From 9c8e605bd79f26a8b551608b86bb975a6cca2382 Mon Sep 17 00:00:00 2001
From: Quentin Gliech <quenting@element.io>
Date: Fri, 17 Jun 2022 11:18:27 +0200
Subject: [PATCH] Simplify the alias deletion logic as an application service.

Signed-off-by: Quentin Gliech <quenting@element.io>
---
 changelog.d/13093.misc              |  1 +
 synapse/rest/client/directory.py    | 35 +++++++++++------------------
 tests/rest/client/test_directory.py | 34 ++++++++++++++++++++++++++++
 3 files changed, 48 insertions(+), 22 deletions(-)
 create mode 100644 changelog.d/13093.misc

diff --git a/changelog.d/13093.misc b/changelog.d/13093.misc
new file mode 100644
index 000000000000..2547c87fa481
--- /dev/null
+++ b/changelog.d/13093.misc
@@ -0,0 +1 @@
+Simplify the alias deletion logic as an application service.
diff --git a/synapse/rest/client/directory.py b/synapse/rest/client/directory.py
index e181a0dde2f8..9639d4fe2c8c 100644
--- a/synapse/rest/client/directory.py
+++ b/synapse/rest/client/directory.py
@@ -17,13 +17,7 @@
 
 from twisted.web.server import Request
 
-from synapse.api.errors import (
-    AuthError,
-    Codes,
-    InvalidClientCredentialsError,
-    NotFoundError,
-    SynapseError,
-)
+from synapse.api.errors import AuthError, Codes, NotFoundError, SynapseError
 from synapse.http.server import HttpServer
 from synapse.http.servlet import RestServlet, parse_json_object_from_request
 from synapse.http.site import SynapseRequest
@@ -96,30 +90,27 @@ async def on_DELETE(
         self, request: SynapseRequest, room_alias: str
     ) -> Tuple[int, JsonDict]:
         room_alias_obj = RoomAlias.from_string(room_alias)
+        requester = await self.auth.get_user_by_req(request)
 
-        try:
-            service = self.auth.get_appservice_by_req(request)
+        if requester.app_service:
             await self.directory_handler.delete_appservice_association(
-                service, room_alias_obj
+                requester.app_service, room_alias_obj
             )
+
             logger.info(
                 "Application service at %s deleted alias %s",
-                service.url,
+                requester.app_service.url,
                 room_alias_obj.to_string(),
             )
-            return 200, {}
-        except InvalidClientCredentialsError:
-            # fallback to default user behaviour if they aren't an AS
-            pass
-
-        requester = await self.auth.get_user_by_req(request)
-        user = requester.user
 
-        await self.directory_handler.delete_association(requester, room_alias_obj)
+        else:
+            await self.directory_handler.delete_association(requester, room_alias_obj)
 
-        logger.info(
-            "User %s deleted alias %s", user.to_string(), room_alias_obj.to_string()
-        )
+            logger.info(
+                "User %s deleted alias %s",
+                requester.user.to_string(),
+                room_alias_obj.to_string(),
+            )
 
         return 200, {}
 
diff --git a/tests/rest/client/test_directory.py b/tests/rest/client/test_directory.py
index aca03afd0e52..67473a68d71a 100644
--- a/tests/rest/client/test_directory.py
+++ b/tests/rest/client/test_directory.py
@@ -16,6 +16,7 @@
 
 from twisted.test.proto_helpers import MemoryReactor
 
+from synapse.appservice import ApplicationService
 from synapse.rest import admin
 from synapse.rest.client import directory, login, room
 from synapse.server import HomeServer
@@ -129,6 +130,39 @@ def test_deleting_alias_via_directory(self) -> None:
         )
         self.assertEqual(channel.code, HTTPStatus.OK, channel.result)
 
+    def test_deleting_alias_via_directory_appservice(self) -> None:
+        user_id = "@as:test"
+        as_token = "i_am_an_app_service"
+
+        appservice = ApplicationService(
+            as_token,
+            id="1234",
+            namespaces={"aliases": [{"regex": "#asns-*", "exclusive": True}]},
+            sender=user_id,
+        )
+        self.hs.get_datastores().main.services_cache.append(appservice)
+
+        # Add an alias for the room, as the appservice
+        alias = RoomAlias(f"asns-{random_string(5)}", self.hs.hostname).to_string()
+        data = {"room_id": self.room_id}
+        request_data = json.dumps(data)
+
+        channel = self.make_request(
+            "PUT",
+            f"/_matrix/client/r0/directory/room/{alias}",
+            request_data,
+            access_token=as_token,
+        )
+        self.assertEqual(channel.code, HTTPStatus.OK, channel.result)
+
+        # Then try to remove the alias, as the appservice
+        channel = self.make_request(
+            "DELETE",
+            f"/_matrix/client/r0/directory/room/{alias}",
+            access_token=as_token,
+        )
+        self.assertEqual(channel.code, HTTPStatus.OK, channel.result)
+
     def test_deleting_nonexistant_alias(self) -> None:
         # Check that no alias exists
         alias = "#potato:test"