Add basic impl for room history ACL on GET /messages client API

synapse/handlers/message.py

@@ -113,11 +113,42 @@ class MessageHandler(BaseHandler):
             "room_key", next_key
         )
 
+        if not events:
+            defer.returnValue({
+                "chunk": [],
+                "start": pagin_config.from_token.to_string(),
+                "end": next_token.to_string(),
+            })
+
+        states = yield self.store.get_state_for_events(
+            room_id, [e.event_id for e in events],
+        )
+
+        events_and_states = zip(events, states)
+
+        def allowed(event_and_state):
+            _, state = event_and_state
+
+            membership = state.get((EventTypes.Member, user_id), None)
+            if membership and membership.membership == Membership.JOIN:
+                return True
+
+            history = state.get((EventTypes.RoomHistoryVisibility, ''), None)
+            if history and history.content["visibility"] == "after_join":
+                return False
+
+        events_and_states = filter(allowed, events_and_states)
+        events = [
+            ev
+            for ev, _ in events_and_states
+        ]
+
         time_now = self.clock.time_msec()
 
         chunk = {
             "chunk": [
-                serialize_event(e, time_now, as_client_event) for e in events
+                serialize_event(e, time_now, as_client_event)
+                for e in events
             ],
             "start": pagin_config.from_token.to_string(),
             "end": next_token.to_string(),