Implement knock feature (#6739)

This PR aims to implement the knock feature as proposed in https://github.com/matrix-org/matrix-doc/pull/2403

Signed-off-by: Sorunome mail@sorunome.de
Signed-off-by: Andrew Morgan andrewm@element.io

1 files changed, 302 insertions, 0 deletions

diff --git a/tests/federation/transport/test_knocking.py b/tests/federation/transport/test_knocking.py
new file mode 100644
index 0000000000..121aa88cfa
--- /dev/null
+++ b/tests/federation/transport/test_knocking.py
@@ -0,0 +1,302 @@
+# Copyright 2020 Matrix.org Federation C.I.C
+#
+# Licensed under the Apache License, Version 2.0 (the "License");
+# you may not use this file except in compliance with the License.
+# You may obtain a copy of the License at
+#
+#     http://www.apache.org/licenses/LICENSE-2.0
+#
+# Unless required by applicable law or agreed to in writing, software
+# distributed under the License is distributed on an "AS IS" BASIS,
+# WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+# See the License for the specific language governing permissions and
+# limitations under the License.
+from collections import OrderedDict
+from typing import Dict, List
+
+from synapse.api.constants import EventTypes, JoinRules, Membership
+from synapse.api.room_versions import RoomVersions
+from synapse.events import builder
+from synapse.rest import admin
+from synapse.rest.client.v1 import login, room
+from synapse.server import HomeServer
+from synapse.types import RoomAlias
+
+from tests.test_utils import event_injection
+from tests.unittest import FederatingHomeserverTestCase, TestCase, override_config
+
+# An identifier to use while MSC2304 is not in a stable release of the spec
+KNOCK_UNSTABLE_IDENTIFIER = "xyz.amorgan.knock"
+
+
+class KnockingStrippedStateEventHelperMixin(TestCase):
+    def send_example_state_events_to_room(
+        self,
+        hs: "HomeServer",
+        room_id: str,
+        sender: str,
+    ) -> OrderedDict:
+        """Adds some state to a room. State events are those that should be sent to a knocking
+        user after they knock on the room, as well as some state that *shouldn't* be sent
+        to the knocking user.
+
+        Args:
+            hs: The homeserver of the sender.
+            room_id: The ID of the room to send state into.
+            sender: The ID of the user to send state as. Must be in the room.
+
+        Returns:
+            The OrderedDict of event types and content that a user is expected to see
+            after knocking on a room.
+        """
+        # To set a canonical alias, we'll need to point an alias at the room first.
+        canonical_alias = "#fancy_alias:test"
+        self.get_success(
+            self.store.create_room_alias_association(
+                RoomAlias.from_string(canonical_alias), room_id, ["test"]
+            )
+        )
+
+        # Send some state that we *don't* expect to be given to knocking users
+        self.get_success(
+            event_injection.inject_event(
+                hs,
+                room_version=RoomVersions.MSC2403.identifier,
+                room_id=room_id,
+                sender=sender,
+                type="com.example.secret",
+                state_key="",
+                content={"secret": "password"},
+            )
+        )
+
+        # We use an OrderedDict here to ensure that the knock membership appears last.
+        # Note that order only matters when sending stripped state to clients, not federated
+        # homeservers.
+        room_state = OrderedDict(
+            [
+                # We need to set the room's join rules to allow knocking
+                (
+                    EventTypes.JoinRules,
+                    {"content": {"join_rule": JoinRules.KNOCK}, "state_key": ""},
+                ),
+                # Below are state events that are to be stripped and sent to clients
+                (
+                    EventTypes.Name,
+                    {"content": {"name": "A cool room"}, "state_key": ""},
+                ),
+                (
+                    EventTypes.RoomAvatar,
+                    {
+                        "content": {
+                            "info": {
+                                "h": 398,
+                                "mimetype": "image/jpeg",
+                                "size": 31037,
+                                "w": 394,
+                            },
+                            "url": "mxc://example.org/JWEIFJgwEIhweiWJE",
+                        },
+                        "state_key": "",
+                    },
+                ),
+                (
+                    EventTypes.RoomEncryption,
+                    {"content": {"algorithm": "m.megolm.v1.aes-sha2"}, "state_key": ""},
+                ),
+                (
+                    EventTypes.CanonicalAlias,
+                    {
+                        "content": {"alias": canonical_alias, "alt_aliases": []},
+                        "state_key": "",
+                    },
+                ),
+            ]
+        )
+
+        for event_type, event_dict in room_state.items():
+            event_content = event_dict["content"]
+            state_key = event_dict["state_key"]
+
+            self.get_success(
+                event_injection.inject_event(
+                    hs,
+                    room_version=RoomVersions.MSC2403.identifier,
+                    room_id=room_id,
+                    sender=sender,
+                    type=event_type,
+                    state_key=state_key,
+                    content=event_content,
+                )
+            )
+
+        # Finally, we expect to see the m.room.create event of the room as part of the
+        # stripped state. We don't need to inject this event though.
+        room_state[EventTypes.Create] = {
+            "content": {
+                "creator": sender,
+                "room_version": RoomVersions.MSC2403.identifier,
+            },
+            "state_key": "",
+        }
+
+        return room_state
+
+    def check_knock_room_state_against_room_state(
+        self,
+        knock_room_state: List[Dict],
+        expected_room_state: Dict,
+    ) -> None:
+        """Test a list of stripped room state events received over federation against a
+        dict of expected state events.
+
+        Args:
+            knock_room_state: The list of room state that was received over federation.
+            expected_room_state: A dict containing the room state we expect to see in
+                `knock_room_state`.
+        """
+        for event in knock_room_state:
+            event_type = event["type"]
+
+            # Check that this event type is one of those that we expected.
+            # Note: This will also check that no excess state was included
+            self.assertIn(event_type, expected_room_state)
+
+            # Check the state content matches
+            self.assertEquals(
+                expected_room_state[event_type]["content"], event["content"]
+            )
+
+            # Check the state key is correct
+            self.assertEqual(
+                expected_room_state[event_type]["state_key"], event["state_key"]
+            )
+
+            # Ensure the event has been stripped
+            self.assertNotIn("signatures", event)
+
+            # Pop once we've found and processed a state event
+            expected_room_state.pop(event_type)
+
+        # Check that all expected state events were accounted for
+        self.assertEqual(len(expected_room_state), 0)
+
+
+class FederationKnockingTestCase(
+    FederatingHomeserverTestCase, KnockingStrippedStateEventHelperMixin
+):
+    servlets = [
+        admin.register_servlets,
+        room.register_servlets,
+        login.register_servlets,
+    ]
+
+    def prepare(self, reactor, clock, homeserver):
+        self.store = homeserver.get_datastore()
+
+        # We're not going to be properly signing events as our remote homeserver is fake,
+        # therefore disable event signature checks.
+        # Note that these checks are not relevant to this test case.
+
+        # Have this homeserver auto-approve all event signature checking.
+        async def approve_all_signature_checking(_, pdu):
+            return pdu
+
+        homeserver.get_federation_server()._check_sigs_and_hash = (
+            approve_all_signature_checking
+        )
+
+        # Have this homeserver skip event auth checks. This is necessary due to
+        # event auth checks ensuring that events were signed by the sender's homeserver.
+        async def _check_event_auth(
+            origin, event, context, state, auth_events, backfilled
+        ):
+            return context
+
+        homeserver.get_federation_handler()._check_event_auth = _check_event_auth
+
+        return super().prepare(reactor, clock, homeserver)
+
+    @override_config({"experimental_features": {"msc2403_enabled": True}})
+    def test_room_state_returned_when_knocking(self):
+        """
+        Tests that specific, stripped state events from a room are returned after
+        a remote homeserver successfully knocks on a local room.
+        """
+        user_id = self.register_user("u1", "you the one")
+        user_token = self.login("u1", "you the one")
+
+        fake_knocking_user_id = "@user:other.example.com"
+
+        # Create a room with a room version that includes knocking
+        room_id = self.helper.create_room_as(
+            "u1",
+            is_public=False,
+            room_version=RoomVersions.MSC2403.identifier,
+            tok=user_token,
+        )
+
+        # Update the join rules and add additional state to the room to check for later
+        expected_room_state = self.send_example_state_events_to_room(
+            self.hs, room_id, user_id
+        )
+
+        channel = self.make_request(
+            "GET",
+            "/_matrix/federation/unstable/%s/make_knock/%s/%s?ver=%s"
+            % (
+                KNOCK_UNSTABLE_IDENTIFIER,
+                room_id,
+                fake_knocking_user_id,
+                # Inform the remote that we support the room version of the room we're
+                # knocking on
+                RoomVersions.MSC2403.identifier,
+            ),
+        )
+        self.assertEquals(200, channel.code, channel.result)
+
+        # Note: We don't expect the knock membership event to be sent over federation as
+        # part of the stripped room state, as the knocking homeserver already has that
+        # event. It is only done for clients during /sync
+
+        # Extract the generated knock event json
+        knock_event = channel.json_body["event"]
+
+        # Check that the event has things we expect in it
+        self.assertEquals(knock_event["room_id"], room_id)
+        self.assertEquals(knock_event["sender"], fake_knocking_user_id)
+        self.assertEquals(knock_event["state_key"], fake_knocking_user_id)
+        self.assertEquals(knock_event["type"], EventTypes.Member)
+        self.assertEquals(knock_event["content"]["membership"], Membership.KNOCK)
+
+        # Turn the event json dict into a proper event.
+        # We won't sign it properly, but that's OK as we stub out event auth in `prepare`
+        signed_knock_event = builder.create_local_event_from_event_dict(
+            self.clock,
+            self.hs.hostname,
+            self.hs.signing_key,
+            room_version=RoomVersions.MSC2403,
+            event_dict=knock_event,
+        )
+
+        # Convert our proper event back to json dict format
+        signed_knock_event_json = signed_knock_event.get_pdu_json(
+            self.clock.time_msec()
+        )
+
+        # Send the signed knock event into the room
+        channel = self.make_request(
+            "PUT",
+            "/_matrix/federation/unstable/%s/send_knock/%s/%s"
+            % (KNOCK_UNSTABLE_IDENTIFIER, room_id, signed_knock_event.event_id),
+            signed_knock_event_json,
+        )
+        self.assertEquals(200, channel.code, channel.result)
+
+        # Check that we got the stripped room state in return
+        room_state_events = channel.json_body["knock_state_events"]
+
+        # Validate the stripped room state events
+        self.check_knock_room_state_against_room_state(
+            room_state_events, expected_room_state
+        )