Merge tag 'v1.41.1'

Synapse 1.41.1 (2021-08-31)
===========================

Due to the two security issues highlighted below, server administrators are encouraged to update Synapse. We are not aware of these vulnerabilities being exploited in the wild.

Security advisory
-----------------

The following issues are fixed in v1.41.1.

- **[GHSA-3x4c-pq33-4w3q](GHSA-3x4c-pq33-4w3q) / [CVE-2021-39164](https://cve.mitre.org/cgi-bin/cvename.cgi?name=CVE-2021-39164): Enumerating a private room's list of members and their display names.**

  If an unauthorized user both knows the Room ID of a private room *and* that room's history visibility is set to `shared`, then they may be able to enumerate the room's members, including their display names.

  The unauthorized user must be on the same homeserver as a user who is a member of the target room.

  Fixed by [52c7a51](matrix-org@52c7a51cf).

- **[GHSA-jj53-8fmw-f2w2](GHSA-jj53-8fmw-f2w2) / [CVE-2021-39163](https://cve.mitre.org/cgi-bin/cvename.cgi?name=CVE-2021-39163): Disclosing a private room's name, avatar, topic, and number of members.**

  If an unauthorized user knows the Room ID of a private room, then its name, avatar, topic, and number of members may be disclosed through Group / Community features.

  The unauthorized user must be on the same homeserver as a user who is a member of the target room, and their homeserver must allow non-administrators to create groups (`enable_group_creation` in the Synapse configuration; off by default).

  Fixed by [cb35df9](matrix-org@cb35df940a), [\matrix-org#10723](matrix-org#10723).

Bugfixes
--------

- Fix a regression introduced in Synapse 1.41 which broke email transmission on systems using older versions of the Twisted library. ([\matrix-org#10713](matrix-org#10713))

CHANGES.md

@@ -1,3 +1,35 @@
+Synapse 1.41.1 (2021-08-31)
+===========================
+
+Due to the two security issues highlighted below, server administrators are encouraged to update Synapse. We are not aware of these vulnerabilities being exploited in the wild.
+
+Security advisory
+-----------------
+
+The following issues are fixed in v1.41.1.
+
+- **[GHSA-3x4c-pq33-4w3q](https://github.com/matrix-org/synapse/security/advisories/GHSA-3x4c-pq33-4w3q) / [CVE-2021-39164](https://cve.mitre.org/cgi-bin/cvename.cgi?name=CVE-2021-39164): Enumerating a private room's list of members and their display names.**
+
+  If an unauthorized user both knows the Room ID of a private room *and* that room's history visibility is set to `shared`, then they may be able to enumerate the room's members, including their display names.
+
+  The unauthorized user must be on the same homeserver as a user who is a member of the target room.
+
+  Fixed by [52c7a51cf](https://github.com/matrix-org/synapse/commit/52c7a51cf).
+
+- **[GHSA-jj53-8fmw-f2w2](https://github.com/matrix-org/synapse/security/advisories/GHSA-jj53-8fmw-f2w2) / [CVE-2021-39163](https://cve.mitre.org/cgi-bin/cvename.cgi?name=CVE-2021-39163): Disclosing a private room's name, avatar, topic, and number of members.**
+
+  If an unauthorized user knows the Room ID of a private room, then its name, avatar, topic, and number of members may be disclosed through Group / Community features.
+
+  The unauthorized user must be on the same homeserver as a user who is a member of the target room, and their homeserver must allow non-administrators to create groups (`enable_group_creation` in the Synapse configuration; off by default).
+
+  Fixed by [cb35df940a](https://github.com/matrix-org/synapse/commit/cb35df940a), [\#10723](https://github.com/matrix-org/synapse/issues/10723).
+
+Bugfixes
+--------
+
+- Fix a regression introduced in Synapse 1.41 which broke email transmission on systems using older versions of the Twisted library. ([\#10713](https://github.com/matrix-org/synapse/issues/10713))
+
+
 Synapse 1.41.0 (2021-08-24)
 ===========================
 

changelog.d/10713.bugfix

@@ -0,0 +1 @@
+Fix a regression introduced in Synapse 1.41 which broke email transmission on Systems using older versions of the Twisted library.

changelog.d/10723.bugfix

@@ -0,0 +1 @@
+Fix unauthorised exposure of room metadata to communities.

debian/changelog

@@ -1,3 +1,9 @@
+matrix-synapse-py3 (1.41.1) stable; urgency=high
+
+  * New synapse release 1.41.1.
+
+ -- Synapse Packaging team <[email protected]>  Tue, 31 Aug 2021 12:59:10 +0100
+
 matrix-synapse-py3 (1.41.0) stable; urgency=medium
 
   * New synapse release 1.41.0.

mypy.ini

@@ -87,6 +87,7 @@ files =
   tests/test_utils,
   tests/handlers/test_password_providers.py,
   tests/handlers/test_room_summary.py,
+  tests/handlers/test_send_email.py,
   tests/rest/client/v1/test_login.py,
   tests/rest/client/v2_alpha/test_auth.py,
   tests/util/test_itertools.py,

synapse/__init__.py

@@ -47,7 +47,7 @@
 except ImportError:
     pass
 
-__version__ = "1.41.0"
+__version__ = "1.41.1"
 
 if bool(os.environ.get("SYNAPSE_TEST_PATCH_LOG_CONTEXTS", False)):
     # We import here so that we don't have to install a bunch of deps when

synapse/groups/groups_server.py

@@ -332,6 +332,13 @@ async def get_rooms_in_group(
             requester_user_id, group_id
         )
 
+        # Note! room_results["is_public"] is about whether the room is considered
+        # public from the group's point of view. (i.e. whether non-group members
+        # should be able to see the room is in the group).
+        # This is not the same as whether the room itself is public (in the sense
+        # of being visible in the room directory).
+        # As such, room_results["is_public"] itself is not sufficient to determine
+        # whether any given user is permitted to see the room's metadata.
         room_results = await self.store.get_rooms_in_group(
             group_id, include_private=is_user_in_group
         )
@@ -341,8 +348,15 @@ async def get_rooms_in_group(
             room_id = room_result["room_id"]
 
             joined_users = await self.store.get_users_in_room(room_id)
+
+            # check the user is actually allowed to see the room before showing it to them
+            allow_private = requester_user_id in joined_users
+
             entry = await self.room_list_handler.generate_room_entry(
-                room_id, len(joined_users), with_alias=False, allow_private=True
+                room_id,
+                len(joined_users),
+                with_alias=False,
+                allow_private=allow_private,
             )
 
             if not entry:
@@ -354,7 +368,7 @@ async def get_rooms_in_group(
 
         chunk.sort(key=lambda e: -e["num_joined_members"])
 
-        return {"chunk": chunk, "total_room_count_estimate": len(room_results)}
+        return {"chunk": chunk, "total_room_count_estimate": len(chunk)}
 
 
 class GroupsServerHandler(GroupsServerWorkerHandler):

synapse/handlers/message.py

@@ -183,20 +183,37 @@ async def get_state_events(
 
             if not last_events:
                 raise NotFoundError("Can't find event for token %s" % (at_token,))
+            last_event = last_events[0]
+
+            # check whether the user is in the room at that time to determine
+            # whether they should be treated as peeking.
+            state_map = await self.state_store.get_state_for_event(
+                last_event.event_id,
+                StateFilter.from_types([(EventTypes.Member, user_id)]),
+            )
+
+            joined = False
+            membership_event = state_map.get((EventTypes.Member, user_id))
+            if membership_event:
+                joined = membership_event.membership == Membership.JOIN
+
+            is_peeking = not joined
 
             visible_events = await filter_events_for_client(
                 self.storage,
                 user_id,
                 last_events,
                 filter_send_to_client=False,
+                is_peeking=is_peeking,
             )
 
-            event = last_events[0]
             if visible_events:
                 room_state_events = await self.state_store.get_state_for_events(
-                    [event.event_id], state_filter=state_filter
+                    [last_event.event_id], state_filter=state_filter
                 )
-                room_state: Mapping[Any, EventBase] = room_state_events[event.event_id]
+                room_state: Mapping[Any, EventBase] = room_state_events[
+                    last_event.event_id
+                ]
             else:
                 raise AuthError(
                     403,

synapse/handlers/send_email.py

@@ -19,9 +19,12 @@
 from io import BytesIO
 from typing import TYPE_CHECKING, Optional
 
+from pkg_resources import parse_version
+
+import twisted
 from twisted.internet.defer import Deferred
-from twisted.internet.interfaces import IReactorTCP
-from twisted.mail.smtp import ESMTPSenderFactory
+from twisted.internet.interfaces import IOpenSSLContextFactory, IReactorTCP
+from twisted.mail.smtp import ESMTPSender, ESMTPSenderFactory
 
 from synapse.logging.context import make_deferred_yieldable
 
@@ -30,6 +33,19 @@
 
 logger = logging.getLogger(__name__)
 
+_is_old_twisted = parse_version(twisted.__version__) < parse_version("21")
+
+
+class _NoTLSESMTPSender(ESMTPSender):
+    """Extend ESMTPSender to disable TLS
+
+    Unfortunately, before Twisted 21.2, ESMTPSender doesn't give an easy way to disable
+    TLS, so we override its internal method which it uses to generate a context factory.
+    """
+
+    def _getContextFactory(self) -> Optional[IOpenSSLContextFactory]:
+        return None
+
 
 async def _sendmail(
     reactor: IReactorTCP,
@@ -42,7 +58,7 @@ async def _sendmail(
     password: Optional[bytes] = None,
     require_auth: bool = False,
     require_tls: bool = False,
-    tls_hostname: Optional[str] = None,
+    enable_tls: bool = True,
 ) -> None:
     """A simple wrapper around ESMTPSenderFactory, to allow substitution in tests
 
@@ -57,24 +73,37 @@ async def _sendmail(
         password: password to give when authenticating
         require_auth: if auth is not offered, fail the request
         require_tls: if TLS is not offered, fail the reqest
-        tls_hostname: TLS hostname to check for. None to disable TLS.
+        enable_tls: True to enable TLS. If this is False and require_tls is True,
+           the request will fail.
     """
     msg = BytesIO(msg_bytes)
-
     d: "Deferred[object]" = Deferred()
 
-    factory = ESMTPSenderFactory(
-        username,
-        password,
-        from_addr,
-        to_addr,
-        msg,
-        d,
-        heloFallback=True,
-        requireAuthentication=require_auth,
-        requireTransportSecurity=require_tls,
-        hostname=tls_hostname,
-    )
+    def build_sender_factory(**kwargs) -> ESMTPSenderFactory:
+        return ESMTPSenderFactory(
+            username,
+            password,
+            from_addr,
+            to_addr,
+            msg,
+            d,
+            heloFallback=True,
+            requireAuthentication=require_auth,
+            requireTransportSecurity=require_tls,
+            **kwargs,
+        )
+
+    if _is_old_twisted:
+        # before twisted 21.2, we have to override the ESMTPSender protocol to disable
+        # TLS
+        factory = build_sender_factory()
+
+        if not enable_tls:
+            factory.protocol = _NoTLSESMTPSender
+    else:
+        # for twisted 21.2 and later, there is a 'hostname' parameter which we should
+        # set to enable TLS.
+        factory = build_sender_factory(hostname=smtphost if enable_tls else None)
 
     # the IReactorTCP interface claims host has to be a bytes, which seems to be wrong
     reactor.connectTCP(smtphost, smtpport, factory, timeout=30, bindAddress=None)  # type: ignore[arg-type]
@@ -154,5 +183,5 @@ async def send_email(
             password=self._smtp_pass,
             require_auth=self._smtp_user is not None,
             require_tls=self._require_transport_security,
-            tls_hostname=self._smtp_host if self._enable_tls else None,
+            enable_tls=self._enable_tls,
         )

tests/handlers/test_send_email.py

@@ -0,0 +1,112 @@
+# Copyright 2021 The Matrix.org Foundation C.I.C.
+#
+# 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 typing import List, Tuple
+
+from zope.interface import implementer
+
+from twisted.internet import defer
+from twisted.internet.address import IPv4Address
+from twisted.internet.defer import ensureDeferred
+from twisted.mail import interfaces, smtp
+
+from tests.server import FakeTransport
+from tests.unittest import HomeserverTestCase
+
+
+@implementer(interfaces.IMessageDelivery)
+class _DummyMessageDelivery:
+    def __init__(self):
+        # (recipient, message) tuples
+        self.messages: List[Tuple[smtp.Address, bytes]] = []
+
+    def receivedHeader(self, helo, origin, recipients):
+        return None
+
+    def validateFrom(self, helo, origin):
+        return origin
+
+    def record_message(self, recipient: smtp.Address, message: bytes):
+        self.messages.append((recipient, message))
+
+    def validateTo(self, user: smtp.User):
+        return lambda: _DummyMessage(self, user)
+
+
+@implementer(interfaces.IMessageSMTP)
+class _DummyMessage:
+    """IMessageSMTP implementation which saves the message delivered to it
+    to the _DummyMessageDelivery object.
+    """
+
+    def __init__(self, delivery: _DummyMessageDelivery, user: smtp.User):
+        self._delivery = delivery
+        self._user = user
+        self._buffer: List[bytes] = []
+
+    def lineReceived(self, line):
+        self._buffer.append(line)
+
+    def eomReceived(self):
+        message = b"\n".join(self._buffer) + b"\n"
+        self._delivery.record_message(self._user.dest, message)
+        return defer.succeed(b"saved")
+
+    def connectionLost(self):
+        pass
+
+
+class SendEmailHandlerTestCase(HomeserverTestCase):
+    def test_send_email(self):
+        """Happy-path test that we can send email to a non-TLS server."""
+        h = self.hs.get_send_email_handler()
+        d = ensureDeferred(
+            h.send_email(
+                "[email protected]", "test subject", "Tests", "HTML content", "Text content"
+            )
+        )
+        # there should be an attempt to connect to localhost:25
+        self.assertEqual(len(self.reactor.tcpClients), 1)
+        (host, port, client_factory, _timeout, _bindAddress) = self.reactor.tcpClients[
+            0
+        ]
+        self.assertEqual(host, "localhost")
+        self.assertEqual(port, 25)
+
+        # wire it up to an SMTP server
+        message_delivery = _DummyMessageDelivery()
+        server_protocol = smtp.ESMTP()
+        server_protocol.delivery = message_delivery
+        # make sure that the server uses the test reactor to set timeouts
+        server_protocol.callLater = self.reactor.callLater  # type: ignore[assignment]
+
+        client_protocol = client_factory.buildProtocol(None)
+        client_protocol.makeConnection(FakeTransport(server_protocol, self.reactor))
+        server_protocol.makeConnection(
+            FakeTransport(
+                client_protocol,
+                self.reactor,
+                peer_address=IPv4Address("TCP", "127.0.0.1", 1234),
+            )
+        )
+
+        # the message should now get delivered
+        self.get_success(d, by=0.1)
+
+        # check it arrived
+        self.assertEqual(len(message_delivery.messages), 1)
+        user, msg = message_delivery.messages.pop()
+        self.assertEqual(str(user), "[email protected]")
+        self.assertIn(b"Subject: test subject", msg)