Handle missing data in power levels events during room upgrade. (#9395)

3 files changed, 162 insertions, 5 deletions

diff --git a/changelog.d/9395.bugfix b/changelog.d/9395.bugfix
new file mode 100644
index 0000000000..d45cc4ffb9
--- /dev/null
+++ b/changelog.d/9395.bugfix
@@ -0,0 +1 @@
+Fix a long-standing bug when upgrading a room: "TypeError: '>' not supported between instances of 'NoneType' and 'int'".
diff --git a/synapse/handlers/room.py b/synapse/handlers/room.py
index 3cf6635821..591a82f459 100644
--- a/synapse/handlers/room.py
+++ b/synapse/handlers/room.py
@@ -425,17 +425,20 @@ class RoomCreationHandler(BaseHandler):
 
         # Copy over user power levels now as this will not be possible with >100PL users once
         # the room has been created
-
         # Calculate the minimum power level needed to clone the room
         event_power_levels = power_levels.get("events", {})
-        state_default = power_levels.get("state_default", 0)
-        ban = power_levels.get("ban")
+        state_default = power_levels.get("state_default", 50)
+        ban = power_levels.get("ban", 50)
         needed_power_level = max(state_default, ban, max(event_power_levels.values()))
 
+        # Get the user's current power level, this matches the logic in get_user_power_level,
+        # but without the entire state map.
+        user_power_levels = power_levels.setdefault("users", {})
+        users_default = power_levels.get("users_default", 0)
+        current_power_level = user_power_levels.get(user_id, users_default)
         # Raise the requester's power level in the new room if necessary
-        current_power_level = power_levels["users"][user_id]
         if current_power_level < needed_power_level:
-            power_levels["users"][user_id] = needed_power_level
+            user_power_levels[user_id] = needed_power_level
 
         await self._send_events_for_new_room(
             requester,
diff --git a/tests/rest/client/v2_alpha/test_upgrade_room.py b/tests/rest/client/v2_alpha/test_upgrade_room.py
new file mode 100644
index 0000000000..7c22293d6d
--- /dev/null
+++ b/tests/rest/client/v2_alpha/test_upgrade_room.py
@@ -0,0 +1,153 @@
+# -*- coding: utf-8 -*-
+# Copyright 2021 The Matrix.org Foundation 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 typing import Optional
+
+from synapse.config.server import DEFAULT_ROOM_VERSION
+from synapse.rest import admin
+from synapse.rest.client.v1 import login, room
+from synapse.rest.client.v2_alpha import room_upgrade_rest_servlet
+
+from tests import unittest
+from tests.server import FakeChannel
+
+
+class UpgradeRoomTest(unittest.HomeserverTestCase):
+    servlets = [
+        admin.register_servlets,
+        login.register_servlets,
+        room.register_servlets,
+        room_upgrade_rest_servlet.register_servlets,
+    ]
+
+    def prepare(self, reactor, clock, hs):
+        self.store = hs.get_datastore()
+        self.handler = hs.get_user_directory_handler()
+
+        self.creator = self.register_user("creator", "pass")
+        self.creator_token = self.login(self.creator, "pass")
+
+        self.other = self.register_user("user", "pass")
+        self.other_token = self.login(self.other, "pass")
+
+        self.room_id = self.helper.create_room_as(self.creator, tok=self.creator_token)
+        self.helper.join(self.room_id, self.other, tok=self.other_token)
+
+    def _upgrade_room(self, token: Optional[str] = None) -> FakeChannel:
+        # We never want a cached response.
+        self.reactor.advance(5 * 60 + 1)
+
+        return self.make_request(
+            "POST",
+            "/_matrix/client/r0/rooms/%s/upgrade" % self.room_id,
+            # This will upgrade a room to the same version, but that's fine.
+            content={"new_version": DEFAULT_ROOM_VERSION},
+            access_token=token or self.creator_token,
+        )
+
+    def test_upgrade(self):
+        """
+        Upgrading a room should work fine.
+        """
+        channel = self._upgrade_room()
+        self.assertEquals(200, channel.code, channel.result)
+        self.assertIn("replacement_room", channel.json_body)
+
+    def test_not_in_room(self):
+        """
+        Upgrading a room should work fine.
+        """
+        # THe user isn't in the room.
+        roomless = self.register_user("roomless", "pass")
+        roomless_token = self.login(roomless, "pass")
+
+        channel = self._upgrade_room(roomless_token)
+        self.assertEquals(403, channel.code, channel.result)
+
+    def test_power_levels(self):
+        """
+        Another user can upgrade the room if their power level is increased.
+        """
+        # The other user doesn't have the proper power level.
+        channel = self._upgrade_room(self.other_token)
+        self.assertEquals(403, channel.code, channel.result)
+
+        # Increase the power levels so that this user can upgrade.
+        power_levels = self.helper.get_state(
+            self.room_id, "m.room.power_levels", tok=self.creator_token,
+        )
+        power_levels["users"][self.other] = 100
+        self.helper.send_state(
+            self.room_id,
+            "m.room.power_levels",
+            body=power_levels,
+            tok=self.creator_token,
+        )
+
+        # The upgrade should succeed!
+        channel = self._upgrade_room(self.other_token)
+        self.assertEquals(200, channel.code, channel.result)
+
+    def test_power_levels_user_default(self):
+        """
+        Another user can upgrade the room if the default power level for users is increased.
+        """
+        # The other user doesn't have the proper power level.
+        channel = self._upgrade_room(self.other_token)
+        self.assertEquals(403, channel.code, channel.result)
+
+        # Increase the power levels so that this user can upgrade.
+        power_levels = self.helper.get_state(
+            self.room_id, "m.room.power_levels", tok=self.creator_token,
+        )
+        power_levels["users_default"] = 100
+        self.helper.send_state(
+            self.room_id,
+            "m.room.power_levels",
+            body=power_levels,
+            tok=self.creator_token,
+        )
+
+        # The upgrade should succeed!
+        channel = self._upgrade_room(self.other_token)
+        self.assertEquals(200, channel.code, channel.result)
+
+    def test_power_levels_tombstone(self):
+        """
+        Another user can upgrade the room if they can send the tombstone event.
+        """
+        # The other user doesn't have the proper power level.
+        channel = self._upgrade_room(self.other_token)
+        self.assertEquals(403, channel.code, channel.result)
+
+        # Increase the power levels so that this user can upgrade.
+        power_levels = self.helper.get_state(
+            self.room_id, "m.room.power_levels", tok=self.creator_token,
+        )
+        power_levels["events"]["m.room.tombstone"] = 0
+        self.helper.send_state(
+            self.room_id,
+            "m.room.power_levels",
+            body=power_levels,
+            tok=self.creator_token,
+        )
+
+        # The upgrade should succeed!
+        channel = self._upgrade_room(self.other_token)
+        self.assertEquals(200, channel.code, channel.result)
+
+        power_levels = self.helper.get_state(
+            self.room_id, "m.room.power_levels", tok=self.creator_token,
+        )
+        self.assertNotIn(self.other, power_levels["users"])