knockknock-daemon.py

#!/usr/bin/env python
"""knockknock-daemon implements Moxie Marlinspike's port knocking protocol."""

__author__ = "Moxie Marlinspike"
__email__  = "moxie@thoughtcrime.org"
__license__= """
Copyright (c) 2009 Moxie Marlinspike <moxie@thoughtcrime.org>

This program is free software; you can redistribute it and/or
modify it under the terms of the GNU General Public License as
published by the Free Software Foundation; either version 2 of the
License, or (at your option) any later version.

This program 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 this program; if not, write to the Free Software
Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA 02111-1307
USA

"""

import os, sys, pwd, grp

from knockknock.LogEntry import LogEntry
from knockknock.LogFile import LogFile
from knockknock.Profiles import Profiles
from knockknock.PortOpener import PortOpener
from knockknock.DaemonConfiguration import DaemonConfiguration
from knockknock.KnockWatcher import KnockWatcher

import knockknock.daemonize

def checkPrivileges():
    if (not os.geteuid() == 0):
        print "Sorry, you have to run knockknock-daemon as root."
        sys.exit(3)

def checkConfiguration():
    if (not os.path.isdir('/etc/knockknock.d/')):
        print "/etc/knockknock.d/ does not exist.  You need to setup your profiles first.."
        sys.exit(3)

    if (not os.path.isdir('/etc/knockknock.d/profiles/')):
        print "/etc/knockknock.d/profiles/ does not exist.  You need to setup your profiles first..."
        sys.exit(3)

def dropPrivileges():
    nobody = pwd.getpwnam('nobody')
    adm    = grp.getgrnam('adm')

    os.setgroups([adm.gr_gid])
    os.setgid(adm.gr_gid)
    os.setuid(nobody.pw_uid)

def handleFirewall(input, config):
    portOpener = PortOpener(input, config.getDelay())
    portOpener.waitForRequests()

def handleKnocks(output, profiles, config):
    dropPrivileges()
    
    logFile      = LogFile('/var/log/kern.log')
    portOpener   = PortOpener(output, config.getDelay())
    knockWatcher = KnockWatcher(config, logFile, profiles, portOpener)

    knockWatcher.tailAndProcess()

def main(argv):
    checkPrivileges()
    checkConfiguration()

    profiles   = Profiles('/etc/knockknock.d/profiles/')
    config     = DaemonConfiguration('/etc/knockknock.d/config')

    if (profiles.isEmpty()):
        print 'WARNING: Running knockknock-daemon without any active profiles.'

    knockknock.daemonize.createDaemon()

    input, output = os.pipe()
    pid           = os.fork()

    if pid:
        os.close(input)
        handleKnocks(os.fdopen(output, 'w'), profiles, config)
    else:
        os.close(output)
        handleFirewall(os.fdopen(input, 'r'), config)
                
if __name__ == '__main__':
    main(sys.argv[1:])