tunnelrunner_askpass

#!/usr/bin/env python2

# Copyright (c) 2008-2013 Brandon williams
#
# AUTHOR:
# Brandon Williams <opensource@subakutty.net>
#
# This file is part of TunnelManager
#
# TunnelManager is free software; you can redistribute it and/or modify it
# under the terms of the GNU General Public License version 2, as published by
# the Free Software Foundation.
#
# TunnelManager is distributed in the hope that it will be useful,
# but WITHOUT ANY WARRANTY; without even the implied warranty of
# MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
# General Public License for more details.
#
# You should have received a copy of the GNU General Public License
# along with Tunnelmanager; if not, write to the Free Software
# Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA  02111-1307  USA
#

import os
import errno
import stat
import subprocess
import sys
import time

def acquireLockFile(lockfile):
    """Acquire the lock file. We will try once per second for 10 minutes."""

    max_wait = 60; # wait up to 60 seconds
    max_age = 300; # assume it's bad after 5 minutes
    fd = 0

    while True:
        try:
            fd = os.open(lockfile,os.O_EXCL|os.O_RDWR|os.O_CREAT)
            break
        except OSError, e:
            if e.errno != errno.EEXIST:
                raise
            # file already exists. find out how old it is.
            f = None
            s = None
            try:
                f = open(lockfile, "r")
                s = os.stat(lockfile)
            except OSError, e:
                if e.errno != errno.EEXIST:
                    print >>sys.stderr, "%s exists but stat() failed: %s" % (lockfile,e.strerror)
                    sys.exit(1)
                    raise
                continue; #File is gone now. Just try again.

            # didn't create lock file, still there, how old is it?
            now = int(time.time())
            if((now - s[stat.ST_MTIME]) > max_age):
                pid = f.readline()
                print >>sys.stderr, "%s has been locked for more than %d seconds by PID %s; breaking lock" % (lockfile, max_age, pid)
                os.remove(lockfile)
            elif((now - s[stat.ST_MTIME]) > max_wait):
                # wait up to 10 minutes for others to complete before failure
                pid = f.readline()
                print >>sys.stderr, "%s has been locked for more than %d seconds by PID %s" % (lockfile, max_wait, pid)
                sys.exit(1)
            # it hasn't been locked too long; wait and try again
            f.close()
            time.sleep(1)

    # this process got the lock
    return fd


if __name__ == "__main__":

    lockfile = os.environ['HOME'] + "/.tunnelrunner.lock"
    lockfd = acquireLockFile(lockfile)
    os.write(lockfd,"%d\n" % os.getpid())

    cmd = [ 'ssh-askpass' ]
    cmd.extend(sys.argv[1:])
    returncode = subprocess.call(cmd)

    os.remove(lockfile)
    os.close(lockfd)

    sys.exit(returncode)