Rakshas' Scrapbook

public key authentication

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in addition to mysetup, this code assumes that your ssh key(s) are stored on a hot-swappable mass storage device (usb stick, flash card, etc.). it first asks you to connect the storage device and then adds your key(s) into the ssh agent.

MOUNTPOINT

the path where your mass storage device can be mounted

IDENTITY

the identity that is to be added

LIFETIME

the lifetime of the identity

DEFAULT_LIFETIME

the default lifetime that is applied to all identities

##################################################
### ssh agent
###

# the identity you expect to be present
IDENTITY="/mnt/usb/.ssh/id_dsa"
# mount point of external filesystem (is mounted if set)
MOUNTPOINT="/mnt/usb"
# the lifetime of the identity
LIFETIME="0"
# the lifetime of manually added identities
DEFAULT_LIFETIME="0"

# functions
function agent_running() {
    # agent is not running
    test "$(ps ax | perl -ne "print if m/^\s*${SSH_AGENT_PID}/" | grep ssh-agent | wc -l)" -eq 1
    return $?
}
function key_present() {
    KEY=$1

    test $(ssh-add -l | grep ${KEY} | wc -l) -eq 1
    return $?
}

# enable usage of SSH_ASKPASS if DISPLAY is present
test "x${DISPLAY}" != "x" && {
    SSH_ASKPASS="$(which gtk2-ssh-askpass x11-ssh-askpass 2>/dev/null | head -n 1)"
    test "x${SSH_ASKPASS}" != "x" && {
        export SSH_ASKPASS
        SSH_ADD_OPTS="</dev/null"
    }
}

# check for running ssh-agent
source ~/.ssh-agent
agent_running || {
    ssh-agent -s -t ${DEFAULT_LIFETIME} >~/.ssh-agent
    source ~/.ssh-agent
}

# adding identity upon login
key_present ${IDENTITY} || {
    XMESSAGE="$(which gxmessage xmessage 2>/dev/null | head -n 1)"
    if test "$(${XMESSAGE} -center -title "${MOUNTPOINT}" -buttons Done,Cancel -default Done -print "please prepare the mount point")" == "Done"
    then
        mount ${MOUNTPOINT}
        if mount | grep -q " on ${MOUNTPOINT} type vfat "
        then
            chmod 600 ${IDENTITY}
        fi
        COMMAND="ssh-add -t ${LIFETIME} ${IDENTITY} ${SSH_ADD_OPTS}"
        eval ${COMMAND}
        umount ${MOUNTPOINT}
    fi
}

# cleanup
unset IDENTITY
unset MOUNTPOINT
unset LIFETIME
unset DEFAULT_LIFETIME
unset SSH_ADD_OPTS
unset COMMAND