Md at debian.org

Thu, 20 Feb 2014

Automatically unlocking xscreensaver in some locations

When I am at home I do not want to be bothered by the screensaver locking my laptop. To solve this, I use a custom PAM configuration which checks if I am authenticated to the local access point.

Add this to the top of /etc/pam.d/xscreensaver:

auth sufficient pam_exec.so quiet /usr/local/sbin/pam_auth_xscreensaver

And then use a script like this one to decide when you want the display to be automatically unlocked:

#!/bin/sh -e

# return the ESSID of this interface
current_essid() {
  /sbin/iwconfig $1 | sed -nre '/ESSID/s/.*ESSID:"([^"]+)".*/\1/p'
}

# automatically unlock only for these users
case "$PAM_USER" in
  "")   echo "This program must be run by pam_auth.so!"
        exit 1
        ;;
  md)   ;;

  *)    exit 1
        ;;
esac

CURRENT_ESSID=$(current_essid wlan0)

# automatically unlock when connected to these networks
case "$CURRENT_ESSID" in
  MYOWNESSID) exit 0 ;;
esac

exit 6