diff --git a/changelog.d/13779.bugfix b/changelog.d/13779.bugfix
new file mode 100644
index 0000000000..a92c722c6e
--- /dev/null
+++ b/changelog.d/13779.bugfix
@@ -0,0 +1 @@
+Prevent clients from reporting nonexistent events.
\ No newline at end of file
diff --git a/synapse/rest/client/report_event.py b/synapse/rest/client/report_event.py
index e2b410cf32..9be5860221 100644
--- a/synapse/rest/client/report_event.py
+++ b/synapse/rest/client/report_event.py
@@ -16,7 +16,7 @@ import logging
from http import HTTPStatus
from typing import TYPE_CHECKING, Tuple
-from synapse.api.errors import Codes, SynapseError
+from synapse.api.errors import Codes, NotFoundError, SynapseError
from synapse.http.server import HttpServer
from synapse.http.servlet import RestServlet, parse_json_object_from_request
from synapse.http.site import SynapseRequest
@@ -39,6 +39,7 @@ class ReportEventRestServlet(RestServlet):
self.auth = hs.get_auth()
self.clock = hs.get_clock()
self.store = hs.get_datastores().main
+ self._event_handler = self.hs.get_event_handler()
async def on_POST(
self, request: SynapseRequest, room_id: str, event_id: str
@@ -61,6 +62,14 @@ class ReportEventRestServlet(RestServlet):
Codes.BAD_JSON,
)
+ event = await self._event_handler.get_event(
+ requester.user, room_id, event_id, show_redacted=False
+ )
+ if event is None:
+ raise NotFoundError(
+ "Unable to report event: it does not exist or you aren't able to see it."
+ )
+
await self.store.add_event_report(
room_id=room_id,
event_id=event_id,
diff --git a/tests/rest/client/test_report_event.py b/tests/rest/client/test_report_event.py
index 7cb1017a4a..1250685d39 100644
--- a/tests/rest/client/test_report_event.py
+++ b/tests/rest/client/test_report_event.py
@@ -73,6 +73,18 @@ class ReportEventTestCase(unittest.HomeserverTestCase):
data = {"reason": None, "score": None}
self._assert_status(400, data)
+ def test_cannot_report_nonexistent_event(self) -> None:
+ """
+ Tests that we don't accept event reports for events which do not exist.
+ """
+ channel = self.make_request(
+ "POST",
+ f"rooms/{self.room_id}/report/$nonsenseeventid:test",
+ {"reason": "i am very sad"},
+ access_token=self.other_user_tok,
+ )
+ self.assertEqual(404, channel.code, msg=channel.result["body"])
+
def _assert_status(self, response_status: int, data: JsonDict) -> None:
channel = self.make_request(
"POST", self.report_path, data, access_token=self.other_user_tok
|
