireWall-1 uses . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
.. .. .. .. .. .. .. .. .. .. ..
.. .. .. .. .. .. .. .. .. .. ..
© Copyright IBM Corp. 2000
. . . . . . . . 6. . . . .2 Defense provided by PortSentry . . Chapter 6. . . . . . 48 . .8 SSH2 interoperability between OpenSSH and SSH. . . 6. . . . . . . . . . . . . . . . . . . . .. . . 5. . . . . . . . . . . . . 76 . . . . . 89 . . . . . . .. . . . . . . 94 . . . . . . . . . . . . . .. . . . . . . 6.1. .1 Obtaining and installing SAINT . . . . . . . . . . . .1. . . . . 5. . . . . . . . . 98 .2 Complimentary software for IBM Secureway Firewall . . . . . . . . 6. . . . . . . . . .5 List Open Files (lsof) . 49 . . . . . . . . . . 5. .1 Obtaining and installing PortSentry. . . . . . . .2 Using NSA . . . . . 95 . . . . . . . . . . . . .4. . . . 77 . . . 6. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .1 Secure Shell (ssh) . . . . . . . .1. . . 49 . . . . . . . . . . . .. . . . . . . . . .7 Other interesting SSH daemon configuration options . . . .6 OpenSSH using SSH2 . . 77 . 47 . . . . 78 . . . . . . .. . . . . . . . . . . . . 5. . . . . . .2 Using SAINT. . . . 83 . . . . . . . . . . .. . . . . . .3 Additional TCP Wrapper security features . .2 Network Mapper (NMAP) . . . . . . . . . . . . . . . . . . . . . .9 SSH clients for the PC . . . . . . . . . . . . . .11 Alternatives to SSH . . . . . . . . . . . . . . . . . . . . . . . .2 Difference between SSH1 and SSH2 . . . . . . . . . . .. . . . . . . . . . . . . . . . . . . . . . . .10 Implications of having SSH . . . . . . . . . . . . . .4. . . . . . 5. . . . . . . 4. . . . . . . . . . . . . . . . . . . . 6. . . 5. . . 59 . .3 Security Administrator's Integrated Network Tool (SAINT) 6. . . . . . . . . . . . . . . . 4. . . . . .1 Obtaining and installing fping . . . . . . . . .. . . . 5. . . . .2 Using fping .1 IBM Secureway Firewall features . . . .1. .1. . . . . . . . . . . . . . . . . 65 . . . . . . .4 PortSentry . . .1. . .4. 4. . . . . 103 . . . . . . . .2. . . . . . . .4 Network Security Auditor (NSA) . 5. . . . . . .. . . . .3. .2. .. . . . . . . . . . . . . . . . . 61 . . . . .1. . . . 94 . . . . . . . . . . . . . . . . . . . . .2. . . . . . . . . . . . . . . 5. 103 iv Additional Security Tools for AIX Systems . . . . . . .. . . . .. Port and network scanning . . . . . . 51 . . . 82 Chapter 5. . . .. . . . . .. . . . . . . . . . . . . . . . . . . . . .2.1 Obtaining and installing TCP Wrapper . . . . . 98 . . . . . . . . . . . . .5 OpenSSH using SSH1 . 6. . . . . . 71 . . . . . . . . . . . . . . . . . . . . .. . . . . . 50 . . .3 Protection against ping sweeps . . 88 . . . . . . . .1. . . . . . .1. . . . .. . IBM Secureway Firewall . .. 90 . . . . . . . . . . . . . 84 . . . .. . . 5. .1. . . . . . . . . . . . . . . . . 77 . . . . . . . . . .1 Obtaining SSH . . . . . 92 . . . . . .. . . . . . . . . . . . . . . . . 68 . . . . . . . . . . . . . . . . .4. . . . . .1. 4. . . . .. . 79 . . . .. . . . . . . . .4 Installing OpenSSH on AIX. . . . . . . . . . . . . . . . . .1 fping . . . . . . . . . . . .. . . . . . . . . . . . 4. . . . . . . . . . . . . . 49 . .2 TCP Wrapper . . . . . .. . . . . . . . . . . . 5. . 6. . . . . . . . . . . .. . 47 . . . . . . . . . . . .1. 6. . . . . . . . . . . . . . .. .. . 59 . . . . . . . . . .1 Obtaining and installing nmap. . . . . . . . . .Chapter 4. . .1 Installing NSA. . . . . . . . . 99 . . . . 62 .3 Key concepts of SSH . 85 . .3 Firewall hardening . . . . . . . . . . . . . . . . . . 75 . . . . . . . . . . . . . 5. ..3 Interpreting NSA output . . . . .3. . . . . . . 5. 5. .. . . . . . . . . . . . . . . . . Secure remote access . . . . . . . . . . . 4. .. . . .2. 6. .Com 5. . . . . .. . . . . . 76 . 86 . . .3 Protection against port scanners . . . . . ..1. . . . . . . . . . . . . . . . . . . . .2 Configuring TCP Wrapper. . . . . . 6. . . . . . . 5. . .4. .. . . . . .1. . . . . . . 4. . . 6. . . .2. . . . . . . . .2 Nmap usage . . . . . . 6. 62 . . 6. . . . . . . . . .
. . . . . . . . . . . . . . . .. .3. . . . . . . . . . .. . . . .. . . . . . 118 . . . . .. . 8. . . v . . . . . 148 . . . 7. . . . .3 Removing entries from /etc/inetd. . .6 Securing X11 . .. . .. . . . . . . ..3. . . . .. . . 119 . . . . . . . .. 109 . .. ... . . . . . . . .. . . . . . . .. 7. . . .1. . . .3. . 141 . . .5 Trivial File Transfer Protocol (TFTP). . . . . . . . . . . . . . . . . . . . . . . . . . .4 Protecting your private key .. . System and data integrity . 7. . . .. . . . . . .1 Obtaining and installing Tripwire . . . . . .. . . . .. 140 . .. . . . . . . . .. . . .. . 105 6. . . . . .6 Intrusion detection . .. 8... . .. . . . 7. 7. . . . ... . . . .2. .3 Pretty Good Privacy (PGP) . . . . . . . . . .. .2 Obtaining and installing PGP . .. . . . . . . 122 . . .3. . . .. .. 118 . . 8. . 111 . . . . . .3 Step 2: Tighten configurations of remaining services . . . 8. . . .1. . . . 7. . ... . . .4. 110 . . . . . . . . . . .2 John the Ripper . . . . . . . . . . . 124 .4 MD5 . . . . . 8. . . . . . . . . . . .2 Configuring John the Ripper . . . . 181 . 7. . .. . 8.. 136 . . . . . . . . .8 Protecting TCP services using SOCKS. . .. . . . . . . . . . . . . . . . . ..3. . .3. . 8. . . . 7. . .. . .3. . . . . . . . . . . 124 . . . . . .. . . . . . .. . . . . . . 134 . .1 Obtaining and installing John the Ripper 7. . .. . . . . . . . . 7. . . . . . .1 Removing entries from /etc/inittab . . . . 127 . . .3 IP routing options . . . . . . .5. . . . 7. . . . . . . 8. .. . .3. . .. .2 Removing entries from /etc/rc.3. . . . . . .. .4 Step 3: Set proper network (no) options . . . . . . . . . . . . . . . . . . . . . . . 8. . . 8.. . . . . . . . . . . . .1 SYN attack protection . . . . . .2. .. .. . 153 . . .6. . . . . .4.. .1. . . 180 . . .2. . . . . . 8. . . . 114 . . . . . . .. . . .. . . . . . . .. 8. . . . . . . .. ..1 Domain Name System (DNS) . . .. . . .. . . . . . . . . . . 142 . . . . . 8. 188 Chapter 8. . . . .6 Alternatives to Tripwire . . . 182 . . . 121 . . .. .4 Comments on configuration . . .2 Using lsof . . . . . . . . . . . . . . . . . .. . .. . . . . . . . . . . . 144 . . . . . . .5. . . .1 Installing lsof . . . 8. 139 . . . . . . . . . . . . . . . . . . 8. . . . . .tcpip . . . . . . . . . . 153 . . . . . 8. . . . .1 Tripwire . . . . . . 168 . 186 . . 119 . . . . . .. . . . . . . . . . . . . . . . . . . . . . 187 . .1 Overview . . . . . .3 Configuring Tripwire . . . . .1 Ensuring the integrity of downloads . . . . .conf. . 7. . . . . . .7 File Transfer Protocol (ftp) . . . . . . . . . . . . . . . . . 7. .. . . . . . . . . .. . . . . .1.. 7. . .5 When should Tripwire be run . .. . .. . . .. . .. . . . . .3. . . . 175 . . . . . . . . . .2. .2 Step 1: Remove unnecessary services . . . . . . . . . . . . . . .2. . . . . . .3 Simple Mail Transfer Protocol (SMTP) . .. . . . . . . 120 . .. . . . . . .. . . . .. . . . . . . . . . . . . . . . . . .. . 7. . .. . . . . . . . . . . . . . . . . . . . . . . . . . . . . 126 . . . Securing AIX. . . . . . 8. . . . .. .3. .. . . .2 Network File System and Network Information Service . . . . .. .4 Simple Network Management Protocol (SNMP) . . . . . . . .. .. . .4. . . . . . . 7. 8. . . . .. . . . . . . . . . . . 106 Chapter 7. . . . . . . . . . . . . . . . . . . .3. . ... . . . . . . . . . . . ... . . 187 . .1. . . . . . .. . . .. . . .4. . . . . . . . . . . 186 . . . . .1 PGP basics . . . . ..3 Using PGP . . . . . . . . . .. . . . . . . . . . . . . .. . 184 . . . . . . . . . . 7. . .2 Configuring and using Tripwire . . .. .. 104 6. 134 . . . . . . . 112 . . . . . . . . . . . . . . . . . . . . . . . .2 Broadcast protection. . .. . . . . .2.. . . . . . . . .1. 7. . . . . .3 Using John the Ripper . . . . ... . . . . . .. . . . . .. . . . . .
. . . . 190 .. . . . . .5. . 8. . . .4 Other attributes . . . . . . . . . . . . .8. . . . . .5. . . . . . .. . . . . . . . . . . . . . . . 8. . . . .2 IBM Redbooks collections. . . . . . . . . . . . . . . . 8. . . . . . . . . . 8. . . . . . . . . . . . . . . . . . . . . . . .. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .4 Referenced Web sites. .. . . . . . . . . . . . . . . . . . . . .. .4 Monitor cron and at jobs . . . . . . . 194 . . . .. . . . . . . . . . . . . . . . . . 205 Appendix B. . . 8. . . . . . . . . . . 215 E. . audit trails.6. . 189 .2 Password cracker utility . . . . . . .8. . . . . .. . . . . . . . . . . .2 Enable auditing. . . . . . . . . . . 8. 193 . . . . . . . . . .. . . . . . . . . . . .. . . . . . . . . . .5 Step 4: Tighten up user accounts . 201 . . . . . . . . . . . .8. . . . . . . . . . and system behavior . . . . . . . . . 189 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 216 E. . . . . . . . . . . .3 Securing root . . . . . . . . 201 . . . . . . . . 8. . . . . . . . . . . . . . . . . . . . . . Related publications . . . . . . . 209 Appendix D. . . .. . . . . . . . . . . . . . .1 Monitor system logs . . . . . . . . .. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .1 IBM Redbooks . . . . .5. . . . . . . . . . . . . . .3 Other resources . 215 E. . .1 Removing unnecessary default accounts . . . . . . . . . . . . 200 . . . . . . . . . . . .6. . . .6 Step 5: Set up strong password policy . . 197 . . .. . . . 192 . 221 IBM Redbooks fax order form . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 8. . . . . . NSA Scan Options. . . . . . 207 Appendix C. . . . 216 How to get IBM Redbooks . . . . . . . . . . . . . . . . 223 IBM Redbooks review . . . . . . . . . . .2 Setting user attributes . . . . . . . . . . . . . . . . . . . . . . . . . . . . .7 Step 6: Install additional security tools . .. . . 202 . . . . . . . . . . . . 211 Appendix E. . . . . . . . . . . . . . . . . . . . . . 203 Appendix A. . . . . . . . . . . . . . . . 8. . . . . . . . . . . . . .5. . .3 Monitor files and directories . . 215 E. . . . . . . . . . 8. . . . 197 . . Special notices . . . . . . . . . . . . . . . . . .8. . . . . . . . . . . . . . 194 . . . . .1 Modifying user password attributes. 8. . . . . . . 8. . . . . . . . . . . . . . . . 8. 222 Index . . . . . . . . . . .8. . . . . . . Script used to scan a network with fping . . . . . .. . . . . . . . . Script to merge the AIX passwd files . . . . . . . . . . . . . . . . . . . . . . . .8 Step 7: Monitor logs. . . . . . . . . . . . . . 243 vi Additional Security Tools for AIX Systems . . . .
be it all RS/6000 SP. we cover third-party software that is readily available. this book is primarily aimed at Information Technology (IT) professionals responsible for managing and securing their server environment. we work from the application layer at the top to the network layer at the bottom. We assume. From firewalls to operating system hardening. or a mixture of both. and assorted techniques that can all be used to provide enhanced security in your environment. PSSP. 2000 vii . Along the way.3 Elements of Security Effective and Efficient Implementation. in an SP environment. SG24-5521 • This redbook Like the others. modifications to the standard software that comes with AIX and PSSP. As we move through these servers. at a minimum. the viability of e-commerce is critically dependent on the secure flow of information.Preface Information is one of your most important assets in the digital economy. Subjects covered in this redbook include: • Firewalls • Secure Remote Access • Network Mapping and Port Scanning • System Integrity • Securing AIX © Copyright IBM Corp. This redbook is the third in the security redbook trilogy: • AIX 4. The approach taken is from outside to inside and top to bottom. this redbook illustrates additional tools and techniques that you can use to enhance the security environment of your IBM RS/6000 and IBM ^ pSeries. SG24-5962 • Exploiting RS/6000 SP Security: Keeping It Safe. all RS/6000 standalone. Whether in an online store or a complex Internet-based commodity exchange. We move from the servers on the far reaches of your network that are visible to the outside world to those on the innermost recesses of your intranet that contain your most confidential data. that you are familiar with AIX and.
He is currently the Global Web Architecture (GWA) AIX Architecture Team Lead in Boulder. and Senior Project Manager at the International Technical Support Organization. Farazdel worked in the Global Business Intelligence Solutions (GBIS) group at IBM Dallas as an Implementation Manager for Data Warehousing and Data Mining Solutions and in the Scientific and Technical Systems and Solutions (STSS) group at the IBM Thomas J. Jeff Quaintance viii Additional Security Tools for AIX Systems .The team that wrote this redbook This redbook was produced by a team of specialists from around the world working at the International Technical Support Organization. in Computational Physics from the University of Massachusetts. Bruno Kerouanton is a System and Security Engineer working for Sysicom in France. and DCE/DFS. Colorado. He is an AIX Certified Advanced Technical Expert and has received Check Point CCSA and CCSE certifications. Chune Keat Khor is an IT Availability Specialist from IBM Singapore. Technical Consultant.Sc. He was also a contributing author of the book. He has worked in UNIX environments for 10 years and is an RS/6000 Certified Advanced Technical Expert (CATE). Dr. Thanks to the following people for their invaluable contributions to this project: IBM Boulder Tom Kleespies. Watson Research Center as a High Performance Computing Specialist. Austin Center. His areas of expertise include UNIX. His areas of expertise include network and system security including penetration tests and architecture design. AIX. SG24-5521. RS/6000 SP. Bruno is an RS/6000 Certified Advanced Technical Expert (CATE). Abbas Farazdel is an SP System Strategist.D. He holds a BS degree in Manufacturing from Colorado State University. He also holds CCSA and CCSE certifications for CheckPoint Firewall-1/VPN. He joined IBM in 1998 after graduating from National University of Singapore with a bachelor's degree in Electrical Engineering. Marc Genty is a Systems Management Integration Professional working for IBM Global Services at the Western Geoplex Service Delivery Center in Boulder. Exploiting RS/6000 SP Security: Keeping It Safe. HACMP. Dr. in Computational Quantum Chemistry and an M. He has four years of experience with AIX and RS/6000 SP system administration and support. Poughkeepsie Center. Before joining the ITSO in 1998. Farazdel holds a Ph.
Please send us your comments about this or other Redbooks in one of the following ways: • Fax the evaluation form found in "IBM Redbooks review" on page 243 to the fax number shown on the form. • Use the online evaluation form found at ibm.com ix .ibm.IBM Poughkeepsie Chris Derobertis.com/redbooks • Send your comments in an Internet note to redbook@us. Larry Parker Comments welcome Your comments are important to us! We want our Redbooks to be as helpful as possible.
x Additional Security Tools for AIX Systems .
SG24-5521 The purpose of this redbook is to provide you with information about additional security tools (both IBM and non-IBM) and techniques that can be used to further enhance the security of your AIX 4. IBM has always been serious about security and has unparalleled experience designing and implementing secure systems.3 is covered in the redbook: • AIX 4. 2000 1 . December 1996 Internet World Information is one of your most important assets in the digital economy. Lou Gerstner. Once the security framework has been described.Chapter 1. the IBM RS/6000 and the new IBM ^ pSeries servers deliver a complete security package that you can count on from one end of your enterprise system to the other in a flexible.2 environments. from planning to architecture to implementation to ongoing support. Many of the tools described here are available for download from the Internet. we go on to cover some of the tools and techniques you can use to implement it.Overview This book begins by describing a framework for security.3 and/or PSSP 3. For this reason. The framework © Copyright IBM Corp. Introduction "More than any other single factor.2 in the redbook: • Exploiting RS/6000 SP Security: Keeping It Safe. SG24-5962 and that of PSSP 3. Your environment will only be as secure as your weakest link. the potential of e-commerce hinges on people's confidence that the network can keep confidential transactions confidential. easy-to-manage manner.3 Elements of Security Effective and Efficient Implementation. Whether we are talking about an online store or a complex.1 Security framework ." IBM Chairman. The security infrastructure shipped with AIX 4. By using this knowledge and leveraging services based on open standards. it is critically important to take a holistic view of security. the viability of e-commerce is critically dependent on the secure flow of information. and private records private. 1. Internet-based commodity exchange.
of the previous phases on its way toward resolution.This is where you design your environment to meet the requirements defined in the Planning phase.This is where the rubber meets the road. 2 Additional Security Tools for AIX Systems . we see: • Application software • Operating system • Network (hardware and software) • Physical server and network media Each element in the environment and each layer of each element needs to be taken into account when building your security framework. A problem discovered here should pass through some. and you build what you designed in the Architecture phase. likely. Planning . Monitoring . 2. The security approach we take is top-down. you need to continuously monitor it for vulnerabilities and suspected attacks. this step is performed at the corporate level and. if not all.This is where you define your overall security policies and goals. In many organizations. has already been completed.provides both the context and the direction for which tools and techniques you use and how you use them. 3. Architecture . 4. The topology of a typical eBusiness environment is structured something like the following (as viewed from the Internet side): • Boundary routers • External firewalls • Public servers in the demilitarized zone (DMZ) • Private network in the DMZ • Internal firewalls • Private internal servers • Private internal network Also. The steps to building a security framework and filling in the structure are as follows: 1. Implementation .Once your environment is operational. viewing each of the servers top-down. This phase forms the feedback loop for all of the previous phases.
There are many good books on the subject of security planning and architecture. we refer you to those other two books when appropriate so as not to duplicate detailed information contained there. There is a lot that you can do in terms of security for not a great deal of money (80 percent security . the damage done to the reputation of your organization should it be compromised Chapter 1. Some of the questions that should be answered during this phase are: • How much security do you need? • How much security can you afford? • What is the nature of the enemy? The first two questions are interdependent. The focus of this book is primarily on security implementation. a server in a DMZ that can be easily reconstructed should something happen to it typically does not warrant the same level of security that you would give to an internal database server housing confidential information. The absolute worst time to begin working on this phase is after an attack has already occurred. Even though a public Web server does not contain confidential information. In this chapter.2 Security framework . you will want to be well prepared. In general. You must also weigh the value of the assets you are trying to protect with the amount of money you are allocating for security. This is another place where the 80/20 rule holds. you should expect to pay a premium for it (additional 20 percent security . Time spent in the beginning considering how you would respond to a real attack will pay for itself many times over if you ever find yourself confronted with the real thing. there are also intangibles that you need to take into account. the more it will cost. However.Planning The purpose of this phase is to define the overall security goals and policies for your organization.This is the phase that you hope you will never have to go into. Incident response . we cover all of the phases and give you ideas on things to consider when you work through them for your organization. but if you need very high security. For example. and. 1. tangentially.additional 80 percent money). monitoring.20 percent money). the more security you need. However. if the worst should happen.5. incident response. Introduction 3 . Think of this as the "peace of mind" phase. Throughout the book. Keep in mind as you read it that it is meant as a companion to the other two security redbooks mentioned at the start of this chapter.
can be huge. Reputations take a very long time to establish and a very short time to destroy. Finally, you need to be realistic in your planning. Having elaborate security goals and policies is all well and good, but you must also back them with the funding for the staff to support them. System and network administrators typically have their hands full just trying to keep the systems running and maintained. Depending on your needs, you may want to consider staffing a separate security team. At the very least, consider having a security lead within the ranks of your system and/or network administration team.
"If you know the enemy and know yourself, you need not fear the result of a hundred battles"
Sun Tzu, The Art of War A big part of security planning is threat assessment. Even though attacks from the outside are what we hear about most often, attacks from the inside are far more common, but, for obvious reasons, rarely publicized. Your planning should take into account both groups. A good starting point for learning how to understand your enemy is detailed in the book Hacking Exposed: Network Security Secrets and Solutions . Through detailed, real-world examples, this book teaches you how to think like an attacker. In it, the authors outline the typical methodology used by would-be attackers to size up their targets. The steps of that methodology are as follows: 1. Target acquisition and information gathering 2. Initial access 3. Privilege escalation 4. Covering tracks 5. Planting back doors A brief explanation of each step is given here. For a more thorough explanation, refer to the book ( Hacking Exposed ). Target acquisition and information gathering This step can be broken into three phases: • The first phase is footprinting , where the attacker attempts to find out as much as possible about your environment. Your IP address range(s) and DNS information are prime targets during this phase.
Additional Security Tools for AIX Systems
• The second phase is scanning. Having acquired your IP address range(s) and/or DNS information, the attacker now starts probing your systems looking for active ports. Tools, such as NSA, SAINT, fping, and nmap, which are all covered in this redbook, are commonly used during this phase. • The third phase is enumeration . This phase is much more intrusive than the previous one. Having narrowed the target to specific systems, the attacker now attempts to find a hole that will enable initial access into one or more of your systems. Banners, default users, and poorly-configured network resources are all prime targets during this phase. Operating system hardening and strong password policy (both covered in this redbook) are two of the most effective defenses against this phase. Initial access The attacker next attempts to penetrate the system. The initial access is typically not root access, but no worry, that will come next. In this step, the attacker uses things, such as social engineering, password guessing, password cracking, or buffer overflow techniques, to gain the first toehold into your systems. There are many tools and techniques described in this redbook to help you prevent this from happening. We also cover additional tools and techniques that can act as an early warning device to suspicious activities and alert you prior to the attacker moving to the next step. Privilege escalation Once root is compromised, all is compromised (at least on this system). This is every system administrator's worst nightmare. Many of the same techniques used in the previous step apply here, but now the attacker has the luxury of actually being on the system, which makes the job considerably easier. In addition to the tools and techniques for protecting normal user accounts, there are additional considerations and steps for root. They too are covered in this redbook. Covering tracks Having gone through all the work in the previous steps to gain access to the system, the last thing the attacker wants is to be discovered and have all that work go for naught. Altering log files, configuration files, and mimicking normal system user behavior are but some of the tricks the attacker uses to not be detected. Your first defense here is to know what "normal system behavior" looks like. There are many monitoring tools (system-provided and third-party) to help you with this. In addition, tools, such as Tripwire, provide a baseline snapshot of your critical system directories and files for you to
Chapter 1. Introduction
compare things against. We cover both system monitoring and Tripwire later in this redbook. Planting back doors The attacker knows full well that the door used to enter the system may not be there when needed again. Like any good burglar, the attacker wants to make sure that there are multiple points of entry available should the need arise to again visit the scene of the crime (and, in the case of the attacker, the need almost always arises again). To this end, the attacker plants backdoors and Trojan horses, not only to secure future access, but to also, hopefully, gain enough additional information to be able to launch successful attacks on other systems in your environment. The defense tools covered in the previous step also apply here, especially tools like Tripwire. Of course, internal attackers typically have the advantage of being able to hide under the cover of a normal user account. Beyond that, though, their methods are quite similar to their external counterparts, even though their motives probably are not. Once you have defined your overall security goals and policies, both defensive and offensive, you are ready to move on to laying out your security architecture. It is important to remember that time invested in the early phases (such as planning and architecture) pays off by orders of magnitude in the later phases.
1.3 Security framework - Architecture
In general, security requirements differ across environments. Security requirements for an isolated lab environment are quite different from those for a large eCommerce site. The primary focus for the first is on physical access controls, whereas the primary focus for the second is on preventing attacks. In the architecture phase, you examine your environment and plan your high-level defenses. Some of the questions to consider are: • What are the weakest points in your environment? • What type of attacks are you expecting? • From where do you anticipate the attacks to originate? • Do you concentrate most of your effort and resources on the perimeter, or do you set up rings of defense, with the perimeter being the outermost ring?
Additional Security Tools for AIX Systems
The specific questions (and answers) depend not only on the type of environment you have, but also on whether or not it is a new or existing environment. For example, fortifying a DMZ is a much different task than creating one. Additionally, when planning your architecture, don't forget to take into account attacks from the inside as well as those from the outside. Think of this phase as a chess match: • How do you plan to protect the king? • What strategy do you plan to use to out-fox your opponent? • How will you recover if your initial defenses falter? • Should you use subterfuge to try and throw him off? • What will you do if your opponent does not use the strategy that you are expecting? As you lay out your architecture, it is very important to keep in mind funding and support considerations. You need to build something that can be supported in terms of cost, effort, and expertise. Architecting an unsupportable security environment is, in some ways, worse than having no security environment at all. You are lulled into a false sense of security by your paper architecture, which bears no resemblance to what is actually in place. Above all else, be realistic when developing your security architecture, and, if possible, include input from the people who will ultimately have to support your design. Two excellent books to consult during this phase, especially when considering strategy, are The Art of War, ISBN 0-1950-1476-6, by Sun Tzu, and Information Warfare and Security, ISBN 0-2014-3303-6, by Dorothy E. Denning. In addition, the tools and techniques covered in this redbook can be used to provide some of the "bricks and mortar" for your design.
1.4 Security framework - Implementation
This phase also depends on whether or not you are working with a new or existing infrastructure. Retrofitting security to an existing environment is much more complicated than building it from scratch. You have to take into account existing production services and plan your changes in such a manner as to not disrupt these services. Tools, such as IPSec, TCP Wrapper, and, especially, PortSentry, are tricky to configure properly on the first attempt. You should test them thoroughly before implementation and monitor them closely afterwards to be certain that you have not inadvertently denied access to legitimate clients.
Chapter 1. Introduction
A methodical approach to this phase will serve you well. Here are some possibilities: • Start with servers on the perimeter of your network and work your way back to the servers on your internal networks, or vice versa. • Implement by server type. For example, all firewalls, then all Web servers, then all mail servers, and so on. • Start with a specific security package, such as IPSec or TCP Wrapper, and implement that on all designated servers; then, move on to the next security package. • Work from the bottom to the top. Start with the physical layer (physical security); then, move to the network layer, then the operating system layer, and, finally, the application layer. Which ever methodology you pick, stick with it throughout your implementation phase, and document the configuration as you go. It is a very good idea to keep a complete set of your system and security documentation, such as listings of configuration files and filter rules) stored offline. In the event of a breach, this documentation becomes invaluable for damage control and postmortem activities. One of the primary goals of this redbook is to provide you with the information you need to successfully implement your security environment with some or all of the tools and techniques covered here. It is important to understand that this phase, in particular, is iterative. Security implementation is not a one time thing. Discovery of new vulnerabilities in software and hardware requires that you routinely revisit your implementation to apply new patches, update configuration files and lists, and, at times, replace ineffective tools.
1.5 Security framework - Monitoring
So, now that you have your security environment set up and operational, the next phase involves adding a feedback loop to the previous phases. In this phase, you implement system and security monitoring. Both automated and manual monitoring should be considered here. The goal is to develop a reliable system that provides you with early warnings of suspected attacks. There is, however, a very fine line between too little information and too much information when it comes to this type of monitoring. With too little information, you run the risk of missing suspicious activities early enough to take the necessary preventative action. With too much information, you also run the risk of missing something important, but, this time, it is because it gets
Additional Security Tools for AIX Systems
access_logs. and so on) • Network performance statistics (netstat. • Fully-automated monitoring follows the set logic pattern that is built into the scripts. Performing a system health check every morning (at least on a random subset of your systems) keeps security in the forefront of your mind. ISBN 0-6717-2688-9. sulog. • Manual monitoring requires you to think about security on a daily basis. Do both. and so on) • Special logs provided by the additional security tools you have installed • Audit logs • System logs (syslog. consider using multiple tools and multiple data sources to cross-check the information provided by each of the tools and logs. over time. Here are some of the reasons why: • It is too easy to take fully-automated monitoring for granted and. Introduction 9 . A combination of automated and manual monitoring is a better solution. • Manual monitoring helps you develop a feel for the normal performance of your systems and environment. and so on) • System errors (errpt) • System performance statistics (vmstat. firewall logs. generally.lost in all of the detail and background noise. Like a good newspaper reporter. Here are some of the areas to consider for monitoring: • Application logs (httpd_logs. each has its own Chapter 1. become complacent. Tools are not perfect. netpmon. A great illustration of this point can be found in The Cuckoo's Egg: Tracking a Spy Through the Maze of Computer Espionage. Also. This empirical data often proves to be a far more useful early warning indicator than any of the data coming out of the automated processes. lastlog. it is. you can follow an infinite number of paths and make unexpected linkages that would be impossible with automated monitoring. not a good idea. wtmp. topas. • With manual monitoring. failedlogin. It takes time and experience with the data to find the balance that works best for you. by Clifford Stoll. iostat. and so on) • Physical access records • Critical system file and directory permissions and ownership Even though it is possible to automate the entire monitoring process. automated and manual. and individual logs do not capture everything. verify your sources.
ers. you should still designate a small team of people who have a thorough knowledge of the incident response policies and procedures and can take control of the situation when a breach is discovered. visit: http://www. the first step in the process is to identify your incident response team. and regularly rehearsed. Even if you have contracted out your emergency response services (ERS). so that you have more than one baseline to use as a reference when investigating system anomalies. The goal of this phase is to be in a position such that. but that is exactly why it should be thought about. It is also extremely important for everyone in your organization to understand that this team is in total control in the case of a breach or suspected breach. you know exactly what to do and how to do it. Like any professional team. One final note to close of the discussion of these first four phases.ibm. there are a number of professional services companies (IBM being just one) that can help you through the process. if the worst happens.Incident response Nobody likes to think about this phase. To find out more about the IBM Emergency Response Service. or even if your organization has a corporate-level ERS team. practice. What you are striving for is an overall picture and feel for the health of your environment. They will even be there for you should the worst happen. your incident response team should have one single leader who has the final say on all investigative activities. planned for. If you do not feel comfortable tackling these processes alone.6 Security framework . where a simulated breach is identified and dealt with. 10 Additional Security Tools for AIX Systems .com/ 1. practice. they should practice. It is every system administrator's worst nightmare. Be sure to keep several historical copies of the snapshots as well. It is also a good idea to take a snapshot of each of your systems periodically and store the information on a different system and/or offline. your incident response team springs into action like a well-oiled machine. In other words. The absolute worst time to figure out how you will respond to a security incident is after one has already occurred. Additionally. Consider implementing quarterly dry-runs. So.strengths and weaknesses. and they should all look to this team for all command and control decisions. and you find that you have to move on to the next phase (for real).
application logs. directory and file permissions. rational decisions needed in a situation like this. 8. Do not wait too long before calling in additional experts to help. Work methodically through the environment. This is why it is a very good idea to have a neutral third-party in charge of the incident response team. That. inspect each item on the list in the order identified on the list. In the case of incident response. Document everything as you go. the people responsible for the day-to-day administration of the systems are too close to the situation emotionally and do not have the perspective necessary to make the calm. 5. 3. system error reports. source code files. This is extraordinarily difficult to do. Chapter 1. Remember that it does not take long for the tail of evidence to grow cold in a crime scene investigation. Identify the suspected scope of the breach. Speculation is fine. Introduction 11 . 6. The investigation cannot occur without it. Your first instinct is to shut everything down so that the attacker cannot get back in. system configuration files. and may destroy any chance of actually identifying and catching the attacker. Typically. either from outside in (external attack) or inside out (internal attack). Start with the application layer and work down. and so on. Work methodically through each system. you have the added challenge of not knowing if the attacker has fled the scene of the crime. you must attempt to conduct your investigation in a manner that will not alert the attacker to your activities. Have a predefined list of items to look at on each system. Validate assumptions with facts and data. and make sure that the conclusions can be backed up with hard evidence. but do not be too quick to jump to conclusions. 4. You have to assume that the attacker is still present. however. This. especially on an emotional level. Start by outlining what is known. So. is not to say that their expertise is not needed. Additional items can be inspected as needed. fundamentally changes the crime scene. output from system commands. at a minimum. audit logs. Incident response should follow a systematic approach similar to the following: 1. 7. however. but. 2.Think of responding to an incident in terms of a crime scene investigation. You need to gather forensic evidence in such a way as to not contaminate the scene. or start with the network layer and work up. and update your outline of what is known. The list should include things like system logs.
fr/ If you have never visited this site before.7 Next steps The remainder of this redbook covers additional tools and techniques you can use to build or enhance your security environment. 12 Additional Security Tools for AIX Systems . it contains a wealth of other software for AIX. Many of the tools covered in this book are available for AIX in installp format from the Bull site at: http://www-frec.Keep this final phase in mind as you read through the remainder of this redbook. For each of the tools and techniques. It begins with a discussion of firewalls and ends with a discussion of operating system hardening. top-down perspective. In addition to the security tools. think about what would be of value to you during the investigation of a security incident. we encourage you to go there and browse.bull. The material is roughly organized from an outside-in. Additional information about incident response in the form of step-by-step guides is available (for a fee) from: http://www.org/ 1.sanstore.
It is impossible to predict all possible attacks that may be attempted. 2. Attackers will be able to capitalize on the vulnerabilities of the Web server using legitimate commands from their remote client through the firewall to the Web server. keeping up to date with the latest attack methods as well as product patch or release levels is a good idea. switches. elements of uncertainty should be eliminated or at least minimized in a secure environment. hardware solutions usually have superior performance. In general. if you have a badly-configured Web server that has security problems. It is typically set up at the periphery of a network. For example. The total security of a network depends on its weakest link.Chapter 2. properly-configured firewalls (together with properly-configured routers. Firewalls can be implemented as hardware or software solutions. Hardware solutions are simpler and. having a firewall will not be sufficient. and Internet servers) go a long way in providing good protection against most forms of attack. © Copyright IBM Corp. 2000 13 . Since new exploits are developed or discovered constantly. whether it is between the internal and external networks or between different segments of the internal network (for example. Having alternate paths may weaken the security posture and create an element of the unknown because of the additional vulnerabilities opened up through the alternate path. not as sophisticated as their software counterparts. For firewalls to properly do their job. we will focus on the software solutions. all network traffic must be routed through them. but must be used in conjunction with other security elements. You may liken a firewall to the security post at the entrance of a high-security area where the guards will allow only vehicles with appropriate passes to pass through. between departmental LANs). Firewalls can protect against most known forms of direct attack. In this book.1 Misconceptions about firewalls A big misconception is that firewalls provide all the protection required for a network. Firewalls A firewall is a system designed to prevent unauthorized access to or from a private internal network. Dial-up connections within the network to independent ISPs is an example of an alternate network path. However. In general. This is untrue. typically. Firewalls can be the primary security enforcer. Having alternate network paths defeats the purpose of having a firewall.
Since Java and ActiveX exploits are based on programming problems. will not be allowed through the firewall. it is important to keep all logs (system and firewall) in a safe and trusted location and to maintain regular offline backup copies of them as well. the logs can prove invaluable to the security experts doing the analysis and tracking. Another common error is to leave firewalls in their default configurations. the firewall will be unable to block such an attacker. it is important to stay up to date with new vulnerabilities (through firewall vendor Web sites. Java and ActiveX filters are not enabled by default in Check Point FireWall-1. mailing lists. Many system administrators do not bother with logging because either they do not realize its importance or they are under the misconception that it is unnecessary. If an attacker steals a password or guesses it correctly. With this in mind. Oftentimes. provide protection from Java and ActiveX exploits by giving the option to filter out all Java and ActiveX code through the firewall.org. Firewalls do not provide protection for password breaches. and so on). firewalls have difficulty determining which user is authentic and which is not. it is possible to detect such activity by carefully watching the logs. it is important to implement strong passwords on AIX (see Section 8. firewalls cannot reliably decide which code is good or bad. CERT advisories at www. Therefore. For example. Logging becomes critical when a security breach occurs.A firewall does not provide protection in server exploits where a legitimate client accesses a legitimate server on a legitimate port. They will probe and scan the network looking for potential weaknesses. "Step 5: Set up strong password policy" on page 194. Another area where there is typically a lack of focus is logging. be they well written or poorly written. Vulnerabilities on the servers themselves may be exploited by attackers to gain unauthorized access to the servers themselves. As such. Some firewalls. Additionally. As long as someone has the password (by whatever means). and close them in a timely manner. With this in mind. if a break-in attempt does occur. 14 Additional Security Tools for AIX Systems . for more information on how to implement strong passwords). such as Check Point FireWall-1. By filtering all Java and ActiveX code.6. Hackers will typically test the site for weak spots prior to launching an attack. all programs written in these languages. it is important to stay current with security patches (operating system patches and application patches) and maintain rigorous control of the system configurations on the servers themselves. Default configurations are typically insufficient and may leave certain known vulnerabilities open.cert.
2 Types of firewalls There are four architectural models for firewalls: • Static packet filter firewalls • Circuit level firewalls • Application layer (proxy) firewalls • Dynamic packet filter firewalls Each is briefly described in the following sections.1 Static packet filter firewalls Static packet filter firewalls control traffic by examining the packet header information passing between service ports.2. For example. support network address translation. typically). They support TCP protocol only (no UDP). such as ftp/http/telnet. The security level is the lowest and is not considered secure.net. are very important companions for other types of firewalls. This type of firewall validates that a packet is either a connection request or a data packet belonging to a connection or a virtual circuit between two peer transport layers.3. AIX 4. Static packet filter firewalls are the fastest of the four types. This type of firewall inspects packets at the network layer and is not capable of processing state information in the application-layer protocols. Routers. a properly-configured router is essential to the overall security of the network. the firewall inspects the packets to determine if the Chapter 2. and static packet filtering is also native to many routers. 2. Routers with well-designed and maintained filter sets go a long way towards fending off hackers because these filters provide the first line of defense in many internet attacks (denial of service. network mapping).2 Circuit level firewalls Circuit level firewalls operate at the transport layer.x provides static packet filtering through the IPSec facility ( bos.2. The firewall forms a type of state table to monitor the handshake of each new connection. in particular. After the handshakes are complete. and can be implemented in hardware.2.rte fileset). 2. Firewalls 15 . Although the router cannot by itself be the primary security enforcer. you have to configure the static packet filter firewall to allow traffic from all external users (Internet) to your Web server (port 80. if you have an Internet Web server set up for your business. They are stateless.ipsec. The level of filtering is simple and has no embedded logic to handle the more sophisticated attacks.
For example. 16 Additional Security Tools for AIX Systems . A proxy firewall sits transparently between an end-user and a service provider. They should not be used as the sole enforcer of security because of their limitations. new proxies have to be developed by the firewall vendors. if an attacker attempts to simulate a reply to a request from an internal host. A static packet filter firewall would not be able to detect that the reply was simulated and could potentially allow it to pass to the internal host and inflict its intended damage. They support network address translation and provide very good auditing and logging facilities.packets are to be allowed through or not. 2.4 Dynamic packet filter firewalls Dynamic packet filter firewalls provide additional protection for the UDP transport protocol by associating the UDP packets with a virtual connection table within the firewall. However. The dynamic packet filter firewall will know that the internal host did not initiate the request. for example. an FTP proxy can be used to restrict commands. 2. They also support network address translation. No direct connections are made between the internal clients and the external server. both sides are unaware of the proxy in the middle. Circuit level firewalls are generally faster than application layer firewalls because less computation is done on the packets. An FTP proxy is different from a HTTP proxy and so on. and when new protocols come out. based on a ruleset.2. for example. therefore. allowing get but disallowing put commands. and. it will fail. they form the first line of defense in good firewall design by preventing certain traffic from reaching your network. Each specific protocol requires its own specific proxy.3 Application layer (proxy) firewalls Application layer firewalls act as a proxy between internal and external users. The advantage of proxy firewalls is that the firewall has better control over what access to grant. Once allowed. Proxy firewalls are slow in comparison to the other types of firewalls. all network packets associated with this connection are allowed without further checks. when implemented on routers at the edge of your network. This connection table keeps track of the connection at both sides of the firewall. The disadvantage of proxy firewalls is that they are tied to specific protocols.5 Comparison between the different types Static packet filter firewalls are considered outdated and the least secure.2. 2. So.2. will not allow the simulated reply in.
Packet filtering checks individual IP packets.16. and proxies work on the level of connections and application byte streams. For more information on firewall evolution and types. such as the Internet and the company intranet. Good firewalls are hybrids.4 Figure 1.16. proxy. These designs are presented merely as a starting point for your design work. with characteristics of each of these types of firewalls incorporated into one product.30.3 Firewall designs Having covered firewall architecture.htm 2.3.16.cisco.30. we now turn our attention to firewall design. The basic firewall design is shown in Figure 1. visit: www. and dynamic packet filter firewalls have their strengths and weaknesses.com/univercd/cc/td/doc/product/iaabu/centri4/user/scf4ch3.1 Public Server 2 172.30. 2. Basic firewall design Firewall Router to ISP Different technologies can be used to control the traffic flow between the networks.1 Basic firewall design The most basic firewall system is one that separates two IP networks.30.3 Public Server 4 172. The configuration of the firewall specifies which connections are allowed and which are denied. All traffic between the two security zones must pass through the firewall system for it to be effective.16.Circuit level. Firewalls 17 . The complexity of your network and the nature of your business will influence and shape the decisions you make here. these techniques are often combined in a hybrid design that Chapter 2. Internal Network External Network Public Server 1 172.2 Public Server 3 172. In modern firewall products.
an attacker can gain full access to the Web server system. This zone. Secure because a firewall is protecting it.2 Firewalls with demilitarized zone (DMZ) More security can be gained by introducing a perimeter network within which public servers can be placed. The firewall cannot prevent the attacker from leveraging this to access other systems within one security zone (in other words. configuration errors. Servers that are to be visible from the Internet should be placed in the DMZ. Placing important servers outside the firewall in the external network is not recommended either. or any one of many other possible causes). It cannot prohibit unwanted connections within one security zone. This fact can lead to major security risks. since. It takes time for this information to reach public Internet sites and security mailing lists and even more time for software companies to develop and test patches to fix the vulnerabilities. such as Web servers. the internal network). Thus. 18 Additional Security Tools for AIX Systems . Every day. insecure dynamic content. 2. Experience shows that it is not realistic to expect complex server software.supports both techniques as discussed in Section 2. Knowledge is your best defense. to that end. to be free of security holes. and learning to think as the hackers do.3. It is important to keep in mind that a firewall is only able to check the traffic between the different attached networks. If the Web server contains security holes (due to software bugs. and. should be separated from the DMZ by another firewall. it is prudent to keep up to date with the latest information by reading security-related Web sites.3. new security holes are found and shared in the underground by hackers. "Firewall designs" on page 17. joining mailing lists. if the company's public Web server is placed within the internal network. is considered to be semi-secure. Major companies and government institutions have frequently been victims of these kinds of attacks. and not secure because it is accessible directly from the Internet. the firewall needs to be configured to allow HTTP connections to this system so that everyone can get to the Web pages. All other servers. then. the classic DMZ setup has two firewalls and a DMZ server network in-between as shown in Figure 2. including infrastructure support servers to the DMZ. For example. they cannot be protected by the firewall against attacks. known as the DMZ.
1 6 .1 6 .3 0 . that way. The obvious disadvantage of this setup is that you need two firewalls.3 0 . Further protection is still necessary for the public servers on the DMZ network.3 0 . Chapter 2.3 0 .1 In te rn a l S e rv e r 2 1 0 .D M Z N e tw o rk P u b lic S e rv e r 1 1 7 2 . The intruder that broke into Public Server 1 can now freely attack Public Server 2 because there is nothing between them.1 6 .3 0 . 2. when Public Server 1 is broken into.3 0 . especially if different technologies are used for the two firewalls. The intruder on Public Server 1 can easily monitor all network traffic (including company e-mail and other potentially sensitive information when collected systematically) that leaves both firewalls on the DMZ network side.3 0 . Analyzing who is talking to whom is called traffic analysis (even encrypted mail typically has plain text From: and To: mail addresses information that allows some insight into possibly confidential transactions). vulnerabilities in one firewall may not be used to breach the second firewall. No direct connection is allowed from the Internet to the internal servers. You may also want to consider using different firewall technologies on the two firewalls.4 E x te rn a l N e tw o rk E x te rn a l F ire w a ll R o u te r to IS P In te rn a l N e tw o rk In te rn a l F ire w a ll In te rn a l S e rv e r 1 1 0 .2 In te rn a l S e rv e r 3 1 0 . Firewall with DMZ The advantage of this setup is that the publicly-accessible servers are now protected from the external network and separated from the internal network.1 P u b lic S e rv e r 2 1 7 2 .3 Figure 2. and two firewalls must be compromised for attackers to gain access. more security is lost than necessary. Firewalls 19 .1 6 . This technique is known as network sniffing.1 6 .2 P u b lic S e rv e r 3 1 7 2 .1 6 .1 6 . In a worst case scenario. For example: 1.3 P u b lic S e rv e r 4 1 7 2 . which increases the complexity and the administrative overhead.
Experience shows that they are. Suppose Servers A. and suppose further that an attacker has compromised Server C. Switches are a good choice since they do not employ a shared medium. point-to-point. transmit account IDs and passwords in the clear across the network. they usually cannot properly filter even common protocols. account logins from one server to another are visible to all servers sharing that same medium. cumbersome. and are reusable. and ongoing maintenance provides additional challenges. properly administered. So. A third option is to use the IPSec facility under AIX 4. on a shared medium. B. Using the routing table. For example. The account information (ID and password) passed between Server A and Server B when a user establishes a telnet or ftp session is visible (through sniffing) to the attacker on Server C. which makes the kind of sniffing outlined in this scenario much more difficult. Another possibility is to use static packet filter routers with filters set to prevent certain traffic or certain routes. therefore.x to implement static packet filtering directly on the public servers. They can be a formidable partner to firewalls if properly configured and. A properly-configured switch will have a limited number of paths from the source to the destination. the medium is no longer shared but. With switches. not dependable as your only means of defense. such as telnet and ftp. and convenience as their primary objectives. rather. In addition to missing emphasis on security in development. and access to multiple destinations is controlled entirely within the switch. the people who set up the switches and routers and those who administer them are in different groups and have vastly different sets of skills. just as importantly. to summarize. switches. However. since active network devices. Switches and routers have even been known to contain hardwired backdoor passwords allowing easy reconfiguration by a knowledgeable attacker. switches and routers can be used to provide additional filtering and alarming but should never be relied on as a primary and dependable means of providing security to the business. Often. such as FTP. These passwords can be easily captured. speed. and C are all on the shared medium. you may also segregate subnets within the DMZ network. administrators have to maintain all sorts of 20 Additional Security Tools for AIX Systems . and routers are designed with performance.One common way of closing this vulnerability is to use manageable switches between the servers in the DMZ network. Security is somewhat of an afterthought. or even guessed.3. switches and routers are usually configured by sending plain text (not encrypted) passwords over the network. Also. due to very limited filtering capabilities. and error prone. configuring filter sets is somewhat counter-intuitive. Services. Typically. In addition.
which makes it very difficult. Firewalls 21 . Zwicky. More information on classic firewall designs can be found in: • Building Internet Firewalls. to be experts in and keep current with each. Compartments are a new name for security zones that are protected from each other by one firewall. looks similar to what is shown in Figure 3 on page 22. therefore. and may be considered state of the art. from each other. Chapter 2. ISBN 0-201-63357-4 2.equipment. by D. ISBN 1-5659-2124-0. two-firewall DMZ or Secure Server Network. and Deborah Russell • Firewalls and Internet Security: Repelling the Wily Hacker. We use it to differentiate this approach from the single. Brent Chapman. such as DMZs or security zones. The design that has emerged in recent years. if not impossible. from switches to routers to servers to PCs to whatever else their company has sitting on the network.3 Compartmentalized firewall environment design A more secure and flexible approach suitable for complex environments is the compartmentalized firewall environment in which a single firewall system is equipped with more than two network interfaces and which can.3. Elizabeth D. mutually protect several different compartments.
16. Careful planning of the compartments is required so that a partial security breach does not turn into a total security breach.30.30. One of the main functions of a firewall is to generate alarms when suspicious activity is detected (for example. If possible. A Web server breach should not entitle the attacker to go after your mail servers. DMZ Network 2. A properly-configured firewall should generate an alert if the intruder tries to leverage more access from the attacked system.2 DMZ Network 2 Public Server 4 172. The damage is restricted to the compartment where the compromised server is located.1 DMZ Network 1 Public Server 1 172.2 External Network Router to ISP Firewall Internal Network Figure 3. You should strive to keep the compartments homogeneous.3 22 Additional Security Tools for AIX Systems .30. for example. Since the compartments are independent. a security breach in one of the attached systems (for example.17. IP sniffing is almost useless to an attacker because they are able to see only the traffic within the one compartment they have broken into. Compartmentalized firewall The different compartments (External Network.1 Public Server 2 172.2 Internal Server 3 10.16. DMZ Network 1. each type should be in separate compartments.16.30. Internal Network) each have their own physical network connected to the firewall through dedicated network cards.Public Server 3 172. the Web server connecting to the mail server) because no security Internal Server 1 10. by having the Web server try to access the mail server.1 Internal Server 2 10.30.30.17.16. Public Server 1) does not lead to a total compromise of the environment. The firewall is now able to control all the traffic between these compartments.30.16.
quality. and only one has to be successful whereas the defender has to defend against an infinite number of possible attacks. Firewalls 23 . The compartmentalized approach entails somewhat higher complexity (more network cards in the firewall and more routing issues). The real problem in this setup (as well as all other firewall designs) is that if the firewall is broken into. The firewall system shown in Figure 3 on page 22 should perform network traffic control and nothing else. but it is disastrous when it occurs on the main firewall system. and audited for use in a firewall environment should be considered for use. In addition. and maintenance procedures should be well documented and always followed. Also. not firewalls. the number of TCP or UDP server programs on the firewall should Chapter 2. A security breach of this nature is very bad when it occurs on a server that is isolated in a compartment. Be aware that the attackers are always one step ahead since they have the ability to plan and launch many possible attacks. tested. The operating system should be hardened and always up-to-date. The firewall should serve the single-purpose of being a firewall. Either IP filtering or secure proxies or any combination of both can be used for that purpose. It should alert you when you are under attack and. A recent successful attack was launched while a firewall was down for maintenance activities. Proxies that are designed exclusively for firewall use can protect against certain rare network-level attacks because new IP packets are generated by the operating system instead of forwarding the original (and potentially harmful) IP packets. A single bug in the software usually enables the attacker to execute arbitrary commands and ultimately gain full control of the system. enable you to react. Obviously. Both have their own advantages.device will ever be able to protect you against all possible threats. Operating system insecurities due to low integrity. and that task is carried out by kernel modules designed exclusively for that task. and human error have been major factors in many security breaches. all security is lost. but the additional security is well worth the cost. it is a good idea to physically disconnect the firewall from the external network prior to starting any maintenance activities. it is extremely important to make the firewall as secure as possible. IP filtering makes it very difficult to break into the firewall system because only IP packets are processed. Only software that was explicitly designed. the defender can only hope to detect a successful attack early and initiate reconnaissance and countermeasures. incomplete hardening. Application software belongs on application servers. therefore. Plan ahead carefully before installing additional software on a firewall system. Therefore. Always keep the worst-case scenario in mind.
"Securing AIX" on page 139). The default option settings in firewalls are usually not sufficient to provide a secure environment. Many of the common attack methods are not covered by the default settings. firewall configuration should be viewed as an ongoing activity rather than just a one-time setup. you need to first secure the operating system (discussed in Chapter 8. To secure the firewall.icsa.be kept to an absolute minimum because these kinds of programs are usually the weak points taken advantage of by potential intruders. the battle is. Some firewalls have default ports on which they listen. Therefore. To identify a Check Point FireWall-1. Constant auditing and log monitoring is crucial for early detection of a potential (or real) security breach. generally.5 Firewalls on AIX Two common firewalls that run on IBM RS/6000 and the new IBM ^ pSeries hardware are Check Point FireWall-1 and IBM Secureway Firewall. to prevent easy detection. and additional configuration is typically required. you may want to add filter rules to your routers to prevent any external network traffic to those ports. so. Both products are hybrid firewalls that incorporate characteristics of both dynamic packet filter firewalls and application layer (proxy) firewalls. once it is compromised. and new attack methods are being invented almost daily. Check Point FireWall-1 is covered in Chapter 3. and. as such. Complicated rules may leave unanticipated holes in the rulebase. A firewall is a security enforcer and. "Check Point FireWall-1" on page 25. an attacker can use a port scanner to scan those ports to see if they are active. it must be very secure.shtml 24 Additional Security Tools for AIX Systems . then. It holds the keys to your kingdom. Check Point FireWall-1 listens on ports 256.net/html/communities/firewalls/certification/vendors/index. and 258 by default. 257. and IBM Secureway Firewall is covered in Chapter 4. lost. 2. A good source for comparing firewall products from different vendors is: www. 2.4 Securing firewalls Think of a firewall as an application. For example. "IBM Secureway Firewall" on page 47. Filter rules should be kept simple and short. secure the firewall software.
and answers to general questions is: www. The documentation is good. Traffic to and from the management console is encrypted. management. SecureRemote can be © Copyright IBM Corp. and logging. FireWall-1 integrates and centrally manages all aspects of network security.com/fw1 3. A central management console increases manageability by having a central location from which to implement security policies across multiple network entry points. It also has built-in support for LDAP directory services to centralize user management. FireWall-1 supports multiple authentication schemes. and there is additional support available on the Internet. both from Check Point and their business partners.Chapter 3. Diffie-Hellman. FireWall-1 password. Utilizing Check Point's patented Stateful Inspection Technology and Open Platform for Secure Enterprise Connectivity (OPSEC). The Check Point homepage can be found at: www. S/Key and digital certificates. including SecureID and RADIUS through internal or external authentication servers. FireWall-1 provides a central management console facility that enables you to administer a number of firewalls remotely. automation scripts. This makes the product intuitive to set up and use. Check Point FireWall-1 Check Point FireWall-1 is the industry leader for firewalls.phoneboy. a lot of other companies have integrated their products with FireWall-1. IPSec. 2000 25 . Other user authentication schemes include operating system password. Add-on software is also available to turn FireWall-1 into a total security solution. OPSEC is the binding platform that provides for this integration.checkpoint. There are a number of products that complement FireWall-1.com A good Web site for Check Point FireWall-1 troubleshooting information. and so on).1 FireWall-1 features The strength of FireWall-1 is its ease of use in terms of the user interface for configuration. With its position as market leader. 3DES. Encryption can be used for VPN with support for Internet standards (IKE. RSA. DES.
In FireWall-1 4. 3. • FTP Security Server protects FTP servers by controlling access to get and put commands. The Motif license needs to be installed on the management console. and 26 Additional Security Tools for AIX Systems . or unlimited). Licensing is based on the number of internal hosts to be protected (25.2 Complementary software for FireWall-1 Other products can be used with FireWall-1 to provide a total enterprise security solution.1.used to provide IPSec compliant encryption and key management to extend VPN to remote users. 250.may be subject to US export regulations based on key strength • Firewall engine (no management console. built-in server load balancing (five different algorithms) may be used to transparently load balance servers behind the firewall. • SMTP Security Server protects Mail servers by removing certain sendmail header fields. 50. For performance. Check Point FireWall-1 is available in several different configurations: • Basic firewall (includes management module and firewall module) • Firewall with VPN support (includes VPN for multiple site setup) • Firewall with VPN and DES encryption . There are three security servers in FireWall-1 that provide for content security: • HTTP Security Server protects Web servers against malicious Java and ActiveX applications as well as undesirable URLs. Bandwitdth management (Floodgate).1 product. Ensure that the correct license package is obtained. and it should be ordered with the FireWall 4. In FireWall-1 4. requires a separate management console) Check Point FireWall-1 requires licenses to be installed for it to work properly. FireWall-1 also has network address translation (NAT) using many-to-one and one-to-one configurations. compression. A license is also required to use the Motif GUI to connect to the FireWall-1 management console.0 and earlier. This license is not required with the Windows GUI. this license is free and can be requested off the Web. you will need to pay extra for it. and it should be tied to the management console's hostname or IP address as appropriate.
which is increasingly important in today's Web environment.com/support/technical/documents/index. such as Stonebeat. you will need to do this yourself. as such. For high availability. but the password is provided to both customers and resellers. Check Point FireWall-1 on AIX. is tailored to this firewall. and your security is only as strong as its weakest link. Check Point FireWall-1 27 .html). may also be used with FireWall-1 or IBM Secureway Firewall. However. we do cover additional procedures for tightening Check Point FireWall-1 security. the strength of Stonebeat is that it was created specifically with FireWall-1 in mind.hardware-based VPN-based acceleration are used to provide better performance. With firewalls being a crucial component of the network. "Securing AIX" on page 139. we cover: • Closing vulnerabilities during system start up • Managing FireWall-1 logs • Securing FireWall-1 default configurations • Creating a useful rulebase • Viewing connections • Enabling other defense mechanisms Chapter 3. Additional information can be found in the redbook. This site is password protected. Stonebeat increases the availability of the server by having a standby machine automatically take over for the primary firewall after a system or network interface failure.3 Securing FireWall-1 Check Point FireWall-1 installation does not include operating system hardening.checkpoint. In this book. For more information on operating system hardening. refer to Chapter 8. This product is built on top of FireWall-1 and. A Cookbook for Stand-Alone and High Availability. It is easily installed and configured and provides full functionality for the firewall. Other generic high availability software. products. SG24-5492. so. such as HACMP. can be used for automating failover. That subject is well covered on the Check Point Web site (www. 3. However. This is an important step because the firewall software sits on top of the operating system. Specifically. we do not cover how to install and initially configure Check Point FireWall-1.
as already mentioned. So. the default value of IP forwarding is 0 (disabled). you will need to reenable portmapper because Motif relies on the portmap service for port allocations. such as /etc/rc. as a side note.tcpip during system start up. disable IP forwarding ( no -o ipforwarding=0) on the firewall during this period to prevent any connections from going through. It occurs at the point in AIX start up when the network is available and the firewall policies have not yet been loaded. if you plan to use the Motif GUI. During the normal operation of a firewall. executed out of /etc/inittab. the portmap service is started by /etc/rc. In other words.3. Once the firewall policies have loaded.net. During this short time.net or any of the other start up files. should the AIX server act as a gateway.tcpip or /etc/rc. and make certain that ipforwarding has not been changed from its default of 0 (disabled) in /etc/rc. To protect your network. IP forwarding must be allowed since it is a gateway. attackers can attack the network by routing their packets through the firewall since no security policy is loaded. IP forwarding (ipforwarding) is an AIX network option (no) that specifies whether or not packets will be forwarded from one network interface to another. such as the following. You may have already disabled portmapper as part of your operating system hardening. After the firewall policies have loaded. However. #/bin/ksh LOG=/tmp/log/console FWDIR=/usr/lpp/FireWall-1/ export FWDIR /usr/lpp/FireWall-1/bin/fwstart > $LOG 2>&1 /usr/sbin/no -o ipforwarding=1 echo "Enabling IP forwarding" >> $LOG 2>&1 /usr/sbin/no -a | grep ipforwarding >> $LOG 2>&1 exit 0 Also.1 Closing vulnerabilities during system startup There is a period of time during AIX start up where the network protected by the firewall is vulnerable. you need to turn IP forwarding off during the vulnerable period and on during normal operation. At system start up. 28 Additional Security Tools for AIX Systems . IP forwarding can be enabled again.3. you can have a script. Be sure to comment out the start up of FireWall-1 in /etc/rc. For example.local. turn it on by changing it to 1 (enabled).
you disable the default ICMP option. They are found in the Properties Setup menu (from the main menu bar. To turn on functionality. If. you may want to further tighten security by removing the defaults and creating rules especially for the things you really need. which should be run periodically to ensure that the logs do not grow too large. it does not enable logging for that option. You then create a new rule (with logging turned on) for this in which you specify the trusted hosts that are allowed to ping the firewall. In general. Therefore. Check Point FireWall-1 29 .3 Securing FireWall-1 default configurations The FireWall-1 default options make it quick and easy to install and use the product. This separate filesystem prevents the /usr filesystem from filling up because of firewall logging activity. This is necessary if you want the firewall to track UDP Chapter 3. All other hosts are forbidden.m. it is a good idea to create a separate filesystem for the logging directory. you can ping the firewall from anywhere. and then select Properties). you do not want to allow that.2 Managing FireWall-1 logs When setting up FireWall-1. This flexibility gives you a high granularity of control over the security level on the firewal. you can either enable the option in the Properties Setup menu or create a rule for it. In most cases. Upon installation. For example. FireWall-1 provides a log switching option (fw logswitch). if you enable an option from the menu. better control is achieved through the latter. However.3. you create a rule for it. For example. by default.3. click Policy.. so.3. the following entry can be added to root's crontab: 0 2 * * * /usr/lpp/FireWall-1/bin/fw logswitch > /dev/null 2>&1 3. We recommend that you enable the following two options only: Accepting UDP Replies The Accepting UDP Replies option enables replies for two-way UDP communications. independent of rulebase. it will give you the option to turn on logging. to switch logs daily at 2:00 a. the level of verbosity you have configured for the firewall logging activity. Log file maintenance is best controlled through crontab. and the logging facility gives you an audit trail for each of the rules. The size of this filesystem depends on the amount of traffic that goes through the firewall. there are a number of services that are allowed by default. rather than the former. and it eases the management of the log directory. such as $FWDIR/log or /usr/lpp/FireWall-1/log. and the amount of historical logging data you want to keep. instead.
The other option is to create separate rules for UDP replies. However. you may disable this option. Figure 4. Having Check Point track the state of UDP communications is a good idea. this option needs to be enabled (or 30 Additional Security Tools for AIX Systems .communications. If the management console and the firewall daemons are on the same machine. if they are on separate machines. The assumption here is that all packets that come from the firewall are trusted. Security Policy tab in Properties Setup We recommend that you disable the remaining options for better security: Accept FireWall-1 Control Connections The Accept FireWall-1 Control Connections option needs to be enabled if you do remote firewall management. but this does not provide the advantage of state. It adds state to an otherwise stateless connection. Figure 4 shows the Properties Setup menu with the Accepting UDP Replies and Accepting Outgoing Packets options turned on. Accepting Outgoing Packets The Accepting Outgoing Packets option is used to enable outgoing packets initiated from the firewall or routed from the firewall to leave the firewall.
Some other types.phoneboy. (Refer to the www. A rule gives you better control and lets you turn on logging. refer to the redbook. The other commonly used dynamic routing protocol is OSPF (Open Shortest Path First).equivalent rules need to be created in the rulebase). and redirect (5). This option should be disabled unless you are using encryption.com/fw1 FAQ for more information on stateful inspection). may be dangerous and not necessary when initiated from the Internet. and 258. destination unreachable (3). Chapter 3. Accept Domain Name Download (TCP) The Accept Domain Name Download (TCP) option pertains to DNS nameserver zone transfers. you have to turn this option on. Check Point FireWall-1 31 . GG24-3376. There are various ICMP types. you should create a separate rule for it. you should create individual rules for the DNS servers that need to do zone transfers. such as timestamp request (13). such as ping and traceroute). 257. For more information about the ICMP types. Enable Decryption on Accept The Enable Decryption on Accept option will decrypt incoming encrypted packets even if there is no encryption rule. Dynamic routing has its insecurities and should be disabled unless you are certain it is properly configured. TCP/IP Tutorial and Technical Overview. address mask request (17). such as echo request (8). Accept RIP RIP (Routing Information Protocol) is the protocol used by the routed daemon for dynamic routing. If you want to take advantage of stateful inspection on ICMP. The Accept RIP option should be enabled only if you are using RIP (not OSPF). Rather than enabling this option. Accept ICMP The Accept ICMP option is used to enable or disable ICMP protocol (things. Accept Domain Name Queries (UDP) The Accept Domain Name Queries (UDP) option is used to enable or disable DNS queries. Disabling this feature disables access to ports 256. Rather than enable this globally. and time exceeded (11). and you should allow only the types you need. echo reply (0).
Enable FTP PASV Connections. you need to enable the Enable FTP PORT Data Connections option. It should be disabled if you are not allowing rsh and rexec protocol (see Chapter 8. "Securing AIX" on page 139. Enable RSH/REXEC Reverse stderr Connections The Enable RSH/REXEC Reverse stderr Connections option is used to allow rsh and rexec protocols to open a reverse connection for errors. See ****section X**** on passive FTP to decide if you need this. 32 Additional Security Tools for AIX Systems . To enable commands.Additional options that need to be configured are under the Services tab of the Properties Setup menu. you need to enable this option if you want to allow FTP. We recommend that you disable all four options: Enable FTP PORT Data Connections The FTP protocol uses two connections. RPC should not be allowed when facing the Internet as it has many security problems (see Chapter 8. A large number of FTP servers on the Internet require passive connection. for information about OS hardening). for information about OS hardening) Enable RPC Control The Enable RPC Control option is used for RPC dynamic port allocation and should be disabled unless required. so. and Enable RPC Control options turned off. one for control (port 21) and one for data (port 20). and so on. get. such as ls. put. to run on the data port (20). Enable FTP PASV Connections The Enable FTP PASV Connections option is used for passive FTP. "Securing AIX" on page 139. Enable RSH/REXEC Reverse stderr Connections. it only enables control port (21) access. Figure 5 on page 33 shows the Services tab of the Properties Setup menu with the Enable FTP PORT Data Connections. When you enable the FTP services in the rulebase.
Services tab in Properties Setup Lastly. By default. we recommend that you select Alert as an early warning mechanism for potential attacks. so. Figure 6 on page 34 shows the Log and Alert tab of the Properties Setup menu with the IP Options Drop Track set to Alert. Chapter 3.Figure 5. Check Point FireWall-1 33 . Set the IP Options Drop Track option to either Alert or Log. there is an option under the Log and Alert tab of the Properties Setup menu that needs to be configured. FireWall-1 drops IP packets with IP options. These packets are frequently used by attackers.
We explain them in order of importance: • Rule 9: The first rule you should set up is actually the last rule in the ruleset and is considered the cleanup rule. 34 Additional Security Tools for AIX Systems . processed sequentially from top to bottom. essentially.3.4 Creating a useful rulebase Our example rulebase (shown in Figure 7 on page 36) is for a rather simple setup and is only meant to illustrate some principles. Log and Alert tab in Properties Setup 3. Check Point FireWall-1 has an implicit drop rule that. This logging serves as an important early warning device in that it can alert you to a potential attacker snooping around your network. The difference between the cleanup rule and the implicit drop rule is that with the cleanup rule. does the same thing as the cleanup rule.Figure 6. There are nine rules. It is used to drop all packets which have not been accepted by any of the other rules. in our rulebase. you can log all traffic that is dropped.
• Rule 5: This is considered the stealth rule because it drops all connections that have the firewall as the destination. This rule prevents attackers from connecting to the firewall or even pinging the firewall. Notice that you should log this rule as well as drop the packets, but do not select reject because it will send an RST back to the originator. • Rule 4: Set up this rule to prevent excessive logging. NetBIOS (NBT) consists of nbname, nbsession, and nbdatagram service traffic, which may be dropped (and not logged) since it is voluminous and does not pose a security risk. • Rule 1: Add this rule to allow an admin client to remotely connect to the firewall for administrative purposes. That client can also ping the firewall and vice versa for network debugging purposes. You may remove echo-reply service and just allow echo-request service if you only want the client to ping the firewall and not the other way around. Alternatively, you can enable the Accept ICMP option as discussed (this is not recommended). • Rules 6,7, and 8: These rules are for Web and mail servers. You will need to modify them for your specific environment. For compartmentalized firewalls that have connections to the internal network as well as the DMZ and the Internet, you should include rules to prevent traffic from the DMZ or the Internet from reaching the internal network. All such attempts should be logged because they may be an indication of attempted spoofing. Remember also that the DMZ is considered semi-secure and should not be trusted completely. Only applications that need to connect to internal servers should have such connectivity allowed in the rulebase. • Rule 2: Set up this rule if the firewall is also a DNS server that serves the Internet. Some exploits have been known to use the UDP port 53 (DNS port). Therefore, enable it only if it is absolutely required. If the DNS server serves only internal users, you should change the Source to DMZ or Internal, or, better yet, move the DNS server off of the firewall. Notice that this rule must come before the stealth rule. • Rule 3: Only set this rule up if you have a secondary DNS server that needs to do zone transfers. Figure 7 on page 36 shows a useful rulebase.
Chapter 3. Check Point FireWall-1
Figure 7. Useful rulebase
Options chosen in the Properties Setup menu are already part of the rulebase. To view the complete list of rules, including those from the Properties Setup menu, click View, and then select Pseudo-rules. As shown in Figure 7, pseudo-rules have no numbers and appear in yellow.
3.3.5 Viewing connections
To view the current connection table, you can use the FireWall-1 command:
#fw tab -t connections -u
There is a PERL script available from www.enteract.com/~lspitz/fwtable.txt that lists the current connection table in a much more usable format:
Additional Security Tools for AIX Systems
# perl ./fwtable.pl ---- FW-1 CONNECTIONS TABLE ---
Src_IP 18.104.22.168 188.8.131.52 126.96.36.199 184.108.40.206 184.108.40.206
Src_Prt Dst_IP 32782 32780 846 784 1971 220.127.116.11 188.8.131.52 220.127.116.11 126.96.36.199 18.104.22.168
Dst_Prt IP_prot Kbuf Type 53 23 755 755 23 6 6 6 6 6 0 0 0 0 0 16385 16385 16385 16385 16385
Flags ffff0400 ffff0600 ffff0600 ffff0600 ffffff00
Timeout 3176/3600 2440/3600 3433/3600 3484/3600 3600/3600
3.3.6 Enabling other defense mechanisms
There are a number of ways to make Check Point FireWall-1 more secure. We recommend that you enable SYNDefender and IP spoofing protection, but do not use Fast Mode TCP. We also recommend that you consider implementing Intrusion Detection. Each of these is described in the following sections.
220.127.116.11 SYNDefender The SYN attack falls under the category of denial of service attack . Before going into the details of the SYN attack, we need to cover how a typical TCP connection is established as follows:
1. A client attempting to connect to a server sends a SYN packet (TCP packet with the SYN bit set) to the server. 2. The server replies with a SYN/ACK packet. 3. The client receives the SYN/ACK packet from the server and sends an ACK packet back. This is known as a 3-way handshake, and, upon successful completion, the connection is considered established. (Note that with stateful inspection, the firewall will monitor this handshake process as an active onlooker.) Here is how the SYN attack works: 1. The attacker uses a forged and non-reachable IP address and sends several SYN packets to the server. 2. The server responds with the appropriate SYN/ACK packets, but, since the sender's IP is a non-reachable address, the 3-way handshake cannot complete. 3. The connections remain pending and will not be cleared for the duration of the TCP timeout (unless the clear_partial_conns network option is set at
Chapter 3. Check Point FireWall-1
the OS level), which effectively prevents legitimate clients from connecting to the server on that service port. The key to the SYN attack is that the source IP must not be reachable. If it is, the server sending the SYN/ACK will get an RST packet in return. This is because the legitimate client (whose IP address has been stolen) will detect that the SYN/ACK packet is not in response to a SYN packet that it had sent, and will reply with an RST packet to reset the server connection (which defeats the attack). For an in-depth description of the attack, go to www.fc.net/phrack/files/p48/p48-13.html. Check Point FireWall-1 has two built-in defenses against SYN attacks. They are the SYNDefender Gateway and the SYNDefender Passive Gateway. You can set them on the SYNDefender tab of the Properties Setup menu (see Figure 8 on page 39). For the following explanations, assume the server is behind the firewall, and the client is in front of it. SYNDefender Gateway Mode works as follows: 1. The client sends the SYN packet to the server. 2. The server sends the SYN/ACK packet back to the client. 3. FireWall-1 sends the ACK packet to the server on behalf of the client. 4. The client sends the ACK packet to the server, but it is absorbed by FireWall-1. 5. The connection between client and server is established. 6. If the client does not send the ACK packet (event 4) within the timeout period configured in FireWall-1 (Figure 8), the firewall sends an RST packet to the server to tear down the connection. This is the recommended method to protect against SYN attacks. SYNDefender Passive SYN Gateway works as follows: 1. The client sends the SYN packet to the server. 2. The server sends the SYN/ACK packet back to the client, but it is intercepted by FireWall-1. 3. FireWall-1 resends the SYN/ACK packet to client. 4. The client sends the ACK packet back to server. 5. The connection between the client and server is established. 6. If the client does not send the ACK packet (event 4) to the server within the timeout period configured in FireWall-1 (see Figure 8 on page 39), the firewall sends an RST packet to the server to close its pending connection.
Additional Security Tools for AIX Systems
During the timeout period, the pending connection table on the server still has this connection in it. In other words, from the server's point of view, the 3-way handshake has never completed. Figure 8 shows the SYNDefender tab in the Properties Setup screen.
Figure 8. SYNDefender tab in the Properties Setup screen
184.108.40.206 IP spoofing protection Anti-spoofing protects against forged packets that claim to have originated from an internal IP address (a spoofed IP packet). Anti-spoofing ensures that the packets are coming or going on the correct network interfaces. For example, packets with a source IP address from the internal network should be coming into the firewall from the network card on the internal interface. If packets carrying the source IP address from the internal network come into the firewall from the Internet, it is likely due to a spoofed packet from someone trying to attack your network.
You need to know which networks are reachable from which interface. You then need to associate each group of addresses with the appropriate network
Chapter 3. Check Point FireWall-1
(More information follows. 2. IP addresses that are not considered to be spoofed. Perform the following steps to set up IP spoofing protection in FireWall-1 (refer to Figure 9 on page 40): 1. From Valid Addresses. 3. The option you choose depends on whether or not you are using network address translation (NAT) at the firewall. Select an interface (in our case. select firewall. select This net. In other words. From Spoof tracking.interface.) Figure 9. depending on how your network is configured. 4. select Log or Alert . Select the Interfaces tab. 40 Additional Security Tools for AIX Systems . From Network Objects. the tr0 interface is the external interface). Setting up IP spoofing The Valid Addresses selection specifies which addresses are allowed to be on the chosen interface. as shown in Figure 9. 5. Others. or Specific.
1.12.0) and the public IP addresses 203.16. Chapter 3.2. For example.12. use the IP address for the internal network. The real IP address (configured on the network card on the server) and the NAT IP address (publicly known IP address) are listed in the figure. Figure 10 on page 42 illustrates a with NAT enabled for Web Server 1 (Public Server 1). and 203.30. Table 2.If you are not using NAT. Valid Addresses with NAT Interface External (facing Internet) Internal Valid addresses Others Specific In the case of NAT and an Internal Interface. use the following for your Valid Addresses selections as shown in Table 1. Check Point FireWall-1 41 .12. For the servers on the internal network. When using NAT. Web Server 2 (Public Server 2). Valid Addresses without NAT Interface External (facing Internet) Internal Valid addresses Others This net If you are using NAT. and Mail Server (Public Server 3). you have to specify a group of addresses for Specific. Table 1. use the following for your Valid Addresses selections as shown in Table 2. and the NAT IP addresses for the servers on that network. 203.12.12. the group for Specific consists of the internal network address (172.12.3.
then.16. the end servers will drop the packets anyway because they are out of sequence. This reduces the security awareness of the firewall and should not be used. We do not recommend that you do this.126.96.36.199 Figure 10.12. 42 Additional Security Tools for AIX Systems . from the main menu bar. The assumption is that if these packets are not part of an established TCP connection.12. the Fast Mode TCP option can be used. select TCP (as shown in Figure 11 on page 43).220.127.116.11 NAT IP 203. To check the Fast Mode setting.16.30.2 172.16. Illustrating IP spoofing with NAT 3. select Manage.1 Public Server 2 172.30.Internal Network External Network Public Server 1 172. Notice that Fast Mode only applies to the TCP protocol.16.2 Public Server 3 172.3. The firewall assumes that all such packets are part of an established TCP connection and does no further checks on them.30.16.2 203. Fast Mode works by allowing all non-SYN/NO-ACK packets through the firewall.6.1 172. SYN packets are still checked with the rulebase. under Services.12.4 Firewall Router to ISP Real IP Web Server 1 Web Server 2 Mail Server 172.1 203.16. but successful connections are not logged into the connections table (removing the stateful inspection).3 Public Server 4 172.30.30.3 Fast Mode TCP For faster throughput.
3.4 Intrusion detection on Check Point FireWall-1 There is a very good article on how to implement intrusion detection on Check Point FireWall-1 at www. and 258 are controlled from the Properties Setup menu with the Accept FireWall-1 Control Connections option discussed in Section 3. 257. We will not be discussing it further here.3.conf file). Chapter 3.conf file.3. The latter file applies only to the SAM and LEA services (described later). you can disable them (just as you would normal TCP/IP ports in the /etc/inetd.htm. Fast Mode TCP 3.com/~lspitz/intrusion.enteract. modify the appropriate entries in the $FWDIR/conf/fwauthd. "Securing FireWall-1 default configurations" on page 29.Figure 11.6. If there are ports that you are not using. Ports 256. Check Point FireWall-1 43 .4 List of ports that Check Point FireWall-1 uses Check Point FireWall-1 has a list of ports that it uses by default.conf file or in the $FWDIR/conf/fwopsec.3. To disable authentication related services.
Exchange of CA and DH keys in FWZ and SKIP encryption between two FireWall-1 Management Consoles. • TCP Port 900 is used by FireWall-1's HTTP Client Authentication mechanism. use: # netstat -af inet If you are not sure which application is bound to a particular port. • TCP Port 257 is used by a remote firewall module to send logs to a management console.phoneboy. • TCP Port 264 is used for Secure Client (SecuRemote) build 4100 and later to fetch network topology and encryption keys from a FireWall-1 Management Console. "List Open Files (lsof)" on page 103. • UDP Port 260 and UDP Port 161 are used for the SNMP daemon that Check Point FireWall-1 provides.) • TCP Port 256 is used for three important things: a." It is probably used by FireWall-1 to exchange public keys with other hosts. SecuRemote build 4005 and earlier uses this port to fetch the network topology and encryption keys from a FireWall-1 Management Console. (Note: This information is taken verbatim directly from the www. • TCP Port 259 is used for Client Authentication.C. • UDP Port 259 is used in FWZ encryption to manage the encrypted session (SecuRemote and FireWall-1 to FireWall-1 VPNs). c. according to the 4.com/fw1/ Web site. 44 Additional Security Tools for AIX Systems .5. The following is the list of ports that the firewall uses. b. is labeled "Check Point VPN-1 Public Key Transfer Protocol. try using the lsof tool instead (see Section 6. Among other things. you can then determine which ports to leave active and which ports to disable. the management console uses this port to push the policy to the remote firewall.1SP1 objects. From that information.To view all active ports on your system. this tool can tell you which applications are bound to which ports. When installing a policy. • TCP Port 258 is used by the fwpolicy remote GUI. • UDP Port 500 is used for ISAKMP key exchange between firewalls or between a firewall and a host running Secure Client. • TCP Port 265. for more information).
• TCP Ports above 1024 are generally any Security Servers that are active. • TCP Port 18183 is used for SAM (Suspicious Activity Monitoring. • TCP Port 18181 is used for CVP (Content Vectoring Protocol. for intrusion detection). Chapter 3. for anti-virus scanning). for WebSense and the like). The actual ports used by these servers will vary. • TCP Port 18184 is used for Log Export API (LEA). • TCP Port 18182 is used for UFP (URL Filtering Protocol. Check Point FireWall-1 45 .
46 Additional Security Tools for AIX Systems .
IBM Secureway Firewall comes with an embedded Web proxy server (via the enhanced version of Web Traffic Express). proxy. 2000 47 .com/security/ •http://www-4. The NSA tool alone provides reason enough for purchasing the IBM Secureway Firewall. and support for URL blocking. The proxy server includes added support for industry-standard reporting utitlities.4. VPNs enable you to create secure tunnels between remote locations across the Internet. NSA can be used to proactively scan any hosts on the network (including the firewall) for potential security vulnerabilities. "Network Security Auditor (NSA)" on page 49. This means that the full HTTP proxy functionality is within the firewall itself with no need for additional software. IBM Secureway Firewall includes Virtual Private Network (VPN) support based on the IPSec standards. Infoworld named it as their product of the year: www. IBM Secureway Firewall comes with a two-user license Security Dynamics ACE Server (SecurID Protected) that is used for secure authentication. IBM Secureway Firewall IBM Secureway Firewall has been protecting IBM for more than 10 years. It is an excellent tool for identifying potential problems before they become breaches.infoworld. © Copyright IBM Corp. Installation and configuration of NSA is covered in Section 4.1. A brief overview is given here.ibm. In 1999. and circuit-level and includes a built-in Web proxy server and a SOCKS server. IBM Secureway Firewall ships with a tool called Network Security Auditor (NSA).com/software/security/firewall/ 4.1 IBM Secureway Firewall features IBM Secureway Firewall is comprised of a suite of tools that can be used individually or in combination depending on your needs and environment. support for persistent Web sessions of HTTP 1. This reduces the need for expensive leased lines.com/supplements/99poy_win/99poy_s.Chapter 4. It is a hybrid of three firewall architectures: Filtering.html Online information about IBM Secureway Firewall can be found at: •http://www-3.ibm.
HTTP.Net. load-balancing.Net runs on Windows 95 or Windows NT and collects IBM Secureway Firewall log files. Since users connect through the firewall. and failover of the firewall(s). and FTP content security and management solution.com Another useful product is Telemate. The firewall periodically FTPs the logs to the Telemate.The firewall has built-in support for email and pager notifications keyed off of specific. Network address translation (NAT) support using many-to-one and one-to-one configurations is included as well.Net server sitting behind the firewall.mimesweeper.2 Complimentary software for IBM Secureway Firewall As with Check Point FireWall-1.com/software/network/dispatcher/ Another complimentary product is MIMEsweeper. It is transparent to users and provides logging for further analysis. MIMEsweeper examines application content and provides protection against malicious code and viruses. Non-important users and groups are removed. an SMTP. 4. SOCKS Version 5 (V5) support is included for both TCP and UDP applications. The firewall offers advanced email protection to help block unwanted email and prevent mail spoofing. which is used to translate large. abstract firewall log files into meaningful business reports. Telemate. network dispatcher can be used to enhance performance by transparently splitting the load across multiple firewalls. configurable events. More information can be found at: www-4. Real-time performance statistics and log monitoring are also provided. This feature enables administrators to be notified of suspicious activities and to take action in the early stages of an attack. and non-essential services are disabled to reduce potential vulnerabilities. Administration of multiple firewalls is simplified through a centralized administration facility. More information can be found at: www.ibm. More information can be found at: 48 Additional Security Tools for AIX Systems . IBM Secureway Network Dispatcher can be used for scalability. The installation of the firewall hardens the operating system automatically. IBM Secureway Firewall also has a list of products to complement it. You can easily customize the reports and distribute them through email or translate them into HTML for publication on the intranet.integralis.
To make sure that this automatic hardening is sufficient for your needs. "Securing AIX" on page 139 of this book. The NSA tool is essentially a port scanner. for the complete list of steps that IBM Secureway Firewall takes to harden itself. For more information on NSA.www. making it an easy tool to use.1 . A single nsa command provides the entire output. refer to Section 2.net 4.1 Installing NSA The required NSA fileset is nsaauditor. which requires OS hardening as a manual step.3 Firewall hardening The IBM Secureway Firewall installation procedure includes a section on hardening.ibm. IBM Secureway Firewall 49 . Also.2 comes with IBM Secureway Firewall Version 4.4 Network Security Auditor (NSA) NSA is an extremely good tool for auditing your servers (AIX and others) for potential security vulnerabilities in the services that are running.telemate.4. Chapter 8.base. This is in contrast to Check Point FireWall-1. The NSA version may vary. but it incorporates additional tests to look for vulnerabilities within the ports it scans. depending on the version of IBM Secureway Firewall that you purchase. A Secure Way to Protect Your Network: IBM SecureWay Firewall for AIX V4.1.2 of the redbook. SG24-5855. To install NSA: TYPE SELECT TYPE TYPE smitty installp Install and Update from ALL Available Software /dev/cd0 [ESC+4 or F4 to select the CD ROM drive] F4 or ESC+4 to list Chapter 4. The output from the NSA scan of your environment gives you insight into an attacker's perspective of your network. 4.com/software/security/firewall/about/ 4. NSA Version 2.1. The hardening is an automated procedure that happens during firewall installation. Review the results of the scan and plug the security holes proactively before an attacker strikes.3. thus. see: http://www-4. discusses in detail the manual procedures you can use to harden the operating system.
and is the type used in this book.1. The extent of the port scans and tests varies depending on which type you choose. The firewall type provides the most extensive scan. Ensure that you have the necessary authorization prior to running these scans.nsa file. Important Some companies have strict restrictions against doing such scanning. you may want to play it safe by ensuring that backups are done prior to scanning.1. A Secure Way to Protect Your Network: IBM SecureWay Firewall for AIX V4. as crashes may occur as a result of the scans.base Fileset Level State Description ---------------------------------------------------------------------------Path: /usr/lib/objrepos nsauditor. is also a good source of information about the NSA tool.2. medium . You will be unable to scan until you obtain valid licenses. use: # nsa report -d /tmp/<output_file> The report can also be output in HTML format for viewing with a Web browser. Once obtained. Details of each type are in the scannerdefs file and in Appendix A. fulltcp. baseline.base 2. 50 Additional Security Tools for AIX Systems . To scan a server. standard . use: # nsa scan -d /tmp/<output_file> --scantype=firewall <host_to_scan> To view the output of the scan. The redbook. and firewall . complete. SG24-5855.4. these licenses must be located in the password-proctected /etc/nsa/license. Also. The NSA documentation is located in the /usr/lpp/nsauditor/doc/ directory.base (F7 or ESC+7 to select the fileset) Enter three times to install Ensure that the fileset is properly installed as follows: # lppchk -v # lslpp -l nsauditor.2 Using NSA Various scan methods are defined in the file /etc/nsa/scannerdefs file.0 COMMITTED Network Security Auditor 4. The types of scan are default.SELECT PRESS find nsaauditor.
you can decide if you need those services. when someone installs a new application that adds new. It is better to turn on only those services that you are certain that you need. See Chapter 8. sometimes. Whatever the case. Chapter 4.4. a description of the potential security loopholes is given. The report can be divided into these categories: • Configuration settings • Potential vulnerabilities • Dangerous services • Information leaks For each of these categories. for example. Default installations will have some services enabled by default (for example SNMP). This is very helpful for administrators trying to fix these potential loopholes and minimize the security risks. ensure that they are at their most secure configuration and latest security patch level. For those services that you need. The problem is that. it is a good idea to audit your servers regularly to ensure that the security levels remain the same and to alert you if any changes are made. IBM Secureway Firewall 51 . "Securing AIX" on page 139. administrators are unaware of such services running on the server. and turn the rest off.3 Interpreting NSA output An NSA scan produces considerable output. The following screen contains a sample of an NSA scan that was run on the control workstation of an SP complex.4. active ports. With a list of services running. for more information.
2 o Other .2 Dangerous Servers and Services .2 o NFS server vulnerabilities . September 01.5 o Network File Sharing Configuration . 2000 17:24 o Name: sp5cw0 Operating System: UNIX IBM AIX 4.3 o Information About System Resources .Network Services Audit Report Network Services Audit Report Report Date: Friday.3 Audit Date: `Friday.6 o Dangerous Sun RPC servers .6 Security Audit Findings o Configuration Settings o Access Control Configuration o Network File Sharing Configuration o `/spdata/sys1/install/pssplpp' is shared to everyone via NFS.6 o Dangerous Network Servers .images' is shared to everyone via NFS. o [SMTP at port 25] EXPN command is enabled.9 Security Audit Breakdown Configuration Settings .4 Information Leaks .2 Dangerous Servers and Services . 2000 16:59' Auditor: `root@arthur' Security Audit Summary o o o o Configuration Settings .3 Potential Vulnerabilities .7 o Access Control Configuration . o `/spdata/sys1/install/aix433/lppsource' is shared to everyone via NFS.9 o Information About User Accounts . o `/usr/sys/inst. September 01. o [SMTP at port 25] VRFY command is enabled.6 Information Leaks . o [177/UDP] XDMCP server accepts all management requests.7 Potential Vulnerabilities . o SNMP at UDP port 161 read community string is `public'. 52 Additional Security Tools for AIX Systems .
o XDMCP is active on UDP port 177. o calendar (Sun RPC program 100068) is active on TCP port 784. o FTP is active on TCP port 21. o Dangerous Sun RPC servers o pcnfs (Sun RPC program 150001) is active on UDP port 32784. o nfsmountd (Sun RPC program 100005) is active on TCP port 32774. o portmapper (Sun RPC program 100000) is active on TCP port 111. o NFS (Sun RPC program 100003) is active on TCP port 2049. o TFTP server on port 69 serves file `. o Active Network Servers o SSH is active on TCP port 22. IBM Secureway Firewall 53 . o Information Leaks o Information About User Accounts o rusers (Sun RPC program 100002) is active on UDP port 32781. o SMTP is active on TCP port 25. o status (Sun RPC program 100024) is active on TCP port 746. o rstatd (Sun RPC program 100001) is active on UDP port 32780. o rshell is active on TCP port 514. o TFTP is active on UDP port 69. o [SMTP at port 25] VRFY command is enabled. o nfsmountd (Sun RPC program 100005) is active on UDP port 32795. o SNMP is active on UDP port 161. o unknown (Sun RPC program 200006) is active on TCP port 2049. o rexec is active on TCP port 512. o [SMTP at port 25] EXPN command is enabled. o ttdbserver (Sun RPC program 100083) is active on TCP port 32769. o rlogin is active on TCP port 513. o Information About System Resources o portmapper (Sun RPC program 100000) is active on UDP port 111. Chapter 4. o telnet is active on TCP port 23. o X is active on TCP port 6000. o aix4_rstatd (Sun RPC program 200001) is active on TCP port 755. o SNMP is active on UDP port 161. o rlogin is active on TCP port 513.'.o Dangerous Servers and Services o Dangerous Network Servers o TFTP is active on UDP port 69. o rstatd (Sun RPC program 100001) is active on UDP port 32780. o [32774/TCP] NFS mountd allows mount requests to come from arbitrary port. o nfsmountd (Sun RPC program 100005) is active on TCP port 32774. o rshell is active on TCP port 514. o nlockmgr (Sun RPC program 100021) is active on TCP port 32775. o Potential Vulnerabilities o NFS server vulnerabilities o [32795/UDP] NFS mountd allows mount requests to come from arbitrary port.
2049.3'. o Network Transport Information o IP Transport Information o Host responded to ICMP Echo Request. 54 Additional Security Tools for AIX Systems .3'. o unknown (Sun RPC program 300667) is active on TCP port 32770. o nlockmgr (Sun RPC program 100021) is active on UDP port 32818.1.1 Sun Jul 9 18:28:14 CDT 2000'. o XDMCP is active on UDP port 177. o aix4_rstatd (Sun RPC program 200001) is active on UDP port 755. o rlogin is active on TCP port 513. 32769-32770. o NFS (Sun RPC program 100003) is active on UDP port 2049. o FTP is active on TCP port 21. 6000. 25. o Shared File Systems o `/spdata/sys1/install/pssplpp' is shared to everyone via NFS. o rexec is active on TCP port 512. o spray (Sun RPC program 100012) is active on UDP port 32783. 784.3/8. o nfsmountd (Sun RPC program 100005) is active on UDP port 32795. 512-514. 109-111. o Available Network Services o Unauthenticated File Service o TFTP server on port 69 serves file `. o pcnfs (Sun RPC program 150001) is active on UDP port 32784. o portmapper (Sun RPC program 100000) is active on UDP port 111. 109-111.1'. o Port Scan Information o TCP Port Scan Data o The following TCP ports were scanned: 21-23. 746. 755. o status (Sun RPC program 100024) is active on UDP port 746. o telnet is active on TCP port 23. o User Login Services o SSH is active on TCP port 22. o SNMP at UDP port 161 read community string is `public'. o rshell is active on TCP port 514. o rwall (Sun RPC program 100008) is active on UDP port 32782. o rusers (Sun RPC program 100002) is active on UDP port 32781. o calendar (Sun RPC program 100068) is active on UDP port 32785. 139. 139.9. o [25/TCP] SMTP server version is `Sendmail AIX4. 746.o portmapper (Sun RPC program 100000) is active on TCP port 111. 143. o Operating system is `UNIX IBM AIX 4. 784. 37661. 143. o rstatd (Sun RPC program 100001) is active on UDP port 32780. Server OpenSSH_2. o `/spdata/sys1/install/aix433/lppsource' is shared to everyone via NFS. 2049. 512-514. 755. o autofs (Sun RPC program 100099) is active on UDP port 32839. o `/usr/sys/inst.99. 32774-32775. o [21/TCP] FTP server version is `4. o Server Version Strings o [22/TCP] SSH server version is `Protocol 1. 49690 o The following TCP ports were visible: 21-23. 25.images' is shared to everyone via NFS.'.
32769-32770. o Sun RPC program 300667 (unknown) is registered on TCP port 32770. 746. 32795. 137. 32839 o The following UDP ports were active: 69. 755. 2049. 32774-32775. 2049. 2049.6000. 746. 111. o Sun RPC program 100003 (NFS) is registered on TCP port 2049. 746. 161. o Sun RPC program 100083 (ttdbserver) is registered on TCP port 32769. o Sun RPC program 100000 (portmapper) is registered on UDP port 111. 161. 111. 111. 2049. 32818. 111. 49690 o The following TCP ports were active: 21-23. o Sun RPC program 100002 (rusers) is registered on UDP port 32781. o Sun RPC program 200006 (unknown) is registered on TCP port 2049. o Sun RPC program 1342177279 (unknown) is registered on TCP port 37661. 32839 o The following UDP ports did not respond: None o The servers on these UDP ports could not be identified: None o Sun RPC Registrations o Sun RPC program 100000 (portmapper) is registered on TCP port 111. o Sun RPC program 100021 (nlockmgr) is registered on TCP port 32775. 177. o Sun RPC program 200001 (aix4_rstatd) is registered on TCP port 755. 6000. 32795. 37661. 177. o Sun RPC program 100068 (calendar) is registered on TCP port 784. 32780-32785. 137. 32839 o The following UDP ports were visible: 69. o Sun RPC program 100001 (rstatd) is registered on UDP port 32780. 746. 755. 32818. o Sun RPC program 1342177280 (unknown) is registered on TCP port 49690. 32780-32785. 755. 32780-32785. 512-514. 32795. IBM Secureway Firewall 55 . 49690 o The servers on these TCP ports could not be identified: 49690 o The servers on these TCP ports terminated immediately: None o UDP Port Scan Data o The following UDP ports were scanned: 69. 784. 161. 25. 32769-32770. Chapter 4. o Sun RPC program 100024 (status) is registered on TCP port 746. 32818. 177. 32774-32775. o Sun RPC program 100008 (rwall) is registered on UDP port 32782. o Sun RPC program 100005 (nfsmount) is registered on TCP port 32774. 755.
0000\nTCP/IP Client Support version: 04.1.99-OpenSSH_2.0003. 1 Sep 2000 16:59:24 -0400 56 Additional Security Tools for AIX Systems .0 o Server Banners o [22/TCP] SSH server banner SSH-1. o SNMP/161 variable sysObjectID value is `1.ibm.1.msc.0 tot75 :0.03. o Sun RPC program 100005 (nfsmount) is registered on UDP port 32795. o Sun RPC program 200006 (unknown) is registered on UDP port 2049. Fri.3. o Sun RPC program 200001 (aix4_rstatd) is registered on UDP port 755.1. o Sun RPC program 150001 (pcnfs) is registered on UDP port 32784.0000'.3/8. o SNMP Variables Retrieved o SNMP/161 variable sysDescr value is `RISC System/6000 Architecture\nMachine Type: 0x0100 Processor id: 000509306700\nBase Operating System Runtime AIX version: 04.com ESMTP Sendmail AIX4.1.1 o [25/TCP] SMTP server banner 220 sp5en0.itso. o SNMP/161 variable sysName value is `sp5en0'. o Sun RPC program 100099 (autofs) is registered on UDP port 32839.o Sun RPC program 100012 (spray) is registered on UDP port 32783.0003. o Sun RPC program 100021 (nlockmgr) is registered on UDP port 32818.9. o Sun RPC program 100024 (status) is registered on UDP port 746.3'.3.03.0 :0.3. o Active Users o rusers/32781 shows the following users logged on: root root root root root root root root root root <<<<<<<<<<- tot75 :0.1. o Sun RPC program 100068 (calendar) is registered on UDP port 32785.6. o Sun RPC program 100003 (NFS) is registered on UDP port 2049.9.2.4.1.3/8.2.
login: o [21/TCP] FTP server banner 220 sp5en0 FTP server (Version 4. 1996.o [23/TCP] telnet server banner telnet (sp5en0) AIX Version 4 (C) Copyrights by IBM and by others 1982. Chapter 4. IBM Secureway Firewall 57 .1 Sun Jul 9 18:28:14 CDT 2000) ready.
58 Additional Security Tools for AIX Systems .
Over the years. These commands have various security vulnerabilities. when authentication is required. and data integrity are all required to ensure security and are discussed at length in this chapter. we discuss how to implement security measures for remote access. Only the requests from trusted hosts (as specified in the access control lists) are then allowed onto the protected services. passwords are bypassed entirely. rcp. and data integrity.1 Secure Shell (ssh) SSH is a client-server application that allows secure login or secure execution of commands on a remote computer. Instead. rsh. particularly in situations where access to the remote host is through the Internet. 2000 59 . passwords are not encrypted. However. All requests for the protected services pass through TCP Wrapper first and are checked against access control lists. The ssh daemon typically listens to port 22. security has become more of an issue. Secure shell (ssh) is a protocol that can be used to provide a secure channel between two hosts. introducing the need to implement secure remote access. TCP Wrapper is a tool that provides this protection. 5. It uses encryption and authentication while ensuring data integrity. TCP Wrapper can also be configured to log all connection attempts to the protected services. thus. For example.Chapter 5. Secure remote access In this chapter. encryption. That is because the more common © Copyright IBM Corp. SSH is intended to replace the traditional BSD "r" commands (rlogin. authentication. Remote access is typical in UNIX environments. in many cases. they are sent as clear-text across the wire. To ensure security. you need to: • Ensure that users are who they say they are • Protect the communication channel such that anyone sniffing the network will not be able to read the communication • Ensure that the information sent is not altered in transit SSH is a protocol that can achieve these requirements by providing strong authentication. Encryption. The goal is to provide assurance that the communication channels between two hosts remain private. and so on). Certain services under the control of the inetd daemon (such as ftp or telnet) should also be protected.
That connection is authenticated through a combination of the client's private key on the client and the client's public key on the server. In non-interactive mode.onsight. The public key of a client must be physically located on the server for the client to be able to open an SSH connection to the server. Any user with access to a host listed in one of these files on the remote host may automatically be granted access to that host. It supports either public-private key pairs or . Protection is accomplished by way of the private key. These will covered soon.com/faq/ssh/ssh-faq. Encryption channels ensure this protection.configuration is to have these commands authenticate based on hostname or IP address (contained in the . SSH supports two modes: Interactive. Worse still is the scenario where an attacker steals a legitimate IP address from a host listed in one of these files and configures an imposter host with the stolen IP address. SSH is used to establish a session on a remote server.equiv files). public key pair. and manipulation of data by intermediary hosts. SSH is used to execute a command on a remote server and return the results to the local client.) SSH also protects against password sniffing. In the case of the root user. The imposter host then has the same access to the target host as the host whose IP address was stolen. SSH provides the same functionality as the BSD "r" commands. (It goes without saying that private keys need to be rigorously protected and never sent across unencrypted network connections. listening X authentication data attacks. A fake host claiming to have the IP address or DNS name of the client will not be able to establish the SSH connection without also having access to the client's private key. The following Web site is an excellent source of information for SSH: www. and non-interactive. the consequences are disastrous. SSH also protects against DNS spoofing where the attacker forges DNS entries.html 60 Additional Security Tools for AIX Systems . but with added security. In the interactive mode.rhosts files for authentication and has various encryption and data integrity schemes.rhosts or /etc/hosts. SSH protects against IP spoofing (where a remote host commandeers the IP address of an internal trusted host). SSH is flexible in its setup.
1 Obtaining SSH There are two versions of SSH covered in this book: 1. SSH.fr.1. is available in installp format.Com" on page 76.Com differ slightly in their implementations.ssh. OpenSSH.com/ssh/download. "Difference between SSH1 and SSH2" on page 62. 2. couple it with a tool. The main site is ftp://ftp.Com is available from numerous sources. whereas the second.bull. such as Tripwire. Solaris.com/pub/ssh/. One very common insidious attack involves patching the SSH client executable such that it logs all account IDs and passwords used within the SSH sessions.1. in place.1. such as Tripwire. Compatibility between the two versions is covered in Section 5.html.8. The homepage for OpenSSH is http://www. requires that you have access to a C compiler. A full server version is also available for UNIX. and Van Dyke Software: • SSH from SSH Communication is available from http://www. Secure remote access 61 . A list of mirror sites can be found in http://www. especially in their configuration files. OpenSSH and SSH. Commercial versions can be obtained from SSH Communication Security. Chapter 5. which we will refer to as SSH.Com. F-Secure. We cover both versions in this book. SSH. The installp version is available from http://www-frec. The original version from SSH Communications Security. HP-UX. Linux.ssh. "SSH2 interoperability between OpenSSH and SSH.Important If you plan to use SSH as a key component in your security environment.Com. The commercial version includes clients for Windows. The version developed by the OpenBSD project (OpenSSH) The first.com.com/ssh. Without a tool. The UNIX versions include a limited server that allows up to two simultaneous connections. 5. and AIX. SSH. see Section 5. For more information on the differences between the two protocols. There are two different protocol versions of SSH: SSH1 and SSH2. it is very difficult to discover that this attack has occurred.ssh.2.openssh.Com and OpenSSH support both SSH1 and SSH2.
transmit these passwords in clear text across the network.) • It has built-in support for both SOCKS and secure file transfer protocol (sftp). SSH1 will continue to be important for some time. Because of this.1. This SSH client runs on Windows platforms and supports the SSH1 and SSH2 protocols.f-secure. • SecureCRT from Van Dyke Software is available at http://www. This means that they are easily picked up by anyone sniffing the network. has a much larger installed base. at present.vandyke. encryption. Also available is SecureFX. 62 Additional Security Tools for AIX Systems . It has been around much longer and. Also. The bulk of the new development effort is going into SSH2. performance. Windows. and portability than SSH1. .3 Key concepts of SSH SSH provides authentication.1 Authentication Authentication is the process of identifying an individual and ensuring that the person is who he or she claims to be. SSH2 is a complete rewrite of SSH1.rhosts). However. SSH1 has support for more platforms and more authentication schemes (Kerberos. passwords have a practical length limit of eight characters (characters after the eighth are ignored). Authentication is important because access rights are usually granted based on user ID. (SSH1 supports RSA. and rsh.2 Difference between SSH1 and SSH2 SSH1 and SSH2 are entirely different protocols. and Macintosh operating systems. Protocols. It runs on UNIX. 5.• F-Secure SSH is available at http://www. such as telnet. and data integrity. thus. thus. 5.com/products/securecrt/.1.3.1. An understanding of these concepts is key to an understanding of how SSH fits into a total security solution. The key differences with SSH2 are: • It has better security. Both client and server versions of SSH are available. in AIX. the most common means of authentication is through passwords.com/products/ssh/. • It supports DSA and other public key algorithms for encryption and authentication. and SSH1 and SSH2 protocols are supported. For all practical purposes. In AIX. ftp. 5. AFS. a file transfer product that does FTP tunneling over SSH2. the need to ensure that the person logging in with a specific user ID is indeed that person.
• User A then requests a log in on SSH Server B via SSH. A good passphrase is one that is 10-30 characters long. There are two types of cryptography algorithm: Symmetric and asymmetric. private-key pair. How do we distribute the keys safely from sender to recipient? This is the big limitation of symmetric key cryptography that resulted in the development of asymmetric key cryptography. This is the older of the two. you must have a public-key. • SSH Server B checks its set of public keys looking for the one belonging to User A (which it finds). This form of authentication is significantly harder to break than the more conventional methods. In asymmetric key cryptography. A more significant benefit is the use of public-key. SSH does support other authentication methods. private-key pairs to authenticate instead of the traditional UNIX user ID and password scheme. deriving the private key from the public key is an extremely difficult task that takes more resources than are commonly available. As has already been mentioned. you are given the opportunity to protect the private key with a passphrase.SSH improves security by encrypting any traffic used during authentication. To use SSH. Chapter 5. In symmetric key cryptography. you first need to be familiar with the types of cryptography. is almost impossible to guess and has a hidden meaning only for the person generating it. When the keys are generated. keys exists in pairs: Public and private. To understand public-key. the drawback is key management. • User A first copies their public key to SSH Server B. the harder this is to do. Passwords are not transferred in the clear. The advantage of this method is that it is very fast with both encryption and decryption of the data. Longer key lengths translate into better security. These two keys form a pair and are generated at the same time. A single program generates both keys. The private key remains on the local SSH client and must be kept safe. The public key must be copied to the SSH servers to which you want access. Although mathematically related. Here is an example of how this works: • User A wants to connect to SSH Server B via SSH. Notice that a passphrase can be much more secure than a standard UNIX password by virtue of its increased length. The longer the key length. Secure remote access 63 . However. the same key is used to encrypt and decrypt the data. private-key authentication.
5. 64 Additional Security Tools for AIX Systems . and DSA. DSA in SSH2) • Kerberos (SSH1 only) • Host-based (. The public-key method is the one that is most commonly used. Since the private key is protected by a passphrase. SSH2 uses DSA keys. a secure channel is established. This. Twofish. Thus.equiv in SSH1. Blowfish. only User A can use it. Depending on the version being used and how it is configured. These methods are used to provide the secure and encrypted channel to transfer data. Notice that conventional symmetric ciphers are used to encrypt communication channels. IDEA. does not mean that the encryption cannot be broken. With encryption. reducing the need for expensive dedicated lease lines. access is granted.rhosts or /etc/hosts. • If the challenge is successful. the data will not be decipherable.3. The ciphers or cryptographic algorithm used for encryption depend on the version of SSH that is running. Each of them has its own strengths and weaknesses. SSH can authenticate by the following methods: • Password (/etc/passwd or /etc/shadow in UNIX) • Public-key (RSA in SSH1. Strong encryption just means that it is impractical to do so because it takes too long or it takes more computational power than is commonly available. or Cast128.2 Encryption Encryption is the translation of data into a secret code that should not be decipherable to anyone other than the intended recipient. Refer to the documentation for your implementation to see if all are available.• SSH Server B challenges User A for the matching private key. however. which means it is very impracticable to decode encrypted data without the right key or passphrase. Arcfour. or Blowfish while SSH2 uses 3DES. and it is the only one that we cover in this book. SSH incorporates two different and incompatible cryptographic algorithms for authentication: RSA. and can be used even over the Internet to provide a virtual private network. SSH uses strong cryptography. SSH1 uses DES. even if someone is sniffing the network. 3DES.1. but they all serve the same functionality. public key in SSH2) The methods vary according to implementation. SSH1 uses RSA keys.
no news is good news.1.1 1.4 Installing OpenSSH on AIX We now show you how to install the freeware. To understand how SSH makes this determination. Secure remote access 65 .rte freeware. SSH is silent.8. and freeware. The sending machine calculates the hash on the input data and sends both the data and the hash to the receiving machine.rte freeware.1.egd.openssl.rte Version 2.egd. SSH warns you about it.4. The fileset versions we used during the production of this book are shown in Table 3.zlib. Any change to the input will result in a totally different output (though the length will still be the same).rte.zlib. If the data has not been tampered with. If the data is clean. It is available for download in installp format from http://www-frec. freeware. See Section 7. It has the following prerequisite filesets: freeware.1.openssh. for more information on how to do this.0 0.0. This version of SSH supports both SSH1 and SSH2. SSH does not protect against data tampering as such.1. A hash function takes an input of any length and calculates a fixed length output (where the length depends on the specific hashing algorithm).2 Once you have downloaded the software distribution.rte version of SSH.4 0. ensure that is has not been tampered with. 5. The receiving machine recalculates the hash on the data and compares it to the received hash. Chapter 5.5.3.rte freeware. an understanding of hashing functions is necessary. If they are not.1.rte. either intentionally or by accident. Hashing functions are mathematical in nature. In the case of SSH. both hashes will be identical. Table 3. "Ensuring the integrity of downloads" on page 136.3.5.openssl.openssh.rte.bull.1.3 Data integrity Data integrity helps give assurance that the received data matches the send data and has not been tampered with. instead it just merely informs you of when such activity has taken place.fr. Freeware OpenSSH filesets Fileset freeware.9.
Without this file. by Info-ZIP (firstname.lastname@example.com. inflating: egd-0. freeware.0.0 USR COMMITT SUCCESS You now need to create and load the local socket file. egd-0.bff file: # chmod u+x .1. and will need to be done manually afterwards.wku. Run the following command to create the /dev/entropy local socket file: #/usr/bin/perl -w /usr/opt/perl5/bin/egd.0. which must be present for the remaining installation of SSH to work properly.egd.egd.8.exe to obtain the installp-format. This file must be in place prior to running the remainder of the OpenSSH installation so that the installation process can create all of the necessary DSA keys automatically.4.exe # .egd.1. The following installp command will apply.pl /dev/entropy 66 Additional Security Tools for AIX Systems .exe UnZipSFX 5.exe zlib-1_1_3_2.edu).0. and automatically install prerequisite filesets: #installp -acgX -d . that creation process will fail with a " Couldn't connect to EGD socket "/dev/entropy": Connection refused" message.rte Installation Summary -------------------Name Level Part Event Result ------------------------------------------------------------------------------freeware./egd-0_8_0_0. commit.9.#ls -l total 7152 -rwx------rwx------rwx------rwx------ 1 1 1 1 root root root root system system system system 104740 532553 2878322 137279 Aug Aug Aug Aug 18 18 18 18 17:40 17:40 17:40 17:40 egd-0_8_0_0.rte 0.8.0. /dev/entropy.exe openssl-0.rte fileset first because it creates the local socket./egd-0_8_0_0.exe You will need to install the freeware. Inflate egd-0_8_0_0.0.bff # Install the fileset either through SMIT or at the command line.exe openssh-2.8.32 of 3 November 1997.
9.5.2. "Ensuring the integrity of downloads" on page 136.bff filesets.2.bff.rte 1. # installp -acgX -d . freeware.zlib.exe openssl-0.5.asc are the PGP signatures as will be discussed in Section 7. openssl-0.exe openssh-2.5.1. Inflate the other three filesets.1.bff openssl-0.openssl.rte 2. and zlib-1.4 ROOT APPLY SUCCESS Verify that all of the filesets are properly installed: Chapter 5.8.5.rte 2.1.bff openssh-2.4.2. You need to have the openssh-2.1.1.rte 0.1.3.rte 0.openssh.bff.1.3.rte and freeware.1.4.openssl.1.openssl.exe Use the following installp command to install the freeware.egd.9. #rm .3.1.1.bff.bff egd-0_8_0_0.4.asc zlib-1_1_3_2.1.toc #ls -l total 29192 -rwxr--r--rwx------rw-r--r--rw-r--r--rwx------rw-r--r--rw-r--r--rwx------rw-r--r--rw-r--r--rwx------ 1 1 1 1 1 1 1 1 1 1 1 root root root root root root root root root root root system system system system system system system system system system system 153600 104740 1433600 2599 532553 9420800 2599 2878322 256000 2571 137279 Jul Aug Aug Aug Aug Jul Aug Aug Mar Mar Aug 06 18 03 03 18 28 01 18 20 20 18 03:39 17:40 07:51 07:58 17:40 10:39 04:26 17:40 12:13 12:14 17:40 egd-0.1.9.openssh.tcpip by the installation of the freeware.bff.0.zlib.4.1 ROOT APPLY SUCCESS freeware.1.3.1.rte fileset.4 USR APPLY SUCCESS freeware.openssh.1.rte filesets automatically (because of the -g flag).1.1.asc openssh-2.9.1 USR APPLY SUCCESS freeware.openssh.5.1. This will also install the freeware.1.bff. The files with extensions .1. and verify that the files are properly inflated.9.exe zlib-1. Secure remote access 67 .4.Note This command was also added to /etc/rc.5.rte Installation Summary -------------------Name Level Part Event Result ------------------------------------------------------------------------------freeware.2 USR APPLY SUCCESS freeware.rte fileset.bff zlib-1.asc openssl-0.9.0.
To check.1. which is available in the SSH2 version of SSH from SSH Communications Security..equiv/.shosts) file on the remote machine.openssh.equiv) file or the . but it has the added security of ssh. OpenSSH comes with the scp tool. The first is based on the /etc/hosts... The set up for this method is the same as that for the first.equiv/shosts.. the OpenSSH installation sets the SSH daemon to SSH1.shosts files.rhosts/. the current version of OpenSSH does not ship with the sftp tool. By default. The second method is based on the first method combined with RSA-based host authentication.equiv (or /etc/shosts. # After installation.tcpip to automatically start the SSH daemon on system startup. This method carries the inherent security weaknesses of the traditional BSD rsh and rlogin commands (such as clear-text passwords) and should be disabled. Unfortunately. you may want to include environment variables MANPATH=/usr/local/man and PATH=/usr/local/bin into /etc/profile to simplify access to the man pages and tools. run: #lslpp -f freeware.openssh. this authentication method is disabled in the /etc/openssh/sshd_config file (RhostsAuthentication no). # lslpp -l | grep freeware.equiv/shosts. the server verifies the client's host key in /etc/ssh/known_hosts and $HOME/. 68 Additional Security Tools for AIX Systems .shosts files. and an entry is added to /etc/rc.rhosts (or . The SSH server prompts you whenever a new connection is added or modified. It is functionally similar to rcp.rte | grep sftp 5. 2. It can also be used as a replacement for ftp.equiv/. This method also has security weaknesses since it still requires the use of hosts.rte . The known_hosts file is updated automatically by the SSH server.# lppchk -v . This tool may be added in future versions of OpenSSH. this authentication method is enabled in the /etc/openssh/sshd_config file (RhostsRSAAuthentication yes). When a user connects to the OpenSS1 server.5 OpenSSH using SSH1 By default. In addition to ssh. By default.rhosts/. there are four supported methods of authentication: 1. This means that on top of the hosts.ssh/known_hosts files.
When you generate a key-pair.ssh/identity. Notice that the SSH version is 1.ssh/authorized_keys file on the SSH server contains copies of the public keys for the remote clients that are allowed to log in under that account. The difference is that this authentication method uses encryption for the exchanges. To manually start the SSH daemon (using /etc/openssh/sshd_config as the config file and /etc/openssh/ssh_host_key as the RSA host key file): #/usr/local/bin/opensshd -f /etc/openssh/sshd_config -h /etc/openssh/ssh_host_key To manually stop the SSH daemon: #kill `cat /var/openssh/sshd. this authentication method is enabled in the /etc/openssh/sshd_config file (RSAAuthentication yes ). Connected to 0.pub file.ssh/identity file. and the private key is stored in the $HOME/. To find out which version of SSH (SSH1 or SSH2) you are running.99.pid` Chapter 5. 4. the public key is stored in the $HOME/.. telnet to localhost (0) on sshd port (22). By default.1. This is the method we recommend and the one we cover in detail in this book. Escape character is '^T'. Secure remote access 69 .pid` To refresh the daemon: #kill -1 `cat /var/openssh/sshd. This method is used when all other authentication methods fail. ftp. rsh. the SSH daemon listens on port 22. so passwords are not sent in clear text as they are with standard protocols.99-OpenSSH_2. # tn 0 22 Trying.1 The SSH installation adds /etc/rc. storing it in your $HOME/. SSH-1. Configuring and using SSH1 By default. You then copy the public key to the SSH server.. The $HOME/. The fourth method is based on RSA authentication.ssh/ directory under the new name of authorized_keys. and rlogin. The third method is based on user passwords as per normal telnet logins.3.openssh to /etc/inittab so that the SSH daemon will automatically start during system startup. such as telnet.
.... and per-user options are specified in the $HOME/..pub) to the SSH server. (You may first want to rename the public key to identify the user and host from which the key was generated.ssh/identity file.equiv is not recommended. To generate a public-key.. The use of $HOME/....... During the creation process. but you will also need to add an IdentifyFile <filename> option line in the corresponding client configuration file........ and the public key will be stored in the $HOME/.... 70 Additional Security Tools for AIX Systems .... private-key pair: #ssh-keygen By default.. By default.. and has a hidden meaning only for the person generating it.. this will generate an SSH1 RSA key pair each with length of 1024 bits.. In this implementation.pub file on the SSH client.) The public key needs to be stored (via rename or append) in the $HOME/...oooO Key generation complete...........ssh/identity. The use of these files will not be discussed further..... $HOME/. see the appropriate SSH man pages. It is also possible to generate the SSH1 RSA key pair each with length of 2048 bits by using the "-b 2048" flag....oooO......rhosts......ssh/identity... A good passphrase is one that is 10-30 characters long..... is almost impossible to guess.. you will be asked to enter a passphrase........ ..ssh/config file in each user's home directory.equiv.. System-wide options are specified in the /etc/openssh/ssh_config file. Next. For more information on their use..ssh/identity.ssh/authorized_keys file on the SSH server....ssh/identity): Enter passphrase (empty for no passphrase): Enter same passphrase again: Your identification has been saved in /home/khorck/...... sp5en05 /home/khorck # ssh-keygen -b 2048 Generating RSA keys: .. you need to send the public key ($HOME/.. You can specify a different name for the location of the keys......pub.Configuration changes will take effect once the daemon has been refreshed.......ssh/identity.... the file authorized_keys stores the actual keys themselves rather than just the file name(s) of where the keys are stored. Enter file in which to save the key (/home/khorck/.... The key fingerprint is: 8e:f3:19:84:25:91:49:d3:fa:47:de:77:29:f0:15:5e khorck@sp5en05. Your public key has been saved in /home/khorck/.. the private key will be stored in the $HOME/..........shosts. /etc/hosts..... or /etc/shosts...
the SSH server checks for a matching public key locally. SSH2 uses DSA authentication instead of the RSA authentication used by SSH1. is tried. password authentication is tried.3. You may want to use software.ssh/id_dsa file on the client machine. to decrypt the key before you try to use it.ssh/authorized_keys file on the server machine. Be sure. one known as the public key and the other the private key. To review. Private keys are private and must be kept secure. to protect the key by encrypting it when it is not in use. and the client's public key is located in the $HOME/. They are more computationally intensive. but there is no such thing as a free lunch. the second method. generate the keys without passphrase protection (using the -N '' flag): #ssh-keygen -b 2048 -N '' Use of this method requires further safeguards to ensure that the private key file is kept secure. Secure remote access 71 . If a matching key is found and the signature is correct. both to initially create them and to use them for data encryption and decryption. two different authentication methods are tried. this implementation of SSH does not support Kerberos or S/Key authentication. 5.1. If public key authentication fails. The first method tried is public key authentication. which require automatic remote login without prompting for password or passphrase. If that method fails. such as PGP (refer to Section 7. password authentication.3. The client uses the private key (which is a DSA key for SSH2) to sign a session identifier and sends the output to the SSH server. public key authentication uses an asymmetric scheme where each user has a pair of keys. You will pay a performance penalty for using longer keys. The keys are related mathematically but it is computationally impracticable to derive the private key from the public key. such as HACMP and PSSP. "Using PGP" on page 127). The client's private key is located in the $HOME/. access is granted. and it is much harder to break them. At present. Public keys are public and can be distributed freely. Chapter 5. This method is similar to normal password authentication except that the passwords are encrypted rather than being transmitted in the clear. Longer keys (more bits) are cryptographically stronger. On receiving the data.For applications.6 OpenSSH using SSH2 When someone attempts to connect to an OpenSSH server using SSH2. however.
you will be informed and asked to accept or reject the connection.pub files. Any host that has been connected to in the past will be remembered. ssh-2. When connecting to any new host (DSA host key not found in the known_hosts2 file).openssh to /etc/inittab so that the SSH daemon will automatically start during system startup. the host DSA key will be automatically added into your known_hosts2 file and will be reused in future connections. 2. both client and server need to be configured for this version of the protocol. Connected to 0. The default command in rc. telnet to localhost (0) on sshd port (22).1 The SSH installation adds /etc/rc.Once authenticated. By default. As part of the authentication process. Notice that the SSH version is now 2. or Arcfour. Remove or rename the /etc/openssh/ssh_host_key and /etc/openssh/ssh_host_key. the SSH daemon listens on port 22. several encryption schemes are available to ensure the security of the data.ssh/known_hosts2 file on the client. Configuring and using SSH2 To run SSH2. Uncomment 'Protocol 2. the OpenSSH client is configured to support both SSH1 and SSH2. by default. the OpenSSH server daemon (sshd) is configured only for SSH1. To find out which version of SSH (SSH1 or SSH2) you are running.1. Blowfish. To reconfigure the OpenSSH server daemon (sshd) for SSH2. Restart the SSH server By default. If you accept. However. Escape character is '^T'. To further enhance security.0. DSA host keys are stored in the $HOME/. The available schemes are 3DES (default). follow these steps: 1.openssh to start the SSH daemon is: #/usr/local/bin/opensshd -f /etc/openssh/sshd_config -h /etc/openssh/ssh_host_key 72 Additional Security Tools for AIX Systems .. data integrity is assured using hmac-sha1 or hmac-md5.1' in /etc/openssh/sshd_config 3.. CAST128. SSH automatically checks to see if the host that the client is connecting to has been connected to previously.0-OpenSSH_2. # tn 0 22 Trying.
start the daemon with SSH2 support rather than SSH1. A good passphrase is one that is 10-30 characters long.pid` To refresh the daemon: #kill -1 `cat /var/openssh/sshd.The -h flag is used to specify the RSA host key file.pid` Configuration changes will take effect once the daemon has been refreshed. you will be asked to enter a passphrase. if found. and has a hidden meaning only for the person generating it. private-key pair for SSH2: #ssh-keygen -d Notice the addition of the -d flag. you will need to generate a new public-key. Secure remote access 73 . Because SSH2 uses DSA keys rather than RSA keys. During the creation process. This failure triggers the SSH daemon to look for the ssh_host_dsa_key file instead and. this will generate an SSH2 DSA key pair each with length of 1024 bits. It is also possible to generate the SSH2 DSA key pair each with length of 2048 bits by using the "-b 2048" flag or 3072 bits by using the "-b 3072" flag. To manually start the SSH daemon with SSH2 support (using /etc/openssh/sshd_config as the config file and suppress warning messages because of the missing /etc/openssh/ssh_host_key file): #/usr/local/bin/opensshd -f /etc/openssh/sshd_config -Q To manually stop the SSH daemon: #kill `cat /var/openssh/sshd. This will fail because we removed that file as part of the reconfiguration for SSH2. This flag instructs ssh-keygen to generate DSA keys rather than RSA ones. Chapter 5. You can append the -Q flag to the end of the command to suppress the messages generated because of the missing /etc/openssh/ssh_host_key file. By default. is almost impossible to guess.
ssh/authorized_keys2 file on the SSH server.ssh/id_dsa file. Enter file in which to save the key (/home/ali/.ssh/config file in each user's home directory.ssh/id_dsa): Created directory '/home/ali/.ssh/id_dsa. but you will also need to add an IdentifyFile2 <filename> option line in the corresponding client configuration file.pub file on the SSH client.pub) to the SSH server. You can specify a different name for the location of the keys. You next need to send the public key ($HOME/. In this implementation.ssh/id_dsa.$/usr/local/bin/ssh-keygen -d Generating DSA parameter and key. Your public key has been saved in /home/ali/.ssh'.pub. To ssh to the SSH server: sp5en01 /home/khorck # ssh sp5en05 Enter passphrase for DSA key '/home/khorck/. The key fingerprint is: 96:66:f5:5e:83:83:51:8e:f5:90:7c:90:a7:cc:39:3b ali@sp5en05 Refer to the man pages for more detail on the options.ssh/id_dsa. the private key will be stored in the $HOME/. By default. and per-user options are specified in the $HOME/.3! * * * * * * Please see the README file in /usr/lpp/bos for information pertinent to * * this release of the AIX Operating System. the file authorized_keys2 stores the actual keys themselves rather than just the file name(s) of where the keys are stored.ssh/id_dsa. (You may first want to rename the public key to identify the user and host from which the key was generated. System-wide options are specified in the /etc/openssh/ssh_config file.) The public key needs to be stored (via rename or append) in the $HOME/. and the public key will be stored in the $HOME/.ssh/id_dsa': ******************************************************************************* * * * * * Welcome to AIX Version 4. Enter passphrase (empty for no passphrase): Enter same passphrase again: Your identification has been saved in /home/ali/. * * * * * ******************************************************************************* Last login: Thu Aug 17 10:47:17 2000 on ssh from sp5en01 sp5en05 /home/khorck # 74 Additional Security Tools for AIX Systems .
If public key method of authentication fails because the passphrase is wrong or the required files are not set up properly. or DenyGroups options can be set to allow only certain users and/or (primary) groups to connect to the SSH server. to decrypt the key before you try to use it. such as telnet. • The AllowUsers. but you may want to change it to something else for security reasons. however. you should also disable remote access for things. Be sure. Secure remote access 75 . For security reasons. to protect the key by encrypting it when not in use. If so. • The Ports option is used to define the port on which the SSH daemon listens. By default. generate the keys without passphrase protection (using the -N '' flag): #ssh-keygen -d -b 2048 -N '' Use of this method requires further safeguards to ensure that the private key file is kept secure. They are applicable to both SSH1 and SSH2. • The PermitRootLogin option is an option that can be used to further control root access. ftp. • The ListenAddress option is used to control the network interfaces (IP addresses) on which SSH listens. Note that this option must not come before the Port option in the config file. For applications. or those whose keys have changed will be refused. The default is to allow connections from any user and/or group. The arguments must be yes. The default is "yes".7 Other interesting SSH daemon configuration options The following options can be set for the SSH daemon on the SSH server. Connections to hosts with keys not in the known_hosts(2) file. DenyUsers.3. which require automatic remote login without prompting for password or passphrase. or without-password. such as PGP (refer to Section 7. By default. rsh. You may want to use software. • The StrictHostKeyChecking option can be set to ensure that SSH will not automatically add host keys to the known_hosts(2) file. no. 5. and rlogin. "Using PGP" on page 127). it is port 22. The default is to listen on all available interfaces.1.3. such as HACMP and PSSP. this option is set to "no". Chapter 5. the SSH server prompts for a password instead. and any changes to the known_hosts(2) file will need to be done manually. AllowGroups. in addition to this option. you may not want root users to log in remotely. This protects against Trojan horse attacks.
Use this option to protect X11 communications. and NT. ERROR. readme.ssh/authorized 2. The default is AUTH. LOCAL6. interoperability between OpenSSH and SSH from SSH Communications Security is possible. The sftp tool enables file transfers to occur over an encrypted channel. this time to generate a public key (mykey. • The LogLevel option controls the amount of logging done by sshd. and update the authorization file: $echo Key mykey. and can connect to an SSH daemon running either SSH1 or SSH2 protocol. Transfer the public key (mykey. The default is "no". FATAL.ssh2/authorization 5.9 SSH clients for the PC An SSH client for PCs can be obtained from SSH Communications Security at: http://www. thus.pub >> $HOME/. 76 Additional Security Tools for AIX Systems . 5. Users on a host running SSH2 from OpenSSH can connect to another host running SSH2 from SSH. it must be purchased). LOCAL4. LOCAL1. LOCAL5. This option is useful for debugging and audit trails. LOCAL3. run ssh-keygen as follows: $ssh-keygen -f /key/from/ssh. and DEBUG. INFO.pub in this example): $ssh-keygen -f /privatekey/from/openssh -x > mykey.Com According to the OpenSSH README file.1. On the OpenSSH host. • The X11Forwarding option is used to control the forwarding of X11 traffic. and LOCAL7. AUTH. On the OpenSSH host.openssh2. A very interesting feature in this version of the SSH client is secure file transfer (sftp).2.pub) to the SSH. VERBOSE.• The SyslogFacility option can be used to control the type of logging for sshd related messages. It may be freely used by non-commercial users or used for a 30 day trial period by commercial users (after which time. DEBUG violates the privacy of users and is not recommended. providing enhanced security.com The latest version at the time of this writing is SSHWin 2. The values are QUIET.Com host. According to the man pages.1.8 SSH2 interoperability between OpenSSH and SSH. The values are DAEMON. The steps are as follows: 1.ssh. again run ssh-keygen.Com. USER. LOCAL2. The default is INFO.pub 3. This version of the SSH client runs on Windows 95.com -X >> $HOME/. 98.
and is contained in the bos.html 5.x.10 Implications of having SSH With SSH installed. For added security.com. If it is. telnet. A Comprehensive Guide to Virtual Private Networks. The only change to inetd that is required is to the /etc/inetd.3. Volume III . you can securely communicate between hosts with encryption. DenyUsers. DenyGroups.Another tool worth looking at is teraterm. Secure remote access 77 . inetd first runs the TCP Wrapper program (tcpd).1. consider using some of the additional SSH configuration options described in Section 5. TCP Wrapper logs all connection requests to maintain an audit trail of both successful and unsuccessful connection attempts.2 TCP Wrapper TCP Wrapper protects the inetd daemon by defining access controls to services provided by the daemon. 5. AIX 4. Specifically.ipsec fileset. "Other interesting SSH daemon configuration options" on page 75.3 Elements of Security Effective and Efficient Implementation. It is a terminal emulator that runs over SSH. and the ListenAddress option lets you limit SSH traffic to specific network interfaces (IP addresses). Non-secure services.3.conf file.1. The IPSec man pages are a good source of information.3 of the redbook. the AllowUsers. such as ftp. and Chapter 9 of the redbook. and PermitRootLogin options can help you control who has remote access to the SSH server. The tcpd program then checks the incoming connection request against the access controls to ensure that it is a legal request for the requested service and port combination.zip. SG24-5309.7. When a connection comes in for a service and port combination.11 Alternatives to SSH There are alternatives to SSH. and rsh. IPSec comes standard with AIX 4.net. Additional detailed information on how to set up IPSec can be found in Section 7.x enables you to define firewall-like filter sets for network interfaces as well as create virtual private networks (VPNs) between hosts.au/~roca/ttssh. From the standpoint of inetd. It needs to be Chapter 5. authentication. the entire tcpd process is transparent. and data integrity. tcpd runs the requested server program to satisfy the original request. 5. SG24-5962. can then be disabled or removed and replaced with SSH. It currently has support for SSH1 only and is available from: http://www. AllowGroups. The IP Security (IPSec) facility of AIX 4.1.
1 Obtaining and installing TCP Wrapper You can obtain TCP Wrapper (and other tools. for more information on how to do this.4. (The tcpd program will take care of starting the requested server program.1.bff.) TCP Wrapper can be used to protect telnet. "Ensuring the integrity of downloads" on page 136.org/pub/security/index. 5.6. tftp./tcp_wrappers-7.exe UnZipSFX 5.32 of 3 November 1997.exe Install the product.18.104.22.168. inflating: tcp_wrappers-7.1.1. rlogin.asc # ls -l total 1032 -rw-r--r-.bff -rw-r--r-.bff. ftp.porcupine.6.6.6.modified to start tcpd instead of the requested server program.bff inflating: tcp_wrappers-7.html TCP Wrapper is also available from the Bull site in installp format. such as SATAN and POSTFIX.1. and verify that the installation completed successfully: 78 Additional Security Tools for AIX Systems . rsh.wku.0. For example.1. from the same author) from: ftp://ftp. talk.6. by Info-ZIP (Zip-Bugs@lists. Refer to Section 7.0. This tool is really useful on networks where you want to specify which hosts are allowed to connect to a particular service on a particular port and which hosts are not.0. Once downloaded. The version we installed and tested for this book is Version 7. and other services that have a one-to-one mapping with an executable server program. exec.edu).0.asc -rwx-----.0. ensure the distribution has not been tampered with. Inflate the distribution and ensure the filesets are all there and have the correct sizes: # .1 root system 358400 Jul 06 11:27 tcp_wrappers-7.1 root system 162727 Aug 18 10:49 tcp_wrappers-7.6. comsat.1.1 root system 2643 Jul 06 11:28 tcp_wrappers-7. you may want to allow only certain hosts to connect to your FTP server while disallowing all others. finger.
# installp -acgX -d .allow first.2 Configuring TCP Wrapper Once installed.conf with tcpd. Permissions of 600 for the log file will prevent normal users from reading the logs: # touch /var/adm/tcp_wrapper.2. For the appropriate service.0 USR APPLY SUCCESS # lslpp -l freeware.log. you need to decide which inetd-controlled services to protect with TCP Wrapper.rte Fileset Level State Description ---------------------------------------------------------------------------Path: /usr/lib/objrepos freeware.log # refresh -s syslogd You now need to configure the TCP Wrapper access control lists to define which hosts are allowed to execute the protected services and which are not.debug /var/adm/tcp_wrapper. if you want to protect the ftp service.log You need to create the /var/adm/tcp_wrapper.conf as follows: mail. refresh inetd: # refresh -s inetd Next.tcp_wrappers. to have it log to /var/adm/tcp_wrapper.6. configure tcpd to log appropriately.1. then /etc/hosts.0 COMMITTED TCP/IP daemon security wrapper package (with IPv6) 5.log file and refresh the syslog daemon.rte 7.log # chmod 600 /var/adm/tcp_wrapper. modify the ftp line as follows: ftp stream tcp6 nowait root /usr/local/bin/tcpd ftpd Repeat for each service you want to protect with TCP Wrapper. When you have finished making modifications to /etc/inetd.rte 7. For example.6.allow and /etc/hosts.tcp_wrappers. For example.tcp_wrappers. If neither Chapter 5. TCP Wrapper uses the mail facility within syslog to log to /var/adm/syslog. We recommend that you modify the /etc/syslog.deny files.tcp_wrappers. freeware. The search order is /etc/hosts. replace the corresponding server program in /etc/inetd.deny. modify /etc/syslog.1. Access control is done through the /etc/hosts.conf.conf file to log to a different location.rte Installation Summary -------------------Name Level Part Event Result ------------------------------------------------------------------------------freeware. Secure remote access 79 . By default.
itso. or a combination of all of them in these files. Lastly. domain names. see the man pages hosts_options and hosts_access. (Note that you can use IP addresses.5. and when specifying networks.ibm.ibm.contains the match. When specifying domain names. be sure to include the netmask.com domain. For ftp. We then created the /etc/hosts.deny files with the required access control for these services. as in . host names. are allowed to use the service. as in 9. all servers in the itso.com. Access to either service from outside the itso.ibm. we verified the access controls with the tcpdchk -v command: 80 Additional Security Tools for AIX Systems .255. For additional access control options.12. arthur is the only server in the itso.255.0).ibm. with the exception of sp5cw0. we first had to modify the telnet and ftp lines in /etc/inetd. Here is how we configured TCP Wrapper for our lab environment.conf to run /usr/local/bin/tcpd instead of telnetd and ftpd.itso.0. Our server is merlin.allow and /etc/hosts.com domain is denied. We set up TCP Wrapper to protect the telnet and ftp services. be sure to include the leading period in the name.ibm.com. To enable this functionality. For telnet. access is granted.0/255.com domain allowed to use the service.
deny line 1: ftpd 9.ibm.allow line 2: ftpd arthur.0/255.255.0 : deny ALL: ALL: deny # tcpdchk -v Using network configuration file: /etc/inetd.itso.255.12.0.com: allow # cat /etc/hosts.ibm.itso.ibm.deny line 2: ALL ALL deny denied To test this setup.0.allow telnetd: .conf >>> Rule daemons: clients: command: access: >>> Rule daemons: clients: command: access: >>> Rule daemons: clients: command: access: >>> Rule daemons: clients: command: access: /etc/hosts.ibm. access was denied on the first test but granted on the second: Chapter 5. we used the tcpdmatch command.ibm.com.. Secure remote access 81 .com allow granted /etc/hosts.0 deny denied /etc/hosts. stream stream tcp6 tcp6 nowait nowait root root /usr/local/bin/tcpd /usr/local/bin/tcpd ftpd telnetd -a # cat /etc/hosts.# cat /etc/inetd.com allow granted /etc/hosts.itso.com except sp5cw0.itso. As expected.com : allow ftpd: arthur.255.com except sp5cw0.allow line 1: telnetd .ibm..itso.itso.12. We first simulated a telnet test from sp5cw0.conf .itso. ftp telnet .ibm.deny ftpd: 9.ibm.itso. followed by a telnet test from arthur...0/255.255.com.
itso.5 server: process telnetd access: denied # tcpdmatch telnetd arthur.com client: hostname sp5cw0.itso. TCP Wrapper (tcpd) does this by performing a name to IP address lookup and an IP address to name lookup to ensure that both are consistent.0.ibm.3 Additional TCP Wrapper security features By default.com client: address 9.com client: address 9. This double lookup helps ensure the authenticity of the client.0.ibm.itso.ibm.com client: hostname arthur. TCP Wrapper verifies that a client is indeed who it claims to be.12.2.18 server: process telnetd access: granted 5.itso. 82 Additional Security Tools for AIX Systems .# tcpdmatch telnetd sp5cw0.ibm.12.
6. if there is a new vulnerability for named (BIND). These tools are not port or network scanners per se but © Copyright IBM Corp. we also discuss other types of tools. ensure that no new hosts have been introduced without your knowledge.Chapter 6. In this chapter. attempt to exploit the new vulnerability.3. attackers may scan to see if that port is active. and. Port scanners scan systems looking for open ports and known vulnerabilities. and look for potential weak points. Learning these tools gives you two advantages: • You learn how these tools can be used against your network and what information can be gathered. Port and network scanning Network and port scanners are tools typically used by attackers to find vulnerabilities in systems. A port scanner connects to TCP or UDP ports on a machine to determine which ports are active and in LISTEN state (as can be seen with the netstat -an command). With this tool. we discuss fping and nmap which are network and port scanners. The default scan is a TCP connect() scan that uses the standard TCP handshake (explained in Section 3. Important Even though this is considered ethical hacking. For example. The tool also includes many other types of scans. if so.1. such as SAINT. The nmap tool is a premier port scanner. You can then build defense mechanisms around this information. some of which are more subtle (like stealth scans) to prevent detection. The nmap tool uses various scan techniques to determine if a port is active. PortSentry. • You use this knowledge to proactively scan your own network to find possible loopholes before an attacker discovers it. Be sure to get the proper permissions in writing before using these tools on a production network. This technique is also called the ping sweep. They are used to map out your network and look for potential security weaknesses. and lsof. The fping tool is a useful for quickly mapping out the network by sending ICMP echo requests to the entire network or to an IP range. many organizations have very strick policies against it. 2000 83 . you can quickly scan the network and determine which hosts are alive. "SYNDefender" on page 37). In this chapter.
The fping tool is similar to the ping tool except that it sends out ICMP echo request packets in a round-robin fashion. These options are covered in detail in Section 6. • They can be specified in ranges either on the command line or in the file. You can think of it more as a very enhanced version of the netstat -an command. SAINT is an enhanced and updated version of SATAN. "Using fping" on page 86. To run SAINT. 6. This feature enables fping to be a quick tool for scanning an entire network. when configured to drop the connections. and you are unsure which application owns it. and can significantly help to secure your environment.1. and can be configured to drop those connections. • They can be specified in a list in a file.4. The last tool covered in this chapter is lsof. SAINT checks remote machines for a list of known vulnerabilities. you first provide it with a list of target machines to scan. It also gives you recommendations on how to solve the vulnerabilities that it found. It is also a good idea to have a tool to defend against port scans. SAINT (Security Administrator's Integrated Network Tool) is a tool similar to the NSA tool discussed in Section 4. fping takes in a list of IP addresses to be scanned as arguments. The IP addresses passed to fping can be in several forms: • They can be specified in a list on the command line. It alerts you when it detects a port scan (both UDP and TCP). can help to thwart the attacker(s). When executed. 84 Additional Security Tools for AIX Systems .2. and. It is a good tool to help you identify ports which are unknown to you. "Network Security Auditor (NSA)" on page 49.are included here because they are complimentary tools to port and network scanners. This tool is very useful as an early warning mechanism for suspected attacks. PortSentry is just such a tool. lsof can help you determine the owner. and sends out the ICMP packets to each address without waiting for a response. When you see that your server has an active port. SAINT then checks the target machines for the vulnerabilities and reports its findings in an easy-to-read format.1 fping The fping tool is a ping sweep utility that can help map the network topology by sending ICMP echo requests to the entire network or to a range of IP addresses. Note that the lsof tool is not really a security tool.
More information about denial of service attacks and how to prevent them can be found at: www. Refer to Section 7. you may get a response back indicating that a machine is down.255). firewalls are typically configured this way. Once downloaded.ac.cgil 6. Then. inflate the distribution: Chapter 6. The fping tool is also very useful for verifying that the network is configured the way you think it is configured.kernel. For this reason.org/pub/software/admin/mon/ http://www.1. Over time.uk/sites/ftp.fr (installp format) http://www. that there may be machines on the network that have been configured specifically not to respond to ping requests. This may be a false positive caused by a slow network or an overloaded machine. "Ensuring the integrity of downloads" on page 136.2 from the Bull site.0 and .shtml For this redbook.1. we used fping version 2.svn. Denial of service attacks have been successfully launched against the broadcast addresses (both .bull. In other cases. The danger here is that this machine.1 Obtaining and installing fping The fping tool is available for download from: http://www-frec. Port and network scanning 85 . Keep in mind.pentics. suppose a new machine with multiple network cards is introduced on the network with out your knowledge. by virtue of its multiple network cards. ensure that the distribution has not been tampered with.With fping. and documentation rapidly goes out of date. could easily provide an alternate path into your network.net/denial-of-service/white-papers/smurf. a path that enables an attacker to circumvent a firewall. you can quickly determine which hosts are alive on the network and ensure that no new hosts have been introduced on the network without your knowledge.4. it is a good idea to ensure that your broadcast addresses are not configured to respond to ping requests. however. Another good use of fping is to determine if broadcast addresses are configured to respond to pings. You can use fping routinely as an audit tool against your network documentation.mirror. This is especially important for early identification of potential loopholes in your security. For example.net/datamonk/outline. things change. For example. for more information on how to do this.
0. a sample script that will scan an entire Class C network (or any network with netmask 255.5 is alive 22.214.171.124 192. and verify that the installation completed successfully: # installp -acqX -d .0.edu).31 of 31 May 1997. The list of hosts to scan can be specified on the command line or through scripts.2 Using fping The fping tool scans a large number of hosts quickly. Also.bff 92765 Aug 18 10:48 fping-2.168.5. install the fileset freeware.168.fping.5.wku. 192.168.168. inflating: fping-220.127.116.11.# .0 USR APPLY SUCCESS 6.5.3 192. The three addresses are used by fping as its 86 Additional Security Tools for AIX Systems .5.3 is unreachable# In this example.1.fping.rte Installation Summary -------------------Name Level Part Event Result ------------------------------------------------------------------------------freeware.1. Three examples of using fping are given in this section.0) is given in Appendix B.2.1.5.rte 220.127.116.11.2. The first example shows how to run fping with the host list provided on the command line: # /usr/local/bin/fping 192. by Info-ZIP (email@example.com. Scripts to automate the generation of the host list are available for download on the Web.255.exe UnZipSFX 5.rte.168.5 192.5. freeware.3. "Script used to scan a network with fping" on page 126.96.36.199.1.exe Now.168. and 184.108.40.206. fping is used to scan three address: 192.168.fping.bff Verify that it was inflated properly: # ls -l total 384 -rw-r--r--rwx------ 1 root 1 root system system 102400 Jan 14 1998 fping-2.1 is alive 192./fping-2.
15.9 is alive 192.5.1 is alive 192. we also want them scanned to ensure that they do not respond to ping requests because of the vulnerability to denial of service attacks.12.5.5 for increased retry wait times (controlled by the -B flag) The second example shows how to run fping with the /etc/hosts file as input: # cat /etc/hosts | fping 127.0 network (addresses 192.168.0.5. did not respond after a timeout. Please wait for prompt to return.5.15.150 is alive 9.out Obtaining list of hosts to scan and storing the list into /tmp/fping. In this example.168.5.255 can act as broadcast addresses.5. # /tmp/fping.13 is alive 9.168.out Output file is /tmp/fping. 192.out for results Chapter 6.0.script 192.12.0 Please enter filename to output results /tmp/fping.168. fping uses: • A retry count of three.168.168. View output file /tmp/fping.168.168 is unreachable You can use this method as a quick way to ensure that all hosts in the hosts table are alive.0 through 192.168.5 is alive 192.168. excluding the initial ping (controlled by the -r flag) • A 25ms minimum time between sending packets (controlled by the -i flag) • A factor of 18.104.22.168.5.5.0. Port and network scanning 87 .13 is alive 192. Notice that the address.5.3. Since 192.168.168.1 is alive 192.0 and 22.214.171.124 is alive 192.168.host list. inclusive). By default.168.data Scanning hosts now.15.5 is alive 192. "Script used to scan a network with fping" on page 207. It sends ICMP echo requests to each in round-robin fashion.5 is alive 192.2. The third example shows how to run fping with the script found in Appendix B. we are scanning the 192.5.
5.5.13] 192.168. the broadcast addresses.168.168.13. 192. "Broadcast protection" on page 187 for more information about this no option.5] 188.8.131.52.168.1 is alive 192.5.255 is alive [<.0 is alive [<.5.173 sec (elapsed real time) As you can see.168. Refer to Section 8. had responses from 192. 84 bytes.5. that some port scanners (like nmap) can do a really slow scan (-T Paranoid flag) that may be missed by the intrusion detection software.126.96.36.199 ms (avg round trip time) 220.127.116.11.126.96.36.199.192.253 is unreachable 192.168.168.168. however.22.214.171.124.168.2 is unreachable 192.168.5.3 Protection against ping sweeps In general.5. Keep in mind.184.108.40.206. The output file contains the following results: # cat /tmp/fping.5.150 is alive 192.255 : duplicate for [0]. This software implements a form of network sniffer that monitors the network traffic looking for this type of event.40 ms [<.5.41 ms (min round trip time) 1. 1..168. 6. You can also protect your network by disabling ICMP requests from the Internet on your routers.254 is unreachable 256 7 249 0 996 1003 9 0 targets alive unreachable unknown addresses timeouts (waiting for response) ICMP Echos sent ICMP Echo Replies received other ICMP received 0. you can use intrusion detection software to protect your network from ping sweeps.220.127.116.11.3 is unreachable 192.13 is alive 192.9 is alive 192.5 is alive 192. 2.4 is unreachable . 192.The entire scan took less than a minute to run (including generating the list of hosts to be scanned).5.40 ms (max round trip time) 35.out 192.192.71 ms [<..13] 192.168. A check of these two servers reveals that they are configured with the bcastping no option set to on (1).0 : duplicate for [0].168.5.0 and 192.5 and 192. 84 bytes.5] 192.5. There is also software available for download on the 88 Additional Security Tools for AIX Systems .
Web that provides protection against port scanning.txt file that explains the various scan techniques and their use. supports many scanning techniques. Remember that some port scanners can be very subtle (in stealth mode) and use a number of different techniques to prevent detection. Xmas. Learn how to view your network from both the defensive and offensive positions. This reduces the number of potential targets that attackers have. or NULL (stealth) scanning.53/nmap. and reverse ident scanning to determine the owner of the remote process if ident protocol is running. To check for vulnerabilities on a system. you should harden your operating system (refer to Chapter 8. If logging is enabled to track port scanning. You should stay current with the latest techniques by reading articles posted on security sites and subscribing to security-related mailing lists. To minimize your exposure. The default scan is a TCP connect() scan which uses the standard TCP handshake (explained in Section 3. your best defense is knowing how to think like an attacker. "SYNDefender" on page 37).1. 6. run an nmap port scan on the system to see which services are running and exploitable. The nmap tool supports more subtle scans like SYN stealth (half open) scanning that may escape some logging facilities. and enables you to do port scanning of hosts or entire networks.6. remote OS identification to "guess" the remote operating system. However. TCP ftp proxy (bounce attack) scanning. you should thoroughly test these packages prior to putting them in production to determine how sensitive they are to scans. It is very flexible. Included in the package is the /usr/local/lib/nmap-2. It is also visible in the output of the netstat command. and UDP port scanning can also be used. this type of scanning will surely be logged. Other techniques like TCP FIN. Port and network scanning 89 . As always. Read that file for Chapter 6. Other nmap features include ping scanning to determine the hosts that are running. "Securing AIX" on page 139) by removing unnecessary services.2 Network Mapper (NMAP) The nmap tool was written by Fyodor and is well accepted as a premier tool for port scanning. The nmap tool supports various scan techniques to determine if a port is active.3. A port scanner connects to the TCP or UDP ports on a machine to determine which ports are active and in LISTEN state (as can be seen in the output of the netstat -an command).deprecated.
Alternatively.lex and yacc Once you have downloaded nmap. For nmap on AIX. The nmap tool can also be obtained from its homepage at http://www.3.adt. we used nmap version 2. you will need to install them before installing nmap. Next. If lex and yacc are not already installed.fr/.org/nmap for a more detailed description of the techniques and features supported by nmap. 6.4.utils fileset. You can find these in the bos. make sure the distribution has not been tampered with.adt.a better understanding on what nmap can do.2. "Ensuring the integrity of downloads" on page 136 for more information on how to do this.1.53 from the Bull site.utils 4. you also need the /usr/bin/lex and /usr/bin/yacc utilities. you can visit http://www. and install the nmap tool.adt. unpack the distribution. Refer to Section 7. For this redbook.insecure.3.utils fileset is installed: $ lslpp -l bos.adt.1 Obtaining and installing nmap The nmap tool in installp format can be downloaded from http://www-frec. To determine if the bos. (Notice that nmap requires libpcap as a prerequisite): 90 Additional Security Tools for AIX Systems .org/nmap.0 COMMITTED Base Application Development Utilities .utils Fileset Level State Description ---------------------------------------------------------------------------Path: /usr/lib/objrepos bos.bull.insecure.
0.edu). by Info-ZIP (Zip-Bugs@lists. you need to recompile your kernel with Berkeley Packet Filter support. Port and network scanning 91 .bff.nmap.41 of 16 April 2000.0 USR APPLY SUCCESS Once installed.5. If you are getting No such file or directory.0.3 driver loopback driver token ring driver FDDI driver Note There seems to be some nmap functionality in the release that we used for this redbook that does not work properly with the token ring interface.asc # installp -acgX -d .0. freeware.exe UnZipSFX 5.wku. inflating: nmap-2. To enable the drivers. complain to Sun.bff inflating: libpcap-0.rte Installation Summary -------------------Name Level Part Event Result ------------------------------------------------------------------------------freeware.53. try modprobe af_packet or recompil your kernel with SOCK_PACKET enabled. Now.libpcap.wku. If you do not enable the pse drivers.53. uncomment the appropriate entry for your type of network adapter (such as Ethernet or token ring).0.0.5.0. SOLARIS: If you are trying to scan localhost and getting '/dev/lo0: No such file or directory'. activate the drivers: Chapter 6.rte 2.edu). I don't think Solaris can support advanced localhost scan You can probably use "-P0 -sT localhost" though. inflating: libpcap-0.bff.0. try crea the device (eg cd /dev.sS pcap_open_live: /dev/dlpi/tr0: No such file or directory There are several possible reasons for this. enable the pse drivers.exe UnZipSFX 5. and add an entry for the loopback adapter: #d+ #d+ d+ d+ #d+ dlpi dlpi dlpi dlpi dlpi en et lo tr fi /dev/dlpi/en /dev/dlpi/et /dev/dlpi/lo /dev/dlpi/tr /dev/dlpi/fi # # # # # streams streams streams streams streams dlpi dlpi dlpi dlpi dlpi ethernet driver 802.asc # . depending on your operating system: LINUX: If you are getting Socket type not supported.0 USR APPLY SUCCESS freeware.0.# .32 of 3 November 1997.nmap. you will get messages like this one: # nmap -sS -O -P0 -v merlin > /tmp/merlin.53. *BSD: If you are getting device not configured./nmap-2_53_0_0.rte 0.0. or use mknod). MAKEDEV <device>.bff inflating: nmap-2.conf file.5.nmap. by Info-ZIP (Zip-Bugs@lists./libpcap-0_5_0_0. edit the /etc/pse.0.
The port is unprotected. is protecting the port and preventing connection.# strload -f /etc/pse. • Filtered . By default. 6.deprecated.2 Nmap usage The nmap tool reports one of three states for each port scanned. on a production network. 42 Sep 03 22:13 en crw-rw-rw. strload: cannot initialize xtiso: Do not specify an existing file. strload: cannot initialize stddev: Do not specify an existing file. strload: 'spx' already loaded strload: 'sc' already loaded strload: 'stdmod' already loaded strload: cannot initialize dlpi: Do not specify an existing file.2. Be sure to get the proper approval in writing before running tools. strload: 'timod' already loaded strload: 'tirdwr' already loaded # ls -l /dev/dlpi total 0 crw-rw-rw.The target machine will accept() connections on that port. such as a firewall. We recommend that you change the permission to 500. strload: cannot initialize xtiso: Do not specify an existing file. The states are: • Open . strload: cannot initialize xtiso: Do not specify an existing file. strload: cannot initialize dlpi: Do not specify an existing file. strload: cannot initialize xtiso: Do not specify an existing file.1 root system 11. In all likelihood. Important Some organizations have strict policies against network scanning by unauthorized personnel.1 root system 11. such as nmap. 43 Sep 03 22:14 lo You are now ready to use nmap.A device. you probably do not want normal users scanning your network. strload: cannot initialize xtiso: Do not specify an existing file.txt file for highlights of the many different scanning techniques available and suggestions on when you might want to use them as well as the different types of information they provide. Check out the /usr/local/lib/nmap-2. strload: cannot initialize xtiso: Do not specify an existing file. the permission of nmap is 755.53/nmap. • Unfiltered . 92 Additional Security Tools for AIX Systems .conf strload: cannot initialize stddev: Do not specify an existing file. The following screen contains some examples of nmap usage along with the corresponding output.
168. Adding TCP port 53 (state open).50): (The 2 ports scanned but not shown below are in state: closed) Port State Service 23/tcp open telnet # nmap -P0 -v 172.30. Adding TCP port 111 (state open).30.53 by email@example.com. assuming vanilla tcp connect() scan. 2. Use -sP if you really don't want to portscan(and just want to see what hosts are up).16. The TCP connect scan took 0 seconds to scan 1523 ports.30.2.insecure.org/nmap/ ) Strange error from connect (13):Permission denied The 1 scanned port on (172.30.16. Adding TCP port 21 (state open).53 by fyodor@insecure..org ( www. .insecure.0) is: closed Interesting ports on (172.16.1 IP address (1 host up) scanned in 0 seconds # nmap -sS -P0 -O sp5en01 Starting nmap V.org ( www.16.5. Initiating TCP connect() scan against merlinen0 (172.org ( www.5 . Port and network scanning 93 .50) Adding TCP port 23 (state open).insecure.50): (The 1516 ports scanned but not shown below are in state: closed) Port State Service 21/tcp open ftp 23/tcp open telnet 53/tcp open domain 111/tcp open sunrpc 683/tcp open unknown 684/tcp open unknown 6000/tcp open X11 Nmap run completed -.16.513 172.udp.30.org ( www..insecure.30.53 by fyodor@insecure. Adding TCP port 683 (state open).50 Starting nmap V.16. # nmap -P0 -p23.16.# nmap -P0 -p23 -sT 172.4 Nmap run completed -. 2.org/nmap/ ) No tcp. Adding TCP port 6000 (state open).30.50 Starting nmap V.1): (The 1502 ports scanned but not shown below are in state: closed) Port State Service 7/tcp open echo 9/tcp open discard 13/tcp open daytime 19/tcp open chargen 21/tcp open ftp 2770/tcp open sometimes-rpc3 32771/tcp open sometimes-rpc5 TCP Sequence Prediction: Class=truly random Difficulty=9999999 (Good luck!) Remote operating system guess: IBM AIX v3.1 IP address (1 host up) scanned in 3 seconds Chapter 6.. Interesting ports on merlinen0 (172. 2. or ICMP scantype specified. Adding TCP port 684 (state open).1): Port State Service 23/tcp filtered telnet .30.. 2.org/nmap/ ) Interesting ports on merlinen0 (172.0/24 Starting nmap V.514.53 by email@example.com/nmap/ ) Interesting ports on sp5en01 (192.
that some port scanners.2. There is software available for download on the Web that provides protection against port scanning.Read the man pages and review the /usr/local/lib/nmap-2. To minimize your exposure. that the list of vulnerabilities changes with each release of the tool. and is similar to the NSA tool discussed in Section 4. SAINT has many built-in tests for known vulnerabilities. "Network Security Auditor (NSA)" on page 49.3 Protection against port scanners In general. Learn how to view your network from both the defensive and offensive positions. As always. There are numerous scan techniques that can be used under many different circumstances in different environments. it is always a good idea to have multiple tools so that you can cross-verify the results from each. your best defense is knowing how to think like an attacker. We think you will be amazed at what you see. such as nmap. 6.4. Remember that some port scanners can be very subtle (in stealth mode) and use a number of different techniques to prevent detection.com/cgi-bin/vulns. you can use intrusion detection software to protect your network from port scanners. you should thoroughly test these packages prior to putting them in production to determine how sensitive they are to scans. can do a really slow scan (-T Paranoid flag) that may be missed by the intrusion detection software. This reduces the number of potential targets that attackers have. As you do. however.pl for the full list of vulnerabilities known to SAINT. The best way to get familiar with nmap is to play around with it in a lab environment. That is why it is important to make sure you are running 94 Additional Security Tools for AIX Systems . Note. Keep in mind. It is an enhanced and updated version of SATAN. "Securing AIX" on page 139) by removing unnecessary services.wwdsi.3 Security Administrator's Integrated Network Tool (SAINT) SAINT is a useful scanning tool for system vulnerabilities.53/nmap. This software implements a form of network sniffer that monitors the network traffic looking for this type of event. remember to also view what you see from the eyes of a potential attacker. You should stay current with the latest techniques by reading articles posted on security sites and subscribing to security-related mailing lists. See http://www. however. However. you should harden your operating system (refer to Chapter 8. 6. Even if you have other similar tools.deprecated.txt file to get a good overview of the nmap tool and its capabilities.
It also has a very cool demo/tutorial of the product. Be sure also to set the permissions as tightly as possible. it is not a good idea to have a C compiler loaded on a production system.the latest version of the software (similar to what you are probably already doing with virus-protection software). Download it from http://www. SAINT can be run from the command line or from a browser. The online documentation is plentiful and provides explanations of how to use the tool. The browser interface is nice in that it enables you to run the tool and view the results all within the browser.2.1 Obtaining and installing SAINT SAINT is only available in source-code form. a copy of PERL.3. Compile the program on a non-production system. and only move the executable program to the production system. Port and network scanning 95 . We used the version 4.html This site provides a lot of detailed information about the tool.wwdsi. 6. you will need to the gzip utility (available for download from the Bull site).html.4 C compiler for AIX under AIX 4.wwdsi.3. The SAINT homepage is at: http://www. At the time of this writing. and install it as shown in the following screen. Chapter 6.com/saint/index. and a C compiler. the current version is SAINT 2. It even gives recommended procedures for solving the vulnerabilities it finds. You will then need to compile it with a C compiler.com/saint/index. Important For security reasons.3. To install the package. Download the package.
Trying to find Perl.# ls -l total 1352 -rw-r----. Invoke the SAINT browser interface./.gz # tar -xvf saint-2.. Perl is in /bin/perl ...o Additional installation information is available in the README file that comes with the product. # perl reconfig Reconfiguring. shown in Figure 12 on page 97...tar. cc -o . make "LIBS=" "XFLAGS=-DAUTH_GID_T=in ..2.. To run SAINT. you need to ensure that your X11 environment is set up correctly to display the browser..tar. The default browser was set automatically when you ran perl reconfig during the installation process. # make CC=cc aix cd src/misc. by typing saint... ... Changing paths in config/paths.sh. If you are going to use the browser interface..2. # make Usage: make system-type... Stop..2.1 root system 687209 Sep 11 14:57 saint-2.. ...gz # gzip -d saint-2.. Known types are: aix osf freebsd openbsd bsdi dgux irix4 irix hpux9 hpux10 hpux11 linux-old linux-new solaris sunos4 sunos5 sysv4 tru64 unixware7-udk make: 1254-004 The error code from the last command is 1. . 96 Additional Security Tools for AIX Systems .tar ... you can either use the command line (saint -h) or a browser.Checking to make sure all the targets are here./bin/ddos_scan dds.
Port and network scanning 97 .Figure 12. SAINT main page Chapter 6.
2. /etc/hosts.2 Using SAINT Important Some companies have strict restrictions against doing such scanning. you may want to play safe by ensuring that backups are done prior to scanning since crashes may occur under some severe conditions. (Without this added feature. 3. Click the Data Mgmt. Ensure that you have the necessary authorization prior to running these scans. The steps for configuring SAINT. Select the scan method. you will need to regularly check the PortSentry logs yourself.deny file so that further connection attempts to protected services are denied.4 PortSentry PortSentry from Psionic is a port scan detector. it can react by adding the IP address of the attacking host into the TCP Wrapper. buttons to configure SAINT for your requirements. When used in conjunction with the LogCheck utility (also from Psionic). It can also kill off the route from the attacking machine. 6. then click the By Approximate Danger Level button to analyze the results. 5. Also. Click the Target Selection button to select the target systems to scan. having a defense against it will help secure your environment. Click the Data Analysis button.3. then click the Start the scan button. running a scan. Since port scanning is a common part of an attacker's routine. Click the Documentation button for access to the full product documentation for SAINT.6.psionic.com/abacus/ 98 Additional Security Tools for AIX Systems . PortSentry can notify you through email when it detects a possible attack. and Config Mgmt. and viewing the results are as follows: 1. Select each item in the list for further details.) The PortSentry homepage is can be found at the following address: http://www. 4. When PortSentry detects a port scan.
0. 21 media blocks. 14 media blocks.install. x portsentry-1. x portsentry-1.Z drwxr-xr-x 4 root system 512 Sep 12 14:52 share drwxr-xr-x 6 root system 3584 Sep 12 16:00 src [/usr/local] # gzip -d portsentry-1. 1 media blocks.c.h. 2912 bytes. 5475 bytes.0/README. 7728 bytes. 8 media blocks.0/portsentry.0/README. 6. To install the package.h. 2325 bytes. x portsentry-1. 52759 bytes.0/ignore. x portsentry-1. x portsentry-1.0.tar.0/portsentry_io. "Ensuring the integrity of downloads" on page 136. Also.1.0/README.0/portsentry. 5519 bytes.tar x portsentry-1. x portsentry-1. 9 media blocks. 2215 bytes. and unpack it as follows. 10 media blocks.tar. 40 media blocks. 20191 bytes.0/portsentry_tcpip.0 x portsentry-1. [/usr/local] # ls -l total 408 drwxr-xr-x 2 bin bin 512 Sep 12 14:52 bin drwxr-xr-x 3 root system 512 Aug 30 19:04 include drwxr-xr-x 13 root system 512 Sep 12 14:52 lib drwxr-xr-x 6 root system 512 Aug 30 19:04 man -rw-r----. 1 media blocks. 5 media blocks.stealth. x portsentry-1. once you have implemented PortSentry. x portsentry-1. x portsentry-1.h. 10403 bytes. We used the version 4.methods. 5 media blocks.0/CREDITS.0/README.c.4 C compiler for AIX under AIX 4. 6 media blocks.h.4. 4160 bytes. 2438 bytes. 39 media blocks.COMPAT.0/portsentry_config.conf.3. x portsentry-1. x portsentry-1.0. It is amazingly easy to lock out legitimate clients. 3896 bytes. 11 media blocks.3. you need the gzip utility (available for download from the Bull site) and a C compiler. 11 media blocks.h.0/portsentry.csh.0/Makefile. x portsentry-1. Download it from http://www.1 root system 184320 Sep 12 15:36 portsentry-1.0/portsentry_io.0/CHANGES.Important Be sure to thoroughly test your PortSentry rules and thresholds before putting them into production. 2715 bytes. Refer to Section 7.1 Obtaining and installing PortSentry PortSentry is only available in source code form. Port and network scanning 99 . Download the package.0/portsentry_util. Ensure the integrity of your download by verifying your signature posted on the site.psionic. 5 media blocks. continue to monitor it to ensure that it is really doing what you expected it to do.gz [/usr/local] # tar -xvf portsentry-1.0/LICENSE. x portsentry-1. 19871 bytes.0/portsentry_util. 334 bytes.c. x portsentry-1. x portsentry-1.ignore. 4688 bytes. 12 media blocks. x portsentry-1. 6 media blocks. 236 bytes.4. x portsentry-1.com/abacus/portsentry/.0/portsentry. 16 media blocks. 6133 bytes. 104 media blocks. 6729 bytes. Chapter 6. x portsentry-1.
see Section 5.Additional installation information is available in the README. and specify your choices for logging options. and set the file permissions to prevent normal users from accessing it: # touch /var/adm/portsentry # chmod 600 /var/adm/portsentry 4. Notice also that we installed PortSentry in /usr/local/portsentry.conf file.conf file and to the README. Create the PortSentry log file. but you are free to install it somewhere else.debug mail. For example.install file that comes with the product. "TCP Wrapper" on page 77. to have PortSentry write to a dedicated log file. The steps to install and configure PortSentry are as follows: 1.conf" #define SYSLOG_FACILITY LOG_LOCAL0 #define SYSLOG_LEVEL LOG_DEBUG 2. and specify your PortSentry configuration choices.h header file.debug /var/adm/portsentry /var/adm/tcp_wrapper 3. set SYSLOG_FACILITY to LOG_LOCAL0. Edit the /etc/syslog. pay special attention to the PORT_BANNER and KILL_ROUTE options: 100 Additional Security Tools for AIX Systems .2. and add a line for the PortSentry log file: local0. Refer to the comments in the porsentry.install file for more information about the various configuration options.conf file. For more information on how to install and configure TCP Wrapper. To enhance the protection provided by PortSentry. you should have TCP Wrapper installed and running. In particular. If you do. Edit the portsentry. be sure to modify the relevant fields in the header file to reflect your choice: #define CONFIG_FILE "/usr/local/portsentry/portsentry. Edit the portsentry_config.
32773.635.. .54320" UDP_PORTS="1.54320" #UDP_PORTS="1.32771.327220.127.116.113.54321" # # Use these if you just want to be aware: #TCP_PORTS="1..11.32771.40421.12345.66..32 722.214.171.1240.161.1080.5742.40425.31337.512.7.110..54321" .7.32772.32774.1080. make aix.513.12345.32770. 20034. # Generic #KILL_ROUTE="/sbin/route add $TARGET$ 333. INSTALLDIR.188.8.131.52.69.32774. and add the IP addresses of your local interfaces.126.96.36.1995.162.119..6000.518.31337.32774.49724.640.700.32773.79.32772.3 1337. Edit the Makefile.5742.32773.30303.32772.143.514. 6.111.4000.12346.history" # Hosts that have been denied this session only (temporary until next restart) BLOCKED_FILE="/usr/local/portsentry/portsentry.69.ignore file.666 .68.80.32773.700.555.70.666" KILL_ROUTE="/usr/sbin/route add $TARGET$ 127.67.6667.blocked" .# Un-comment these if you are really anal: TCP_PORTS="1.2000.32771.15220.127.116.11.444.2001. .640.31337. and modify CFLAGS.ignore" # Hosts that have been denied (running history) HISTORY_FILE="/usr/local/portsentry/portsentry. and make install.6667. Edit the portsentry. In our case.6001.12346. remove the -Wall flag.641...474.635..2000.517.2049.513.327188.8.131.52.4001.20034.138.11.40421.1524.635. 635. IGNORE_FILE="/usr/local/portsentry/portsentry.143. Run make.641.540. and CHILDDIR lines as follows: CFLAGS = -O INSTALLDIR = /usr/local CHILDDIR=/portsentry 7. This is where the portsentry executable will be located: Chapter 6.119.49724.32774. the install directory is /usr/local/portsentry.1 5. Port and network scanning 101 .
hpux-gcc. generic This code requires snprintf()/vsnprintf() system calls to work. 8. hpux. etc) WARNING: This version and above now use a new directory structure for storing the program and config files (/usr/local/portsentry).conf chmod 700 /usr/local/portsentry/portsentry Edit /usr/local/portsentry/portsentry.c: [/usr/local/portsentry-1./portsentry.conf /usr/local/portsentry cp . osf.0] # make Usage: make <systype> <systype> is one of: linux./portsentry .0]# make install Creating psionic directory /usr/local Setting directory permissions chmod 700 /usr/local Creating portsentry directory /usr/local/portsentry Setting directory permissions chmod 700 /usr/local/portsentry Copying files cp .. Please make sure you delete the old files when the testing of this install is complete.[/usr/local/portsentry-1.c .ignore chmod 600 /usr/local/portsentry/portsentry. ./portsentry_io./portsentry_util./portsentry. 102 Additional Security Tools for AIX Systems . [/usr/local/portsentry-1./portsentry. Any existing files will be overwritten. bsdi.ignore /usr/local/portsentry cp .0] # make aix SYSTYPE=aix Making cc -O -o .c . Start PortSentry in either TCP or UDP mode. freebsd...c . If you get it to work on an unlisted OS please write me with the changes./portsentry /usr/local/portsentry Setting permissions chmod 600 /usr/local/portsentry/portsentry. netbsd. Install: make install NOTE: This will install the package in this directory: /usr/local Edit the makefile if you wish to change these paths.conf and change your settings if you haven't already. solaris. openbsd. bsd.. /portsentry_util. If you run a modern OS it should work on your system with 'make generic'. (route. aix.
(For more information about installing and configuring TCP Wrapper. If you find an unknown port with the netstat command. you can download the LogCheck tool (http://www.) This method may. (Note that KILL_ROUTE will only add routes to remote systems on different networks. you must already have TCP Wrapper configured and running on the server. You enable this method with the KILL_ROUTE option in the portsentry.deny. Recall that TCP Wrapper only protects services started by inetd and then only the ones that you have wrapped with TCP Wrapper.conf file.2.purdue. Test until you are satisfied that the tool is properly configured. not provide sufficient defense against port scanning. To use this method. It is also available in Chapter 6.2.conf match what you have listed in the portsentry. you can use lsof to get more information about it.com/abacus/logcheck/).edu/pub/tools/unix/lsof.conf file. you must make sure that the ports that you have wrapped in /etc/inetd.2 Defense provided by PortSentry PortSentry provides two major forms of defense: • The first is based on TCP Wrapper. The tool is available via anonymous ftp from ftp://vic.5 List Open Files (lsof) The lsof tool is quite literally used to list open files.h header file.4. 6. We recommend that you enable both methods. Once enabled. the AIX version of the tool that we tested did not have support for detecting and blocking stealth scans. including network sockets.cc. In addition. such as ownership. by itself.For email alerts and better log management. • The second is based on the loopback adapter. see Section 5. "Configuring TCP Wrapper" on page 79. IP addresses of suspected attack hosts will automatically be added to the TCP Wrapper access control file /etc/hosts. Once enabled. 6.) 10.[/usr/local/portsentry]# portsentry -tcp [/usr/local/portsentry]# portsentry -udp 9. or write your own scripts to do something similar. Unfortunately. This new route will effectively block a lot of normal port scans. PortSentry will automatically add routes through the loopback adapter on your server to the IP addresses of the suspected attack hosts. Remember that in UNIX (and AIX) most things appear as files. You enable this method with the WRAPPER_HOSTS_DENY option in the portsentry_config. Port and network scanning 103 .psionic.
inflating: lsof-4.bff inflating: lsof-4.1 root system 369866 Sep 01 14:48 lsof_aix432-22.214.171.124.edu).50.0. Type F4 or ESC+4 to list filesets 5.bff.asc # ls -l total 2640 -rw-r--r-.toc # installp -acgX -d . freeware. inflate it.50.50 from the Bull site.50.50.exe # rm .0.1.1 root system 2580 Jul 04 10:38 lsof-4.4. and retrying the installation again. Select Find freeware. (dot) and press Enter 4.50./lsof_aix432-4.32 of 3 November 1997. Press Enter three times to install If the installation failed with a fileset not found message. Type .1 Installing lsof Download the package and ensure that it has not been tampered with. "Ensuring the integrity of downloads" on page 136. verify that the installation completed successfully: 104 Additional Security Tools for AIX Systems .lsof.rte Alternatively.1 root system 972800 Jul 04 04:55 lsof-4. Select Install and Update from ALL Available Software 3.asc -rwx-----.wku.exe UnZipSFX 5. See Section 7. try exiting SMIT.0.0. removing the . Type smitty installp 2. 6.installp format from the Bull site. Either way (installp or SMIT).0. and install it with either the installp command or SMIT: # chmod u+x lsof_aix432-4. for more information on how to do this.bff.0.50.toc). Once you have verified the integrity of the package.0.toc file (#rm .lsof (F7 or ESC+7 to select the fileset) 6.50.bff -rw-r--r-. you can use SMIT to install the fileset: 126.96.36.199. by Info-ZIP (email@example.com. The version we used during the writing of this redbook was version 4.0.exe # .
* (state) ESTABLISHED LISTEN LISTEN LISTEN LISTEN LISTEN LISTEN LISTEN Assume that UDP port 32768 is the unknown and that you want to find out which service owns it.32770 *.5.2 Using lsof The lsof tool is very versatile.865 *.32768 *.* tcp 0 0 *.* udp4 0 0 *.telnet merlin.sunrpc *.rte Fileset Level State Description ---------------------------------------------------------------------------Path: /usr/lib/objrepos freeware.rte 4.865 *.50.50.* tcp4 0 0 *.864 *.lsof. You can run lsof as follows to find out: Chapter 6. Suppose you run the netstat -af inet command and notice some unknown ports.ftp *.0 COMMITTED List Open Files 6.* *.32768 *.Installation Summary -------------------Name Level Part Event Result ------------------------------------------------------------------------------freeware.time *.* udp4 0 0 *. We illustrate just one simple use for it here.telnet *.* tcp4 0 0 *.rte 4.lsof.0.864 *.time *.0.* udp4 0 0 *. Port and network scanning 105 .0 USR APPLY SUCCESS You can also check it with the lslpp command: # lslpp -l freeware.32809 tcp 0 0 *.lsof.* tcp4 0 0 *.* tcp4 0 0 *.* udp4 0 0 *.* udp4 0 0 *.* tcp4 0 0 *.* *. The output of the netstat command might look something like this: # netstat -af inet Active Internet connections (including servers) Proto Recv-Q Send-Q Local Address Foreign Address tcp4 0 2 arthur.* udp4 0 0 *.* udp4 0 0 *.
stevenspublishing. this is DEVICE SIZE/OFF NODE 0x700f3a00 0t0 UDP 0x70030300 0t0 UDP 0x700e9d00 0t0 UDP 0x700e9a00 0t0 UDP 4.6 Intrusion detection Intrusion detection software can help protect your network against attacks and alert you (via email) to take appropriate action. the sensitivity of the tools is key.4.3. If an activity matches the signature of a known attack pattern. Keeping your intrusion detection software current will ensure that the latest attack patterns are known to the sensor. you can place a network sniffer (also known as sensor) on your network to monitor network activity. An attacker usually follows some form of pattern (also known as a signature pattern) when attacking a target. 106 Additional Security Tools for AIX Systems .0.statd 6200 root 20u IPv4 rpc. visit: http://www. you can use PortSentry discussed in Section 6. to protect against port scanners. "PortSentry" on page 98.0. Remember that some forms of attack are very subtle (and slow). To protect your network. so. an alert can be raised forewarning you of the impending attack.statd 6200 root 22u IPv4 version 4.2. Examples of intrusion detection tools are: • • • • • ISS RealSecure NFR Network Flight Recorder Cisco NetRanger Computer Associates SessionWall Axent NetProwler For a comparison of the different products. In this case. such as nmap. Care should be taken to ensure that your intrusion detection software is properly configured. NAME *:syslog *:time *:864 *:865 From the output.nsf/PubHome/1F93DB21EE 40EE8086256855005882EB?Opendocument As already mentioned. 6.com/stevens/secprodpub.3.# lsof -i udp -p 32768 lsof: WARNING: compiled for AIX COMMAND PID USER FD TYPE syslogd 3978 root 4u IPv4 inetd 5986 root 8u IPv4 rpc. you can see which services are using this port and take further action if necessary.3. you would have PortSentry servers as sensors to alert you to possible attacks.
As another intrusion detection option.com Chapter 6.ers. For more information. In addition to intrusion detection support. Port and network scanning 107 . you have at your disposal security experts to help with the defense and postmortem activities.ibm. these companies can also do an evaluation of your current security posture and recommend various ways to improve it. visit: http://www. you may want to consider hiring an outside company with security experts to provide 24x7 watch over your network. The biggest advantage to outsourcing this support is that in the unfortunate event of an attack and/or break-in.
108 Additional Security Tools for AIX Systems .
be non-reusable after expiration. but. System programs are replaced with modified versions that enable the attacker to gain easy access into the system again or that provide additional information to the attacker for future attacks on this or connected systems. they should be configured to not allow direct logins. they should be configured to require the use of the su command. Password integrity is critical because it is almost impossible to differentiate between a valid user and an attacker who has purloined a user's password. and never be shared. In this chapter. be they system or data files.Chapter 7. Once an attacker has penetrated the system. A better solution is to provide the users with encryption tools that they can use to protect their sensitive information (even from root). we cover the following tools: • • • • Tripwire John the Ripper Pretty Good Privacy (PGP) MD5 © Copyright IBM Corp. but to ensure password integrity. Passwords should be very difficult to guess. Internet downloads are another area of concern when it comes to system and data integrity. you really should have a program specifically designed for cracking bad passwords. they need to be sure that what is downloaded is really what they expected and not something that has been tampered with by a would-be attacker. you need to have a security tool in place to give you assurance that your system files are intact. Some scan programs (such as NSA) will check for obvious passwords. the root user can still bypass these permissions and access the files. when they are necessary (such as with root). System integrity also covers the area of password policy. However. such as root for root. Therefore. Sensitive files need to be secured from unauthorized access. Instead. are not tampered with or accessed illegally. System and data integrity System and data integrity are important aspects of security. 2000 109 . Standard UNIX file and directory permissions provide some measure of protection. a common behavior is to leave backdoors and Trojan-horse programs in the system. expire regularly. You need to be sure that files. Downloads are common in today's environment. The privacy of your users also needs to be protected. shared accounts are a bad idea because of the loss of accountability. In other words. and you need to provide a way for system users to ensure the integrity of their downloads. In general.
A tool. Ensuring strong passwords should be part of the security guidelines of any organization. In order for this tool to be effective. Once you have downloaded the file. such as this one. to its ease of use. John the Ripper is a password cracker program. Tripwire creates a database with the checksums of system binaries and configuration files. If the values are different.Tripwire is a tool that provides assurance that systems and configuration files have not been modified. a database is created to store all relevant security information about important files (as defined in the tw. clean system. such as one that has just been installed and has not yet been connected to an external network. Tripwire is a tool to help you detect and correct this sort of thing. Pretty Good Privacy (PGP) is a popular encryption tool that you can make available for users to use to protect their sensitive files. do not unpack and/or execute the file.1 Tripwire Tripwire is a public domain tool that helps you ensure (with a high degree of certainty) that a list of system or configuration files has not been modified. MD5 computes a unique checksum against a file. these only go so far in forcing users to pick good passwords. in no small part. run MD5 against it and compare the output with the published value. Tripwire should 110 Additional Security Tools for AIX Systems . This database should be created on a known. and uses them to periodically compare against the current copies of those files. PGP is a very popular tool due. AIX provides a number of facilities for implementing strong password policies.config file). 7. Tripwire alerts you to this condition. Put simply. and notify the owners of the site. and the algorithm that MD5 uses is very sensitive to even the slightest changes to the file. Tripwire computes two (or more) checksums of the system files. This is achieved in part by replacing some system files with modified versions. During Tripwire configuration. If any of the files have been replaced or tampered with. the site from which you are downloading the file needs to have published the MD5 checksum. stores them in the database. MD5 is a tool for ensuring the integrity of files downloaded from the Internet. A normal part of an attacker's routine is to install a backdoor into the system to allow for an easy return. It can also be used to securely communicate with remote users via encrypted email. However. will go the extra step and help you to uncover (and correct) weak passwords before an attacker does. such as Trojan horse programs. Delete it. This database provides the security baseline for those files.
tripwiresecurity. Tripwire becomes worse than useless.cfml for a comparison of the two different versions. The TSS Web site is located at http://www. and so on. Purdue University transferred management of Tripwire to Tripwire Security Solutions. For example. Inc. In other words. ensure it has not been tampered with before installing it. the configuration file.com/. This ensures that you have a "known good" copy of the database. System and data integrity 111 . APARs.) For maximum protection. They should only be restored to the system when you are ready to run Tripwire again.1. Tripwire should also be run just before and just after any changes are made to the system that alter the system files. After you download the package. Tripwire checks the files listed in the configuration file against its database and reports any discrepancies found. Chapter 7. See http://www.bull.de/pub/out/.then be run regularly to check each of these system files to ensure that they have not been modified inappropriately.com/products/index. PTFs. Tripwire should be run just after system installation is complete. The version we downloaded for this redbook was Tripwire 1. To escape detection. they could modify the checksums to match the altered system files that they have loaded on the system.tripwiresecurity. "Ensuring the integrity of downloads" on page 136. If any of the Tripwire components are compromised.1 Obtaining and installing Tripwire Tripwire was initially developed at Purdue University in 1992. while still in single-user mode and not connected to an external network. when you next run Tripwire.1. and the Tripwire executable should be stored securely offline. Ideally. it appears that all is well. but they are not in installp format. A version of Tripwire in installp format is available from the Bull site at http://www. for more information about how to do this. The for-purchase version has additional functionality that you may find useful. the database. timestamp. 7. and so on). which is extremely difficult to do. Then. for example. In 1998.4. they will need to be compiled for AIX and manually installed. Newer versions are available from TSS. O/S upgrades. (TSS). an attacker would have to replace a system file with an identical file (size. checksums. Refer to Section 7. if attackers got hold of the Tripwire database. They offer open-source and for-purchase versions of Tripwire.2. (The reason this is so difficult is that Tripwire uses two different checksum algorithms to compute the checksums. Creating a modified system file to match both original checksums is no small task.
1.tripwire_bin command to verify the installation. and verify that it was successfully installed: # installp -acqX -d .bff 336614 Aug 16 13:58 tripwire-220.127.116.11.tripwire.db_<hostname> The program file is the executable that should be run periodically to check system integrity.2 Configuring and using Tripwire The important files for Tripwire are: • The program file: /usr/security/bin/tripwire • The configuration file: /usr/adm/tcheck/tw./tripwire-1.tripwire_ 1.tripwire.0.2.Inflate the package.config • The database: /usr/adm/tcheck/databases/tw.0. freeware.exe inflating: tripwire-1.exe Install the fileset (with installp or SMIT).1. The configuration file contains the list of system files that you want to protect. and verify that it inflated properly: # . which uses it to populate the database.tripwire.bff # ls -l total 1480 -rw-r--r--rwx------ 1 root 1 root system system 412672 Aug 09 1996 tripwire-1. The database stores the following information about the files and directories listed in the configuration file: • Permission and file mode bits • Access timestamp • Inode number • Modification timestamp 112 Additional Security Tools for AIX Systems .2.exe Archive: .0.1.1.2.2. This file needs to be created prior to the initial run of Tripwire.2. 7.0 USR APPLY SUCCESS You can also use the lslpp -l freeware./tripwire-1.1.0.tripwire_bin Installation Summary -------------------Name Level Part Event Result ------------------------------------------------------------------------------freeware.0.
System and data integrity 113 . the database is updated with the current configuration information.1.• Number of links (ref count) • Inode creation timestamp • User ID of owner • Group ID of owner • Size of file • Signature 1 (MD5 by default) • Signature 2 (Snefru by default) It is the combination of the two different signatures coupled with the file size that makes it extremely difficult to create another file with the same characteristics. This is required when legitimate changes are made to the system. Tripwire creates the databases subdirectory in the current working directory and then creates the database under the databases directory. you will most likely need to modify it for your systems. so.db_<hostname>) based on the configuration file. Note that the default configuration file was created for AIX 4. Tripwire creates the database (/usr/adm/tcheck/databases/tw.5. Tripwire runs in one of four modes: • Database Generation • Database Update • Integrity Checking • Interactive Update In Database Generation mode. To initialize the database: # cd /usr/adm/tcheck # /usr/security/bin/tripwire -initialize Important Be sure that your current working directory is set to /usr/adm/tcheck before initializing the database. In Database Update mode. such as changes to the system files or application of operating system patches: Chapter 7.
cfg to create an initial delta file for the Tripwire configuration file: # cat /etc/security/sysck.3 Configuring Tripwire The most important step in the configuration of Tripwire is creating an accurate and complete configuration file. or create your own from scratch.sort file with additional files and directories that you deem important.list.out In Interactive Update mode. Tripwire generates a report of added. deleted.db_<hostname>): # /usr/security/bin/tripwire | tee /tmp/tripwire. Modify the tripwire.cfg | grep ":" | sed s/://g | \ >sort > tripwire.# /usr/security/bin/tripwire -update <path_of_changed_file_or_directory> In Integrity Checking mode.list.list. The configuration file should contain the list of system files and directories that you want to have Tripwire protect.sort 2. This is done by comparing the current configuration information against that which is stored in the database (/usr/adm/tcheck/databases/tw.sort # chmod 600 tripwire. or changed files.1. Tripwire also prompts you to apply these changes to its database: # /usr/security/bin/tripwire -interactive 7. Use /etc/security/sysck. You can either start with the supplied Tripwire configuration file. rather than just reporting things that have changed.5. which was created for AIX 4. We used the former technique: 1.1. We added the following: 114 Additional Security Tools for AIX Systems .
Once you are satisfied with the output of CheckConfig.login: not found /.rhosts: file /. 6. System and data integrity 115 . (See the /usr/local/lib/tripwire-1. Merge the contents of this file with tw.netrc: not found /.config file and run CheckConfig again.CheckConfig file for more information about how to use this script.cshrc: not found /. initialize the database: Chapter 7.cfg R /usr/lib/objrepos L # files frequently modified /etc/objrepos L /usr/bin/whoami R /usr/bin/sh R /usr/bin/Rsh R /usr/bin/tsh R /usr/bin/bsh R /usr/bin/ls R /usr/adm/wtmp L ## protect other binaries you installed in your system. you may need to make additional changes to the tw.2/README.profile: file /. Based on the output of the CheckConfig script.): # /usr/local/lib/tripwire-1. Eg security tools /usr/local/bin/nmap R /usr/local/bin/ssh R /usr/local/bin/pgp R /usr/local/bin/lsof R 3.config /: directory /.kshrc: file /usr/lib/boot/unix_mp: file /usr/lib/boot/unix_up: not found /usr/lib/boot/unix_kdb: not found /usr/lib/boot/unix_mp_kdb: file /unix: symlink /dev: directory /sbin: directory /usr/local: directory /usr: directory 5. 4. Verify the configuration file with the Tripwire CheckConfig script.kshrc R # may not exist /usr/lib/boot/unix_mp R /usr/lib/boot/unix_up R /usr/lib/boot/unix_kdb R /usr/lib/boot/unix_mp_kdb R /unix R /etc/security/limits R /etc/security/login.2/CheckConfig -v /usr/adm/tcheck/tw./.config file that came with the Tripwire package.
it reports what it thinks are inconsistencies.db_sp5en01. ### ### Make sure to move this file file and the configuration ### to secure media! ### ### (Tripwire expects to find it in '/usr/adm/tcheck/databases' 7./databases/tw.[/usr/adm/tcheck] # /usr/security/bin/tripwire -initialize ### Phase 1: Reading configuration file ### Phase 2: Generating file list ### Phase 3: Creating file information database ### ### Warning: Database file placed in . (As long as your system is still off the network. Update the configuration file with the requested changes. When you first initialize the Tripwire database. you can be sure that these changes are a byproduct of normal system behavior. and then reinitialize the database.): 116 Additional Security Tools for AIX Systems .
System and data integrity 117 . Repeat this process as many times as needed until Tripwire reports that the changes remaining are zero: Chapter 7.boot changed: -rw-r--r-.root 27029 Jul 20 14:16:31 1999 /sbin/rc.root 1826 Sep 11 18:54:53 2000 /etc/inittab changed: -rw-r----.root 0 Sep 11 18:55:26 2000 /etc/pmd_lock2 changed: -rw------.root 0 Sep 11 18:55:26 2000 /etc/pmd_lock ### Phase 5: Generating observed/expected pairs for changed files ### ### Attr Observed (what it is) Expected (what it should be) ### =========== ============================= ============================= /sbin/rc.boot st_ctime: Mon Sep 11 18:53:50 2000 /etc/inittab st_ino: 403 /etc/security/lastlog st_mtime: Mon Sep 11 18:55:36 2000 st_ctime: Mon Sep 11 18:55:36 2000 md5 (sig1): 2noet1FpnqVIw1XwfZEL9f snefru (sig2): 2egxLZbqhjIm6g64gpYOSR /etc/pmd_lock2 st_ino: 409 /etc/pmd_lock st_ino: 476 Sun Sep 10 23:15:04 2000 405 Mon Sep 11 17:45:35 2000 Mon Sep 11 17:45:35 2000 25zTiUps0WezoeLB7nJUki 2jbnbYfhkSkdJWLppnIFf.[/usr/adm/tcheck] # /usr/security/bin/tripwire ### Phase 1: Reading configuration file ### Phase 2: Generating file list ### Phase 3: Creating file information database ### Phase 4: Searching for inconsistencies ### ### Total files scanned: 6667 ### Files added: 0 ### Files deleted: 0 ### Files changed: 6111 ### ### After applying rules: ### Changes discarded: 6108 ### Changes remaining: 5 ### changed: -rwxrwxr-.root 1412 Sep 11 18:55:36 2000 /etc/security/lastlog changed: -rw------. 476 477 8.
Just one key system file missing from the configuration file could open the door for an attacker. or on the local machine encrypted with PGP. and the tripwire executable in a safe area. 118 Additional Security Tools for AIX Systems . Tripwire should be initialized immediately after system installation and configuration while still in single-user mode and not connected to an external network. you will need to put the database back in /usr/adm/tcheck/databases/. This makes it much easier to spot suspicious activities called out within the report.5 When should Tripwire be run Ideally. examining the report.4 Comments on configuration A good deal of thought and planning need to go into the creation of the Tripwire configuration file (tw.[/usr/adm/tcheck]# /usr/security/bin/tripwire ### Phase 1: Reading configuration file ### Phase 2: Generating file list ### Phase 3: Creating file information database ### Phase 4: Searching for inconsistencies ### ### Total files scanned: ### Files added: ### Files deleted: ### Files changed: ### ### After applying rules: ### Changes discarded: ### Changes remaining: ### 6667 0 0 6010 6010 0 9. the database. To run Tripwire again.1. 7. rather than assuming they will be picked up by a directory specification. Important system files should be explicitly called out in the tw. on read-only media.config file. Be sure to safely store the configuration file. such as /sbin or /usr/sbin. the configuration file. The strength of Tripwire depends solely on the integrity of these files. such as on another secure machine. store the database.config). Once the Tripwire database has been successfully initialized. 7. modifying the configuration file.1. Be forewarned that this is an iterative process. and the executable program after each iteration. The goal is to minimize the Tripwire report of changed files to only those that change because of normal day-to-day activities. It takes some time to refine it into a tool that works well in your environment. You need to spend time running Tripwire. and running Tripwire again.
Here are some guidelines taken from the AIX 4. SG24-5962.3 Elements of Security redbook: • Do not use your user ID or any permutation of it. Also. see Chapter 7 of Exploiting RS/6000 SP Security: Keeping it safe. 7. For more information about TCB. Weak passwords are one of the most common ways in which attackers gain unauthorized access to systems.Run Tripwire periodically to ensure that no unauthorized changes have been made to important system files or directories. Having John the Ripper proactively scan the password file is one way to ensure that passwords are sufficiently strong.2 John the Ripper John the Ripper is a tool for password cracking. run it just before and just after any changes to the system for things. APARs.1. not the least of which is that it can only be enabled during AIX installation (not after). Never use the same root password on multiple systems. For details on COPS and Tamu's Tiger.3 Elements of Security Effective and Efficient Implementation. especially for a networked or larger multi-user system. • Do not use words that can be found in the online spelling-check dictionary. As always. This is one of the most insidious forms of attack. • Do not use any person's name. • If you use the same password on more than one system. Your first step in ensuring strong passwords is to educate the users of your system on what constitutes a strong password. and so on. be extra careful with it. Chapter 7.6 Alternatives to Tripwire Other alternatives to Tripwire are: • Trusted Computing Base (TCB) • COPS • Tamu's Tiger Trusted Computing Base (TCB) is a feature that comes with AIX. There are a number of drawbacks with TCB. because it is very difficult to differentiate between a valid user and an attacker who has purloined a valid user's password. System and data integrity 119 . • Do not use passwords shorter than five or six characters. PTFs. new software installs. 7. such as operating system upgrades. be sure to secure the modified copies of the Tripwire configuration file and database. SG24-5521. see Chapter 6 of AIX 4.
Do not write down your password. Inflate the package. but many of them still require good education and ongoing enforcement. • Two words. • AIX checks only the first eight characters of the password. Refer to Section 7. however the word can be longer than eight characters. John the Ripper is a very good tool to help you with the enforcement piece. with a numeric digit inserted in the word.2. these are among the first words tried when guessing passwords. • A word (with at least six characters).com/john/. You can download the tool from this site in source-code format.1. make a good password.1 Obtaining and installing John the Ripper The main site for of John the Ripper is http://www. Download the package and ensure that it has not been tampered with before installing it. • A good scheme is to memorize a sentence and use the first letter of each word for the password. But do not form the digit by changing an "l" to "1" or an "o" to "0. Note that some of these guidelines can be enforced through facilities provided by AIX. "Ensuring the integrity of downloads" on page 136 for more information on how to do this.6 from the Bull site. with a number in between.4. • Do use passwords that you can type quickly. and install it (via installp or SMIT): 120 Additional Security Tools for AIX Systems . "the cat sat on the mat" = tcsotm. 7. • Do use passwords that you can remember. • Do consider passwords that consist of letters and numbers." A word with an internal digit is a better password than a word with a leading or trailing digit.• Do not use swear words or obscene words. • A pronounceable password is easier to remember. or can download it in installp format from the Bull site. The version that we used for this redbook was version 1.openwall. is an excellent password. For example.
Important Many organizations have very strict policies against unauthorized use of tools like John the Ripper. Make sure you have the proper written authorization in place before running this tool. System and data integrity 121 .0.john. It uses the login/GECOS information from the /etc/password file as input. For example.john. It is a rather short list./john-1.32 of 3 November 1997.6/password.rte 1.0 USR APPLY SUCCESS # lslpp -l freeware. by Info-ZIP (firstname.lastname@example.com. A wordlist file (/usr/local/bin/john-1.lst) is provided with the package.rte Installation Summary -------------------Name Level Part Event Result ------------------------------------------------------------------------------freeware.0.wku.0 COMMITTED John the Ripper Password Cracker Once the fileset has successfully been installed.6.0. freeware. 7.0.2 Configuring John the Ripper There are three modes that John the Ripper uses to crack passwords: • Single Crack • Wordlist • Incremental The Single Crack mode is the fastest.bff # installp -acgX -d . you can merge it with the /usr/share/dict/words file from the bos.0.6.6.john. The Wordlist mode takes as input a file containing one word per line.data fileset (found on the AIX Installation CD).# ls -l total 1048 -rwx------ 1 root system 535904 Sep 12 09:54 john-1.rte Fileset Level State Description ---------------------------------------------------------------------------Path: /usr/lib/objrepos freeware. change the ownership and permissions on the executable (/usr/local/bin/john) such that root is the only one allowed to run it.6.6.rte 1.2.edu). as follows: Chapter 7.exe UnZipSFX 5.exe # .0. inflating: john-1. so you should augment it with additional words.0.
John the Ripper requires that the password file be a single file. You can set parameters in the $JOHNDIR/john. you can manually merge the contents of the two files by replacing the "|" mark in the /etc/passwd file with the encrypted password in the /etc/security/passwd file.sort Once merged. Use the egrep command to filter out the users you do not 122 Additional Security Tools for AIX Systems .ini file to control this mode of operation and turn it into something more realistic and practical.2.list./shadmgr. Since AIX implements a shadow password file.zix > /tmp/password # chmod 600 /tmp/password . because of the length of time it needs to do this.list.3 Using John the Ripper Important As has already been mentioned.ini configuration file to reflect the new filename (/usr/local/lib/john-1. "Script to merge the AIX passwd files" on page 209 provides a listing of the shadmrg. you need to merge the /etc/passwd and /etc/security/passwd files into a single file.aix | egrep -v "useridA|useridB|useridC" > /tmp/password # chmod 600 /tmp/password This command runs the shadmgr. It uses all possible character combinations to ultimately crack all passwords.aix script to create the merged password file (/tmp/password).6 #cp /usr/share/dict/words $JOHNDIR #cat $JOHNDIR/password. 7.OR # . (Alternatively. it is generally not practical to have it run this way without modification.sort).): # .lst >> $JOHNDIR/words #/usr/bin/tr A-Z a-z < $JOHNDIR/words | \ sort -u > $JOHNDIR/words. edit the Wordfile entry in the john.#export JOHNDIR=/usr/local/lib/john-1. ensure that you have the necessary written authorization in place before attempting to use John the Ripper./shadmgr. Appendix C.aix script (obtained from the Crack package) to merge these two files. The Incremental mode is the most powerful.6/words. However.
John the Ripper uses the three modes (Single Crack. and re-run John the Ripper to see what happens: Chapter 7. System and data integrity 123 . Also. Now. and Incremental. Successful attempts are sent to the screen and saved in the $JOHNDIR/john. If you want to see them again. Important After installation. be sure to change the file permissions for the /tmp/password file so that only root has access to it. change the file permissions of the John the Ripper executable (/usr/local/bin/john) so that only root has access to it. Wordlist. The same goes for the merged password file (/tmp/password). Run John the Ripper as follows: # /usr/local/bin/john /tmp/password By default. respectively) to attempt to crack the passwords.meter1 The passwords for root (password rootroot) and khorck (password merlin1) are cracked in 3 seconds. re-run John the Ripper with the -show option: # /usr/local/bin/john -show /tmp/password Here is an example that illustrates the difference in time it takes to crack a password with a digit on the end versus one with a digit in the middle: # /usr/local/bin/john /tmp/password Loaded 2 passwords with 2 different salts (Standard DES [32/32 BS]) rootroot merlin1 (root) (khorck) guesses: 2 time: 0:00:00:03 100% (2) c/s: 22715 trying: menu1 . lets change khorck's password from merlin1 to merl1n.want to scan.pot file.
files encrypted with the public key 124 Additional Security Tools for AIX Systems .# /usr/local/bin/john /tmp/password Loaded 2 passwords with 2 different salts (Standard DES [32/32 BS]) rootroot merl1n (root) (khorck) guesses: 2 time: 0:00:28:24 100% (3) c/s: 23710 trying: Booms2 . "Key concepts of SSH" on page 62). and Outlook Express. such as secondary authentication or two-person login. ftp. This security is achieved by strong encryption and authentication. In a nutshell. rather than on either end.org/doc/faq/pgpi/en/#International 7. "Secure remote access" on page 59.3 Elements of Security Effective and Efficient Implementation. Linux. see the PGP FAQ at: http://www. This illustrates that having numbers in the middle of passwords. It runs on various operating systems. including UNIX. even the strongest password is vulnerable to network sniffing with protocols. SG24-5962. 7.5 minutes to crack the new khorck password. and so on.1.3 Pretty Good Privacy (PGP) PGP is a popular tool used to communicate between two parties securely. such as telnet.hilsuh Notice that Jack the Ripper now took 28. However.1 PGP basics PGP is based on public key cryptography (see Section 5. Note A strong password is a good defense against brute force cracking methods. Refer to Chapter 5. makes them significantly harder to crack. For more information about supported configurations. For more information. such as Lotus Notes.pgpi. rsh. for ways to protect against this type of attack. Eudora. refer to AIX 4. and Windows. Additional methods. and it has plug-ins available for email programs. PGP is a de facto standard used in email to quickly and easily enable secure communications.3. are available to make authentication more difficult to crack.3.
With PGP. Here is how PGP does it: 1. It also supports either DSS/DH keys or RSA (IDEA only) keys. Once encrypted. It is for this reason that PGP uses a hybrid of both symmetric and asymmetric cryptography. By definition. The private key is "private" and should be kept secure and private. In this case. messages are encrypted using conventional symmetric cryptography (the same key is used to encrypt and decrypt the message). a public key is "public" and can be freely distributed to the other individuals you want to communicate with using PGP. Jack wants to communicate securely with Jill using PGP. From now on. Straight public-key encryption is much slower (sometimes by as much as a factor of 1000) than conventional single-key encryption (symmetric cryptography). and IDEA. The private key can be further protected with the use of a pass phrase. With this hybrid method. Jack and Jill will just use the session key to encrypt and decrypt the data flowing back and forth between them. this key is a random one-time key (session key) that is used for this session only. then uses Jill's public key to encrypt the session key (asymmetric cryptography). the symmetric algorithm used to encrypt the data itself and the asymmetric algorithm used to securely transfer the encryption key. PGP overcomes this weakness by using asymmetric cryptography. Now. 3. A comparison of each can be found in the PGP man pages ( man pgp-intro).(asymmetric cryptography) can only be decrypted by the matching private key and vice-versa. both symmetric and asymmetric algorithms are used. Jill sends Jack her public key. 2. However. Jack encrypts the data with the session key (symmetric cryptography). Chapter 7. the main weakness of symmetric cryptography is in how to share the same key securely. 4. both speed and security are achieved. PGP supports three symmetric ciphers: CAST (default). System and data integrity 125 . Jack sends both the session key and the data to Jill. Jill uses her private key to decrypt the session key (asymmetric cryptography) and then uses the session key to decrypt the data (symmetric cryptography). Triple DES. 5.
the author of the message is verified because the message was signed with the private key of the sender (thus the importance of protecting the private key).PGP also uses digital signatures for message authentication.4. Digital signatures serve the same function as that of real signatures. PGP is available in both commercial and non-commercial packages. Download the package and ensure that it has not been tampered with before installing it.pgp.2 Obtaining and installing PGP PGP was created by Phil Zimmermann and is available from Network Associates (http://www. The digital signature is sent together with the message. Both must be the same to ensure data integrity.0 from the Bull site. but in the digital world. see the PGP man pages (man pgp-intro). Inflate the package. PGP is available for download in source-code form from the PGP International site (http://www. ranging from firewalls to intrusion detection software to consultancy services.3. 7.com (US or Canada only) or from http://www. Refer to Section 7.1.bull. Network Associates has a host of other security-related products.com (everywhere else). Then.pgpi. the recipient uses the sender's public key to decrypt and obtain the message digest.pgpinternational. the recipient executes a one-way hash function on the message to obtain a message digest and compares this output with that sent by the sender (the output decrypted with the senders' public key). A digital signature is created by encrypting the message digest (a strong one-way hash function of the message) with the sender's private key.com).fr. for more information on how to do this. install it (via installp or SMIT). To verify the digital signature. The version we used for this redbook was version 5. For more information on this process.com). At the same time. PGP is also available in installp format from http://www-frec. See the Network Associates site for more details on the licensing agreements. Commercial licenses are available from http://www. and verify that it is successfully installed: 126 Additional Security Tools for AIX Systems .nai. In addition to PGP. "Ensuring the integrity of downloads" on page 136.
0.wku.exe UnZipSFX 5. inflating: pgp-5. Like SSH.31 of 31 May 1997.bff -rwx-----.exe # rm . Generate your public-private key pair with the pgpk -g command: Chapter 7.rte 5.0.1 root system 4403200 Mar 06 1998 pgp-5.toc # installp -acgX -d .0.0 COMMITTED Pretty Good Pricacy E-mail system You may also want to update the MANPATH environment variable to include /usr/local/man and the PATH environment variable to include /usr/local/bin in /etc/profile.pgp.0. Installation Summary -------------------Name Level Part Event Result ------------------------------------------------------------------------------freeware.rte .0.0 USR APPLY SUCCESS # lslpp -l freeware. Each user will have their own set of key files and configuration files.3 Using PGP The first step to using PGP is to generate a public-private key pair.0.0.toc # ls -l total 11776 -rw-r--r-. by Info-ZIP (firstname.lastname@example.com # rm .0.0.pgp./pgp-5.0..edu).0. freeware.3.0. not just root.pgp.0.rte 5. System and data integrity 127 .# .0.pgp..0. 7.1 root system 1622544 Aug 24 14:49 pgp-5. PGP can be used by anyone.rte Fileset Level State Description ---------------------------------------------------------------------------Path: /usr/lib/objrepos freeware.
Archival grade.............. 2..1 root system 512 Sep 05 11:53 randseed.complete....1 root system 0 Sep 05 11:50 secring. Please enter some random text on your keyboard until you hear the beep: 0 * -Enough..1 root system 889 Sep 05 11:51 pubring.pgp # ls -l total 24 -rw------. Read the user's guide for more information) 1) 768/768 bits. slow....pgp /.bak -rw------........com> If you violate this standard.. If you wish to send this new key to a server. Enter pass phrase: Enter again.....pgp."Military" grade..... secure for forseeable future(default) 4) 3072/1024 bits.bak -rw------.... you will lose much of the benefits of PGP 5. thank you... followed by your E-mail address enclosed in <angle brackets>.0 (default) 2) RSA Choose 1 or 2: 1 Pick your public/private keypair key size: (Sizes are Diffie-Hellman/DSS.... We need to generate 571 random bits.... spaces.... below..........ibm.... 3 or 4../ # pgpk -g Creating /....... For example: Joe Smith <user@domain. .... secure for many years 3) 2048/1024 bits.....******* '[o..com> Enter the validity period of your key in days from 0 ...... enter nothing...0's keyserver and email integration.. probably not currently breakable 2) 1024/1024 bits. highest security Choose 1...... Your pass phrase can be any sentence or phrase and may have many words.4096): 2 You need a user ID for your public key.skr 128 Additional Security Tools for AIX Systems .........New algorithm for 5..... If not.........1 root system 0 Sep 05 11:50 pubring.999 0 is forever (and the default): You need a pass phrase to protect your private key(s)......pkr -rw-r--r-.cfg Choose the type of your public key: 1) DSS/Diffie-Hellman ..alibaba.. The desired form for this user ID is your FULL name.... enter the URL of the server.. No randseed file found.. Enter a user ID for your public key: root <root@arthur.......******* . / # cd ... . punctuation... if you have an E-mail address......... or enter desired number of Diffie-Hellman bits (768 ..... or any other printable characters.. Cannot open configuration file /. This is done by measuring the time intervals between your keystrokes..High commercial grade.bin -rw------...1 root system 976 Sep 05 11:51 secring...******* ....Commercial grade.******* Keypair created successfully....... for confirmation: Enter pass phrase: Collecting randomness for key.pgp/pgp....
pgp/pgp. These are the default names and locations for these files. and you can use the pgpk -x <userid> command to extract your public key to a file for distribution: /. root's public key is extracted to a file named publickeyfile.cfg Type Bits KeyID Created Expires Algorithm Use sec+ 1024 0x0592C6DE 2000-09-05 ---------.cfg /.pgp/secring. respectively.pgp # pgpk -l Cannot open configuration file /.DSS Sign & Encrypt sub 1025 0x76580B38 2000-09-05 ---------.0i for non-commercial use mQGiBDm1FoQRBAD8KcZ/FCH+QtQQRauJpBHLK2Ciwve1D7Zts8zqhsiGz+ywZxib Lmsg1opAW1w/IzpMLET0g4JhSSNnAi1H02KmBKrNCY4b2gB3UCX0bIxahamyTKU1 aDSFwthos5+PLbKSDB1WjVohLSei1W1uPWSrO6B7sM0fOl+K0pYx8HrCEwCg/+aO SDTzQp+BM2kBTYM6CKgbThMEAM+eE70adaiAm50KZRefSThuDgbvWpYkCZZs+i0X L5KBRsnw26z1MF8xFPw+KTf8N+TGn6td+qOxL1b5x2jOxoHA1Y2yp0yG6ExJfxN7 Ni6YcVrUHQbPbsOE9cJTlXgsugbwACQRtq0F/LkFquXOlBguA1tiPH4FC87QEA0u AuTLBADBrviGRVzVtsvYcb1hKBY4bRnEZwswvIhc0s7l0ZJGi54zH5RgvwTmsmd4 OgPBwZSaAuoaI5j3U4nHbihJE4le/sWS+FO7Bgy6dFZ8qK/e5ibmB2nW29N6R9ZN +E2KkWr7JNzbJNlvJAorJIYIyQgO9qfMXEKekGmLXCMk2r1Cv7Qicm9vdCA8cm9v dEBhcnRodXIuYWxpYmFiYS5pYm0uY29tPokASwQQEQIACwUCObUWhAQLAwECAAoJ EHOk2qQFksbeL8wAoO1E50QLVmdpEFGCC3MUsSzLbZ0SAJ9TWFX0a4V9qIbHKYWu tP+813BqnrkBDgQ5tRaREAQBAQEYVycxln++/zRqA2eQoNr4IrrHluZvHwyhhINo 6cCy+oANKzUjmXJajGIMCwT6wbO+koVSa8kYPzlSG5QpdEE9+2XjJaaB/csBMvN8 jvOjBBXrnGjEfAIwosAU1cvvmLwJPhGvh00cSbSX9ELj/iD0hqXABW6SlpdnRoRa ARlPAAICA/98YOZxJl87uGlxdKhn4PDdECtEdMOqVE1oq3pECtQQgLa8WYZmfiir EPGvT7eBG1O1at2FrSDT0ac+Fd0LAAbRCw/0XRibPIoMbYE3ENUrX16tuCOQtT6G EXRe2OxLS2wKcG/QyXyPH3TbF9gH/IyKqxUnCsfI552Xcda4WjgF64kAPwMFGDm1 FpFzpNqkBZLG3hECWDYAoLco/XRRLjAlqKQR9yUQsyAdwCcZAKCwXGoKTfAuuYuZ DGnXLJJxybmxEA== =hX2t In this example.Diffie-Hellman uid root <firstname.lastname@example.com file and the $HOME/.The important files to note are the $HOME/.ibm.pgp/pubring. System and data integrity 129 . you can: Chapter 7.pgp # pgpk -x root > publickeyfile Cannot open configuration file /. You can view the contents of your keyring using the pgpk -l command.alibaba.pgp/pgp. which contain the public and private keyrings. but you can configure PGP to use different names and locations if desired.skr file. To distribute the public key.pgp # more publickeyfile -----BEGIN PGP PUBLIC KEY BLOCK----Version: PGPfreeware 5. The publickeyfile can then be distributed to other users with whom you need to communicate securely.com> 1 matching key found /.
com> 2 matching keys found You can use the pgpk -ll command to obtain detailed information of the keys on your keyring. use the pgpk -a command: # pgpk -a /home/khorck/. You can use this information to verify with the key owner (by phone or other means) that you are using the correct version of their public key: 130 Additional Security Tools for AIX Systems . and send it to those who need it.alibaba. /.pgp/pgp.asc' KeyID Created Expires Algorithm Use 0xF409CB5B 2000-09-05 ---------. the KeyID. To add a public key (khor.asc Cannot open configuration file /. The important information is the key length.pgp # pgpk -l Cannot open configuration file /. • Distribute the public key through a public key server (details available in the PGP man pages).• Make the file to which you extracted the public key available to those who need it.Diffie-Hellman uid root <firstname.lastname@example.com Sign & Encrypt sub 1025 0x76580B38 2000-09-05 ---------.Diffie-Hellman chune keat 1 matching key found Add these keys to your keyring? [Y/n] y Keys added successfully.DSS Sign & Encrypt sub 1024 0xDC8183A1 2000-09-05 ---------.DSS Sign & Encrypt 0xDC8183A1 2000-09-05 ---------.Diffie-Hellman uid khor chune keat sec+ 1024 0x0592C6DE 2000-09-05 ---------.pgp/khor.cfg Type Bits KeyID Created Expires Algorithm Use pub 1024 0xF409CB5B 2000-09-05 ---------. and the Fingerprint. • Include the public key as attached text within an email message.asc in this case) to your keyring.cfg Adding keys: Key ring: Type Bits pub 1024 sub 1024 uid khor '/home/khorck/.pgp/khor.ibm.pgp/pgp.
pgp/pgp.Diffie-Hellman uid khor chune keat SIG! 0xF409CB5B 2000-09-05 khor chune keat pub 1024 0x0592C6DE 2000-09-05 ---------.alibaba.Diffie-Hellman f20 Fingerprint20 = 83E2 8BC0 991F AC40 FB0E BE10 4183 8C47 7658 0B38 uid root <email@example.com Sign & Encrypt sub 1024 0xDC8183A1 2000-09-05 ---------.alibaba. System and data integrity 131 .ibm.Diffie-Hellman uid root <firstname.lastname@example.com Type Bits KeyID Created Expires Algorithm Use sec+ 1024 0xF409CB5B 2000-09-05 ---------.DSS Sign & Encrypt sub 1025 0x76580B38 2000-09-05 ---------.ibm.Diffie-Hellman f20 Fingerprint20 = 135C F183 BFC8 2B1A C9CC 9BB8 618C uid khor chune keat sig 0xF409CB5B 2000-09-05 khor chune keat Use Sign & Encrypt 2B3B F409 CB5B 33E1 DC81 83A1 sec+ 1024 0x0592C6DE 2000-09-05 ---------.ibm.com> SIG 0x0592C6DE 2000-09-05 root <root@arthur. That simply means that the public key that you imported for root did not come from a trusted source.DSS f20 Fingerprint20 = 2334 815A FC8B ABEC 4AEF 8D3C 5284 sub 1024 0xDC8183A1 2000-09-05 ---------. Chapter 7. it is a very good idea to use the pgpk -ll command and verify the key length.pgp/pgp.ibm.com> Notice that the Trust value for root's public key is untrusted.alibaba.com> sig! 0x0592C6DE 2000-09-05 root <firstname.lastname@example.com.# pgpk -ll Cannot open configuration file /.ibm.com> KeyID Trust Validity User * 0xF409CB5B ultimate complete khor khor 0x0592C6DE untrusted invalid root root ID chune keat chune keat <firstname.lastname@example.com Sign & Encrypt f20 Fingerprint20 = A594 B67E 5DFA BBEC 9FDE A59A 73A4 DAA4 0592 C6DE sub 1025 0x76580B38 2000-09-05 ---------.com> 2 matching keys found You can display even more information about the keys in your keyring (such as Trust level) with the pgpk -c command: $ pgpk -c Cannot open configuration file /home/khorck/.ibm.com> <root@arthur. When this is the case. KeyID.cfg Type Bits KeyID Created Expires Algorithm pub 1024 0xF409CB5B 2000-09-05 ---------. and Fingerprint with the public key owner to ensure that you have the correct key.alibaba. such as a Certificate Authority.
Once both parties have each other's public keys. Key ID 0592C6DE.asc output file is automatically created. then reverses the process to send the reply. Note that signing and encrypting are independent events.ibm. the pgpe -r "recipient name" -sat /tmp/secretfile command encrypts and signs (-s flag) the /tmp/secretfile file.cfg A private key is required to make a signature. To encrypt a file. PGP then uses the corresponding public key to encrypt the file: # pgpe -r "khor chune keat" -sat /tmp/secretfile Cannot open configuration file /.pgp/pgp. they can communicate securely using PGP: • The sender encrypts the message with the receiver's public key. The warning message simply means that the public key was not obtained from a trusted source. such as a Certificate Authority. Created 2000-09-05 "khor chune keat" WARNING: The above key is not trusted to belong to: khor chune keat Do you want to use the key with this name? [y/N] y Creating output file /tmp/secretfile. Since the message is signed with your private key. Key ID F409CB5B.asc In this case. 1024 bits. The /tmp/secretfile. they can decrypt it with the pgpv command: 132 Additional Security Tools for AIX Systems . then sends the message. you need to know the recipient's name. Need a pass phrase to decrypt private key: 1024 bits. • The receiver uses their private key to decrypt the message. Created 2000-09-05 "root <root@arthur. Once the recipient receives the encrypted file. (Use the pgps command if you want to sign a file).alibaba. you also need to enter the pass phrase. The -at flags cause the output of the command to be in text format for portability between different operating systems. This file contains the encrypted contents which you send to the recipient. you can sign a file without encrypting it. so. and you can encrypt a file without signing it.com>" Enter pass phrase: Pass phrase is good.
PGP can also be used to encrypt sensitive files for secure storage (locally or remotely). PGP is widely used on the Internet to provide assurance (through digital signatures) that downloadable files have not been tampered with.ibm. encrypted /tmp/secretfile.ibm.asc Chapter 7. Created 2000-09-05 "root <root@arthur. Key ID 0592C6DE. Notice also the Good signature line.asc Cannot open configuration file /home/khorck/. Key ID 0592C6DE. The warning message simply means that the public key was not obtained from a trusted source. Need a pass phrase to decrypt private key: 1024 bits.alibaba.alibaba. which is very important for ensuring the integrity of the message. Created 2000-09-05 "root <email@example.com/pgp.pgp/pgp.asc # rm /tmp/secretfile Note that there is no reason to save the /tmp/secretfile file since what you really wanted was the signed.com> Notice the prompt for the pass phrase. Need a pass phrase to decrypt private key: 1024 bits. Good signature made 2000-09-05 18:15 GMT by key: 1024 bits. System and data integrity 133 .ibm.com>" Creating output file /tmp/secretfile. packages from the Bull site often include a file with a . Because the file was encrypted with the recipient's public key.$ pgpv /tmp/secretfile. Created 2000-09-05 "root <root@arthur. Key ID 0592C6DE. To use PGP to encrypt a file for yourself. Opening file "/tmp/aaa" type text.cfg Message is encrypted.com>" WARNING: The signing key is not trusted to belong to: root <root@arthur. and use of the private key requires a pass phrase.asc file.cfg A private key is required to make a signature. it must be decrypted with their private key.ibm.alibaba. 1024 bits. such as a Certificate Authority. Key ID DC8183A1. simply encrypt it with you as the designated recipient: # pgpe -r "root" -sat /tmp/secretfile Cannot open configuration file /.alibaba.com>" Enter pass phrase: Pass phrase is good. For example. Created 2000-09-05 Enter pass phrase: Pass phrase is good.
private keys are the key to security within PGP (and all public-private key encryption schemes. "Ensuring the integrity of downloads" on page 136. A detailed description of MD5 can be found in RFC 1321. Recall that a hash function takes an input of arbitrary length and produces an output of fixed length. In the case of the Bull site. for that matter).purdue. and have meaning only for you. It is one way because you cannot reproduce the original input if given the hashed output. 7.4.bff) are included together in the same package. Read this file for further instructions on how to verify the integrity of the download prior to installation of the fileset(s). the signature file (.extension. run the pgpv command against the signature file (. or just the signature without the message. 134 Additional Security Tools for AIX Systems . 7.bff). known as the MD5 checksum. we used version 4. you need to have the message file available (through a separate download) for PGP to be able to verify the signature. Additional information on ensuring the integrity of downloads can be found in Section 7. Most Internet sites provide the signature and message in separate files.4 Protecting your private key As you can see.edu/pub/tools/unix/crypto/md5/ The site also contains a digital signature so that you can verify the integrity of the package. It is a strong. one-way hash function . The MD5 package is available in source-code form from Purdue University: ftp://ftp. obtain the public key of the file's creator and add it to your keyring.asc) and the message file (. but the signature file does not contain the message file. The PGP man pages ( man pgp-intro) contain additional suggestions on ways to protect your keys.3. then.4 of the C compiler for AIX under AIX 4. which is included in the package. Pass phrases should be 10-30 characters in length.4 MD5 MD5 is a tool used to produce a unique checksum. you will need access to a C compiler. In our case. To verify the message file (.cerias. Just as important as the physical security of your private key is the choice of a good pass phrase. In the latter case.1.3. A downloaded signature file can contain the signature and the message in a single file.asc) to verify the integrity of the download.3. extremely difficult to guess. Any change to the input will result in a totally different output (though of the same length). first. Private keys must be kept private and secure at all times. In addition to the package.
and only move the executable program to the production system.h. x rfc1321./md5 nmap-2. 10423 bytes. it is not a good idea to have a C compiler loaded on a production system. 4 media blocks. System and data integrity 135 .bff file: # .Important For security reasons. x md5.53. Also. x md5. x md5. x global. x mddriver.bff) = 449244ff27fc11be06864ac6b0e8bb44 Chapter 7.0.tar.1 root system 35287 Sep 10 20:41 MD5. Compile the program on a non-production system.Z # uncompress MD5.1.53.. Once the make has successfully completed.0. 17 media blocks. MD5 is ready for use. compile.txt # vi Makefile . be sure to set the permissions as tightly as possible.ps mddriver.c cc -c -O -DMD=5 mddriver. 1350 bytes. CC = cc .tar md5-announcement.0.c README md5. 1644 bytes. 3 media blocks. 1503 bytes. x md5. # make md5 cc -c -O -DMD=5 md5c. 1288 bytes. 35223 bytes. 4 media blocks.1. 781 bytes.53.c.bff MD5 (nmap-2.tar x Makefile.tar.1.1 md5c.0. 5354 bytes. 8572 bytes.o mddriver. 21 media blocks. 3 media blocks.1.ps.. 11 media blocks.h. 69 media blocks. 1898 bytes.0..c. 3 media blocks.h md5. x md5-announcement. For example.txt.txt md5. # ls MD5.txt rfc1321.txt. Unpack.1. 11 media blocks. to compute the MD5 checksum on the nmap-2.o # Notice that we modified the Makefile to reflect the fact that we were using cc (AIX C compiler) rather than gcc (GNU C compiler).h Makefile md5.c cc -o md5 md5c. and install the package as follows: # ls -l total 72 -rw-r----. 2 media blocks.. x md5c. x README.Z # tar -xvf MD5.c global.0. 5568 bytes.txt.
53_0_0./nmap-2_53_0_0.net>" WARNING: The signing key is not trusted to belong to: Ciaran Deignan <ciaran. When that is the case.1 Ensuring the integrity of downloads Before downloading anything from the Internet.bff. inflating: nmap-2.asc (digital signature) file along with the installable nmap-2.4. 7. you know that what you downloaded matches what was put on the site. If they are not.0.bff]: Good signature made 2000-07-24 15:32 GMT by key: 1024 bits.0.53.0.0. you need to download the public key of the author and run the pgpv command against the nmap-2. Created 1999-03-15 "Ciaran Deignan <ciaran.53. delete the file(s).0. # . execute the MD5 checksum on the downloaded files. however. you will need to download each of the files separately.0. and notify the site owner.edu). MD5 is but one of a number of available checksum tools. Key ID 22F02AED.53. An example package that contains a digital signature is the nmap-2.32 of 3 November 1997. you will find an nmap-2.When downloading files from the Internet.53.exe UnZipSFX 5.bff Cannot open configuration file /. If you do.pgp/pgp.0. Some sites will include a digital signature from the author for your verification. by Info-ZIP (Zip-Bugs@lists. This signature applies to another message File to check signature against [nmap-2. and then verify the MD5 checksums with the MD5 checksums published on the Web site.0. For additional instructions. For example.asc # pgpv nmap-2.bff file.wku.deignan@bull. Once you inflate this package. A good signature indicates that the package has not been tampered with.asc email@example.com. MD5 is also a good tool to use when sending files to a remote location across the network.asc -o nmap-2. you next need to ensure that the copy of the file(s) you download match the original version of the file(s) placed on the site by the owner.53_0_0. depending on what is available from the site. There are several ways you can do this. you first need to decide if you trust the site.bff. 136 Additional Security Tools for AIX Systems .53_0_0. It is.53.exe package. If the checksums are identical.cfg Opening file "/dev/null" type text.53_0_0.0.bff inflating: nmap-2. see the . the Bull site includes digital signatures for some of its filesets. To verify the signature. also one of the most popular and widely-used ones.asc file.net> Some sites may not have all these files packaged together.
Other sites may not use PGP signatures at all. Instead, they publish the MD5 checksums for their downloadable files. Once you have downloaded the file(s), you use MD5 to generate the checksum(s), and then compare your results with those published on the site. If they are different, delete the file(s) and notify the owner of the site. Finally, some sites just post information about the security measures in place on their site. After reviewing this information, you can decide whether or not you feel comfortable proceeding with the download.
Chapter 7. System and data integrity
Additional Security Tools for AIX Systems
Chapter 8. Securing AIX
Once AIX is installed on a server, there are a number of additional configuration changes that you can make to further tighten down security on the box. This chapter illustrates how to turn off unnecessary services and modify the configuration of the remaining services to make them even more secure. AIX supports a multitude of applications (each with their own unique requirements) in any number of conceivable environments making it impossible to create a single, default security environment that applies to all. Thus, the security level you set up in AIX needs to be tailored to the customer and application environment where the server is deployed. For example, an Internet Web server will most likely have different security requirements than a software development server located in a lab. A common entry point for attackers is through vulnerabilities in network services. New exploits are discovered almost daily; so, what is secure today may not be secure tomorrow. The best rule of thumb is to turn off all services that are not needed. The best time to do this is before the server is in production. Begin by turning off as much as possible. If in doubt, turn it off. Then, selectively turn services back on only when there is proof that they are needed. It is far easier to turn on what is needed before going into production than it is to try and figure out what can be turned off once the server is live. You can then focus your security efforts toward making configuration changes and applying the latest security patches on the remaining services. To secure a building, all entry points around the perimeter must be secure. The same holds true for securing a server. Take, for example, a Web server. Among other things, this server consists of the network, the operating system, and the Web server software (application). If you focus only on securing the Web server software piece, you leave the operating system and the network doors vulnerable. An entry gained through any door is an entry gained. For example, suppose the attacker takes advantage of an rpc.statd vulnerability to gain root access. At that point, the battle is lost. Not only has the OS been compromised, but everything else along with it. Worse yet, suppose that rpc.statd was a service not required for the proper functioning of the server. Unneeded doors should be removed and bricked over, and the remaining doors should be reinforced with the strongest materials at your disposal. Securing AIX is not a one-time process. Even though you have taken steps to turn off unnecessary services and protect the remaining ones, you still need to maintain constant vigilance. New exploits are being invented almost daily, and changes to the system, such as software upgrades, potentially open new
© Copyright IBM Corp. 2000
holes. Apply security fixes to your system as soon as it is practicable, and strive to know the normal behavior of the system so that you can easily spot anomalies if they occur.
8.1 Overview
As mentioned earlier, there are two types of attackers: Those who are on the inside and those who are on the outside. Both can cause harm, but they each have slightly different profiles in the way they attack. For example, internal attackers may already have legitimate user accounts on the systems. In general, they do not, typically, have root access. However, having a normal, non-privileged account still gives them the freedom to snoop around looking for possible configuration errors and system vulnerabilities. External attackers need to spend more time doing reconnaissance against their potential targets. For example, using tools, such as nmap (with the -O flag), external attackers attempt to find out which operating system runs on their target. They then use tools, such as SAINT or nmap, to attempt to determine which network service ports are open. With this information in hand, they next use a tool, such as netcat (nc) , to attempt to grab banner information to determine which version of the service is running on each port. If the attacker finds that you are running a certain version of a service, and there are known problems with this level of code, the attacker can then use known attack methods to penetrate the system. The importance of keeping your systems up-to-date with the latest security patches and configuring your systems to not leak any unnecessary information cannot be understated. One has simply to look at recent news headlines to understand that the threat is very real and that the reputation of the organization may very well hinge on the security of the systems you have been entrusted to protect. The general steps to harden AIX (which are explained in detail in the remainder of this chapter) are as follows: 1. Remove unnecessary services. 2. Tighten configurations of remaining services. 3. Set proper network (no) options. 4. Tighten up user accounts. 5. Set up a strong password policy. 6. Install additional security tools (such as the ones mentioned in previous chapters).
Additional Security Tools for AIX Systems
7. Monitor logs, audit trails, and system behavior.
Prior to making any change to a production system, be certain that you have a known-good backup just in case the change does not work the way you expect. In the examples that follow, we assume a newly-installed system. Our environment (AIX 4.3.3 on an RS/6000 F50) is meant to simply illustrate what is possible. Your environment is almost certainly different and more complex; so, you will need to take this information and tailor it to your unique needs.
Many organizations have very strict policies in place against running certain types of tools, such as sniffers and scanners, on a production network. Make sure you have the proper written authorization in place prior to running any of these tools on your systems.
8.2 Step 1: Remove unnecessary services
You can see which services have active listening ports on your system with the netstat -af inet command. Alternatively, you can do this with scanning tools, such as NSA, SAINT, or nmap. The advantage to using scanning tools are threefold: • You can run them against a multitude of servers from a single location. With netstat, you need to run it on a server-by-server basis. • Tools, such as NSA (Section 4.4, "Network Security Auditor (NSA)" on page 49) and SAINT (Section 6.3, "Security Administrator's Integrated Network Tool (SAINT)" on page 94), have a list of known vulnerabilities that they use to test against. • Attackers use similar tools to scan your network. By knowing what they know and seeing what they see, you can devise strategies to defend against such scans and minimize the amount of information that is available to would-be attackers. The less information they have to work with, the harder it is to penetrate your network.
Chapter 8. Securing AIX
The /etc/inittab file varies from system to system depending on the applications that are installed on the server. It is also possible to permanently remove a service by uninstalling the appropriate filesets. remove the /etc/inittab entries. can cause system crashes. that you have fully tested the scanning tool on a non-production server and network.2. Make sure you have the proper written authorization in place prior to running any of these tools on your systems. This is not required and should only be undertaken by someone with sufficient AIX skills since there is a high risk involved with removing system-level filesets. Verify that the entries in /etc/inittab reflect the software that is installed on the server. rather than removing them.Important Many organizations have very strict policies in place against running certain types of tools. Additionally. be sure to make a backup copy of it. It is also a good idea to have a known-good system backup. typically have entries in /etc/inittab. such as sniffers and scanners. on a production network.1 Removing entries from /etc/inittab Important Prior to making any changes to /etc/inittab. in rare cases. Ensure that you have current known-good backups. and that you have informed the relevant parties before launching a scan on the production network. The following default entries in /etc/inittab are candidates for removal since they are usually not required: 142 Additional Security Tools for AIX Systems . such as NSA. scanning tools. 8. If the software is no longer used on the server. We recommend disabling services. Applications. Oracle. HACMP. such as TSM. and so on.
you can do so with the rmitab command as follows: # for i in piobe qdaemon writesrv uprintfd httpdlite df imnss imqss \ >do \ >rmitab $i \ >done Removing the entries from /etc/inittab will disable them from automatically starting. The piobe program is the spooler backend program called by the qdaemon program. 8. but great care must be taken when doing this.1 The piobe and qdaemon entries The qdaemon program is used to schedule jobs for printing. and configure docsearch to use your installed Web server. you can remove httpdlite.1.ibm.2 The httpdlite. For docsearch to function properly.com/doc_link/en_US/a_doc_lib/aixgen/topnav/topnav. This information is provided to help you determine whether or not these entries are needed on your systems. Reboot the server after the modification to test the change and ensure that everything else still properly starts.htm Chapter 8.httpdlite fileset.2. You may also want to alter the permissions (chmod 0000 <filename>) on the executables to further disable the service. see: www.piobe:2:wait:/usr/lib/lpd/pio/etc/pioinit >/dev/null 2>&1 # pb cleanup qdaemon:2:wait:/usr/bin/startsrc -sqdaemon writesrv:2:wait:/usr/bin/startsrc -swritesrv uprintfd:2:respawn:/usr/sbin/uprintfd httpdlite:2:once:/usr/IMNSearch/httpdlite/httpdlite -r /etc/IMNSearch/httpdlite/ httpdlite. and imqss entries The httpdlite program is the default Web server for the docsearch engine and is installed by default. and httpdlite is the version that comes with the IMNSearch.1. If you have another Web server.conf & >/dev/console 2>&1 dt:2:wait:/etc/rc. 8.rs6000. a Web server is required. The following sections provide detailed descriptions of the default /etc/inittab entries. These two entries are required if the server is set up for printing. You can even go so far as to uninstall the filesets (particularly the Dt filesets used for CDE). imnss. For more information on how to do this. Securing AIX 143 . It processes the print job and serves as the print job manager.rte.2.dt imnss:2:once:/usr/IMNSearch/bin/imnss -start imnhelp >/dev/console 2>&1 imqss:2:once:/usr/IMNSearch/bin/imq_start >/dev/console 2>&1 If you decide to remove these entries.
to ensure that it is not put back in. This server process communicates with the client process (write) and provides whatever services are requested. By default. Kernel messages are submitted through the NLuprintf and uprintf kernel services. Removing the writesrv entry prevents use of the write command between systems but does not effect its use between users on the local system. inetd.1.tcpip script starts the TCP/IP daemons. snmpd.dt entry. portmap. If you find a service listening on an unknown port. To determine which TCP/IP services are actively listening on the system. This daemon is generally not required. Remove the /etc/rc. 144 Additional Security Tools for AIX Systems . Uninstalling CDE (Dt) filesets is another option.2 Removing entries from /etc/rc. you can use tools. In order for this communication to work.2.tcpip The /etc/rc. and the man pages provide much faster access to information than does the docsearch engine. the man pages are sufficient. converts. CDE should not be run on servers because of the security issues inherent in it as well as the X window system on which it sits. 8. and docsearch is not really required.4 The writesrv entry The writesrv daemon enables users to communicate back and forth between systems by means of the write command. 8. For the ones that you do need.1. and always keep them up-to-date with the latest patch levels. 8. and use a tool.3 The dt entry The /etc/rc. Unless absolutely essential.In most cases.5 The uprintfd entry The uprintfd daemon retrieves. be sure to modify their configuration files to further tighten down security.1. such as lsof (see Section 6. Storing local copies of man pages is rarely an issue with the disk sizes today. The writesrv daemon receives incoming requests from a write command and creates a server process to handle the request. sendmail.2. the receiving system(s) must have the writesrv daemon running. "List Open Files (lsof)" on page 103). the syslog. The one advantage that docsearch provides over the man pages is its search capabilities.2. such as Tripwire. to help determine the ownership. formats.2.5. 8. You may not need some of these (especially dpid2).dt script is used to start Common Desktop Environment (CDE). use the netstat -af inet command. and writes kernel messages to the controlling terminals of processes. and dpid2 daemons are started.
In addition. Securing AIX 145 . Note that all TCP/IP connections will be severed when you run /etc/tcp. then run /etc/rc. either comment it out (add a # at the beginning of the line) or delete the entry from the file. We suggest the latter because it is all too easy for another administrator to uncomment the line during a problem determination session and unknowingly open a potential and unnecessary security vulnerability.tcpip. or you can run the /etc/tcp. To stop the unwanted TCP/IP daemons.tcpip to restart only those that are still uncommented in the file. the following daemons do not need to be started: Chapter 8. In most cases. This is very disruptive and should not be done on a production server outside of a maintenance window. you can either wait for a maintenance reboot of the system. ensure that you are locally connected to the system because all telnet connections will be dropped as well.To prevent a service from starting in /etc/rc.clean.clean script to stop all TCP/IP daemons.
and dhcprd entries DHCP (Dynamic Host Control Protocol) is a protocol that enables network clients to receive their IP addresses from a server pool of IP addresses. When a client machine is 146 Additional Security Tools for AIX Systems .2.# Start up dhcpcd daemon #start /usr/sbin/dhcpcd "$src_running" # Start up autoconf6 process #start /usr/sbin/autoconf6 "" # Start up ndpd-host daemon #start /usr/sbin/ndpd-host "$src_running" # Start up the ndpd-router daemon #start /usr/sbin/ndpd-router "$src_running" # Start up print daemon #start /usr/sbin/lpd "$src_running" # Start up routing daemon (only start ONE) #start /usr/sbin/routed "$src_running" -q #start /usr/sbin/gated "$src_running" # Start up Domain Name daemon #start /usr/sbin/named "$src_running" # Start up time daemon #start /usr/sbin/timed "$src_running" # Start up Network Time Protocol (NTP) daemon #start /usr/sbin/xntpd "$src_running" # Start up rwhod daemon (a time waster) #start /usr/sbin/rwhod "$src_running" # Start up the Simple Network Management Protocol (SNMP) daemon # start /usr/sbin/snmpd "$src_running" # Start up the DHCP Server #start /usr/sbin/dhcpsd "$src_running" # Start up the DHCP Relay Agent #start /usr/sbin/dhcprd "$src_running" # Start up the DPID2 daemon start /usr/sbin/dpid2 "$src_running" # Start up the mrouted daemon #start /usr/sbin/mrouted "$src_running" The following sections provide detailed descriptions of these entries. This information is provided to help you determine whether or not these entries are needed on your systems. 8.2. DHCP is an extension of the bootp protocol. dhcpsd.1 The dhcpcd.
you define static routes to the system. 8.3. These daemons are typically used in time-sensitive environments. instead of using dynamic routing. and some firewalls (to synchronize connection tables). So. 8.2. see Section 8. Generally. such as DCE/DFS cells.2.4 The routed and gated entries Routed and gated are two daemons used to implement dynamic routing. For more information on DNS.2.6 The timed and xntpd entries Timed and xntpd are two different time synchronization daemons. 220.127.116.11 The autoconf6.2. The DHCP server responds with an IP address assigned from its pool of addresses. 8. this machine has an attached printer that is used by remote machines for printing. When this is the case.1. They are used by servers to synchronize their time with a reliable clock source. In other words. For more information on the no options. leave these entries commented.2. you want to keep things deterministic. Chapter 8. If you do not use DHCP with your AIX servers.5 The named entry The named daemon is used when the local server acts as a Domain Name System (DNS) server providing name resolution services to other machines on the network. "Step 3: Set proper network (no) options" on page 186. The client then uses this assigned IP address to configure the remainder of its network services and finish booting. leave these entries commented.configured to use DHCP boots. If you are not using IPv6. and ndnpd-router entries The autoconf6 process is run at boot time to configure the IPv6 network interfaces and to add necessary routes. see Section 8. ndpd-host.2. server.4. and relay components of the protocol.2. You can run either routed or gated but not both. SP complexes (NTP is used by default). The entries correspond to the client.3 The lpd entry The lpd daemon is required if this machine acts as a print server to other machines. Securing AIX 147 . "Domain Name System (DNS)" on page 153. The ndp entries are also for IPv6 and are not yet commonly used. 8. in a secure environment.2. and be sure to set the network (no) options accordingly. leave the entries commented. it sends out a request for an IP address to a DHCP server.
and should not be used. there is still a 148 Additional Security Tools for AIX Systems . "Simple Network Management Protocol (SNMP)" on page 180. For those services that are required. and rlogind executables with their SSH equivalents. leave it commented.10 The mrouted entry Mrouted is used to forward multicast datagrams. you can replace telnet. and should be removed.3. rlogin. Unfortunately. rsh. sftp).2.3 Removing entries from /etc/inetd. 8. and modify the permissions of the executable (chmod 0000 /usr/sbin/dpid2). see Section 5. rsh. and ftp with SSH equivalents (ssh.2. (For more information about SSH. rshd.2. (For detailed information about how to set up TCP Wrapper. consider protecting them with TCP Wrapper.2. "Secure Shell (ssh)" on page 59. you may also be able to remove services that are normally considered necessary. In some cases. 8. For more information on configuring SNMP.2. "TCP Wrapper" on page 77. is a security exposure. If it is needed.2.conf configuration file) as needed.8 The snmpd entry SNMP is used for network administration. For example.) TCP Wrapper protects these services through access control and logging.conf.9 The dpid2 entry DPID is a legacy SNMP daemon. you should change the community names to unique. It is a very big security exposure. comment out the telnet. ftpd. see Section 8. 8. This design is meant to reduce system load.4. Unneeded services should be commented out. telnetd. at a minimum. Delete the entry from /etc/rc. You might also consider replacing the ftp. It is rarely used.tcpip.7 The rwhod entry This daemon is used to provide remote users with information about who is logged in to the server. It has security vulnerabilities and should be removed if not needed. telnet. This also means additional opportunities for attack.) If you decide to go with SSH. Each new daemon started by inetd results in another active port being available for remote client connection. which are more secure. see Section 5. The only drawback to this approach is that they will almost certainly be overwritten by OS upgrades and patches requiring you to redo the replacements each time.2.2.2. and ftp services in /etc/inetd.1.conf The inetd daemon acts as a master server that invokes other daemons (specified in the /etc/inetd. rlogin. rsh.2. 8. If you are not using multicasting. scp. hard-to-guess names.8.
conf file. To prevent inetd from starting a service. and then refresh inetd (refresh -s inetd). we removed the following services from the /etc/inetd. Securing AIX 149 . A lot of these services are nice to have but may present a security problem. For our basic setup.problem with many of these services exchanging authentication information in clear text across the network. only enable those services that are absolutely required. This is not meant to be a definitive list. Chapter 8. klogin. bootps. kshell. However. You need to decide which services to run and which to remove based on your environment. you can selectively turn them off when they are not required and reenable them when they are. comment it out in the /etc/inetd. In an SP environment. again. and tftp are required. so.conf configuration file. TCP Wrapper does nothing to solve this.
#shell stream tcp6 nowait root /usr/sbin/rshd rshd #kshell stream tcp nowait root /usr/sbin/krshd krshd #login stream tcp6 nowait root /usr/sbin/rlogind rlogind #klogin stream tcp nowait root /usr/sbin/krlogind krlogind #exec stream tcp6 nowait root /usr/sbin/rexecd rexecd #comsat dgram udp wait root /usr/sbin/comsat comsat #uucp stream tcp nowait root /usr/sbin/uucpd uucpd #bootps dgram udp wait root /usr/sbin/bootpd bootpd /etc/bootp tab #finger stream tcp nowait nobody /usr/sbin/fingerd fingerd #systat stream tcp nowait nobody /usr/bin/ps ps -ef #netstat stream tcp nowait nobody /usr/bin/netstat netstat -f inet # #tftp dgram udp6 SRC nobody /usr/sbin/tftpd tftpd -n #talk dgram udp wait root /usr/sbin/talkd talkd #ntalk dgram udp wait root /usr/sbin/talkd talkd #rquotad sunrpc_udp udp wait root /usr/sbin/rpc.pcnfsd pcnfsd 1500 01 1-2 #echo stream tcp nowait root internal #discard stream tcp nowait root internal #chargen stream tcp nowait root internal #daytime stream tcp nowait root internal #time stream tcp nowait root internal #echo dgram udp wait root internal #discard dgram udp wait root internal #chargen dgram udp wait root internal #daytime dgram udp wait root internal #time dgram udp wait root internal #instsrv stream tcp nowait netinst /u/netinst/bin/instsrv instsrv -r /tmp/n etinstalllog /u/netinst/scripts #ttdbserver sunrpc_tcp tcp wait root /usr/dt/bin/rpc.ttdbserv er rpc.ttdbserver 100083 1 #dtspc stream tcp nowait root /usr/dt/bin/dtspcd /usr/dt/bin/dtspcd #cmsd sunrpc_udp udp wait root /usr/dt/bin/rpc.sprayd sprayd 100012 1 #pcnfsd sunrpc_udp udp wait root /usr/sbin/rpc.ssalld rpc. This information is provided to help you determine whether or not these entries are needed on your systems.rquotad rquota00011 1 #rexd sunrpc_tcp tcp wait root /usr/sbin/rpc.ruser sd rusersd 100002 1-2 #rwalld sunrpc_udp udp wait root /usr/lib/netsvc/rwall/rpc.cmsd cmsd 100068 2-5 #imap2 stream tcp nowait root /usr/sbin/imapd imapd #pop3 stream tcp nowait root /usr/sbin/pop3d pop3d #ssalld sunrpc_tcp tcp wait root /usr/sbin/rpc. 150 Additional Security Tools for AIX Systems .rstatd rstatd 1000 01 1-3 #rusersd sunrpc_udp udp wait root /usr/lib/netsvc/rusers/rpc.ssalld 300667 1 #kfcli stream tcp nowait root /usr/lpp/ssp/install/bin/kfserver kfserver #xmquery dgram udp wait root /usr/bin/xmservd xmservd -p3 The following sections provide detailed descriptions of these entries.rwalld rwalld 100008 1 #sprayd sunrpc_udp udp wait root /usr/lib/netsvc/spray/rpc.rexd rexd 100017 1 #rstatd sunrpc_udp udp wait root /usr/sbin/rpc.
1 The shell (rshd) and login (rlogind) entries These entries are for rsh.3. See Section 5.2. data from commands. 8. It is important to note that in an SP environment. 8. and the krlogind daemon uses TCP port 543. The rshd daemon uses TCP port 514.2. and the rlogind daemon uses TCP port 513. 8. Securing AIX 151 . It is used to copy one or more source files from one system to one or more destination files on another UNIX system.3. The uucpd daemon uses TCP port 540. 8.3.3. It should be disabled. are transferred in the open without encryption.3. even though the sessions are authenticated. rwalld.7.2. which is used for remote command execution support. for more information.1. The tftp service.8. in particular. These services are required in an SP when installing or network-booting an SP node. The rexecd daemon uses TCP port 512. and rcp command functionality and should be disabled for security reasons.6 The bootps (bootpd) and tftp (tftpd) entries The bootpd daemon implements an Internet Boot Protocol server to enable remote boot of clients.5 The uucp (uucpd) entry The uucp command is a Basic Networking Utilities (BNU) command. see Section 8.2. "Secure Shell (ssh)" on page 59.2 The kshell (krshd) and klogin (krlogind) entries These entries are similar to the shell and login services but are used when Kerberos authentication is used. "File Transfer Protocol (ftp)" on page 184.4 The comsat entry The comsat daemon is the server that receives reports of incoming mail and notifies those users who have enabled this service (with the biff command) accordingly. For more information. As with other "r" services. ruserd. such as rsh and rcp. The krshd daemon uses TCP port 544.7 The finger (fingerd) entry The finger command displays information about the users currently logged in to a system (either local or remote). The tftp command uses trivial file transfer protocol to transfer files from one system to another. has a number of security issues that you need to be aware of if you plan to leave it enabled. 8. rstatd.3.2. The bootpd daemon uses UDP port 67. and the tftpd daemon uses UDP port 69. rlogin. and rquotad entries The exec (rexecd) entry is for rexec command functionality. The other daemons listed here use rpc (portmap) for their port allocation.220.127.116.11.3 The exec. They are typically required in SP environments. as it is commonly Chapter 8. it should be disabled. 8. The comsat daemon uses UDP port 512.
The port usage is as follows: echo uses TCP and UDP port 7. 8.3. The pcnfsd daemon uses rpc (portmap) for its port allocation. 8. The rexd daemon uses rpc (portmap) for its port allocation.13 The pcnfsd entry The pcnfsd daemon provides NFS service to PC clients.2. 8. 8. it should be disabled.2. It uses TCP port 11. this entry should be disabled. it should be disabled.2. any program emulating the on command can obtain shell access. chargen. time. The fingerd daemon uses TCP port 79.2.3. in turn.14 The echo. It has a history of attackers using untrapped-meta-character vulnerabilities to execute unauthorized commands on remote systems.8 The systat (ps) entry The systat entry provides support for the ps command. and daytime uses TCP and UDP port 13.11 The rexd entry With the rexd daemon running. which. 8.3. time uses TCP and UDP port 37.2.10 The talk (talkd) and ntalk (talkd) entries The talk command allows two users on the same system or on different systems to have an interactive conversation.3. such as the password file. For this reason. chargen uses TCP and UDP port 19. The sprayd daemon uses rpc (portmap) for its port allocation.3.9 The netstat entry The netstat entry provides support for the netstat command.3. Because of the security risks. The talkd daemon uses TCP port 518. and daytime entries All these services can be spoofed into sending data from one service on one system to another service on another system resulting in an infinite loop and creating a denial of service attack. Because the spray command can be used for both buffer overflow and denial of service attacks.3. 8. provides access to files on the remote system including things.2.used for social-engineering attacks and buffer-overflow attacks. It uses TCP port 15.12 The sprayd entry The sprayd daemon provides support for the spray command. 8.2. 152 Additional Security Tools for AIX Systems .
3.3 Step 2: Tighten configurations of remaining services No doubt. some services will still be required to support the normal production activities of the server. and support for it has been dropped. These services typically include things. The extent of the configuration changes will depend on the security level that you are trying to achieve. BIND4 is the older protocol. CDE should not be used on a server unless absolutely required.1 Domain Name System (DNS) DNS is used to map a host name to an IP address and vice-versa. you do not need it. 8. Two different BIND versions (BIND4 and BIND8) are in common use. and the pop3d daemon uses TCP port 110. SMTP. It uses TCP and UDP port 9. 8.isc. The BIND homepage is: http://www. which includes more capabilities.2. The imapd daemon uses TCP and UDP port 143 for imap2. The local host table solution does not scale well. built-in security. disable these entries. dtspc. Other means of host name resolution include the local host table (/etc/hosts) and NIS. Basically.2. 8. and cmsd entries These entries are used for the CDE environment. DNS and BIND are so closely related that the terms are interchangeable.8. If this system is not serving as an imap or pop3 server.3. you should adjust the default configurations to further tighten their security.2. 8. Securing AIX 153 . All of these services use rpc (portmap) for their port allocation. and NIS has a number of well-known security issues. disable these entries also. BIND8 is the newer protocol. and support for bug fixes. and SNMP. In all likelihood. For these reasons. it is a host name to IP lookup protocol.16 The ttdbserver.3. On AIX.org/products/BIND/ Chapter 8.17 The imap2 (imapd) and pop3 (pop3d) entries Both of these daemons are used to retrieve mail. If you are disabling CDE. DNS is managed by BIND (the Berkeley Internet Name Daemon). For any remaining active services. such as DNS.15 The discard entry As its name implies.3. DNS is the most commonly used solution. Each has had buffer overflow problems in the past. discard discards whatever is sent to it by a client. NFS.
acme. Once your name server finally gets the IP address for west. host name resolution will be hindered by the cache rather than helped.3.8.west. to which other DNS name server should I escalate this request? Escalating the request and receiving the answer can be quite time consuming.3.).com. Assuming the worst case scenario. it will not have to make the preceding queries again until the information in its cache expires.com. with the volatile nature of the Internet. ("dot".france. If not. A client knows its DNS name server by IP address only. each DNS name server manages a local cache of the answers to its most recent queries. spoofing means: Nonsense. acme. 5. a gentle satirical imitation. com.1 DNS principles When asked to resolve a host name to IP address (for example. Is the answer in the my local DNS cache? 2.dictionary. does this name belong to my DNS domain? 3. To reduce both network load and delays.xyz.acme. 4. the DNS name server tries to answer the following three questions: 1.fr.france. 154 Additional Security Tools for AIX Systems . a light parody. The following domain name servers will be queried in sequence (assuming no cache hits along the way): 1.1.com.2 DNS spoofing According to www. the question of how to keep DNS cache up-to-date with the thousands of address changes that occur every day remains.). (If the address associated with a host name changes but the local DNS cache still has the old information. let us say that your DNS name server belongs to a completely different DNS domain (for example.acme.france. sales. a hoax. This IP address can be faked by an attacking machine on the LAN (for instance. If not.acme. abc. a portable computer).com. 3. france. . this is the top of the DNS tree) 2. However.com. If that false name server answers faster than the real name server. west.1.) We will return to the question of DNS cache consistency shortly..com. The use of DNS cache typically speeds up name resolution by anywhere from one to three orders of magnitude. 8.
attackers designed a new and improved version of DNS spoofing. there is no need to disturb anything further up the DNS hierarchy. imagine that the IP address that was updated was the IP address to a Web site that provides secure content. this technique has the following drawbacks from the point of view of the attacker: • It requires a machine to be connected to the LAN.it can misdirect the querying client to other hostile computers.3. For these reasons. the false name server will only fool the clients that are querying DNS as they boot. Even if it is faster. 8. • A single IP address associated with two different MAC addresses is easy to detect by system and network administrators because it generally causes additional problems on the network. in principle. the DNS name server sending the update requests does not belong to the same DNS domain as the local DNS name server. and. the remote DNS name server is not a trusted host. it looks and feels just like the real site. Suppose further that the attackers have managed to duplicate the home page of that site on the host whose IP address they substituted for the legitimate one. • Success is not guaranteed. Chapter 8. "DNS principles" on page 154. and you unknowingly attempt to log in with your account number and password. The other clients on the LAN already have the MAC address for the real DNS name server in their ARP cache. Prior to BIND 8.1.1. Securing AIX 155 . The whole idea behind DNS spoofing is to send counterfeit update requests to a DNS name server. and since it is an update to a fully-qualified host name. By definition. However.1. Since it appears as nothing more than a routine update of the IP address associated with a given host name. How the DNS spoofing exploit works Here is an example of how the DNS spoofing exploit works: The attacker starts by sending a bogus update to a DNS name server. there was no way to prevent this. that cached addresses need to be updated whenever they change. To you. The update changes the IP address of a fully-qualified host name in the DNS name server cache. the update should not be allowed.2.3. everything seems fine.3 The new and improved DNS spoofing We saw in Section 8. Now. In other words.
the attackers blackhole you. then put up some fake message (such as "site busy" or "requested page not found") and ask you to try again later. rather than to the legitimate destination (real server). when someone looks up the name for that entry.The attackers now employ a technique known as blackholing. they turn around and use your identity and password to access the legitimate site. DNS spoofing is more subtle. With DNS spoofing. If the two IP addresses do not match. they will be long gone. the request is denied and a warning message issued. which is included in AIX 4. reverse access table is much more difficult. because they accessed the site with your legitimate account number and password.3. (Faking an address in a direct access table is easy. guarantee the integrity of the DNS queries and responses. From then on. Protection against the DNS spoofing exploit One form of protection against DNS spoofing involves a software modification to do an extra DNS lookup for each request. Then. but inserting a fake address at the correct location in a sequential. By the time you realize what has happened. they get the phone 156 Additional Security Tools for AIX Systems . These security extensions enable DNS resolvers and DNS name servers to cryptographically authenticate the source and. a second translation from host name back to IP address is performed. This technique is intended to consume time from the requester and is used both by attackers against their victims and by system administrators against suspected attackers. After translating the incoming request from an IP address to a host name. They are incorporated into BIND 8.) To address the growing problem of DNS (and IP) spoofing. a skilled technician takes over the phone number (IP address) of the destination. So. DNS spoofing compared to IP spoofing To illustrate the difference between DNS spoofing and IP spoofing.2. RFC 2065 defines the DNS Security Extensions (DNSSEC). Worse yet. the technician modifies a phone book (DNS server) somewhere in the system and substitutes their phone number (IP address) in place of a legitimate one. While you are waiting for all of this to happen. Instead. Blackholing means intentionally giving no answer to a request.1. the skilled technician keeps their original phone number (IP address) unchanged. we use a telephone system analogy: With IP spoofing. through digital signatures. the site will probably not accept any responsibility for any damage done to you.3. calls (requests) made to that number (IP address) go to the technician (bogus server).
1. is started by default in /etc/rc.number (IP address) of the technician.x AIX 4. DNS spoofing requires IP spoofing at the very beginning to fake the identity of a DNS server. named.tcp. in all likelihood.2. however. Securing AIX 157 .3 BIND 4.1.3.net.9. Chapter 8.4 DNS on AIX The DNS daemon. as shown in the next screen.1.3 ipv6 BIND 8.3 ipv4 BIND 4. Once that is done. At this point.server 4.1 are meant to thwart these kinds of attacks.9.3 (with bos.tcp. AIX versions of BIND AIX Version AIX 3.2 ipv4 BIND 4.9. 8. rather than that of the legitimate owner.net.x AIX 4.13) BIND Version BIND 188.8.131.52.x AIX 4.3 BIND 4.3 ipv6 BIND 8. The security extensions provided in BIND 8.2 (patch 5) To check which version of BIND (BIND4 or BIND8) is running on the system.220.127.116.11. is probably the address of another site the attacker has broken into). the attacker can revert back to their "legitimate" IP address (which.tcpip.client fileset. look at how the /usr/sbin/named file is symbolically linked (either to /usr/sbin/named4 or /usr/sbin/named8): $ ls -l /usr/sbin/named lrwxrwxrwx 1 root system 16 Mar 08 1999 /usr/sbin/named -> /usr/sbin/named4 $ ls -l /usr/sbin/named-xfer lrwxrwxrwx 1 root system 21 Mar 08 1999 /usr/sbin/named-xfer -> /usr/sbin/named4-xfer The named daemon is contained in the bos.x AIX 4. nothing appears out of the ordinary on the network. The version of BIND is dependent on the version of AIX as shown in Table 4: Table 4.3.9.
# cd /usr/samples/tcpip # chmod u+x named-bootconf. The easiest way to do this is with the /usr/samples/tcpip/named-booconf.server|more Fileset File ---------------------------------------------------------------------------Path: /usr/lib/objrepos bos./named-bootconf..$ type named4 named4 is /usr/sbin/named4 $ lslpp -w /usr/sbin/named4 File Fileset Type ---------------------------------------------------------------------------/usr/sbin/named4 bos.conf #rm /usr/sbin/named #rm /usr/sbin/named-xfer #rm /usr/sbin/nsupdate #cd /usr/sbin #ln -s named8 named #ln -s named8-xfer named-xfer #ln -s nsupdate8 nsupdate #startsrc -s named 0513-059 The named Subsystem has been started.server 4. you can use the h2n PERL script to convert the /etc/hosts file into the appropriate named files. stop named. restart named: # stopsrc -s named 0513-044 The named Subsystem was requested to stop.hosts /usr/sbin/named -> /usr/sbin/named4 .pl /etc/named.tcp.boot) into the BIND8 configuration file (/etc/named. Finally. convert the BIND4 configuration file (/etc/named.tar..pl # .my /usr/sbin/rsvpd /usr/sbin/XNSquery /usr/samples/snmpd/unix. Next. Then.tcp.0 /usr/sbin/trpt /usr/sbin/named8-xfer /usr/samples/snmpd/view. If you are setting up BIND8 on a system that previously just used /etc/hosts for name resolution.my /usr/sbin/mosy /usr/samples/tcpip/named. relink the named.net.net/published/oreilly/nutshell/dnsbind/dns.tcp.Z 158 Additional Security Tools for AIX Systems .server File $ lslpp -f bos. The h2n PERL script is available via anonymous FTP from: ftp://ftp.pl PERL script. Converting from BIND4 to BIND8 is fairly straightforward.boot > /etc/named. First. Subsystem PID is 12346.conf). and nsupdate files.3.3.net. named-xfer.uu.net.
com from the primary master name server: Chapter 8. and network mapping.1. and. The allow-transfer substatement can be used as a zone substatement to restrict transfers of a particular zone. It takes as its argument a list of addresses to match against.com zone have IP addresses 192. only one at a time.184.108.40.206 Securing DNS on AIX The following configuration changes will help make DNS more secure on AIX: Restrict zone transfers Restricting zone transfers enables you to control which servers (trusted servers) may request and receive zone transfers from your DNS server. This option is available with BIND 4. The allow-transfer substatement in BIND 8 and the xfrnets directive in BIND 4.0. Web servers. It provides information about things. Any user on a remote system that is able to query the zone data of your DNS name server is only able to look up data (such as IP addresses) for hosts whose domain names they already know. The information provided by a DNS zone transfer is of great value to a would-be attacker. For example.9 enables you to apply access lists to zone transfers. Any user on a remote system that is able to request and receive zone transfers from your DNS name server is able to see all of the DNS data for all of the hosts in your zone(s). Important Be sure to restrict zone transfer access on both your primary and slave DNS server.9 and later. suppose the DNS slave servers for your acmebw.1. then.6. Note The ls subcommand of nslookup is implemented as a zone transfer. server aliases.1 and 192.8. such as mail servers. Securing AIX 159 . or it can be used as an options substatement to restrict all zone transfers. "Nslookup" on page 22.214.171.124. The following zone statement (in /etc/named.conf) allow only those slave servers to transfer acmebw. More information about querying DNS name servers with the nslookup tool can be found in Section 8.
0): options { allow-transfer { 192. you can also establish a global access list for zone transfers.1.168/16. The syntax for including a network mask is 160 Additional Security Tools for AIX Systems .0. With BIND 4. }. allowing only hosts on the Class A network 15. masters { 192. suppose you want to limit all zone transfers to hosts on your internal network (192.9.0. on your DNS slave servers: zone "acmebw.boot).32. }. you can add a network mask. this restriction applies to any zones for which the server is authoritative. }.0.0. allow-transfer { 192.0. file "db.168. With BIND 8. }.zone "acmebw.0 Unlike secure zones.0. Networks are specified in dotted-octet format (in /etc/named.168.acmebw".4.com" { type slave.0.32. For example.0.1. }.0 and the Class B network 128.168.0 to do zone transfers: xfrnets 15. Note that since the default in BIND 8 is to allow any IP address (including ones belonging to attackers) to transfer zones. for example. }.com" { type master. This list applies only to those zones that do not already have explicit access lists defined (via zone substatements). allow-transfer { none.1.0. the xfrnets directive may have arguments that are the networks or IP addresses that are allowed to do zone transfers from your primary master DNS name server.168. }. If you want to specify just a part of the network down to a single IP address. you should also have a zone statement.0 128. such as the following. 192.
Note that no spaces are allowed either between the network and the ampersand or between the ampersand and the netmask. where one DNS server refers you to the next DNS server and so on. This is different from giving a referral.4&255. you will probably want to limit zone transfers to just your slave name servers. In some cases. with DHCP servers. Securing AIX 161 . For a primary master name server on your internal network (behind a firewall). The advantage to recursion is that the servers along the way cache the answers. you must add the allow-update substatement to the name server configuration file (/etc/named. for example. }. Restrict dynamic updates Dynamic DNS is a protocol extension to DNS.32.4 and the subnet 128.255. file "db.255 128. dynamic updates should either not be enabled or enabled only to localhost.255.1.255. potentially speeding up the response time for future queries. }.network&netmask.0&255. dynamic updates are necessary. If authentication is not being used.0: xfrnets 15. Only BIND 8 has the dynamic update capability. To enable dynamic updates.255.conf): zone "acmebw.1.0 For a primary master name server accessible from the Internet. Suppose you want to pare down the addresses allowed to transfer zones in the previous example to just the IP address 15.32.acmebw" allow-update { localhost. It defines a lightweight mechanism that allows for zone data modifications (low overhead) without the need for a complete reloading of zone data.255.255. The update can theoretically originate from a remote host. Chapter 8.152. it does not allow dynamic updates. Restrict recursion Recursion is where DNS servers contact other DNS servers on your behalf and relay the final answer back to you.com" { type master. you will probably only want to limit zone transfers to your slave name servers if you are concerned about your own people listing your zone data.152. By default.
When queried about an unknown host. DNS reverts to referrals. With recursion on. but the advantage is that it makes it much more difficult to spoof. the DNS server sends back a referral to a more authoritative DNS server. it is a good idea to configure your name server to only respond to queries originating from within your internal network. If it is not practical for you to turn recursion off. The response from the query contains bogus data that is then stored in the cache of your name server. your name server queries the information on your behalf from the commandeered name server. The disadvantage is that this may slow down response time. The attacker then queries your name server for information about those zones.With recursion disabled. you should: • Restrict the addresses to which your name server responds • Restrict the addresses to which your name server responds to recursive queries The method for turning off recursion is version-dependent. In other words. and the process repeats. the DNS server attempts to answer the query. The DNS client then contacts this next server in the chain. your DNS name server should be configured to 162 Additional Security Tools for AIX Systems . For an internal DNS server (one sitting on your internal network behind the firewall). The attacker can now relinquish control of the commandeered name server since your name server is now set up to route requests to their servers instead of the legitimate ones. }. For BIND 4. and the DNS spoof is complete.9: options no-recursion For BIND 8: options { recursion no. If it is not able to answer it. Accepting recursive queries from the Internet makes you DNS name server susceptible to DNS spoofing. Suppose an attacker has gained (temporary) control over some remote DNS zones. Restricting queries The purpose of a DNS name server is to answer questions about the zones for which it is authoritative.
this option only works for those zones for which the DNS name server is authoritative.168. but it helps you avoid many potential problems. include one or more special TXT (txt) records in the zone data on the primary master name server.0:255. For BIND 4.0 network: zone "acmebw. To use secure zones.0" Restrict DNS cache update The DNS feature that allows for address updates within cache is known as glue fetching . To restrict queries to your name server from only those hosts on the 192.0 network. restricting queries is accomplished with the secure_zone record.255. In BIND 8. }. In BIND 4. For example.249. Securing AIX 163 . It is an open door for DNS spoofing and should be turned off (fetch-glue no). }.respond to only those queries originating from within the same zones for which it is authoritative. The records are automatically transferred to the slave servers: secure_zone IN TXT "192. the two are done separately.255. This slows the performance of your DNS server (since no cache is built).249. Note This option can also be set at a global level rather than at the zone level.com" { type slave.9: options no-fetch-glue For BIND 8: Chapter 8. (In BIND 8. such as spoofing. The method for turning off glue fetching is version-dependent.168. suppose acmebw. allow-query { 192. It limits access to both individual resource records and zone transfers.0/24.) With BIND 4. this is done with the allow-query substatement inside the zone statement.com is on the 192.168.
fetch-glue no. file "db.147.com". allow-transfer { slaves. }. glue fetching and recursive queries can also be allowed on these servers. Internal resolution name server 164 Additional Security Tools for AIX Systems . Split DNS configuration Consider having two kinds of name servers: • Advertising name servers that are open to the world and non-recursive. }.options { fetch-glue no. }. options { directory /var/named. // the default }. Configuration examples for each type are as follows: Advertising name server acl slaves { 207.com" { type master. }. zone "acmebw. • Internal resolution name servers that can only be queried by known resolvers (internal and secure).69. recursion no.1. If desired.231.acmebw. 209. }.86.3. allow-query { any.
231. file "db.6 Nslookup The nslookup tool is used to query DNS name servers for information about hosts or domains.191. it is packaged in the bos. 8.redbooks.com Address: 198.153 Conversely.com Address: 9.acl internal { 192.net. masters { 207.69.1 Non-authoritative answer: Name: www.2.0/24.245. suppose you want to find the IP address of www. file "bak.168. // the default allow-query { internal. As a simple example. It is commonly used to query a DNS server to obtain the IP address of a server.sg." { type hint.245. recursion yes.tcp. }. suppose you want to find the name associated with IP address 198.com".cache".8. but it has far more functionality than that.153: Chapter 8. zone "acmebw.com: #nslookup www.com" { type slave.ibm. Securing AIX 165 .191. zone ". }.acmebw.client fileset.redbooks. options { directory "/var/named".3. }. }. }. On AIX.184.1.redbooks. }. Nslookup can be used two ways: Interactively and non-interactively (batch). }. allow-transfer { internal.com Server: joyce.
dcx.ans.com nameserver = ns1.ibm.com yahoo. You can also use nslookup to query DNS name servers specific kinds of DNS records.europe.245. You can use that information to query each for more information.200.com mail address = hostmaster.225.arpa name = redbooks.191.com Server: joyce.ibm.#nslookup -type=ptr 198.com Address: 9.arpa nameserver = nis.net internet address = 192.237.184.yahoo.1.in-addr.71.sg.in-addr.arpa nameserver = ns.sg. For example.245.net 191.103.63.com internet address = 204. to find the DNS name servers serving the yahoo.ans.ans.com domain: 166 Additional Security Tools for AIX Systems .153 Server: joyce. For example.1 Non-authoritative answer: 153.com nameserver = ns3.1 Non-authoritative answer: yahoo.74.yahoo.com ns1.europe.yahoo.net internet address = 147.com Address: 9.com serial = 2000080812 refresh = 1800 (30 mins) retry = 900 (15 mins) expire = 1209600 (14 days) minimum ttl = 9 (9 secs) Authoritative answers can be found from: yahoo.com internet address = 216.com nameserver = ns5.51 ns5.yahoo.yahoo.com internet address = 194.33 ns3.ans.com: #nslookup -type=SOA yahoo.in-addr.198. to query for the Start Of Authority (SOA) record from yahoo.dcx.32.198.100 Notice the listing of name servers that are authoritative for the site.191.com origin = ns0.245.yahoo-inc.net nis.com yahoo.22.214.171.124 ns.com Authoritative answers can be found from: 191.yahoo.198.245.corp.8.10 You can also use nslookup to query for the DNS name servers that serve a specific domain.yahoo.
108.ibm.51 ns5.yahoo.in-addr.71. it failed.dcx.com [merlin.yahoo.com command was issued.dcx. so.184.1 Non-authoritative answer: yahoo.arpa Address: 127.ibm.ibm.12.com Address: 9.yahoo.ibm. zone transfers must be allowed in order for the ls subcommand to work.0.0.0.74.com [merlin.com internet address = 204. use the ls subcommand of nslookup to list the servers in the domain: > ls <domain name> Recall that the ls subcommand of nslookup does a zone transfer.yahoo.com yahoo.com] *** Can't list domain alibaba.europe. # nslookup Default Server: LOCALHOST. That is because we had zone transfers disabled.32.0.com command.ibm.12.itso.sg.com] 10M IN NS merlin merlin 10M IN A 9.com Address: 9.5 > ls alibaba.ibm.10 ns1. Chapter 8.18 loopback 10M IN A 127.com yahoo. We then enabled zone transfers and reissued the ls alibaba.12.0.50 aixfw 10M IN A 172.12.yahoo. Securing AIX 167 . the entire domain listing was returned this time.ibm.com nameserver = ns5.# nslookup -type=NS yahoo.com nameserver = ns1.5 Default Server: sp5cw0.0.itso.1.0.33 You can also use nslookup to list all servers in a given DNS domain.yahoo.5 Success Notice that the first time the ls alibaba.1 >server 9.237.1.com internet address = 194.8.com:Unspecified error > ls alibaba.com internet address = 216.0.com Authoritative answers can be found from: ns3.itso.0.4 arthur 10M IN A 9.ibm.12.europe.ibm.1 cws 10M IN A 9.com nameserver = ns3.0. Start by connecting to the DNS server (in interactive mode) with the server subcommand in nslookup: > server <DNS server IP address> Then.200. As you can see.com Server: joyce.127.0.
if you have a DNS name server that is accessible to hosts on the Internet. sp5cw0: 168 Additional Security Tools for AIX Systems . You can use the rpcinfo command to query the portmap daemon on a remote system to determine if NFS is active. the access control list is the /etc/exports file.3 Network Information Services (NIS and NIS+) Guide for detailed information on NIS and its derivatives. However. NFS and NIS both use Sun's Remote Procedure Call (RPC) protocol. sometimes. you should check to make sure that only those servers that need to be visible outside of your DMZ show up and all others are hidden. The one used by NFS and NIS is AUTH_UNIX or.6 of AIX 4. Both protocols have a tight history with each other. disable the portmap daemon. Be sure to keep it at the latest security patch level. we refer you to Section 7. Knowing that no RPC services are active on a server still provides useful information to a would-be attacker. SG24-5962.3. The RPC protocol supports several authentication methods. If your server is not using any of these RPC services. Suppose you want to see which RPC services are active on host. Notice that any user can use rpcinfo to query the portmap daemon on a remote system to determine which RPC services are active. the portmap daemon has been subject to buffer overflow attacks. The Network Information Service (NIS) provides central administration of key system files. AUTH_SYS.2 Network File System and Network Information Service The Network File System (NFS) provides local access to remote file systems. nslookup is also very useful for ensuring that your DNS is properly configured to not give out any more information than is necessary. Applications do the same thing to locate the port for a given service. or disable it if it is not needed. or the Network Information Service (NIS) Overview for System Management in AIX Version 4. In the case of NFS.In addition to general-purpose DNS debugging. The portmap daemon converts RPC program numbers to Internet port numbers. With AUTH_UNIX. Historically. It gives them information about what not to attack. you can determine on which port an RPC service is listening. By querying portmapper (TCP/UDP port 111) with the rpcinfo program.3 Elements of Security Effective and Efficient Implementation. NIS will not be covered in detail here. such as /etc/passwd and /etc/hosts. 8. For example. the client sends user ID and group ID information along with the request. The server assumes this is legitimate information from the client and grants or denies access based on the access control list stored on the server. which uses portmapper to allocate ports. Instead.
$ rpcinfo -p sp5cw0 program vers 100000 100000 100000 100000 100000 100000 100001 100001 100001 100002 100002 100008 100012 150001 150001 100083 100068 100068 100068 100068 300667 100003 100003 100003 100003 200006 200006 100005 100005 100005 100005 100005 100005 100024 100024 200001 200001 200001 100021 100021 100021 100021 100021 100021 100021 100021 100099 1342177279 1342177279 1342177280 1342177280 proto port service 4 tcp 111 portmapper 3 tcp 111 portmapper 2 tcp 111 portmapper 4 udp 111 portmapper 3 udp 111 portmapper 2 udp 111 portmapper 1 udp 32780 rstatd 2 udp 32780 rstatd 3 udp 32780 rstatd 1 udp 32781 rusersd 2 udp 32781 rusersd 1 udp 32782 walld 1 udp 32783 sprayd 1 udp 32784 pcnfsd 2 udp 32784 pcnfsd 1 tcp 32769 ttdbserver 2 udp 32785 cmsd 3 udp 32785 cmsd 4 udp 32785 cmsd 5 udp 32785 cmsd 1 tcp 32770 2 udp 2049 nfs 3 udp 2049 nfs 2 tcp 2049 nfs 3 tcp 2049 nfs 1 udp 2049 1 tcp 2049 1 udp 32795 mountd 2 udp 32795 mountd 3 udp 32795 mountd 1 tcp 32774 mountd 2 tcp 32774 mountd 3 tcp 32774 mountd 1 udp 746 status 1 tcp 746 status 1 udp 755 1 tcp 755 2 tcp 755 1 udp 32818 nlockmgr 2 udp 32818 nlockmgr 3 udp 32818 nlockmgr 4 udp 32818 nlockmgr 1 tcp 32775 nlockmgr 2 tcp 32775 nlockmgr 3 tcp 32775 nlockmgr 4 tcp 32775 nlockmgr 1 udp 32839 autofs 4 tcp 37661 1 tcp 37661 4 tcp 49690 1 tcp 49690 Chapter 8. Securing AIX 169 .
vu.gz The nfs utility has an ftp-like interface. In our case. run make to compile the nfs utility: 170 Additional Security Tools for AIX Systems .cs. Download the package. and specifying the appropriate C compiler. Finally.4.tar. You also need to modify the Makefile by commenting out the Solaris section. we used the version 4.images (everyone) /spdata/sys1/install/aix433/lppsource (everyone) Notice that any user can use the showmount command to find out which directories are exported from a remote server. you can easily see the dangers of exporting a file system with root access. you can see that NFS (port 2049) is active on the target system. they may also be able to find out the individual server names for the servers that are allowed access to the exported directories. With it.4 C compiler (/usr/vac/bin/cc) on AIX 4.3. and.3. You need access to both the gzip utility (available from the Bull site) and a C compiler.1. All of this is useful information for a would-be attacker. uncompress it. uncommenting the AIX section. you can now use the showmount command to see which filesystems are exported from host sp5cw0: $ showmount -e sp5cw0 export list for sp5cw0: /spdata/sys1/install/pssplpp (everyone) /usr/sys/inst. "Ensuring the integrity of downloads" on page 136). Knowing that NFS is active. depending on how the exports are set up. There is a very useful NFS client utility (nfs) available from: ftp://ftp. and verify that it has not been tampered with (see Section 7.nl/pub/leendert/nfsshell.From the output.
x steal. 12107 bytes.o mount_xdr.c. x nfs/nfs_prot_xdr.c nfs_prot.c.h.x.x #CC = gcc #CFLAGS = -DSYSV -DREADLINE -I/usr/local/include #LIBS = -lsocket -L/usr/ucblib -R/usr/ucblib -lrpcsoc -lnsl \ -L/usr/local/lib -lreadline -lhistory -ltermlib # uncomment the following 3 lines for AIX CC = cc CFLAGS = -DAIX LIBS = # make nfs cc -DAIX -c mount_clnt. 5744 bytes.o Chapter 8. x nfs/READ_ME.h nfs_prot_xdr.c.c nfs_prot_svc. x nfs/mount_clnt.c cc -DAIX -c nfs_prot_clnt. 2579 bytes.c READ_ME mount_clnt. 6405 bytes.o nfs_prot_clnt. 3088 bytes. 1687 bytes.tar.o nfs. 2259 bytes.# ls -l total 96 -rw-r----.c cc -g -o nfs mount_clnt. 12 media blocks. 4 media blocks. x nfs/mount_svc. 6358 bytes.c.o nfs_prot_xdr . 53673 bytes. 24 media blocks. 13 media blocks. 2 media blocks.h mount_xdr.c # vi Makefile # uncomment the following 4 lines for Solaris 2.c.c cc -DAIX -c mount_xdr.h. 828 bytes.c cc -DAIX -c nfs. 4144 bytes.c mount. 4 media blocks. 9 media blocks.c. x nfs/steal. x nfs/nfs_prot_svc. 13 media blocks.gz # /usr/local/bin/gzip -d nfsshell.c nfs_prot_clnt. 12153 bytes.tar x nfs x nfs/Makefile.tar. x nfs/mount.x nfs.c nfs_prot.gz # tar -xvf nfsshell. x nfs/nfs_prot. 6 media blocks. 1935 bytes. 105 media blocks. 5 media blocks. 7 media blocks.c. x nfs/mail x nfs/mail/Friedrichs.c cc -DAIX -c nfs_prot_xdr. x nfs/mount_xdr. x nfs/nfs. 7750 bytes.x.c mail mount_svc. x nfs/mount. Securing AIX 171 . x nfs/nfs_prot.c. # cd nfs # ls Makefile mount. 17 media blocks.1 root system 29393 Aug 29 09:52 nfsshell. 16 media blocks. 24 media blocks. x nfs/nfs_prot_clnt. 8287 bytes.
transfer size 8192 bytes. With the status subcommand. we change our IDs to root. Lastly. With the uid and gid subcommands. we run nfs from a non-privileged user account. so. nfs> ls -l -rwx-----. Be sure also to set the permissions as tightly as possible. and only move the executable program to the production system. From the export subcommand. Next. Now.5. we see that we currently have permissions as user nobody (-2) and group nobody (-2). let us take a look at how to use the nfs utility to see the dangers of exporting an NFS filesystem with root access. We started by NFS exporting the /node5 filesystem from host node5 using defaults and giving root access to host node13. For this example.Important For security reasons. we used our lab SP system. with the ls subcommand.1 0 3 17 Aug 29 10:01 aaa nfs> cat aaa this is file aaa nfs> uid -2 nfs> cat aaa aaa: Permission denied 172 Additional Security Tools for AIX Systems . even though nfs was not started as root. it is not a good idea to have a C compiler loaded on a production system. On node13. Compile the program on a non-production system. we mount it with the mount subcommand.168. we see that there is a file (aaa) with access permissions for root only. TCP. we open a connection to node5 with the host subcommand. Then. we see that the /node5 filesystem is exported. we change our user ID back to nobody (-2) to show that we no longer have access to the file (aaa): $ nfs nfs> status User id : -2 Group id : -2 Transfer size: 0 nfs> host node5 Using a privileged port (1023) Open sp5en05 (192. The cat subcommand proves that we now have root access in the /node5 file system. Now comes the really scary part.5) TCP nfs> uid 0 nfs> gid 0 nfs> export Export list for sp5en05: /node5 everyone nfs> mount /node5 Using a privileged port (1022) Mount `/node5'.
More secure alternatives include: supper. Secure NFS and NIS+ use the more secure AUTH_DES method. nightly mksysb backups to the control workstation. If you are dependent upon having NFS active within the SP environment.3 Network Information Services (NIS and NIS+) Guide. in an SP environment. Network Information Service (NIS) Overview for System Management in AIX Version 4. if you load the nfs utility. Newer alternatives to NFS and NIS are Secure NFS and NIS+. make sure you set the permissions so that only root can run it.3. change this to read-only. By default. see Section 7. Second. private-key encryption. Secure NFS and NIS+ use Sun's RPC protocol. but its setup is not trivial. just as NFS and NIS do. but they differ in the authentication protocol used. see the system manual. the NFS export on AIX gives read-write access to all hosts. provides a secure way of sharing data (Secure NFS) and performing user management (NIS+). do not export file systems with root access unless absolutely necessary. run the help subcommand. This ensures proper authentication for all requests and. Protecting NFS With NFS. The AUTH_DES protocol used by Secure RPC employs DES-based. For more information about Secure NFS. Both supper and DCE user management are supported directly by PSSP. In most SP environments. Securing AIX 173 . Where possible. There are two lessons here.4 of AIX 4.If the /node5 file system had not been exported with root access.3 Elements of Security Effective and Efficient Implementation. therefore. DCE user management. SG24-5962. and explicitly specify only those hosts who need access to the directories on a directory by Chapter 8. PSSP uses NFS during node installation and customization. In an SP environment. avoid using NIS for user management because of the security exposure. The most straightforward way of doing this is with NIS+. and so on). NIS+ is included with AIX 4. be sure to limit it to only the internal SP networks (administrative Ethernet and switch) by being very explicit in your export list. To use Secure RPC. For more information about using the nfs utility. Also. For more information about setting up and administering NIS+. we would not have been able to view the file (aaa) with the nfs utility. NFS and NIS use the AUTH_UNIX method. you need to set up the public and private keys and create principals for all users.3.5. NFS is also used for normal day-to-day support activities (automounted home directories. and NIS+. public-key. the most common security mistake is exporting directories with excessive privileges. First.
The biod daemon handles client requests and runs on the NFS client (and usually also the NFS server).statd.) These daemons have been successfully exploited through buffer overflow attacks to gain root access on the system. Each are briefly described here: • Biod .statd. • Rpc.statd daemon provides crash recovery functions for the NFS locking services (provided by the rpc.The nfsd daemon services requests from clients for file system operations. rpc. NFS supports the UNIX advisory locking functions with the rpc. • Rpc.client.lockd and rpc. For example. If you are not running applications that require this locking functionality. see Chapter 6.mountd after all client mounts have successfully completed. NFS is started on system startup with the /etc/rc.lockd daemon).mountd . and specify the exports as low in the directory as possible. rpc.mound daemon answers requests from clients for file system mounts. disable rpc.directory basis. consider blocking the portmap port (port 111) at the firewall. To provide further protection. biod sends the request to NFS server.mountd. "Port and network scanning" on page 83. ensure that you are at the latest patch level for fileset bos. By default. (It is also possible to disable rpc. 174 Additional Security Tools for AIX Systems . nfsd. It is required when you mount an NFS file system. Export only the needed directories.The rpc. For more information about how to protect against port scanning attacks. If you do need them. You may still want to allow internal users to have portmap (and NFS) access while preventing it for external users. • Rpc.nfs.statd .lockd . you should also set up protection against port scanning. but this is much harder to do and runs the risk of causing additional problems for clients that need to remount the file systems.net. When a user (client) wants access to a file on an NFS-mounted file system.The rpc.The rpc.lockd and rpc. rpc. on an SP control workstation.statd daemon. the /spdata/sys1/install/pssplpp directory is exported to the nodes instead of the top-level /spdata directory.nfs script out of /etc/inittab.lockd. • Nfsd . Since attackers can still ferret out the fact that you are using portmap (and NFS) by scanning non-privileged ports (above 1023). NFS is comprised of five separate daemons: biod.lockd daemon processes lock requests for concurrent access to files. You should also keep an eye on the content in the directories that are NFS exported to ensure that no sensitive data is inadvertently exposed.
nfs.1.2.To disable rpc.2.7 Sendmail 8. 8.1 AIX 4. use the exportfs -u <directory> command.2.3.1. you should have as current a version as possible.7 Sendmail 8. Securing AIX 175 .lockd.3 Simple Mail Transfer Protocol (SMTP) In AIX.sendmail.7 Sendmail 8. For that reason.3.statd.8 Sendmail 8.0 AIX 4.lockd and rpc.org With AIX.4 Sendmail 8.9 The sendmail configuration file is /etc/sendmail.3.8 Sendmail 8. and stop the daemons (in the order shown): # stopsrc -s rpc. AIX versions of sendmail AIX version AIX 3.6.1 AIX 4. Sendmail has gotten a bad reputation for having had many security vulnerabilities in the past.2 AIX 4.4 AIX 4.4 Sendmail 5.5 AIX 4. To unexport a single directory. stopsrc -s rpc. the sendmail version you receive depends on the AIX version as shown in Table 5.4 Sendmail 5.0 AIX 4. and always keep it at the latest patch level. comment out their entries in /etc/rc. A wealth of information about sendmail can be found at the sendmail homepage: http://www. the default SMTP server software is sendmail. One of the most common security mistakes made with the configuration file is to allow the use of the VRFY and EXPN built-in commands.3.3.cf file: Chapter 8. Table 5. To unexport all directories in the /etc/exports file.cf.5 AIX 4.statd.6.3 Sendmail version Sendmail 5.6. use the exportfs -au command. These should be disabled by adding the following line in the /etc/sendmail.
To connect to the local sendmail daemon. and the timezone 176 Additional Security Tools for AIX Systems .3). the sendmail version (8.9.9. To include all of the above options in addition to the novrfy and noexpn options.O PrivacyOptions=noexpn.novrfy VRFY is used to verify names of valid users..3) that sendmail is running on this server.3/8. • goaway restricts SMTP status queries. This is a wealth of information for would-be attackers.itso.3. This is such a common security mistake that scan programs.9.com> Notice also how much information is provided by the Sendmail banner. Note: This option takes care of setting novrfy. Tue.4. and EXPN is used to obtain the actual delivery addresses.. we show both the VRFY and the EXPN commands.com ESMTP Sendmail AIX4. and needvrfyhelo. needmailhelo. It gives the version of AIX (4. add the following line to the /etc/sendmail. "Network Security Auditor (NSA)" on page 49).restrictmailq. Escape character is '^T'. Not only do these commands expose sensitive information to would-be attackers. needexpnhelo. such as NSA (Section 4. Connected to 0. They now know the operating system type (AIX). • restrictqrun restricts ordinary users from causing sendmail to process its queue.msc. There a couple of other security-related options that you might want to consider adding to the sendmail PrivacyOptions line: • restrictmailq restricts ordinary users from viewing the status of all queued mail. the operating system version (4. have built-in tests for it.3/8. 29 Aug 2000 17:08:15 -0500 vrfy khorck 250 <email@example.com file (instead of the one shown earlier): O PrivacyOptions=goaway.msc.ibm.msc. noexpn.9.restrictqrun In the following example.itso. 220 sp5en0.3) as well as the version of sendmail (8.3). Sendmail listens on TCP port 25. we simply telnet to port 25 on localhost (0): # tn 0 25 Trying.ibm. but they can sometimes also be used by the attacker to forge mail from the server. authwarnings.com> expn khorck 250 <firstname.lastname@example.com.
and then refresh the sendmail daemon for the changes to take effect. For the latter type of server.cf. $b The $v is AIX version. sendmail will always try to not run as Chapter 8. but taken together. sendmail supports the option to run as a user other than root. and look for the SMTPGreetingMessage line: O SmtpGreetingMessage=$j Sendmail $v/$Z. edit /etc/sendmail. the child forked by the sendmail daemon to process the request runs with the unprivileged ID. add the following two lines to your /etc/sendmail. when a connection is opened. Lets assume that you use postman for the user ID and group ID. Beginning with version 8.) By default. Taken individually.where the server is located. the problems involved with opening access to these files for the unprivileged sendmail ID outweigh the benefits. Securing AIX 177 . Note that sendmail in daemon mode still runs as root so that it is able listen on TCP port 25. and the $b shows the time and date (unless you have defined the macro). the $Z is sendmail version. each of these pieces of information is damaging enough. the unprivileged ID used by sendmail needs read access to the . However.8. In general. To set this up. we recommend that you create a special unprivileged user ID of either postman or mailnull and a matching group for the exclusive use of sendmail. This option is ideal for sendmail relays or hubs but does not work very well for servers with normal user accounts and access. This can reduce the impact of an attacker using a remote exploit to gain access to the local system through a sendmail vulnerability. However.cf file: O RunAsUser=postman:postman O DefaultUser=postman:postman The DefaultUser option is used by sendmail when it is unable to run as root and has no other choices. For that reason. Remove the fields as required. you should turn off the banner information.forward and :include: files owned by the normal users. this option should only be used on systems that are either dedicated sendmail servers or bastion hosts in a DMZ. Once these are created. The would-be attacker can now perform a simple search on the Web to find all known exploits for this version of sendmail running on this version of the operating system. the damage can be much worse. To remove it. (This option should be set even if you do not plan to use the RunAsUser option.
com). that is not allowed login privileges on the system.cf. 2.deadletter. One type of denial of service attack involves symbolically linking bogus files to system configuration files or system device files and then getting sendmail to overwrite them. However.root unless needed. As has already been mentioned. For example. consider setting the O SafeFileEnvironment option in /etc/sendmail.st /var/spool/mqueue 3.cf file: 178 Additional Security Tools for AIX Systems . you need to give the unprivileged sendmail id access to the sendmail queue: # chown postman /var/spool/mqueue Note that the commercial version of sendmail. Sendmail Switch (http://www. among other things. Important Do not run sendmail from the command line with the RunAsUser option because it may cause sendmail to lose its root authority. it does not need root to write to $HOME/. Consider setting this option as follows in the /etc/sendmail.cf /etc/sendmail. Change ownership of the sendmail files: # # # # chown chown chown chown mailnull mailnull mailnull mailnull /usr/sbin/sendmail /etc/sendmail. Redo the SUID to the unprivileged sendmail ID: # chmod 4511 /usr/sbin/sendmail If you are running sendmail on a server where users have shell access. you can still remove the root SUID from the sendmail executable: 1. you probably do not want to use the sendmail RunAsUser option on a server that has normal user account access. The SafeFileEnvironment option. automatically configures sendmail to run as an unprivileged user. with the RunAsUser option. ensures that the file being written to is a plain file (as opposed to a symbolic link or device file). such as mailnull. Additionally. Create an unprivileged user account.sendmail.
forward files of normal users. In addition.org/faq. always verify them with: # sendmail -v -bi Running this will alert you to any permissions errors on the files and directories needed by sendmail. You should also visit the sendmail homepage to get the latest security information as well as additional methods for securing sendmail.org.sendmail. Another security option that you can use with sendmail is the sendmail restricted shell (smrsh). For more information about setting up a chrooted environment for sendmail. there are tools. This enables you to control the programs that sendmail can execute. at http://www. With this special shell.27 of AIX Version 4. This is similar to smrsh but takes things a step further by completely disallowing sendmail any access outside of its own (chrooted) directory tree. This also seriously hinders the damage that a would-be attacker can cause by exploiting a hole in sendmail. Chapter 8.html).O SafeFileEnvironment=/ This causes sendmail to do the extra level of checking on the files but does not go so far as to require that all files to which it appends exist in a chrooted directory tree set up specifically for sendmail. that can set it up for you. you can restrict sendmail to a specific directory tree from which it can execute programs. Securing AIX 179 .sendmail.3 has various sendmail enhancements.html. Two special points of interest are the sendmail FAQ. such as the Firewall Toolkit (http://www.3. the attacker can execute arbitrary programs and issue commands as root on the system. AIX 4. look for the README file in the smrsh subdirectory. Whenever you make sendmail configuration changes.sendmail. which are covered in Section 7. at http://www.com/research/software/fwtk_over. It is also possible to run sendmail in a chrooted environment. There are numerous articles on the Internet about how to set this up. You can get more information about how to set up and use smrsh by downloading the latest sendmail source tree from ftp. SG24-2014. see Sendmail.3 Differences Guide. After expanding the distribution. Without it.tis. such as those that are specified in the . and the information about how to set up anti-spam measures.org/antispam. which limits sendmail to a specific directory tree. ISBN 1-5659-2222-0 (aka "The Bat Book").
You may also want to consider restricting access to SMTP TCP port 25. There are a number of ways of doing this. You can control direct access to the port by blocking it at the firewall, or you can block access to it at the server level with IPSec, which is included in the AIX 4.3 bos.net.ipsec fileset. For more information on IPSec, refer to Section 7.3 of AIX 4.3 Elements of Security Effective and Efficient Implementation, SG24-5962, and Chapter 9 of A Comprehensive Guide to Virtual Private Networks, Volume III , SG24-5309. A slightly different approach is to protect access to sendmail rather than just SMTP TCP port 25. One way to do this is by placing sendmail under the control of inetd, and protecting it with TCP Wrapper. For more information on how to do this, see Section 7.4.4 of Exploiting RS/6000 SP Security: Keeping it Safe, SG24-5521. It is also possible to just replace sendmail. One alternative is a product known as Postfix. Postfix is essentially a re-architecture of sendmail that was done with both security and speed in mind. The developer of Postfix, Wietse Venema, is also the developer of TCP Wrapper and SATAN. For more information about Postfix, see Section 7.4.4 of Exploiting RS/6000 SP Security: Keeping it Safe, SG24-5521. Postfix is available from:
(At one time, Postfix was know as IBM Secure Mailer; so, you may find additional information about Postfix under that name as well.)
8.3.4 Simple Network Management Protocol (SNMP)
AIX ships with SNMPv1. The only security mechanism supported by SNMPv1 is through the use of community names (see the /etc/snmpd.conf file). An SNMP community consists of one or more hosts grouped under a community name. The community name is used for authentication in the SNMP request packet. When a request is received, the SNMP agent verifies that the IP address of the host making the requests matches one of the hosts belonging to the community name. If the requesting host is a member of the community, the SNMP agent then determines if the requesting host is authorized for the requested access to the specified MIB. By default, AIX actively listens for SNMP requests on TCP and UDP port 161. Therefore, to further secure SNMP, you should change the community names from their defaults (such as public ) to names that are harder to guess. You should also disable MIB read and write permissions as much as possible.
Additional Security Tools for AIX Systems
8.3.5 Trivial File Transfer Protocol (TFTP)
TFTP is typically used to boot diskless workstations and network devices. It is basically a stripped-down version of FTP and has very little built-in security. TFTP uses UDP port 69. On SP systems, both tftp and bootps are required for node installation and customization activities. The following screen shows an example of tftp use within our lab environment. (Server sp5cw0 is the control workstation for the SP, and server arthur is a standalone server.):
[sp5cw0] $ cat /etc/tftpacces.ctl # PSSP and NIM access for network boot allow:/tftpboot allow:/usr/lpp/ssp allow:/etc/SDR_dest_info allow:/etc/krb.conf allow:/etc/krb.realms tn arthur ... [arthur] $ tftp sp5cw0 tftp> ? Commands may be abbreviated. Commands are: connect mode put get quit verbose trace status binary ascii timeout ? Connect to remote tftp Set file transfer mode Send file Receive file Exit tftp Toggle verbose mode Toggle packet tracing Show current status Set mode to octet Set mode to netascii Set total retransmission timeout Print help information
tftp> get /etc/krb.conf Received 36 bytes in 0.1 seconds tftp> quit
TFTP access control is provided through the /etc/tftpaccess.ctl file. The default TFTP access control for an SP system allows access to the /tftpboot directory, the /usr/lpp/ssp directory, the /etc/SDR_dest_info file, the /etc/krb.conf file, and the /etc/krb.realms file. Notice that from arthur, a standalone server that is completely unrelated to the SP system, that we were able to grab a copy of the /etc/krb.conf file without having to provide any authentication information whatsoever.
Chapter 8. Securing AIX
You may want to consider enabling tftp on the SP system only when it is needed for node installations or customizations. Of particular interest to a would-be attacker is the /tftpboot directory, which contains information about the nodes in the SP system. It is also a good idea to make sure that tftp access is blocked at your firewalls as well.
8.3.6 Securing X11
If you are running X11, you need to be especially concerned about security. An insecure X11 poses a major security risk. If access control is improperly set, attackers with simple programs (built on the X libraries) can capture keystrokes (such as account name, password, and other sensitive data), take control of the X windows display, and monitor the applications that are run. There are utilities available on the Internet that scan networks looking for active X servers, and, once found, attempt to connect to them for the sole purpose of monitoring and capturing keystrokes. In fact, utilities, such as xwd and xwud (found in the X11.apps.clients fileset), can be used to silently monitor a remote X server:
# xwd -root -display <server to be snooped>:0.0 > /tmp/tempfile # xwud -in /tmp/tempfile
X provides two forms of access control: • xhost - provides access control through IP address and/or host name • xauth - provides access control through cookies A comparison of the two can be found at:
Of the two, xhost is the more commonly used method for access control. Running xhost with out parameters lists the hosts that have been granted access to the X server. A fairly common user mistake is to issue the xhost + command. This disables all access control for the X server, which means that any host (even one belonging to an attacker) anywhere can connect to it. Once connected, programs, such as xwd, xwud, or worse, can easily be run to gather sensitive information and monitor activities. Some port scanners are able to detect that access control is turned off for an X server. For example, when NSA detects this, it reports it as follows:
o X server has no access control [port 6000].
Additional Security Tools for AIX Systems
If you want to secure the X server, start by running the xhost - command to turn on access control. You can safely run this command even if you are not sure if access control is already enabled. Running this command will not remove any existing connections, it will only prevent new, unauthorized connections from occurring. You can then augment your access control list by iteratively running the xhost + <hostname> for each additional host that is to have access to the X server. For example:
# xhost access control enabled, only authorized clients can connect # xhost access control enabled, only authorized clients can connect INET:loopback INET:merlinen0 INET:firewall LOCAL: # xhost +sp5cw0 sp5cw0 being added to access control list # xhost -sp5cw0 sp5cw0 being removed from access control list
You can obtain a finer grain of access control with xauth. For information on how to set this up, see The X Windows System Administrator's Guide, Volume 8, ISBN 0-9371-7583-8. Unattended workstations should always have their screens locked. This not only applies to PCs but also to workstations running X. The xlock command provides a password protected screen lock, and the xss command enables you to automatically activate the screen lock after some period of inactivity. These features are also built in to the CDE desktop. The X server uses TCP port 6000. This port should either be blocked at the firewall or filtered on the server with the IPSec facility (included in the AIX 4.3 bos.net.ipsec fileset). For more information on IPSec, refer to Section 7.3 of AIX 4.3 Elements of Security Effective and Efficient Implementation, SG24-5962, and Chapter 9 of A Comprehensive Guide to Virtual Private Networks, Volume III , SG24-5309. Terminal emulators are another area of concern for security and X. When using xterm (or other similar terminal emulators), use the secure keyboard option activated from the main menu. To activate the main menu, place the mouse pointer in the terminal window, then hold down the control key and mouse pointer button simultaneously. Once activated, the secure keyboard
Chapter 8. Securing AIX
option directs all keyboard inputs to the xterm command only, thus, preventing keystroke snooping. When secure keyboard is activated, the xterm foreground and background colors are interchanged to provide a visual reminder that the option is in force. Be aware that only one X client at a time can use this option, so you will need to enable and disable it as you move from X client to X client. For more information on the secure keyboard option, see the xterm man page. Also, note that the secure keyboard option does not protect against network sniffing since user ids and passwords are still transferred in the open. To protect against this, you can run X over SSH. For more information on SSH, see Section 5.1, "Secure Shell (ssh)" on page 59.
8.3.7 File Transfer Protocol (ftp)
The ftp protocol is used for transferring files between two hosts. As mentioned in Section 5.1, "Secure Shell (ssh)" on page 59, ftp transfers passwords (for authentication) in the open without encryption and is, thus, susceptible to spoofing. As such, running ftp over the Internet poses a huge security risk. Your first, best option is to replace ftp with a more secure variant. If that is not possible, steps should be taken to further secure ftp. If possible, consider using sftp or scp from the SSH package to replace ftp. SSH is based on a public-key, private-key authentication scheme and provides encryption for secure communication channels. Refer to Section 5.1, "Secure Shell (ssh)" on page 59 for more details. Another option is to protect ftp with TCP Wrapper. TCP Wrapper provides access control to services (such as ftpd) controlled by the inetd daemon (/etc/inetd.conf). Refer to Section 5.2, "TCP Wrapper" on page 77, for more details. By default, the ftp command displays a banner of information when run:
# ftp sp5cw0 Connected to sp5en0. 220 sp5en0 FTP server (Version 4.1 Sun Jul 9 18:28:14 CDT 2000) ready. Name (sp5cw0:root):
Of particular interest to would-be attackers is the ftp version information. Lists of vulnerabilities are readily available on the Internet. With the banner information in hand, the attacker can then tailor the attack to that specific version of ftp, saving many hours of trial and error. You can remove the banner as follows:
Additional Security Tools for AIX Systems
220 sp5en0 FTP server ready.. In active ftp. There are two different ways in which SOCKS can be implemented to further secure ftp.2. Securing AIX 185 . With active ftp. one for control and one for data...cat /usr/lib/nls/msg/en_US/ftpd.. "signal: %m" 9 "%s FTP server ready. or the ftp client can be socksified.geek-speak.msg $delset 1 $set 1 $quote " . Passive ftp prevents this from happening. .cat /tmp/ftpd.net/ftp/ftp1. For more information on the differences between active and passive ftp. Some organizations require that only passive ftp be allowed. it is possible for a malicious ftp server on the Internet to open a data port on an internal server for attack purposes.html Another alternative for ftp is to use SOCKS (see Section 2.msg # vi /tmp/ftpd. For passive ftp to work. visit: http://www. ftp uses two channels.. both ftp server and ftp client must support it.2.3. the client initiates the data channel. The ftp server code in AIX supports both active and passive modes. Name (sp5cw0:root): There are two modes of ftp: active and passive.cat Here is how it looks after the banner replacement: # ftp sp5cw0 Connected to sp5en0. Socksified clients are the more common solution. as does the AIX 4. You can obtain a socksified ftp client (rftp) from Chapter 8.# dspcat -g /usr/lib/nls/msg/en_US/ftpd. In passive ftp.msg # cp -p /tmp/ftpd." . For any file transfer. Passive ftp is the mode which is supported by most Web browsers and many GUI-based ftp clients. "Circuit level firewalls" on page 15) as a security measure. Active ftp is the default in AIX.cat > /tmp/ftpd. # gencat /tmp/ftpd. the server initiates the data channel..3 ftp client code (via the passive subcommand). Either the TCP stack can be socksified.
SOCKS also enables you to define your own IP address ranges (such as 192. There are also socksified ftp clients incorporated in Web browsers.raleigh.3.) The advantage of a socksified TCP stack is that you do not need to replace your clients. and ICMP behave on an AIX machine.8 Protecting TCP services using SOCKS SOCKS is a common means for clients behind a firewall to connect to servers on the Internet.com/IBM/socks/AIX/bin/. (There are AIX versions available for download from the Bull site. SG24-2014.4 Step 3: Set proper network (no) options Network options control how TCP.3 contains support for automatic socksification (SOCKS v5). UDP. Configuration can be found in the AIX Version 4. "Protecting TCP services using SOCKS".130. SOCKS is also more generalized with little limitation on the supported protocols (dependent.3. Among other things. SOCKS protects the clients by hiding their IP addresses from the servers on the Internet.8. refer to the following. you will still need access to a SOCKS server. You use the no command to configure network attributes.0) for machines behind the firewall. such as rftp for ftp. The changes you make are dependent on the level of security required for your environment.3. you will also need access to a SOCKS server. They automatically and transparently make use of the SOCKS support provided in the TCP stack. on the specific SOCKS implementation).3 Differences Guide. Default settings are insufficient for the Internet world. SOCKS servers are similar to proxy servers. Some of the default settings need to be changed in order to further tighten security on the machine. 8. The options along with their default settings (for AIX 4. and rtn for tn. 8. To socksify the entire TCP stack. To use SOCKS. 186 Additional Security Tools for AIX Systems . Section 8. There are a number of socksified clients available for AIX. of course. you either need a socksified client or a socksified TCP stack. To use these clients.ibm.ftp://isscftp. such as Netscape or Internet Explorer. whereas a proxy server actually performs the functionality on behalf of the client. rtelnet for telnet. Even with a socksified TCP stack.3) are explained here to help you make those choices. AIX 4.3. since these IP addresses do not need to be registered externally.168. Only the Internet-facing IP address of the firewall is exposed to the servers. The main difference is that a SOCKS server identifies the user and redirects the application through to the server.
net/denial-of-service/white-papers/smurf. thus. When the server receives the SYN packets. the spoofed IP address must not be reachable by the server. Chapter 8. the client sends a SYN packet (TCP packet with SYN bit set) to the server. to halt. a client with a spoofed IP address sends many repeated SYN packets to the server. Smurf attacks are another form of denial of service attacks. This is a denial of service attack because once the connection table is full. In a SYN attack. In a legitimate 3-way TCP/IP handshake. Smurf attacks occur when a client sends huge amounts of spoofed ICMP traffic to the broadcast addresses. The routers should be configured to not allow ICMP echo packets from the Internet to reach the broadcast addresses. in extreme cases. each host on the network will respond with an ICMP echo reply. Securing AIX 187 . However. the client acknowledges the SYN/ACK packet with an ACK packet. Since the spoofed IP address is unreachable. More information on smurf attacks can be found at: http://www. the server is unable to service legitimate requests. This worthless network traffic wastes bandwidth causing normal operations to slow or. it responds by sending the SYN/ACK packets back to the spoofed IP address.4. the server never receives the corresponding ACK packets in return.1 SYN attack protection The clean_partial_conns option is used to avoid SYN attacks.2 Broadcast protection The bcastping option is used to control the response to ICMP echo packets directed at the broadcast address.pentics. reducing the likelihood of a successful SYN attack and allowing legitimate client connections to proceed. Setting clean_partial_conns to 1 (the default is 0) causes the server to periodically clear incomplete 3-way handshake connections. Systems are vulnerable to smurf attacks when bcastping is enabled. and the pending connection table on the server eventually fills up. With broadcast address ping allowed.cgil Setting bcastping to 0 (the default is 0) causes the hosts to not respond to broadcast ping requests. 8.4. smurf attack are more effectively dealt with by routers. For this attack to work. Finally.8. The server replies with a SYN/ACK packet. This completes the 3-way handshake.
you should set ipforwarding to 0 (the default is 0) unless the server is acting as a gateway. Setting the no options as outlined prevents source routing control from external sources. • Set icmpaddressmask to 0 (the default is 0). Lastly. the following no options should be set to prevent illegal access through source routing: • Set ipsendredirects to 0 (the default is 1). The recommended alternative is to set ipignoreredirects to 1 (the default is 0) and add static routes. • Set ipsrcrouterecv to 0 (the default is 0).3 IP routing options The ipignoreredirects option is used to control ICMP redirects. 8. Note that for SP systems. add only static routes and do not allow routes to be dynamically set by dynamic routing daemons (that can be abused). • Set udp_pmtu_discover to 0 (the default is 0). When servers or routers find a more efficient way of routing packets. This solution also requires the Topology Services daemon to prepare an all-known-IP list for netmonAdapterHealth. For maximum security. Similarly. the control workstation for a large SP 188 Additional Security Tools for AIX Systems . they send back ICMP redirect packets to the originating host informing it of the more efficient route. the hats topology daemon requires bcastping to be set to 1 unless APAR IX86922 has been installed throughout the SP system. Source routing attempts to control the path through the network to the destination. This opens a potential security loophole because it can be used to alter a legitimate route to redirect traffic to an unintended destination.Similarly. • Set nolocsrcroute to 0 (the default is 0). • Set ipsrcroutesend to 0 (the default is 1). • Set ipsrcrouteforward to 0 (the default is 1). For example. • Set tcp_pmtu_discover to 0(the default is 0).4. • Set ip6srcrouteforward to 0 (the default is 1). directed_broadcast should be set to 0 (the default is 1) to prevent directed packets from reaching the broadcast address of a remote network through a gateway. It can be manipulated such that the source is directed to reach the destination through an insecure interface rather than a secure one.
for use by the IMN search engine • guest . it can certainly serve as an launch point for attacks on other servers. The default users that can be removed are: • uucp and nuucp . Unneeded default accounts are an open invitation to would-be attackers.5.for use with the imnadm account You can remove these users and groups as follows: Chapter 8. but you should also have some form of monitoring or auditing to ensure that it does not get inadvertently turned back on (set to 1). An attacker who has commandeered a legitimate user account is a very difficult animal to track and capture. They are usually not required and can be safely removed. Much better to have and enforce strong account policies so that the attacker never gains this toehold in the first place.1 Removing unnecessary default accounts By default. 8.system with multiple administrative Ethernet segments will typically have ipforwarding set to 1 so that traffic can pass from segment to segment. Remember that even though your server may not contain sensitive data.for use with the lpd account • imnadm . Not only should ipforwarding be turned off (set to 0). and tighten the default attributes for the remaining ones.for use by users without accounts on the system The default groups that can be removed are: • uucp . This setting is used to allow packets to pass from one interface to another in a dual-homed server. Securing AIX 189 .for use by the uucp protocol • lpd . once compromised.for use by the printing subsystem • imnadm . several users and groups are created on the system during installation.for use with the uucp and nuucp accounts • printq . 8. In this step we give recommendations about default accounts that can possibly be removed and account options that can be tightened up. It is a very big security concern on servers attached to two different networks (such as in a DMZ).5 Step 4: Tighten up user accounts Remove unnecessary default accounts. and insecure normal user accounts pose one of the most insidious threats to security on a system.
To be usable again. the account is locked. The user attributes along with the recommended and default settings are listed in Table 6. Once the number of retries is exceeded. done # for g in uucp printq imnadm.# for u in uucp nuucp lpd imnadm guest. group. verify the correctness of the user. They can either be set globally or on an individual user basis. AIX account attributes Attribute loginretries registry rlogin tpath ttys umask Recommended value 3 files false (for root) on tty0 (for root) 077 Default value 0 true nosak ALL 022 Descriptions of each of the attributes follows: loginretries This attribute controls the number of invalid login attempts before the account is locked. and the default stanza contains the global settings. The possible values are positive integers or 0 to disable it. This file is in stanza format. do rmgroup $g. 8. A setting in an individual user stanza overrides the corresponding setting in the default stanza. Table 6.2 Setting user attributes User attributes are set in the /etc/security/user file. do rmuser -p $u. and password files: # usrck -y ALL # grpck -y ALL # pwdck -y ALL These commands should be run on a regular basis to ensure consistency and detect problems. done Once you have removed these users and groups.5. the 190 Additional Security Tools for AIX Systems .
• notsh . Consider setting this attribute to tty0 (console) for root.When you log in you are always on the trusted path. but it also provides an audit trail with the /var/adm/sulog file.cfg file) is set true for the port you are logging into.notice the exclamation point preceding the terminal name). umask Chapter 8. • always . such as NIS. thus.The Secure Attention Key (SAK) key (^X^R) has no effect. A value of files means that the account will be administered with local files rather than remotely with something. The rlogin and telnet commands support this attribute. ttys This attribute controls which terminals can be used by this account. The possible values are: • nosak . registry This attribute controls where the account is administered. The possible values are true and false. • on . Note This attribute only takes effect if the sak_enabled attribute (in the /etc/security/login. Securing AIX 191 .The SAK key logs you out. rlogin This attribute controls whether or not the account can be accessed by remote logins. tpath This attribute defines the trusted path characteristics for the account. Terminals can either be explicitly allowed (tty0) or explicitly denied (!tty0 . Not only is this more secure.The trusted path is entered when the SAK key is hit. You can never be on the trusted path.account will need to be unlocked by the system administrator (smitty failed_logins). The value should be set to false for root. requiring users to use the su command from their normal user accounts to gain root access.
3 Securing root The root account requires special attention. Note For SP node installation and customization. It is useful for limiting the times when normal user activity can occur on the system. Examples include managing accounts.5. a value of 077 is recommended. itself. This functionality is covered in detail in Chapter 3 of AIX 4. performing backups. ensure that the umask is set to 022 (at least temporarily during the process). Two additional account attributes to consider are: expires This attribute defines the expiration time for the account. such as Tripwire). For example. it is possible to allow selected accounts to execute certain administrative commands without having to have access to root. In addition to the recommendations for securing normal user accounts. The first step is to limit access to as few people as possible.This attribute defines the default umask for this account. A good way to protect root is by disabling remote login for the account. where the account should expire at a known point in time in the future. the fewer the better. For tight security. It is specified as a three-digit octal mask. and rebooting the system. Because AIX accounts support the function of roles. logintimes This attribute defines the times when the account may be used.3 Elements of Security Effective and Efficient Implementation. you could use it to prevent normal users from logging in during regularly-scheduled maintenance windows. consider these additional recommendations for securing root: 192 Additional Security Tools for AIX Systems . 8. should be protected with some tool. such as classes or schools. This provides accountability through the audit trail in the /var/adm/sulog file (which. It is useful in situations. This option is critically-important for securing permissions within the file systems. SG24-5962. This forces the authorized users to first log in with their normal user accounts and then use the su command to gain root access.
4. The login herald is specified in the default stanza of the /etc/security/login. Securing AIX 193 . Disable remote root login (rlogin option set false in /etc/security/user).cfg file. Set up exceptionally strong passwords (see Section 8. and change them regularly.4 Other attributes The login herald should be modified to provide only the information needed for the actual sign on of the account. "Step 5: Set up strong password policy" on page 194). 3. 8. 2. telnet (sp5en0) AIX Version 4 (C) Copyrights by IBM and by others 1982.\n\r\rlogin: " The new herald can now be seen in the following telnet session: Chapter 8. the goal is to provide as little useful information to would-be attackers as possible. Use roles extensively to limit the number of accounts requiring root access. By default. login: You should remove the operating system type and version from the herald and replace it with something like the following: herald = "\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\nUnauthorized Access Prohibit ed. Allow direct root login from tty0 (console) only. the AIX herald proclaims the system to be running AIX Version 4. as can be seen in the following telnet session: Escape character is '^T'.6. 1996.1.5. Remember.
telnet (merlin) Unauthorized Access Prohibited. include the following line in the /etc/profile file: TMOUT=600 . the TMOUT and TIMEOUT environment variables should be set in the /etc/profile file.1 Modifying user password attributes The AIX attributes used to define strong password policy are contained in the /etc/security/user file. export readonly TMOUT TIMEOUT 8. The AIX attributes are listed in Table 7 on page 195 and discussed in the next section. 8. login: Notice how little useful information is revealed in the new herald. Lastly. Attributes specified for the default stanza apply globally but can be overridden for individual user accounts. These variables control how long the account can remain idle with no activity before being automatically logged off. "John the Ripper" on page 119). such as John the Ripper (see Section 7. you can use these attributes to force users (including root) to choose passwords that are difficult to guess and are not available in the standard UNIX dictionary. For example. to set these timeouts to 10 minutes (600 seconds).6. the attribute 194 Additional Security Tools for AIX Systems . However.Escape character is '^T'. Among other things. use of these attributes does not alleviate the need to run cracking tools.2. TIMEOUT=600 .6 Step 5: Set up strong password policy AIX provides a set of attributes that enable you to implement strong password policy on the systems.
by adding common computer terms. such as hostname ).name. Recommended values for password settings Attribute dictionlist histexpire histsize minage maxage maxexpired minalpha minother minlen mindiff maxrepeats pwdwarntime Recommended value /usr/share/dict/words 26 8 0 12 (5 for root user) 4 4 1 6 (8 for root user) 3 3 14 Default value Max value 0 0 0 0 -1 (no limit) 0 0 0 0 8 0 260 50 52 52 52 8 8 8 8 8 0 Descriptions of each of the attributes follows: dictionlist This attribute ensures that passwords are not words from the standard UNIX dictionary (under AIX. Securing AIX 195 . When passwords are changed. As root. which is part of the bos. Table 7. the default value. the recommended value. histexpire This attribute specifies the number of weeks before a user is allowed to reuse a password. In addition to the bos. neither of which get installed by default. and the max value for the AIX attributes are shown in Table 7. you can add or delete words from this file to tailor for your environment (for example. Chapter 8. you will also need the bos.data fileset).spell fileset (required for text processing).txt.data fileset. the dictionary file is checked to make sure that the chosen password is not contained in the dictionary. this is the /usr/shared/dict/words file.
The root password is exempt. minother This attribute specifies the minimum number of non-alphabetic characters that the password must contain. A smaller value limits the amount of time that an exposed or disclosed password can be used. to prevent the account from being compromised). such as root and members of the system group. Consider using smaller values for privileged users. maxage This attribute specifies the maximum number of weeks that can pass before a password must be changed. minalpha This attribute specifies the minimum number of alphabetic characters that the password must contain. There is debate about whether or not a rigid password expiration policy is a good thing. they will either pick something that is very close to the expired password or. More often than not. A user suddenly confronted with an expired password does not have the luxury of considering their choice for a new one at length. we recommend that you do not use this attribute. worse yet. Since it is common for there to be situations where a password must be changed immediately (for example.histsize This attribute specifies the number of password iterations required before a user is allowed to reuse a password. These (other) characters are defined as any 196 Additional Security Tools for AIX Systems . minage This attribute specifies the minimum number of weeks that must pass before a password can be changed. This permits the user the time needed to consider a strong replacement for their current password. maxexpired This attribute specifies the maximum number of weeks beyond maxage in which a password can be changed (after which administrative action will be required to effect the change). The pwdwarntime attribute (described later) causes AIX to start warning the user shortly before the password is set to expire. something trivial just so that they can get logged in to the system to do their work.
2. One such tool is John the Ripper. Our intent is to give you a representative sample of the tools that are available to help you with the various areas of security. maxrepeats This attribute specifies the maximum number of times a character can appear in the password. "John the Ripper" on page 119. If it is. mindiff This attribute specifies the minimum number of characters in the new password that must be different from the characters in the old password. The sum of 'minalpha + minother' should never be greater than 8. whichever is greater. pwdwarntime This attribute (specified in days) causes AIX to start warning the user that their password is about to expire. 8. Note The minimum length of a password is determined either by minlen or by the sum of 'minalpha + minother'. Securing AIX 197 . we cover a number of third-party security tools. then minother is reduced to '8 .minalpha'.2 Password cracker utility There are a number of good tools available that enable you to test the strength of passwords. 8. which is covered in detail in Section 7. To recap.ASCII printable characters that are non-alphabetic and not national language code points.7 Step 6: Install additional security tools Throughout this book. minlen This attribute specifies the minimum number of characters that the password must contain.6. the tools covered in this book are: • Check Point FireWall-1 Chapter 8.
you specify which servers 198 Additional Security Tools for AIX Systems . In one. For example. Only those services that are essential to the proper functioning of the organization should be allowed to cross the firewall. TCP Wrapper provides access control protection to the services that are under the control of the inetd daemon. such as sendmail. In the other. such as the ftpd and telnetd daemons. they also log illegal access attempts. It provides encryption. SSH is a secure replacement for less secure protocols. such as rsh. If you plan to use them beyond the evaluation period. authentication. Together with routers. but can even include things. This includes things. A brief summary of each is given here: Firewalls are an essential security enforcement mechanism. which are secure replacements for ftp and rcp.• IBM Secureway Firewall • SSH • TCP Wrapper • fping • nmap • SAINT • PortSentry • Tripwire • PGP • MD5 • John the Ripper Note A number of these tools are licensed products even though they are available for download on a "try before you buy" basis. and data integrity to ensure that remote hosts can communicate securely (even across the Internet). There are two different TCP Wrapper access control lists. providing a means of early warning for potential attacks. such as sftp and scp. you specify which servers are allowed access to which services. SSH and TCP Wrapper are used to secure remote access. Different implementations of SSH provide different sets of tools. some provide tools. they provide the first line of defense against attacks. thus. In addition to protecting the network. All others should be blocked. ensure that you have the proper licenses in place.
Securing AIX 199 . on a production network. A similar. the AIX version of the tool does not currently support protection against stealth scans. preventing access to any inetd controlled services that are protected by TCP Wrapper. Make sure you have the proper written authorization in place before running any of these tools on your systems. It is helpful to view the collection of fping. It is used to scan a large number of hosts looking for active services. These tools are invaluable for providing you with insight into what a would-be attacker sees when probing your network. which comes with IBM Secureway Firewall. Both are comprehensive tools for overall security auditing. The fping tool does a ping sweep of an entire network or range of IP addresses by quickly sending out ICMP echo requests and tracking the return responses. Run in concert with each Chapter 8. SAINT. nmap. The SAINT tool is another port scanner. and NSA as a suite of tools for proactively verifying the security of your network. you start by denying access to all services from all servers. NSA provides much more additional functionality. In addition to scanning for active services. SAINT produces a report of the potential vulnerabilities it found along with recommendations for fixing them. which quietly scans a server in a way that makes it very hard to detect. The nmap tool is a port scanner. Typically. The PortSentry tool provides protection against port scanners. thus. but the sum of the tools used together is much greater than the individual parts. PortSentry can automatically add the IP address of the suspected attacker to the TCP Wrapper /etc/hosts. Each tool brings with it its own set of strengths and weaknesses. The fping and nmap tools are network and port scanners. It is a good tool for verifying that the topology of your network is what you think it is and that hosts that should respond to these types of requests actually do respond. PortSentry can also be configured to kill the route (by aliasing it against the loopback adapter) to the suspected attack server.deny file. but requires a valid license from IBM to run it. It is an enhanced version of the SATAN tool. including stealth scan. Unfortunately. it also tests those services against a list of known vulnerabilities. and then grant access to individual services on a server-by-server basis.are denied access to which services. TCP Wrapper also provides logging of both successful and unsuccessful connection attempts. commercial tool is NSA. such as nmap. Important Many organizations have very strict policies in place against running certain types of tools. It supports many different scan techniques. such as sniffers and scanners.
This subject is further discussed in Section 7. it is extremely difficult.8 Step 7: Monitor logs. Remember that an attacker who has gained access to a legitimate user account is very hard to distinguish from the real user. you can create and enforce strong password policy. However. and system behavior Routine and regular system monitoring is another important aspect of security. it is still a good idea to use a tool. audit trails. tedious. forcing passwords to be changed on a regular basis. and ensuring that passwords are not chosen from words available in the dictionary. such as requiring passwords to meet certain criteria. these tools can cross-verify the results from the others. It enables them to secure sensitive information from others (including root) and to communicate securely with others. Having a strong password policy is one of the most important defenses you can have within your network. MD5 is a tool for verifying data integrity. John the Ripper is a password cracking tool.other. it is a commonly used method for ensuring that files downloaded from an Internet Web site have not been tampered with. 8. such as John the Ripper. and often impossible to ferret out the holes left behind by attackers. PGP provides encryption services for users of your systems. such as Tripwire. to proactively search for weak passwords. locally or remotely. Tripwire protects against this threat by means of a secure database containing a snapshot of the system configuration. Tripwire provides a means of verifying with a high degree of certainty that essential system files and directories have not been tampered with. Attackers usually leave backdoors and Trojan horses after compromising a system so that they can return to it in the future. "Ensuring the integrity of downloads" on page 136. and vulnerability lists. Like PGP. even with a policy like this in place. patches. Many Internet Web sites support it as a means of verifying that files downloaded from their site have not been tampered with. Without a tool. It is commonly used with email systems to provide secure authentication and data integrity for sensitive messages or files.1. Finding and correcting weak passwords is one good way to combat against this. Through it. With AIX. you are able to discover system breaches and attempted system breaches. It is a tool for assuring that system integrity has not been compromised. Be sure to keep the tools current with the latest versions. The various elements of this type of monitoring can be roughly categorized as follows: • Monitor system logs • Enable auditing 200 Additional Security Tools for AIX Systems .4.
/etc/security/failedlogin This file captures all failed login attempts. Often. the account that was the target of the command. You can access the information in this file by running the who command.• Monitor files and directories • Monitor cron and at jobs In addition to monitoring.8. You access this file with the last command.2 Enable auditing You can also set up system auditing to monitor security-related activities.1 Monitor system logs Regularly monitor the following logs for evidence of breaches or attempted breaches: /var/adm/sulog This file logs the use of the su command. 8. This file is especially important if you have disabled remote login for root because it tracks the accounts that are being used to gain (or attempt to gain) root access along with the time when the access was performed. a once secure network becomes insecure because someone introduces a change that inadvertently and unknowingly opens a security vulnerability. You can access the information in this file by running: who /etc/security/failedlogin | more /etc/utmp This file stores information about the users who are currently logged in to the system.8. Running regular security audits greatly reduces the risks posed by such activities. These tools help you ensure that your security posture remains unchanged. The information is kept in this file only until the acctcon1 and acctcon2 commands are run. It identifies the account that initiated the command. A list of pre-defined audit events can be found in the /etc/security/audit/events Chapter 8. /var/adm/wtmp This file stores information about current and previous system logins and logouts. and the time and date when the command was run. Securing AIX 201 . whether the command was successful or not. 8. you should also consider running regular scans with the security auditing tools described in the previous section.
netrc files because they expose user IDs and passwords in plain text.hup files Next. however. Scan these logs regularly for evidence of any suspicious activities.3 Monitor files and directories First. That is why it is so important to routinely monitor for these types of files. begin by cleaning up unneeded files.3 System Management Guide: Operating System and Devices. system activities are monitored and logs generated for the events that you have defined. it is possible to break out of it and run arbitrary commands as root. Once auditing is turned on.8. To find files owned by root with either the SUID or SGID bit set: # find / -perm -4000 -user 0 -ls # find / -perm -2000 -user 0 -ls You may also want to remove files with no owner. It is typically run from crontab on a daily basis.rhosts files because they enable unauthenticated system access and . set up routine monitoring and clean up of the following types of files (and directories): Executable files owned by root that have the SUID and/or SGID bit set can pose a serious threat to security. In addition. Examples of candidate files include: • files in the /tmp directory • files older than a specified age • a. which are typically caused by removing an account without removing the files belonging to that account. Be sure to get a baseline listing of these files on a newly-installed system so that you know which files have a legitimate need for these settings. These files execute with root authority regardless of who executes them. There are. Unless the code is rock solid. The skulker utility enables you to easily remove unwanted or obsolete files. and this is normal. To streamline the audit and limit the amount of generated data.out files • core files • ed. 8. which pose their own form of security risk. you may also want to remove . AIX system programs that require the SUID and/or SGID bits to be set. For more information about setting up auditing. 202 Additional Security Tools for AIX Systems . define just the events of interest to you. see "Setting up Auditing" in the AIX Version 4.file.
netrc -ls World-writable directories and files are also another potential area of security exposure. These commands enable attackers to plant time bombs on the systems and be long gone well Chapter 8.Important Under some HACMP configurations. do not remove the /.rhosts -ls To find . To find world-writable directories (monitor this list): # find / -perm -0007 -type d -ls To find world-writable files: # find / -perm -2 -type f -ls 8. /.netrc files: # find / -name . To find files with no user: # find / -nouser -ls To find . but. Again. Securing AIX 203 .8. ensure that the ownership is root. instead.system and that the permissions are set to 600.rhosts files.4 Monitor cron and at jobs Both cron and at are favorite hunting grounds for attackers. In those situations.rhosts files: # find / -name . you should get a baseline listing on a newly-installed system so that you can know which directories and files are normally required to be this way for the proper functioning of the system.rhosts files are required for the proper functioning of an HACMP cluster on AIX.
before they explode. you should be familiar with all of the jobs that are scheduled on your systems with cron or at. To monitor all cron jobs: # cronadm cron -l To monitor all at jobs: # cronadm at -l 204 Additional Security Tools for AIX Systems . For this reason.
53.69.6000-6063 udpports 1-1023 rpcsvcs * options tcp-seq-num options ftp-walk-tree options smtp-no-relay options smtp-require-reject. smtp-mail-from. 2000 205 .126.96.36.19900 udpports 53.111.25. smtp-mail-rcpt options nntp-no-post end define fulltcp tcpports 1-65535 udpports 53.1080.512-514. smtp-mail-rcpt options nntp-no-post end define standard tcpports 1-1023.79.109. smtp-mail-rcpt options nntp-no-post end © Copyright IBM Corp.22.23. smtp-mail-from. NSA Scan Options There are a number of scan options available in NSA (as documented in the /etc/nsa/scannerdefs file): define default tcpports 21.111.512-514.177 rpcsvcs * options ftp-walk-tree options no-user-login end define medium tcpports 21. smtp-mail-from.139.Appendix A.18.104.22.168.220.127.116.11.18.104.22.168.161.111.177 rpcsvcs * options tcp-seq-num options ftp-walk-tree options smtp-require-reject.23.137.177 rpcsvcs * options tcp-seq-num options ftp-walk-tree options smtp-no-relay options smtp-require-reject.22.69.177 rpcsvcs * options no-user-login end define baseline tcpports 21.6000 udpports 53.6000 udpports 188.8.131.52.220.127.116.11.22.214.171.124.111.22.110.
smtp-mail-from. ip-options options ftp-walk-tree. tcp-seq-num. ftp-no-mkdir options smtp-require-reject. ftp-no-wdir. ftp-no-mkdir options smtp-mail-from. ftp-no-wdir. smtp-mail-rcpt options smtp-no-relay options nntp-no-post end 206 Additional Security Tools for AIX Systems . smtp-mail-rcpt options nntp-no-post options smtp-no-relay end define firewall tcpports 1-65535 udpports 1-65535 rpcsvcs * options ip-source-route.define complete tcpports 1-65535 udpports 1-65535 rpcsvcs * options tcp-seq-num options ftp-walk-tree.
2.1.255. 2000 207 . Script used to scan a network with fping This script can be used with the fping tool to scan a whole network with netmask 255. © Copyright IBM Corp.255.0 as mentioned in Section 6. "Using fping" on page 86.Appendix B.
$ID2. do echo "$ID1. then echo "The default file to store list of hosts to scan is $datafile" echo "There is already a file named $datafile" echo "Do you want to remove it?[y(es)/n(o)]" read removeoutfile case "$removeoutfile" in y* | Y*) echo "Removing file\n" rm $datafile. esac fi echo "Obtaining list of hosts to scan and storing the list into $datafile" y=0 while [ "$y" -le 255 ]. scan 255 addresses if [[ $ID4 = "" ]] || [[ $ID4 -eq 0 ]]. *) echo "\nRerun program after renaming/removing that exit 0.#!/bin/ksh # # To scan a network with ffffff00 netmask # # Declare datafile to store list of hosts to scan datafile=/tmp/fping. .0\n" exit 0 fi ID1=`echo ID2=`echo ID3=`echo ID4=`echo $1 $1 $1 $1 | | | | awk awk awk awk -F -F -F -F .30. echo if [ $# -ne 1 ].16. . then tput clear echo "Please enter filename to output results" read outfile echo "Output file is $outfile\n" # Remove $datafile if it already exists." cat $datafile | /usr/local/bin/fping -sA > $outfile 2>&1 echo "View output file $outfile for results" else # If last octet is a host IP..$y" >> $datafile y=`expr $y + 1` done echo "\nScanning hosts now. Please wait for prompt to return.. then scan the host only /usr/local/bin/fping -sA $1 fi exit 0 208 Additional Security Tools for AIX Systems . if [ -f $datafile ]. '{print '{print '{print '{print $1}'` $2}'` $3}'` $4}'` # If last octet is the null string or 0. . then echo "Usage : $0 {Network address}" echo "Example : $0 172.$ID3.data tput clear.
as mentioned in Section 7. next. 1993.Appendix C.0 Password Cracking package. It was obtained from the Crack package (available at the Bull site). }' | sed -e 's/^PTAG://' © Copyright IBM Corp. print $0.0 and upwards. } $1 == "password" { print "STAG:" curruser $3. ### SHADOW=/etc/security/passwd PASSWD=/etc/passwd ( awk ' /^[a-zA-Z0-9]+:/ { curruser = $1. }' < $SHADOW sed -e 's/^/PTAG:/' < $PASSWD ) | awk -F: ' BEGIN { OFS=":". The John the Ripper tool requires a single password file. # # The copyright holder disclaims all responsibility or liability with # respect to its usage or its effect upon hardware or computer # systems. # 1992.2. 1995. and maintains copyright as set out in the "LICENCE" # document which accompanies distributions of Crack v5. 1994. #!/bin/sh ### # This program was written by and is copyright Alec Muffett 1991. next. 2000 209 . } $1 == "PTAG"{ $3 = pw[$2]. and is provided as part of the # Crack v5. } $1 == "STAG" { pw[$2] = $3. "John the Ripper" on page 119. Script to merge the AIX passwd files This script merges the /etc/passwd and /etc/security/passwd files. and 1996.
210 Additional Security Tools for AIX Systems .
600A. IBM may have patents or pending patent applications covering subject matter in this document.Appendix D. References in this publication to IBM products. subject to appropriate terms and conditions.3 or PSSP 3. payment of a fee. Special notices This publication is intended to help an RS/6000 AIX or SP/Cluster Specialist who wants to implement additional security tools other than those provides by IBM AIX 4. Mail Drop 1329.3. The information in this publication is not intended as the specification of any programming interfaces that are provided by IBM AIX and PSSP software products. Any functionally equivalent program that does not infringe any of IBM's intellectual property rights may be used instead of the IBM product. The furnishing of this document does not give you any license to these patents. program. program or service. You can send license inquiries. program. Dept. there is no guarantee © Copyright IBM Corp. or service is not intended to state or imply that only IBM's product. NY 10589 USA. Somers. to the IBM Director of Licensing. and is limited in application to those specific hardware and software products and levels. 2000 211 . in writing. Such information may be available. Information in this book was developed in conjunction with use of the equipment specified. NY 10504-1785. Licensees of this program who wish to have information about it for the purpose of enabling: (i) the exchange of information between independently created programs and other programs (including this one) and (ii) the mutual use of the information which has been exchanged. While each item may have been reviewed by IBM for accuracy in a specific situation. Armonk. The use of this information or the implementation of any of these techniques is a customer responsibility and depends on the customer's ability to evaluate and integrate them into the customer's operational environment. including in some cases. See the PUBLICATIONS section of the IBM Programming Announcement for IBM products mentioned in this redbook for more information about what publications are considered to be product documentation. The information contained in this document has not been submitted to any formal IBM test and is distributed AS IS. should contact IBM Corporation. Any reference to an IBM product.2. IBM Corporation. North Castle Drive. programs or services do not imply that IBM intends to make these available in all countries in which IBM operates. or service may be used.
in the United States and/or other countries. PC Direct is a trademark of Ziff Communications Company in the United States and/or other countries and is used by IBM Corporation under license. in the United States.. Any pointers in this publication to external Web sites are provided for convenience only and do not in any manner serve as an endorsement of these Web sites. The following terms are trademarks of the International Business Machines Corporation in the United States and/or other countries: e (logo)® Netfinity Redbooks Logo RS/6000 SecureWay SP1 TCS IBM Redbooks RISC System/6000 SAA SP System/390 The following terms are trademarks of other companies: Tivoli. ActionMedia. Planet Tivoli.TME. C-bus is a trademark of Corollary.The Power To Manage. Windows. or both. and the Windows logo are trademarks of Microsoft Corporation in the United States and/or other countries. an IBM company. Windows NT. Anywhere. Pentium and ProShare are trademarks of Intel Corporation in the United States and/or other countries. and Tivoli Enterprise are trademarks or registered trademarks of Tivoli Systems Inc. UNIX is a registered trademark in the United States and other countries 212 Additional Security Tools for AIX Systems . other countries. LANDesk.Tivoli A/S. Tivoli Ready. Manage. Cross-Site. Anything. MMX. Anywhere... Tivoli Certified..that the same or similar results will be obtained elsewhere. in the United States and/or other countries. In Denmark. Java and all Java-based trademarks and logos are trademarks or registered trademarks of Sun Microsystems. Inc. Microsoft. Tivoli is a trademark licensed from Kjøbenhavns Sommer . Customers attempting to adapt these techniques to their own environments do so at their own risk. Inc. NetView. Anything.
SET Secure Electronic Transaction. Special notices 213 . and the SET Logo are trademarks owned by SET Secure Electronic Transaction LLC. and service names may be trademarks or service marks of others. SET.licensed exclusively through The Open Group. Appendix D. Lotus Notes is a registered trademark of Lotus Development Corporation Other company. product.
214 Additional Security Tools for AIX Systems .
SG24-2014 • AIX 4. updates and formats. SG24-5521 • Safe Surfing: How to Build a Secure WWW Connection. Click the CD-ROMs button at ibm.com/redbooks for information about all the CD-ROMs offered.Appendix E. SG24-5309 • A Secure Way to Protect Your Network: IBM SecureWay Firewall for AIX V4. E.1 IBM Redbooks For information on ordering these publications see "How to get IBM Redbooks" on page 221.2 IBM Redbooks collections Redbooks are also available on the following CD-ROMs. • A Comprehensive Guide to Virtual Private Networks. 2000 215 .3 Differences Guide. SG24-5855 • AIX Version 4.3 Elements of Security Effective and Efficient Implementation. Related publications The publications listed in this section are considered particularly suitable for a more detailed discussion of the topics covered in this redbook.1. GG24-3376 E. CD-ROM Title Collection Kit Number IBM System/390 Redbooks Collection SK2T-2177 IBM Networking Redbooks Collection SK2T-6022 IBM Transaction Processing and Data Management Redbooks Collection SK2T-8038 IBM Lotus Redbooks Collection SK2T-8039 Tivoli Redbooks Collection SK2T-8044 IBM AS/400 Redbooks Collection SK2T-2849 IBM Netfinity Hardware and Software Redbooks Collection SK2T-8046 IBM RS/6000 Redbooks Collection SK2T-8043 IBM Application Development Redbooks Collection SK2T-8037 IBM Enterprise Storage and Systems Management Solutions SK3T-3694 © Copyright IBM Corp. SG24-4564 • TCP/IP Tutorial and Technical Overview. SG24-5962 • Exploiting RS/6000 SP Security: Keeping It Safe. Volume III .
postfix.purdue. ISBN 1-5659-2148-8.ssh.security How to Build a Secure World Wide Web Connection.faqs.org • http://www.ssh. and Deborah Russell • Firewalls and Internet Security: Repelling the Wily Hacker.edu/coast/satan.com • http://www.E. by D. Elizabeth D. ISBN 0-6717-2688-9. ISBN 1-5659-2222-0 • The Art of War.net • http://wuarchive. ISBN 0-3852-9216-3. ISBN 0-1361-2409-7 E. ISBN 0-2014-3303-6.html • http://www.org • http://all. • Practial Unix and Internet Security. ISBN 0-0609-2694-5. by Michele Slatalla and Joshua Quittner. ISBN 0-0721-2748-1 • Information Warfare and Security. by Clifford Stoll • The X Windows System Administrator's Guide. ISBN 0-2016-3357-4 • Hacking Exposed: Network Security Secrets and Solutions.edu/packages/security/TAMU/ • http://www.bull.3 Other resources These publications are also relevant as further information sources: • Building Internet Firewalls. Denning • Masters of Deception: The Gang That Ruled Cyberspace. by Simson Garfinkel and Gene Spafford • Sendmail. Brent Chapman. ISBN 0-9371-7583-8 • Www.wustl.cerias.org • http://www. by Sun Tzu • The Cuckoo's Egg: Tracking a Spy Through the Maze of Computer Espionag.4 Referenced Web sites The following Web sites are also relevant as further information sources: • http://www.org/faqs/kerberos-faq/general/ 216 Additional Security Tools for AIX Systems . ISBN 1-5659-2124-0. by Dorothy E. Volume 8. Zwicky.
ccc.iana.postfix.edu/kerberos/www/dialogue.html/ • The Internet Assigned Numbers Authority: http://www.bull.org Appendix E. not a hacker site: http://www.purdue.ice.org/ • Large archive of SMIT installable freeware: http://www.org • Fred Cohen's page.radium.ssh.cerias. large download area with hacker tools and security tools: http://packetstorm.itsec.net • Chaos Computer Club (partly German): http://www.html/ • Information Technology Security Evaluation Criteria (ITSEC) Assurance Level Criteria: http://www.edu.org • IBM emergency response team: http://www.securify.tw/os/unix/security/ • The Admin guide to cracking by Dan Farmer and Wietse Venema: http://www.ntnu.html/ • Trusted Computing System Evaluation Criteria (TCSEC) Rainbow Series Library: http://www.redbooks.edu/coast/satan-html/docs/admin_guide_to_crack ing.gov.attrition. replacement for sendmail: http://www.com • This is a security site.uk/ • Wietse Venema's (author of tcp_wrapper) tools and papers: http://sneezy.com/ • Designing an Authentication System: a Dialogue in Four Scenes: http://web.ncsc.de/pub • Secure Shell hompage: http://www.cert.ibm.org • Computer Emergency Response Team: http://www. Related publications 217 .mil/tprep/library/rainbow/index.• IBM Redbooks: http://www.ers.com • Postfix homepage.de • Security information.ibm.mit. programmer of the Deception Toolkit: http://all.
com/pub/ssh/ • http://www.com/abacus/ • http://www. • http://www.au/~roca/ttssh.sanstore.txt • www.psionic.porcupine.insecure.com/univercd/cc/td/doc/product/iaabu/centri4/user/scf4ch3.f-secure.com/ • http://www.com • www.enteract.com/supplements/99poy_win/99poy_s.cisco.enteract.fc.ssh.org/pub/security/index.com/support/technical/documents/index.html • ftp://ftp.mimesweeper.cyberarmy.openssh.html • http://www.com • http://www-frec.bull.html.com/software/security/firewall/ • www-4.com/products/securecrt/ • http://www.ibm.checkpoint.com/fw1 • www.infoworld.telemate.zip.org/ • www.com/software/network/dispatcher/ • www.com/~lspitz/fwtable.vandyke.htm • www.com • www.com/products/ssh/ • http://www.ibm.ssh.com/saint/index.html • http://www.ibm.net/phrack/files/p48/p48-13.fr • http://www.shtml • http://www.htm • www.html • www.wwdsi.ibm.com/t-50/index.com/ssh/download.ibm.phoneboy.ers.psionic.com.com/~lspitz/intrusion.html • ftp://ftp.onsight.com/abacus/portsentry/ 218 Additional Security Tools for AIX Systems .integralis.com/security/ • http://www-4.html • www.com/faq/ssh/ssh-faq.html • http://www-3.org/nmap • http://www.com/software/security/firewall/about/ • www.checkpoint.net • http://www-4.• Top 50 security sites: http://www.
com/doc_link/en_US/a_doc_lib/aixgen/topnav/topnav.htm • http://www.tripwiresecurity.sendmail.com/ • http://www.org/faq • http://www.com • http://www.sendmail.cfml • http://www.org • http://www.com/products/index.sendmail.• http://www.com • http://www.org/products/BIND/ • www.com/abacus/logcheck/ • http://www.html Appendix E.tripwiresecurity.pgpi.com • http://www.com • http://www.org/antispam.pgpinternational.dictionary.com • www. Related publications 219 .bull.sendmail.psionic.com • http://www.de/pub/out/ • http://www.ibm.pgp.org/doc/faq/pgpi/en/#International • http://www.pgpi.nai.isc.rs6000.
220 Additional Security Tools for AIX Systems .
• Redbooks Web Site ibm.com/ and clicking the ITSO Mailing List button. • E-mail Orders Send orders by e-mail including information from the IBM Redbooks fax order form to: e-mail address In United States or Canada Outside North America • Telephone Orders United States (toll free) Canada (toll free) Outside North America 1-800-879-2755 1-800-IBM-4YOU Country coordinator phone number is in the "How to Order" section at this site: http://www. The latest information may be found at the Redbooks Web site.ibm. view.ibmlink.ibm. 2000 221 .ibm.elink. and CD-ROMs. and workshop announcements. or order hardcopy/CD-ROM Redbooks from the Redbooks Web site.com Contact information is in the "How to Order" section at this site: http://www. Look in the Materials repository for workshops. IBM Intranet for Employees IBM employees may register for information on workshops. redpieces.com/ for redbook.elink. click the Additional Materials button.com/redbooks Search for. A form for ordering books and CD-ROMs by fax or e-mail is also provided.ibmlink.com/pbl/pbl This information was current at the time of publication. residencies. not all Redbooks become redpieces and sometimes just a few chapters will be published this way. and Web pages developed and written by the ITSO technical professionals. Also read redpieces and download additional materials (code samples or diskette/CD-ROM images) from this Redbooks site. © Copyright IBM Corp. download.itso. residency. but is continually subject to change. Redpieces are Redbooks in progress.ibmlink. The intent is to get the information out much quicker than the formal publishing process allows. papers.com/pbl/pbl • Fax Orders United States (toll free) Canada Outside North America 1-800-445-9269 1-403-267-4455 Fax phone number is in the "How to Order" section at this site: http://www. and Redbooks by accessing the IBM Intranet Web site at http://w3.com/pbl/pbl pubscan@us. presentations.elink.ibm. Employees may access MyNews at http://w3.ibm.How to get IBM Redbooks This section explains how both customers and IBM employees can find out about IBM Redbooks.ibm.
and Visa. Payment by credit card not available in all countries.IBM Redbooks fax order form Please send me the following: Title Order Number Quantity First name Company Address City Telephone number Invoice to customer number Credit card number Last name Postal code Telefax number Country VAT number Credit card expiration date Card issued to Signature We accept American Express. Signature mandatory for credit card payment. Master Card. Diners. 222 Additional Security Tools for AIX Systems . Eurocard.
netrc 202 .clean 145 /etc/tftpaccess. 71 $HOME/.shosts 68 /.ssh/known_hosts2 72 $JOHNDIR/john. 68. 70 /etc/inetd. 157 /etc/SDR_dest_info 181 /etc/security/audit/events 201 /etc/security/failedlogin 201 /etc/security/login. 194 /etc/sendmail.dt 144 /etc/rc.6/words. 161 /etc/nsa/license. 144.conf 43 $FWDIR/log 29 $HOME/.pub 74 $HOME/. 142.conf 180 /etc/ssh/known_hosts 68 /etc/tcp.skr 129 $HOME/. protecting with Tripwire 144 /etc/rc.allow 79 /etc/hosts.ssh/identity 70 $HOME/.lst 121 /usr/local/lib/john-1.sort 122 /usr/local/lib/tripwire-1.forward 177 .st 178 /etc/shosts.conf 43 $FWDIR/conf/fwopsec.tcpip 28.ssh/config 70 $HOME/.pub 72 /etc/openssh/sshd_config 68 . 202 .deadletter 178 .pgp/pubring. 178 /etc/sendmail. 70 /etc/snmpd.rhosts 60. 199 /etc/hosts.equiv 68. 160 /etc/named. 177. 69.conf 181 /etc/krb. 2000 223 . 69. 174 /etc/krb.deadletter 178 $HOME/.ssh/authorized_keys2 74 $HOME/.list. 159.db_ 112 /usr/adm/tcheck/tw.rhosts 203 /etc/exports 168.pot 123 (^X^R) 191 .ini 122 $JOHNDIR/john.6/password.ssh/id_dsa 71.ctl 181 /etc/utmp 201 /spdata 174 /spdata/sys1/install/pssplpp 174 /tftpboot 181 /tmp 202 /usr/adm/tcheck/databases/ 118 /usr/adm/tcheck/databases/tw.cf 175.equiv 60. 168 /etc/profile 68.conf 43.ssh/known_hosts 68 $HOME/.local 28 /etc/rc.ssh/id_dsa.cfg 114 /etc/security/user 190. 72 /etc/passwd 122. 148 /etc/inittab 28.2/README. 74 $HOME/. 168 /etc/hosts.conf (BIND8) 158.prk 129 $HOME/. 193.pl 158 /usr/sbin/named 157 /usr/sbin/named4 157 /usr/sbin/named8 157 /usr/sbin/sendmail 178 /usr/security/bin/tripwire 112 /usr/share/dict/words 121 /usr/shared/dict/words 195 © Copyright IBM Corp.config 112 /usr/local/bin 68 /usr/local/bin/john 121 /usr/local/bin/john-1.rhosts 70 $HOME/.openssh 69 /etc/rc.realms 181 /etc/named.cfg 191.CheckConfig 115 /usr/local/man 68 /usr/lpp/FireWall-1/log 29 /usr/lpp/nsauditor/doc/ 50 /usr/lpp/ssp 181 /usr/samples/tcpip/named-booconf.nfs 174. 175 /etc/hosts 153.dt.pgp/secring.forward files 179 . 194 /etc/rc.ssh/authorized_keys 70. 193 /etc/security/sysck.Index Symbols !tty0 191 # 145 $FWDIR/conf/fwauthd.deny 79. 175 /etc/rc.net 28 /etc/rc.boot (BIND4) 158.shosts 70 $HOME/.nsa 50 /etc/nsa/scannerdefs 50 /etc/openssh/ssh_host_key 69 /etc/openssh/ssh_host_key.
x 157 AIX 4. X11 182 account expiration time. options example 160 allow-transfer. 38 attacks buffer overflow 153 attacks./usr/vac/bin/cc 170 /var/adm/sulog 191. 173 authentication 62. 191 AIX account roles 192 AIX herald.3. 196 mindiff 195. defining 192 account policies. threat 4 at 201. slave example 160 allow-update substatement 161 allow-update. master example 160 allow-transfer. 196 minalpha 195.tcp. 196 maxrepeats 195. strong 189 ACK packet 187 active ftp 185 additional security tools. 197 minlen 195. SYN 37. 196 maxage 195. 16 architecture of security framework 6 assessment.3 (with bos. 197 minother 195. 71 authentication methods. 191 AIX account atttibutes registry 190. 203 attack.3.2. defining 192 account login times.3. 191 umask 190. 201 /var/adm/wtmp 201 /var/spool/mqueue 178 Numerics 022 192 077 192 3DES 64. denial of service 152 attacks. 191 tpath 190.server 4. smurf 187 attributes. 192.3. 197 minage 195.13) 157 AIX 4. 72 3-way TCP/IP handshake 187 80/20 rule 3 A a. example 161 AllowUsers 75 alternatives to disabling DNS recursion 162 alternatives to SSH 77 always 191 anonymous FTP site for h2n 158 APAR IX86922 188 application layer (proxy) firewalls 15. disabling 193 AIX password settings dictionlist 195 histexpire 195 histsize 195.net.x 157 AIX 4. other 193 audit logs 200 AUTH_DES 173 AUTH_SYS 168 AUTH_UNIX 168. DNS versions 157 all-known-IP list 188 AllowGroups 75 allow-query substatement 163 allow-query. 196 maxexpired 195. RPC 168 224 Additional Security Tools for AIX Systems . example 163 allow-transfer substatement 159 allow-transfer.2.x 157 AIX account attributes expires 192 loginretries 190 logintimes 192 rlogin 190. 197 AIX versions of sendmail 175 AIX.out 202 access control. buffer overflow 152 attacks.x 157 AIX 4. TFTP 181 access control. 191 ttys 190. 196 pwdwarntime 195. installing 197 ADSM See TSM ADSTAR Distributed Storage Manager (ADSM) See TSM advertising name servers 164 advisory locking in UNIX 174 AIX /etc/inittab 142 network services 141 securing 139 AIX 3.1.
DHCP extension 146 bootpd 151 bootps 149. 25. 153 CDE and Tripwire 144 CDE desktop 183 CDE startup. 183 bos.tcp.net. 153 4.3.9 159 4. ftp 184 banner.1 156 8.client 174 bos.2 155 8.3 157 4.authoritative 163 authwarnings 176 autoconf6 147 automatic socksification support in AIX 4.9.net. 153.3.3. 157 BIND8 conversion script 158 configuration file 158 converting to BIND8 158 no longer supported 153 options no-fetch-glue 163 options no-recursion 162 secure_zone record 163 BIND8 153. ftp 184 banner. 157 allow-transfer substatement 159 allow-update substatement 161 configuration file 158 converting to from /etc/hosts 158 dynamic update capability 161 options fetch-glue no 163 options recursion no 162 biod 174 biod.nfs.3.net. HACMP 203 cmsd 153 Command lslpp 68 opensshd 72 Commands at 201.3 186 automounted home directories 173 B banner replacement. DNS 154 CAST 125 CDE 144.ipsec. 181 bos. restricting 163 cache.rte 15 bos.2.txt.tcp.spell 195 boundary routers 2 broadcast protection 187 buffer overflow attacks 152. 38. reliable 147 closing vulnerabilities during system startup 28 cluster. defined 174 blackholing. ipv4 157 8. 174 building a security framework 2 C cache update.2 (patch 5).ipsec 180. sendmail 176 Basic Networking Utilities See BNU bastion hosts 177 bcastping 187 Berkeley Internet Name Daemon See BIND biff 151 BIND 147.server 4.net. ipv6 157 homepage 153 symbolic link 157 BIND4 153. 37. disabling 144 CDE. uninstalling 144 chargen 152 Check Point FireWall-1 14.client 157. 49.net. 151.8.2. 24.2. 203 biff 151 bootps 149 225 .13 157 bos.9 xfrnets directive 159 4. 165 bos. 197 chmod 0000 /usr/sbin/dpid2 148 chmod 4511 /usr/sbin/sendmail 178 chrooted 179 circuit level firewalls 15 clean_partial_conns 187 cleanup rule 34 clear text 149 clock source. defined 156 Blowfish 64 BNU 151 bogus DNS update 155 bootp 146 bootp protocol.data 195 bos. ipv6 157 8. 26.1.
183 Common Desktop Environment See CDE communications daemons. 114 connections. 203 cronadm at -l 204 cronadm cron -l 204 delset 1 185 dspcat -g 185 egrep 122 exportfs -au 175 exportfs -u 175 ftp 148 fw 36 gencat 185 grpck 190 kloginl 149 kshell 149 last 201 lsof 144 make 170 netstat 44. 151 rpcinfo 168 rsh 148. 151 rtelnet 186 rtn 186 scp 148 sendmail -v -bi 179 sftp 148 showmount 170 smitty failed_logins 191 spray 152 ssh 148 ssh-keygen 71. 186 rlogin 148. unique SNMP 148 compartmentalized approach 23 compartmentalized firewall environment design 21 compartmentalized firewalls 35 Compartments 21 complementary software for FireWall-1 26 complimentary software for IBM Secureway Firewall 48 comstat 151 configuration file for BIND4 158 configuration file for BIND8 158 configuring and using SSH1 69 configuring and using SSH2 72 configuring and using Tripwire 112 configuring DNS 153 configuring John the Ripper 121 configuring remaining services 153 configuring TCP Wrapper 79 configuring Tripwire 112 . 76 su 201 talk 152 tcp.chmod 0000 /usr/sbin/dpid2 148 chmod 4511 /usr/sbin/sendmail 178 cron 201. delete 145 commercial version of sendmail 178 Commnads xhost . SNMP 180 community names. 73. 183 xlock 183 xterm 183 commands to find root SUID/SGID files 202 commands to remove default users and groups 189 comment out vs. 152 netstat -af inet 144 no 28. 165 on 152 opensshd 69 pgpe 132 pgpk 127 ps 152 pwdck 190 rcp 151 refresh -s inetd 149 rftp 185.clean 145 tcpdchk 80 tcpdmatch 81 telnet 148 tftp 149 usrck 190 who 201 who /etc/security/failedlogin | more 201 write 144 xauth 182 xhost 182 xhost + 182. 186 nsa 50 nslookup 159. viewing 36 converting from /etc/hosts to BIND8 158 converting from BIND4 to BIND8 158 COPS 119 core 202 counterfeit update requests 155 226 Additional Security Tools for AIX Systems . disabling 144 community names.
157 ndnpd-router 147 ndpd-host 147 network management 148 nfsd 174 pcnfsd 152 piobe 143 pop3d 153 portmap 144. 184. 198 info search 143 IPv6 147 krlogind 151 krshd 151 lpd 147 mrouted 148 multicasting 148 named 147. 168 print 143. 203 cronadm at -l 204 cronadm cron -l 204 cross-verify 200 cryptographic authentication in DNS 156 D daemons 144 autoconf6 147 biod 174 bootpd 151 communication 144 comstat 151 DHCP 146 dhcpd 146 dhcprd 146 dhcpsd 146 DNS 147 dpid2 144.tcpip dpid2 144 inetd 144 portmap 144 sendmail 144 snmpd 144 syslog 144 data integrity 65 database managers started in /etc/inittab 142 database. Tripwire 200 daytime 152 DCE 147 DCE user management 173 DCE/DFS 147 default accounts 189 default accounts. removing unnecessary ones 189 default daemons started by TCP/IP 144 default groups 227 . 148 email 153 fingerd 151 ftpd 148.statd 174 rshd 148. 151 routed 147 routing 147 rpc. 184 gated 147 hats 188 httpdlite 143 imapd 153 imnss 143 imqss 143 inetd 144. 148. 176 snmpd 144.covering tracks 5 crack 197 crack utility 197 cracking tools 194 creating a useful rulebase 34 cron 201.lockd 174 rpc.mountd 174 rpc. 151 rstatd 151 ruserd 151 rwalld 151 rwhod 148 sendmail 144. 175. 147 qdaemon 143 rexd 152 rexecd 151 rlogind 148. 148 sprayd 152 syslog 144 talkd 152 telnetd 148 tftpd 151 time 147 time synchronization 147 timed 147 uprintfd 144 uucpd 151 writesrv 144 xntpd 147 daemons started by default in /etc/rc.
extension of bootp protocol 146 dhcpd 146 dhcprd 146 dhcpsd 146 dictionary. 153 advertising name servers 164 allow-query substatement 163 alternatives to disabling recursion 162 cache 154 cache update. 19 . 20.lockd & rpc.statd 175 disabling services dt 144 httpdlite 143 imnss 143 imqss 143 piobe 143 qdaemon 143 uprintfd 144 writesrv 144 disabling TCP/IP daemons autoconf6 147 dhcpd 146 dhcprd 146 dhcpsd 146 dpid2 148 gated 147 lpd 147 mrouted 148 named 147 ndnpd-router 147 ndpd-host 147 routed 147 rwhod 148 snmpd 148 timed 147 xntpd 147 disabling the AIX herald 193 disabling time daemons 147 disabling VRFY & EXPN 175 discard 153 Distributed Computing Environment See DCE Distributed File System See DFS DMZ 3. disabling 146 DHCP relay daemon. restricting 163 checking version 157 configuring 153 cryptographically authenticated name servers 156 228 Additional Security Tools for AIX Systems . 189 public servers in DMZ.imnadm 189 printq 189 uucp 189 default stanza 190. 168. 7. world-writable 203 disabling CDE startup 144 disabling communications daemons 144 disabling DHCP daemons 146 disabling DNS daemons 147 disabling info search daemons 143 disabling IPv6 daemons 147 disabling multicasting daemons 148 disabling network management daemons 148 disabling print daemons 143. comment out 145 delset 1 185 demilitarized zone See DMZ denial of service attack 37 denial of service attacks 152. 193. 177. 195 dictionlist 195 difference between SSH1 and SSH2 62 digital signatures 156 directed_broadcast 188 directories. 35. private-key encryption 173 description of entries in /etc/inetd. dhcpsd 147 DHCP. public-key. 147 disabling routing daemons 147 disabling rpc. dhcpcd 147 DHCP daemons. private network in 2 DNS 147. standard UNIX 194. 161 DHCP client daemon.conf 150 DFS 147 DHCP 146. 194 default users guest 189 imnadm 189 lpd 189 nuucp 189 uucp 189 default webserver 143 DefaultUser 177 defining account expiration time 192 defining account login times 192 delete vs. 187 DenyUsers 75 DES 64 DES-based. dhcprd 147 DHCP server daemon.
defined 163 internal resolution name servers 164 IP address resolution steps 154 IP spoofing compared to DNS spoofing 156 nslookup 165 principles 154 protecting against spoofing exploit 156 queries. restricting 161 dynamic vs. 201 enabling other defense mechanisms 37 encryption 64 engine. restricting 161 referrals 162 resolvers 156 restrict cache update 163 restrict dynamic updates 161 restrict recursion 161 restrict zone transfers 159 restricting queries 162 securing on AIX 159 Security Extensions (DNSSEC). disabling 147 debugging with nslookup 168 determining version 157 DNS spoofing compared to IP spoofing 156 double lookup 156 dynamic updates. 155 spoofing exploit. static routes 147. 16 dynamic routes 188 dynamic routing 147 dynamic routing daemons 188 dynamic update capability in BIND8 161 dynamic updates. 188 E echo 152 echo packets. 148 dpid2 security exposure 148 DSA 62. explained 155 spoofing exploit. alternatives to disabling 162 recursion.hup 202 egrep 122 elements of security monitoring 200 email daemons 153 emergency response services (ERS) 10 enable auditing 200. restricting 162 recursion disabled 162 recursion. old and tired 154 Start Of Authority (SOA) record 166 TXT (txt) records 163 update. restricting 159 docsearch engine 143 Domain Name System See DNS dpid2 144. restricting 161 fetch-glue no option 163 finding version 157 glue fetching. docsearch 143 entries in /etc/inetd. defined 161 recursion.daemons. protocol extension 161 Dynamic Host Control Protocol See DHCP dynamic IP address assignment 146 dynamic packet filter firewalls 15. 64 dspcat -g 185 dt 144 dt entry in /etc/inittab 144 dtspc 153 dynamic DNS.conf 150 enumeration 5 environment variable TIMEOUT 194 environment variable TMOUT 194 etc/security/passwd 122 exec 151 expires 192 EXPN 175 EXPN. ICMP 187 ed. bogus 155 versions on AIX 157 with recursion disabled 162 zone transfers. RFC 2065 156 split configuration 164 spoofing 154. defined 176 exportfs -au 175 exportfs -u 175 external firewalls 2 external network 19 F Fast Mode TCP 42 favorite haunting ground 203 fetch-glue no (BIND8) option 163 fetch-glue no option in DNS 163 File Transfer Protocol See FTP Files 229 . protecting against 156 spoofing. new and improved 155 spoofing.
conf 148 inittab 142.conf 43 $HOME/.cfg 191. 175 /etc/rc.cf 175.shosts 68 /. 144. 142. 160 /etc/named.config 112 /usr/local/bin/john-1. 174 login.ssh/authorized_keys2 74 $HOME/.ssh/id_dsa 71. 71 $HOME/. 193 /etc/security/sysck.rhosts 70 $HOME/.ini 122 $JOHNDIR/john.pgp/pubring.out 202 cc 170 core 202 ed.pub 74 $HOME/.prk 129 $HOME/. 69. 148 /etc/inittab 28. 174 /etc/named.pot 123 . 168 hosts.boot (BIND4) 158.deadletter 178 .cfg 114 /etc/security/user 190.cfg 191.pl 158 /usr/sbin/named 157 /usr/sbin/named4 157 /usr/sbin/named8 157 /usr/sbin/sendmail 178 /usr/security/bin/tripwire 112 /usr/share/dict/words 121 /usr/shared/dict/words 195 /usr/vac/bin/cc 170 /var/adm/sulog 191. 74 $HOME/.db_ 112 /usr/adm/tcheck/tw.ssh/config 70 $HOME/.boot (BIND4) 158. 68.lst 121 /usr/local/lib/john-1.st 178 /etc/shosts.clean 145 /etc/tftpaccess.pub 72 /etc/openssh/sshd_config 68 .deadletter 178 $HOME/. 202 .deny 199 include 177 inetd.tcpip 28.pgp/secring. 159.forward 177. 160 named.ssh/identity 70 $HOME/. 161 /etc/nsa/license. 69.conf (BIND8) 158.conf 43 $FWDIR/conf/fwopsec. 193. 179 . 177.nsa 50 /etc/nsa/scannerdefs 50 /etc/openssh/ssh_host_key 69 /etc/openssh/ssh_host_key.$FWDIR/conf/fwauthd. 168 /etc/profile 194 /etc/rc.2/README.6/password.skr 129 $HOME/. 192.deny 79. 161 230 Additional Security Tools for AIX Systems . 194 /etc/sendmail.rhosts 203 /etc/exports 168.conf (BIND8) 158. 193 mqueue 178 named 157 named. 199 /etc/hosts.allow 79 /etc/hosts.ssh/authorized_keys 70.sort 122 /usr/local/lib/tripwire-1.ssh/known_hosts 68 $HOME/. 72 /etc/passwd 122.ssh/known_hosts2 72 $JOHNDIR/john.6/words.openssh 69 /etc/rc.conf 180 /etc/ssh/known_hosts 68 /etc/tcp.nfs 174.conf 43. 201 /var/adm/wtmp 201 /var/spool/mqueue 178 a. 178 /etc/sendmail. 168 /etc/hosts.equiv 60.hup 202 etc/security/passwd 122 events 201 exports 168.CheckConfig 115 /usr/lpp/FireWall-1/log/* 29 /usr/lpp/nsauditor/doc/ * 50 /usr/samples/tcpip/named-booconf.netrc 202 . 70 /etc/inetd. 157 /etc/security/audit/events 201 /etc/security/failedlogin 201 /etc/security/login. 175 /etc/hosts 153.dt 144 /etc/rc.rhosts 60.ssh/id_dsa.equiv 68.net 28 /etc/rc.list.shosts 70 $HOME/.local 28 /etc/rc. 159.ctl 181 /etc/utmp 201 /usr/adm/tcheck/databases/* 118 /usr/adm/tcheck/databases/tw. 70 /etc/snmpd. 175 failedlogin 201 h2n (BIND8) 158 hosts 153.
199 framework.tcpip 157 sendmail 178 sendmail.base 49 X11. securing 24 firewalls. 165 nsupdate 158 passwd 168 profile 194 rc. active 185 ftp.3.openssl.tcp.apps.rte 65 F-Secure SSH 62 FTP 184 ftp 148. 192.conf 180 sulog 191.httpdlite 143 nsaauditor. 193.porcupine. 198 //ftp.rte 65 freeware.net. 183 bos.txt. 16 misconceptions 13 on AIX 24 securing 24 static packet filter 15 types 15 firewalls on AIX 24 firewalls. 194 utmp 201 words 195 wtmp 201 files.clients 182 finding .st 178 snmpd.rte 65 freeware.net.client 174 bos.egd. socksified 185 ftp protocol 184 ftp.rte 15 bos.ssh.list.server 4. 175 rc.openssl.cf 175. 201 tcp.sort 114 tw. internal 2 firewalls.net. securing default configurations 29 firewalls 13.zlib. 184 fw 36 G gated 147 231 .13 157 bos.net.netrc files 203 finding . managing logs 29 FireWall-1.named4 157 named8 157 named-booconf. security 1 freeware.rte 65 freeware. passive 185 ftpd 148.egd. 178 sendmail. 198 application layer (proxy) 15.rte.ipsec.clean 145 tftpaccess.nfs 174.dt 144 rc. 165 bos.client 157.com/pub/ssh/ 61 ftp banner 184 ftp banner replacement 184 ftp client.compartmentalized 35 footprinting 4 fping 198. misconceptions 13 firewalls.pl 158 named-xfer 158 nslookup 159.org/pub/security/index.html 78 //ftp.rte 65 freeware.tcp.rte 65 IMNSearch.spell 195 freeware. world-writable 203 filesets bos.nfs.rhosts files 203 finding files with no user 203 finding root SUID/SGID files 202 finding world-writable directories 203 finding world-writable files 203 finger 151 fingerd 151 firewall design 17 firewall design 17 firewall hardening 49 Firewall Toolkit 179 FireWall-1 197 FireWall-1 features 25 FireWall-1.data 195 bos.zlib.ctl 181 tripwire. 177.config 115 user 190. external 2 firewalls.3.ipsec 180.net. 16 circuit level 15 comparison between different types 16 compartmentalized 35 compartmentalized environment design 21 default configurations 14 dynamic packet filter 15.
com/products/ssh/ 62 //www.com/ssh/download. firewalls 49 hats topology daemon 188 herald 193 High Availability Cluster MultiProcessing See HACMP histexpire 195 histsize 195.ers. 126 httpdlite 143 H h2n (BIND8) 158 h2n.gencat 185 gentle satirical imitation 154 glue fetching 164 glue fetching.rhosts 203 handshake. 184.org 12 //www.com/ssh 61 //www.bull 65 //www-frec.openssh.com 126 //www.nai.ibm. 196 hoax 154 homepages BIND 153 sendmail 175 host name resolution 153 host table.org/doc/faq/pgpi/en/#International 124 //www.com/products/index.fr 12.httpdlite fileset 143 imnss 143 implementation of security framework 7 implications of having SSH 77 implicit drop rule 34 imqss 143 include 177 incoming mail 151 inetd 144 inetd daemon 148.ssh.ssh.vandyke.pgp.com/ 111 //www. 199 IBM Secureway Firewall features 47 IBM Secureway Network Despatcher 48 ICMP 29.tripwiresecurity. TCP 3-way 187 hardening.bull.f-secure.ibm.rte.pgpinternational.com/products/securecrt/ 62 //www-3.com 126 //www.ibm. turning it off 163 goaway 176 grpck 190 guest 189 gzip 170 //www.sanstore. defined 163 glue fetching.com 10 //www.com 76 //www.ssh.openwall.com 61 //www.ibm. local 153 http //www.de/pub/out/ 111 //www.com/software/security/firewall/about/ 49 //www-frec.com 126 //www.html 61 //www. 198.com/software/security/firewall/ 47 //www-4.com 126 //www. anonymous FTP site for 158 HACMP 142.com/security/ 47 //www-4.pgpi. 186 ICMP echo packets 187 ICMP echo requests 199 icmpaddressmask 188 IDEA 64 imap2 153 imapd 153 IMN search engine 189 imnadm 189 IMNSearch. 61.cfml 111 I IBM Secure Mailer See Postfix IBM Secureway Firewall 47. 203 HACMP and /.pgpi.com/john/ 120 //www. 198 inetd entry bootpd 151 bootps 151 chargen 152 cmsd 153 comstat 151 daytime 152 discard 153 dtspc 153 echo 152 exec 151 finger 151 fingerd 151 imap2 153 232 Additional Security Tools for AIX Systems .tripwiresecurity. 49.bull.
imapd 153 klogin 151 krlogind 151 krshd 151 kshell 151 login 151 netstat 152 ntalk 152 pcnfsd 152 pop3 153 pop3d 153 ps 152 rexd 152 rexecd 151 rlogind 151 rshd 151 rstatd 151 ruserd 151 rwalld 151 shell 151 sparyd 152 systat 152 talk 152 talkd 152 tftp 151 tftpd 151 time 152 ttdbserver 153 uucp 151 uucpd 151 inetd. verifying 200 Internet Explorer 186 Internet Protocol (IP) version 6 See IPv6 interoperability between OpenSSH and SSH.Com 76 interpreting NSA output 51 intrusion detection on Check Point FireWall-1 43 IP address resolution steps in DNS 154 IP address.2 (patch 5) 157 IPv6 daemons. disabling 143 InfoExplorer 143 initial access 5 inittab 142 install additional security tools 197 installing John the Ripper 120 installing NSA 49 installing OpenSSH on AIX 65 installing TCP Wrapper 78 installing Tripwire 111 integrity. using 122 K Kerberos 151 kernel messages 144 kernel services. obtaining 120 John the Ripper. 180. 151 krlogind 151 krshd 151 kshell 149.9.2. private 2 Internet Boot Protocol server 151 Internet downloads. 197. 151 233 . 110. uprintf 144 key concepts of SSH 62 klogin 149. installing 120 John the Ripper.conf 148 infinite loop 152 info search daemons. 194. private 2 internal resolution name servers 164 internal servers. 188 ipforwarding on SP control workstation 188 ipignoreredirects 188 IPSec 7. 15. 183 ipsendredirects 188 ipsrcrouteforward 188 ipsrcrouterecv 188 ipsrcroutesend 188 ipv4 BIND 4. system and data 109 internal firewalls 2 internal network 19 internal network. 200 John the Ripper. 119. 198. NLuprintf 144 kernel services.3 157 IPv6 147 ipv6 BIND 8. dynamic assignment 146 IP forwarding 28 IP routing options 188 IP spoofing compared to DNS spoofing 156 IP spoofing protection 39 ip6srcrouteforward 188 ipforwarding 28. configuring 121 John the Ripper. 8.1. 26.2 157 ipv6 BIND 8. disabling 147 J John 109 John the Ripper 109.
audit trails. kernel 144 MIB 180 MIMEsweeper 48 minage 195. 157 named daemon in bos.client 157. 178 make 170 man pages 143 managing FireWall-1 logs 29 MANPATH 68. 167 lslpp 68 lsof 144 monitoring.lockd 174 M mail. 189 ls subcommand in nslookup 159. external 19 network. incoming 151 mailnull 177. 198. relinking 158 NAT 41 national language code points 197 ndnpd-router 147 ndpd-host 147 needexpnhelo 176 needmailhelo 176 needvrfyhelo 176 netmonAdapterHealth 188 Netscape 186 netstat 44.net. symbolic link 157 named-xfer. 127 maxage 195. 201 monitoring all at jobs 204 monitoring all cron jobs 204 monitoring security framework 8 234 Additional Security Tools for AIX Systems . infinite 152 loopback alias 199 lpd 147. 165 named. 196 maxexpired 195.nfs. 197 minother 195. 196 minalpha 195. 196 modifying startup files 142 modifying user password attributes 194 monitor cron and at jobs 201. 110. 152 netstat -af inet 144 network address translation (NAT) 40 Network Information System See NIS network management daemons. rpc. 197 MD5 109. 200 messages.net. 197 minlen 195. elements of 200 mrouted 148 multicasting daemons. internal 19 network-booting an SP node 151 NFS 153 biod. biod 174 daemons.client fileset 174 daemons. disabling 148 N name resolution 153 name resolution services 147 named 147. defined 174 configuring 168 daemons in bos. 203 monitor files and directories 201. restarting 158 named. disabling 148 network options 186 network scanners 199 Network Security Auditor See NSA Network Security Auditor (NSA) 47.L last 201 legacy SNMP daemon. nfsd 174 daemons. dpid2 148 licensed products 198 light parody 154 list of known vulnerabilities 199 List of ports that Check Point FireWall-1 uses 43 ListenAddress 75 local host table 153 login 151 loginretries 190 logintimes 192 LogLevel 76 loop. 49 network services 141 Network Time Protocol See NTP network topology verification 199 network&netmask 161 network. 196 maxrepeats 195. 202 monitor logs. 196 mindiff 195. relinking 158 named.tcp. and system behavior 200 monitor system logs 200.
interpreting its output 51 NSA.statd 174 disabling rpc.lockd.mountd. 186 no options 186 bcastping 187 clean_partial_conns 187 directed_broadcast 188 icmpaddressmask 188 ip6srcrouteforward 188 ipforwarding 188 ipignoreredirects 188 ipsendredirects 188 ipsrcrouteforward 188 ipsrcrouterecv 188 ipsrcroutesend 188 nolocsrcroute 188 tcp_pmtu_discover 188 udp_pmtu_discover 188 nobody (-2) 172 node customization 181 node installation 181 noexpn 176 no-fetch-glue (BIND4) option 163 nolocsrcroute 188 non-privileged ports (above 1023) 174 nonsense 154 no-recursion (BIND4) option 162 nosak 191 notsh 191 novrfy 176 NSA 141.base 49 nslookup 159. using 50 nsaauditor. relinking 158 ntalk 152 NTP 147 nuucp 189 O obtaining and installing John the Ripper 120 obtaining and installing PGP 126 obtaining and installing TCP Wrapper 78 obtaining and installing Tripwire 111 obtaining John the Ripper 120 obtaining PGP 126 obtaining SSH 61 obtaining TCP Wrapper 78 obtaining Tripwire 111 octal mask 192 on 152. defined 174 PC clients 152 protecting 173 rpc. interoperability with SSH. defined 174 NIS 153. rpc. 191 configuring 168 NIS+ 168.Com 76 opensshd 69.mountd 174 daemons.daemons. 68 OpenSSH using SSH1 68 OpenSSH using SSH2 71 OpenSSH. 72 options fetch-glue no (BIND8) 163 options no-fetch-glue (BIND4) 163 options no-recursion (BIND4) 162 options recursion no (BIND8) 162 Oracle 142 other attributes 193 235 . interpreting 51 NSA. 167 nsupdate. 176. defined 174 rpc.statd. 182.statd 175 most common security mistake 173 nfsd. 199 nsa 50 NSA output. 199 no 28. rpc. defined 174 NFS (port 2049) 170 nfs client tool 170 nfsd 174 nfsd.lockd 175 disabling rpc. installing on AIX 65 OpenSSH. defined 174 rpc. 191 Open Platform for Secure Enterprise Connectivity (OPSEC) 25 OpenSSH 61. 173 NLuprintf 144 nmap 198. 165 DNS debugging 168 listing all servers in a domain 167 ls subcommand 167 querying for name servers in a domain 166 querying specific types of records 166 querying Start Of Authority (SOA) record 166 server subcommand 167 zone transfers with ls subcommand 159. installing 49 NSA.
NFS 152 PC. chargen 152 port 25 (TCP). snmpd 180 port 19 (TCP & UDP). 200 PGP basics 124 PGP. disabling 143. 124 principles. 110. 127 PC clients. ftp 184 proxy servers. pop3d 153 port 111 (TCP & UDP). bootpd 151 port 69 (UD). portmapper 168. tftpd 181 port 69 (UDP). fingerd 152 port 9 (TCP & UDP). SSH clients for 76 pcnfsd 152 PERL script to convert /etc/hosts to BIND8 158 PERL script to convert BIND4 to BIND8 158 PermitRootLogin 75 PGP 198. krshd 151 port 6000 (TCP). DNS 154 print daemons. 153 port scanners 199 portmap 144 portmap daemon 168 portmapper 168 Ports 75 ports port 11 (TCP). installing 126 PGP. imapd (imap2) 153 port 15 (TCP). netstat 152 port 161 (TCP & UDP). SYN 187 packet. protecting 134 private network in DMZ 2 private-key 63 privilege escalation 5 proper network options 186 protecting /etc/rc. 174 port 13 (TCP & UDP). echo 152 port 79 (TCP). rlogind 151 port 514 (TCP). 147 printq 189 PrivacyOptions 176 authwarnings 176 goaway 176 needexpnhelo 176 needmailhelo 176 needvrfyhelo 176 noexpn 176 novrfy 176 restrictmailq 176 restrictqrun 176 private internal network 2 private internal servers 2 private key. obtaining 126 PGP. 177 port 37 (TCP & UDP). ACK 187 packet. rshd 151 port 518 (TCP). discard 153 PortSentry 198. rexecd 151 port 512 (UDP). strong 194 PATH 68.dt with Tripwire 144 protecting NFS 173 protecting sendmail with TCP Wrapper 180 protecting TCP services using SOCKS 186 protecting your private key 134 protection. SMTP (sendmail) 176. 152. using 127 pgpe 132 pgpk 127 Phil Zimmermann 126 ping sweep 199 piobe 143 planning security framework 3 planting back door 6 pop3 153 pop3d 153 port allocation via rpc (portmap) 151. talkd 152 port 540 (TCP). SYN/ACK 187 packets. IP spoofing 39 protocol.P packet. time 152 port 512 (TCP). daytime 152 port 143 (TCP & UDP). tftpd 151 port 7 (TCP & UDP). 199 PortSentry and /etc/hosts. comstat 151 port 513 (TCP). SOCKS 186 236 Additional Security Tools for AIX Systems . broadcast 187 protection. krlogind 151 port 544 (TCP).deny 199 PortSentry and loopback aliases 199 POSTFIX 78 Postfix 180 postman 177 Pretty Good Privacy (PGP) 109. uucpd 151 port 543 (TCP). ICMP echo 187 passive ftp 185 password cracker utility 197 password minimum length determination 197 password policy. X 183 port 67 (UDP). systat 152 port 110 (TCP).
179 SAINT 141.ps 152 PSSP 173 public key 71 public servers in DMZ public-key 63 public-key. 71 rsh 148. 178 ruserd 151 rwalld 151 rwhod 148 rwhod security exposure 148 S SafeFileEnvironment 178.statd. 151. secure 59 Remote Procedure Call See RPC removing entries from /etc/inetd.lockd 174 rpc. defined 174 rpc. 151 roles. 198 recommendations for fixing vulnerabilities 199 recursion no (BIND8) option 162 recursion. cleanup 34 rule. 151 rstatd 151 rtelnet 186 rtn 186 rule. 199 SAINT. defined 174 rpcinfo 168 rpcinfo.tcpip 144. 151. implicit drop 34 rule. dynamic 147 RPC 168 rpc (portmap) 151. securing 192 root. 198.dt 144 rc. 191 reliable clock source 147 remote access.conf 148 removing entries from /etc/inittab 142 removing entries from /etc/rc. 188 RS/6000 SP and ipforwarding 188 RS/6000 SP umask 022 192 RSA 62. 153 RPC authentication methods 168 rpc.mountd. restricting 161 recursive queries 164 referrals. private-key authentication scheme 184 pwdck 190 pwdwarntime 195. boundary 2 routes. 152. dynamic vs.statd 174 rpc. 157 rcp 151. 173. 64 RSA authentication 69. 174. example 169 RS/6000 SP 147. restricting 162 R RADIUS 25 rc. DNS 162 refresh -s inetd 149 refresh the sendmail daemon 177 registry 190. 191 rlogind 148. 149. AIX account 192 root SUID on sendmail 178 root. steps for securing 192 routed 147 routers. static vs. dynamic 147 routing daemons. stealth 35 RunAsUser 177.mountd 174 rpc. 197 Q qdaemon 143 Quaintance. 151 rshd 148. DNS 156 restarting named 158 restrict cache update 163 restrict dynamic updates 161 restrict queries 162 restrict recursion 161 restrict zone transfers 159 restrictmailq 176 restrictqrun 176 rexd 152 rexecd 151 RFC 2065 156 rftp 185.tcpip 144 removing sendmail banner 177 removing unnecessary default accounts 189 removing unnecessary services 141 resolvers. disabling 147 routing. static 147 routes. enhanced SATAN 199 237 . Jeff 176 queries. 190. 181. 186 rlogin 148. 196.lockd. defined 174 rpc.
184. 184. 180. unique 148 snmpd 144. DefaultUser 177 sendmail. third-party 197 sendmail 144. 199 scanning 5 scp 148. removing 177 sendmail built-in commands 175 sendmail configuration file 175 sendmail daemon 176 sendmail homepage 175 sendmail in daemon mode 177 sendmail not running as root 177 sendmail replacement 180 sendmail restricted shell See smrsh Sendmail Switch 178 sendmail -v -bi 179 sendmail version 8. 198 Secureway Firewall features 47 Secureway Network Despatche 48 securing AIX 139 securing DNS on AIX 159 securing FireWall-1 27 securing FireWall-1 default configurations 29 securing firewalls 24 securing root 192 securing X11 182 security exposure with /tftpboot directory 182 security exposure. BIND4 163 secure_zone. root SUID 178 sendmail.aix script 122 shell 151 showmount 170 signatures. 178 sendmail. 148 SNMPv1 180 SOCKS 185. 49.3 186 SOCKS to protect TCP services 186 238 Additional Security Tools for AIX Systems . digital 156 Simple Mail Transfer Protocol See SMTP Simple Network Management Protocol See SNMP smitty failed_logins 191 smrsh 179 SMTP 153. 198 sendmail banner 176 sendmail banner. . 198 search engine. SafeFileEnvironment 178. RunAsUser 177. AIX versions 175 sendmail. 179 services network 141 services configurations. 175. 198 Secure RPC 173 Secure Shell 59 secure shell (ssh) 59 secure_zone record. rwhod 148 security framework 1 architecture 6 implementation 7 incident response 10 monitoring 8 planning 3 security framework. 198 SGID 202 shadmgr.SAK key (^X^R) 191 sak_enabled attribute 191 SATAN 78. 153. . 175 SMTP TCP port 25 180 SMTPGreetingMessage 177 smurf attacks 187 SNMP 148. architecture 6 security framework. IMN 189 Secure Attention Key (SAK) 191 Secure NFS 173 secure remote access 59. planning 3 security tool suite 199 security tools. tightenning 153 services. 186 SOCKS support in AIX 4. building 2 security framework. name resolution 147 services. example 163 SecureCRT 62 SecureID 25 Secureway Firewall 47.8 177 sendmail. removing unnecessary 141 set up strong password policy 194 setting user attributes 190 sftp 148.deadletter 178 sendmail.3. incident response 10 security framework. 180 SNMP community names 180 SNMP community names. implementation 7 security framework. monitoring 8 security framework. PrivacyOptions 176 sendmail. dpid2 148 security exposure. include files 177 sendmail.forward files 177 sendmail.
76 standard UNIX dictionary 194. 173. comparison between DNS and IP 156 spoofing. 174. 188 SP administrative Ethernet 173 SP and ipforwarding 188 SP nightly mksysb backups 173 SP node customization 192 SP node installation 192 SP required services bootps 149 klogin 149 kshell 149 tftp 149 SP switch 173 SP umask 022 192 split configuration. 155 spray 152 sprayd 152 SSH 59. F-Secure 62 SSH. configuring and using 72 SSH2. 71 SSH2. BIND 157 symbolic link. DNS 154. used by OpenSSH 71 ssh-keygen 71.SOCKS v5 186 socksified ftp client 185 socksified TCP stack 186 source routing control 188 SP 147. security tool 199 Sun's Remote Procedure Call See RPC symbolic link. 73. 148. 149. defined 154 spoofing. obtaining 61 SSH. 195 stanza format 190 Start Of Authority (SOA) record 166 startup AIX 142 HACMP 142 Oracle 142 system 142 UNIX 142 starup TCP/IP daemons 144 static packet filter firewalls 15 static routes 188 static vs. interoperability with OpenSSH 76 SSH1 61 SSH1. named 157 symmetric key cryptography 63 SYN attack 37. implications of having 77 SSH. configuring and using 69 SSH1. 198 ssh 148 SSH clients for the PC 76 SSH daemon configuration options 75 SSH scp 184 SSH sftp 184 SSH with X 184 SSH. 38 SYN attack defined 187 SYN attack protection 187 SYN packet 187 SYN/ACK packet 187 SYNDefender 37 syslog 144 SyslogFacility 76 systat 152 system and data integrity 109 system behavior 200 system logs 200 system logs to monitor /etc/security/failedlogin 201 /etc/utmp 201 /var/adm/sulog 201 /var/adm/wtmp 201 system startup 142 T talk 152 239 .Com. DNS 164 spoofed ICMP traffic 187 spoofing 184 spoofing. difference with SSH2 62 SSH2 61. alternatives to 77 SSH. key concepts 62 SSH. dynamic routes 147. 188 stealth rule 35 stealth scan 199 stealth scans 199 steps for securing root 192 stopping TCP/IP 145 StrictHostKeyChecking 75 strong account policies 189 strong password policy 194 su 201 SUID 202 suite. difference with SSH1 62 SSH2. 181. 151. 184.
snmpd 180 TCP stack. protecting sendmail with 180 TCP/IP stopping 145 TCP/IP daemon startup 144 TCP/IP daemons started by default 144 tcp_pmtu_discover 188 tcpdchk 80 tcpdmatch 81 telephone system analogy 156 telnet 148 telnet to port 25 on localhost (0) 176 telnetd 148 terminal emulators 183 TFTP 181 tftp 149. 8. 165 rftp 185. 151. configuring 112. krshd 151 port 6000. 180. chargen 152 port 37. talkd 152 port 540. 200 Tripwire and CDE 144 Tripwire CheckConfig script 115 Tripwire secure database 200 Tripwire. configuring 79 TCP Wrapper. installing 111 240 Additional Security Tools for AIX Systems . echo 152 port 9. uucpd 151 port 543. comments on configuration 118 Tripwire. 114 Tripwire. time 152 port 7. alternatives to 119 Tripwire. 174 port 13. socksified 186 TCP Wrapper 7. SMTP (sendmail) 176. protecting ftp with 184 TCP Wrapper. 77. installing 78 TCP Wrapper. krlogind 151 port 544. 191 tpath always 191 tpath nosak 191 tpath notsh 191 tpath on 191 Tripwire 109. Volume 8 183.talkd 152 Tamu's Tiger 119 target acquisition and information gathering 4 TCP 186 port 11. pop3d 153 port 15. daytime 152 port 143. 198. 181 TFTP access control 181 tftpd 151 The Bat Book 179 The X Windows System Administrator's Guide. rshd 151 port 518. systat 152 port 110. obtaining 78 TCP Wrapper. 216 third-party security tools 197 threat assessment 4 three-digit octal mask 192 tighten remaining services configurations 153 tighten up user accounts 189 time 152 time bombs 203 time daemons. rexecd 151 port 513.deny 199 TCP Wrapper access control lists 198 TCP Wrapper security features 82 TCP Wrapper. 110. disabling 147 time synchronization daemons 147 timed 147 TIMEOUT 194 Tivoli Storage Manager See TSM TMOUT 194 Tools gzip 170 lsof 144 nfs 170 NSA 141 nslookup 159. netstat 152 port 25. 192. 198 TCP Wrapper /etc/hosts. fingerd 152 TCP & UDP port 111. discard 153 TCP &UDP port 161. rlogind 151 port 514. X 183 port 79. imapd (imap2) 153 port 19. 186 rtelnet 186 rtn 186 SAINT 141 scp 184 sftp 184 xwd 182 xwud 182 Topology Services daemon 188 tpath 190. 177 port 512. portmapper 168. 148.
com/faq/ssh/ssh-faq.integralis.html 60 www.com/software/network/dispatcher/ 48 U UDP 186 port 512. defined 176 vulnerabilities.cisco.sort 114 Trivial File Transfer Protocol See TFTP Trusted Computing Base (TCB) 119 try before you buy 198 TSM 142 ttdbserver 153 tty0 191 tty0 (console) 191 ttys 190.onsight.net/phrack/files/p48/p48-13.net 49 www-4.checkpoint.ibm. default 143 who 201 who /etc/security/failedlogin | more 201 Wietse Venema 180 world-writable directories 203 world-writable files 203 Wrapper. comstat 151 port 67. 191 umask 022 192 umask 077 192 uninstalling CDE 144 unique SNMP community names 148 UNIX advisory locking 174 untrapped-meta-character vulnerabilities 152 update requests. tftpd 151 udp_pmtu_discover 188 umask 190.htm 43 www.infoworld.enteract. untrapped-meta-character 152 W webserver.config 115 TXT (txt) records. setting 190 user password attributes.com/fw1/ 44 www.com/~lspitz/intrusion.com/~lspitz/fwtable.com/fw1 25 www.html 47 www.com 25 www.net/html/communities/firewalls/certification/vendors/index.Tripwire.com/supplements/99poy_win/99poy_s.checkpoint. TCP 148 write 144 writesrv 144 www.183 X11 xhost + 182. counterfeit 155 uprintf 144 uprintfd 144 user account cleanup 189 user attributes.icsa.phoneboy.com 48 www. 191 turning off glue fetching 163 tw.html 38 www. bootpd 151 port 69 181 port 69.shtml 24 www.com/support/technical/documents/index.txt 36 www. obtaining 111 Tripwire. DNS 163 types of firewalls 15 verifying Internet downloads 200 viewing connections 36 VRFY 175 VRFY. using 112 Tripwire.mimesweeper.phoneboy. modifying 194 using John the Ripper 122 using NSA 50 using PGP 127 using Tripwire 112 usrck 190 uucp 151.telemate.enteract.fc.list. 189 uucpd 151 X X client 184 X libraries 182 X over SSH 184 X server 183 X window system 144 X xterm 183 X11 access control 182 X11 xauth 182 X11 xhost 182 X11 xhost . 183 X11 xlock 183 V Venema. Wietse 180 241 .com/univercd/cc/td/doc/product/iaabu/centri4/user/scf4ch3.html 27 www. when should be run 118 tripwire.htm 17 www.
more restrictive example 161 xhost 182 xhost . restricting 159 242 Additional Security Tools for AIX Systems . securing 182 X11.apps.X11 xwd 182 X11 xwud 182 X11. example 160 xfrnets. 167 zone transfers.clients fileset 182 X11Forwarding 76 xauth 182 xfrnets directive 159 xfrnets. 183 xlock 183 xntpd 147 xterm 183 xwd 182 xwud 182 Y Yellow Pages (YP) See NIS Z zone substatements 160 zone transfers with nslookup 159.183 xhost + 182.
ibm. Lotus or Tivoli Employee O None of the above O Please do not use the information collected here for future marketing or promotional contacts or other communications beyond the scope of this transaction.com Document Number Redbook Title Review SG24-5971-00 Additional AIX Security Tools on IBM ^ pSeries. and SP/Cluster What other subjects would you like to see IBM Redbooks address? Please rate your overall satisfaction: Please identify yourself as belonging to one of the following groups: Your email address: The data you provide here may be used to provide you with information from IBM or our business partners about our products. The following link explains how we protect your personal information.com/privacy/yourprivacy/ © Copyright IBM Corp. depth and quality as appropriate. In particular we are interested in situations where a Redbook "made the difference" in a task or problem you encountered.com/redbooks • Fax this form to: USA International Access Code + 1 845 432 8264 • Send your comments in an Internet note to redbook@us. 2000 243 . IBM RS/6000. services or activities. ibm. Questions about IBM's privacy policy? O Very Good O Good O Average O Poor O Solution Developer O Customer O Business Partner O IBM.IBM Redbooks review Your feedback is valued by the Redbook authors. please review the Redbook. • Use the online Contact us review redbook form found at ibm. subject matter. Using one of the following methods. addressing value. structure.
and SP/Cluster .Additional AIX Security Tools on IBM ^ pSeries. IBM RS/6000.
non-IBM. and SP/Cluster Customize the security of your pSeries systems Explore IBM. we cover third-party software that is readily available. For more information: ibm. Specific recommendations are provided to help you implement IT solutions more effectively in your environment. Subjects covered in this redbook include: .com/redbooks SG24-5971-00 ISBN 0738418382 . Experts from IBM.System Integrity . and freeware security tools Learn new approaches to security From firewalls to operating system hardening. IBM RS/6000. Customers and Partners from around the world create timely technical information based on realistic scenarios. or Cluster. Along the way.Securing AIX INTERNATIONAL TECHNICAL SUPPORT ORGANIZATION BUILDING TECHNICAL INFORMATION BASED ON PRACTICAL EXPERIENCE IBM Redbooks are developed by the IBM International Technical Support Organization.Firewalls . The approach taken is from outside to inside and from top to bottom. As we move through these servers. we work from the application layer at the top to the network layer at the bottom.Secure Remote Access . modifications to the standard software that comes with AIX and PSSP. and assorted techniques that can all be used to provide enhanced security in your environment.® Additional AIX Security Tools on IBM pSeries. We move from the servers on the far reaches of your network that are visible to the outside world to those in the innermost recesses of your intranet containing your most confidential data.Network Mapping and Port Scanning . this redbook illustrates additional tools and techniques that you can use to enhance the security environment of your pSeries. RS/6000 workstation. SP.