Log when we receive a /make_* request from a different origin

3 files changed, 38 insertions, 4 deletions

diff --git a/changelog.d/5744.bugfix b/changelog.d/5744.bugfix
new file mode 100644
index 0000000000..7b67ebb2d3
--- /dev/null
+++ b/changelog.d/5744.bugfix
@@ -0,0 +1 @@
+Log when we receive a `/make_*` request from a different origin.
diff --git a/synapse/federation/federation_server.py b/synapse/federation/federation_server.py
index 8c0a18b120..ed2b6d5eef 100644
--- a/synapse/federation/federation_server.py
+++ b/synapse/federation/federation_server.py
@@ -369,7 +369,7 @@ class FederationServer(FederationBase):
             logger.warn("Room version %s not in %s", room_version, supported_versions)
             raise IncompatibleRoomVersionError(room_version=room_version)
 
-        pdu = yield self.handler.on_make_join_request(room_id, user_id)
+        pdu = yield self.handler.on_make_join_request(origin, room_id, user_id)
         time_now = self._clock.time_msec()
         defer.returnValue(
             {"event": pdu.get_pdu_json(time_now), "room_version": room_version}
@@ -423,7 +423,7 @@ class FederationServer(FederationBase):
     def on_make_leave_request(self, origin, room_id, user_id):
         origin_host, _ = parse_server_name(origin)
         yield self.check_server_matches_acl(origin_host, room_id)
-        pdu = yield self.handler.on_make_leave_request(room_id, user_id)
+        pdu = yield self.handler.on_make_leave_request(origin, room_id, user_id)
 
         room_version = yield self.store.get_room_version(room_id)
 
diff --git a/synapse/handlers/federation.py b/synapse/handlers/federation.py
index 57be968c67..30b69af82c 100644
--- a/synapse/handlers/federation.py
+++ b/synapse/handlers/federation.py
@@ -1204,11 +1204,28 @@ class FederationHandler(BaseHandler):
 
     @defer.inlineCallbacks
     @log_function
-    def on_make_join_request(self, room_id, user_id):
+    def on_make_join_request(self, origin, room_id, user_id):
         """ We've received a /make_join/ request, so we create a partial
         join event for the room and return that. We do *not* persist or
         process it until the other server has signed it and sent it back.
+
+        Args:
+            origin (str): The (verified) server name of the requesting server.
+            room_id (str): Room to create join event in
+            user_id (str): The user to create the join for
+
+        Returns:
+            Deferred[FrozenEvent]
         """
+
+        if get_domain_from_id(user_id) != origin:
+            logger.info(
+                "Got /make_join request for user %r from different origin %s, ignoring",
+                user_id,
+                origin,
+            )
+            raise SynapseError(403, "User not from origin", Codes.FORBIDDEN)
+
         event_content = {"membership": Membership.JOIN}
 
         room_version = yield self.store.get_room_version(room_id)
@@ -1411,11 +1428,27 @@ class FederationHandler(BaseHandler):
 
     @defer.inlineCallbacks
     @log_function
-    def on_make_leave_request(self, room_id, user_id):
+    def on_make_leave_request(self, origin, room_id, user_id):
         """ We've received a /make_leave/ request, so we create a partial
         leave event for the room and return that. We do *not* persist or
         process it until the other server has signed it and sent it back.
+
+        Args:
+            origin (str): The (verified) server name of the requesting server.
+            room_id (str): Room to create leave event in
+            user_id (str): The user to create the leave for
+
+        Returns:
+            Deferred[FrozenEvent]
         """
+        if get_domain_from_id(user_id) != origin:
+            logger.info(
+                "Got /make_leave request for user %r from different origin %s, ignoring",
+                user_id,
+                origin,
+            )
+            raise SynapseError(403, "User not from origin", Codes.FORBIDDEN)
+
         room_version = yield self.store.get_room_version(room_id)
         builder = self.event_builder_factory.new(
             room_version,