Add an Admin API to temporarily grant the ability to update an existing cross-signing key without UIA (#16634)

2 files changed, 99 insertions, 0 deletions

diff --git a/synapse/storage/databases/main/end_to_end_keys.py b/synapse/storage/databases/main/end_to_end_keys.py
index 8cb61eaee3..9e98729330 100644
--- a/synapse/storage/databases/main/end_to_end_keys.py
+++ b/synapse/storage/databases/main/end_to_end_keys.py
@@ -1383,6 +1383,51 @@ class EndToEndKeyWorkerStore(EndToEndKeyBackgroundStore, CacheInvalidationWorker
 
         return otk_rows
 
+    async def get_master_cross_signing_key_updatable_before(
+        self, user_id: str
+    ) -> Tuple[bool, Optional[int]]:
+        """Get time before which a master cross-signing key may be replaced without UIA.
+
+        (UIA means "User-Interactive Auth".)
+
+        There are three cases to distinguish:
+         (1) No master cross-signing key.
+         (2) The key exists, but there is no replace-without-UI timestamp in the DB.
+         (3) The key exists, and has such a timestamp recorded.
+
+        Returns: a 2-tuple of:
+          - a boolean: is there a master cross-signing key already?
+          - an optional timestamp, directly taken from the DB.
+
+        In terms of the cases above, these are:
+         (1) (False, None).
+         (2) (True, None).
+         (3) (True, <timestamp in ms>).
+
+        """
+
+        def impl(txn: LoggingTransaction) -> Tuple[bool, Optional[int]]:
+            # We want to distinguish between three cases:
+            txn.execute(
+                """
+                SELECT updatable_without_uia_before_ms
+                FROM e2e_cross_signing_keys
+                WHERE user_id = ? AND keytype = 'master'
+                ORDER BY stream_id DESC
+                LIMIT 1
+            """,
+                (user_id,),
+            )
+            row = cast(Optional[Tuple[Optional[int]]], txn.fetchone())
+            if row is None:
+                return False, None
+            return True, row[0]
+
+        return await self.db_pool.runInteraction(
+            "e2e_cross_signing_keys",
+            impl,
+        )
+
 
 class EndToEndKeyStore(EndToEndKeyWorkerStore, SQLBaseStore):
     def __init__(
@@ -1630,3 +1675,42 @@ class EndToEndKeyStore(EndToEndKeyWorkerStore, SQLBaseStore):
             ],
             desc="add_e2e_signing_key",
         )
+
+    async def allow_master_cross_signing_key_replacement_without_uia(
+        self, user_id: str, duration_ms: int
+    ) -> Optional[int]:
+        """Mark this user's latest master key as being replaceable without UIA.
+
+        Said replacement will only be permitted for a short time after calling this
+        function. That time period is controlled by the duration argument.
+
+        Returns:
+            None, if there is no such key.
+            Otherwise, the timestamp before which replacement is allowed without UIA.
+        """
+        timestamp = self._clock.time_msec() + duration_ms
+
+        def impl(txn: LoggingTransaction) -> Optional[int]:
+            txn.execute(
+                """
+                UPDATE e2e_cross_signing_keys
+                SET updatable_without_uia_before_ms = ?
+                WHERE stream_id = (
+                    SELECT stream_id
+                    FROM e2e_cross_signing_keys
+                    WHERE user_id = ? AND keytype = 'master'
+                    ORDER BY stream_id DESC
+                    LIMIT 1
+                )
+            """,
+                (timestamp, user_id),
+            )
+            if txn.rowcount == 0:
+                return None
+
+            return timestamp
+
+        return await self.db_pool.runInteraction(
+            "allow_master_cross_signing_key_replacement_without_uia",
+            impl,
+        )
diff --git a/synapse/storage/schema/main/delta/83/05_cross_signing_key_update_grant.sql b/synapse/storage/schema/main/delta/83/05_cross_signing_key_update_grant.sql
new file mode 100644
index 0000000000..b74bdd71fa
--- /dev/null
+++ b/synapse/storage/schema/main/delta/83/05_cross_signing_key_update_grant.sql
@@ -0,0 +1,15 @@
+/* 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.
+ */
+ALTER TABLE e2e_cross_signing_keys ADD COLUMN updatable_without_uia_before_ms bigint DEFAULT NULL;
\ No newline at end of file