#!/usr/bin/perl
###########################################################################
#
#  sshagent.pl     Edward Diehl  Sept, 2006  V. 1.1
#
#  This script is a frontend for ssh-agent to make it easier to use.
#  The script does the following:
#  1. Check env. variable SSH_AGENT_PID is already set. 
#     If so assume that all is ok and so quit.
#  2. If there is no SSH_AGENT_PID then look for ssh-agent processes.
#     If found config for it, i.e. set SSH_AGENT_PID and SSH_AUTH_SOCK,
#     and list any loaded keys. 
#  3. If no ssh-agent is found then start one, and load ~/.ssh/id_rsa 
#     if it exists
#  
#  To set these variables in the parent shell you must invoke
#  this script as: eval `sshagent.pl`.  If you just run the script straight
#  you see the C-shell commands it generates, but variables are not set.
#  
#  To kill an existing ssh-agent run with the the -k option.
#  
###########################################################################
#  Check for arguments 
###########################################################################
if( $ARGV[0] eq "-h" || $ARGV[0] eq "--help" ) {
  print "echo '======== Script sshagent.pl     Author: Edward Diehl =======';\n";
  print "echo '  This script is a frontend for ssh-agent to make it easier to use.';\n";
  print "echo '  The script does the following:';\n";
  print "echo '  1. Check env. variable SSH_AGENT_PID is already set.';\n";
  print "echo '     If so assume that all is ok and so quit.';\n";
  print "echo '  2. If there is no SSH_AGENT_PID then look for ssh-agent processes.';\n";
  print "echo '     If found config for it, i.e. set SSH_AGENT_PID and SSH_AUTH_SOCK';\n";
  print "echo '  3. If no ssh-agent is found then start ssh-agent.';\n";
  print "echo '';\n";
  print "echo '   To set these variables in the parent shell you must invoke';\n";
  print "echo '   this script as: eval `sshagent.pl`.  If you just run the script straight';\n";
  print "echo '   you see the C-shell commands it generates, but variables are not set.';\n";
  print "echo '';\n";
  print "echo '   To kill an existing ssh-agent run with the the -k option.'\n";
  exit;
} elsif ( $ARGV[0] eq "-k" ) {
  system("ssh-agent -k");
  exit;
}
###########################################################################
#  See if SSH_AGENT_PID is already set in which case there is nothing to do
###########################################################################
$ssh_pid = $ENV{SSH_AGENT_PID}; 
if( $ENV{SSH_AGENT_PID} != "" ) { 
  $ssh_sock = $ENV{SSH_AUTH_SOCK};
  print "echo ssh-agent already running and configured:;\n";
  print "echo '  SSH_AGENT_PID = $ssh_pid';\n";
  print "echo '  SSH_AUTH_SOCK = $ssh_sock';\n";
  print "echo SSH Keys loaded:;\n";
  print "echo `ssh-add -l`\n";
  exit;
}
###########################################################################
#   Get a list of all ssh-agents running 
###########################################################################
@list = `ps -C ssh-agent -o pid=,user=`;
$user = $ENV{USER};
$found_pid = 0;
###########################################################################
#  Check if one of these agents is owned by the user
###########################################################################
foreach $line (@list) {
  if( $line =~ /(\d+)\s+$user/ ) {
    $ssh_pid = $1;
    $found_pid++;
    print "echo Found ssh-agent pid=$ssh_pid for user $user;\n"
  } 
}
###########################################################################
#  If ssh-agent exists, find the /tmp/ssh* file which has the socket 
#  NOTE: use 'ls' rather than 'find' because find generates stupid errors
#  when looking at non-user-owned files in /tmp
###########################################################################
if( $found_pid == 1 ) {
  @list = `ls -ald /tmp/ssh-*`;
  $found_sock = 0;
  foreach $line (@list) {
    if( $line =~ /$user/ ) {
      if( $line =~ /ssh-(\w+)/ ) {
        $ssh_sock = `find /tmp/ssh-$1/ -name "agent.*"`;
        chop $ssh_sock;
        $found_sock++;
      }
    } 
  }
###########################################################################
#  If found ssh-agent exists, print details
###########################################################################
  if( $found_sock == 1 ) {
    print "setenv SSH_AGENT_PID $ssh_pid;\n";
    print "setenv SSH_AUTH_SOCK $ssh_sock;\n";
    print "echo SSH_AGENT_PID = $ssh_pid;\n";
    print "echo SSH_AUTH_SOCK = $ssh_sock;\n";
    print "echo SSH Keys loaded:;\n";
    print "echo `ssh-add -l`\n";
  } else {
    print "echo ERROR: found ssh-agent with pid=$ssh_pid but $found_sock SOCK files in /tmp - aborting\n";
    exit;    
  }
} elsif( $found_pid > 1 ) {
  print "echo WARNING: Found $found ssh-agents running for user $user - aborting\n";
} else {
  print "echo No ssh-agent running, start one;\n";
  system("ssh-agent -c");
#  If "id_rsa" exists load it
  $keyfile = $ENV{"HOME"} . "/.ssh/id_rsa"; 
  if( -e  $keyfile ) {
    print "echo `ssh-add $keyfile`\n";
  }
}