Stop shadow-banned users from sending non-member events. (#8142)

3 files changed, 66 insertions, 40 deletions

diff --git a/synapse/rest/client/v1/room.py b/synapse/rest/client/v1/room.py
index a9dd3a6aec..11da8bc037 100644
--- a/synapse/rest/client/v1/room.py
+++ b/synapse/rest/client/v1/room.py
@@ -201,8 +201,8 @@ class RoomStateEventRestServlet(TransactionRestServlet):
         if state_key is not None:
             event_dict["state_key"] = state_key
 
-        if event_type == EventTypes.Member:
-            try:
+        try:
+            if event_type == EventTypes.Member:
                 membership = content.get("membership", None)
                 event_id, _ = await self.room_member_handler.update_membership(
                     requester,
@@ -211,16 +211,16 @@ class RoomStateEventRestServlet(TransactionRestServlet):
                     action=membership,
                     content=content,
                 )
-            except ShadowBanError:
-                event_id = "$" + random_string(43)
-        else:
-            (
-                event,
-                _,
-            ) = await self.event_creation_handler.create_and_send_nonmember_event(
-                requester, event_dict, txn_id=txn_id
-            )
-            event_id = event.event_id
+            else:
+                (
+                    event,
+                    _,
+                ) = await self.event_creation_handler.create_and_send_nonmember_event(
+                    requester, event_dict, txn_id=txn_id
+                )
+                event_id = event.event_id
+        except ShadowBanError:
+            event_id = "$" + random_string(43)
 
         set_tag("event_id", event_id)
         ret = {"event_id": event_id}
@@ -253,12 +253,19 @@ class RoomSendEventRestServlet(TransactionRestServlet):
         if b"ts" in request.args and requester.app_service:
             event_dict["origin_server_ts"] = parse_integer(request, "ts", 0)
 
-        event, _ = await self.event_creation_handler.create_and_send_nonmember_event(
-            requester, event_dict, txn_id=txn_id
-        )
+        try:
+            (
+                event,
+                _,
+            ) = await self.event_creation_handler.create_and_send_nonmember_event(
+                requester, event_dict, txn_id=txn_id
+            )
+            event_id = event.event_id
+        except ShadowBanError:
+            event_id = "$" + random_string(43)
 
-        set_tag("event_id", event.event_id)
-        return 200, {"event_id": event.event_id}
+        set_tag("event_id", event_id)
+        return 200, {"event_id": event_id}
 
     def on_GET(self, request, room_id, event_type, txn_id):
         return 200, "Not implemented"
@@ -799,20 +806,27 @@ class RoomRedactEventRestServlet(TransactionRestServlet):
         requester = await self.auth.get_user_by_req(request)
         content = parse_json_object_from_request(request)
 
-        event, _ = await self.event_creation_handler.create_and_send_nonmember_event(
-            requester,
-            {
-                "type": EventTypes.Redaction,
-                "content": content,
-                "room_id": room_id,
-                "sender": requester.user.to_string(),
-                "redacts": event_id,
-            },
-            txn_id=txn_id,
-        )
+        try:
+            (
+                event,
+                _,
+            ) = await self.event_creation_handler.create_and_send_nonmember_event(
+                requester,
+                {
+                    "type": EventTypes.Redaction,
+                    "content": content,
+                    "room_id": room_id,
+                    "sender": requester.user.to_string(),
+                    "redacts": event_id,
+                },
+                txn_id=txn_id,
+            )
+            event_id = event.event_id
+        except ShadowBanError:
+            event_id = "$" + random_string(43)
 
-        set_tag("event_id", event.event_id)
-        return 200, {"event_id": event.event_id}
+        set_tag("event_id", event_id)
+        return 200, {"event_id": event_id}
 
     def on_PUT(self, request, room_id, event_id, txn_id):
         set_tag("txn_id", txn_id)
diff --git a/synapse/rest/client/v2_alpha/relations.py b/synapse/rest/client/v2_alpha/relations.py
index 89002ffbff..e29f49f7f5 100644
--- a/synapse/rest/client/v2_alpha/relations.py
+++ b/synapse/rest/client/v2_alpha/relations.py
@@ -22,7 +22,7 @@ any time to reflect changes in the MSC.
 import logging
 
 from synapse.api.constants import EventTypes, RelationTypes
-from synapse.api.errors import SynapseError
+from synapse.api.errors import ShadowBanError, SynapseError
 from synapse.http.servlet import (
     RestServlet,
     parse_integer,
@@ -35,6 +35,7 @@ from synapse.storage.relations import (
     PaginationChunk,
     RelationPaginationToken,
 )
+from synapse.util.stringutils import random_string
 
 from ._base import client_patterns
 
@@ -111,11 +112,18 @@ class RelationSendServlet(RestServlet):
             "sender": requester.user.to_string(),
         }
 
-        event, _ = await self.event_creation_handler.create_and_send_nonmember_event(
-            requester, event_dict=event_dict, txn_id=txn_id
-        )
+        try:
+            (
+                event,
+                _,
+            ) = await self.event_creation_handler.create_and_send_nonmember_event(
+                requester, event_dict=event_dict, txn_id=txn_id
+            )
+            event_id = event.event_id
+        except ShadowBanError:
+            event_id = "$" + random_string(43)
 
-        return 200, {"event_id": event.event_id}
+        return 200, {"event_id": event_id}
 
 
 class RelationPaginationServlet(RestServlet):
diff --git a/synapse/rest/client/v2_alpha/room_upgrade_rest_servlet.py b/synapse/rest/client/v2_alpha/room_upgrade_rest_servlet.py
index f357015a70..39a5518614 100644
--- a/synapse/rest/client/v2_alpha/room_upgrade_rest_servlet.py
+++ b/synapse/rest/client/v2_alpha/room_upgrade_rest_servlet.py
@@ -15,13 +15,14 @@
 
 import logging
 
-from synapse.api.errors import Codes, SynapseError
+from synapse.api.errors import Codes, ShadowBanError, SynapseError
 from synapse.api.room_versions import KNOWN_ROOM_VERSIONS
 from synapse.http.servlet import (
     RestServlet,
     assert_params_in_dict,
     parse_json_object_from_request,
 )
+from synapse.util import stringutils
 
 from ._base import client_patterns
 
@@ -62,7 +63,6 @@ class RoomUpgradeRestServlet(RestServlet):
 
         content = parse_json_object_from_request(request)
         assert_params_in_dict(content, ("new_version",))
-        new_version = content["new_version"]
 
         new_version = KNOWN_ROOM_VERSIONS.get(content["new_version"])
         if new_version is None:
@@ -72,9 +72,13 @@ class RoomUpgradeRestServlet(RestServlet):
                 Codes.UNSUPPORTED_ROOM_VERSION,
             )
 
-        new_room_id = await self._room_creation_handler.upgrade_room(
-            requester, room_id, new_version
-        )
+        try:
+            new_room_id = await self._room_creation_handler.upgrade_room(
+                requester, room_id, new_version
+            )
+        except ShadowBanError:
+            # Generate a random room ID.
+            new_room_id = stringutils.random_string(18)
 
         ret = {"replacement_room": new_room_id}