better log messages when rejecting cross-origin requests

IPython/html/base/zmqhandlers.py

@@ -1,206 +1,214 b''
 """Tornado handlers for WebSocket <-> ZMQ sockets."""
 
 # Copyright (c) IPython Development Team.
 # Distributed under the terms of the Modified BSD License.
 
 import json
 
 try:
     from urllib.parse import urlparse # Py 3
 except ImportError:
     from urlparse import urlparse # Py 2
 
 try:
     from http.cookies import SimpleCookie  # Py 3
 except ImportError:
     from Cookie import SimpleCookie  # Py 2
 import logging
 
 import tornado
 from tornado import ioloop
 from tornado import web
 from tornado import websocket
 
 from IPython.kernel.zmq.session import Session
 from IPython.utils.jsonutil import date_default
 from IPython.utils.py3compat import PY3, cast_unicode
 
 from .handlers import IPythonHandler
 
 
 class ZMQStreamHandler(websocket.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 or host is None):
+        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:
-            return self.allow_origin == origin
+            allow = self.allow_origin == origin
         elif self.allow_origin_pat:
-            return bool(self.allow_origin_pat.match(origin))
+            allow = bool(self.allow_origin_pat.match(origin))
         else:
             # No CORS headers deny the request
-            self.log.warn("Cross Origin WebSocket Attempt from %s", self.get_origin())
-            return False
+            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, unserializes 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.unserialize(msg_list)
         try:
             msg['header'].pop('date')
         except KeyError:
             pass
         try:
             msg['parent_header'].pop('date')
         except KeyError:
             pass
         msg.pop('buffers')
         return json.dumps(msg, default=date_default)
 
     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)
 
     def allow_draft76(self):
         """Allow draft 76, until browsers such as Safari update to RFC 6455.
         
         This has been disabled by default in tornado in release 2.2.0, and
         support will be removed in later versions.
         """
         return True
 
 # ping interval for keeping websockets alive (30 seconds)
 WS_PING_INTERVAL = 30000
 
 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 open(self, kernel_id):
         self.kernel_id = cast_unicode(kernel_id, 'ascii')
         # Check to see that origin matches host directly, including ports
         # Tornado 4 already does CORS checking
         if tornado.version_info[0] < 4:
             if not self.check_origin(self.get_origin()):
                 raise web.HTTPError(403)
 
         self.session = Session(config=self.config)
         self.save_on_message = self.on_message
         self.on_message = self.on_first_message
         
         # 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()
 
     def _inject_cookie_message(self, msg):
         """Inject the first message, which is the document cookie,
         for authentication."""
         if not PY3 and isinstance(msg, unicode):
             # Cookie constructor doesn't accept unicode strings
             # under Python 2.x for some reason
             msg = msg.encode('utf8', 'replace')
         try:
             identity, msg = msg.split(':', 1)
             self.session.session = cast_unicode(identity, 'ascii')
         except Exception:
             logging.error("First ws message didn't have the form 'identity:[cookie]' - %r", msg)
         
         try:
             self.request._cookies = SimpleCookie(msg)
         except:
             self.log.warn("couldn't parse cookie string: %s",msg, exc_info=True)
 
     def on_first_message(self, msg):
         self._inject_cookie_message(msg)
         if self.get_current_user() is None:
             self.log.warn("Couldn't authenticate WebSocket connection")
             raise web.HTTPError(403)
         self.on_message = self.save_on_message