Add /user/{user_id}/shared_rooms/ api (#7785)

* Add shared_rooms api

* Add changelog

* Add .

* Wrap response in {"rooms": }

* linting

* Add unstable_features key

* Remove options from isort that aren't part of 5.x

`-y` and `-rc` are now default behaviour and no longer exist.

`dont-skip` is no longer required

https://timothycrosley.github.io/isort/CHANGELOG/#500-penny-july-4-2020

* Update imports to make isort happy

* Add changelog

* Update tox.ini file with correct invocation

* fix linting again for isort

* Vendor prefix unstable API

* Fix to match spec

* import Codes

* import Codes

* Use FORBIDDEN

* Update changelog.d/7785.feature

Co-authored-by: Andrew Morgan <1342360+anoadragon453@users.noreply.github.com>

* Implement get_shared_rooms_for_users

* a comma

* trailing whitespace

* Handle the easy feedback

* Switch to using runInteraction

* Add tests

* Feedback

* Seperate unstable endpoint from v2

* Add upgrade node

* a line

* Fix style by adding a blank line at EOF.

* Update synapse/storage/databases/main/user_directory.py

Co-authored-by: Tulir Asokan <tulir@maunium.net>

* Update synapse/storage/databases/main/user_directory.py

Co-authored-by: Andrew Morgan <1342360+anoadragon453@users.noreply.github.com>

* Update UPGRADE.rst

Co-authored-by: Andrew Morgan <1342360+anoadragon453@users.noreply.github.com>

* Fix UPGRADE/CHANGELOG unstable paths

unstable unstable unstable

Co-authored-by: Andrew Morgan <1342360+anoadragon453@users.noreply.github.com>
Co-authored-by: Tulir Asokan <tulir@maunium.net>

Co-authored-by: Andrew Morgan <1342360+anoadragon453@users.noreply.github.com>
Co-authored-by: Patrick Cloke <clokep@users.noreply.github.com>
Co-authored-by: Tulir Asokan <tulir@maunium.net>

8 files changed, 270 insertions, 1 deletions

diff --git a/UPGRADE.rst b/UPGRADE.rst
index 6492fa011f..77be1b2952 100644
--- a/UPGRADE.rst
+++ b/UPGRADE.rst
@@ -1,3 +1,16 @@
+Upgrading to v1.20.0
+====================
+
+Shared rooms endpoint (MSC2666)
+-------------------------------
+
+This release contains a new unstable endpoint `/_matrix/client/unstable/uk.half-shot.msc2666/user/shared_rooms/.*`
+for fetching rooms one user has in common with another. This feature requires the
+`update_user_directory` config flag to be `True`. If you are you are using a `synapse.app.user_dir`
+worker, requests to this endpoint must be handled by that worker. 
+See `docs/workers.md <docs/workers.md>`_ for more details.
+
+
 Upgrading Synapse
 =================
 
diff --git a/changelog.d/7785.feature b/changelog.d/7785.feature
new file mode 100644
index 0000000000..c7e51c9320
--- /dev/null
+++ b/changelog.d/7785.feature
@@ -0,0 +1 @@
+Add an endpoint to query your shared rooms with another user as an implementation of [MSC2666](https://github.com/matrix-org/matrix-doc/pull/2666).
diff --git a/docs/workers.md b/docs/workers.md
index bfec745897..7a8f5c89fc 100644
--- a/docs/workers.md
+++ b/docs/workers.md
@@ -380,6 +380,7 @@ Handles searches in the user directory. It can handle REST endpoints matching
 the following regular expressions:
 
     ^/_matrix/client/(api/v1|r0|unstable)/user_directory/search$
+    ^/_matrix/client/unstable/uk.half-shot.msc2666/user/shared_rooms/.*$
 
 When using this worker you must also set `update_user_directory: False` in the
 shared configuration file to stop the main synapse running background
diff --git a/synapse/rest/__init__.py b/synapse/rest/__init__.py
index 46e458e95b..87f927890c 100644
--- a/synapse/rest/__init__.py
+++ b/synapse/rest/__init__.py
@@ -50,6 +50,7 @@ from synapse.rest.client.v2_alpha import (
     room_keys,
     room_upgrade_rest_servlet,
     sendtodevice,
+    shared_rooms,
     sync,
     tags,
     thirdparty,
@@ -125,3 +126,6 @@ class ClientRestResource(JsonResource):
         synapse.rest.admin.register_servlets_for_client_rest_resource(
             hs, client_resource
         )
+
+        # unstable
+        shared_rooms.register_servlets(hs, client_resource)
diff --git a/synapse/rest/client/v2_alpha/shared_rooms.py b/synapse/rest/client/v2_alpha/shared_rooms.py
new file mode 100644
index 0000000000..2492634dac
--- /dev/null
+++ b/synapse/rest/client/v2_alpha/shared_rooms.py
@@ -0,0 +1,68 @@
+# -*- coding: utf-8 -*-
+# Copyright 2020 Half-Shot
+#
+# 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.
+import logging
+
+from synapse.api.errors import Codes, SynapseError
+from synapse.http.servlet import RestServlet
+from synapse.types import UserID
+
+from ._base import client_patterns
+
+logger = logging.getLogger(__name__)
+
+
+class UserSharedRoomsServlet(RestServlet):
+    """
+    GET /uk.half-shot.msc2666/user/shared_rooms/{user_id} HTTP/1.1
+    """
+
+    PATTERNS = client_patterns(
+        "/uk.half-shot.msc2666/user/shared_rooms/(?P<user_id>[^/]*)",
+        releases=(),  # This is an unstable feature
+    )
+
+    def __init__(self, hs):
+        super(UserSharedRoomsServlet, self).__init__()
+        self.auth = hs.get_auth()
+        self.store = hs.get_datastore()
+        self.user_directory_active = hs.config.update_user_directory
+
+    async def on_GET(self, request, user_id):
+
+        if not self.user_directory_active:
+            raise SynapseError(
+                code=400,
+                msg="The user directory is disabled on this server. Cannot determine shared rooms.",
+                errcode=Codes.FORBIDDEN,
+            )
+
+        UserID.from_string(user_id)
+
+        requester = await self.auth.get_user_by_req(request)
+        if user_id == requester.user.to_string():
+            raise SynapseError(
+                code=400,
+                msg="You cannot request a list of shared rooms with yourself",
+                errcode=Codes.FORBIDDEN,
+            )
+        rooms = await self.store.get_shared_rooms_for_users(
+            requester.user.to_string(), user_id
+        )
+
+        return 200, {"joined": list(rooms)}
+
+
+def register_servlets(hs, http_server):
+    UserSharedRoomsServlet(hs).register(http_server)
diff --git a/synapse/rest/client/versions.py b/synapse/rest/client/versions.py
index 0d668df0b6..24ac57f35d 100644
--- a/synapse/rest/client/versions.py
+++ b/synapse/rest/client/versions.py
@@ -60,6 +60,8 @@ class VersionsRestServlet(RestServlet):
                     "org.matrix.e2e_cross_signing": True,
                     # Implements additional endpoints as described in MSC2432
                     "org.matrix.msc2432": True,
+                    # Implements additional endpoints as described in MSC2666
+                    "uk.half-shot.msc2666": True,
                 },
             },
         )
diff --git a/synapse/storage/databases/main/user_directory.py b/synapse/storage/databases/main/user_directory.py
index c977db042e..f2f9a5799a 100644
--- a/synapse/storage/databases/main/user_directory.py
+++ b/synapse/storage/databases/main/user_directory.py
@@ -15,7 +15,7 @@
 
 import logging
 import re
-from typing import Any, Dict, Iterable, Optional, Tuple
+from typing import Any, Dict, Iterable, Optional, Set, Tuple
 
 from synapse.api.constants import EventTypes, JoinRules
 from synapse.storage.database import DatabasePool
@@ -675,6 +675,48 @@ class UserDirectoryStore(UserDirectoryBackgroundUpdateStore):
         users.update(rows)
         return list(users)
 
+    @cached()
+    async def get_shared_rooms_for_users(
+        self, user_id: str, other_user_id: str
+    ) -> Set[str]:
+        """
+        Returns the rooms that a local user shares with another local or remote user.
+
+        Args:
+            user_id: The MXID of a local user
+            other_user_id: The MXID of the other user
+
+        Returns:
+            A set of room ID's that the users share.
+        """
+
+        def _get_shared_rooms_for_users_txn(txn):
+            txn.execute(
+                """
+                SELECT p1.room_id
+                FROM users_in_public_rooms as p1
+                INNER JOIN users_in_public_rooms as p2
+                    ON p1.room_id = p2.room_id
+                    AND p1.user_id = ?
+                    AND p2.user_id = ?
+                UNION
+                SELECT room_id
+                FROM users_who_share_private_rooms
+                WHERE
+                    user_id = ?
+                    AND other_user_id = ?
+                """,
+                (user_id, other_user_id, user_id, other_user_id),
+            )
+            rows = self.db_pool.cursor_to_dict(txn)
+            return rows
+
+        rows = await self.db_pool.runInteraction(
+            "get_shared_rooms_for_users", _get_shared_rooms_for_users_txn
+        )
+
+        return {row["room_id"] for row in rows}
+
     async def get_user_directory_stream_pos(self) -> int:
         return await self.db_pool.simple_select_one_onecol(
             table="user_directory_stream_pos",
diff --git a/tests/rest/client/v2_alpha/test_shared_rooms.py b/tests/rest/client/v2_alpha/test_shared_rooms.py
new file mode 100644
index 0000000000..5ae72fd008
--- /dev/null
+++ b/tests/rest/client/v2_alpha/test_shared_rooms.py
@@ -0,0 +1,138 @@
+# -*- coding: utf-8 -*-
+# Copyright 2020 Half-Shot
+#
+# 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.
+import synapse.rest.admin
+from synapse.rest.client.v1 import login, room
+from synapse.rest.client.v2_alpha import shared_rooms
+
+from tests import unittest
+
+
+class UserSharedRoomsTest(unittest.HomeserverTestCase):
+    """
+    Tests the UserSharedRoomsServlet.
+    """
+
+    servlets = [
+        login.register_servlets,
+        synapse.rest.admin.register_servlets_for_client_rest_resource,
+        room.register_servlets,
+        shared_rooms.register_servlets,
+    ]
+
+    def make_homeserver(self, reactor, clock):
+        config = self.default_config()
+        config["update_user_directory"] = True
+        return self.setup_test_homeserver(config=config)
+
+    def prepare(self, reactor, clock, hs):
+        self.store = hs.get_datastore()
+        self.handler = hs.get_user_directory_handler()
+
+    def _get_shared_rooms(self, token, other_user):
+        request, channel = self.make_request(
+            "GET",
+            "/_matrix/client/unstable/uk.half-shot.msc2666/user/shared_rooms/%s"
+            % other_user,
+            access_token=token,
+        )
+        self.render(request)
+        return request, channel
+
+    def test_shared_room_list_public(self):
+        """
+        A room should show up in the shared list of rooms between two users
+        if it is public.
+        """
+        u1 = self.register_user("user1", "pass")
+        u1_token = self.login(u1, "pass")
+        u2 = self.register_user("user2", "pass")
+        u2_token = self.login(u2, "pass")
+
+        room = self.helper.create_room_as(u1, is_public=True, tok=u1_token)
+        self.helper.invite(room, src=u1, targ=u2, tok=u1_token)
+        self.helper.join(room, user=u2, tok=u2_token)
+
+        request, channel = self._get_shared_rooms(u1_token, u2)
+        self.assertEquals(200, channel.code, channel.result)
+        self.assertEquals(len(channel.json_body["joined"]), 1)
+        self.assertEquals(channel.json_body["joined"][0], room)
+
+    def test_shared_room_list_private(self):
+        """
+        A room should show up in the shared list of rooms between two users
+        if it is private.
+        """
+        u1 = self.register_user("user1", "pass")
+        u1_token = self.login(u1, "pass")
+        u2 = self.register_user("user2", "pass")
+        u2_token = self.login(u2, "pass")
+
+        room = self.helper.create_room_as(u1, is_public=False, tok=u1_token)
+        self.helper.invite(room, src=u1, targ=u2, tok=u1_token)
+        self.helper.join(room, user=u2, tok=u2_token)
+
+        request, channel = self._get_shared_rooms(u1_token, u2)
+        self.assertEquals(200, channel.code, channel.result)
+        self.assertEquals(len(channel.json_body["joined"]), 1)
+        self.assertEquals(channel.json_body["joined"][0], room)
+
+    def test_shared_room_list_mixed(self):
+        """
+        The shared room list between two users should contain both public and private
+        rooms.
+        """
+        u1 = self.register_user("user1", "pass")
+        u1_token = self.login(u1, "pass")
+        u2 = self.register_user("user2", "pass")
+        u2_token = self.login(u2, "pass")
+
+        room_public = self.helper.create_room_as(u1, is_public=True, tok=u1_token)
+        room_private = self.helper.create_room_as(u2, is_public=False, tok=u2_token)
+        self.helper.invite(room_public, src=u1, targ=u2, tok=u1_token)
+        self.helper.invite(room_private, src=u2, targ=u1, tok=u2_token)
+        self.helper.join(room_public, user=u2, tok=u2_token)
+        self.helper.join(room_private, user=u1, tok=u1_token)
+
+        request, channel = self._get_shared_rooms(u1_token, u2)
+        self.assertEquals(200, channel.code, channel.result)
+        self.assertEquals(len(channel.json_body["joined"]), 2)
+        self.assertTrue(room_public in channel.json_body["joined"])
+        self.assertTrue(room_private in channel.json_body["joined"])
+
+    def test_shared_room_list_after_leave(self):
+        """
+        A room should no longer be considered shared if the other
+        user has left it.
+        """
+        u1 = self.register_user("user1", "pass")
+        u1_token = self.login(u1, "pass")
+        u2 = self.register_user("user2", "pass")
+        u2_token = self.login(u2, "pass")
+
+        room = self.helper.create_room_as(u1, is_public=True, tok=u1_token)
+        self.helper.invite(room, src=u1, targ=u2, tok=u1_token)
+        self.helper.join(room, user=u2, tok=u2_token)
+
+        # Assert user directory is not empty
+        request, channel = self._get_shared_rooms(u1_token, u2)
+        self.assertEquals(200, channel.code, channel.result)
+        self.assertEquals(len(channel.json_body["joined"]), 1)
+        self.assertEquals(channel.json_body["joined"][0], room)
+
+        self.helper.leave(room, user=u1, tok=u1_token)
+
+        request, channel = self._get_shared_rooms(u2_token, u1)
+        self.assertEquals(200, channel.code, channel.result)
+        self.assertEquals(len(channel.json_body["joined"]), 0)