#!/bin/sh
#-----------------------------------------------------------------------
# Starting ssh-agent when logging in
#-----------------------------------------------------------------------
# $Id: ssh-login,v 1.4 2002/08/06 17:57:54 jochen Exp jochen $
#-----------------------------------------------------------------------
# This works when you use a bourne shell compatible shell.  Add the
# following sniplet into your .bashrc, .kshrc or .zshrc depending
# on your login shell.  I've tested it with bash.
#-----------------------------------------------------------------------
# if [ -f $HOME/scripts/ssh-login ]; then
#     . $HOME/scripts/ssh-login
# fi
#-----------------------------------------------------------------------

#-----------------------------------------------------------------------
pidfile=$HOME/.ssh/agent.pid.`hostname`
identity=$HOME/.ssh/id_dsa
#-----------------------------------------------------------------------

#-----------------------------------------------------------------------
debug()
{
  :
  #echo "$*"
}

#-----------------------------------------------------------------------
is_ssh_agent()
{
    debug "function is_ssh_agent entered"
    # is SSH_AGENT_PID set and valid?
    if [ -n "$1" ]
    then
	# Linux /proc style
	if [ -f "/proc/$1/cmdline" ]
	then
	    # backticks are more portable than $( / $)
	    # which don't work with Solaris /sbin/sh
	    cmdline=`cat /proc/$1/cmdline | tr -d '\000'`
	    # X in front of string comparisons to avoid
	    # [: argument expected
	    if [ ! X"ssh-agent" = X"$cmdline" ]
	    then
		debug "PID $1 is no ssh-agent"
		return 1
	    fi
	# Solaris and AIX /proc style
	elif [ -f "/proc/$1/psinfo" ]
	then
	    cmdline=`strings /proc/$1/psinfo | head -1`
	    if [ ! X"ssh-agent" = X"$cmdline" ]
	    then
		debug "PID $1 is no ssh-agent"
		return 1
	    fi
	# no /proc at all, e.g. HP-SUX
	# after all, only ps is portable, and even that is a lie :-(
	elif [ -z "`ps -e | grep \"^ *$1 \" | grep ssh-agent `" ]
	then
	    debug "PID $1 is invalid"
	    return 1
	fi
	return 0
    fi
    return 1
}

maybe_save_pid()
{
    debug "function maybe_save_pid entered"
    debug "SSH_AGENT_PID is $SSH_AGENT_PID"
    WORK_SSH_AGENT_PID=$SSH_AGENT_PID
    WORK_SSH_AUTH_SOCK=$SSH_AUTH_SOCK
    if [ -f $pidfile ]; then
	. $pidfile > /dev/null
	debug "saved SSH_AGENT_PID is $SSH_AGENT_PID"
    else
	unset SSH_AGENT_PID
	unset SSH_AUTH_SOCK
    fi
    if [ ! x"$WORK_SSH_AGENT_PID" = x"$SSH_AGENT_PID" ]; then
        debug "Saving new SSH_AGENT_PID $WORK_SSH_AGENT_PID"
	echo "SSH_AGENT_PID=$WORK_SSH_AGENT_PID ; export SSH_AGENT_PID" > $pidfile
	echo "SSH_AUTH_SOCK=$WORK_SSH_AUTH_SOCK ; export SSH_AUTH_SOCK" >> $pidfile
    fi
}

load_keys()
{
    if tty -s; then
	# Enter passphrase for your key
	debug "adding keys to agent"
	ssh-add $identity
    elif [ -n "$DISPLAY" ]; then
	SSH_ASKPASS=/usr/bin/ssh-askpass
	debug "adding keys to agent"
	ssh-add $identity
    fi
}

ssh_login()
{
    #-----------------------------------------------------------------------
    # If we are logging in via ssh and have agent forwarding on
    if [ ! -z "$SSH_CLIENT" -a ! -z "$SSH_AUTH_SOCK" ]; then
	debug "SSH_CLIENT is set and agent forwarding on, no agent needed"
	return
    fi
    #-----------------------------------------------------------------------
    # Check old agent PID
    if is_ssh_agent "$SSH_AGENT_PID"; then
	maybe_save_pid
	return
    fi
    #-----------------------------------------------------------------------
    # Read PID-file when there is one
    if [ -f $pidfile ]; then
	debug "Reading PID-File »${pidfile}«"
	. $pidfile > /dev/null
	debug "Values are: SSH_AGENT_PID=$SSH_AGENT_PID, SSH_AUTH_SOCK=$SSH_AUTH_SOCK"
    fi

    # is the PID-file valid?
    if is_ssh_agent "$SSH_AGENT_PID"; then
	ssh-add -l > /dev/null || load_keys
	return
    fi

    debug "Starting ssh-agent, writing to $pidfile"
    ssh-agent > $pidfile
    . $pidfile > /dev/null

    load_keys

}
#-----------------------------------------------------------------------
case "$-" in
*C*) # noclobber is set
    set +o noclobber
    ssh_login
    set -o noclobber
    ;;
*)
    ssh_login
    ;;
esac
#-----------------------------------------------------------------------