Ignore received EDUs if origin server in room ACL

changelog.d/18475.feature

@@ -0,0 +1 @@
+Make ACLs apply to EDUs per [MSC4163](https://github.com/matrix-org/matrix-spec-proposals/pull/4163).

synapse/federation/federation_server.py

@@ -551,6 +551,53 @@ async def _process_edu(edu_dict: JsonDict) -> None:
                 edu_type=edu_dict["edu_type"],
                 content=edu_dict["content"],
             )
+
+            # Server ACL's apply to `EduTypes.TYPING` per MSC4163:
+            #
+            # > For typing notifications (m.typing), the room_id field inside
+            # > content should be checked, with the typing notification ignored if
+            # > the origin of the request is a server which is forbidden by the
+            # > room's ACL. Ignoring the typing notification means that the EDU
+            # > MUST be dropped upon receipt.
+            if edu.edu_type == EduTypes.TYPING:
+                origin_host, _ = parse_server_name(origin)
+                room_id = edu.content["room_id"]
+                try:
+                    await self.check_server_matches_acl(origin_host, room_id)
+                except AuthError:
+                    logger.warning(
+                        "Ignoring typing EDU for room %s from banned server", room_id
+                    )
+                    return
+
+            # Server ACL's apply to `EduTypes.RECEIPT` per MSC4163:
+            #
+            # > For read receipts (m.receipt), all receipts inside a room_id
+            # > inside content should be ignored if the origin of the request is
+            # > forbidden by the room's ACL.
+            if edu.edu_type == EduTypes.RECEIPT:
+                origin_host, _ = parse_server_name(origin)
+                to_remove = set()
+                for room_id in edu.content.keys():
+                    try:
+                        await self.check_server_matches_acl(origin_host, room_id)
+                    except AuthError:
+                        to_remove.add(room_id)
+
+                if to_remove:
+                    logger.warning(
+                        "Ignoring receipts in EDU for rooms %s from banned server %s",
+                        to_remove,
+                        origin_host,
+                    )
+
+                    for room_id in to_remove:
+                        edu.content.pop(room_id)
+
+                    if not edu.content:
+                        # If we've removed all the rooms, we can just ignore the whole EDU
+                        return
+
             try:
                 await self.registry.on_edu(edu.edu_type, origin, edu.content)
             except Exception: