My Setup: Public Key Authentication
Published on 23 Jan 2005Tags #SSH
The following code chunk is copied from my ~/.bash_profile and demonstrates how to ensure that all login shells share a single SSH agent. You will also want to distribute your public key(s) and enable agent forwarding.
The code contains come configuration options:
-
The IDENTITY that is to be added
-
The LIFETIME of the identity
-
The DEFAULT_LIFETIME that is applied to all identities
-
Whether the identity is added on login or when using ssh (ADD_ON_LOGIN)
##################################################
### ssh agent
###
# the identity you expect to be present
IDENTITY="${HOME}/.ssh/id_dsa"
# the lifetime of the identity
LIFETIME="0"
# the lifetime of manually added identities
DEFAULT_LIFETIME="1h"
# when to add identity
ADD_ON_LOGIN="true"
# functions
function agent_running() {
# agent is not running
test "$(ps ax | perl -ne "print if m/^s*${SSH_AGENT_PID}/" | 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
}
if ${ADD_ON_LOGIN}
then
# adding identity upon login
key_present ${IDENTITY} || {
COMMAND="ssh-add -t ${LIFETIME} ${IDENTITY} ${SSH_ADD_OPTS}"
eval ${COMMAND}
}
else
# ssh alias
alias ssh="key_present ${IDENTITY} || ssh-add -t ${LIFETIME} ${IDENTITY} ${SSH_ADD_OPTS}; ssh"
fi
# cleanup
unset IDENTITY
unset LIFETIME
unset DEFAULT_LIFETIME
unset SSH_ADD_OPTS
Feedback is always welcome! If you'd like to get in touch with me concerning the contents of this article, please use Twitter.