1 files changed, 54 insertions, 0 deletions
diff --git a/synapse/handlers/federation.py b/synapse/handlers/federation.py
index b5d882fd65..d7f197f247 100644
--- a/synapse/handlers/federation.py
+++ b/synapse/handlers/federation.py
@@ -31,6 +31,8 @@ from synapse.crypto.event_signing import (
 )
 from synapse.types import UserID
 
+from synapse.events.utils import prune_event
+
 from synapse.util.retryutils import NotRetryingDestination
 
 from twisted.internet import defer
@@ -222,6 +224,56 @@ class FederationHandler(BaseHandler):
                     "user_joined_room", user=user, room_id=event.room_id
                 )
 
+    @defer.inlineCallbacks
+    def _filter_events_for_server(self, server_name, room_id, events):
+        states = yield self.store.get_state_for_events(
+            room_id, [e.event_id for e in events],
+        )
+
+        events_and_states = zip(events, states)
+
+        def redact_disallowed(event_and_state):
+            event, state = event_and_state
+
+            if not state:
+                return event
+
+            history = state.get((EventTypes.RoomHistoryVisibility, ''), None)
+            if history:
+                visibility = history.content.get("history_visibility", "shared")
+                if visibility in ["invited", "joined"]:
+                    # We now loop through all state events looking for
+                    # membership states for the requesting server to determine
+                    # if the server is either in the room or has been invited
+                    # into the room.
+                    for ev in state.values():
+                        if ev.type != EventTypes.Member:
+                            continue
+                        try:
+                            domain = UserID.from_string(ev.state_key).domain
+                        except:
+                            continue
+
+                        if domain != server_name:
+                            continue
+
+                        memtype = ev.membership
+                        if memtype == Membership.JOIN:
+                            return event
+                        elif memtype == Membership.INVITE:
+                            if visibility == "invited":
+                                return event
+                    else:
+                        return prune_event(event)
+
+            return event
+
+        res = map(redact_disallowed, events_and_states)
+
+        logger.info("_filter_events_for_server %r", res)
+
+        defer.returnValue(res)
+
     @log_function
     @defer.inlineCallbacks
     def backfill(self, dest, room_id, limit, extremities=[]):
@@ -882,6 +934,8 @@ class FederationHandler(BaseHandler):
             limit
         )
 
+        events = yield self._filter_events_for_server(origin, room_id, events)
+
         defer.returnValue(events)
 
     @defer.inlineCallbacks