Implement GET /_matrix/client/r0/rooms/{roomId}/aliases (#6939)

per matrix-org/matrix-doc#2432

2 files changed, 39 insertions, 1 deletions

diff --git a/synapse/handlers/directory.py b/synapse/handlers/directory.py
index f718388884..3f8c792149 100644
--- a/synapse/handlers/directory.py
+++ b/synapse/handlers/directory.py
@@ -16,6 +16,7 @@
 
 import logging
 import string
+from typing import List
 
 from twisted.internet import defer
 
@@ -28,7 +29,7 @@ from synapse.api.errors import (
     StoreError,
     SynapseError,
 )
-from synapse.types import RoomAlias, UserID, get_domain_from_id
+from synapse.types import Requester, RoomAlias, UserID, get_domain_from_id
 
 from ._base import BaseHandler
 
@@ -452,3 +453,17 @@ class DirectoryHandler(BaseHandler):
         yield self.store.set_room_is_public_appservice(
             room_id, appservice_id, network_id, visibility == "public"
         )
+
+    async def get_aliases_for_room(
+        self, requester: Requester, room_id: str
+    ) -> List[str]:
+        """
+        Get a list of the aliases that currently point to this room on this server
+        """
+        # allow access to server admins and current members of the room
+        is_admin = await self.auth.is_server_admin(requester.user)
+        if not is_admin:
+            await self.auth.check_joined_room(room_id, requester.user.to_string())
+
+        aliases = await self.store.get_aliases_for_room(room_id)
+        return aliases
diff --git a/synapse/rest/client/v1/room.py b/synapse/rest/client/v1/room.py
index 6f31584c51..143dc738c6 100644
--- a/synapse/rest/client/v1/room.py
+++ b/synapse/rest/client/v1/room.py
@@ -45,6 +45,10 @@ from synapse.storage.state import StateFilter
 from synapse.streams.config import PaginationConfig
 from synapse.types import RoomAlias, RoomID, StreamToken, ThirdPartyInstanceID, UserID
 
+MYPY = False
+if MYPY:
+    import synapse.server
+
 logger = logging.getLogger(__name__)
 
 
@@ -843,6 +847,24 @@ class RoomTypingRestServlet(RestServlet):
         return 200, {}
 
 
+class RoomAliasListServlet(RestServlet):
+    PATTERNS = client_patterns("/rooms/(?P<room_id>[^/]*)/aliases", unstable=False)
+
+    def __init__(self, hs: "synapse.server.HomeServer"):
+        super().__init__()
+        self.auth = hs.get_auth()
+        self.directory_handler = hs.get_handlers().directory_handler
+
+    async def on_GET(self, request, room_id):
+        requester = await self.auth.get_user_by_req(request)
+
+        alias_list = await self.directory_handler.get_aliases_for_room(
+            requester, room_id
+        )
+
+        return 200, {"aliases": alias_list}
+
+
 class SearchRestServlet(RestServlet):
     PATTERNS = client_patterns("/search$", v1=True)
 
@@ -931,6 +953,7 @@ def register_servlets(hs, http_server):
     JoinedRoomsRestServlet(hs).register(http_server)
     RoomEventServlet(hs).register(http_server)
     RoomEventContextServlet(hs).register(http_server)
+    RoomAliasListServlet(hs).register(http_server)
 
 
 def register_deprecated_servlets(hs, http_server):