#!/bin/sh
# Find or start an ssh-agent, as desired.
# 
# Copyright 2001, Bri Hatch (bri@ifokr.org)
# Released under the GPL.
#
# Version: 1.2.
#
# Available at
#   http://www.hackinglinuxexposed.com/tools/find-ssh-agent
#
#
# Purpose: Find and attach to a running SSH agent automatically,
#          or start one if necessary.
#
# This code started way back in 1995, and works like a charm
# for me.  For something with a wider audience, you may want
# to look at keychain (www.gentoo.org/proj/en/keychain.xml)
# which does a very similar thing, but automatically handles
# adding the keys to the agent as well.
#
#
# Theory:
#       Never assume that ENV variables are sufficient, actually check
#       to see if an agent is listening.
#
#       Finds agents in the following order:
#               Agent that are properly set in current ENV.
#
#               Agent specified in ~/.ssh/agent_params
#                       (theoretically the most recently started agent)
#
#               Agents listening in /tmp/ssh-????????/
#                        (OpenSSH naming convention)
#
#               Agents listening in /tmp/ssh-username/
#                        (older naming convention)
#
#               Give up and start an agent, if desired, echoing agent
#                        parameters to ~/.ssh/agent_params for next time
#
# Usage:
#
# NOTBugs:
#       This script does not work with csh and friends.  If you're using
#       csh/tcsh/etc, scold yourself and learn Bourne Shell.
#
# Requirements:
#       ssh-agent and 'whoami' must be in your PATH already.



whoami=`whoami`


debug="/bin/false"
environ="/bin/false"
startagent="/bin/false"

usage () {
	cat <<EOM >&2
Usage: $0 [options]
-e         Print environment variables to stdout
-s         Start agent if one not found
-d         Print debugging info
-h         This help text
EOM
	exit 1
}


set - `getopt hdes $*`
for i in $*
do
        case $i in
                -d)     debug="/bin/true"; shift ;;
                -e)     environ="/bin/true"; shift ;;
                -s)     startagent="/bin/true"; shift ;;
                -h)     usage ;;
        esac
done


findAgent () {
        local SSH_PARAMS

        if `agentAlive` ; then                  # Check if we're already set
                `$debug` && echo "Using existing agent" >&2
        else
                mkdir $HOME/.ssh 2>/dev/null
                SSH_PARAMS=$HOME/.ssh/agent_params
                if test -r $SSH_PARAMS; then
                        . $SSH_PARAMS  > /dev/null
                fi

                if `agentAlive` ; then
                        `$debug` && echo "Connected to existing agent" >&2
                else
                        for socket in /tmp/ssh-????????/* /tmp/ssh-$whoami/* 
                        do
                                SSH_AUTH_SOCK=$socket;
                                SSH_AUTHENTICATION_SOCKET=$socket;
				export SSH_AUTH_SOCK
				export SSH_AUTHENTICATION_SOCKET
                                if `agentAlive` ; then
                                        break
                                fi
                        done
                        if `agentAlive` ; then
                                `$debug` && echo "Connected to (unregistered) Agent" >&2
                        else
				if `$startagent` ; then
					eval `ssh-agent -s 2>/dev/null | \
						tee $SSH_PARAMS | grep -v '^echo '`
					if `agentAlive` ; then
						`$debug` && echo "New Agent started" >&2
					else
						echo "$0: Cannot start the agent" >&2
						exit 1
					fi
				else
					echo "$0: Agent not found." >&2
					echo "$0: Use '-s' to force new agent creation" >&2
					exit 1
				fi
                        fi
                fi
        fi
}

agentAlive () {
        ssh-add -l > /dev/null 2>&1             # see if it's live
        [ $? -ne 2 ]
}

findAgent
unset -f findAgent agentAlive

`$environ` && echo "SSH_AUTH_SOCK=$SSH_AUTH_SOCK ; export SSH_AUTH_SOCK"
`$environ` && echo "SSH_AUTHENTICATION_SOCKET=$SSH_AUTH_SOCK ; export SSH_AUTHENTICATION_SOCKET"

exit 0;