Delete server-side backup keys when deactivating an account. (#15181)

6 files changed, 291 insertions, 3 deletions

diff --git a/changelog.d/15181.bugfix b/changelog.d/15181.bugfix
new file mode 100644
index 0000000000..191bb6f611
--- /dev/null
+++ b/changelog.d/15181.bugfix
@@ -0,0 +1 @@
+Delete server-side backup keys when deactivating an account.
\ No newline at end of file
diff --git a/synapse/_scripts/synapse_port_db.py b/synapse/_scripts/synapse_port_db.py
index 1dcb397ba4..a58ae2a308 100755
--- a/synapse/_scripts/synapse_port_db.py
+++ b/synapse/_scripts/synapse_port_db.py
@@ -59,6 +59,7 @@ from synapse.storage.databases.main.account_data import AccountDataWorkerStore
 from synapse.storage.databases.main.client_ips import ClientIpBackgroundUpdateStore
 from synapse.storage.databases.main.deviceinbox import DeviceInboxBackgroundUpdateStore
 from synapse.storage.databases.main.devices import DeviceBackgroundUpdateStore
+from synapse.storage.databases.main.e2e_room_keys import EndToEndRoomKeyBackgroundStore
 from synapse.storage.databases.main.end_to_end_keys import EndToEndKeyBackgroundStore
 from synapse.storage.databases.main.event_push_actions import EventPushActionsStore
 from synapse.storage.databases.main.events_bg_updates import (
@@ -225,6 +226,7 @@ class Store(
     MainStateBackgroundUpdateStore,
     UserDirectoryBackgroundUpdateStore,
     EndToEndKeyBackgroundStore,
+    EndToEndRoomKeyBackgroundStore,
     StatsStore,
     AccountDataWorkerStore,
     PushRuleStore,
diff --git a/synapse/handlers/deactivate_account.py b/synapse/handlers/deactivate_account.py
index d31263c717..bd5867491b 100644
--- a/synapse/handlers/deactivate_account.py
+++ b/synapse/handlers/deactivate_account.py
@@ -176,6 +176,9 @@ class DeactivateAccountHandler:
         # Remove account data (including ignored users and push rules).
         await self.store.purge_account_data_for_user(user_id)
 
+        # Delete any server-side backup keys
+        await self.store.bulk_delete_backup_keys_and_versions_for_user(user_id)
+
         # Let modules know the user has been deactivated.
         await self._third_party_rules.on_user_deactivation_status_changed(
             user_id,
diff --git a/synapse/storage/databases/main/e2e_room_keys.py b/synapse/storage/databases/main/e2e_room_keys.py
index 9f8d2e4bea..d01f28cc80 100644
--- a/synapse/storage/databases/main/e2e_room_keys.py
+++ b/synapse/storage/databases/main/e2e_room_keys.py
@@ -13,17 +13,24 @@
 # See the License for the specific language governing permissions and
 # limitations under the License.
 
-from typing import Dict, Iterable, Mapping, Optional, Tuple, cast
+from typing import TYPE_CHECKING, Dict, Iterable, Mapping, Optional, Tuple, cast
 
 from typing_extensions import Literal, TypedDict
 
 from synapse.api.errors import StoreError
 from synapse.logging.opentracing import log_kv, trace
 from synapse.storage._base import SQLBaseStore, db_to_json
-from synapse.storage.database import LoggingTransaction
+from synapse.storage.database import (
+    DatabasePool,
+    LoggingDatabaseConnection,
+    LoggingTransaction,
+)
 from synapse.types import JsonDict, JsonSerializable, StreamKeyType
 from synapse.util import json_encoder
 
+if TYPE_CHECKING:
+    from synapse.server import HomeServer
+
 
 class RoomKey(TypedDict):
     """`KeyBackupData` in the Matrix spec.
@@ -37,7 +44,82 @@ class RoomKey(TypedDict):
     session_data: JsonSerializable
 
 
-class EndToEndRoomKeyStore(SQLBaseStore):
+class EndToEndRoomKeyBackgroundStore(SQLBaseStore):
+    def __init__(
+        self,
+        database: DatabasePool,
+        db_conn: LoggingDatabaseConnection,
+        hs: "HomeServer",
+    ):
+        super().__init__(database, db_conn, hs)
+
+        self.db_pool.updates.register_background_update_handler(
+            "delete_e2e_backup_keys_for_deactivated_users",
+            self._delete_e2e_backup_keys_for_deactivated_users,
+        )
+
+    def _delete_keys_txn(self, txn: LoggingTransaction, user_id: str) -> None:
+        self.db_pool.simple_delete_txn(
+            txn,
+            table="e2e_room_keys",
+            keyvalues={"user_id": user_id},
+        )
+
+        self.db_pool.simple_delete_txn(
+            txn,
+            table="e2e_room_keys_versions",
+            keyvalues={"user_id": user_id},
+        )
+
+    async def _delete_e2e_backup_keys_for_deactivated_users(
+        self, progress: JsonDict, batch_size: int
+    ) -> int:
+        """
+        Retroactively purges account data for users that have already been deactivated.
+        Gets run as a background update caused by a schema delta.
+        """
+
+        last_user: str = progress.get("last_user", "")
+
+        def _delete_backup_keys_for_deactivated_users_txn(
+            txn: LoggingTransaction,
+        ) -> int:
+            sql = """
+                SELECT name FROM users
+                WHERE deactivated = ? and name > ?
+                ORDER BY name ASC
+                LIMIT ?
+            """
+
+            txn.execute(sql, (1, last_user, batch_size))
+            users = [row[0] for row in txn]
+
+            for user in users:
+                self._delete_keys_txn(txn, user)
+
+            if users:
+                self.db_pool.updates._background_update_progress_txn(
+                    txn,
+                    "delete_e2e_backup_keys_for_deactivated_users",
+                    {"last_user": users[-1]},
+                )
+
+            return len(users)
+
+        number_deleted = await self.db_pool.runInteraction(
+            "_delete_backup_keys_for_deactivated_users",
+            _delete_backup_keys_for_deactivated_users_txn,
+        )
+
+        if number_deleted < batch_size:
+            await self.db_pool.updates._end_background_update(
+                "delete_e2e_backup_keys_for_deactivated_users"
+            )
+
+        return number_deleted
+
+
+class EndToEndRoomKeyStore(EndToEndRoomKeyBackgroundStore):
     """The store for end to end room key backups.
 
     See https://spec.matrix.org/v1.1/client-server-api/#server-side-key-backups
@@ -550,3 +632,29 @@ class EndToEndRoomKeyStore(SQLBaseStore):
         await self.db_pool.runInteraction(
             "delete_e2e_room_keys_version", _delete_e2e_room_keys_version_txn
         )
+
+    async def bulk_delete_backup_keys_and_versions_for_user(self, user_id: str) -> None:
+        """
+        Bulk deletes all backup room keys and versions for a given user.
+
+        Args:
+            user_id: the user whose backup keys and versions we're deleting
+        """
+
+        def _delete_all_e2e_room_keys_and_versions_txn(txn: LoggingTransaction) -> None:
+            self.db_pool.simple_delete_txn(
+                txn,
+                table="e2e_room_keys",
+                keyvalues={"user_id": user_id},
+            )
+
+            self.db_pool.simple_delete_txn(
+                txn,
+                table="e2e_room_keys_versions",
+                keyvalues={"user_id": user_id},
+            )
+
+        await self.db_pool.runInteraction(
+            "delete_all_e2e_room_keys_and_versions",
+            _delete_all_e2e_room_keys_and_versions_txn,
+        )
diff --git a/synapse/storage/schema/main/delta/74/04_delete_e2e_backup_keys_for_deactivated_users.sql b/synapse/storage/schema/main/delta/74/04_delete_e2e_backup_keys_for_deactivated_users.sql
new file mode 100644
index 0000000000..a194f4cece
--- /dev/null
+++ b/synapse/storage/schema/main/delta/74/04_delete_e2e_backup_keys_for_deactivated_users.sql
@@ -0,0 +1,17 @@
+/* Copyright 2023 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.
+ */
+
+INSERT INTO background_updates (ordering, update_name, progress_json) VALUES
+  (7404, 'delete_e2e_backup_keys_for_deactivated_users', '{}');
\ No newline at end of file
diff --git a/tests/rest/client/test_account.py b/tests/rest/client/test_account.py
index 7f675c44a2..ac19f3c6da 100644
--- a/tests/rest/client/test_account.py
+++ b/tests/rest/client/test_account.py
@@ -474,6 +474,163 @@ class DeactivateTestCase(unittest.HomeserverTestCase):
         self.assertEqual(len(memberships), 1, memberships)
         self.assertEqual(memberships[0].room_id, room_id, memberships)
 
+    def test_deactivate_account_deletes_server_side_backup_keys(self) -> None:
+        key_handler = self.hs.get_e2e_room_keys_handler()
+        room_keys = {
+            "rooms": {
+                "!abc:matrix.org": {
+                    "sessions": {
+                        "c0ff33": {
+                            "first_message_index": 1,
+                            "forwarded_count": 1,
+                            "is_verified": False,
+                            "session_data": "SSBBTSBBIEZJU0gK",
+                        }
+                    }
+                }
+            }
+        }
+
+        user_id = self.register_user("missPiggy", "test")
+        tok = self.login("missPiggy", "test")
+
+        # add some backup keys/versions
+        version = self.get_success(
+            key_handler.create_version(
+                user_id,
+                {
+                    "algorithm": "m.megolm_backup.v1",
+                    "auth_data": "first_version_auth_data",
+                },
+            )
+        )
+
+        self.get_success(key_handler.upload_room_keys(user_id, version, room_keys))
+
+        version2 = self.get_success(
+            key_handler.create_version(
+                user_id,
+                {
+                    "algorithm": "m.megolm_backup.v1",
+                    "auth_data": "second_version_auth_data",
+                },
+            )
+        )
+
+        self.get_success(key_handler.upload_room_keys(user_id, version2, room_keys))
+
+        self.deactivate(user_id, tok)
+        store = self.hs.get_datastores().main
+
+        # Check that the user has been marked as deactivated.
+        self.assertTrue(self.get_success(store.get_user_deactivated_status(user_id)))
+
+        # Check that there are no entries in 'e2e_room_keys` and `e2e_room_keys_versions`
+        res = self.get_success(
+            self.hs.get_datastores().main.db_pool.simple_select_list(
+                "e2e_room_keys", {"user_id": user_id}, "*", "simple_select"
+            )
+        )
+        self.assertEqual(len(res), 0)
+
+        res2 = self.get_success(
+            self.hs.get_datastores().main.db_pool.simple_select_list(
+                "e2e_room_keys_versions", {"user_id": user_id}, "*", "simple_select"
+            )
+        )
+        self.assertEqual(len(res2), 0)
+
+    def test_background_update_deletes_deactivated_users_server_side_backup_keys(
+        self,
+    ) -> None:
+        key_handler = self.hs.get_e2e_room_keys_handler()
+        room_keys = {
+            "rooms": {
+                "!abc:matrix.org": {
+                    "sessions": {
+                        "c0ff33": {
+                            "first_message_index": 1,
+                            "forwarded_count": 1,
+                            "is_verified": False,
+                            "session_data": "SSBBTSBBIEZJU0gK",
+                        }
+                    }
+                }
+            }
+        }
+        self.store = self.hs.get_datastores().main
+
+        # create a bunch of users and add keys for them
+        users = []
+        for i in range(0, 20):
+            user_id = self.register_user("missPiggy" + str(i), "test")
+            users.append((user_id,))
+
+            # add some backup keys/versions
+            version = self.get_success(
+                key_handler.create_version(
+                    user_id,
+                    {
+                        "algorithm": "m.megolm_backup.v1",
+                        "auth_data": str(i) + "_version_auth_data",
+                    },
+                )
+            )
+
+            self.get_success(key_handler.upload_room_keys(user_id, version, room_keys))
+
+            version2 = self.get_success(
+                key_handler.create_version(
+                    user_id,
+                    {
+                        "algorithm": "m.megolm_backup.v1",
+                        "auth_data": str(i) + "_version_auth_data",
+                    },
+                )
+            )
+
+            self.get_success(key_handler.upload_room_keys(user_id, version2, room_keys))
+
+        # deactivate most of the users by editing DB
+        self.get_success(
+            self.store.db_pool.simple_update_many(
+                table="users",
+                key_names=("name",),
+                key_values=users[0:18],
+                value_names=("deactivated",),
+                value_values=[(1,) for i in range(1, 19)],
+                desc="",
+            )
+        )
+
+        # run background update
+        self.get_success(
+            self.store.db_pool.simple_insert(
+                "background_updates",
+                {
+                    "update_name": "delete_e2e_backup_keys_for_deactivated_users",
+                    "progress_json": "{}",
+                },
+            )
+        )
+        self.store.db_pool.updates._all_done = False
+        self.wait_for_background_updates()
+
+        # check that keys are deleted for the deactivated users but not the others
+        res = self.get_success(
+            self.hs.get_datastores().main.db_pool.simple_select_list(
+                "e2e_room_keys", None, ("user_id",), "simple_select"
+            )
+        )
+        self.assertEqual(len(res), 4)
+
+        res2 = self.get_success(
+            self.hs.get_datastores().main.db_pool.simple_select_list(
+                "e2e_room_keys_versions", None, ("user_id",), "simple_select"
+            )
+        )
+        self.assertEqual(len(res2), 4)
+
     def deactivate(self, user_id: str, tok: str) -> None:
         request_data = {
             "auth": {