root / vncauthproxy.py @ 5da701ba
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#!/usr/bin/env python
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#
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# Copyright (c) 2010 Apollon Oikonomopoulos
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#
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# This program is free software; you can redistribute it and/or modify
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# it under the terms of the GNU General Public License as published by
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# the Free Software Foundation; either version 2 of the License, or
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# (at your option) any later version.
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#
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# This program is distributed in the hope that it will be useful, but
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# WITHOUT ANY WARRANTY; without even the implied warranty of
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# MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
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# General Public License for more details.
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#
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# You should have received a copy of the GNU General Public License
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# along with this program; if not, write to the Free Software
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# Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA
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# 02110-1301, USA.
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import os |
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import sys |
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import logging |
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import gevent |
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import rfb |
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from gevent import socket |
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from gevent.select import select |
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class VncAuthProxy(gevent.Greenlet): |
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"""
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Simple class implementing a VNC Forwarder with MITM authentication as a
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Greenlet
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VncAuthProxy forwards VNC traffic from a specified port of the local host
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to a specified remote host:port. Furthermore, it implements VNC
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Authentication, intercepting the client/server handshake and asking the
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client for authentication even if the backend requires none.
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It is primarily intended for use in virtualization environments, as a VNC
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``switch''.
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"""
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id = 1
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def __init__(self, sport, daddr, dport, password, connect_timeout=30): |
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"""
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@type sport: int
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@param sport: source port
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@type daddr: str
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@param daddr: destination address (IPv4, IPv6 or hostname)
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@type dport: int
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@param dport: destination port
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@type password: str
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@param password: password to request from the client
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@type connect_timeout: int
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@param connect_timeout: how long to wait for client connections
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(seconds)
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"""
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gevent.Greenlet.__init__(self)
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self.id = VncAuthProxy.id
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VncAuthProxy.id += 1
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self.sport = sport
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self.daddr = daddr
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self.dport = dport
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self.password = password
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self.log = logging
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self.server = None |
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self.client = None |
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self.timeout = connect_timeout
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def _cleanup(self): |
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"""Close all active sockets and exit gracefully"""
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if self.server: |
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self.server.close()
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if self.client: |
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self.client.close()
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raise gevent.GreenletExit
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def info(self, msg): |
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logging.info("[C%d] %s" % (self.id, msg)) |
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def debug(self, msg): |
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logging.debug("[C%d] %s" % (self.id, msg)) |
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def warn(self, msg): |
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logging.warn("[C%d] %s" % (self.id, msg)) |
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def error(self, msg): |
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logging.error("[C%d] %s" % (self.id, msg)) |
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def critical(self, msg): |
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logging.critical("[C%d] %s" % (self.id, msg)) |
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def __str__(self): |
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return "VncAuthProxy: %d -> %s:%d" % (self.sport, self.daddr, self.dport) |
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def _forward(self, source, dest): |
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"""
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Forward traffic from source to dest
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@type source: socket
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@param source: source socket
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@type dest: socket
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@param dest: destination socket
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"""
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while True: |
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d = source.recv(8096)
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if d == '': |
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if source == self.client: |
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self.info("Client connection closed") |
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else:
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self.info("Server connection closed") |
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break
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dest.sendall(d) |
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source.close() |
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dest.close() |
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def _handshake(self): |
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"""
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Perform handshake/authentication with a connecting client
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Outline:
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1. Client connects
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2. We fake RFB 3.8 protocol and require VNC authentication
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3. Client accepts authentication method
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4. We send an authentication challenge
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5. Client sends the authentication response
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6. We check the authentication
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7. We initiate a connection with the backend server and perform basic
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RFB 3.8 handshake with it.
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8. If the above is successful, "bridge" both connections through two
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"fowrarder" greenlets.
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"""
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self.client.send(rfb.RFB_VERSION_3_8 + "\n") |
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client_version = self.client.recv(1024) |
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if not rfb.check_version(client_version): |
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self.error("Invalid version: %s" % client_version) |
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self._cleanup()
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self.debug("Requesting authentication") |
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auth_request = rfb.make_auth_request(rfb.RFB_AUTHTYPE_VNC) |
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self.client.send(auth_request)
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res = self.client.recv(1024) |
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type = rfb.parse_client_authtype(res) |
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if type == rfb.RFB_AUTHTYPE_ERROR:
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self.warn("Client refused authentication: %s" % res[1:]) |
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else:
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self.debug("Client requested authtype %x" % type) |
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if type != rfb.RFB_AUTHTYPE_VNC: |
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self.error("Wrong auth type: %d" % type) |
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self.client.send(rfb.to_u32(rfb.RFB_AUTH_ERROR))
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self._cleanup()
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# Generate the challenge
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challenge = os.urandom(16)
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self.client.send(challenge)
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response = self.client.recv(1024) |
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if len(response) != 16: |
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self.error("Wrong response length %d, should be 16" % len(response)) |
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self._cleanup()
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if rfb.check_password(challenge, response, password):
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self.debug("Authentication successful!") |
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else:
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self.warn("Authentication failed") |
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self.client.send(rfb.to_u32(rfb.RFB_AUTH_ERROR))
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self._cleanup()
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# Accept the authentication
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self.client.send(rfb.to_u32(rfb.RFB_AUTH_SUCCESS))
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# Initiate server connection
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for res in socket.getaddrinfo(self.daddr, self.dport, socket.AF_UNSPEC, |
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socket.SOCK_STREAM, 0, socket.AI_PASSIVE):
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af, socktype, proto, canonname, sa = res |
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try:
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self.server = socket.socket(af, socktype, proto)
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except socket.error, msg:
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self.server = None |
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continue;
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try:
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self.debug("Connecting to %s:%s" % sa[:2]) |
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self.server.connect(sa)
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self.debug("Connection to %s:%s successful" % sa[:2]) |
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except socket.error, msg:
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self.server.close()
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self.server = None |
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continue;
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break
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if self.server is None: |
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self.error("Failed to connect to server") |
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self._cleanup()
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version = self.server.recv(1024) |
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if not rfb.check_version(version): |
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self.error("Unsupported RFB version: %s" % version.strip()) |
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self._cleanup()
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self.server.send(rfb.RFB_VERSION_3_8 + "\n") |
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res = self.server.recv(1024) |
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types = rfb.parse_auth_request(res) |
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if not types: |
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self.error("Error handshaking with the server") |
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self._cleanup()
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else:
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self.debug("Supported authentication types: %s" % |
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" ".join([str(x) for x in types])) |
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if rfb.RFB_AUTHTYPE_NONE not in types: |
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self.error("Error, server demands authentication") |
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self._cleanup()
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self.server.send(rfb.to_u8(rfb.RFB_AUTHTYPE_NONE))
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# Check authentication response
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res = self.server.recv(4) |
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res = rfb.from_u32(res) |
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if res != 0: |
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self.error("Authentication error") |
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self._cleanup()
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# Bridge client/server connections
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self.workers = [gevent.spawn(self._forward, self.client, self.server), |
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gevent.spawn(self._forward, self.server, self.client)] |
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gevent.joinall(self.workers)
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del self.workers |
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self._cleanup()
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def _run(self): |
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sockets = [] |
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# Use two sockets, one for IPv4, one for IPv6. IPv4-to-IPv6 mapped
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# addresses do not work reliably everywhere (under linux it may have
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# been disabled in /proc/sys/net/ipv6/bind_ipv6_only).
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for res in socket.getaddrinfo(None, self.sport, socket.AF_UNSPEC, |
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socket.SOCK_STREAM, 0, socket.AI_PASSIVE):
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af, socktype, proto, canonname, sa = res |
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try:
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s = socket.socket(af, socktype, proto) |
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if af == socket.AF_INET6:
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# Bind v6 only when AF_INET6, otherwise either v4 or v6 bind
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# will fail.
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s.setsockopt(socket.IPPROTO_IPV6, socket.IPV6_V6ONLY, 1)
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except socket.error, msg:
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s = None
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continue;
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try:
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s.bind(sa) |
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s.listen(1)
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self.debug("Listening on %s:%d" % sa[:2]) |
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except socket.error, msg:
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self.error("Error binding to %s:%d: %s" % |
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(sa[0], sa[1], msg[1])) |
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s.close() |
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s = None
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continue
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if s:
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sockets.append(s) |
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if not sockets: |
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self.error("Failed to listen for connections") |
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self._cleanup()
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self.log.debug("Waiting for client to connect") |
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rlist, _, _ = select(sockets, [], [], timeout=self.timeout)
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if not rlist: |
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self.info("Timed out, no connection after %d sec" % self.timeout) |
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self._cleanup()
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for sock in rlist: |
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self.client, addrinfo = sock.accept()
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self.info("Connection from %s:%d" % addrinfo[:2]) |
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# Close all listening sockets, we only want a one-shot connection
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# from a single client.
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for listener in sockets: |
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listener.close() |
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break
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self._handshake()
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if __name__ == '__main__': |
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from optparse import OptionParser |
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parser = OptionParser() |
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parser.add_option("-s", "--socket", dest="ctrl_socket", |
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help="UNIX socket path for control connections",
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default="/tmp/vncproxy.sock",
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metavar="PATH")
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parser.add_option("-d", "--debug", action="store_true", dest="debug", |
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help="Enable debugging information")
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parser.add_option("-l", "--log", dest="logfile", default=None, |
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help="Write log to FILE instead of stdout",
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metavar="FILE")
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parser.add_option("-t", "--connect-timeout", dest="connect_timeout", |
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default=30, type="int", metavar="SECONDS", |
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help="How long to listen for clients to forward")
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(opts, args) = parser.parse_args(sys.argv[1:])
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lvl = logging.DEBUG if opts.debug else logging.INFO |
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logging.basicConfig(level=lvl, filename=opts.logfile, |
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format="%(asctime)s %(levelname)s: %(message)s",
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datefmt="%m/%d/%Y %H:%M:%S")
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if os.path.exists(opts.ctrl_socket):
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logging.critical("Socket '%s' already exists" % opts.ctrl_socket)
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sys.exit(1)
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# TODO: make this tunable? chgrp as well?
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old_umask = os.umask(0077)
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ctrl = socket.socket(socket.AF_UNIX, socket.SOCK_STREAM) |
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ctrl.bind(opts.ctrl_socket) |
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os.umask(old_umask) |
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ctrl.listen(1)
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logging.info("Initalized, waiting for control connections at %s" %
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opts.ctrl_socket) |
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while True: |
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try:
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client, addr = ctrl.accept() |
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except KeyboardInterrupt: |
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break
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logging.info("New control connection")
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line = client.recv(1024).strip()
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try:
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# Control message format:
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# TODO: make this json-based?
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# TODO: support multiple forwardings in the same message?
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# <source_port>:<destination_address>:<destination_port>:<password>
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# <password> will be used for MITM authentication of clients
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# connecting to <source_port>, who will subsequently be forwarded
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# to a VNC server at <destination_address>:<destination_port>
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sport, daddr, dport, password = line.split(':', 3) |
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logging.info("New forwarding [%d -> %s:%d]" %
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(int(sport), daddr, int(dport))) |
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except:
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logging.warn("Malformed request: %s" % line)
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client.send("FAILED\n")
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client.close() |
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continue
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client.send("OK\n")
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VncAuthProxy.spawn(sport, daddr, dport, password, opts.connect_timeout) |
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client.close() |
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os.unlink(opts.ctrl_socket) |
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sys.exit(0)
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