1 files changed, 82 insertions, 4 deletions
diff --git a/synapse/crypto/context_factory.py b/synapse/crypto/context_factory.py
index a1e1d0d33a..1a391adec1 100644
--- a/synapse/crypto/context_factory.py
+++ b/synapse/crypto/context_factory.py
@@ -11,19 +11,22 @@
 # 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.
-
 import logging
 
+from zope.interface import implementer
+
 from OpenSSL import SSL, crypto
-from twisted.internet import ssl
 from twisted.internet._sslverify import _defaultCurveName
+from twisted.internet.interfaces import IOpenSSLClientConnectionCreator
+from twisted.internet.ssl import CertificateOptions, ContextFactory
+from twisted.python.failure import Failure
 
 logger = logging.getLogger(__name__)
 
 
-class ServerContextFactory(ssl.ContextFactory):
+class ServerContextFactory(ContextFactory):
     """Factory for PyOpenSSL SSL contexts that are used to handle incoming
-    connections and to make connections to remote servers."""
+    connections."""
 
     def __init__(self, config):
         self._context = SSL.Context(SSL.SSLv23_METHOD)
@@ -48,3 +51,78 @@ class ServerContextFactory(ssl.ContextFactory):
 
     def getContext(self):
         return self._context
+
+
+def _idnaBytes(text):
+    """
+    Convert some text typed by a human into some ASCII bytes. This is a
+    copy of twisted.internet._idna._idnaBytes. For documentation, see the
+    twisted documentation.
+    """
+    try:
+        import idna
+    except ImportError:
+        return text.encode("idna")
+    else:
+        return idna.encode(text)
+
+
+def _tolerateErrors(wrapped):
+    """
+    Wrap up an info_callback for pyOpenSSL so that if something goes wrong
+    the error is immediately logged and the connection is dropped if possible.
+    This is a copy of twisted.internet._sslverify._tolerateErrors. For
+    documentation, see the twisted documentation.
+    """
+
+    def infoCallback(connection, where, ret):
+        try:
+            return wrapped(connection, where, ret)
+        except:  # noqa: E722, taken from the twisted implementation
+            f = Failure()
+            logger.exception("Error during info_callback")
+            connection.get_app_data().failVerification(f)
+
+    return infoCallback
+
+
+@implementer(IOpenSSLClientConnectionCreator)
+class ClientTLSOptions(object):
+    """
+    Client creator for TLS without certificate identity verification. This is a
+    copy of twisted.internet._sslverify.ClientTLSOptions with the identity
+    verification left out. For documentation, see the twisted documentation.
+    """
+
+    def __init__(self, hostname, ctx):
+        self._ctx = ctx
+        self._hostname = hostname
+        self._hostnameBytes = _idnaBytes(hostname)
+        ctx.set_info_callback(
+            _tolerateErrors(self._identityVerifyingInfoCallback)
+        )
+
+    def clientConnectionForTLS(self, tlsProtocol):
+        context = self._ctx
+        connection = SSL.Connection(context, None)
+        connection.set_app_data(tlsProtocol)
+        return connection
+
+    def _identityVerifyingInfoCallback(self, connection, where, ret):
+        if where & SSL.SSL_CB_HANDSHAKE_START:
+            connection.set_tlsext_host_name(self._hostnameBytes)
+
+
+class ClientTLSOptionsFactory(object):
+    """Factory for Twisted ClientTLSOptions that are used to make connections
+    to remote servers for federation."""
+
+    def __init__(self, config):
+        # We don't use config options yet
+        pass
+
+    def get_options(self, host):
+        return ClientTLSOptions(
+            host.decode('utf-8'),
+            CertificateOptions(verify=False).getContext()
+        )