path: root/xmpp/transports.py

##   transports.py
##
##   Copyright (C) 2003-2004 Alexey "Snake" Nezhdanov
##
##   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, 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.

# $Id: transports.py, v1.36 2013/11/03 alkorgun Exp $

"""
This module contains the low-level implementations of xmpppy connect methods or
(in other words) transports for xmpp-stanzas.
Currently here is three transports:
direct TCP connect - TCPsocket class
proxied TCP connect - HTTPPROXYsocket class (CONNECT proxies)
TLS connection - TLS class. Can be used for SSL connections also.

Transports are stackable so you - f.e. TLS use HTPPROXYsocket or TCPsocket as more low-level transport.

Also exception 'error' is defined to allow capture of this module specific exceptions.
"""

import sys
import socket
import dispatcher

from base64 import encodestring
from select import select
from simplexml import ustr
from plugin import PlugIn
from protocol import *

# http://pydns.sourceforge.net
try:
	import dns
except ImportError:
	dns = None

DATA_RECEIVED = 'DATA RECEIVED'
DATA_SENT = 'DATA SENT'
DBG_CONNECT_PROXY = 'CONNECTproxy'

BUFLEN = 1024

class error:
	"""
	An exception to be raised in case of low-level errors in methods of 'transports' module.
	"""
	def __init__(self, comment):
		"""
		Cache the descriptive string.
		"""
		self._comment = comment

	def __str__(self):
		"""
		Serialize exception into pre-cached descriptive string.
		"""
		return self._comment

class TCPsocket(PlugIn):
	"""
	This class defines direct TCP connection method.
	"""
	def __init__(self, server=None, use_srv=True):
		"""
		Cache connection point 'server'. 'server' is the tuple of (host, port)
		absolutely the same as standard tcp socket uses. However library will lookup for
		('_xmpp-client._tcp.' + host) SRV record in DNS and connect to the found (if it is)
		server instead.
		"""
		PlugIn.__init__(self)
		self.DBG_LINE = "socket"
		self._exported_methods = [self.send, self.disconnect]
		self._server, self.use_srv = server, use_srv

	def srv_lookup(self, server):
		"""
		SRV resolver. Takes server=(host, port) as argument. Returns new (host, port) pair.
		"""
		if dns:
			query = "_xmpp-client._tcp.%s" % server[0]
			try:
				dns.DiscoverNameServers()
				dns__ = dns.Request()
				response = dns__.req(query, qtype="SRV")
				if response.answers:
					(port, host) = response.answers[0]["data"][2:]
					server = str(host), int(port)
			except dns.DNSError:
				self.DEBUG("An error occurred while looking up %s." % query, "warn")
		return server

	def plugin(self, owner):
		"""
		Fire up connection. Return non-empty string on success.
		Also registers self.disconnected method in the owner's dispatcher.
		Called internally.
		"""
		if not self._server:
			self._server = (self._owner.Server, 5222)
		if self.use_srv:
			server = self.srv_lookup(self._server)
		else:
			server = self._server
		if not self.connect(server):
			return None
		self._owner.Connection = self
		self._owner.RegisterDisconnectHandler(self.disconnected)
		return "ok"

	def getHost(self):
		"""
		Returns the 'host' value that is connection is [will be] made to.
		"""
		return self._server[0]

	def getPort(self):
		"""
		Returns the 'port' value that is connection is [will be] made to.
		"""
		return self._server[1]

	def connect(self, server=None):
		"""
		Try to connect to the given host/port. Does not lookup for SRV record.
		Returns non-empty string on success.
		"""
		if not server:
			server = self._server
		host, port = server
		server = (host, int(port))
		if ":" in host:
			sock = socket.AF_INET6
			server = server.__add__((0, 0))
		else:
			sock = socket.AF_INET
		try:
			self._sock = socket.socket(sock, socket.SOCK_STREAM)
			self._sock.connect(server)
			self._send = self._sock.sendall
			self._recv = self._sock.recv
		except socket.error as error:
			try:
				code, error = error
			except Exception:
				code = -1
			self.DEBUG("Failed to connect to remote host %s: %s (%s)" % (repr(server), error, code), "error")
		except Exception:
			pass
		else:
			self.DEBUG("Successfully connected to remote host %s." % repr(server), "start")
			return "ok"

	def plugout(self):
		"""
		Disconnect from the remote server and unregister self.disconnected method from
		the owner's dispatcher.
		"""
		self._sock.close()
		if hasattr(self._owner, "Connection"):
			del self._owner.Connection
			self._owner.UnregisterDisconnectHandler(self.disconnected)

	def receive(self):
		"""
		Reads all pending incoming data.
		In case of disconnection calls owner's disconnected() method and then raises IOError exception.
		"""
		try:
			data = self._recv(BUFLEN)
		except socket.sslerror as e:
			self._seen_data = 0
			if e[0] in (socket.SSL_ERROR_WANT_READ, socket.SSL_ERROR_WANT_WRITE):
				return ""
			self.DEBUG("Socket error while receiving data.", "error")
			sys.exc_clear()
			self._owner.disconnected()
			raise IOError("Disconnected!")
		except Exception:
			data = ""
		while self.pending_data(0):
			try:
				add = self._recv(BUFLEN)
			except Exception:
				break
			if not add:
				break
			data += add
		if data:
			self._seen_data = 1
			self.DEBUG(data, "got")
			if hasattr(self._owner, "Dispatcher"):
				self._owner.Dispatcher.Event("", DATA_RECEIVED, data)
		else:
			self.DEBUG("Socket error while receiving data.", "error")
			sys.exc_clear()
			self._owner.disconnected()
			raise IOError("Disconnected!")
		return data

	def send(self, data, timeout=0.002):
		"""
		Writes raw outgoing data. Blocks until done.
		If supplied data is unicode string, encodes it to utf-8 before send.
		"""
		if isinstance(data, unicode):
			data = data.encode("utf-8")
		elif not isinstance(data, str):
			data = ustr(data).encode("utf-8")
		while not select((), [self._sock], (), timeout)[1]:
			pass
		else:
			try:
				self._send(data)
			except Exception:
				self.DEBUG("Socket error while sending data.", "error")
				self._owner.disconnected()
			else:
				if not data.strip():
					data = repr(data)
				self.DEBUG(data, "sent")
				if hasattr(self._owner, "Dispatcher"):
					self._owner.Dispatcher.Event("", DATA_SENT, data)

	def pending_data(self, timeout=0):
		"""
		Returns true if there is a data ready to be read.
		"""
		return select([self._sock], [], [], timeout)[0]

	def disconnect(self):
		"""
		Closes the socket.
		"""
		self.DEBUG("Closing socket.", "stop")
		self._sock.close()

	def disconnected(self):
		"""
		Called when a Network Error or disconnection occurs.
		Designed to be overidden.
		"""
		self.DEBUG("Socket operation failed.", "error")

class HTTPPROXYsocket(TCPsocket):
	"""
	HTTP (CONNECT) proxy connection class. Uses TCPsocket as the base class
	redefines only connect method. Allows to use HTTP proxies like squid with
	(optionally) simple authentication (using login and password).
	"""
	def __init__(self, proxy, server, use_srv=True):
		"""
		Caches proxy and target addresses.
		'proxy' argument is a dictionary with mandatory keys 'host' and 'port' (proxy address)
		and optional keys 'user' and 'password' to use for authentication.
		'server' argument is a tuple of host and port - just like TCPsocket uses.
		"""
		TCPsocket.__init__(self, server, use_srv)
		self.DBG_LINE = DBG_CONNECT_PROXY
		self._proxy = proxy

	def plugin(self, owner):
		"""
		Starts connection. Used interally. Returns non-empty string on success.
		"""
		owner.debug_flags.append(DBG_CONNECT_PROXY)
		return TCPsocket.plugin(self, owner)

	def connect(self, dupe=None):
		"""
		Starts connection. Connects to proxy, supplies login and password to it
		(if were specified while creating instance). Instructs proxy to make
		connection to the target server. Returns non-empty sting on success.
		"""
		if not TCPsocket.connect(self, (self._proxy["host"], self._proxy["port"])):
			return None
		self.DEBUG("Proxy server contacted, performing authentification.", "start")
		connector = [
			"CONNECT %s:%s HTTP/1.0" % self._server,
			"Proxy-Connection: Keep-Alive",
			"Pragma: no-cache",
			"Host: %s:%s" % self._server,
			"User-Agent: HTTPPROXYsocket/v0.1"
		]
		if "user" in self._proxy and "password" in self._proxy:
			credentials = "%s:%s" % (self._proxy["user"], self._proxy["password"])
			credentials = encodestring(credentials).strip()
			connector.append("Proxy-Authorization: Basic " + credentials)
		connector.append("\r\n")
		self.send("\r\n".join(connector))
		try:
			reply = self.receive().replace("\r", "")
		except IOError:
			self.DEBUG("Proxy suddenly disconnected.", "error")
			self._owner.disconnected()
			return None
		try:
			proto, code, desc = reply.split("\n")[0].split(" ", 2)
		except Exception:
			raise error("Invalid proxy reply")
		if code != "200":
			self.DEBUG("Invalid proxy reply: %s %s %s" % (proto, code, desc), "error")
			self._owner.disconnected()
			return None
		while reply.find("\n\n") == -1:
			try:
				reply += self.receive().replace("\r", "")
			except IOError:
				self.DEBUG("Proxy suddenly disconnected.", "error")
				self._owner.disconnected()
				return None
		self.DEBUG("Authentification successfull. Jabber server contacted.", "ok")
		return "ok"

	def DEBUG(self, text, severity):
		"""
		Overwrites DEBUG tag to allow debug output be presented as 'CONNECTproxy'.
		"""
		return self._owner.DEBUG(DBG_CONNECT_PROXY, text, severity)

class TLS(PlugIn):
	"""
	TLS connection used to encrypts already estabilished tcp connection.
	"""
	def PlugIn(self, owner, now=0):
		"""
		If the 'now' argument is true then starts using encryption immidiatedly.
		If 'now' in false then starts encryption as soon as TLS feature is
		declared by the server (if it were already declared - it is ok).
		"""
		if hasattr(owner, "TLS"):
			return None
		PlugIn.PlugIn(self, owner)
		DBG_LINE = "TLS"
		if now:
			return self._startSSL()
		if self._owner.Dispatcher.Stream.features:
			try:
				self.FeaturesHandler(self._owner.Dispatcher, self._owner.Dispatcher.Stream.features)
			except NodeProcessed:
				pass
		else:
			self._owner.RegisterHandlerOnce("features", self.FeaturesHandler, xmlns=NS_STREAMS)
		self.starttls = None

	def plugout(self, now=0):
		"""
		Unregisters TLS handler's from owner's dispatcher. Take note that encription
		can not be stopped once started. You can only break the connection and start over.
		"""
		self._owner.UnregisterHandler("features", self.FeaturesHandler, xmlns=NS_STREAMS)
		self._owner.UnregisterHandler("proceed", self.StartTLSHandler, xmlns=NS_TLS)
		self._owner.UnregisterHandler("failure", self.StartTLSHandler, xmlns=NS_TLS)

	def FeaturesHandler(self, conn, feats):
		"""
		Used to analyse server <features/> tag for TLS support.
		If TLS is supported starts the encryption negotiation. Used internally.
		"""
		if not feats.getTag("starttls", namespace=NS_TLS):
			self.DEBUG("TLS unsupported by remote server.", "warn")
			return None
		self.DEBUG("TLS supported by remote server. Requesting TLS start.", "ok")
		self._owner.RegisterHandlerOnce("proceed", self.StartTLSHandler, xmlns=NS_TLS)
		self._owner.RegisterHandlerOnce("failure", self.StartTLSHandler, xmlns=NS_TLS)
		self._owner.Connection.send("<starttls xmlns=\"%s\"/>" % NS_TLS)
		raise NodeProcessed()

	def pending_data(self, timeout=0):
		"""
		Returns true if there possible is a data ready to be read.
		"""
		return self._tcpsock._seen_data or select([self._tcpsock._sock], [], [], timeout)[0]

	def _startSSL(self):
		tcpsock = self._owner.Connection
		tcpsock._sslObj = socket.ssl(tcpsock._sock, None, None)
		tcpsock._sslIssuer = tcpsock._sslObj.issuer()
		tcpsock._sslServer = tcpsock._sslObj.server()
		tcpsock._recv = tcpsock._sslObj.read
		tcpsock._send = tcpsock._sslObj.write
		tcpsock._seen_data = 1
		self._tcpsock = tcpsock
		tcpsock.pending_data = self.pending_data
		tcpsock._sock.setblocking(0)
		self.starttls = "success"

	def StartTLSHandler(self, conn, starttls):
		"""
		Handle server reply if TLS is allowed to process. Behaves accordingly.
		Used internally.
		"""
		if starttls.getNamespace() != NS_TLS:
			return None
		self.starttls = starttls.getName()
		if self.starttls == "failure":
			self.DEBUG("Got starttls response: " + self.starttls, "error")
			return None
		self.DEBUG("Got starttls proceed response. Switching to TLS/SSL...", "ok")
		self._startSSL()
		self._owner.Dispatcher.PlugOut()
		dispatcher.Dispatcher().PlugIn(self._owner)