Fix up failing sytest

roomserver/api/wrapper.go

@@ -122,15 +122,7 @@ func SendEventWithRewrite(
 		// We will handle an event as if it's an outlier if one of the
 		// following conditions is true:
 		storeAsOutlier := false
-		if authOrStateEvent.Type() == event.Type() && *authOrStateEvent.StateKey() == *event.StateKey() {
-			// The event is a state event but the input event is going to
-			// replace it, therefore it can't be added to the state or we'll
-			// get duplicate state keys in the state block. We'll send it
-			// as an outlier because we don't know if something will be
-			// referring to it as an auth event, but need it to be stored
-			// just in case.
-			storeAsOutlier = true
-		} else if _, ok := isCurrentState[authOrStateEvent.EventID()]; !ok {
+		if _, ok := isCurrentState[authOrStateEvent.EventID()]; !ok {
 			// The event is an auth event and isn't a part of the state set.
 			// We'll send it as an outlier because we need it to be stored
 			// in case something is referring to it as an auth event.

roomserver/internal/helpers/auth.go

@@ -32,7 +32,18 @@ func CheckForSoftFail(
 	ctx context.Context,
 	db storage.Database,
 	event gomatrixserverlib.HeaderedEvent,
+	stateEventIDs []string,
 ) (bool, error) {
+	rewritesState := len(stateEventIDs) > 1
+
+	var authStateEntries []types.StateEntry
+	var err error
+	if rewritesState {
+		authStateEntries, err = db.StateEntriesForEventIDs(ctx, stateEventIDs)
+		if err != nil {
+			return true, fmt.Errorf("StateEntriesForEventIDs failed: %w", err)
+		}
+	} else {
 		// Work out if the room exists.
 		roomInfo, err := db.RoomInfo(ctx, event.RoomID())
 		if err != nil {
@@ -42,19 +53,14 @@ func CheckForSoftFail(
 			return false, nil
 		}
 
-	// If the room exist, gets the current state snapshot.
-	_, stateSnapshotNID, _, err := db.LatestEventIDs(ctx, roomInfo.RoomNID)
-	if err != nil {
-		return true, fmt.Errorf("r.DB.LatestEventIDs: %w", err)
-	}
-
 		// Then get the state entries for the current state snapshot.
 		// We'll use this to check if the event is allowed right now.
 		roomState := state.NewStateResolution(db, *roomInfo)
-	authStateEntries, err := roomState.LoadStateAtSnapshot(ctx, stateSnapshotNID)
+		authStateEntries, err = roomState.LoadStateAtSnapshot(ctx, roomInfo.StateSnapshotNID)
 		if err != nil {
 			return true, fmt.Errorf("roomState.LoadStateAtSnapshot: %w", err)
 		}
+	}
 
 	// As a special case, it's possible that the room will have no
 	// state because we haven't received a m.room.create event yet.

roomserver/internal/input/input_events.go

@@ -43,7 +43,6 @@ func (r *Inputer) processRoomEvent(
 	// Parse and validate the event JSON
 	headered := input.Event
 	event := headered.Unwrap()
-	softfail := false
 
 	// Check that the event passes authentication checks and work out
 	// the numeric IDs for the auth events.
@@ -54,9 +53,11 @@ func (r *Inputer) processRoomEvent(
 		isRejected = true
 	}
 
+	var softfail bool
+	if input.Kind == api.KindBackfill || input.Kind == api.KindNew {
 		// Check that the event passes authentication checks based on the
 		// current room state.
-	softfail, err = helpers.CheckForSoftFail(ctx, r.DB, headered)
+		softfail, err = helpers.CheckForSoftFail(ctx, r.DB, headered, input.StateEventIDs)
 		if err != nil {
 			logrus.WithFields(logrus.Fields{
 				"event_id": event.EventID(),
@@ -64,6 +65,7 @@ func (r *Inputer) processRoomEvent(
 				"room":     event.RoomID(),
 			}).WithError(err).Info("Error authing soft-failed event")
 		}
+	}
 
 	// If we don't have a transaction ID then get one.
 	if input.TransactionID != nil {
@@ -100,6 +102,7 @@ func (r *Inputer) processRoomEvent(
 			"event_id": event.EventID(),
 			"type":     event.Type(),
 			"room":     event.RoomID(),
+			"sender":   event.Sender(),
 		}).Debug("Stored outlier")
 		return event.EventID(), nil
 	}
@@ -128,6 +131,7 @@ func (r *Inputer) processRoomEvent(
 			"type":      event.Type(),
 			"room":      event.RoomID(),
 			"soft_fail": softfail,
+			"sender":    event.Sender(),
 		}).Debug("Stored rejected event")
 		return event.EventID(), rejectionErr
 	}

sytest-blacklist

@@ -53,6 +53,3 @@ Outbound federation requests missing prev_events and then asks for /state_ids an
 
 # We don't implement lazy membership loading yet.
 The only membership state included in a gapped incremental sync is for senders in the timeline
-
-# flakey since implementing rejected events
-Inbound federation correctly soft fails events

sytest-whitelist

@@ -473,3 +473,5 @@ Local users can peek by room alias
 Peeked rooms only turn up in the sync for the device who peeked them
 Room state at a rejected message event is the same as its predecessor
 Room state at a rejected state event is the same as its predecessor
+Inbound federation correctly soft fails events
+Inbound federation accepts a second soft-failed event