diff --git a/synapse/handlers/message.py b/synapse/handlers/message.py
index b743fc2dcc..522271eed1 100644
--- a/synapse/handlers/message.py
+++ b/synapse/handlers/message.py
@@ -852,6 +852,38 @@ class EventCreationHandler(object):
)
@defer.inlineCallbacks
+ def _validate_canonical_alias(
+ self, directory_handler, room_alias_str, expected_room_id
+ ):
+ """
+ Ensure that the given room alias points to the expected room ID.
+
+ Args:
+ directory_handler: The directory handler object.
+ room_alias_str: The room alias to check.
+ expected_room_id: The room ID that the alias should point to.
+ """
+ room_alias = RoomAlias.from_string(room_alias_str)
+ try:
+ mapping = yield directory_handler.get_association(room_alias)
+ except SynapseError as e:
+ # Turn M_NOT_FOUND errors into M_BAD_ALIAS errors.
+ if e.errcode == Codes.NOT_FOUND:
+ raise SynapseError(
+ 400,
+ "Room alias %s does not point to the room" % (room_alias_str,),
+ Codes.BAD_ALIAS,
+ )
+ raise
+
+ if mapping["room_id"] != expected_room_id:
+ raise SynapseError(
+ 400,
+ "Room alias %s does not point to the room" % (room_alias_str,),
+ Codes.BAD_ALIAS,
+ )
+
+ @defer.inlineCallbacks
def persist_and_notify_client_event(
self, requester, event, context, ratelimit=True, extra_users=[]
):
@@ -905,15 +937,9 @@ class EventCreationHandler(object):
room_alias_str = event.content.get("alias", None)
directory_handler = self.hs.get_handlers().directory_handler
if room_alias_str and room_alias_str != original_alias:
- room_alias = RoomAlias.from_string(room_alias_str)
- mapping = yield directory_handler.get_association(room_alias)
-
- if mapping["room_id"] != event.room_id:
- raise SynapseError(
- 400,
- "Room alias %s does not point to the room" % (room_alias_str,),
- Codes.BAD_ALIAS,
- )
+ yield self._validate_canonical_alias(
+ directory_handler, room_alias_str, event.room_id
+ )
# Check that alt_aliases is the proper form.
alt_aliases = event.content.get("alt_aliases", [])
@@ -931,16 +957,9 @@ class EventCreationHandler(object):
new_alt_aliases = set(alt_aliases) - set(original_alt_aliases)
if new_alt_aliases:
for alias_str in new_alt_aliases:
- room_alias = RoomAlias.from_string(alias_str)
- mapping = yield directory_handler.get_association(room_alias)
-
- if mapping["room_id"] != event.room_id:
- raise SynapseError(
- 400,
- "Room alias %s does not point to the room"
- % (room_alias_str,),
- Codes.BAD_ALIAS,
- )
+ yield self._validate_canonical_alias(
+ directory_handler, alias_str, event.room_id
+ )
federation_handler = self.hs.get_handlers().federation_handler
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