diff --git a/synapse/handlers/message.py b/synapse/handlers/message.py
index 7b2c33a922..792edc7579 100644
--- a/synapse/handlers/message.py
+++ b/synapse/handlers/message.py
@@ -22,7 +22,7 @@ from canonicaljson import encode_canonical_json, json
from twisted.internet import defer
from twisted.internet.defer import succeed
-from synapse.api.constants import EventTypes, Membership
+from synapse.api.constants import EventTypes, Membership, RelationTypes
from synapse.api.errors import (
AuthError,
Codes,
@@ -601,6 +601,20 @@ class EventCreationHandler(object):
self.validator.validate_new(event)
+ # If this event is an annotation then we check that that the sender
+ # can't annotate the same way twice (e.g. stops users from liking an
+ # event multiple times).
+ relation = event.content.get("m.relates_to", {})
+ if relation.get("rel_type") == RelationTypes.ANNOTATION:
+ relates_to = relation["event_id"]
+ aggregation_key = relation["key"]
+
+ already_exists = yield self.store.has_user_annotated_event(
+ relates_to, event.type, aggregation_key, event.sender,
+ )
+ if already_exists:
+ raise SynapseError(400, "Can't send same reaction twice")
+
logger.debug(
"Created event %s",
event.event_id,
|
