fix: Don't try to sign events that don't originate from us

src/api/server/make_leave.rs

@@ -1,5 +1,5 @@
 use axum::extract::State;
-use conduwuit::{Err, Result, info, matrix::pdu::PduBuilder};
+use conduwuit::{Err, Result, info, matrix::pdu::PduBuilder, utils};
 use ruma::{
 	api::federation::membership::prepare_leave_event,
 	events::room::member::{MembershipState, RoomMemberEventContent},
@@ -49,10 +49,10 @@ pub(crate) async fn create_leave_event_template_route(
 	let room_version_id = services.rooms.state.get_room_version(&body.room_id).await?;
 	let state_lock = services.rooms.state.mutex.lock(&body.room_id).await;
 
-	let (_pdu, mut pdu_json) = services
+	let (pdu, _) = services
 		.rooms
 		.timeline
-		.create_hash_and_sign_event(
+		.create_event(
 			PduBuilder::state(
 				body.user_id.to_string(),
 				&RoomMemberEventContent::new(MembershipState::Leave),
@@ -64,9 +64,9 @@ pub(crate) async fn create_leave_event_template_route(
 		.await?;
 
 	drop(state_lock);
-
-	// room v3 and above removed the "event_id" field from remote PDU format
-	maybe_strip_event_id(&mut pdu_json, &room_version_id)?;
+	let mut pdu_json = utils::to_canonical_object(&pdu)
+		.expect("Barebones PDU should be convertible to canonical JSON");
+	pdu_json.remove("event_id");
 
 	Ok(prepare_leave_event::v1::Response {
 		room_version: Some(room_version_id),