Reference Matrix Home Server

synapse/crypto/keyclient.py

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+# -*- coding: utf-8 -*-
+# Copyright 2014 matrix.org
+#
+# Licensed under the Apache License, Version 2.0 (the "License");
+# you may not use this file except in compliance with the License.
+# You may obtain a copy of the License at
+#
+#     http://www.apache.org/licenses/LICENSE-2.0
+#
+# Unless required by applicable law or agreed to in writing, software
+# distributed under the License is distributed on an "AS IS" BASIS,
+# WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+# See the License for the specific language governing permissions and
+# limitations under the License.
+
+from twisted.web.http import HTTPClient
+from twisted.internet import defer, reactor
+from twisted.internet.protocol import ClientFactory
+from twisted.names.srvconnect import SRVConnector
+import json
+import logging
+
+
+logger = logging.getLogger(__name__)
+
+
+@defer.inlineCallbacks
+def fetch_server_key(server_name, ssl_context_factory):
+    """Fetch the keys for a remote server."""
+
+    factory = SynapseKeyClientFactory()
+
+    SRVConnector(
+        reactor, "matrix", server_name, factory,
+        protocol="tcp", connectFuncName="connectSSL", defaultPort=443,
+        connectFuncKwArgs=dict(contextFactory=ssl_context_factory)).connect()
+
+    server_key, server_certificate = yield factory.remote_key
+
+    defer.returnValue((server_key, server_certificate))
+
+
+class SynapseKeyClientError(Exception):
+    """The key wasn't retireved from the remote server."""
+    pass
+
+
+class SynapseKeyClientProtocol(HTTPClient):
+    """Low level HTTPS client which retrieves an application/json response from
+    the server and extracts the X.509 certificate for the remote peer from the
+    SSL connection."""
+
+    def connectionMade(self):
+        logger.debug("Connected to %s", self.transport.getHost())
+        self.sendCommand(b"GET", b"/key")
+        self.endHeaders()
+        self.timer = reactor.callLater(
+            self.factory.timeout_seconds,
+            self.on_timeout
+        )
+
+    def handleStatus(self, version, status, message):
+        if status != b"200":
+            logger.info("Non-200 response from %s: %s %s",
+                        self.transport.getHost(), status, message)
+            self.transport.abortConnection()
+
+    def handleResponse(self, response_body_bytes):
+        try:
+            json_response = json.loads(response_body_bytes)
+        except ValueError:
+            logger.info("Invalid JSON response from %s",
+                        self.transport.getHost())
+            self.transport.abortConnection()
+            return
+
+        certificate = self.transport.getPeerCertificate()
+        self.factory.on_remote_key((json_response, certificate))
+        self.transport.abortConnection()
+        self.timer.cancel()
+
+    def on_timeout(self):
+        logger.debug("Timeout waiting for response from %s",
+                     self.transport.getHost())
+        self.transport.abortConnection()
+
+
+class SynapseKeyClientFactory(ClientFactory):
+    protocol = SynapseKeyClientProtocol
+    max_retries = 5
+    timeout_seconds = 30
+
+    def __init__(self):
+        self.succeeded = False
+        self.retries = 0
+        self.remote_key = defer.Deferred()
+
+    def on_remote_key(self, key):
+        self.succeeded = True
+        self.remote_key.callback(key)
+
+    def retry_connection(self, connector):
+        self.retries += 1
+        if self.retries < self.max_retries:
+            connector.connector = None
+            connector.connect()
+        else:
+            self.remote_key.errback(
+                SynapseKeyClientError("Max retries exceeded"))
+
+    def clientConnectionFailed(self, connector, reason):
+        logger.info("Connection failed %s", reason)
+        self.retry_connection(connector)
+
+    def clientConnectionLost(self, connector, reason):
+        logger.info("Connection lost %s", reason)
+        if not self.succeeded:
+            self.retry_connection(connector)