catch potential payload forgery (CVE-2024-23832).

federation/tests/utils/test_activitypub.py

@@ -57,7 +57,8 @@ class TestRetrieveAndParseDocument:
     )
     @patch.object(Follow, "post_receive")
     def test_returns_entity_for_valid_document__follow(self, mock_post_receive, mock_fetch, mock_recv):
-        entity = retrieve_and_parse_document("https://example.com/foobar")
+        entity = retrieve_and_parse_document("https://example.com/follow")
+        print(entity)
         assert isinstance(entity, Follow)
 
     @patch("federation.entities.activitypub.models.get_profile_or_entity", return_value=None)
@@ -65,7 +66,7 @@ class TestRetrieveAndParseDocument:
             json.dumps(ACTIVITYPUB_POST_OBJECT), None, None),
     )
     def test_returns_entity_for_valid_document__post__without_activity(self, mock_fetch, mock_recv):
-        entity = retrieve_and_parse_document("https://example.com/foobar")
+        entity = retrieve_and_parse_document("https://diaspodon.fr/users/jaywink/statuses/102356911717767237")
         assert isinstance(entity, Note)
 
     @patch("federation.entities.activitypub.models.extract_receivers", return_value=[])
@@ -73,7 +74,7 @@ class TestRetrieveAndParseDocument:
             json.dumps(ACTIVITYPUB_POST_OBJECT_IMAGES), None, None),
     )
     def test_returns_entity_for_valid_document__post__without_activity__with_images(self, mock_fetch, mock_recv):
-        entity = retrieve_and_parse_document("https://example.com/foobar")
+        entity = retrieve_and_parse_document("https://mastodon.social/users/foobar/statuses/34324r")
         assert isinstance(entity, Note)
         assert len(entity._children) == 1
         assert entity._children[0].url == "https://files.mastodon.social/media_attachments/files/017/792/237/original" \
@@ -86,9 +87,19 @@ class TestRetrieveAndParseDocument:
     )
     def test_returns_entity_for_valid_document__post__wrapped_in_activity(
             self, mock_fetch, mock_recv, mock_sign):
-        entity = retrieve_and_parse_document("https://example.com/foobar")
+        entity = retrieve_and_parse_document("https://diaspodon.fr/users/jaywink/statuses/102356911717767237/activity")
         assert isinstance(entity, Note)
 
+    @patch("federation.entities.activitypub.models.verify_ld_signature", return_value=None)
+    @patch("federation.entities.activitypub.models.get_profile_or_entity", return_value=None)
+    @patch("federation.utils.activitypub.fetch_document", autospec=True, return_value=(
+        json.dumps(ACTIVITYPUB_POST), None, None),
+    )
+    def test_returns_none_for_forged_document(
+            self, mock_fetch, mock_recv, mock_sign):
+        entity = retrieve_and_parse_document("https://example.com/foobar")
+        assert entity is None
+
     @patch("federation.utils.activitypub.fetch_document", autospec=True, return_value=('{"foo": "bar"}', None, None))
     def test_returns_none_for_invalid_document(self, mock_fetch):
         entity = retrieve_and_parse_document("https://example.com/foobar")

federation/utils/activitypub.py

@@ -1,6 +1,7 @@
 import json
 import logging
 from typing import Optional, Any
+from urllib.parse import urlparse
 
 from federation.protocols.activitypub.signing import get_http_authentication
 from federation.utils.network import fetch_document, try_retrieve_webfinger_document
@@ -52,8 +53,14 @@ def retrieve_and_parse_document(fid: str, cache: bool=True) -> Optional[Any]:
             return None
         entities = element_to_objects(document)
         if entities:
-            logger.info("retrieve_and_parse_document - using first entity: %s", entities[0])
-            return entities[0]
+            entity = entities[0]
+            id = entity.id or entity.activity_id
+            # check against potential payload forgery (CVE-2024-23832)
+            if urlparse(id).netloc != urlparse(fid).netloc:
+                logger.warning('retrieve_and_parse_document - payload may be forged, discarding: %s', fid)
+                return None
+            logger.info("retrieve_and_parse_document - using first entity: %s", entity)
+            return entity
 
 
 def retrieve_and_parse_profile(fid: str) -> Optional[Any]: