Correctly ratelimit invites when creating a room (#9968)

* Correctly ratelimit invites when creating a room

Also allow ratelimiting for more than one action at a time.

2 files changed, 94 insertions, 0 deletions

diff --git a/tests/api/test_ratelimiting.py b/tests/api/test_ratelimiting.py
index fa96ba07a5..dcf0110c16 100644
--- a/tests/api/test_ratelimiting.py
+++ b/tests/api/test_ratelimiting.py
@@ -230,3 +230,60 @@ class TestRatelimiter(unittest.HomeserverTestCase):
         # Shouldn't raise
         for _ in range(20):
             self.get_success_or_raise(limiter.ratelimit(requester, _time_now_s=0))
+
+    def test_multiple_actions(self):
+        limiter = Ratelimiter(
+            store=self.hs.get_datastore(), clock=None, rate_hz=0.1, burst_count=3
+        )
+        # Test that 4 actions aren't allowed with a maximum burst of 3.
+        allowed, time_allowed = self.get_success_or_raise(
+            limiter.can_do_action(None, key="test_id", n_actions=4, _time_now_s=0)
+        )
+        self.assertFalse(allowed)
+
+        # Test that 3 actions are allowed with a maximum burst of 3.
+        allowed, time_allowed = self.get_success_or_raise(
+            limiter.can_do_action(None, key="test_id", n_actions=3, _time_now_s=0)
+        )
+        self.assertTrue(allowed)
+        self.assertEquals(10.0, time_allowed)
+
+        # Test that, after doing these 3 actions, we can't do any more action without
+        # waiting.
+        allowed, time_allowed = self.get_success_or_raise(
+            limiter.can_do_action(None, key="test_id", n_actions=1, _time_now_s=0)
+        )
+        self.assertFalse(allowed)
+        self.assertEquals(10.0, time_allowed)
+
+        # Test that after waiting we can do only 1 action.
+        allowed, time_allowed = self.get_success_or_raise(
+            limiter.can_do_action(
+                None,
+                key="test_id",
+                update=False,
+                n_actions=1,
+                _time_now_s=10,
+            )
+        )
+        self.assertTrue(allowed)
+        # The time allowed is the current time because we could still repeat the action
+        # once.
+        self.assertEquals(10.0, time_allowed)
+
+        allowed, time_allowed = self.get_success_or_raise(
+            limiter.can_do_action(None, key="test_id", n_actions=2, _time_now_s=10)
+        )
+        self.assertFalse(allowed)
+        # The time allowed doesn't change despite allowed being False because, while we
+        # don't allow 2 actions, we could still do 1.
+        self.assertEquals(10.0, time_allowed)
+
+        # Test that after waiting a bit more we can do 2 actions.
+        allowed, time_allowed = self.get_success_or_raise(
+            limiter.can_do_action(None, key="test_id", n_actions=2, _time_now_s=20)
+        )
+        self.assertTrue(allowed)
+        # The time allowed is the current time because we could still repeat the action
+        # once.
+        self.assertEquals(20.0, time_allowed)
diff --git a/tests/rest/client/v1/test_rooms.py b/tests/rest/client/v1/test_rooms.py
index a3694f3d02..7c4bdcdfdd 100644
--- a/tests/rest/client/v1/test_rooms.py
+++ b/tests/rest/client/v1/test_rooms.py
@@ -463,6 +463,43 @@ class RoomsCreateTestCase(RoomBase):
         )
         self.assertEquals(400, channel.code)
 
+    @unittest.override_config({"rc_invites": {"per_room": {"burst_count": 3}}})
+    def test_post_room_invitees_ratelimit(self):
+        """Test that invites sent when creating a room are ratelimited by a RateLimiter,
+        which ratelimits them correctly, including by not limiting when the requester is
+        exempt from ratelimiting.
+        """
+
+        # Build the request's content. We use local MXIDs because invites over federation
+        # are more difficult to mock.
+        content = json.dumps(
+            {
+                "invite": [
+                    "@alice1:red",
+                    "@alice2:red",
+                    "@alice3:red",
+                    "@alice4:red",
+                ]
+            }
+        ).encode("utf8")
+
+        # Test that the invites are correctly ratelimited.
+        channel = self.make_request("POST", "/createRoom", content)
+        self.assertEqual(400, channel.code)
+        self.assertEqual(
+            "Cannot invite so many users at once",
+            channel.json_body["error"],
+        )
+
+        # Add the current user to the ratelimit overrides, allowing them no ratelimiting.
+        self.get_success(
+            self.hs.get_datastore().set_ratelimit_for_user(self.user_id, 0, 0)
+        )
+
+        # Test that the invites aren't ratelimited anymore.
+        channel = self.make_request("POST", "/createRoom", content)
+        self.assertEqual(200, channel.code)
+
 
 class RoomTopicTestCase(RoomBase):
     """ Tests /rooms/$room_id/topic REST events. """