diff --git a/changelog.d/15077.feature b/changelog.d/15077.feature
new file mode 100644
index 0000000000..384e751056
--- /dev/null
+++ b/changelog.d/15077.feature
@@ -0,0 +1 @@
+Experimental support for MSC3967 to not require UIA for setting up cross-signing on first use.
diff --git a/synapse/config/experimental.py b/synapse/config/experimental.py
index bc38fae0b6..7c81f055b6 100644
--- a/synapse/config/experimental.py
+++ b/synapse/config/experimental.py
@@ -194,3 +194,6 @@ class ExperimentalConfig(Config):
self.msc3966_exact_event_property_contains = experimental.get(
"msc3966_exact_event_property_contains", False
)
+
+ # MSC3967: Do not require UIA when first uploading cross signing keys
+ self.msc3967_enabled = experimental.get("msc3967_enabled", False)
diff --git a/synapse/handlers/e2e_keys.py b/synapse/handlers/e2e_keys.py
index 43cbece21b..4e9c8d8db0 100644
--- a/synapse/handlers/e2e_keys.py
+++ b/synapse/handlers/e2e_keys.py
@@ -1301,6 +1301,20 @@ class E2eKeysHandler:
return desired_key_data
+ async def is_cross_signing_set_up_for_user(self, user_id: str) -> bool:
+ """Checks if the user has cross-signing set up
+
+ Args:
+ user_id: The user to check
+
+ Returns:
+ True if the user has cross-signing set up, False otherwise
+ """
+ existing_master_key = await self.store.get_e2e_cross_signing_key(
+ user_id, "master"
+ )
+ return existing_master_key is not None
+
def _check_cross_signing_key(
key: JsonDict, user_id: str, key_type: str, signing_key: Optional[VerifyKey] = None
diff --git a/synapse/rest/client/keys.py b/synapse/rest/client/keys.py
index 7873b363c0..32bb8b9a91 100644
--- a/synapse/rest/client/keys.py
+++ b/synapse/rest/client/keys.py
@@ -312,15 +312,29 @@ class SigningKeyUploadServlet(RestServlet):
user_id = requester.user.to_string()
body = parse_json_object_from_request(request)
- await self.auth_handler.validate_user_via_ui_auth(
- requester,
- request,
- body,
- "add a device signing key to your account",
- # Allow skipping of UI auth since this is frequently called directly
- # after login and it is silly to ask users to re-auth immediately.
- can_skip_ui_auth=True,
- )
+ if self.hs.config.experimental.msc3967_enabled:
+ if await self.e2e_keys_handler.is_cross_signing_set_up_for_user(user_id):
+ # If we already have a master key then cross signing is set up and we require UIA to reset
+ await self.auth_handler.validate_user_via_ui_auth(
+ requester,
+ request,
+ body,
+ "reset the device signing key on your account",
+ # Do not allow skipping of UIA auth.
+ can_skip_ui_auth=False,
+ )
+ # Otherwise we don't require UIA since we are setting up cross signing for first time
+ else:
+ # Previous behaviour is to always require UIA but allow it to be skipped
+ await self.auth_handler.validate_user_via_ui_auth(
+ requester,
+ request,
+ body,
+ "add a device signing key to your account",
+ # Allow skipping of UI auth since this is frequently called directly
+ # after login and it is silly to ask users to re-auth immediately.
+ can_skip_ui_auth=True,
+ )
result = await self.e2e_keys_handler.upload_signing_keys_for_user(user_id, body)
return 200, result
diff --git a/tests/rest/client/test_keys.py b/tests/rest/client/test_keys.py
index 741fecea77..8ee5489057 100644
--- a/tests/rest/client/test_keys.py
+++ b/tests/rest/client/test_keys.py
@@ -14,12 +14,21 @@
from http import HTTPStatus
+from signedjson.key import (
+ encode_verify_key_base64,
+ generate_signing_key,
+ get_verify_key,
+)
+from signedjson.sign import sign_json
+
from synapse.api.errors import Codes
from synapse.rest import admin
from synapse.rest.client import keys, login
+from synapse.types import JsonDict
from tests import unittest
from tests.http.server._base import make_request_with_cancellation_test
+from tests.unittest import override_config
class KeyQueryTestCase(unittest.HomeserverTestCase):
@@ -118,3 +127,135 @@ class KeyQueryTestCase(unittest.HomeserverTestCase):
self.assertEqual(200, channel.code, msg=channel.result["body"])
self.assertIn(bob, channel.json_body["device_keys"])
+
+ def make_device_keys(self, user_id: str, device_id: str) -> JsonDict:
+ # We only generate a master key to simplify the test.
+ master_signing_key = generate_signing_key(device_id)
+ master_verify_key = encode_verify_key_base64(get_verify_key(master_signing_key))
+
+ return {
+ "master_key": sign_json(
+ {
+ "user_id": user_id,
+ "usage": ["master"],
+ "keys": {"ed25519:" + master_verify_key: master_verify_key},
+ },
+ user_id,
+ master_signing_key,
+ ),
+ }
+
+ def test_device_signing_with_uia(self) -> None:
+ """Device signing key upload requires UIA."""
+ password = "wonderland"
+ device_id = "ABCDEFGHI"
+ alice_id = self.register_user("alice", password)
+ alice_token = self.login("alice", password, device_id=device_id)
+
+ content = self.make_device_keys(alice_id, device_id)
+
+ channel = self.make_request(
+ "POST",
+ "/_matrix/client/v3/keys/device_signing/upload",
+ content,
+ alice_token,
+ )
+
+ self.assertEqual(channel.code, HTTPStatus.UNAUTHORIZED, channel.result)
+ # Grab the session
+ session = channel.json_body["session"]
+ # Ensure that flows are what is expected.
+ self.assertIn({"stages": ["m.login.password"]}, channel.json_body["flows"])
+
+ # add UI auth
+ content["auth"] = {
+ "type": "m.login.password",
+ "identifier": {"type": "m.id.user", "user": alice_id},
+ "password": password,
+ "session": session,
+ }
+
+ channel = self.make_request(
+ "POST",
+ "/_matrix/client/v3/keys/device_signing/upload",
+ content,
+ alice_token,
+ )
+
+ self.assertEqual(channel.code, HTTPStatus.OK, channel.result)
+
+ @override_config({"ui_auth": {"session_timeout": "15m"}})
+ def test_device_signing_with_uia_session_timeout(self) -> None:
+ """Device signing key upload requires UIA buy passes with grace period."""
+ password = "wonderland"
+ device_id = "ABCDEFGHI"
+ alice_id = self.register_user("alice", password)
+ alice_token = self.login("alice", password, device_id=device_id)
+
+ content = self.make_device_keys(alice_id, device_id)
+
+ channel = self.make_request(
+ "POST",
+ "/_matrix/client/v3/keys/device_signing/upload",
+ content,
+ alice_token,
+ )
+
+ self.assertEqual(channel.code, HTTPStatus.OK, channel.result)
+
+ @override_config(
+ {
+ "experimental_features": {"msc3967_enabled": True},
+ "ui_auth": {"session_timeout": "15s"},
+ }
+ )
+ def test_device_signing_with_msc3967(self) -> None:
+ """Device signing key follows MSC3967 behaviour when enabled."""
+ password = "wonderland"
+ device_id = "ABCDEFGHI"
+ alice_id = self.register_user("alice", password)
+ alice_token = self.login("alice", password, device_id=device_id)
+
+ keys1 = self.make_device_keys(alice_id, device_id)
+
+ # Initial request should succeed as no existing keys are present.
+ channel = self.make_request(
+ "POST",
+ "/_matrix/client/v3/keys/device_signing/upload",
+ keys1,
+ alice_token,
+ )
+ self.assertEqual(channel.code, HTTPStatus.OK, channel.result)
+
+ keys2 = self.make_device_keys(alice_id, device_id)
+
+ # Subsequent request should require UIA as keys already exist even though session_timeout is set.
+ channel = self.make_request(
+ "POST",
+ "/_matrix/client/v3/keys/device_signing/upload",
+ keys2,
+ alice_token,
+ )
+ self.assertEqual(channel.code, HTTPStatus.UNAUTHORIZED, channel.result)
+
+ # Grab the session
+ session = channel.json_body["session"]
+ # Ensure that flows are what is expected.
+ self.assertIn({"stages": ["m.login.password"]}, channel.json_body["flows"])
+
+ # add UI auth
+ keys2["auth"] = {
+ "type": "m.login.password",
+ "identifier": {"type": "m.id.user", "user": alice_id},
+ "password": password,
+ "session": session,
+ }
+
+ # Request should complete
+ channel = self.make_request(
+ "POST",
+ "/_matrix/client/v3/keys/device_signing/upload",
+ keys2,
+ alice_token,
+ )
+ self.assertEqual(channel.code, HTTPStatus.OK, channel.result)
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