.sagent

# This is a small script to generate a reusable ssh-agent for use with ssh key forwarding
# The classic use-case is to do git pull on a remote server without sending your ssh keys
# export SSH_AUTH_SOCK="$(sagent)"
# ssh -A remoteserver.com
# git pull
#
# It will helpfully re-use any existing ssh-agent processes, so you dont need to worry about spawning
# too many. It will only ever spawn a new ssh-agent process if needed.
#
# This script can be called in one of two ways:
# 1. export SSH_AUTH_SOCK="$(sagent)"
# 2. source /path/to/sagent

function sshagent_findsockets {
    find /tmp -uid $(id -u) -type s -name agent.\* 2>/dev/null
}

function sshagent_testsocket {
    if [ ! -x "$(which ssh-add)" ] ; then
        echo "ssh-add is not available; agent testing aborted"
        return 1
    fi

    if [ X"$1" != X ] ; then
        export SSH_AUTH_SOCK=$1
    fi

    if [ X"$SSH_AUTH_SOCK" = X ] ; then
        return 2
    fi

    if [ -S $SSH_AUTH_SOCK ] ; then
        ssh-add -l > /dev/null
        if [ $? != 0 -a $? != 1 ] ; then
            echo "Socket $SSH_AUTH_SOCK is dead!  Deleting!"
            rm -f $SSH_AUTH_SOCK
            return 4
        else
            return 0
        fi
    else
        echo "$SSH_AUTH_SOCK is not a socket!"
        return 3
    fi
}

function sshagent_init {
    # ssh agent sockets can be attached to a ssh daemon process or an
    # ssh-agent process.

    AGENTFOUND=0

    # Attempt to find and use the ssh-agent in the current environment
    if sshagent_testsocket ; then AGENTFOUND=1 ; fi

    # If there is no agent in the environment, search /tmp for
    # possible agents to reuse before starting a fresh ssh-agent
    # process.
    if [ $AGENTFOUND = 0 ] ; then
        for agentsocket in $(sshagent_findsockets) ; do
            if [ $AGENTFOUND != 0 ] ; then break ; fi
            if sshagent_testsocket $agentsocket ; then AGENTFOUND=1 ; fi
        done
    fi

    # If at this point we still haven't located an agent, it's time to
    # start a new one
    if [ $AGENTFOUND = 0 ] ; then
        eval `ssh-agent`
    fi

    # Clean up
    unset AGENTFOUND
    unset agentsocket
}