title: SSH Key: “Permissions 0644 for 'id_rsa.pub' are too open.” on mac
body: <p>I generate a ssh key pair on my mac and add the public key to my ubuntu server(in fact, it is a virtual machine on my mac),but when I try to login the ubuntu server,it says:<br /></p>
  
  <pre><code>@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@
  @         WARNING: UNPROTECTED PRIVATE KEY FILE!          @
  @@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@
  Permissions 0644 for '/Users/tudouya/.ssh/vm/vm_id_rsa.pub' are too open.
  It is required that your private key files are NOT accessible by others.
  This private key will be ignored.
  bad permissions: ignore key: /Users/tudouya/.ssh/vm/vm_id_rsa.pub
  Permission denied (publickey,password).
  </code></pre>
  
  <p>I have tried many ways to solve this, change the key file mode, change the folder mode,as some answer on stackoverflow,but it doesn't work.<br />
  the key file permission:</p>
  
  <pre><code>vm dir:
  drwxr-xr-x   4 tudouya  staff    136  4 29 10:37 vm
  
  key file:
  -rw-------  1 tudouya  staff  1679  4 29 10:30 vm_id_rsa
  -rw-r--r--  1 tudouya  staff   391  4 29 10:30 vm_id_rsa.pub
  </code></pre>
  
  <p>please give me some idea...
  =========================================<br /><br />
  I write the host infomation to ssh_config:</p>
  
  <pre><code>Host ubuntuvm
      Hostname 10.211.55.17
      PreferredAuthentications publickey
      IdentityFile /Users/tudouya/.ssh/vm/vm_id_rsa.pub
  </code></pre>
  
  <p>I run command "ssh -v ubuntuvm",it displays:</p>
  
  <pre><code>ssh -v ubuntuvm
  OpenSSH_6.2p2, OSSLShim 0.9.8r 8 Dec 2011
  debug1: Reading configuration data /etc/ssh_config
  debug1: /etc/ssh_config line 20: Applying options for *
  debug1: /etc/ssh_config line 103: Applying options for *
  debug1: /etc/ssh_config line 175: Applying options for ubuntuvm
  debug1: Connecting to 10.211.55.17 [10.211.55.17] port 22.
  debug1: Connection established.
  debug1: identity file /Users/tudouya/.ssh/vm/vm_id_rsa.pub type 1
  debug1: identity file /Users/tudouya/.ssh/vm/vm_id_rsa.pub-cert type -1
  debug1: Enabling compatibility mode for protocol 2.0
  debug1: Local version string SSH-2.0-OpenSSH_6.2
  debug1: Remote protocol version 2.0, remote software version OpenSSH_6.6.1p1 Ubuntu-8
  debug1: match: OpenSSH_6.6.1p1 Ubuntu-8 pat OpenSSH*
  debug1: SSH2_MSG_KEXINIT sent
  debug1: SSH2_MSG_KEXINIT received
  debug1: kex: server-&gt;client aes128-ctr hmac-md5-etm@openssh.com none
  debug1: kex: client-&gt;server aes128-ctr hmac-md5-etm@openssh.com none
  debug1: SSH2_MSG_KEX_DH_GEX_REQUEST(1024&lt;1024&lt;8192) sent
  debug1: expecting SSH2_MSG_KEX_DH_GEX_GROUP
  debug1: SSH2_MSG_KEX_DH_GEX_INIT sent
  debug1: expecting SSH2_MSG_KEX_DH_GEX_REPLY
  debug1: Server host key: RSA 55:6d:4f:0f:23:51:ac:8e:70:01:ec:0e:62:9e:1c:10
  debug1: Host '10.211.55.17' is known and matches the RSA host key.
  debug1: Found key in /Users/tudouya/.ssh/known_hosts:54
  debug1: ssh_rsa_verify: signature correct
  debug1: SSH2_MSG_NEWKEYS sent
  debug1: expecting SSH2_MSG_NEWKEYS
  debug1: SSH2_MSG_NEWKEYS received
  debug1: Roaming not allowed by server
  debug1: SSH2_MSG_SERVICE_REQUEST sent
  debug1: SSH2_MSG_SERVICE_ACCEPT received
  debug1: Authentications that can continue: publickey,password
  debug1: Next authentication method: publickey
  debug1: Offering RSA public key: /Users/tudouya/.ssh/vm/vm_id_rsa.pub
  debug1: Server accepts key: pkalg ssh-rsa blen 279
  @@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@
  @         WARNING: UNPROTECTED PRIVATE KEY FILE!          @
  @@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@
  Permissions 0644 for '/Users/tudouya/.ssh/vm/vm_id_rsa.pub' are too open.
  It is required that your private key files are NOT accessible by others.
  This private key will be ignored.
  bad permissions: ignore key: /Users/tudouya/.ssh/vm/vm_id_rsa.pub
  debug1: No more authentication methods to try.
  Permission denied (publickey,password).
  </code></pre>