Allow upgrading a room only once

changelog.d/5045.bugfix

@@ -0,0 +1 @@
+Prevent the abiltiy to upgrade the same room more than once.

synapse/handlers/room.py

@@ -76,7 +76,9 @@ def __init__(self, hs):
 
  @defer.inlineCallbacks
  def upgrade_room(self, requester, old_room_id, new_version):
- """Replace a room with a new room with a different version
+ """Replace a room with a new room with a different version. Will
+ raise an exception if the room has already been upgraded, or in
+ currently in the process of being upgraded.
 
  Args:
  requester (synapse.types.Requester): the user requesting the upgrade
@@ -85,12 +87,22 @@ def upgrade_room(self, requester, old_room_id, new_version):
 
  Returns:
  Deferred[unicode]: the new room id
+
+ Raises:
+ NotFoundError if the room is unknown
+ SynapseError if this room has already been upgraded
  """
  yield self.ratelimit(requester)
 
  user_id = requester.user.to_string()
 
  with (yield self._upgrade_linearizer.queue(old_room_id)):
+ # Check that this room has not already been upgraded
+ tombstone = yield self.store.get_room_tombstone(old_room_id)
+
+ if tombstone is not None:
+ raise SynapseError(400, "This room has already been upgraded")
+
  # start by allocating a new room id
  r = yield self.store.get_room(old_room_id)
  if r is None:

synapse/storage/state.py

@@ -433,7 +433,8 @@ def get_room_predecessor(self, room_id):
  room_id (str)
 
  Returns:
- Deferred[unicode|None]: predecessor room id
+ Deferred[unicode|None]: predecessor room id, or None if a
+ predecessor is not found
 
  Raises:
  NotFoundError if the room is unknown
@@ -444,6 +445,33 @@ def get_room_predecessor(self, room_id):
  # Return predecessor if present
  defer.returnValue(create_event.content.get("predecessor", None))
 
+ @defer.inlineCallbacks
+ def get_room_tombstone(self, room_id):
+ """Get the tombstone event of an upgraded room if one exists.
+ Otherwise return None.
+
+ Args:
+ room_id (str)
+
+ Returns:
+ Deferred[FrozenEvent|None]: the tombstone event, or None if a
+ tombstone event was not found
+
+ Raises:
+ NotFoundError if the room is unknown
+ """
+ # Retrieve the room's tombstone event if it exists
+ state_ids = yield self.get_current_state_ids(room_id)
+ tombstone_id = state_ids.get((EventTypes.Tombstone, ""))
+
+ # If we can't find the tombstone, assume we've hit a dead end
+ if not tombstone_id:
+ defer.returnValue(None)
+
+ # Retrieve the room's tombstone event and return
+ tombstone_event = yield self.get_event(tombstone_id)
+ defer.returnValue(tombstone_event)
+
  @defer.inlineCallbacks
  def get_create_event_for_room(self, room_id):
  """Get the create state event for a room.