4 files changed, 38 insertions, 1 deletions
diff --git a/synapse/handlers/federation.py b/synapse/handlers/federation.py
index 6c0bc7eafa..351b218247 100644
--- a/synapse/handlers/federation.py
+++ b/synapse/handlers/federation.py
@@ -1413,7 +1413,7 @@ class FederationHandler(BaseHandler):
                 local_view = dict(auth_events)
                 remote_view = dict(auth_events)
                 remote_view.update({
-                    (d.type, d.state_key): d for d in different_events
+                    (d.type, d.state_key): d for d in different_events if d
                 })
 
                 new_state, prev_state = self.state_handler.resolve_events(
diff --git a/synapse/handlers/message.py b/synapse/handlers/message.py
index 15caf1950a..878809d50d 100644
--- a/synapse/handlers/message.py
+++ b/synapse/handlers/message.py
@@ -51,6 +51,19 @@ class MessageHandler(BaseHandler):
         self.snapshot_cache = SnapshotCache()
 
     @defer.inlineCallbacks
+    def purge_history(self, room_id, event_id):
+        event = yield self.store.get_event(event_id)
+
+        if event.room_id != room_id:
+            raise SynapseError(400, "Event is for wrong room.")
+
+        depth = event.depth
+
+        # TODO: Lock.
+
+        yield self.store.delete_old_state(room_id, depth)
+
+    @defer.inlineCallbacks
     def get_messages(self, requester, room_id=None, pagin_config=None,
                      as_client_event=True):
         """Get messages in a room.
diff --git a/synapse/rest/client/v1/admin.py b/synapse/rest/client/v1/admin.py
index e54c472e08..71537a7d0b 100644
--- a/synapse/rest/client/v1/admin.py
+++ b/synapse/rest/client/v1/admin.py
@@ -77,6 +77,24 @@ class PurgeMediaCacheRestServlet(ClientV1RestServlet):
         defer.returnValue((200, ret))
 
 
+class PurgeHistoryRestServlet(ClientV1RestServlet):
+    PATTERNS = client_path_patterns(
+        "/admin/purge_history/(?P<room_id>[^/]*)/(?P<event_id>[^/]*)"
+    )
+
+    @defer.inlineCallbacks
+    def on_POST(self, request, room_id, event_id):
+        requester = yield self.auth.get_user_by_req(request)
+        is_admin = yield self.auth.is_server_admin(requester.user)
+
+        if not is_admin:
+            raise AuthError(403, "You are not a server admin")
+
+        yield self.handlers.message_handler.purge_history(room_id, event_id)
+
+        defer.returnValue((200, {}))
+
+
 class DeactivateAccountRestServlet(ClientV1RestServlet):
     PATTERNS = client_path_patterns("/admin/deactivate/(?P<target_user_id>[^/]*)")
 
diff --git a/synapse/storage/events.py b/synapse/storage/events.py
index 98c917ce15..c3b498bb3d 100644
--- a/synapse/storage/events.py
+++ b/synapse/storage/events.py
@@ -1281,6 +1281,12 @@ class EventsStore(SQLBaseStore):
             )
         return self.runInteraction("get_all_new_events", get_all_new_events_txn)
 
+    def delete_old_state(self, room_id, topological_ordering):
+        return self.runInteraction(
+            "delete_old_state",
+            self._delete_old_state_txn, room_id, topological_ordering
+        )
+
     def _delete_old_state_txn(self, txn, room_id, topological_ordering):
         """Deletes old room state
         """