AP inbox delivery, Protocol.receive: error on blocklisted ids

fixes https://console.cloud.google.com/errors/detail/CN278MyjhZbtOQ;time=P30D?project=bridgy-federated , https://console.cloud.google.com/errors/detail/CLSnttKfy4v90wE;time=P30D?project=bridgy-federated

activitypub.py

@@ -879,6 +879,9 @@ def inbox(protocol=None, id=None):
     actor_id = actor.get('id')
     logger.info(f'Got {type} from {actor_id}: {json_dumps(activity, indent=2)}')
 
+    if ActivityPub.is_blocklisted(actor_id):
+        error(f'Actor {actor_id} is blocklisted')
+
     authed_as = ActivityPub.verify_signature(activity)
 
     # check that this activity is public. only do this for creates, not likes,

follow.py

@@ -134,7 +134,7 @@ class FollowCallback(indieauth.Callback):
         follow_obj = Object(id=follow_id, our_as1=follow_as1, source_protocol='ui',
                             labels=['user'])
 
-        resp = Web.receive(follow_obj, authed_as=domain)
+        resp = Web.receive(follow_obj, authed_as=domain, internal=True)
         logger.info(f'Web.receive returned {resp}')
 
         follow_obj = follow_obj.key.get()
@@ -218,7 +218,7 @@ class UnfollowCallback(indieauth.Callback):
         # network etiquette.)
         follow_obj = Object(id=unfollow_id, users=[user.key], labels=['user'],
                             source_protocol='ui', our_as1=unfollow_as1)
-        resp = Web.receive(follow_obj, authed_as=domain)
+        resp = Web.receive(follow_obj, authed_as=domain, internal=True)
 
         follower.status = 'inactive'
         follower.put()

protocol.py

@@ -546,7 +546,7 @@ class Protocol:
         return outer_obj
 
     @classmethod
-    def receive(from_cls, obj, authed_as=None):
+    def receive(from_cls, obj, authed_as=None, internal=False):
         """Handles an incoming activity.
 
         If ``obj``'s key is unset, ``obj.as1``'s id field is used. If both are
@@ -555,6 +555,7 @@ class Protocol:
         Args:
           obj (models.Object)
           authed_as (str): authenticated actor id who sent this activity
+          internal (bool): whether to allow activity ids on internal domains
 
         Returns:
           (str, int) tuple: (response body, HTTP status code) Flask response
@@ -580,6 +581,8 @@ class Protocol:
 
         if not id:
             error('No id provided')
+        elif from_cls.is_blocklisted(id) and not internal:
+            error(f'Activity {id} is blocklisted')
 
         # short circuit if we've already seen this activity id.
         # (don't do this for bare objects since we need to check further down

tests/test_activitypub.py

@@ -829,6 +829,19 @@ class ActivityPubTest(TestCase):
         self.assertIsNone(Object.get_by_id(not_public['id']))
         self.assertIsNone(Object.get_by_id(not_public['object']['id']))
 
+    def test_inbox_actor_blocklisted(self, mock_head, mock_get, mock_post):
+        got = self.post('/ap/sharedInbox', json={
+            'type': 'Delete',
+            'id': 'http://inst/foo#delete',
+            'actor': 'http://localhost:3000/foo',
+            'object': 'http://inst/foo',
+        })
+        self.assertEqual(400, got.status_code, got.get_data(as_text=True))
+
+        self.assertIsNone(Object.get_by_id('http://localhost:3000/foo'))
+        self.assertIsNone(Object.get_by_id('http://inst/foo#delete'))
+        self.assertIsNone(Object.get_by_id('http://inst/foo'))
+
     def test_inbox_like(self, mock_head, mock_get, mock_post):
         mock_head.return_value = requests_response(url='https://user.com/post')
         mock_get.side_effect = [

tests/test_protocol.py

@@ -1601,6 +1601,16 @@ class ProtocolReceiveTest(TestCase):
                 },
             })
 
+    def test_activity_id_blocklisted(self):
+        with self.assertRaises(BadRequest):
+            Fake.receive_as1({
+                'objectType': 'activity',
+                'verb': 'delete',
+                'id': 'fake:blocklisted:delete',
+                'actor': 'fake:user',
+                'object': 'fake:foo',
+            })
+
     def test_resolve_ids_follow(self):
         follow = {
             'id': 'fake:follow',