#fixed code
                                public static void main(String[] args) throws Exception {
        int port = 8000;
        boolean error = false;

        for (int i = 0; i < args.length; i++) {
            if ("-p".equals(args[i])) {
                if (i + 1 >= args.length) {
                    System.err.println("option requires an argument: " + args[i]);
                    break;
                }
                port = Integer.parseInt(args[++i]);
            } else if (args[i].startsWith("-")) {
                System.err.println("illegal option: " + args[i]);
                error = true;
                break;
            } else {
                System.err.println("extra argument: " + args[i]);
                error = true;
                break;
            }
        }
        if (error) {
            System.err.println("usage: sshd [-p port]");
            System.exit(-1);
        }

        System.err.println("Starting SSHD on port " + port);
                                                    
        SshServer sshd = SshServer.setUpDefaultServer();
        sshd.setPort(port);
        if (SecurityUtils.isBouncyCastleRegistered()) {
            sshd.setKeyPairProvider(new PEMGeneratorHostKeyProvider("key.pem"));
        } else {
            sshd.setKeyPairProvider(new SimpleGeneratorHostKeyProvider("key.ser"));
        }
        if (OsUtils.isUNIX()) {
            sshd.setShellFactory(new ProcessShellFactory(new String[] { "/bin/sh", "-i", "-l" },
                                 EnumSet.of(ProcessShellFactory.TtyOptions.ONlCr)));
        } else {
            sshd.setShellFactory(new ProcessShellFactory(new String[] { "cmd.exe "},
                                 EnumSet.of(ProcessShellFactory.TtyOptions.Echo, ProcessShellFactory.TtyOptions.ICrNl, ProcessShellFactory.TtyOptions.ONlCr)));
        }
        sshd.setPasswordAuthenticator(new PasswordAuthenticator() {
            public boolean authenticate(String username, String password, ServerSession session) {
                return username != null && username.equals(password);
            }
        });
        sshd.setPublickeyAuthenticator(new PublickeyAuthenticator() {
            public boolean authenticate(String username, PublicKey key, ServerSession session) {
                //File f = new File("/Users/" + username + "/.ssh/authorized_keys");
                return true;
            }
        });
        sshd.setForwardingFilter(new ForwardingFilter() {
            public boolean canForwardAgent(ServerSession session) {
                return true;
            }

            public boolean canForwardX11(ServerSession session) {
                return true;
            }

            public boolean canListen(InetSocketAddress address, ServerSession session) {
                return true;
            }

            public boolean canConnect(InetSocketAddress address, ServerSession session) {
                return true;
            }
        });
        sshd.start();
    }
#vulnerable code 
                                public static void main(String[] args) throws Exception {
        int port = 8000;
        boolean error = false;

        for (int i = 0; i < args.length; i++) {
            if ("-p".equals(args[i])) {
                if (i + 1 >= args.length) {
                    System.err.println("option requires an argument: " + args[i]);
                    break;
                }
                port = Integer.parseInt(args[++i]);
            } else if (args[i].startsWith("-")) {
                System.err.println("illegal option: " + args[i]);
                error = true;
                break;
            } else {
                System.err.println("extra argument: " + args[i]);
                error = true;
                break;
            }
        }
        if (error) {
            System.err.println("usage: sshd [-p port]");
            System.exit(-1);
        }

        System.err.println("Starting SSHD on port " + port);
                                                    
        SshServer sshd = SshServer.setUpDefaultServer();
        sshd.setPort(port);
        if (SecurityUtils.isBouncyCastleRegistered()) {
            sshd.setKeyPairProvider(new PEMGeneratorHostKeyProvider("key.pem"));
        } else {
            sshd.setKeyPairProvider(new SimpleGeneratorHostKeyProvider("key.ser"));
        }
        if (System.getProperty("os.name").toLowerCase().indexOf("windows") < 0) {
            sshd.setShellFactory(new ProcessShellFactory(new String[] { "/bin/sh", "-i", "-l" },
                                 EnumSet.of(ProcessShellFactory.TtyOptions.ONlCr)));
        } else {
            sshd.setShellFactory(new ProcessShellFactory(new String[] { "cmd.exe "},
                                 EnumSet.of(ProcessShellFactory.TtyOptions.Echo, ProcessShellFactory.TtyOptions.ICrNl, ProcessShellFactory.TtyOptions.ONlCr)));
        }
        sshd.setPasswordAuthenticator(new PasswordAuthenticator() {
            public boolean authenticate(String username, String password, ServerSession session) {
                return username != null && username.equals(password);
            }
        });
        sshd.setPublickeyAuthenticator(new PublickeyAuthenticator() {
            public boolean authenticate(String username, PublicKey key, ServerSession session) {
                //File f = new File("/Users/" + username + "/.ssh/authorized_keys");
                return true;
            }
        });
        sshd.setForwardingFilter(new ForwardingFilter() {
            public boolean canForwardAgent(ServerSession session) {
                return true;
            }

            public boolean canForwardX11(ServerSession session) {
                return true;
            }

            public boolean canListen(InetSocketAddress address, ServerSession session) {
                return true;
            }

            public boolean canConnect(InetSocketAddress address, ServerSession session) {
                return true;
            }
        });
        sshd.start();
    } 
                            #location 36 
                            #vulnerability type NULL_DEREFERENCE