Fixup

synapse/rest/admin/__init__.py

@@ -42,6 +42,7 @@ from synapse.rest.admin.rooms import (
     DeleteRoomRestServlet,
     JoinRoomAliasServlet,
     ListRoomRestServlet,
+    MakeRoomAdminRoomServlet,
     RoomMembersRestServlet,
     RoomRestServlet,
     ShutdownRoomRestServlet,
@@ -232,6 +233,7 @@ def register_servlets(hs, http_server):
     EventReportDetailRestServlet(hs).register(http_server)
     EventReportsRestServlet(hs).register(http_server)
     PushersRestServlet(hs).register(http_server)
+    MakeRoomAdminRoomServlet(hs).register(http_server)
 
 
 def register_servlets_for_client_rest_resource(hs, http_server):

synapse/rest/admin/rooms.py

@@ -17,7 +17,7 @@ from http import HTTPStatus
 from typing import TYPE_CHECKING, List, Optional
 
 from synapse.api.constants import EventTypes, JoinRules, Membership
-from synapse.api.errors import Codes, NotFoundError, SynapseError
+from synapse.api.errors import AuthError, Codes, NotFoundError, SynapseError
 from synapse.http.servlet import (
     RestServlet,
     assert_params_in_dict,
@@ -344,6 +344,17 @@ class JoinRoomAliasServlet(RestServlet):
 
 
 class MakeRoomAdminRoomServlet(RestServlet):
+    """Allows a server admin to get power in a room if a local user has power in
+    a room. Will also invite the user if they're not in the room and its a
+    private room. Can specify another user (rather than the admin user) to be
+    granted power, e.g.:
+
+        POST /_synapse/admin/v1/make_room_admin/<room_id_or_alias>
+        {
+            "user_id": "@foo:example.com"
+        }
+    """
+
     PATTERNS = admin_patterns("/make_room_admin/(?P<room_identifier>[^/]*)")
 
     def __init__(self, hs: "HomeServer"):
@@ -359,6 +370,7 @@ class MakeRoomAdminRoomServlet(RestServlet):
         await assert_user_is_admin(self.auth, requester.user)
         content = parse_json_object_from_request(request, allow_empty_body=True)
 
+        # Resolve to a room ID, if necessary.
         if RoomID.is_valid(room_identifier):
             room_id = room_identifier
         elif RoomAlias.is_valid(room_identifier):
@@ -370,10 +382,11 @@ class MakeRoomAdminRoomServlet(RestServlet):
                 400, "%s was not legal room ID or room alias" % (room_identifier,)
             )
 
+        # Which user to grant room admin rights to.
         user_to_add = content.get("user_id", requester.user.to_string())
 
+        # Figure out which local users currently have power in the room, if any.
         room_state = await self.state_handler.get_current_state(room_id)
-
         if not room_state:
             raise SynapseError(400, "Server not in room")
 
@@ -381,33 +394,59 @@ class MakeRoomAdminRoomServlet(RestServlet):
         power_levels = room_state.get((EventTypes.PowerLevels, ""))
 
         if power_levels is not None:
+            # We pick the local user with the highest power.
+            user_power = power_levels.content.get("users", {})
             admin_users = [
                 user_id
-                for user_id, power in power_levels.content.get("users")
+                for user_id, power in user_power.items()
                 if self.is_mine_id(user_id)
             ]
-            admin_users.sort(key=lambda user: power_levels.content.get("users")[user])
+            admin_users.sort(key=lambda user: user_power[user])
+
+            if not admin_users:
+                raise SynapseError(400, "No local admin user in room")
 
             admin_user_id = admin_users[-1]
 
             pl_content = power_levels.content
         else:
+            # If there is no power level events then the creator has rights.
+            pl_content = {}
             admin_user_id = create_event.sender
             if not self.is_mine_id(admin_user_id):
-                raise SynapseError(400, "No local admin user in room")
+                raise SynapseError(
+                    400, "No local admin user in room",
+                )
+
+        # Grant the user power equal to the room admin by attempting to send an
+        # updated power level event.
+        new_pl_content = dict(pl_content)
+        new_pl_content["users"] = dict(pl_content.get("users", {}))
+        new_pl_content["users"][user_to_add] = new_pl_content["users"][admin_user_id]
 
         fake_requester = create_requester(
             admin_user_id, authenticated_entity=requester.authenticated_entity,
         )
 
-        new_pl_content = dict(pl_content)
-        new_pl_content["users"] = dict(pl_content.get("users", {}))
-        new_pl_content["users"][user_to_add] = new_pl_content["users"][admin_user_id]
-
-        await self.event_creation_handler.create_and_send_nonmember_event(
-            fake_requester, event_dict=new_pl_content,
-        )
+        try:
+            await self.event_creation_handler.create_and_send_nonmember_event(
+                fake_requester,
+                event_dict={
+                    "content": new_pl_content,
+                    "sender": admin_user_id,
+                    "type": EventTypes.PowerLevels,
+                    "state_key": "",
+                    "room_id": room_id,
+                },
+            )
+        except AuthError:
+            # The admin user we found turned out not to have enough power.
+            raise SynapseError(
+                400, "No local admin user in room with power to update power levels."
+            )
 
+        # Now we check if the user we're granting admin rights to is already in
+        # the room. If not and its not a public room we invite them.
         member_event = room_state.get((EventTypes.Member, user_to_add))
         is_joined = False
         if member_event: