noVNC/utils/websockify

#!/usr/bin/env python

'''
A WebSocket to TCP socket proxy with support for "wss://" encryption.
Copyright 2011 Joel Martin
Licensed under LGPL version 3 (see docs/LICENSE.LGPL-3)

You can make a cert/key with openssl using:
openssl req -new -x509 -days 365 -nodes -out self.pem -keyout self.pem
as taken from http://docs.python.org/dev/library/ssl.html#certificates

'''

import socket, optparse, time, os, sys, subprocess
from select import select
from websocket import WebSocketServer

class WebSocketProxy(WebSocketServer):
    """
    Proxy traffic to and from a WebSockets client to a normal TCP
    socket server target. All traffic to/from the client is base64
    encoded/decoded to allow binary data to be sent/received to/from
    the target.
    """

    buffer_size = 65536

    traffic_legend = """
Traffic Legend:
    }  - Client receive
    }. - Client receive partial
    {  - Target receive

    >  - Target send
    >. - Target send partial
    <  - Client send
    <. - Client send partial
"""

    def __init__(self, *args, **kwargs):
        # Save off proxy specific options
        self.target_host    = kwargs.pop('target_host')
        self.target_port    = kwargs.pop('target_port')
        self.wrap_cmd       = kwargs.pop('wrap_cmd')
        self.wrap_mode      = kwargs.pop('wrap_mode')
        # Last 3 timestamps command was run
        self.wrap_times    = [0, 0, 0]

        if self.wrap_cmd:
            rebinder_path = ['./', os.path.dirname(sys.argv[0])]
            self.rebinder = None

            for rdir in rebinder_path:
                rpath = os.path.join(rdir, "rebind.so")
                if os.path.exists(rpath):
                    self.rebinder = rpath
                    break

            if not self.rebinder:
                raise Exception("rebind.so not found, perhaps you need to run make")

            self.target_host = "127.0.0.1"  # Loopback
            # Find a free high port
            sock = socket.socket(socket.AF_INET, socket.SOCK_STREAM)
            sock.bind(('', 0))
            self.target_port = sock.getsockname()[1]
            sock.close()

            os.environ.update({
                "LD_PRELOAD": self.rebinder,
                "REBIND_OLD_PORT": str(kwargs['listen_port']),
                "REBIND_NEW_PORT": str(self.target_port)})

        WebSocketServer.__init__(self, *args, **kwargs)

    def run_wrap_cmd(self):
        print("Starting '%s'" % " ".join(self.wrap_cmd))
        self.wrap_times.append(time.time())
        self.wrap_times.pop(0)
        self.cmd = subprocess.Popen(
                self.wrap_cmd, env=os.environ)
        self.spawn_message = True

    def started(self):
        """
        Called after Websockets server startup (i.e. after daemonize)
        """
        # Need to call wrapped command after daemonization so we can
        # know when the wrapped command exits
        if self.wrap_cmd:
            print("  - proxying from %s:%s to '%s' (port %s)\n" % (
                    self.listen_host, self.listen_port,
                    " ".join(self.wrap_cmd), self.target_port))
            self.run_wrap_cmd()
        else:
            print("  - proxying from %s:%s to %s:%s\n" % (
                    self.listen_host, self.listen_port,
                    self.target_host, self.target_port))

    def poll(self):
        # If we are wrapping a command, check it's status

        if self.wrap_cmd and self.cmd:
            ret = self.cmd.poll()
            if ret != None:
                self.vmsg("Wrapped command exited (or daemon). Returned %s" % ret)
                self.cmd = None

        if self.wrap_cmd and self.cmd == None:
            # Response to wrapped command being gone
            if self.wrap_mode == "ignore":
                pass
            elif self.wrap_mode == "exit":
                sys.exit(ret)
            elif self.wrap_mode == "respawn":
                now = time.time()
                avg = sum(self.wrap_times)/len(self.wrap_times)
                if (now - avg) < 10:
                    # 3 times in the last 10 seconds
                    if self.spawn_message:
                        print("Command respawning too fast")
                        self.spawn_message = False
                else:
                    self.run_wrap_cmd()

    # 
    # Routines above this point are run in the master listener
    # process.
    #

    #
    # Routines below this point are connection handler routines and
    # will be run in a separate forked process for each connection.
    #

    def new_client(self):
        """
        Called after a new WebSocket connection has been established.
        """

        # Connect to the target
        self.msg("connecting to: %s:%s" % (
                 self.target_host, self.target_port))
        tsock = self.socket(self.target_host, self.target_port,
                connect=True)

        if self.verbose and not self.daemon:
            print(self.traffic_legend)

        # Start proxying
        try:
            self.do_proxy(tsock)
        except:
            if tsock:
                tsock.shutdown(socket.SHUT_RDWR)
                tsock.close()
                self.vmsg("%s:%s: Target closed" %(
                    self.target_host, self.target_port))
            raise

    def do_proxy(self, target):
        """
        Proxy client WebSocket to normal target socket.
        """
        cqueue = []
        c_pend = 0
        tqueue = []
        rlist = [self.client, target]

        while True:
            wlist = []

            if tqueue: wlist.append(target)
            if cqueue or c_pend: wlist.append(self.client)
            ins, outs, excepts = select(rlist, wlist, [], 1)
            if excepts: raise Exception("Socket exception")

            if target in outs:
                # Send queued client data to the target
                dat = tqueue.pop(0)
                sent = target.send(dat)
                if sent == len(dat):
                    self.traffic(">")
                else:
                    # requeue the remaining data
                    tqueue.insert(0, dat[sent:])
                    self.traffic(".>")


            if target in ins:
                # Receive target data, encode it and queue for client
                buf = target.recv(self.buffer_size)
                if len(buf) == 0: raise self.EClose("Target closed")

                cqueue.append(buf)
                self.traffic("{")


            if self.client in outs:
                # Send queued target data to the client
                c_pend = self.send_frames(cqueue)

                cqueue = []


            if self.client in ins:
                # Receive client data, decode it, and queue for target
                bufs, closed = self.recv_frames()
                tqueue.extend(bufs)

                if closed:
                    # TODO: What about blocking on client socket?
                    self.send_close()
                    raise self.EClose(closed)

if __name__ == '__main__':
    usage = "\n    %prog [options]"
    usage += " [source_addr:]source_port target_addr:target_port"
    usage += "\n    %prog [options]"
    usage += " [source_addr:]source_port -- WRAP_COMMAND_LINE"
    parser = optparse.OptionParser(usage=usage)
    parser.add_option("--verbose", "-v", action="store_true",
            help="verbose messages and per frame traffic")
    parser.add_option("--record",
            help="record sessions to FILE.[session_number]", metavar="FILE")
    parser.add_option("--daemon", "-D",
            dest="daemon", action="store_true",
            help="become a daemon (background process)")
    parser.add_option("--cert", default="self.pem",
            help="SSL certificate file")
    parser.add_option("--key", default=None,
            help="SSL key file (if separate from cert)")
    parser.add_option("--ssl-only", action="store_true",
            help="disallow non-encrypted connections")
    parser.add_option("--web", default=None, metavar="DIR",
            help="run webserver on same port. Serve files from DIR.")
    parser.add_option("--wrap-mode", default="exit", metavar="MODE",
            choices=["exit", "ignore", "respawn"],
            help="action to take when the wrapped program exits "
            "or daemonizes: exit (default), ignore, respawn")
    (opts, args) = parser.parse_args()

    # Sanity checks
    if len(args) < 2:
        parser.error("Too few arguments")
    if sys.argv.count('--'):
        opts.wrap_cmd = args[1:]
    else:
        opts.wrap_cmd = None
        if len(args) > 2:
            parser.error("Too many arguments")

    if opts.ssl_only and not os.path.exists(opts.cert):
        parser.error("SSL only and %s not found" % opts.cert)

    # Parse host:port and convert ports to numbers
    if args[0].count(':') > 0:
        opts.listen_host, sep, opts.listen_port = args[0].rpartition(':')
    else:
        opts.listen_host, opts.listen_port = '', args[0]

    try:    opts.listen_port = int(opts.listen_port)
    except: parser.error("Error parsing listen port")

    if opts.wrap_cmd:
        opts.target_host = None
        opts.target_port = None
    else:
        if args[1].count(':') > 0:
            opts.target_host, sep, opts.target_port = args[1].rpartition(':')
        else:
            parser.error("Error parsing target")
        try:    opts.target_port = int(opts.target_port)
        except: parser.error("Error parsing target port")

    # Create and start the WebSockets proxy
    server = WebSocketProxy(**opts.__dict__)
    server.start_server()