# coding: utf-8 """Tornado handlers for WebSocket <-> ZMQ sockets.""" # Copyright (c) IPython Development Team. # Distributed under the terms of the Modified BSD License. import os import json import struct import warnings try: from urllib.parse import urlparse # Py 3 except ImportError: from urlparse import urlparse # Py 2 import tornado from tornado import gen, ioloop, web from tornado.websocket import WebSocketHandler from IPython.kernel.zmq.session import Session from IPython.utils.jsonutil import date_default, extract_dates from IPython.utils.py3compat import cast_unicode from .handlers import IPythonHandler def serialize_binary_message(msg): """serialize a message as a binary blob Header: 4 bytes: number of msg parts (nbufs) as 32b int 4 * nbufs bytes: offset for each buffer as integer as 32b int Offsets are from the start of the buffer, including the header. Returns ------- The message serialized to bytes. """ # don't modify msg or buffer list in-place msg = msg.copy() buffers = list(msg.pop('buffers')) bmsg = json.dumps(msg, default=date_default).encode('utf8') buffers.insert(0, bmsg) nbufs = len(buffers) offsets = [4 * (nbufs + 1)] for buf in buffers[:-1]: offsets.append(offsets[-1] + len(buf)) offsets_buf = struct.pack('!' + 'I' * (nbufs + 1), nbufs, *offsets) buffers.insert(0, offsets_buf) return b''.join(buffers) def deserialize_binary_message(bmsg): """deserialize a message from a binary blog Header: 4 bytes: number of msg parts (nbufs) as 32b int 4 * nbufs bytes: offset for each buffer as integer as 32b int Offsets are from the start of the buffer, including the header. Returns ------- message dictionary """ nbufs = struct.unpack('!i', bmsg[:4])[0] offsets = list(struct.unpack('!' + 'I' * nbufs, bmsg[4:4*(nbufs+1)])) offsets.append(None) bufs = [] for start, stop in zip(offsets[:-1], offsets[1:]): bufs.append(bmsg[start:stop]) msg = json.loads(bufs[0].decode('utf8')) msg['header'] = extract_dates(msg['header']) msg['parent_header'] = extract_dates(msg['parent_header']) msg['buffers'] = bufs[1:] return msg # ping interval for keeping websockets alive (30 seconds) WS_PING_INTERVAL = 30000 if os.environ.get('IPYTHON_ALLOW_DRAFT_WEBSOCKETS_FOR_PHANTOMJS', False): warnings.warn("""Allowing draft76 websocket connections! This should only be done for testing with phantomjs!""") from IPython.html import allow76 WebSocketHandler = allow76.AllowDraftWebSocketHandler # draft 76 doesn't support ping WS_PING_INTERVAL = 0 class ZMQStreamHandler(WebSocketHandler): def check_origin(self, origin): """Check Origin == Host or Access-Control-Allow-Origin. Tornado >= 4 calls this method automatically, raising 403 if it returns False. We call it explicitly in `open` on Tornado < 4. """ if self.allow_origin == '*': return True host = self.request.headers.get("Host") # If no header is provided, assume we can't verify origin if origin is None: self.log.warn("Missing Origin header, rejecting WebSocket connection.") return False if host is None: self.log.warn("Missing Host header, rejecting WebSocket connection.") return False origin = origin.lower() origin_host = urlparse(origin).netloc # OK if origin matches host if origin_host == host: return True # Check CORS headers if self.allow_origin: allow = self.allow_origin == origin elif self.allow_origin_pat: allow = bool(self.allow_origin_pat.match(origin)) else: # No CORS headers deny the request allow = False if not allow: self.log.warn("Blocking Cross Origin WebSocket Attempt. Origin: %s, Host: %s", origin, host, ) return allow def clear_cookie(self, *args, **kwargs): """meaningless for websockets""" pass def _reserialize_reply(self, msg_list): """Reserialize a reply message using JSON. This takes the msg list from the ZMQ socket, deserializes it using self.session and then serializes the result using JSON. This method should be used by self._on_zmq_reply to build messages that can be sent back to the browser. """ idents, msg_list = self.session.feed_identities(msg_list) msg = self.session.deserialize(msg_list) if msg['buffers']: buf = serialize_binary_message(msg) return buf else: smsg = json.dumps(msg, default=date_default) return cast_unicode(smsg) def _on_zmq_reply(self, msg_list): # Sometimes this gets triggered when the on_close method is scheduled in the # eventloop but hasn't been called. if self.stream.closed(): return try: msg = self._reserialize_reply(msg_list) except Exception: self.log.critical("Malformed message: %r" % msg_list, exc_info=True) else: self.write_message(msg, binary=isinstance(msg, bytes)) class AuthenticatedZMQStreamHandler(ZMQStreamHandler, IPythonHandler): ping_callback = None last_ping = 0 last_pong = 0 @property def ping_interval(self): """The interval for websocket keep-alive pings. Set ws_ping_interval = 0 to disable pings. """ return self.settings.get('ws_ping_interval', WS_PING_INTERVAL) @property def ping_timeout(self): """If no ping is received in this many milliseconds, close the websocket connection (VPNs, etc. can fail to cleanly close ws connections). Default is max of 3 pings or 30 seconds. """ return self.settings.get('ws_ping_timeout', max(3 * self.ping_interval, WS_PING_INTERVAL) ) def set_default_headers(self): """Undo the set_default_headers in IPythonHandler which doesn't make sense for websockets """ pass def pre_get(self): """Run before finishing the GET request Extend this method to add logic that should fire before the websocket finishes completing. """ # authenticate the request before opening the websocket if self.get_current_user() is None: self.log.warn("Couldn't authenticate WebSocket connection") raise web.HTTPError(403) if self.get_argument('session_id', False): self.session.session = cast_unicode(self.get_argument('session_id')) else: self.log.warn("No session ID specified") @gen.coroutine def get(self, *args, **kwargs): # pre_get can be a coroutine in subclasses # assign and yield in two step to avoid tornado 3 issues res = self.pre_get() yield gen.maybe_future(res) super(AuthenticatedZMQStreamHandler, self).get(*args, **kwargs) def initialize(self): self.log.debug("Initializing websocket connection %s", self.request.path) self.session = Session(config=self.config) def open(self, *args, **kwargs): self.log.debug("Opening websocket %s", self.request.path) # start the pinging if self.ping_interval > 0: self.last_ping = ioloop.IOLoop.instance().time() # Remember time of last ping self.last_pong = self.last_ping self.ping_callback = ioloop.PeriodicCallback(self.send_ping, self.ping_interval) self.ping_callback.start() def send_ping(self): """send a ping to keep the websocket alive""" if self.stream.closed() and self.ping_callback is not None: self.ping_callback.stop() return # check for timeout on pong. Make sure that we really have sent a recent ping in # case the machine with both server and client has been suspended since the last ping. now = ioloop.IOLoop.instance().time() since_last_pong = 1e3 * (now - self.last_pong) since_last_ping = 1e3 * (now - self.last_ping) if since_last_ping < 2*self.ping_interval and since_last_pong > self.ping_timeout: self.log.warn("WebSocket ping timeout after %i ms.", since_last_pong) self.close() return self.ping(b'') self.last_ping = now def on_pong(self, data): self.last_pong = ioloop.IOLoop.instance().time()