Repository: matrix-org/synapse

Issue:
Admin API endpoint to delete a reported event
**Description:**

Currently the [event reports API](https://matrix-org.github.io/synapse/latest/admin_api/event_reports.html) can be used to list all reported events stored in a synapse instance.

While this is enough to browse events, AFAIK there is no way to delete elements from this list of reported events, eg. to delete  a report considered invalid by an admin or by the report author.

I would expect being able to do something like:

```
DELETE /_synapse/admin/v1/event_reports/<event_report_id>
```


Discussion:

Resolving patch:
diff --git a/synapse/rest/admin/event_reports.py b/synapse/rest/admin/event_reports.py
--- a/synapse/rest/admin/event_reports.py
+++ b/synapse/rest/admin/event_reports.py
@@ -53,11 +53,11 @@ class EventReportsRestServlet(RestServlet):
     PATTERNS = admin_patterns("/event_reports$")
 
     def __init__(self, hs: "HomeServer"):
-        self.auth = hs.get_auth()
-        self.store = hs.get_datastores().main
+        self._auth = hs.get_auth()
+        self._store = hs.get_datastores().main
 
     async def on_GET(self, request: SynapseRequest) -> Tuple[int, JsonDict]:
-        await assert_requester_is_admin(self.auth, request)
+        await assert_requester_is_admin(self._auth, request)
 
         start = parse_integer(request, "from", default=0)
         limit = parse_integer(request, "limit", default=100)
@@ -79,7 +79,7 @@ async def on_GET(self, request: SynapseRequest) -> Tuple[int, JsonDict]:
                 errcode=Codes.INVALID_PARAM,
             )
 
-        event_reports, total = await self.store.get_event_reports_paginate(
+        event_reports, total = await self._store.get_event_reports_paginate(
             start, limit, direction, user_id, room_id
         )
         ret = {"event_reports": event_reports, "total": total}
@@ -108,13 +108,13 @@ class EventReportDetailRestServlet(RestServlet):
     PATTERNS = admin_patterns("/event_reports/(?P<report_id>[^/]*)$")
 
     def __init__(self, hs: "HomeServer"):
-        self.auth = hs.get_auth()
-        self.store = hs.get_datastores().main
+        self._auth = hs.get_auth()
+        self._store = hs.get_datastores().main
 
     async def on_GET(
         self, request: SynapseRequest, report_id: str
     ) -> Tuple[int, JsonDict]:
-        await assert_requester_is_admin(self.auth, request)
+        await assert_requester_is_admin(self._auth, request)
 
         message = (
             "The report_id parameter must be a string representing a positive integer."
@@ -131,8 +131,33 @@ async def on_GET(
                 HTTPStatus.BAD_REQUEST, message, errcode=Codes.INVALID_PARAM
             )
 
-        ret = await self.store.get_event_report(resolved_report_id)
+        ret = await self._store.get_event_report(resolved_report_id)
         if not ret:
             raise NotFoundError("Event report not found")
 
         return HTTPStatus.OK, ret
+
+    async def on_DELETE(
+        self, request: SynapseRequest, report_id: str
+    ) -> Tuple[int, JsonDict]:
+        await assert_requester_is_admin(self._auth, request)
+
+        message = (
+            "The report_id parameter must be a string representing a positive integer."
+        )
+        try:
+            resolved_report_id = int(report_id)
+        except ValueError:
+            raise SynapseError(
+                HTTPStatus.BAD_REQUEST, message, errcode=Codes.INVALID_PARAM
+            )
+
+        if resolved_report_id < 0:
+            raise SynapseError(
+                HTTPStatus.BAD_REQUEST, message, errcode=Codes.INVALID_PARAM
+            )
+
+        if await self._store.delete_event_report(resolved_report_id):
+            return HTTPStatus.OK, {}
+
+        raise NotFoundError("Event report not found")
diff --git a/synapse/storage/databases/main/room.py b/synapse/storage/databases/main/room.py
--- a/synapse/storage/databases/main/room.py
+++ b/synapse/storage/databases/main/room.py
@@ -1417,6 +1417,27 @@ def get_un_partial_stated_rooms_from_stream_txn(
             get_un_partial_stated_rooms_from_stream_txn,
         )
 
+    async def delete_event_report(self, report_id: int) -> bool:
+        """Remove an event report from database.
+
+        Args:
+            report_id: Report to delete
+
+        Returns:
+            Whether the report was successfully deleted or not.
+        """
+        try:
+            await self.db_pool.simple_delete_one(
+                table="event_reports",
+                keyvalues={"id": report_id},
+                desc="delete_event_report",
+            )
+        except StoreError:
+            # Deletion failed because report does not exist
+            return False
+
+        return True
+
 
 class _BackgroundUpdates:
     REMOVE_TOMESTONED_ROOMS_BG_UPDATE = "remove_tombstoned_rooms_from_directory"
@@ -2139,7 +2160,19 @@ async def add_event_report(
         reason: Optional[str],
         content: JsonDict,
         received_ts: int,
-    ) -> None:
+    ) -> int:
+        """Add an event report
+
+        Args:
+            room_id: Room that contains the reported event.
+            event_id: The reported event.
+            user_id: User who reports the event.
+            reason: Description that the user specifies.
+            content: Report request body (score and reason).
+            received_ts: Time when the user submitted the report (milliseconds).
+        Returns:
+            Id of the event report.
+        """
         next_id = self._event_reports_id_gen.get_next()
         await self.db_pool.simple_insert(
             table="event_reports",
@@ -2154,6 +2187,7 @@ async def add_event_report(
             },
             desc="add_event_report",
         )
+        return next_id
 
     async def get_event_report(self, report_id: int) -> Optional[Dict[str, Any]]:
         """Retrieve an event report


Test patch:
diff --git a/tests/rest/admin/test_event_reports.py b/tests/rest/admin/test_event_reports.py
--- a/tests/rest/admin/test_event_reports.py
+++ b/tests/rest/admin/test_event_reports.py
@@ -78,7 +78,7 @@ def test_no_auth(self) -> None:
         """
         Try to get an event report without authentication.
         """
-        channel = self.make_request("GET", self.url, b"{}")
+        channel = self.make_request("GET", self.url, {})
 
         self.assertEqual(401, channel.code, msg=channel.json_body)
         self.assertEqual(Codes.MISSING_TOKEN, channel.json_body["errcode"])
@@ -473,7 +473,7 @@ def test_no_auth(self) -> None:
         """
         Try to get event report without authentication.
         """
-        channel = self.make_request("GET", self.url, b"{}")
+        channel = self.make_request("GET", self.url, {})
 
         self.assertEqual(401, channel.code, msg=channel.json_body)
         self.assertEqual(Codes.MISSING_TOKEN, channel.json_body["errcode"])
@@ -599,3 +599,142 @@ def _check_fields(self, content: JsonDict) -> None:
         self.assertIn("room_id", content["event_json"])
         self.assertIn("sender", content["event_json"])
         self.assertIn("content", content["event_json"])
+
+
+class DeleteEventReportTestCase(unittest.HomeserverTestCase):
+    servlets = [
+        synapse.rest.admin.register_servlets,
+        login.register_servlets,
+    ]
+
+    def prepare(self, reactor: MemoryReactor, clock: Clock, hs: HomeServer) -> None:
+        self._store = hs.get_datastores().main
+
+        self.admin_user = self.register_user("admin", "pass", admin=True)
+        self.admin_user_tok = self.login("admin", "pass")
+
+        self.other_user = self.register_user("user", "pass")
+        self.other_user_tok = self.login("user", "pass")
+
+        # create report
+        event_id = self.get_success(
+            self._store.add_event_report(
+                "room_id",
+                "event_id",
+                self.other_user,
+                "this makes me sad",
+                {},
+                self.clock.time_msec(),
+            )
+        )
+
+        self.url = f"/_synapse/admin/v1/event_reports/{event_id}"
+
+    def test_no_auth(self) -> None:
+        """
+        Try to delete event report without authentication.
+        """
+        channel = self.make_request("DELETE", self.url)
+
+        self.assertEqual(401, channel.code, msg=channel.json_body)
+        self.assertEqual(Codes.MISSING_TOKEN, channel.json_body["errcode"])
+
+    def test_requester_is_no_admin(self) -> None:
+        """
+        If the user is not a server admin, an error 403 is returned.
+        """
+
+        channel = self.make_request(
+            "DELETE",
+            self.url,
+            access_token=self.other_user_tok,
+        )
+
+        self.assertEqual(403, channel.code, msg=channel.json_body)
+        self.assertEqual(Codes.FORBIDDEN, channel.json_body["errcode"])
+
+    def test_delete_success(self) -> None:
+        """
+        Testing delete a report.
+        """
+
+        channel = self.make_request(
+            "DELETE",
+            self.url,
+            access_token=self.admin_user_tok,
+        )
+
+        self.assertEqual(200, channel.code, msg=channel.json_body)
+        self.assertEqual({}, channel.json_body)
+
+        channel = self.make_request(
+            "GET",
+            self.url,
+            access_token=self.admin_user_tok,
+        )
+
+        # check that report was deleted
+        self.assertEqual(404, channel.code, msg=channel.json_body)
+        self.assertEqual(Codes.NOT_FOUND, channel.json_body["errcode"])
+
+    def test_invalid_report_id(self) -> None:
+        """
+        Testing that an invalid `report_id` returns a 400.
+        """
+
+        # `report_id` is negative
+        channel = self.make_request(
+            "DELETE",
+            "/_synapse/admin/v1/event_reports/-123",
+            access_token=self.admin_user_tok,
+        )
+
+        self.assertEqual(400, channel.code, msg=channel.json_body)
+        self.assertEqual(Codes.INVALID_PARAM, channel.json_body["errcode"])
+        self.assertEqual(
+            "The report_id parameter must be a string representing a positive integer.",
+            channel.json_body["error"],
+        )
+
+        # `report_id` is a non-numerical string
+        channel = self.make_request(
+            "DELETE",
+            "/_synapse/admin/v1/event_reports/abcdef",
+            access_token=self.admin_user_tok,
+        )
+
+        self.assertEqual(400, channel.code, msg=channel.json_body)
+        self.assertEqual(Codes.INVALID_PARAM, channel.json_body["errcode"])
+        self.assertEqual(
+            "The report_id parameter must be a string representing a positive integer.",
+            channel.json_body["error"],
+        )
+
+        # `report_id` is undefined
+        channel = self.make_request(
+            "DELETE",
+            "/_synapse/admin/v1/event_reports/",
+            access_token=self.admin_user_tok,
+        )
+
+        self.assertEqual(400, channel.code, msg=channel.json_body)
+        self.assertEqual(Codes.INVALID_PARAM, channel.json_body["errcode"])
+        self.assertEqual(
+            "The report_id parameter must be a string representing a positive integer.",
+            channel.json_body["error"],
+        )
+
+    def test_report_id_not_found(self) -> None:
+        """
+        Testing that a not existing `report_id` returns a 404.
+        """
+
+        channel = self.make_request(
+            "DELETE",
+            "/_synapse/admin/v1/event_reports/123",
+            access_token=self.admin_user_tok,
+        )
+
+        self.assertEqual(404, channel.code, msg=channel.json_body)
+        self.assertEqual(Codes.NOT_FOUND, channel.json_body["errcode"])
+        self.assertEqual("Event report not found", channel.json_body["error"])