feat: Support MSC4494

Cargo.toml

@@ -383,6 +383,7 @@ features = [
     "unstable-msc4354",
     "unstable-msc4480",
     "unstable-msc4466",
+    "unstable-msc4494",
     "unstable-extensible-events",
 ]
 

src/core/matrix/versions.rs

@@ -46,5 +46,7 @@ pub fn unstable_features() -> BTreeMap<String, bool> {
 		("computer.gingershaped.msc4466".to_owned(), true),
 		// web push (https://github.com/matrix-org/matrix-spec-proposals/pull/4174)
 		("org.matrix.msc4174".to_owned(), true),
+		// Membership-based invite blocking (https://github.com/matrix-org/matrix-spec-proposals/pull/4494)
+		("uk.timedout.msc4494".to_owned(), true),
 	])
 }

src/service/users/account.rs

@@ -4,7 +4,7 @@
 };
 
 use conduwuit::{
-	Err, Result, debug_error, debug_warn, err, error, info, trace,
+	Err, Result, debug, debug_error, debug_warn, err, error, info, trace,
 	utils::{self, stream::TryIgnore},
 	warn,
 };
@@ -16,10 +16,12 @@
 	api::client::profile::PropagateTo,
 	events::{
 		GlobalAccountDataEventType, ignored_user_list::IgnoredUserListEvent,
-		push_rules::PushRulesEvent, room::message::RoomMessageEventContent,
+		invite_permission_config::InvitePermissionAction, push_rules::PushRulesEvent,
+		room::message::RoomMessageEventContent,
 	},
 	profile::ProfileFieldValue,
 	push::Ruleset,
+	room::JoinRule,
 };
 use ruminuwuity::invite_permission_config::{FilterLevel, InvitePermissionConfigEvent};
 
@@ -105,13 +107,47 @@ pub async fn invite_filter_level(
 			if stable.is_err() && unstable.is_err() {
 				return FilterLevel::Allow;
 			}
-			stable
-				.unwrap_or_else(|_| unstable.unwrap())
-				.content
-				.user_filter_level(sender_user)
+			let content = stable.unwrap_or_else(|_| unstable.unwrap()).content;
+			let verdict = content.user_filter_level(sender_user);
+			if verdict != FilterLevel::Allow {
+				return verdict;
+			}
+			// Apply other layers of invite blocking first, so that user/server
+			// denies take priority over implicit allows.
+			if content.default_action != Some(InvitePermissionAction::DenyPublic)
+				&& self
+					.check_msc4494_mutual_room(sender_user, recipient_user)
+					.await
+			{
+				FilterLevel::Block
+			} else {
+				FilterLevel::Allow
+			}
 		}
 	}
 
+	/// Checks that sender and recipient share at least one rule that has a join
+	/// rule other than `public`.
+	async fn check_msc4494_mutual_room(&self, sender: &UserId, recipient: &UserId) -> bool {
+		let mut mutual_rooms = std::pin::pin!(
+			self.services
+				.state_cache
+				.get_shared_rooms(sender, recipient)
+		);
+		while let Some(room_id) = mutual_rooms.next().await {
+			if self.services.state_accessor.get_join_rules(&room_id).await != JoinRule::Public {
+				debug!(
+					%sender,
+					%recipient,
+					%room_id,
+					"Sender and recipient share a non-public room"
+				);
+				return true;
+			}
+		}
+		false
+	}
+
 	/// Check if a user is an admin
 	#[inline]
 	pub async fn is_admin(&self, user_id: &UserId) -> bool {