UIA: offer only available auth flows

changelog.d/8858.bugfix

@@ -0,0 +1 @@
+Fix a long-standing bug on Synapse instances supporting Single-Sign-On, where users would be prompted to enter their password to confirm certain actions, even though they have not set a password.

synapse/federation/transport/server.py

@@ -1462,7 +1462,7 @@ def register_servlets(hs, resource, authenticator, ratelimiter, servlet_groups=N
 
     Args:
         hs (synapse.server.HomeServer): homeserver
-        resource (TransportLayerServer): resource class to register to
+        resource (JsonResource): resource class to register to
         authenticator (Authenticator): authenticator to use
         ratelimiter (util.ratelimitutils.FederationRateLimiter): ratelimiter to use
         servlet_groups (list[str], optional): List of servlet groups to register.

synapse/handlers/auth.py

@@ -193,9 +193,7 @@ def __init__(self, hs: "HomeServer"):
         self.hs = hs  # FIXME better possibility to access registrationHandler later?
         self.macaroon_gen = hs.get_macaroon_generator()
         self._password_enabled = hs.config.password_enabled
-        self._sso_enabled = (
-            hs.config.cas_enabled or hs.config.saml2_enabled or hs.config.oidc_enabled
-        )
+        self._password_localdb_enabled = hs.config.password_localdb_enabled
 
         # we keep this as a list despite the O(N^2) implication so that we can
         # keep PASSWORD first and avoid confusing clients which pick the first
@@ -205,7 +203,7 @@ def __init__(self, hs: "HomeServer"):
 
         # start out by assuming PASSWORD is enabled; we will remove it later if not.
         login_types = []
-        if hs.config.password_localdb_enabled:
+        if self._password_localdb_enabled:
             login_types.append(LoginType.PASSWORD)
 
         for provider in self.password_providers:
@@ -219,14 +217,6 @@ def __init__(self, hs: "HomeServer"):
 
         self._supported_login_types = login_types
 
-        # Login types and UI Auth types have a heavy overlap, but are not
-        # necessarily identical. Login types have SSO (and other login types)
-        # added in the rest layer, see synapse.rest.client.v1.login.LoginRestServerlet.on_GET.
-        ui_auth_types = login_types.copy()
-        if self._sso_enabled:
-            ui_auth_types.append(LoginType.SSO)
-        self._supported_ui_auth_types = ui_auth_types
-
         # Ratelimiter for failed auth during UIA. Uses same ratelimit config
         # as per `rc_login.failed_attempts`.
         self._failed_uia_attempts_ratelimiter = Ratelimiter(
@@ -339,7 +329,10 @@ async def validate_user_via_ui_auth(
         self._failed_uia_attempts_ratelimiter.ratelimit(user_id, update=False)
 
         # build a list of supported flows
-        flows = [[login_type] for login_type in self._supported_ui_auth_types]
+        supported_ui_auth_types = await self._get_available_ui_auth_types(
+            requester.user
+        )
+        flows = [[login_type] for login_type in supported_ui_auth_types]
 
         try:
             result, params, session_id = await self.check_ui_auth(
@@ -351,7 +344,7 @@ async def validate_user_via_ui_auth(
             raise
 
         # find the completed login type
-        for login_type in self._supported_ui_auth_types:
+        for login_type in supported_ui_auth_types:
             if login_type not in result:
                 continue
 
@@ -367,6 +360,41 @@ async def validate_user_via_ui_auth(
 
         return params, session_id
 
+    async def _get_available_ui_auth_types(self, user: UserID) -> Iterable[str]:
+        """Get a list of the authentication types this user can use
+        """
+
+        ui_auth_types = set()
+
+        # if the HS supports password auth, and the user has a non-null password, we
+        # support password auth
+        if self._password_localdb_enabled and self._password_enabled:
+            lookupres = await self._find_user_id_and_pwd_hash(user.to_string())
+            if lookupres:
+                _, password_hash = lookupres
+                if password_hash:
+                    ui_auth_types.add(LoginType.PASSWORD)
+
+        # also allow auth from password providers
+        for provider in self.password_providers:
+            for t in provider.get_supported_login_types().keys():
+                if t == LoginType.PASSWORD and not self._password_enabled:
+                    continue
+                ui_auth_types.add(t)
+
+        # if sso is enabled, allow the user to log in via SSO iff they have a mapping
+        # from sso to mxid.
+        if self.hs.config.saml2.saml2_enabled or self.hs.config.oidc.oidc_enabled:
+            if await self.store.get_external_ids_by_user(user.to_string()):
+                ui_auth_types.add(LoginType.SSO)
+
+        # Our CAS impl does not (yet) correctly register users in user_external_ids,
+        # so always offer that if it's available.
+        if self.hs.config.cas.cas_enabled:
+            ui_auth_types.add(LoginType.SSO)
+
+        return ui_auth_types
+
     def get_enabled_auth_types(self):
         """Return the enabled user-interactive authentication types
 
@@ -1029,7 +1057,7 @@ async def _validate_userid_login(
             if result:
                 return result
 
-        if login_type == LoginType.PASSWORD and self.hs.config.password_localdb_enabled:
+        if login_type == LoginType.PASSWORD and self._password_localdb_enabled:
             known_login_type = True
 
             # we've already checked that there is a (valid) password field

synapse/storage/databases/main/registration.py

@@ -463,6 +463,23 @@ async def get_user_by_external_id(
             desc="get_user_by_external_id",
         )
 
+    async def get_external_ids_by_user(self, mxid: str) -> List[Tuple[str, str]]:
+        """Look up external ids for the given user
+
+        Args:
+            mxid: the MXID to be looked up
+
+        Returns:
+            Tuples of (auth_provider, external_id)
+        """
+        res = await self.db_pool.simple_select_list(
+            table="user_external_ids",
+            keyvalues={"user_id": mxid},
+            retcols=("auth_provider", "external_id"),
+            desc="get_external_ids_by_user",
+        )
+        return [(r["auth_provider"], r["external_id"]) for r in res]
+
     async def count_all_users(self):
         """Counts all users registered on the homeserver."""
 
@@ -963,6 +980,14 @@ def __init__(self, database: DatabasePool, db_conn: Connection, hs: "HomeServer"
             "users_set_deactivated_flag", self._background_update_set_deactivated_flag
         )
 
+        self.db_pool.updates.register_background_index_update(
+            "user_external_ids_user_id_idx",
+            index_name="user_external_ids_user_id_idx",
+            table="user_external_ids",
+            columns=["user_id"],
+            unique=False,
+        )
+
     async def _background_update_set_deactivated_flag(self, progress, batch_size):
         """Retrieves a list of all deactivated users and sets the 'deactivated' flag to 1
         for each of them.

synapse/storage/databases/main/schema/delta/58/25user_external_ids_user_id_idx.sql

@@ -0,0 +1,17 @@
+/* Copyright 2020 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
+  (5825, 'user_external_ids_user_id_idx', '{}');

tests/handlers/test_oidc.py

@@ -17,30 +17,15 @@
 
 from mock import Mock, patch
 
-import attr
 import pymacaroons
 
-from twisted.python.failure import Failure
-from twisted.web._newclient import ResponseDone
-
 from synapse.handlers.oidc_handler import OidcError, OidcMappingProvider
 from synapse.handlers.sso import MappingException
 from synapse.types import UserID
 
+from tests.test_utils import FakeResponse
 from tests.unittest import HomeserverTestCase, override_config
 
-
-@attr.s
-class FakeResponse:
-    code = attr.ib()
-    body = attr.ib()
-    phrase = attr.ib()
-
-    def deliverBody(self, protocol):
-        protocol.dataReceived(self.body)
-        protocol.connectionLost(Failure(ResponseDone()))
-
-
 # These are a few constants that are used as config parameters in the tests.
 ISSUER = "https://issuer/"
 CLIENT_ID = "test-client-id"

tests/handlers/test_typing.py

@@ -15,18 +15,20 @@
 
 
 import json
+from typing import Dict
 
 from mock import ANY, Mock, call
 
 from twisted.internet import defer
+from twisted.web.resource import Resource
 
 from synapse.api.errors import AuthError
+from synapse.federation.transport.server import TransportLayerServer
 from synapse.types import UserID, create_requester
 
 from tests import unittest
 from tests.test_utils import make_awaitable
 from tests.unittest import override_config
-from tests.utils import register_federation_servlets
 
 # Some local users to test with
 U_APPLE = UserID.from_string("@apple:test")
@@ -53,8 +55,6 @@ def _make_edu_transaction_json(edu_type, content):
 
 
 class TypingNotificationsTestCase(unittest.HomeserverTestCase):
-    servlets = [register_federation_servlets]
-
     def make_homeserver(self, reactor, clock):
         # we mock out the keyring so as to skip the authentication check on the
         # federation API call.
@@ -77,6 +77,11 @@ def make_homeserver(self, reactor, clock):
 
         return hs
 
+    def create_resource_dict(self) -> Dict[str, Resource]:
+        d = super().create_resource_dict()
+        d["/_matrix/federation"] = TransportLayerServer(self.hs)
+        return d
+
     def prepare(self, reactor, clock, hs):
         mock_notifier = hs.get_notifier()
         self.on_new_event = mock_notifier.on_new_event

tests/replication/_base.py

@@ -13,22 +13,23 @@
 # See the License for the specific language governing permissions and
 # limitations under the License.
 import logging
-from typing import Any, Callable, List, Optional, Tuple
+from typing import Any, Callable, Dict, List, Optional, Tuple
 
 import attr
 
 from twisted.internet.interfaces import IConsumer, IPullProducer, IReactorTime
 from twisted.internet.protocol import Protocol
 from twisted.internet.task import LoopingCall
 from twisted.web.http import HTTPChannel
+from twisted.web.resource import Resource
 
 from synapse.app.generic_worker import (
     GenericWorkerReplicationHandler,
     GenericWorkerServer,
 )
 from synapse.http.server import JsonResource
 from synapse.http.site import SynapseRequest, SynapseSite
-from synapse.replication.http import ReplicationRestResource, streams
+from synapse.replication.http import ReplicationRestResource
 from synapse.replication.tcp.handler import ReplicationCommandHandler
 from synapse.replication.tcp.protocol import ClientReplicationStreamProtocol
 from synapse.replication.tcp.resource import ReplicationStreamProtocolFactory
@@ -54,10 +55,6 @@ class BaseStreamTestCase(unittest.HomeserverTestCase):
     if not hiredis:
         skip = "Requires hiredis"
 
-    servlets = [
-        streams.register_servlets,
-    ]
-
     def prepare(self, reactor, clock, hs):
         # build a replication server
         server_factory = ReplicationStreamProtocolFactory(hs)
@@ -88,6 +85,11 @@ def prepare(self, reactor, clock, hs):
         self._client_transport = None
         self._server_transport = None
 
+    def create_resource_dict(self) -> Dict[str, Resource]:
+        d = super().create_resource_dict()
+        d["/_synapse/replication"] = ReplicationRestResource(self.hs)
+        return d
+
     def _get_worker_hs_config(self) -> dict:
         config = self.default_config()
         config["worker_app"] = "synapse.app.generic_worker"