Synapse 0.33.3.1 (2018-09-06)

=============================
 
 SECURITY FIXES
 --------------
 
 - Fix an issue where event signatures were not always correctly validated ([\#3796](https://github.com/matrix-org/synapse/issues/3796))
 - Fix an issue where server_acls could be circumvented for incoming events ([\#3796](https://github.com/matrix-org/synapse/issues/3796))
 
 Internal Changes
 ----------------
 
 - Unignore synctl in .dockerignore to fix docker builds ([\#3802](https://github.com/matrix-org/synapse/issues/3802))
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Merge tag 'v0.33.3.1' into release-v0.33.4

Synapse 0.33.3.1 (2018-09-06)
=============================

SECURITY FIXES
--------------

- Fix an issue where event signatures were not always correctly validated ([\#3796](https://github.com/matrix-org/synapse/issues/3796))
- Fix an issue where server_acls could be circumvented for incoming events ([\#3796](https://github.com/matrix-org/synapse/issues/3796))

Internal Changes
----------------

- Unignore synctl in .dockerignore to fix docker builds ([\#3802](https://github.com/matrix-org/synapse/issues/3802))

CHANGES.md

@@ -1,3 +1,19 @@
+Synapse 0.33.3.1 (2018-09-06)
+=============================
+
+SECURITY FIXES
+--------------
+
+- Fix an issue where event signatures were not always correctly validated ([\#3796](https://github.com/matrix-org/synapse/issues/3796))
+- Fix an issue where server_acls could be circumvented for incoming events ([\#3796](https://github.com/matrix-org/synapse/issues/3796))
+
+
+Internal Changes
+----------------
+
+- Unignore synctl in .dockerignore to fix docker builds ([\#3802](https://github.com/matrix-org/synapse/issues/3802))
+
+
 Synapse 0.33.4rc1 (2018-09-04)
 ==============================
 
@@ -24,7 +40,6 @@ Bugfixes
 - Fix bug in sending presence over federation ([\#3768](https://github.com/matrix-org/synapse/issues/3768))
 - Fix bug where preserved threepid user comes to sign up and server is mau blocked ([\#3777](https://github.com/matrix-org/synapse/issues/3777))
 
-
 Internal Changes
 ----------------
 

synapse/federation/federation_base.py

@@ -13,17 +13,20 @@
 # See the License for the specific language governing permissions and
 # limitations under the License.
 import logging
+from collections import namedtuple
 
 import six
 
 from twisted.internet import defer
+from twisted.internet.defer import DeferredList
 
-from synapse.api.constants import MAX_DEPTH
+from synapse.api.constants import MAX_DEPTH, EventTypes, Membership
 from synapse.api.errors import Codes, SynapseError
 from synapse.crypto.event_signing import check_event_content_hash
 from synapse.events import FrozenEvent
 from synapse.events.utils import prune_event
 from synapse.http.servlet import assert_params_in_dict
+from synapse.types import get_domain_from_id
 from synapse.util import logcontext, unwrapFirstError
 
 logger = logging.getLogger(__name__)
@@ -133,34 +136,25 @@ class FederationBase(object):
               * throws a SynapseError if the signature check failed.
             The deferreds run their callbacks in the sentinel logcontext.
         """
-
-        redacted_pdus = [
-            prune_event(pdu)
-            for pdu in pdus
-        ]
-
-        deferreds = self.keyring.verify_json_objects_for_server([
-            (p.origin, p.get_pdu_json())
-            for p in redacted_pdus
-        ])
+        deferreds = _check_sigs_on_pdus(self.keyring, pdus)
 
         ctx = logcontext.LoggingContext.current_context()
 
-        def callback(_, pdu, redacted):
+        def callback(_, pdu):
             with logcontext.PreserveLoggingContext(ctx):
                 if not check_event_content_hash(pdu):
                     logger.warn(
                         "Event content has been tampered, redacting %s: %s",
                         pdu.event_id, pdu.get_pdu_json()
                     )
-                    return redacted
+                    return prune_event(pdu)
 
                 if self.spam_checker.check_event_for_spam(pdu):
                     logger.warn(
                         "Event contains spam, redacting %s: %s",
                         pdu.event_id, pdu.get_pdu_json()
                     )
-                    return redacted
+                    return prune_event(pdu)
 
                 return pdu
 
@@ -173,16 +167,116 @@ class FederationBase(object):
                 )
             return failure
 
-        for deferred, pdu, redacted in zip(deferreds, pdus, redacted_pdus):
+        for deferred, pdu in zip(deferreds, pdus):
             deferred.addCallbacks(
                 callback, errback,
-                callbackArgs=[pdu, redacted],
+                callbackArgs=[pdu],
                 errbackArgs=[pdu],
             )
 
         return deferreds
 
 
+class PduToCheckSig(namedtuple("PduToCheckSig", [
+    "pdu", "redacted_pdu_json", "event_id_domain", "sender_domain", "deferreds",
+])):
+    pass
+
+
+def _check_sigs_on_pdus(keyring, pdus):
+    """Check that the given events are correctly signed
+
+    Args:
+        keyring (synapse.crypto.Keyring): keyring object to do the checks
+        pdus (Collection[EventBase]): the events to be checked
+
+    Returns:
+        List[Deferred]: a Deferred for each event in pdus, which will either succeed if
+           the signatures are valid, or fail (with a SynapseError) if not.
+    """
+
+    # (currently this is written assuming the v1 room structure; we'll probably want a
+    # separate function for checking v2 rooms)
+
+    # we want to check that the event is signed by:
+    #
+    # (a) the server which created the event_id
+    #
+    # (b) the sender's server.
+    #
+    #     - except in the case of invites created from a 3pid invite, which are exempt
+    #     from this check, because the sender has to match that of the original 3pid
+    #     invite, but the event may come from a different HS, for reasons that I don't
+    #     entirely grok (why do the senders have to match? and if they do, why doesn't the
+    #     joining server ask the inviting server to do the switcheroo with
+    #     exchange_third_party_invite?).
+    #
+    #     That's pretty awful, since redacting such an invite will render it invalid
+    #     (because it will then look like a regular invite without a valid signature),
+    #     and signatures are *supposed* to be valid whether or not an event has been
+    #     redacted. But this isn't the worst of the ways that 3pid invites are broken.
+    #
+    # let's start by getting the domain for each pdu, and flattening the event back
+    # to JSON.
+    pdus_to_check = [
+        PduToCheckSig(
+            pdu=p,
+            redacted_pdu_json=prune_event(p).get_pdu_json(),
+            event_id_domain=get_domain_from_id(p.event_id),
+            sender_domain=get_domain_from_id(p.sender),
+            deferreds=[],
+        )
+        for p in pdus
+    ]
+
+    # first make sure that the event is signed by the event_id's domain
+    deferreds = keyring.verify_json_objects_for_server([
+        (p.event_id_domain, p.redacted_pdu_json)
+        for p in pdus_to_check
+    ])
+
+    for p, d in zip(pdus_to_check, deferreds):
+        p.deferreds.append(d)
+
+    # now let's look for events where the sender's domain is different to the
+    # event id's domain (normally only the case for joins/leaves), and add additional
+    # checks.
+    pdus_to_check_sender = [
+        p for p in pdus_to_check
+        if p.sender_domain != p.event_id_domain and not _is_invite_via_3pid(p.pdu)
+    ]
+
+    more_deferreds = keyring.verify_json_objects_for_server([
+        (p.sender_domain, p.redacted_pdu_json)
+        for p in pdus_to_check_sender
+    ])
+
+    for p, d in zip(pdus_to_check_sender, more_deferreds):
+        p.deferreds.append(d)
+
+    # replace lists of deferreds with single Deferreds
+    return [_flatten_deferred_list(p.deferreds) for p in pdus_to_check]
+
+
+def _flatten_deferred_list(deferreds):
+    """Given a list of one or more deferreds, either return the single deferred, or
+    combine into a DeferredList.
+    """
+    if len(deferreds) > 1:
+        return DeferredList(deferreds, fireOnOneErrback=True, consumeErrors=True)
+    else:
+        assert len(deferreds) == 1
+        return deferreds[0]
+
+
+def _is_invite_via_3pid(event):
+    return (
+        event.type == EventTypes.Member
+        and event.membership == Membership.INVITE
+        and "third_party_invite" in event.content
+    )
+
+
 def event_from_pdu_json(pdu_json, outlier=False):
     """Construct a FrozenEvent from an event json received over federation
 

synapse/federation/federation_server.py

@@ -99,7 +99,7 @@ class FederationServer(FederationBase):
 
     @defer.inlineCallbacks
     @log_function
-    def on_incoming_transaction(self, transaction_data):
+    def on_incoming_transaction(self, origin, transaction_data):
         # keep this as early as possible to make the calculated origin ts as
         # accurate as possible.
         request_time = self._clock.time_msec()
@@ -108,34 +108,33 @@ class FederationServer(FederationBase):
 
         if not transaction.transaction_id:
             raise Exception("Transaction missing transaction_id")
-        if not transaction.origin:
-            raise Exception("Transaction missing origin")
 
         logger.debug("[%s] Got transaction", transaction.transaction_id)
 
         # use a linearizer to ensure that we don't process the same transaction
         # multiple times in parallel.
         with (yield self._transaction_linearizer.queue(
-                (transaction.origin, transaction.transaction_id),
+                (origin, transaction.transaction_id),
         )):
             result = yield self._handle_incoming_transaction(
-                transaction, request_time,
+                origin, transaction, request_time,
             )
 
         defer.returnValue(result)
 
     @defer.inlineCallbacks
-    def _handle_incoming_transaction(self, transaction, request_time):
+    def _handle_incoming_transaction(self, origin, transaction, request_time):
         """ Process an incoming transaction and return the HTTP response
 
         Args:
+            origin (unicode): the server making the request
             transaction (Transaction): incoming transaction
             request_time (int): timestamp that the HTTP request arrived at
 
         Returns:
             Deferred[(int, object)]: http response code and body
         """
-        response = yield self.transaction_actions.have_responded(transaction)
+        response = yield self.transaction_actions.have_responded(origin, transaction)
 
         if response:
             logger.debug(
@@ -149,7 +148,7 @@ class FederationServer(FederationBase):
 
         received_pdus_counter.inc(len(transaction.pdus))
 
-        origin_host, _ = parse_server_name(transaction.origin)
+        origin_host, _ = parse_server_name(origin)
 
         pdus_by_room = {}
 
@@ -190,7 +189,7 @@ class FederationServer(FederationBase):
                 event_id = pdu.event_id
                 try:
                     yield self._handle_received_pdu(
-                        transaction.origin, pdu
+                        origin, pdu
                     )
                     pdu_results[event_id] = {}
                 except FederationError as e:
@@ -212,7 +211,7 @@ class FederationServer(FederationBase):
         if hasattr(transaction, "edus"):
             for edu in (Edu(**x) for x in transaction.edus):
                 yield self.received_edu(
-                    transaction.origin,
+                    origin,
                     edu.edu_type,
                     edu.content
                 )
@@ -224,6 +223,7 @@ class FederationServer(FederationBase):
         logger.debug("Returning: %s", str(response))
 
         yield self.transaction_actions.set_response(
+            origin,
             transaction,
             200, response
         )

synapse/federation/persistence.py

@@ -36,7 +36,7 @@ class TransactionActions(object):
         self.store = datastore
 
     @log_function
-    def have_responded(self, transaction):
+    def have_responded(self, origin, transaction):
         """ Have we already responded to a transaction with the same id and
         origin?
 
@@ -50,11 +50,11 @@ class TransactionActions(object):
                                "transaction_id")
 
         return self.store.get_received_txn_response(
-            transaction.transaction_id, transaction.origin
+            transaction.transaction_id, origin
         )
 
     @log_function
-    def set_response(self, transaction, code, response):
+    def set_response(self, origin, transaction, code, response):
         """ Persist how we responded to a transaction.
 
         Returns:
@@ -66,7 +66,7 @@ class TransactionActions(object):
 
         return self.store.set_received_txn_response(
             transaction.transaction_id,
-            transaction.origin,
+            origin,
             code,
             response,
         )

synapse/federation/transport/server.py

@@ -353,7 +353,7 @@ class FederationSendServlet(BaseFederationServlet):
 
         try:
             code, response = yield self.handler.on_incoming_transaction(
-                transaction_data
+                origin, transaction_data,
             )
         except Exception:
             logger.exception("on_incoming_transaction failed")

tests/handlers/test_typing.py

@@ -33,7 +33,7 @@ from ..utils import (
 )
 
 
-def _expect_edu(destination, edu_type, content, origin="test"):
+def _expect_edu_transaction(edu_type, content, origin="test"):
     return {
         "origin": origin,
         "origin_server_ts": 1000000,
@@ -42,8 +42,8 @@ def _expect_edu(destination, edu_type, content, origin="test"):
     }
 
 
-def _make_edu_json(origin, edu_type, content):
-    return json.dumps(_expect_edu("test", edu_type, content, origin=origin)).encode(
+def _make_edu_transaction_json(edu_type, content):
+    return json.dumps(_expect_edu_transaction(edu_type, content)).encode(
         'utf8'
     )
 
@@ -190,8 +190,7 @@ class TypingNotificationsTestCase(unittest.TestCase):
             call(
                 "farm",
                 path="/_matrix/federation/v1/send/1000000/",
-                data=_expect_edu(
-                    "farm",
+                data=_expect_edu_transaction(
                     "m.typing",
                     content={
                         "room_id": self.room_id,
@@ -221,11 +220,10 @@ class TypingNotificationsTestCase(unittest.TestCase):
 
         self.assertEquals(self.event_source.get_current_key(), 0)
 
-        yield self.mock_federation_resource.trigger(
+        (code, response) = yield self.mock_federation_resource.trigger(
             "PUT",
             "/_matrix/federation/v1/send/1000000/",
-            _make_edu_json(
-                "farm",
+            _make_edu_transaction_json(
                 "m.typing",
                 content={
                     "room_id": self.room_id,
@@ -233,7 +231,7 @@ class TypingNotificationsTestCase(unittest.TestCase):
                     "typing": True,
                 },
             ),
-            federation_auth=True,
+            federation_auth_origin=b'farm',
         )
 
         self.on_new_event.assert_has_calls(
@@ -264,8 +262,7 @@ class TypingNotificationsTestCase(unittest.TestCase):
             call(
                 "farm",
                 path="/_matrix/federation/v1/send/1000000/",
-                data=_expect_edu(
-                    "farm",
+                data=_expect_edu_transaction(
                     "m.typing",
                     content={
                         "room_id": self.room_id,

tests/utils.py

@@ -321,7 +321,10 @@ class MockHttpResource(HttpServer):
 
     @patch('twisted.web.http.Request')
     @defer.inlineCallbacks
-    def trigger(self, http_method, path, content, mock_request, federation_auth=False):
+    def trigger(
+        self, http_method, path, content, mock_request,
+        federation_auth_origin=None,
+    ):
         """ Fire an HTTP event.
 
         Args:
@@ -330,6 +333,7 @@ class MockHttpResource(HttpServer):
             content : The HTTP body
             mock_request : Mocked request to pass to the event so it can get
                            content.
+            federation_auth_origin (bytes|None): domain to authenticate as, for federation
         Returns:
             A tuple of (code, response)
         Raises:
@@ -350,8 +354,10 @@ class MockHttpResource(HttpServer):
         mock_request.getClientIP.return_value = "-"
 
         headers = {}
-        if federation_auth:
-            headers[b"Authorization"] = [b"X-Matrix origin=test,key=,sig="]
+        if federation_auth_origin is not None:
+            headers[b"Authorization"] = [
+                b"X-Matrix origin=%s,key=,sig=" % (federation_auth_origin, )
+            ]
         mock_request.requestHeaders.getRawHeaders = mock_getRawHeaders(headers)
 
         # return the right path if the event requires it