Finish implementing redactions (#1189)

* Add a bit more logging to the fedsender

* bugfix: continue sending PDUs if ones are added whilst sending another PDU

Without this, the queue goes back to sleep on `<-oq.notifyPDUs` which won't
fire because `pendingPDUs` is already > 0. This should fix a flakey sytest.

* Break if no txn is sent

* WIP syncapi work

* More debugging

* Bump GMSL version to pull in working Event.Redact

* Remove logging

* Make redactions work on v3+

* Fix more tests

6 files changed, 85 insertions, 5 deletions

diff --git a/syncapi/consumers/roomserver.go b/syncapi/consumers/roomserver.go
index af7f612b..c6502716 100644
--- a/syncapi/consumers/roomserver.go
+++ b/syncapi/consumers/roomserver.go
@@ -81,11 +81,23 @@ func (s *OutputRoomEventConsumer) onMessage(msg *sarama.ConsumerMessage) error {
 
 	switch output.Type {
 	case api.OutputTypeNewRoomEvent:
+		// Ignore redaction events. We will add them to the database when they are
+		// validated (when we receive OutputTypeRedactedEvent)
+		event := output.NewRoomEvent.Event
+		if event.Type() == gomatrixserverlib.MRoomRedaction && event.StateKey() == nil {
+			// in the special case where the event redacts itself, just pass the message through because
+			// we will never see the other part of the pair
+			if event.Redacts() != event.EventID() {
+				return nil
+			}
+		}
 		return s.onNewRoomEvent(context.TODO(), *output.NewRoomEvent)
 	case api.OutputTypeNewInviteEvent:
 		return s.onNewInviteEvent(context.TODO(), *output.NewInviteEvent)
 	case api.OutputTypeRetireInviteEvent:
 		return s.onRetireInviteEvent(context.TODO(), *output.RetireInviteEvent)
+	case api.OutputTypeRedactedEvent:
+		return s.onRedactEvent(context.TODO(), *output.RedactedEvent)
 	default:
 		log.WithField("type", output.Type).Debug(
 			"roomserver output log: ignoring unknown output type",
@@ -94,11 +106,25 @@ func (s *OutputRoomEventConsumer) onMessage(msg *sarama.ConsumerMessage) error {
 	}
 }
 
+func (s *OutputRoomEventConsumer) onRedactEvent(
+	ctx context.Context, msg api.OutputRedactedEvent,
+) error {
+	err := s.db.RedactEvent(ctx, msg.RedactedEventID, &msg.RedactedBecause)
+	if err != nil {
+		log.WithError(err).Error("RedactEvent error'd")
+		return err
+	}
+	// fake a room event so we notify clients about the redaction, as if it were
+	// a normal event.
+	return s.onNewRoomEvent(ctx, api.OutputNewRoomEvent{
+		Event: msg.RedactedBecause,
+	})
+}
+
 func (s *OutputRoomEventConsumer) onNewRoomEvent(
 	ctx context.Context, msg api.OutputNewRoomEvent,
 ) error {
 	ev := msg.Event
-
 	addsStateEvents := msg.AddsState()
 
 	ev, err := s.updateStateEvent(ev)
@@ -173,12 +199,10 @@ func (s *OutputRoomEventConsumer) onRetireInviteEvent(
 }
 
 func (s *OutputRoomEventConsumer) updateStateEvent(event gomatrixserverlib.HeaderedEvent) (gomatrixserverlib.HeaderedEvent, error) {
-	var stateKey string
 	if event.StateKey() == nil {
-		stateKey = ""
-	} else {
-		stateKey = *event.StateKey()
+		return event, nil
 	}
+	stateKey := *event.StateKey()
 
 	prevEvent, err := s.db.GetStateEvent(
 		context.TODO(), event.RoomID(), event.Type(), stateKey,
diff --git a/syncapi/storage/interface.go b/syncapi/storage/interface.go
index c4dae4d0..a5e13b67 100644
--- a/syncapi/storage/interface.go
+++ b/syncapi/storage/interface.go
@@ -136,4 +136,6 @@ type Database interface {
 	// Returns the filterID as a string. Otherwise returns an error if something
 	// goes wrong.
 	PutFilter(ctx context.Context, localpart string, filter *gomatrixserverlib.Filter) (string, error)
+	// RedactEvent wipes an event in the database and sets the unsigned.redacted_because key to the redaction event
+	RedactEvent(ctx context.Context, redactedEventID string, redactedBecause *gomatrixserverlib.HeaderedEvent) error
 }
diff --git a/syncapi/storage/postgres/output_room_events_table.go b/syncapi/storage/postgres/output_room_events_table.go
index c7c4dc63..5315de24 100644
--- a/syncapi/storage/postgres/output_room_events_table.go
+++ b/syncapi/storage/postgres/output_room_events_table.go
@@ -99,6 +99,9 @@ const selectEarlyEventsSQL = "" +
 const selectMaxEventIDSQL = "" +
 	"SELECT MAX(id) FROM syncapi_output_room_events"
 
+const updateEventJSONSQL = "" +
+	"UPDATE syncapi_output_room_events SET headered_event_json=$1 WHERE event_id=$2"
+
 // In order for us to apply the state updates correctly, rows need to be ordered in the order they were received (id).
 const selectStateInRangeSQL = "" +
 	"SELECT id, headered_event_json, exclude_from_sync, add_state_ids, remove_state_ids" +
@@ -120,6 +123,7 @@ type outputRoomEventsStatements struct {
 	selectRecentEventsForSyncStmt *sql.Stmt
 	selectEarlyEventsStmt         *sql.Stmt
 	selectStateInRangeStmt        *sql.Stmt
+	updateEventJSONStmt           *sql.Stmt
 }
 
 func NewPostgresEventsTable(db *sql.DB) (tables.Events, error) {
@@ -149,9 +153,21 @@ func NewPostgresEventsTable(db *sql.DB) (tables.Events, error) {
 	if s.selectStateInRangeStmt, err = db.Prepare(selectStateInRangeSQL); err != nil {
 		return nil, err
 	}
+	if s.updateEventJSONStmt, err = db.Prepare(updateEventJSONSQL); err != nil {
+		return nil, err
+	}
 	return s, nil
 }
 
+func (s *outputRoomEventsStatements) UpdateEventJSON(ctx context.Context, event *gomatrixserverlib.HeaderedEvent) error {
+	headeredJSON, err := json.Marshal(event)
+	if err != nil {
+		return err
+	}
+	_, err = s.updateEventJSONStmt.ExecContext(ctx, headeredJSON, event.EventID())
+	return err
+}
+
 // selectStateInRange returns the state events between the two given PDU stream positions, exclusive of oldPos, inclusive of newPos.
 // Results are bucketed based on the room ID. If the same state is overwritten multiple times between the
 // two positions, only the most recent state is returned.
diff --git a/syncapi/storage/shared/syncserver.go b/syncapi/storage/shared/syncserver.go
index 01362ddd..38b503cd 100644
--- a/syncapi/storage/shared/syncserver.go
+++ b/syncapi/storage/shared/syncserver.go
@@ -24,6 +24,7 @@ import (
 	userapi "github.com/matrix-org/dendrite/userapi/api"
 
 	"github.com/matrix-org/dendrite/eduserver/cache"
+	"github.com/matrix-org/dendrite/internal/eventutil"
 	"github.com/matrix-org/dendrite/internal/sqlutil"
 	"github.com/matrix-org/dendrite/roomserver/api"
 	"github.com/matrix-org/dendrite/syncapi/storage/tables"
@@ -597,6 +598,26 @@ func (d *Database) IncrementalSync(
 	return res, nil
 }
 
+func (d *Database) RedactEvent(ctx context.Context, redactedEventID string, redactedBecause *gomatrixserverlib.HeaderedEvent) error {
+	redactedEvents, err := d.Events(ctx, []string{redactedEventID})
+	if err != nil {
+		return err
+	}
+	if len(redactedEvents) == 0 {
+		logrus.WithField("event_id", redactedEventID).WithField("redaction_event", redactedBecause.EventID()).Warnf("missing redacted event for redaction")
+		return nil
+	}
+	eventToRedact := redactedEvents[0].Unwrap()
+	redactionEvent := redactedBecause.Unwrap()
+	ev, err := eventutil.RedactEvent(&redactionEvent, &eventToRedact)
+	if err != nil {
+		return err
+	}
+
+	newEvent := ev.Headered(redactedBecause.RoomVersion)
+	return d.OutputEvents.UpdateEventJSON(ctx, &newEvent)
+}
+
 // getResponseWithPDUsForCompleteSync creates a response and adds all PDUs needed
 // to it. It returns toPos and joinedRoomIDs for use of adding EDUs.
 // nolint:nakedret
diff --git a/syncapi/storage/sqlite3/output_room_events_table.go b/syncapi/storage/sqlite3/output_room_events_table.go
index 0c909cc4..da2ea3f6 100644
--- a/syncapi/storage/sqlite3/output_room_events_table.go
+++ b/syncapi/storage/sqlite3/output_room_events_table.go
@@ -76,6 +76,9 @@ const selectEarlyEventsSQL = "" +
 const selectMaxEventIDSQL = "" +
 	"SELECT MAX(id) FROM syncapi_output_room_events"
 
+const updateEventJSONSQL = "" +
+	"UPDATE syncapi_output_room_events SET headered_event_json=$1 WHERE event_id=$2"
+
 // In order for us to apply the state updates correctly, rows need to be ordered in the order they were received (id).
 /*
 	$1 = oldPos,
@@ -109,6 +112,7 @@ type outputRoomEventsStatements struct {
 	selectRecentEventsForSyncStmt *sql.Stmt
 	selectEarlyEventsStmt         *sql.Stmt
 	selectStateInRangeStmt        *sql.Stmt
+	updateEventJSONStmt           *sql.Stmt
 }
 
 func NewSqliteEventsTable(db *sql.DB, streamID *streamIDStatements) (tables.Events, error) {
@@ -140,9 +144,21 @@ func NewSqliteEventsTable(db *sql.DB, streamID *streamIDStatements) (tables.Even
 	if s.selectStateInRangeStmt, err = db.Prepare(selectStateInRangeSQL); err != nil {
 		return nil, err
 	}
+	if s.updateEventJSONStmt, err = db.Prepare(updateEventJSONSQL); err != nil {
+		return nil, err
+	}
 	return s, nil
 }
 
+func (s *outputRoomEventsStatements) UpdateEventJSON(ctx context.Context, event *gomatrixserverlib.HeaderedEvent) error {
+	headeredJSON, err := json.Marshal(event)
+	if err != nil {
+		return err
+	}
+	_, err = s.updateEventJSONStmt.ExecContext(ctx, headeredJSON, event.EventID())
+	return err
+}
+
 // selectStateInRange returns the state events between the two given PDU stream positions, exclusive of oldPos, inclusive of newPos.
 // Results are bucketed based on the room ID. If the same state is overwritten multiple times between the
 // two positions, only the most recent state is returned.
diff --git a/syncapi/storage/tables/interface.go b/syncapi/storage/tables/interface.go
index 4ac0be4e..9d239d23 100644
--- a/syncapi/storage/tables/interface.go
+++ b/syncapi/storage/tables/interface.go
@@ -49,6 +49,7 @@ type Events interface {
 	// SelectEarlyEvents returns the earliest events in the given room.
 	SelectEarlyEvents(ctx context.Context, txn *sql.Tx, roomID string, r types.Range, limit int) ([]types.StreamEvent, error)
 	SelectEvents(ctx context.Context, txn *sql.Tx, eventIDs []string) ([]types.StreamEvent, error)
+	UpdateEventJSON(ctx context.Context, event *gomatrixserverlib.HeaderedEvent) error
 }
 
 // Topology keeps track of the depths and stream positions for all events.