tunnelrunner

#!/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 sys
import signal
import re
import termios
import fcntl

#Global so that the signal handler has access
tunnelRunner = None


def sighandler(signum, frame):
    """The signal handler"""
    if(signum != signal.SIGCHLD):
        tunnelRunner.stop(signum)



class TunnelRunner(object):
    """This class is used to execute an instance of an SSH tunnel"""

    def __init__(self, controller, argv):
        """This object constructor"""

        if(not controller in ('GUI','CLI')):
            print >>sys.stderr, "Error: unrecognized controller: %s" % controller

        self.controller = controller
        self.argv = [ "/usr/bin/ssh" ]
        self.argv.extend(argv)

	self.child = 0

	os.setuid(os.geteuid())


    def start(self):
	"""Start the tunnel"""

	signal.signal(signal.SIGCHLD, sighandler)
	signal.signal(signal.SIGTERM, sighandler)
	signal.signal(signal.SIGALRM, sighandler)
	signal.signal(signal.SIGHUP, sighandler)
	signal.signal(signal.SIGINT, sighandler)
	signal.signal(signal.SIGQUIT, sighandler)
	signal.signal(signal.SIGPIPE, sighandler)

	try:
	    self.rpipe, self.wpipe = os.pipe()
	    self.child = os.fork()
	except OSError, e:
	    print >>sys.stderr, "system call failed creating child: %d (%s)" % (e.errno, e.strerror)
	    sys.exit(1)

	if(self.child == 0):
	    #Child process here
	    stderr = 2
	    try:
                if(self.controller == "GUI"):
                    #GUI wants disconnect from controlling terminal
                    if(os.isatty(0)):
                        fcntl.ioctl(0,termios.TIOCNOTTY)
                    binPath = os.path.dirname(os.path.realpath(sys.argv[0]))
                    askpassCmd = binPath + "/tunnelrunner_askpass"
                    os.environ['SSH_ASKPASS'] = askpassCmd
		os.close(self.rpipe)
		devNull = os.open("/dev/null",os.O_WRONLY)
		os.dup2(devNull, 1)
		os.dup2(self.wpipe, 0)
		os.dup2(self.wpipe, 2)
		os.execv(self.argv[0], self.argv)
	    except OSError, e:
		print >>sys.stderr, "system call failed executing child: %d (%s)" % (e.errno, e.strerror)
                sys.exit(1)

        else:
            #Parent process here
            try:
                os.close(self.wpipe)
                while True:
                    line = os.read(self.rpipe, 1024)
                    if(line == ""):
                        #EOF here
                        pid,status = os.waitpid(self.child, 0)
                        exitcode = ((status&0xFF00)>>8)
                        sys.exit(exitcode)
                    else:
                        print >>sys.stderr, "%s" % line.rstrip()
                        if(re.compile('Could not request.*forwarding').search(line)):
                            sys.exit(1)
            except OSError, e:
                print >>sys.stderr, "system call failed executing parent: %d (%s)" % (e.errno, e.strerror)
                sys.exit(1)

        self.child = 0


    def stop(self,signum):
        """Stop the tunnel"""
        try:
            if(self.child != 0):
                os.kill(self.child,signum)
                signal.signal(signum,signal.SIG_DFL)
                os.kill(os.getpid(),signum)
        except OSError, e:
            print >>sys.stderr, "system call failed handling signal: %d (%s)" % (e.errno, e.strerror)



if __name__ == "__main__":
    tunnelRunner = TunnelRunner(sys.argv[1], sys.argv[2:])
    tunnelRunner.start()