Add support for MSC4155 Invite filtering (#18288)

Half-Shot · anoadragon453 · web-flow · commit 8010377a8849 · 2025-06-05T11:49:09.000+01:00
This implements matrix-org/matrix-spec-proposals#4155, which adds support for a new account data type that blocks an invite based on some conditions in the event contents. --------- Co-authored-by: Andrew Morgan <1342360+anoadragon453@users.noreply.github.com>
diff --git a/changelog.d/18288.feature b/changelog.d/18288.feature
@@ -0,0 +1 @@
+Add support for [MSC4155](https://github.com/matrix-org/matrix-spec-proposals/pull/4155) Invite Filtering.
diff --git a/docker/complement/conf/workers-shared-extra.yaml.j2 b/docker/complement/conf/workers-shared-extra.yaml.j2
@@ -127,6 +127,8 @@ experimental_features:
   msc3983_appservice_otk_claims: true
   # Proxy key queries to exclusive ASes
   msc3984_appservice_key_query: true
+  # Invite filtering
+  msc4155_enabled: true
 
 server_notices:
   system_mxid_localpart: _server
diff --git a/scripts-dev/complement.sh b/scripts-dev/complement.sh
@@ -229,6 +229,7 @@ test_packages=(
     ./tests/msc3902
     ./tests/msc3967
     ./tests/msc4140
+    ./tests/msc4155
 )
 
 # Enable dirty runs, so tests will reuse the same container where possible.
diff --git a/synapse/api/constants.py b/synapse/api/constants.py
@@ -286,6 +286,10 @@ class AccountDataTypes:
     IGNORED_USER_LIST: Final = "m.ignored_user_list"
     TAG: Final = "m.tag"
     PUSH_RULES: Final = "m.push_rules"
+    # MSC4155: Invite filtering
+    MSC4155_INVITE_PERMISSION_CONFIG: Final = (
+        "org.matrix.msc4155.invite_permission_config"
+    )
 
 
 class HistoryVisibility:
diff --git a/synapse/api/errors.py b/synapse/api/errors.py
@@ -137,6 +137,9 @@ class Codes(str, Enum):
     PROFILE_TOO_LARGE = "M_PROFILE_TOO_LARGE"
     KEY_TOO_LARGE = "M_KEY_TOO_LARGE"
 
+    # Part of MSC4155
+    INVITE_BLOCKED = "ORG.MATRIX.MSC4155.M_INVITE_BLOCKED"
+
 
 class CodeMessageException(RuntimeError):
     """An exception with integer code, a message string attributes and optional headers.
diff --git a/synapse/config/experimental.py b/synapse/config/experimental.py
@@ -566,3 +566,6 @@ def read_config(
             "msc4263_limit_key_queries_to_users_who_share_rooms",
             False,
         )
+
+        # MSC4155: Invite filtering
+        self.msc4155_enabled: bool = experimental.get("msc4155_enabled", False)
diff --git a/synapse/handlers/federation.py b/synapse/handlers/federation.py
@@ -78,6 +78,7 @@
     ReplicationStoreRoomOnOutlierMembershipRestServlet,
 )
 from synapse.storage.databases.main.events_worker import EventRedactBehaviour
+from synapse.storage.invite_rule import InviteRule
 from synapse.types import JsonDict, StrCollection, get_domain_from_id
 from synapse.types.state import StateFilter
 from synapse.util.async_helpers import Linearizer
@@ -1089,6 +1090,20 @@ async def on_invite_request(
         if event.state_key == self._server_notices_mxid:
             raise SynapseError(HTTPStatus.FORBIDDEN, "Cannot invite this user")
 
+        # check the invitee's configuration and apply rules
+        invite_config = await self.store.get_invite_config_for_user(event.state_key)
+        rule = invite_config.get_invite_rule(event.sender)
+        if rule == InviteRule.BLOCK:
+            logger.info(
+                f"Automatically rejecting invite from {event.sender} due to the invite filtering rules of {event.state_key}"
+            )
+            raise SynapseError(
+                403,
+                "You are not permitted to invite this user.",
+                errcode=Codes.INVITE_BLOCKED,
+            )
+        # InviteRule.IGNORE is handled at the sync layer
+
         # We retrieve the room member handler here as to not cause a cyclic dependency
         member_handler = self.hs.get_room_member_handler()
         # We don't rate limit based on room ID, as that should be done by
diff --git a/synapse/handlers/room_member.py b/synapse/handlers/room_member.py
@@ -53,6 +53,7 @@
 from synapse.metrics.background_process_metrics import run_as_background_process
 from synapse.replication.http.push import ReplicationCopyPusherRestServlet
 from synapse.storage.databases.main.state_deltas import StateDelta
+from synapse.storage.invite_rule import InviteRule
 from synapse.types import (
     JsonDict,
     Requester,
@@ -915,6 +916,21 @@ async def update_membership_locked(
                     additional_fields=block_invite_result[1],
                 )
 
+            # check the invitee's configuration and apply rules. Admins on the server can bypass.
+            if not is_requester_admin:
+                invite_config = await self.store.get_invite_config_for_user(target_id)
+                rule = invite_config.get_invite_rule(requester.user.to_string())
+                if rule == InviteRule.BLOCK:
+                    logger.info(
+                        f"Automatically rejecting invite from {target_id} due to the the invite filtering rules of {requester.user}"
+                    )
+                    raise SynapseError(
+                        403,
+                        "You are not permitted to invite this user.",
+                        errcode=Codes.INVITE_BLOCKED,
+                    )
+                # InviteRule.IGNORE is handled at the sync layer.
+
         # An empty prev_events list is allowed as long as the auth_event_ids are present
         if prev_event_ids is not None:
             return await self._local_membership_update(
diff --git a/synapse/handlers/sliding_sync/room_lists.py b/synapse/handlers/sliding_sync/room_lists.py
@@ -49,6 +49,7 @@
     Sentinel as StateSentinel,
 )
 from synapse.storage.databases.main.stream import CurrentStateDeltaMembership
+from synapse.storage.invite_rule import InviteRule
 from synapse.storage.roommember import (
     RoomsForUser,
     RoomsForUserSlidingSync,
@@ -278,6 +279,7 @@ async def _compute_interested_rooms_new_tables(
 
         # Remove invites from ignored users
         ignored_users = await self.store.ignored_users(user_id)
+        invite_config = await self.store.get_invite_config_for_user(user_id)
         if ignored_users:
             # FIXME: It would be nice to avoid this copy but since
             # `get_sliding_sync_rooms_for_user_from_membership_snapshots` is cached, it
@@ -292,7 +294,14 @@ async def _compute_interested_rooms_new_tables(
                 room_for_user_sliding_sync = room_membership_for_user_map[room_id]
                 if (
                     room_for_user_sliding_sync.membership == Membership.INVITE
-                    and room_for_user_sliding_sync.sender in ignored_users
+                    and room_for_user_sliding_sync.sender
+                    and (
+                        room_for_user_sliding_sync.sender in ignored_users
+                        or invite_config.get_invite_rule(
+                            room_for_user_sliding_sync.sender
+                        )
+                        == InviteRule.IGNORE
+                    )
                 ):
                     room_membership_for_user_map.pop(room_id, None)
 
diff --git a/synapse/handlers/sync.py b/synapse/handlers/sync.py
@@ -66,6 +66,7 @@
 from synapse.storage.databases.main.event_push_actions import RoomNotifCounts
 from synapse.storage.databases.main.roommember import extract_heroes_from_room_summary
 from synapse.storage.databases.main.stream import PaginateFunction
+from synapse.storage.invite_rule import InviteRule
 from synapse.storage.roommember import MemberSummary
 from synapse.types import (
     DeviceListUpdates,
@@ -2549,6 +2550,7 @@ async def _get_room_changes_for_incremental_sync(
         room_entries: List[RoomSyncResultBuilder] = []
         invited: List[InvitedSyncResult] = []
         knocked: List[KnockedSyncResult] = []
+        invite_config = await self.store.get_invite_config_for_user(user_id)
         for room_id, events in mem_change_events_by_room_id.items():
             # The body of this loop will add this room to at least one of the five lists
             # above. Things get messy if you've e.g. joined, left, joined then left the
@@ -2631,7 +2633,11 @@ async def _get_room_changes_for_incremental_sync(
             # Only bother if we're still currently invited
             should_invite = last_non_join.membership == Membership.INVITE
             if should_invite:
-                if last_non_join.sender not in ignored_users:
+                if (
+                    last_non_join.sender not in ignored_users
+                    and invite_config.get_invite_rule(last_non_join.sender)
+                    != InviteRule.IGNORE
+                ):
                     invite_room_sync = InvitedSyncResult(room_id, invite=last_non_join)
                     if invite_room_sync:
                         invited.append(invite_room_sync)
@@ -2786,6 +2792,7 @@ async def _get_room_changes_for_initial_sync(
             membership_list=Membership.LIST,
             excluded_rooms=sync_result_builder.excluded_room_ids,
         )
+        invite_config = await self.store.get_invite_config_for_user(user_id)
 
         room_entries = []
         invited = []
@@ -2811,6 +2818,8 @@ async def _get_room_changes_for_initial_sync(
             elif event.membership == Membership.INVITE:
                 if event.sender in ignored_users:
                     continue
+                if invite_config.get_invite_rule(event.sender) == InviteRule.IGNORE:
+                    continue
                 invite = await self.store.get_event(event.event_id)
                 invited.append(InvitedSyncResult(room_id=event.room_id, invite=invite))
             elif event.membership == Membership.KNOCK:
diff --git a/synapse/push/bulk_push_rule_evaluator.py b/synapse/push/bulk_push_rule_evaluator.py
@@ -52,6 +52,7 @@
 from synapse.logging.context import make_deferred_yieldable, run_in_background
 from synapse.state import POWER_KEY
 from synapse.storage.databases.main.roommember import EventIdMembership
+from synapse.storage.invite_rule import InviteRule
 from synapse.storage.roommember import ProfileInfo
 from synapse.synapse_rust.push import FilteredPushRules, PushRuleEvaluator
 from synapse.types import JsonValue
@@ -191,9 +192,17 @@ async def _get_rules_for_event(
 
         # if this event is an invite event, we may need to run rules for the user
         # who's been invited, otherwise they won't get told they've been invited
-        if event.type == EventTypes.Member and event.membership == Membership.INVITE:
+        if (
+            event.is_state()
+            and event.type == EventTypes.Member
+            and event.membership == Membership.INVITE
+        ):
             invited = event.state_key
-            if invited and self.hs.is_mine_id(invited) and invited not in local_users:
+            invite_config = await self.store.get_invite_config_for_user(invited)
+            if invite_config.get_invite_rule(event.sender) != InviteRule.ALLOW:
+                # Invite was blocked or ignored, never notify.
+                return {}
+            if self.hs.is_mine_id(invited) and invited not in local_users:
                 local_users.append(invited)
 
         if not local_users:
diff --git a/synapse/rest/client/versions.py b/synapse/rest/client/versions.py
@@ -174,6 +174,8 @@ async def on_GET(self, request: SynapseRequest) -> Tuple[int, JsonDict]:
                     "org.matrix.simplified_msc3575": msc3575_enabled,
                     # Arbitrary key-value profile fields.
                     "uk.tcpip.msc4133": self.config.experimental.msc4133_enabled,
+                    # MSC4155: Invite filtering
+                    "org.matrix.msc4155": self.config.experimental.msc4155_enabled,
                 },
             },
         )
diff --git a/synapse/storage/databases/main/account_data.py b/synapse/storage/databases/main/account_data.py
@@ -43,6 +43,7 @@
 )
 from synapse.storage.databases.main.cache import CacheInvalidationWorkerStore
 from synapse.storage.databases.main.push_rule import PushRulesWorkerStore
+from synapse.storage.invite_rule import InviteRulesConfig
 from synapse.storage.util.id_generators import MultiWriterIdGenerator
 from synapse.types import JsonDict, JsonMapping
 from synapse.util import json_encoder
@@ -102,6 +103,8 @@ def __init__(
             self._delete_account_data_for_deactivated_users,
         )
 
+        self._msc4155_enabled = hs.config.experimental.msc4155_enabled
+
     def get_max_account_data_stream_id(self) -> int:
         """Get the current max stream ID for account data stream
 
@@ -557,6 +560,23 @@ async def ignored_users(self, user_id: str) -> FrozenSet[str]:
             )
         )
 
+    async def get_invite_config_for_user(self, user_id: str) -> InviteRulesConfig:
+        """
+        Get the invite configuration for the current user.
+
+        Args:
+            user_id:
+        """
+
+        if not self._msc4155_enabled:
+            # This equates to allowing all invites, as if the setting was off.
+            return InviteRulesConfig(None)
+
+        data = await self.get_global_account_data_by_type_for_user(
+            user_id, AccountDataTypes.MSC4155_INVITE_PERMISSION_CONFIG
+        )
+        return InviteRulesConfig(data)
+
     def process_replication_rows(
         self,
         stream_name: str,
diff --git a/synapse/storage/databases/main/user_directory.py b/synapse/storage/databases/main/user_directory.py
@@ -43,6 +43,7 @@
 
     USE_ICU = True
 except ModuleNotFoundError:
+    # except ModuleNotFoundError:
     USE_ICU = False
 
 from synapse.api.errors import StoreError
diff --git a/synapse/storage/invite_rule.py b/synapse/storage/invite_rule.py
@@ -0,0 +1,110 @@
+import logging
+from enum import Enum
+from typing import Optional, Pattern
+
+from matrix_common.regex import glob_to_regex
+
+from synapse.types import JsonMapping, UserID
+
+logger = logging.getLogger(__name__)
+
+
+class InviteRule(Enum):
+    """Enum to define the action taken when an invite matches a rule."""
+
+    ALLOW = "allow"
+    BLOCK = "block"
+    IGNORE = "ignore"
+
+
+class InviteRulesConfig:
+    """Class to determine if a given user permits an invite from another user, and the action to take."""
+
+    def __init__(self, account_data: Optional[JsonMapping]):
+        self.allowed_users: list[Pattern[str]] = []
+        self.ignored_users: list[Pattern[str]] = []
+        self.blocked_users: list[Pattern[str]] = []
+
+        self.allowed_servers: list[Pattern[str]] = []
+        self.ignored_servers: list[Pattern[str]] = []
+        self.blocked_servers: list[Pattern[str]] = []
+
+        def process_field(
+            values: Optional[list[str]],
+            ruleset: list[Pattern[str]],
+            rule: InviteRule,
+        ) -> None:
+            if isinstance(values, list):
+                for value in values:
+                    if isinstance(value, str) and len(value) > 0:
+                        # User IDs cannot exceed 255 bytes. Don't process large, potentially
+                        # expensive glob patterns.
+                        if len(value) > 255:
+                            logger.debug(
+                                "Ignoring invite config glob pattern that is >255 bytes: {value}"
+                            )
+                            continue
+
+                        try:
+                            ruleset.append(glob_to_regex(value))
+                        except Exception as e:
+                            # If for whatever reason we can't process this, just ignore it.
+                            logger.debug(
+                                f"Could not process '{value}' field of invite rule config, ignoring: {e}"
+                            )
+
+        if account_data:
+            process_field(
+                account_data.get("allowed_users"), self.allowed_users, InviteRule.ALLOW
+            )
+            process_field(
+                account_data.get("ignored_users"), self.ignored_users, InviteRule.IGNORE
+            )
+            process_field(
+                account_data.get("blocked_users"), self.blocked_users, InviteRule.BLOCK
+            )
+            process_field(
+                account_data.get("allowed_servers"),
+                self.allowed_servers,
+                InviteRule.ALLOW,
+            )
+            process_field(
+                account_data.get("ignored_servers"),
+                self.ignored_servers,
+                InviteRule.IGNORE,
+            )
+            process_field(
+                account_data.get("blocked_servers"),
+                self.blocked_servers,
+                InviteRule.BLOCK,
+            )
+
+    def get_invite_rule(self, user_id: str) -> InviteRule:
+        """Get the invite rule that matches this user. Will return InviteRule.ALLOW if no rules match
+
+        Args:
+            user_id: The user ID of the inviting user.
+
+        """
+        user = UserID.from_string(user_id)
+        # The order here is important. We always process user rules before server rules
+        # and we always process in the order of Allow, Ignore, Block.
+        for patterns, rule in [
+            (self.allowed_users, InviteRule.ALLOW),
+            (self.ignored_users, InviteRule.IGNORE),
+            (self.blocked_users, InviteRule.BLOCK),
+        ]:
+            for regex in patterns:
+                if regex.match(user_id):
+                    return rule
+
+        for patterns, rule in [
+            (self.allowed_servers, InviteRule.ALLOW),
+            (self.ignored_servers, InviteRule.IGNORE),
+            (self.blocked_servers, InviteRule.BLOCK),
+        ]:
+            for regex in patterns:
+                if regex.match(user.domain):
+                    return rule
+
+        return InviteRule.ALLOW
diff --git a/tests/handlers/test_room_member.py b/tests/handlers/test_room_member.py
diff --git a/tests/storage/test_invite_rule.py b/tests/storage/test_invite_rule.py

Original file line number	Diff line number	Diff line change
`@@ -0,0 +1 @@`
	`1`	`+Add support for [MSC4155](https://github.com/matrix-org/matrix-spec-proposals/pull/4155) Invite Filtering.`
Original file line number	Diff line number	Diff line change
`@@ -229,6 +229,7 @@ test_packages=(`
`229`	`229`	`./tests/msc3902`
`230`	`230`	`./tests/msc3967`
`231`	`231`	`./tests/msc4140`
	`232`	`+ ./tests/msc4155`
`232`	`233`	`)`
`233`	`234`
`234`	`235`	`# Enable dirty runs, so tests will reuse the same container where possible.`
Original file line number	Diff line number	Diff line change
`@@ -566,3 +566,6 @@ def read_config(`
`566`	`566`	`"msc4263_limit_key_queries_to_users_who_share_rooms",`
`567`	`567`	`False,`
`568`	`568`	`)`
	`569`	`+`
	`570`	`+ # MSC4155: Invite filtering`
	`571`	`+ self.msc4155_enabled: bool = experimental.get("msc4155_enabled", False)`