Tails Dead Man's switch

#!/usr/bin/env python3

from pydbus import SystemBus
from gi.repository import GLib
from functools import partial
import logging
import os

TIMEOUT = 900
event = 0

logging.basicConfig(level=logging.DEBUG)
bus = SystemBus()

def handlePropertiesChanged(dbus, _busname, properties, _dunno):
  # We only care about Locked Events
  if(not 'LockedHint' in properties):
    return

  lock = properties['LockedHint']
  logging.debug( "%s - %s" % (dbus._path, lock ))


  # Sorry
  global event

  if(lock):
    if(event == 0):
      logging.debug("Starting timer")
      event = GLib.timeout_add_seconds(TIMEOUT, handleTimeout)
  else:
    if(event != 0):
      logging.debug("Cancelling timer")
      GLib.source_remove(event)
      event = 0

def handleTimeout():
  logging.warning("User session idle for a long time.")
  event = 0
  os.system("sudo -n poweroff")

def findAndRegisterSessions():
  login = bus.get(".login1")
  # Find the dbus path for all the existing sessions.
  sessions = [x[4] for x in login.ListSessions()]

  # Listen to sessions. (This begs the question how should we unsubscribe?)
  for sess in sessions:
    sdb = bus.get(".login1", sess)
    # All sessions or just active? Hmm.
    #if(sdb.Active):
    logging.debug( "registering - %s" % (sdb._path))
    sdb.onPropertiesChanged = partial(handlePropertiesChanged, sdb)


def main():
  findAndRegisterSessions()

  GLib.MainLoop().run()


if __name__ == "__main__":
  main()