Move methods involving event authentication to EventAuthHandler. (#10268)

Instead of mixing them with user authentication methods.

Author: clokep

changelog.d/10268.misc

@@ -0,0 +1 @@
+Move event authentication methods from `Auth` to `EventAuthHandler`.

synapse/api/auth.py

@@ -12,7 +12,7 @@
 # See the License for the specific language governing permissions and
 # limitations under the License.
 import logging
-from typing import TYPE_CHECKING, Any, Dict, List, Optional, Tuple, Union
+from typing import TYPE_CHECKING, Optional, Tuple
 
 import pymacaroons
 from netaddr import IPAddress
@@ -28,34 +28,22 @@
     InvalidClientTokenError,
     MissingClientTokenError,
 )
-from synapse.api.room_versions import KNOWN_ROOM_VERSIONS
 from synapse.appservice import ApplicationService
 from synapse.events import EventBase
-from synapse.events.builder import EventBuilder
 from synapse.http import get_request_user_agent
 from synapse.http.site import SynapseRequest
 from synapse.logging import opentracing as opentracing
 from synapse.storage.databases.main.registration import TokenLookupResult
 from synapse.types import Requester, StateMap, UserID, create_requester
 from synapse.util.caches.lrucache import LruCache
 from synapse.util.macaroons import get_value_from_macaroon, satisfy_expiry
-from synapse.util.metrics import Measure
 
 if TYPE_CHECKING:
     from synapse.server import HomeServer
 
 logger = logging.getLogger(__name__)
 
 
-AuthEventTypes = (
-    EventTypes.Create,
-    EventTypes.Member,
-    EventTypes.PowerLevels,
-    EventTypes.JoinRules,
-    EventTypes.RoomHistoryVisibility,
-    EventTypes.ThirdPartyInvite,
-)
-
 # guests always get this device id.
 GUEST_DEVICE_ID = "guest_device"
 
@@ -66,9 +54,7 @@ class _InvalidMacaroonException(Exception):
 
 class Auth:
     """
-    FIXME: This class contains a mix of functions for authenticating users
-    of our client-server API and authenticating events added to room graphs.
-    The latter should be moved to synapse.handlers.event_auth.EventAuthHandler.
+    This class contains functions for authenticating users of our client-server API.
     """
 
     def __init__(self, hs: "HomeServer"):
@@ -90,18 +76,6 @@ def __init__(self, hs: "HomeServer"):
         self._macaroon_secret_key = hs.config.macaroon_secret_key
         self._force_tracing_for_users = hs.config.tracing.force_tracing_for_users
 
-    async def check_from_context(
-        self, room_version: str, event, context, do_sig_check=True
-    ) -> None:
-        auth_event_ids = event.auth_event_ids()
-        auth_events_by_id = await self.store.get_events(auth_event_ids)
-        auth_events = {(e.type, e.state_key): e for e in auth_events_by_id.values()}
-
-        room_version_obj = KNOWN_ROOM_VERSIONS[room_version]
-        event_auth.check(
-            room_version_obj, event, auth_events=auth_events, do_sig_check=do_sig_check
-        )
-
     async def check_user_in_room(
         self,
         room_id: str,
@@ -152,13 +126,6 @@ async def check_user_in_room(
 
         raise AuthError(403, "User %s not in room %s" % (user_id, room_id))
 
-    async def check_host_in_room(self, room_id: str, host: str) -> bool:
-        with Measure(self.clock, "check_host_in_room"):
-            return await self.store.is_host_joined(room_id, host)
-
-    def get_public_keys(self, invite_event: EventBase) -> List[Dict[str, Any]]:
-        return event_auth.get_public_keys(invite_event)
-
     async def get_user_by_req(
         self,
         request: SynapseRequest,
@@ -489,44 +456,6 @@ async def is_server_admin(self, user: UserID) -> bool:
         """
         return await self.store.is_server_admin(user)
 
-    def compute_auth_events(
-        self,
-        event: Union[EventBase, EventBuilder],
-        current_state_ids: StateMap[str],
-        for_verification: bool = False,
-    ) -> List[str]:
-        """Given an event and current state return the list of event IDs used
-        to auth an event.
-
-        If `for_verification` is False then only return auth events that
-        should be added to the event's `auth_events`.
-
-        Returns:
-            List of event IDs.
-        """
-
-        if event.type == EventTypes.Create:
-            return []
-
-        # Currently we ignore the `for_verification` flag even though there are
-        # some situations where we can drop particular auth events when adding
-        # to the event's `auth_events` (e.g. joins pointing to previous joins
-        # when room is publicly joinable). Dropping event IDs has the
-        # advantage that the auth chain for the room grows slower, but we use
-        # the auth chain in state resolution v2 to order events, which means
-        # care must be taken if dropping events to ensure that it doesn't
-        # introduce undesirable "state reset" behaviour.
-        #
-        # All of which sounds a bit tricky so we don't bother for now.
-
-        auth_ids = []
-        for etype, state_key in event_auth.auth_types_for_event(event):
-            auth_ev_id = current_state_ids.get((etype, state_key))
-            if auth_ev_id:
-                auth_ids.append(auth_ev_id)
-
-        return auth_ids
-
     async def check_can_change_room_list(self, room_id: str, user: UserID) -> bool:
         """Determine whether the user is allowed to edit the room's entry in the
         published room list.

synapse/events/builder.py

@@ -34,7 +34,7 @@
 from synapse.util.stringutils import random_string
 
 if TYPE_CHECKING:
-    from synapse.api.auth import Auth
+    from synapse.handlers.event_auth import EventAuthHandler
     from synapse.server import HomeServer
 
 logger = logging.getLogger(__name__)
@@ -66,7 +66,7 @@ class EventBuilder:
     """
 
     _state: StateHandler
-    _auth: "Auth"
+    _event_auth_handler: "EventAuthHandler"
     _store: DataStore
     _clock: Clock
     _hostname: str
@@ -125,7 +125,9 @@ async def build(
             state_ids = await self._state.get_current_state_ids(
                 self.room_id, prev_event_ids
             )
-            auth_event_ids = self._auth.compute_auth_events(self, state_ids)
+            auth_event_ids = self._event_auth_handler.compute_auth_events(
+                self, state_ids
+            )
 
         format_version = self.room_version.event_format
         if format_version == EventFormatVersions.V1:
@@ -193,7 +195,7 @@ def __init__(self, hs: "HomeServer"):
 
         self.store = hs.get_datastore()
         self.state = hs.get_state_handler()
-        self.auth = hs.get_auth()
+        self._event_auth_handler = hs.get_event_auth_handler()
 
     def new(self, room_version: str, key_values: dict) -> EventBuilder:
         """Generate an event builder appropriate for the given room version
@@ -229,7 +231,7 @@ def for_room_version(
         return EventBuilder(
             store=self.store,
             state=self.state,
-            auth=self.auth,
+            event_auth_handler=self._event_auth_handler,
             clock=self.clock,
             hostname=self.hostname,
             signing_key=self.signing_key,

synapse/federation/federation_server.py

@@ -108,9 +108,9 @@ class FederationServer(FederationBase):
     def __init__(self, hs: "HomeServer"):
         super().__init__(hs)
 
-        self.auth = hs.get_auth()
         self.handler = hs.get_federation_handler()
         self.state = hs.get_state_handler()
+        self._event_auth_handler = hs.get_event_auth_handler()
 
         self.device_handler = hs.get_device_handler()
 
@@ -420,7 +420,7 @@ async def on_room_state_request(
         origin_host, _ = parse_server_name(origin)
         await self.check_server_matches_acl(origin_host, room_id)
 
-        in_room = await self.auth.check_host_in_room(room_id, origin)
+        in_room = await self._event_auth_handler.check_host_in_room(room_id, origin)
         if not in_room:
             raise AuthError(403, "Host not in room.")
 
@@ -453,7 +453,7 @@ async def on_state_ids_request(
         origin_host, _ = parse_server_name(origin)
         await self.check_server_matches_acl(origin_host, room_id)
 
-        in_room = await self.auth.check_host_in_room(room_id, origin)
+        in_room = await self._event_auth_handler.check_host_in_room(room_id, origin)
         if not in_room:
             raise AuthError(403, "Host not in room.")
 

synapse/handlers/event_auth.py

@@ -11,18 +11,21 @@
 # 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 TYPE_CHECKING, Collection, Optional
+from typing import TYPE_CHECKING, Collection, List, Optional, Union
 
+from synapse import event_auth
 from synapse.api.constants import (
     EventTypes,
     JoinRules,
     Membership,
     RestrictedJoinRuleTypes,
 )
 from synapse.api.errors import AuthError
-from synapse.api.room_versions import RoomVersion
+from synapse.api.room_versions import KNOWN_ROOM_VERSIONS, RoomVersion
 from synapse.events import EventBase
+from synapse.events.builder import EventBuilder
 from synapse.types import StateMap
+from synapse.util.metrics import Measure
 
 if TYPE_CHECKING:
     from synapse.server import HomeServer
@@ -34,8 +37,63 @@ class EventAuthHandler:
     """
 
     def __init__(self, hs: "HomeServer"):
+        self._clock = hs.get_clock()
         self._store = hs.get_datastore()
 
+    async def check_from_context(
+        self, room_version: str, event, context, do_sig_check=True
+    ) -> None:
+        auth_event_ids = event.auth_event_ids()
+        auth_events_by_id = await self._store.get_events(auth_event_ids)
+        auth_events = {(e.type, e.state_key): e for e in auth_events_by_id.values()}
+
+        room_version_obj = KNOWN_ROOM_VERSIONS[room_version]
+        event_auth.check(
+            room_version_obj, event, auth_events=auth_events, do_sig_check=do_sig_check
+        )
+
+    def compute_auth_events(
+        self,
+        event: Union[EventBase, EventBuilder],
+        current_state_ids: StateMap[str],
+        for_verification: bool = False,
+    ) -> List[str]:
+        """Given an event and current state return the list of event IDs used
+        to auth an event.
+
+        If `for_verification` is False then only return auth events that
+        should be added to the event's `auth_events`.
+
+        Returns:
+            List of event IDs.
+        """
+
+        if event.type == EventTypes.Create:
+            return []
+
+        # Currently we ignore the `for_verification` flag even though there are
+        # some situations where we can drop particular auth events when adding
+        # to the event's `auth_events` (e.g. joins pointing to previous joins
+        # when room is publicly joinable). Dropping event IDs has the
+        # advantage that the auth chain for the room grows slower, but we use
+        # the auth chain in state resolution v2 to order events, which means
+        # care must be taken if dropping events to ensure that it doesn't
+        # introduce undesirable "state reset" behaviour.
+        #
+        # All of which sounds a bit tricky so we don't bother for now.
+
+        auth_ids = []
+        for etype, state_key in event_auth.auth_types_for_event(event):
+            auth_ev_id = current_state_ids.get((etype, state_key))
+            if auth_ev_id:
+                auth_ids.append(auth_ev_id)
+
+        return auth_ids
+
+    async def check_host_in_room(self, room_id: str, host: str) -> bool:
+        with Measure(self._clock, "check_host_in_room"):
+            return await self._store.is_host_joined(room_id, host)
+
     async def check_restricted_join_rules(
         self,
         state_ids: StateMap[str],