Merge branch 'master' into kegan/history-vis

cmd/roomserver-integration-tests/main.go

@@ -215,7 +215,8 @@ func writeToRoomServer(input []string, roomserverURL string) error {
 	if err != nil {
 		return err
 	}
-	return x.InputRoomEvents(context.Background(), &request, &response)
+	x.InputRoomEvents(context.Background(), &request, &response)
+	return response.Err()
 }
 
 // testRoomserver is used to run integration tests against a single roomserver.

dendrite-config.yaml

@@ -38,9 +38,6 @@ global:
   # The path to the signing private key file, used to sign requests and events.
   private_key: matrix_key.pem
 
-  # A unique identifier for this private key. Must start with the prefix "ed25519:".
-  key_id: ed25519:auto
-
   # How long a remote server can cache our server signing key before requesting it
   # again. Increasing this number will reduce the number of requests made by other
   # servers for our key but increases the period that a compromised key will be

federationapi/routing/keys.go

@@ -19,11 +19,14 @@ import (
 	"net/http"
 	"time"
 
+	"github.com/matrix-org/dendrite/clientapi/httputil"
 	"github.com/matrix-org/dendrite/clientapi/jsonerror"
+	federationSenderAPI "github.com/matrix-org/dendrite/federationsender/api"
 	"github.com/matrix-org/dendrite/internal/config"
 	"github.com/matrix-org/dendrite/keyserver/api"
 	"github.com/matrix-org/gomatrixserverlib"
 	"github.com/matrix-org/util"
+	"github.com/sirupsen/logrus"
 	"golang.org/x/crypto/ed25519"
 )
 
@@ -160,3 +163,62 @@ func localKeys(cfg *config.FederationAPI, validUntil time.Time) (*gomatrixserver
 
 	return &keys, nil
 }
+
+func NotaryKeys(
+	httpReq *http.Request, cfg *config.FederationAPI,
+	fsAPI federationSenderAPI.FederationSenderInternalAPI,
+	req *gomatrixserverlib.PublicKeyNotaryLookupRequest,
+) util.JSONResponse {
+	if req == nil {
+		req = &gomatrixserverlib.PublicKeyNotaryLookupRequest{}
+		if reqErr := httputil.UnmarshalJSONRequest(httpReq, &req); reqErr != nil {
+			return *reqErr
+		}
+	}
+
+	var response struct {
+		ServerKeys []json.RawMessage `json:"server_keys"`
+	}
+	response.ServerKeys = []json.RawMessage{}
+
+	for serverName := range req.ServerKeys {
+		var keys *gomatrixserverlib.ServerKeys
+		if serverName == cfg.Matrix.ServerName {
+			if k, err := localKeys(cfg, time.Now().Add(cfg.Matrix.KeyValidityPeriod)); err == nil {
+				keys = k
+			} else {
+				return util.ErrorResponse(err)
+			}
+		} else {
+			if k, err := fsAPI.GetServerKeys(httpReq.Context(), serverName); err == nil {
+				keys = &k
+			} else {
+				return util.ErrorResponse(err)
+			}
+		}
+		if keys == nil {
+			continue
+		}
+
+		j, err := json.Marshal(keys)
+		if err != nil {
+			logrus.WithError(err).Errorf("Failed to marshal %q response", serverName)
+			return jsonerror.InternalServerError()
+		}
+
+		js, err := gomatrixserverlib.SignJSON(
+			string(cfg.Matrix.ServerName), cfg.Matrix.KeyID, cfg.Matrix.PrivateKey, j,
+		)
+		if err != nil {
+			logrus.WithError(err).Errorf("Failed to sign %q response", serverName)
+			return jsonerror.InternalServerError()
+		}
+
+		response.ServerKeys = append(response.ServerKeys, js)
+	}
+
+	return util.JSONResponse{
+		Code: http.StatusOK,
+		JSON: response,
+	}
+}

federationapi/routing/routing.go

@@ -61,6 +61,26 @@ func Setup(
 		return LocalKeys(cfg)
 	})
 
+	notaryKeys := httputil.MakeExternalAPI("notarykeys", func(req *http.Request) util.JSONResponse {
+		vars, err := httputil.URLDecodeMapValues(mux.Vars(req))
+		if err != nil {
+			return util.ErrorResponse(err)
+		}
+		var pkReq *gomatrixserverlib.PublicKeyNotaryLookupRequest
+		serverName := gomatrixserverlib.ServerName(vars["serverName"])
+		keyID := gomatrixserverlib.KeyID(vars["keyID"])
+		if serverName != "" && keyID != "" {
+			pkReq = &gomatrixserverlib.PublicKeyNotaryLookupRequest{
+				ServerKeys: map[gomatrixserverlib.ServerName]map[gomatrixserverlib.KeyID]gomatrixserverlib.PublicKeyNotaryQueryCriteria{
+					serverName: {
+						keyID: gomatrixserverlib.PublicKeyNotaryQueryCriteria{},
+					},
+				},
+			}
+		}
+		return NotaryKeys(req, cfg, fsAPI, pkReq)
+	})
+
 	// Ignore the {keyID} argument as we only have a single server key so we always
 	// return that key.
 	// Even if we had more than one server key, we would probably still ignore the
@@ -68,6 +88,8 @@ func Setup(
 	v2keysmux.Handle("/server/{keyID}", localKeys).Methods(http.MethodGet)
 	v2keysmux.Handle("/server/", localKeys).Methods(http.MethodGet)
 	v2keysmux.Handle("/server", localKeys).Methods(http.MethodGet)
+	v2keysmux.Handle("/query", notaryKeys).Methods(http.MethodPost)
+	v2keysmux.Handle("/query/{serverName}/{keyID}", notaryKeys).Methods(http.MethodGet)
 
 	v1fedmux.Handle("/send/{txnID}", httputil.MakeFedAPI(
 		"federation_send", cfg.Matrix.ServerName, keys, wakeup,

federationapi/routing/send.go

@@ -372,12 +372,9 @@ func (t *txnReq) processEvent(ctx context.Context, e gomatrixserverlib.Event, is
 		return t.processEventWithMissingState(ctx, e, stateResp.RoomVersion, isInboundTxn)
 	}
 
-	// Check that the event is allowed by the state at the event.
+	// pass the event to the roomserver which will do auth checks
-	if err := checkAllowedByState(e, gomatrixserverlib.UnwrapEventHeaders(stateResp.StateEvents)); err != nil {
+	// If the event fail auth checks, gmsl.NotAllowed error will be returned which we be silently
-		return err
+	// discarded by the caller of this function
-	}
-
-	// pass the event to the roomserver
 	return api.SendEvents(
 		context.Background(),
 		t.rsAPI,

federationapi/routing/send_test.go

@@ -89,12 +89,11 @@ func (t *testRoomserverAPI) InputRoomEvents(
 	ctx context.Context,
 	request *api.InputRoomEventsRequest,
 	response *api.InputRoomEventsResponse,
-) error {
+) {
 	t.inputRoomEvents = append(t.inputRoomEvents, request.InputRoomEvents...)
 	for _, ire := range request.InputRoomEvents {
 		fmt.Println("InputRoomEvents: ", ire.Event.EventID())
 	}
-	return nil
 }
 
 func (t *testRoomserverAPI) PerformInvite(
@@ -461,7 +460,8 @@ func TestBasicTransaction(t *testing.T) {
 	assertInputRoomEvents(t, rsAPI.inputRoomEvents, []gomatrixserverlib.HeaderedEvent{testEvents[len(testEvents)-1]})
 }
 
-// The purpose of this test is to check that if the event received fails auth checks the transaction is failed.
+// The purpose of this test is to check that if the event received fails auth checks the event is still sent to the roomserver
+// as it does the auth check.
 func TestTransactionFailAuthChecks(t *testing.T) {
 	rsAPI := &testRoomserverAPI{
 		queryStateAfterEvents: func(req *api.QueryStateAfterEventsRequest) api.QueryStateAfterEventsResponse {
@@ -479,11 +479,9 @@ func TestTransactionFailAuthChecks(t *testing.T) {
 		testData[len(testData)-1], // a message event
 	}
 	txn := mustCreateTransaction(rsAPI, &txnFedClient{}, pdus)
-	mustProcessTransaction(t, txn, []string{
+	mustProcessTransaction(t, txn, []string{})
-		// expect the event to have an error
+	// expect message to be sent to the roomserver
-		testEvents[len(testEvents)-1].EventID(),
+	assertInputRoomEvents(t, rsAPI.inputRoomEvents, []gomatrixserverlib.HeaderedEvent{testEvents[len(testEvents)-1]})
-	})
-	assertInputRoomEvents(t, rsAPI.inputRoomEvents, nil) // expect no messages to be sent to the roomserver
 }
 
 // The purpose of this test is to make sure that when an event is received for which we do not know the prev_events,

federationsender/api/api.go

@@ -20,6 +20,8 @@ type FederationClient interface {
 	ClaimKeys(ctx context.Context, s gomatrixserverlib.ServerName, oneTimeKeys map[string]map[string]string) (res gomatrixserverlib.RespClaimKeys, err error)
 	QueryKeys(ctx context.Context, s gomatrixserverlib.ServerName, keys map[string][]string) (res gomatrixserverlib.RespQueryKeys, err error)
 	GetEvent(ctx context.Context, s gomatrixserverlib.ServerName, eventID string) (res gomatrixserverlib.Transaction, err error)
+	GetServerKeys(ctx context.Context, matrixServer gomatrixserverlib.ServerName) (gomatrixserverlib.ServerKeys, error)
+	LookupServerKeys(ctx context.Context, s gomatrixserverlib.ServerName, keyRequests map[gomatrixserverlib.PublicKeyLookupRequest]gomatrixserverlib.Timestamp) ([]gomatrixserverlib.ServerKeys, error)
 }
 
 // FederationClientError is returned from FederationClient methods in the event of a problem.

federationsender/internal/api.go

@@ -2,6 +2,7 @@ package internal
 
 import (
 	"context"
+	"sync"
 	"time"
 
 	"github.com/matrix-org/dendrite/federationsender/api"
@@ -23,6 +24,7 @@ type FederationSenderInternalAPI struct {
 	federation *gomatrixserverlib.FederationClient
 	keyRing    *gomatrixserverlib.KeyRing
 	queues     *queue.OutgoingQueues
+	joins      sync.Map // joins currently in progress
 }
 
 func NewFederationSenderInternalAPI(
@@ -187,3 +189,27 @@ func (a *FederationSenderInternalAPI) GetEvent(
 	}
 	return ires.(gomatrixserverlib.Transaction), nil
 }
+
+func (a *FederationSenderInternalAPI) GetServerKeys(
+	ctx context.Context, s gomatrixserverlib.ServerName,
+) (gomatrixserverlib.ServerKeys, error) {
+	ires, err := a.doRequest(s, func() (interface{}, error) {
+		return a.federation.GetServerKeys(ctx, s)
+	})
+	if err != nil {
+		return gomatrixserverlib.ServerKeys{}, err
+	}
+	return ires.(gomatrixserverlib.ServerKeys), nil
+}
+
+func (a *FederationSenderInternalAPI) LookupServerKeys(
+	ctx context.Context, s gomatrixserverlib.ServerName, keyRequests map[gomatrixserverlib.PublicKeyLookupRequest]gomatrixserverlib.Timestamp,
+) ([]gomatrixserverlib.ServerKeys, error) {
+	ires, err := a.doRequest(s, func() (interface{}, error) {
+		return a.federation.LookupServerKeys(ctx, s, keyRequests)
+	})
+	if err != nil {
+		return []gomatrixserverlib.ServerKeys{}, err
+	}
+	return ires.([]gomatrixserverlib.ServerKeys), nil
+}

federationsender/internal/perform.go

@@ -37,12 +37,32 @@ func (r *FederationSenderInternalAPI) PerformDirectoryLookup(
 	return nil
 }
 
+type federatedJoin struct {
+	UserID string
+	RoomID string
+}
+
 // PerformJoinRequest implements api.FederationSenderInternalAPI
 func (r *FederationSenderInternalAPI) PerformJoin(
 	ctx context.Context,
 	request *api.PerformJoinRequest,
 	response *api.PerformJoinResponse,
 ) {
+	// Check that a join isn't already in progress for this user/room.
+	j := federatedJoin{request.UserID, request.RoomID}
+	if _, found := r.joins.Load(j); found {
+		response.LastError = &gomatrix.HTTPError{
+			Code: 429,
+			Message: `{
+				"errcode": "M_LIMIT_EXCEEDED",
+				"error": "There is already a federated join to this room in progress. Please wait for it to finish."
+			}`, // TODO: Why do none of our error types play nicely with each other?
+		}
+		return
+	}
+	r.joins.Store(j, nil)
+	defer r.joins.Delete(j)
+
 	// Look up the supported room versions.
 	var supportedVersions []gomatrixserverlib.RoomVersion
 	for version := range version.SupportedRoomVersions() {
@@ -98,7 +118,10 @@ func (r *FederationSenderInternalAPI) PerformJoin(
 		response.LastError = &gomatrix.HTTPError{
 			Code:         0,
 			WrappedError: nil,
-			Message:      lastErr.Error(),
+			Message:      "Unknown HTTP error",
+		}
+		if lastErr != nil {
+			response.LastError.Message = lastErr.Error()
 		}
 	}
 
@@ -183,27 +206,47 @@ func (r *FederationSenderInternalAPI) performJoinUsingServer(
 	}
 	r.statistics.ForServer(serverName).Success()
 
+	// Process the join response in a goroutine. The idea here is
+	// that we'll try and wait for as long as possible for the work
+	// to complete, but if the client does give up waiting, we'll
+	// still continue to process the join anyway so that we don't
+	// waste the effort.
+	var cancel context.CancelFunc
+	ctx, cancel = context.WithCancel(context.Background())
+	go func() {
+		defer cancel()
+
 		// Check that the send_join response was valid.
 		joinCtx := perform.JoinContext(r.federation, r.keyRing)
 		respState, err := joinCtx.CheckSendJoinResponse(
 			ctx, event, serverName, respMakeJoin, respSendJoin,
 		)
 		if err != nil {
-		return fmt.Errorf("joinCtx.CheckSendJoinResponse: %w", err)
+			logrus.WithFields(logrus.Fields{
+				"room_id": roomID,
+				"user_id": userID,
+			}).WithError(err).Error("Failed to process room join response")
+			return
 		}
 
 		// If we successfully performed a send_join above then the other
 		// server now thinks we're a part of the room. Send the newly
 		// returned state to the roomserver to update our local view.
-	if err = roomserverAPI.SendEventWithState(
+		if err = roomserverAPI.SendEventWithRewrite(
 			ctx, r.rsAPI,
 			respState,
 			event.Headered(respMakeJoin.RoomVersion),
 			nil,
 		); err != nil {
-		return fmt.Errorf("r.producer.SendEventWithState: %w", err)
+			logrus.WithFields(logrus.Fields{
+				"room_id": roomID,
+				"user_id": userID,
+			}).WithError(err).Error("Failed to send room join response to roomserver")
+			return
 		}
+	}()
 
+	<-ctx.Done()
 	return nil
 }
 

federationsender/inthttp/client.go

@@ -30,6 +30,8 @@ const (
 	FederationSenderLookupStatePath      = "/federationsender/client/lookupState"
 	FederationSenderLookupStateIDsPath   = "/federationsender/client/lookupStateIDs"
 	FederationSenderGetEventPath         = "/federationsender/client/getEvent"
+	FederationSenderGetServerKeysPath    = "/federationsender/client/getServerKeys"
+	FederationSenderLookupServerKeysPath = "/federationsender/client/lookupServerKeys"
 )
 
 // NewFederationSenderClient creates a FederationSenderInternalAPI implemented by talking to a HTTP POST API.
@@ -358,3 +360,59 @@ func (h *httpFederationSenderInternalAPI) GetEvent(
 	}
 	return *response.Res, nil
 }
+
+type getServerKeys struct {
+	S          gomatrixserverlib.ServerName
+	ServerKeys gomatrixserverlib.ServerKeys
+	Err        *api.FederationClientError
+}
+
+func (h *httpFederationSenderInternalAPI) GetServerKeys(
+	ctx context.Context, s gomatrixserverlib.ServerName,
+) (gomatrixserverlib.ServerKeys, error) {
+	span, ctx := opentracing.StartSpanFromContext(ctx, "GetServerKeys")
+	defer span.Finish()
+
+	request := getServerKeys{
+		S: s,
+	}
+	var response getServerKeys
+	apiURL := h.federationSenderURL + FederationSenderGetServerKeysPath
+	err := httputil.PostJSON(ctx, span, h.httpClient, apiURL, &request, &response)
+	if err != nil {
+		return gomatrixserverlib.ServerKeys{}, err
+	}
+	if response.Err != nil {
+		return gomatrixserverlib.ServerKeys{}, response.Err
+	}
+	return response.ServerKeys, nil
+}
+
+type lookupServerKeys struct {
+	S           gomatrixserverlib.ServerName
+	KeyRequests map[gomatrixserverlib.PublicKeyLookupRequest]gomatrixserverlib.Timestamp
+	ServerKeys  []gomatrixserverlib.ServerKeys
+	Err         *api.FederationClientError
+}
+
+func (h *httpFederationSenderInternalAPI) LookupServerKeys(
+	ctx context.Context, s gomatrixserverlib.ServerName, keyRequests map[gomatrixserverlib.PublicKeyLookupRequest]gomatrixserverlib.Timestamp,
+) ([]gomatrixserverlib.ServerKeys, error) {
+	span, ctx := opentracing.StartSpanFromContext(ctx, "LookupServerKeys")
+	defer span.Finish()
+
+	request := lookupServerKeys{
+		S:           s,
+		KeyRequests: keyRequests,
+	}
+	var response lookupServerKeys
+	apiURL := h.federationSenderURL + FederationSenderLookupServerKeysPath
+	err := httputil.PostJSON(ctx, span, h.httpClient, apiURL, &request, &response)
+	if err != nil {
+		return []gomatrixserverlib.ServerKeys{}, err
+	}
+	if response.Err != nil {
+		return []gomatrixserverlib.ServerKeys{}, response.Err
+	}
+	return response.ServerKeys, nil
+}

federationsender/inthttp/server.go

@@ -263,4 +263,48 @@ func AddRoutes(intAPI api.FederationSenderInternalAPI, internalAPIMux *mux.Route
 			return util.JSONResponse{Code: http.StatusOK, JSON: request}
 		}),
 	)
+	internalAPIMux.Handle(
+		FederationSenderGetServerKeysPath,
+		httputil.MakeInternalAPI("GetServerKeys", func(req *http.Request) util.JSONResponse {
+			var request getServerKeys
+			if err := json.NewDecoder(req.Body).Decode(&request); err != nil {
+				return util.MessageResponse(http.StatusBadRequest, err.Error())
+			}
+			res, err := intAPI.GetServerKeys(req.Context(), request.S)
+			if err != nil {
+				ferr, ok := err.(*api.FederationClientError)
+				if ok {
+					request.Err = ferr
+				} else {
+					request.Err = &api.FederationClientError{
+						Err: err.Error(),
+					}
+				}
+			}
+			request.ServerKeys = res
+			return util.JSONResponse{Code: http.StatusOK, JSON: request}
+		}),
+	)
+	internalAPIMux.Handle(
+		FederationSenderLookupServerKeysPath,
+		httputil.MakeInternalAPI("LookupServerKeys", func(req *http.Request) util.JSONResponse {
+			var request lookupServerKeys
+			if err := json.NewDecoder(req.Body).Decode(&request); err != nil {
+				return util.MessageResponse(http.StatusBadRequest, err.Error())
+			}
+			res, err := intAPI.LookupServerKeys(req.Context(), request.S, request.KeyRequests)
+			if err != nil {
+				ferr, ok := err.(*api.FederationClientError)
+				if ok {
+					request.Err = ferr
+				} else {
+					request.Err = &api.FederationClientError{
+						Err: err.Error(),
+					}
+				}
+			}
+			request.ServerKeys = res
+			return util.JSONResponse{Code: http.StatusOK, JSON: request}
+		}),
+	)
 }

federationsender/queue/destinationqueue.go

@@ -231,13 +231,24 @@ func (oq *destinationQueue) backgroundSend() {
 		// If we are backing off this server then wait for the
 		// backoff duration to complete first, or until explicitly
 		// told to retry.
-		if _, giveUp := oq.statistics.BackoffIfRequired(oq.backingOff, oq.interruptBackoff); giveUp {
+		until, blacklisted := oq.statistics.BackoffInfo()
+		if blacklisted {
 			// It's been suggested that we should give up because the backoff
 			// has exceeded a maximum allowable value. Clean up the in-memory
 			// buffers at this point. The PDU clean-up is already on a defer.
 			log.Warnf("Blacklisting %q due to exceeding backoff threshold", oq.destination)
 			return
 		}
+		if until != nil && until.After(time.Now()) {
+			// We haven't backed off yet, so wait for the suggested amount of
+			// time.
+			duration := time.Until(*until)
+			log.Warnf("Backing off %q for %s", oq.destination, duration)
+			select {
+			case <-time.After(duration):
+			case <-oq.interruptBackoff:
+			}
+		}
 
 		// If we have pending PDUs or EDUs then construct a transaction.
 		if pendingPDUs || pendingEDUs {

federationsender/statistics/statistics.go

@@ -44,6 +44,7 @@ func (s *Statistics) ForServer(serverName gomatrixserverlib.ServerName) *ServerS
 		server = &ServerStatistics{
 			statistics: s,
 			serverName: serverName,
+			interrupt:  make(chan struct{}),
 		}
 		s.servers[serverName] = server
 		s.mutex.Unlock()
@@ -68,6 +69,7 @@ type ServerStatistics struct {
 	backoffStarted atomic.Bool                  // is the backoff started
 	backoffUntil   atomic.Value                 // time.Time until this backoff interval ends
 	backoffCount   atomic.Uint32                // number of times BackoffDuration has been called
+	interrupt      chan struct{}                // interrupts the backoff goroutine
 	successCounter atomic.Uint32                // how many times have we succeeded?
 }
 
@@ -76,15 +78,24 @@ func (s *ServerStatistics) duration(count uint32) time.Duration {
 	return time.Second * time.Duration(math.Exp2(float64(count)))
 }
 
+// cancel will interrupt the currently active backoff.
+func (s *ServerStatistics) cancel() {
+	s.blacklisted.Store(false)
+	s.backoffUntil.Store(time.Time{})
+	select {
+	case s.interrupt <- struct{}{}:
+	default:
+	}
+}
+
 // Success updates the server statistics with a new successful
 // attempt, which increases the sent counter and resets the idle and
 // failure counters. If a host was blacklisted at this point then
 // we will unblacklist it.
 func (s *ServerStatistics) Success() {
-	s.successCounter.Add(1)
+	s.cancel()
-	s.backoffStarted.Store(false)
+	s.successCounter.Inc()
 	s.backoffCount.Store(0)
-	s.blacklisted.Store(false)
 	if s.statistics.DB != nil {
 		if err := s.statistics.DB.RemoveServerFromBlacklist(s.serverName); err != nil {
 			logrus.WithError(err).Errorf("Failed to remove %q from blacklist", s.serverName)
@@ -99,10 +110,30 @@ func (s *ServerStatistics) Success() {
 // whether we have blacklisted and therefore to give up.
 func (s *ServerStatistics) Failure() (time.Time, bool) {
 	// If we aren't already backing off, this call will start
-	// a new backoff period. Reset the counter to 0 so that
+	// a new backoff period. Increase the failure counter and
-	// we backoff only for short periods of time to start with.
+	// start a goroutine which will wait out the backoff and
+	// unset the backoffStarted flag when done.
 	if s.backoffStarted.CAS(false, true) {
-		s.backoffCount.Store(0)
+		if s.backoffCount.Inc() >= s.statistics.FailuresUntilBlacklist {
+			s.blacklisted.Store(true)
+			if s.statistics.DB != nil {
+				if err := s.statistics.DB.AddServerToBlacklist(s.serverName); err != nil {
+					logrus.WithError(err).Errorf("Failed to add %q to blacklist", s.serverName)
+				}
+			}
+			return time.Time{}, true
+		}
+
+		go func() {
+			until, ok := s.backoffUntil.Load().(time.Time)
+			if ok {
+				select {
+				case <-time.After(time.Until(until)):
+				case <-s.interrupt:
+				}
+			}
+			s.backoffStarted.Store(false)
+		}()
 	}
 
 	// Check if we have blacklisted this node.
@@ -136,53 +167,6 @@ func (s *ServerStatistics) BackoffInfo() (*time.Time, bool) {
 	return nil, s.blacklisted.Load()
 }
 
-// BackoffIfRequired will block for as long as the current
-// backoff requires, if needed. Otherwise it will do nothing.
-// Returns the amount of time to backoff for and whether to give up or not.
-func (s *ServerStatistics) BackoffIfRequired(backingOff atomic.Bool, interrupt <-chan bool) (time.Duration, bool) {
-	if started := s.backoffStarted.Load(); !started {
-		return 0, false
-	}
-
-	// Work out if we should be blacklisting at this point.
-	count := s.backoffCount.Inc()
-	if count >= s.statistics.FailuresUntilBlacklist {
-		// We've exceeded the maximum amount of times we're willing
-		// to back off, which is probably in the region of hours by
-		// now. Mark the host as blacklisted and tell the caller to
-		// give up.
-		s.blacklisted.Store(true)
-		if s.statistics.DB != nil {
-			if err := s.statistics.DB.AddServerToBlacklist(s.serverName); err != nil {
-				logrus.WithError(err).Errorf("Failed to add %q to blacklist", s.serverName)
-			}
-		}
-		return 0, true
-	}
-
-	// Work out when we should wait until.
-	duration := s.duration(count)
-	until := time.Now().Add(duration)
-	s.backoffUntil.Store(until)
-
-	// Notify the destination queue that we're backing off now.
-	backingOff.Store(true)
-	defer backingOff.Store(false)
-
-	// Work out how long we should be backing off for.
-	logrus.Warnf("Backing off %q for %s", s.serverName, duration)
-
-	// Wait for either an interruption or for the backoff to
-	// complete.
-	select {
-	case <-interrupt:
-		logrus.Debugf("Interrupting backoff for %q", s.serverName)
-	case <-time.After(duration):
-	}
-
-	return duration, false
-}
-
 // Blacklisted returns true if the server is blacklisted and false
 // otherwise.
 func (s *ServerStatistics) Blacklisted() bool {

federationsender/statistics/statistics_test.go

@@ -4,8 +4,6 @@ import (
 	"math"
 	"testing"
 	"time"
-
-	"go.uber.org/atomic"
 )
 
 func TestBackoff(t *testing.T) {
@@ -27,34 +25,30 @@ func TestBackoff(t *testing.T) {
 	server.Failure()
 
 	t.Logf("Backoff counter: %d", server.backoffCount.Load())
-	backingOff := atomic.Bool{}
 
 	// Now we're going to simulate backing off a few times to see
 	// what happens.
 	for i := uint32(1); i <= 10; i++ {
-		// Interrupt the backoff - it doesn't really matter if it
-		// completes but we will find out how long the backoff should
-		// have been.
-		interrupt := make(chan bool, 1)
-		close(interrupt)
-
-		// Get the duration.
-		duration, blacklist := server.BackoffIfRequired(backingOff, interrupt)
-
 		// Register another failure for good measure. This should have no
 		// side effects since a backoff is already in progress. If it does
 		// then we'll fail.
 		until, blacklisted := server.Failure()
-		if time.Until(until) > duration {
+
-			t.Fatal("Failure produced unexpected side effect when it shouldn't have")
+		// Get the duration.
-		}
+		_, blacklist := server.BackoffInfo()
+		duration := time.Until(until).Round(time.Second)
+
+		// Unset the backoff, or otherwise our next call will think that
+		// there's a backoff in progress and return the same result.
+		server.cancel()
+		server.backoffStarted.Store(false)
 
 		// Check if we should be blacklisted by now.
 		if i >= stats.FailuresUntilBlacklist {
 			if !blacklist {
 				t.Fatalf("Backoff %d should have resulted in blacklist but didn't", i)
 			} else if blacklist != blacklisted {
-				t.Fatalf("BackoffIfRequired and Failure returned different blacklist values")
+				t.Fatalf("BackoffInfo and Failure returned different blacklist values")
 			} else {
 				t.Logf("Backoff %d is blacklisted as expected", i)
 				continue

go.mod

@@ -1,6 +1,7 @@
 module github.com/matrix-org/dendrite
 
 require (
+	github.com/DATA-DOG/go-sqlmock v1.5.0
 	github.com/Shopify/sarama v1.27.0
 	github.com/codahale/hdrhistogram v0.0.0-20161010025455-3a0bb77429bd // indirect
 	github.com/gologme/log v1.2.0
@@ -21,7 +22,7 @@ require (
 	github.com/matrix-org/go-http-js-libp2p v0.0.0-20200518170932-783164aeeda4
 	github.com/matrix-org/go-sqlite3-js v0.0.0-20200522092705-bc8506ccbcf3
 	github.com/matrix-org/gomatrix v0.0.0-20200827122206-7dd5e2a05bcd
-	github.com/matrix-org/gomatrixserverlib v0.0.0-20200907151926-38f437f2b2a6
+	github.com/matrix-org/gomatrixserverlib v0.0.0-20200922152606-4aa1159e672b
 	github.com/matrix-org/naffka v0.0.0-20200901083833-bcdd62999a91
 	github.com/matrix-org/util v0.0.0-20200807132607-55161520e1d4
 	github.com/mattn/go-sqlite3 v1.14.2

go.sum

@@ -13,6 +13,8 @@ github.com/Arceliar/phony v0.0.0-20191006174943-d0c68492aca0 h1:p3puK8Sl2xK+2Fnn
 github.com/Arceliar/phony v0.0.0-20191006174943-d0c68492aca0/go.mod h1:6Lkn+/zJilRMsKmbmG1RPoamiArC6HS73xbwRyp3UyI=
 github.com/BurntSushi/toml v0.3.1 h1:WXkYYl6Yr3qBf1K79EBnL4mak0OimBfB0XUf9Vl28OQ=
 github.com/BurntSushi/toml v0.3.1/go.mod h1:xHWCNGjB5oqiDr8zfno3MHue2Ht5sIBksp03qcyfWMU=
+github.com/DATA-DOG/go-sqlmock v1.5.0 h1:Shsta01QNfFxHCfpW6YH2STWB0MudeXXEWMr20OEh60=
+github.com/DATA-DOG/go-sqlmock v1.5.0/go.mod h1:f/Ixk793poVmq4qj/V1dPUg2JEAKC73Q5eFN3EC/SaM=
 github.com/Kubuxu/go-os-helper v0.0.1/go.mod h1:N8B+I7vPCT80IcP58r50u4+gEEcsZETFUpAzWW2ep1Y=
 github.com/OneOfOne/xxhash v1.2.2/go.mod h1:HSdplMjZKSmBqAxg5vPj2TmRDmfkzw+cTzAElWljhcU=
 github.com/PuerkitoBio/goquery v1.5.1/go.mod h1:GsLWisAFVj4WgDibEWF4pvYnkVQBpKBKeU+7zCJoLcc=
@@ -567,8 +569,8 @@ github.com/matrix-org/gomatrix v0.0.0-20190528120928-7df988a63f26 h1:Hr3zjRsq2bh
 github.com/matrix-org/gomatrix v0.0.0-20190528120928-7df988a63f26/go.mod h1:3fxX6gUjWyI/2Bt7J1OLhpCzOfO/bB3AiX0cJtEKud0=
 github.com/matrix-org/gomatrix v0.0.0-20200827122206-7dd5e2a05bcd h1:xVrqJK3xHREMNjwjljkAUaadalWc0rRbmVuQatzmgwg=
 github.com/matrix-org/gomatrix v0.0.0-20200827122206-7dd5e2a05bcd/go.mod h1:/gBX06Kw0exX1HrwmoBibFA98yBk/jxKpGVeyQbff+s=
-github.com/matrix-org/gomatrixserverlib v0.0.0-20200907151926-38f437f2b2a6 h1:43gla6bLt4opWY1mQkAasF/LUCipZl7x2d44TY0wf40=
+github.com/matrix-org/gomatrixserverlib v0.0.0-20200922152606-4aa1159e672b h1:I8H9ftkT1K/OA2urt/dfXAYpO3pOiMQL5bvoWm4i0RA=
-github.com/matrix-org/gomatrixserverlib v0.0.0-20200907151926-38f437f2b2a6/go.mod h1:JsAzE1Ll3+gDWS9JSUHPJiiyAksvOOnGWF2nXdg4ZzU=
+github.com/matrix-org/gomatrixserverlib v0.0.0-20200922152606-4aa1159e672b/go.mod h1:JsAzE1Ll3+gDWS9JSUHPJiiyAksvOOnGWF2nXdg4ZzU=
 github.com/matrix-org/naffka v0.0.0-20200901083833-bcdd62999a91 h1:HJ6U3S3ljJqNffYMcIeAncp5qT/i+ZMiJ2JC2F0aXP4=
 github.com/matrix-org/naffka v0.0.0-20200901083833-bcdd62999a91/go.mod h1:sjyPyRxKM5uw1nD2cJ6O2OxI6GOqyVBfNXqKjBZTBZE=
 github.com/matrix-org/util v0.0.0-20190711121626-527ce5ddefc7 h1:ntrLa/8xVzeSs8vHFHK25k0C+NV74sYMJnNSg5NoSRo=

internal/config/config.go

@@ -36,6 +36,9 @@ import (
 	jaegermetrics "github.com/uber/jaeger-lib/metrics"
 )
 
+// keyIDRegexp defines allowable characters in Key IDs.
+var keyIDRegexp = regexp.MustCompile("^ed25519:[a-zA-Z0-9_]+$")
+
 // Version is the current version of the config format.
 // This will change whenever we make breaking changes to the config format.
 const Version = 1
@@ -459,6 +462,9 @@ func readKeyPEM(path string, data []byte) (gomatrixserverlib.KeyID, ed25519.Priv
 			if !strings.HasPrefix(keyID, "ed25519:") {
 				return "", nil, fmt.Errorf("key ID %q doesn't start with \"ed25519:\" in %q", keyID, path)
 			}
+			if !keyIDRegexp.MatchString(keyID) {
+				return "", nil, fmt.Errorf("key ID %q in %q contains illegal characters (use a-z, A-Z, 0-9 and _ only)", keyID, path)
+			}
 			_, privKey, err := ed25519.GenerateKey(bytes.NewReader(keyBlock.Bytes))
 			if err != nil {
 				return "", nil, err

internal/config/config_global.go

@@ -20,7 +20,7 @@ type Global struct {
 
 	// An arbitrary string used to uniquely identify the PrivateKey. Must start with the
 	// prefix "ed25519:".
-	KeyID gomatrixserverlib.KeyID `yaml:"key_id"`
+	KeyID gomatrixserverlib.KeyID `yaml:"-"`
 
 	// How long a remote server can cache our server key for before requesting it again.
 	// Increasing this number will reduce the number of requests made by remote servers

internal/sqlutil/sql.go

@@ -15,10 +15,14 @@
 package sqlutil
 
 import (
+	"context"
 	"database/sql"
 	"errors"
 	"fmt"
 	"runtime"
+	"strings"
+
+	"github.com/matrix-org/util"
 )
 
 // ErrUserExists is returned if a username already exists in the database.
@@ -107,3 +111,44 @@ func SQLiteDriverName() string {
 	}
 	return "sqlite3"
 }
+
+func minOfInts(a, b int) int {
+	if a <= b {
+		return a
+	}
+	return b
+}
+
+// QueryProvider defines the interface for querys used by RunLimitedVariablesQuery.
+type QueryProvider interface {
+	QueryContext(ctx context.Context, query string, args ...interface{}) (*sql.Rows, error)
+}
+
+// SQLite3MaxVariables is the default maximum number of host parameters in a single SQL statement
+// SQLlite can handle. See https://www.sqlite.org/limits.html for more information.
+const SQLite3MaxVariables = 999
+
+// RunLimitedVariablesQuery split up a query with more variables than the used database can handle in multiple queries.
+func RunLimitedVariablesQuery(ctx context.Context, query string, qp QueryProvider, variables []interface{}, limit uint, rowHandler func(*sql.Rows) error) error {
+	var start int
+	for start < len(variables) {
+		n := minOfInts(len(variables)-start, int(limit))
+		nextQuery := strings.Replace(query, "($1)", QueryVariadic(n), 1)
+		rows, err := qp.QueryContext(ctx, nextQuery, variables[start:start+n]...)
+		if err != nil {
+			util.GetLogger(ctx).WithError(err).Error("QueryContext returned an error")
+			return err
+		}
+		err = rowHandler(rows)
+		if closeErr := rows.Close(); closeErr != nil {
+			util.GetLogger(ctx).WithError(closeErr).Error("RunLimitedVariablesQuery: failed to close rows")
+			return err
+		}
+		if err != nil {
+			util.GetLogger(ctx).WithError(err).Error("RunLimitedVariablesQuery: rowHandler returned error")
+			return err
+		}
+		start = start + n
+	}
+	return nil
+}

internal/sqlutil/sqlutil_test.go

@@ -0,0 +1,173 @@
+package sqlutil
+
+import (
+	"context"
+	"database/sql"
+	"reflect"
+	"testing"
+
+	sqlmock "github.com/DATA-DOG/go-sqlmock"
+)
+
+func TestShouldReturnCorrectAmountOfResulstIfFewerVariablesThanLimit(t *testing.T) {
+	db, mock, err := sqlmock.New()
+	assertNoError(t, err, "Failed to make DB")
+	limit := uint(4)
+
+	r := mock.NewRows([]string{"id"}).
+		AddRow(1).
+		AddRow(2).
+		AddRow(3)
+
+	mock.ExpectQuery(`SELECT id WHERE id IN \(\$1, \$2, \$3\)`).WillReturnRows(r)
+	// nolint:goconst
+	q := "SELECT id WHERE id IN ($1)"
+	v := []int{1, 2, 3}
+	iKeyIDs := make([]interface{}, len(v))
+	for i, d := range v {
+		iKeyIDs[i] = d
+	}
+
+	ctx := context.Background()
+	var result = make([]int, 0)
+	err = RunLimitedVariablesQuery(ctx, q, db, iKeyIDs, limit, func(rows *sql.Rows) error {
+		for rows.Next() {
+			var id int
+			err = rows.Scan(&id)
+			assertNoError(t, err, "rows.Scan returned an error")
+			result = append(result, id)
+		}
+		return nil
+	})
+	assertNoError(t, err, "Call returned an error")
+	if len(result) != len(v) {
+		t.Fatalf("Result should be 3 long")
+	}
+}
+
+func TestShouldReturnCorrectAmountOfResulstIfEqualVariablesAsLimit(t *testing.T) {
+	db, mock, err := sqlmock.New()
+	assertNoError(t, err, "Failed to make DB")
+	limit := uint(4)
+
+	r := mock.NewRows([]string{"id"}).
+		AddRow(1).
+		AddRow(2).
+		AddRow(3).
+		AddRow(4)
+
+	mock.ExpectQuery(`SELECT id WHERE id IN \(\$1, \$2, \$3, \$4\)`).WillReturnRows(r)
+	// nolint:goconst
+	q := "SELECT id WHERE id IN ($1)"
+	v := []int{1, 2, 3, 4}
+	iKeyIDs := make([]interface{}, len(v))
+	for i, d := range v {
+		iKeyIDs[i] = d
+	}
+
+	ctx := context.Background()
+	var result = make([]int, 0)
+	err = RunLimitedVariablesQuery(ctx, q, db, iKeyIDs, limit, func(rows *sql.Rows) error {
+		for rows.Next() {
+			var id int
+			err = rows.Scan(&id)
+			assertNoError(t, err, "rows.Scan returned an error")
+			result = append(result, id)
+		}
+		return nil
+	})
+	assertNoError(t, err, "Call returned an error")
+	if len(result) != len(v) {
+		t.Fatalf("Result should be 4 long")
+	}
+}
+
+func TestShouldReturnCorrectAmountOfResultsIfMoreVariablesThanLimit(t *testing.T) {
+	db, mock, err := sqlmock.New()
+	assertNoError(t, err, "Failed to make DB")
+	limit := uint(4)
+
+	r1 := mock.NewRows([]string{"id"}).
+		AddRow(1).
+		AddRow(2).
+		AddRow(3).
+		AddRow(4)
+
+	r2 := mock.NewRows([]string{"id"}).
+		AddRow(5)
+
+	mock.ExpectQuery(`SELECT id WHERE id IN \(\$1, \$2, \$3, \$4\)`).WillReturnRows(r1)
+	mock.ExpectQuery(`SELECT id WHERE id IN \(\$1\)`).WillReturnRows(r2)
+	// nolint:goconst
+	q := "SELECT id WHERE id IN ($1)"
+	v := []int{1, 2, 3, 4, 5}
+	iKeyIDs := make([]interface{}, len(v))
+	for i, d := range v {
+		iKeyIDs[i] = d
+	}
+
+	ctx := context.Background()
+	var result = make([]int, 0)
+	err = RunLimitedVariablesQuery(ctx, q, db, iKeyIDs, limit, func(rows *sql.Rows) error {
+		for rows.Next() {
+			var id int
+			err = rows.Scan(&id)
+			assertNoError(t, err, "rows.Scan returned an error")
+			result = append(result, id)
+		}
+		return nil
+	})
+	assertNoError(t, err, "Call returned an error")
+	if len(result) != len(v) {
+		t.Fatalf("Result should be 5 long")
+	}
+	if !reflect.DeepEqual(v, result) {
+		t.Fatalf("Result is not as expected: got %v want %v", v, result)
+	}
+}
+
+func TestShouldReturnErrorIfRowsScanReturnsError(t *testing.T) {
+	db, mock, err := sqlmock.New()
+	assertNoError(t, err, "Failed to make DB")
+	limit := uint(4)
+
+	// adding a string ID should result in rows.Scan returning an error
+	r := mock.NewRows([]string{"id"}).
+		AddRow("hej").
+		AddRow(2).
+		AddRow(3)
+
+	mock.ExpectQuery(`SELECT id WHERE id IN \(\$1, \$2, \$3\)`).WillReturnRows(r)
+	// nolint:goconst
+	q := "SELECT id WHERE id IN ($1)"
+	v := []int{-1, -2, 3}
+	iKeyIDs := make([]interface{}, len(v))
+	for i, d := range v {
+		iKeyIDs[i] = d
+	}
+
+	ctx := context.Background()
+	var result = make([]uint, 0)
+	err = RunLimitedVariablesQuery(ctx, q, db, iKeyIDs, limit, func(rows *sql.Rows) error {
+		for rows.Next() {
+			var id uint
+			err = rows.Scan(&id)
+			if err != nil {
+				return err
+			}
+			result = append(result, id)
+		}
+		return nil
+	})
+	if err == nil {
+		t.Fatalf("Call did not return an error")
+	}
+}
+
+func assertNoError(t *testing.T, err error, msg string) {
+	t.Helper()
+	if err == nil {
+		return
+	}
+	t.Fatalf(msg)
+}

internal/test/config.go

@@ -25,6 +25,7 @@ import (
 	"math/big"
 	"os"
 	"path/filepath"
+	"strings"
 	"time"
 
 	"github.com/matrix-org/dendrite/internal/config"
@@ -146,10 +147,14 @@ func NewMatrixKey(matrixKeyPath string) (err error) {
 		err = keyOut.Close()
 	})()
 
+	keyID := base64.RawURLEncoding.EncodeToString(data[:])
+	keyID = strings.ReplaceAll(keyID, "-", "")
+	keyID = strings.ReplaceAll(keyID, "_", "")
+
 	err = pem.Encode(keyOut, &pem.Block{
 		Type: "MATRIX PRIVATE KEY",
 		Headers: map[string]string{
-			"Key-ID": "ed25519:" + base64.RawStdEncoding.EncodeToString(data[:3]),
+			"Key-ID": fmt.Sprintf("ed25519:%s", keyID[:6]),
 		},
 		Bytes: data[3:],
 	})

roomserver/api/api.go

@@ -16,7 +16,7 @@ type RoomserverInternalAPI interface {
 		ctx context.Context,
 		request *InputRoomEventsRequest,
 		response *InputRoomEventsResponse,
-	) error
+	)
 
 	PerformInvite(
 		ctx context.Context,

roomserver/api/api_trace.go

@@ -23,10 +23,9 @@ func (t *RoomserverInternalAPITrace) InputRoomEvents(
 	ctx context.Context,
 	req *InputRoomEventsRequest,
 	res *InputRoomEventsResponse,
-) error {
+) {
-	err := t.Impl.InputRoomEvents(ctx, req, res)
+	t.Impl.InputRoomEvents(ctx, req, res)
-	util.GetLogger(ctx).WithError(err).Infof("InputRoomEvents req=%+v res=%+v", js(req), js(res))
+	util.GetLogger(ctx).Infof("InputRoomEvents req=%+v res=%+v", js(req), js(res))
-	return err
 }
 
 func (t *RoomserverInternalAPITrace) PerformInvite(

roomserver/api/input.go

@@ -16,6 +16,8 @@
 package api
 
 import (
+	"fmt"
+
 	"github.com/matrix-org/gomatrixserverlib"
 )
 
@@ -33,6 +35,10 @@ const (
 	// KindBackfill event extend the contiguous graph going backwards.
 	// They always have state.
 	KindBackfill = 3
+	// KindRewrite events are used when rewriting the head of the room
+	// graph with entirely new state. The output events generated will
+	// be state events rather than timeline events.
+	KindRewrite = 4
 )
 
 // DoNotSendToOtherServers tells us not to send the event to other matrix
@@ -83,4 +89,18 @@ type InputRoomEventsRequest struct {
 
 // InputRoomEventsResponse is a response to InputRoomEvents
 type InputRoomEventsResponse struct {
+	ErrMsg     string // set if there was any error
+	NotAllowed bool   // true if an event in the input was not allowed.
+}
+
+func (r *InputRoomEventsResponse) Err() error {
+	if r.ErrMsg == "" {
+		return nil
+	}
+	if r.NotAllowed {
+		return &gomatrixserverlib.NotAllowed{
+			Message: r.ErrMsg,
+		}
+	}
+	return fmt.Errorf("InputRoomEventsResponse: %s", r.ErrMsg)
 }

roomserver/api/output.go

@@ -68,6 +68,17 @@ type OutputEvent struct {
 	NewPeek *OutputNewPeek `json:"new_peek,omitempty"`
 }
 
+// Type of the OutputNewRoomEvent.
+type OutputRoomEventType int
+
+const (
+	// The event is a timeline event and likely just happened.
+	OutputRoomTimeline OutputRoomEventType = iota
+
+	// The event is a state event and quite possibly happened in the past.
+	OutputRoomState
+)
+
 // An OutputNewRoomEvent is written when the roomserver receives a new event.
 // It contains the full matrix room event and enough information for a
 // consumer to construct the current state of the room and the state before the
@@ -80,6 +91,9 @@ type OutputEvent struct {
 type OutputNewRoomEvent struct {
 	// The Event.
 	Event gomatrixserverlib.HeaderedEvent `json:"event"`
+	// Does the event completely rewrite the room state? If so, then AddsStateEventIDs
+	// will contain the entire room state.
+	RewritesState bool `json:"rewrites_state"`
 	// The latest events in the room after this event.
 	// This can be used to set the prev events for new events in the room.
 	// This also can be used to get the full current state after this event.

roomserver/api/wrapper.go

@@ -80,13 +80,107 @@ func SendEventWithState(
 	return SendInputRoomEvents(ctx, rsAPI, ires)
 }
 
+// SendEventWithRewrite writes an event with KindNew to the roomserver along
+// with a number of rewrite and outlier events for state and auth events
+// respectively.
+func SendEventWithRewrite(
+	ctx context.Context, rsAPI RoomserverInternalAPI, state *gomatrixserverlib.RespState,
+	event gomatrixserverlib.HeaderedEvent, haveEventIDs map[string]bool,
+) error {
+	isCurrentState := map[string]struct{}{}
+	for _, se := range state.StateEvents {
+		isCurrentState[se.EventID()] = struct{}{}
+	}
+
+	authAndStateEvents, err := state.Events()
+	if err != nil {
+		return err
+	}
+
+	var ires []InputRoomEvent
+	var stateIDs []string
+
+	// This function generates three things:
+	// A - A set of "rewrite" events, which will form the newly rewritten
+	//     state before the event, which includes every rewrite event that
+	//     came before it in its state
+	// B - A set of "outlier" events, which are auth events but not part
+	//     of the rewritten state
+	// C - A "new" event, which include all of the rewrite events in its
+	//     state
+	for _, authOrStateEvent := range authAndStateEvents {
+		if authOrStateEvent.StateKey() == nil {
+			continue
+		}
+		if haveEventIDs[authOrStateEvent.EventID()] {
+			continue
+		}
+		if event.StateKey() == nil {
+			continue
+		}
+
+		// We will handle an event as if it's an outlier if one of the
+		// following conditions is true:
+		storeAsOutlier := false
+		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.
+			storeAsOutlier = true
+		}
+
+		if storeAsOutlier {
+			ires = append(ires, InputRoomEvent{
+				Kind:         KindOutlier,
+				Event:        authOrStateEvent.Headered(event.RoomVersion),
+				AuthEventIDs: authOrStateEvent.AuthEventIDs(),
+			})
+			continue
+		}
+
+		// If the event isn't an outlier then we'll instead send it as a
+		// rewrite event, so that it'll form part of the rewritten state.
+		// These events will go through the membership and latest event
+		// updaters and we will generate output events, but they will be
+		// flagged as non-current (i.e. didn't just happen) events.
+		// Each of these rewrite events includes all of the rewrite events
+		// that came before in their StateEventIDs.
+		ires = append(ires, InputRoomEvent{
+			Kind:          KindRewrite,
+			Event:         authOrStateEvent.Headered(event.RoomVersion),
+			AuthEventIDs:  authOrStateEvent.AuthEventIDs(),
+			HasState:      true,
+			StateEventIDs: stateIDs,
+		})
+
+		// Add the event ID into the StateEventIDs of all subsequent
+		// rewrite events, and the new event.
+		stateIDs = append(stateIDs, authOrStateEvent.EventID())
+	}
+
+	// Send the final event as a new event, which will generate
+	// a timeline output event for it. All of the rewrite events
+	// that came before will be sent as StateEventIDs, forming a
+	// new clean state before the event.
+	ires = append(ires, InputRoomEvent{
+		Kind:          KindNew,
+		Event:         event,
+		AuthEventIDs:  event.AuthEventIDs(),
+		HasState:      true,
+		StateEventIDs: stateIDs,
+	})
+
+	return SendInputRoomEvents(ctx, rsAPI, ires)
+}
+
 // SendInputRoomEvents to the roomserver.
 func SendInputRoomEvents(
 	ctx context.Context, rsAPI RoomserverInternalAPI, ires []InputRoomEvent,
 ) error {
 	request := InputRoomEventsRequest{InputRoomEvents: ires}
 	var response InputRoomEventsResponse
-	return rsAPI.InputRoomEvents(ctx, &request, &response)
+	rsAPI.InputRoomEvents(ctx, &request, &response)
+	return response.Err()
 }
 
 // SendInvite event to the roomserver.

roomserver/internal/alias.go

@@ -271,5 +271,6 @@ func (r *RoomserverInternalAPI) sendUpdatedAliasesEvent(
 	var inputRes api.InputRoomEventsResponse
 
 	// Send the request
-	return r.InputRoomEvents(ctx, &inputReq, &inputRes)
+	r.InputRoomEvents(ctx, &inputReq, &inputRes)
+	return inputRes.Err()
 }

roomserver/internal/helpers/auth.go

@@ -16,13 +16,78 @@ package helpers
 
 import (
 	"context"
+	"fmt"
 	"sort"
 
+	"github.com/matrix-org/dendrite/roomserver/state"
 	"github.com/matrix-org/dendrite/roomserver/storage"
 	"github.com/matrix-org/dendrite/roomserver/types"
 	"github.com/matrix-org/gomatrixserverlib"
 )
 
+// CheckForSoftFail returns true if the event should be soft-failed
+// and false otherwise. The return error value should be checked before
+// the soft-fail bool.
+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.
+		var roomInfo *types.RoomInfo
+		roomInfo, err = db.RoomInfo(ctx, event.RoomID())
+		if err != nil {
+			return false, fmt.Errorf("db.RoomNID: %w", err)
+		}
+		if roomInfo == nil || roomInfo.IsStub {
+			return false, nil
+		}
+
+		// 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, 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.
+	// If we're now processing the first create event then never
+	// soft-fail it.
+	if len(authStateEntries) == 0 && event.Type() == gomatrixserverlib.MRoomCreate {
+		return false, nil
+	}
+
+	// Work out which of the state events we actually need.
+	stateNeeded := gomatrixserverlib.StateNeededForAuth([]gomatrixserverlib.Event{event.Unwrap()})
+
+	// Load the actual auth events from the database.
+	authEvents, err := loadAuthEvents(ctx, db, stateNeeded, authStateEntries)
+	if err != nil {
+		return true, fmt.Errorf("loadAuthEvents: %w", err)
+	}
+
+	// Check if the event is allowed.
+	if err = gomatrixserverlib.Allowed(event.Event, &authEvents); err != nil {
+		// return true, nil
+		return true, fmt.Errorf("gomatrixserverlib.Allowed: %w", err)
+	}
+	return false, nil
+}
+
 // CheckAuthEvents checks that the event passes authentication checks
 // Returns the numeric IDs for the auth events.
 func CheckAuthEvents(
@@ -36,7 +101,7 @@ func CheckAuthEvents(
 	if err != nil {
 		return nil, err
 	}
-	// TODO: check for duplicate state keys here.
+	authStateEntries = types.DeduplicateStateEntries(authStateEntries)
 
 	// Work out which of the state events we actually need.
 	stateNeeded := gomatrixserverlib.StateNeededForAuth([]gomatrixserverlib.Event{event.Unwrap()})

roomserver/internal/input/input.go

@@ -110,7 +110,7 @@ func (r *Inputer) InputRoomEvents(
 	ctx context.Context,
 	request *api.InputRoomEventsRequest,
 	response *api.InputRoomEventsResponse,
-) error {
+) {
 	// Create a wait group. Each task that we dispatch will call Done on
 	// this wait group so that we know when all of our events have been
 	// processed.
@@ -156,8 +156,10 @@ func (r *Inputer) InputRoomEvents(
 	// that back to the caller.
 	for _, task := range tasks {
 		if task.err != nil {
-			return task.err
+			response.ErrMsg = task.err.Error()
+			_, rejected := task.err.(*gomatrixserverlib.NotAllowed)
+			response.NotAllowed = rejected
+			return
 		}
 	}
-	return nil
 }

roomserver/internal/input/input_events.go

@@ -46,10 +46,25 @@ func (r *Inputer) processRoomEvent(
 
 	// Check that the event passes authentication checks and work out
 	// the numeric IDs for the auth events.
-	authEventNIDs, err := helpers.CheckAuthEvents(ctx, r.DB, headered, input.AuthEventIDs)
+	isRejected := false
+	authEventNIDs, rejectionErr := helpers.CheckAuthEvents(ctx, r.DB, headered, input.AuthEventIDs)
+	if rejectionErr != nil {
+		logrus.WithError(rejectionErr).WithField("event_id", event.EventID()).WithField("auth_event_ids", input.AuthEventIDs).Error("processRoomEvent.checkAuthEvents failed for event, rejecting event")
+		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, input.StateEventIDs)
 		if err != nil {
-		logrus.WithError(err).WithField("event_id", event.EventID()).WithField("auth_event_ids", input.AuthEventIDs).Error("processRoomEvent.checkAuthEvents failed for event")
+			logrus.WithFields(logrus.Fields{
-		return
+				"event_id": event.EventID(),
+				"type":     event.Type(),
+				"room":     event.RoomID(),
+			}).WithError(err).Info("Error authing soft-failed event")
+		}
 	}
 
 	// If we don't have a transaction ID then get one.
@@ -65,12 +80,13 @@ func (r *Inputer) processRoomEvent(
 	}
 
 	// Store the event.
-	_, stateAtEvent, redactionEvent, redactedEventID, err := r.DB.StoreEvent(ctx, event, input.TransactionID, authEventNIDs)
+	_, stateAtEvent, redactionEvent, redactedEventID, err := r.DB.StoreEvent(ctx, event, input.TransactionID, authEventNIDs, isRejected)
 	if err != nil {
 		return "", fmt.Errorf("r.DB.StoreEvent: %w", err)
 	}
+
 	// if storing this event results in it being redacted then do so.
-	if redactedEventID == event.EventID() {
+	if !isRejected && redactedEventID == event.EventID() {
 		r, rerr := eventutil.RedactEvent(redactionEvent, &event)
 		if rerr != nil {
 			return "", fmt.Errorf("eventutil.RedactEvent: %w", rerr)
@@ -86,7 +102,8 @@ func (r *Inputer) processRoomEvent(
 			"event_id": event.EventID(),
 			"type":     event.Type(),
 			"room":     event.RoomID(),
-		}).Info("Stored outlier")
+			"sender":   event.Sender(),
+		}).Debug("Stored outlier")
 		return event.EventID(), nil
 	}
 
@@ -101,12 +118,33 @@ func (r *Inputer) processRoomEvent(
 	if stateAtEvent.BeforeStateSnapshotNID == 0 {
 		// We haven't calculated a state for this event yet.
 		// Lets calculate one.
-		err = r.calculateAndSetState(ctx, input, *roomInfo, &stateAtEvent, event)
+		err = r.calculateAndSetState(ctx, input, *roomInfo, &stateAtEvent, event, isRejected)
 		if err != nil {
 			return "", fmt.Errorf("r.calculateAndSetState: %w", err)
 		}
 	}
 
+	// We stop here if the event is rejected: We've stored it but won't update forward extremities or notify anyone about it.
+	if isRejected || softfail {
+		logrus.WithFields(logrus.Fields{
+			"event_id":  event.EventID(),
+			"type":      event.Type(),
+			"room":      event.RoomID(),
+			"soft_fail": softfail,
+			"sender":    event.Sender(),
+		}).Debug("Stored rejected event")
+		return event.EventID(), rejectionErr
+	}
+
+	if input.Kind == api.KindRewrite {
+		logrus.WithFields(logrus.Fields{
+			"event_id": event.EventID(),
+			"type":     event.Type(),
+			"room":     event.RoomID(),
+		}).Debug("Stored rewrite")
+		return event.EventID(), nil
+	}
+
 	if err = r.updateLatestEvents(
 		ctx,                 // context
 		roomInfo,            // room info for the room being updated
@@ -114,6 +152,7 @@ func (r *Inputer) processRoomEvent(
 		event,               // event
 		input.SendAsServer,  // send as server
 		input.TransactionID, // transaction ID
+		input.HasState,      // rewrites state?
 	); err != nil {
 		return "", fmt.Errorf("r.updateLatestEvents: %w", err)
 	}
@@ -147,11 +186,12 @@ func (r *Inputer) calculateAndSetState(
 	roomInfo types.RoomInfo,
 	stateAtEvent *types.StateAtEvent,
 	event gomatrixserverlib.Event,
+	isRejected bool,
 ) error {
 	var err error
 	roomState := state.NewStateResolution(r.DB, roomInfo)
 
-	if input.HasState {
+	if input.HasState && !isRejected {
 		// Check here if we think we're in the room already.
 		stateAtEvent.Overwrite = true
 		var joinEventNIDs []types.EventNID
@@ -167,19 +207,25 @@ func (r *Inputer) calculateAndSetState(
 		// Check that those state events are in the database and store the state.
 		var entries []types.StateEntry
 		if entries, err = r.DB.StateEntriesForEventIDs(ctx, input.StateEventIDs); err != nil {
-			return err
+			return fmt.Errorf("r.DB.StateEntriesForEventIDs: %w", err)
 		}
+		entries = types.DeduplicateStateEntries(entries)
 
 		if stateAtEvent.BeforeStateSnapshotNID, err = r.DB.AddState(ctx, roomInfo.RoomNID, nil, entries); err != nil {
-			return err
+			return fmt.Errorf("r.DB.AddState: %w", err)
 		}
 	} else {
 		stateAtEvent.Overwrite = false
 
 		// We haven't been told what the state at the event is so we need to calculate it from the prev_events
-		if stateAtEvent.BeforeStateSnapshotNID, err = roomState.CalculateAndStoreStateBeforeEvent(ctx, event); err != nil {
+		if stateAtEvent.BeforeStateSnapshotNID, err = roomState.CalculateAndStoreStateBeforeEvent(ctx, event, isRejected); err != nil {
-			return err
+			return fmt.Errorf("roomState.CalculateAndStoreStateBeforeEvent: %w", err)
 		}
 	}
-	return r.DB.SetState(ctx, stateAtEvent.EventNID, stateAtEvent.BeforeStateSnapshotNID)
+
+	err = r.DB.SetState(ctx, stateAtEvent.EventNID, stateAtEvent.BeforeStateSnapshotNID)
+	if err != nil {
+		return fmt.Errorf("r.DB.SetState: %w", err)
+	}
+	return nil
 }

roomserver/internal/input/input_latest_events.go

@@ -54,6 +54,7 @@ func (r *Inputer) updateLatestEvents(
 	event gomatrixserverlib.Event,
 	sendAsServer string,
 	transactionID *api.TransactionID,
+	rewritesState bool,
 ) (err error) {
 	updater, err := r.DB.GetLatestEventsForUpdate(ctx, *roomInfo)
 	if err != nil {
@@ -71,6 +72,7 @@ func (r *Inputer) updateLatestEvents(
 		event:         event,
 		sendAsServer:  sendAsServer,
 		transactionID: transactionID,
+		rewritesState: rewritesState,
 	}
 
 	if err = u.doUpdateLatestEvents(); err != nil {
@@ -93,6 +95,7 @@ type latestEventsUpdater struct {
 	stateAtEvent  types.StateAtEvent
 	event         gomatrixserverlib.Event
 	transactionID *api.TransactionID
+	rewritesState bool
 	// Which server to send this event as.
 	sendAsServer string
 	// The eventID of the event that was processed before this one.
@@ -178,7 +181,8 @@ func (u *latestEventsUpdater) doUpdateLatestEvents() error {
 		return fmt.Errorf("u.api.updateMemberships: %w", err)
 	}
 
-	update, err := u.makeOutputNewRoomEvent()
+	var update *api.OutputEvent
+	update, err = u.makeOutputNewRoomEvent()
 	if err != nil {
 		return fmt.Errorf("u.makeOutputNewRoomEvent: %w", err)
 	}
@@ -305,6 +309,7 @@ func (u *latestEventsUpdater) makeOutputNewRoomEvent() (*api.OutputEvent, error)
 
 	ore := api.OutputNewRoomEvent{
 		Event:           u.event.Headered(u.roomInfo.RoomVersion),
+		RewritesState:   u.rewritesState,
 		LastSentEventID: u.lastEventIDSent,
 		LatestEventIDs:  latestEventIDs,
 		TransactionID:   u.transactionID,
@@ -337,6 +342,11 @@ func (u *latestEventsUpdater) makeOutputNewRoomEvent() (*api.OutputEvent, error)
 			return nil, fmt.Errorf("failed to load add_state_events from db: %w", err)
 		}
 	}
+	// State is rewritten if the input room event HasState and we actually produced a delta on state events.
+	// Without this check, /get_missing_events which produce events with associated (but not complete) state
+	// will incorrectly purge the room and set it to no state. TODO: This is likely flakey, as if /gme produced
+	// a state conflict res which just so happens to include 2+ events we might purge the room state downstream.
+	ore.RewritesState = len(ore.AddsStateEventIDs) > 1
 
 	return &api.OutputEvent{
 		Type:         api.OutputTypeNewRoomEvent,

roomserver/internal/perform/perform_backfill.go

@@ -547,7 +547,7 @@ func persistEvents(ctx context.Context, db storage.Database, events []gomatrixse
 		var stateAtEvent types.StateAtEvent
 		var redactedEventID string
 		var redactionEvent *gomatrixserverlib.Event
-		roomNID, stateAtEvent, redactionEvent, redactedEventID, err = db.StoreEvent(ctx, ev.Unwrap(), nil, authNids)
+		roomNID, stateAtEvent, redactionEvent, redactedEventID, err = db.StoreEvent(ctx, ev.Unwrap(), nil, authNids, false)
 		if err != nil {
 			logrus.WithError(err).WithField("event_id", ev.EventID()).Error("Failed to persist event")
 			continue

roomserver/internal/perform/perform_invite.go

@@ -183,7 +183,8 @@ func (r *Inviter) PerformInvite(
 			},
 		}
 		inputRes := &api.InputRoomEventsResponse{}
-		if err = r.Inputer.InputRoomEvents(context.Background(), inputReq, inputRes); err != nil {
+		r.Inputer.InputRoomEvents(context.Background(), inputReq, inputRes)
+		if err = inputRes.Err(); err != nil {
 			return nil, fmt.Errorf("r.InputRoomEvents: %w", err)
 		}
 	} else {

roomserver/internal/perform/perform_join.go

@@ -183,33 +183,33 @@ func (r *Joiner) performJoinRoomByID(
 		return "", fmt.Errorf("eb.SetContent: %w", err)
 	}
 
-	// First work out if this is in response to an existing invite
+	// Force a federated join if we aren't in the room and we've been
-	// from a federated server. If it is then we avoid the situation
+	// given some server names to try joining by.
-	// where we might think we know about a room in the following
-	// section but don't know the latest state as all of our users
-	// have left.
 	serverInRoom, _ := helpers.IsServerCurrentlyInRoom(ctx, r.DB, r.ServerName, req.RoomIDOrAlias)
+	forceFederatedJoin := len(req.ServerNames) > 0 && !serverInRoom
+
+	// Force a federated join if we're dealing with a pending invite
+	// and we aren't in the room.
 	isInvitePending, inviteSender, _, err := helpers.IsInvitePending(ctx, r.DB, req.RoomIDOrAlias, req.UserID)
-	if err == nil && isInvitePending && !serverInRoom {
+	if err == nil && isInvitePending {
-		// Check if there's an invite pending.
 		_, inviterDomain, ierr := gomatrixserverlib.SplitID('@', inviteSender)
 		if ierr != nil {
 			return "", fmt.Errorf("gomatrixserverlib.SplitID: %w", err)
 		}
 
-		// Check that the domain isn't ours. If it's local then we don't
+		// If we were invited by someone from another server then we can
-		// need to do anything as our own copy of the room state will be
+		// assume they are in the room so we can join via them.
-		// up-to-date.
 		if inviterDomain != r.Cfg.Matrix.ServerName {
-			// Add the server of the person who invited us to the server list,
-			// as they should be a fairly good bet.
 			req.ServerNames = append(req.ServerNames, inviterDomain)
-
+			forceFederatedJoin = true
-			// Perform a federated room join.
-			return req.RoomIDOrAlias, r.performFederatedJoinRoomByID(ctx, req)
 		}
 	}
 
+	// If we should do a forced federated join then do that.
+	if forceFederatedJoin {
+		return req.RoomIDOrAlias, r.performFederatedJoinRoomByID(ctx, req)
+	}
+
 	// Try to construct an actual join event from the template.
 	// If this succeeds then it is a sign that the room already exists
 	// locally on the homeserver.
@@ -247,7 +247,8 @@ func (r *Joiner) performJoinRoomByID(
 				},
 			}
 			inputRes := api.InputRoomEventsResponse{}
-			if err = r.Inputer.InputRoomEvents(ctx, &inputReq, &inputRes); err != nil {
+			r.Inputer.InputRoomEvents(ctx, &inputReq, &inputRes)
+			if err = inputRes.Err(); err != nil {
 				var notAllowed *gomatrixserverlib.NotAllowed
 				if errors.As(err, &notAllowed) {
 					return "", &api.PerformError{

roomserver/internal/perform/perform_leave.go

@@ -139,7 +139,8 @@ func (r *Leaver) performLeaveRoomByID(
 		},
 	}
 	inputRes := api.InputRoomEventsResponse{}
-	if err = r.Inputer.InputRoomEvents(ctx, &inputReq, &inputRes); err != nil {
+	r.Inputer.InputRoomEvents(ctx, &inputReq, &inputRes)
+	if err = inputRes.Err(); err != nil {
 		return nil, fmt.Errorf("r.InputRoomEvents: %w", err)
 	}
 

roomserver/internal/query/query.go

@@ -70,6 +70,7 @@ func (r *Queryer) QueryStateAfterEvents(
 	if err != nil {
 		switch err.(type) {
 		case types.MissingEventError:
+			util.GetLogger(ctx).Errorf("QueryStateAfterEvents: MissingEventError: %s", err)
 			return nil
 		default:
 			return err

roomserver/inthttp/client.go

@@ -149,12 +149,15 @@ func (h *httpRoomserverInternalAPI) InputRoomEvents(
 	ctx context.Context,
 	request *api.InputRoomEventsRequest,
 	response *api.InputRoomEventsResponse,
-) error {
+) {
 	span, ctx := opentracing.StartSpanFromContext(ctx, "InputRoomEvents")
 	defer span.Finish()
 
 	apiURL := h.roomserverURL + RoomserverInputRoomEventsPath
-	return httputil.PostJSON(ctx, span, h.httpClient, apiURL, request, response)
+	err := httputil.PostJSON(ctx, span, h.httpClient, apiURL, request, response)
+	if err != nil {
+		response.ErrMsg = err.Error()
+	}
 }
 
 func (h *httpRoomserverInternalAPI) PerformInvite(

roomserver/inthttp/server.go

@@ -20,9 +20,7 @@ func AddRoutes(r api.RoomserverInternalAPI, internalAPIMux *mux.Router) {
 			if err := json.NewDecoder(req.Body).Decode(&request); err != nil {
 				return util.MessageResponse(http.StatusBadRequest, err.Error())
 			}
-			if err := r.InputRoomEvents(req.Context(), &request, &response); err != nil {
+			r.InputRoomEvents(req.Context(), &request, &response)
-				return util.ErrorResponse(err)
-			}
 			return util.JSONResponse{Code: http.StatusOK, JSON: &response}
 		}),
 	)

roomserver/roomserver_test.go

@@ -1,12 +1,15 @@
 package roomserver
 
 import (
+	"bytes"
 	"context"
+	"crypto/ed25519"
 	"encoding/json"
 	"fmt"
 	"os"
 	"reflect"
 	"testing"
+	"time"
 
 	"github.com/Shopify/sarama"
 	"github.com/matrix-org/dendrite/internal/caching"
@@ -80,7 +83,65 @@ func deleteDatabase() {
 	}
 }
 
-func mustLoadEvents(t *testing.T, ver gomatrixserverlib.RoomVersion, events []json.RawMessage) []gomatrixserverlib.HeaderedEvent {
+type fledglingEvent struct {
+	Type     string
+	StateKey *string
+	Content  interface{}
+	Sender   string
+	RoomID   string
+}
+
+func mustCreateEvents(t *testing.T, roomVer gomatrixserverlib.RoomVersion, events []fledglingEvent) (result []gomatrixserverlib.HeaderedEvent) {
+	t.Helper()
+	depth := int64(1)
+	seed := make([]byte, ed25519.SeedSize) // zero seed
+	key := ed25519.NewKeyFromSeed(seed)
+	var prevs []string
+	roomState := make(map[gomatrixserverlib.StateKeyTuple]string) // state -> event ID
+	for _, ev := range events {
+		eb := gomatrixserverlib.EventBuilder{
+			Sender:     ev.Sender,
+			Depth:      depth,
+			Type:       ev.Type,
+			StateKey:   ev.StateKey,
+			RoomID:     ev.RoomID,
+			PrevEvents: prevs,
+		}
+		err := eb.SetContent(ev.Content)
+		if err != nil {
+			t.Fatalf("mustCreateEvent: failed to marshal event content %+v", ev.Content)
+		}
+		stateNeeded, err := gomatrixserverlib.StateNeededForEventBuilder(&eb)
+		if err != nil {
+			t.Fatalf("mustCreateEvent: failed to work out auth_events : %s", err)
+		}
+		var authEvents []string
+		for _, tuple := range stateNeeded.Tuples() {
+			eventID := roomState[tuple]
+			if eventID != "" {
+				authEvents = append(authEvents, eventID)
+			}
+		}
+		eb.AuthEvents = authEvents
+		signedEvent, err := eb.Build(time.Now(), testOrigin, "ed25519:test", key, roomVer)
+		if err != nil {
+			t.Fatalf("mustCreateEvent: failed to sign event: %s", err)
+		}
+		depth++
+		prevs = []string{signedEvent.EventID()}
+		if ev.StateKey != nil {
+			roomState[gomatrixserverlib.StateKeyTuple{
+				EventType: ev.Type,
+				StateKey:  *ev.StateKey,
+			}] = signedEvent.EventID()
+		}
+		result = append(result, signedEvent.Headered(roomVer))
+	}
+	return
+}
+
+func mustLoadRawEvents(t *testing.T, ver gomatrixserverlib.RoomVersion, events []json.RawMessage) []gomatrixserverlib.HeaderedEvent {
+	t.Helper()
 	hs := make([]gomatrixserverlib.HeaderedEvent, len(events))
 	for i := range events {
 		e, err := gomatrixserverlib.NewEventFromTrustedJSON(events[i], false, ver)
@@ -93,7 +154,8 @@ func mustLoadEvents(t *testing.T, ver gomatrixserverlib.RoomVersion, events []js
 	return hs
 }
 
-func mustSendEvents(t *testing.T, ver gomatrixserverlib.RoomVersion, events []json.RawMessage) (api.RoomserverInternalAPI, *dummyProducer, []gomatrixserverlib.HeaderedEvent) {
+func mustCreateRoomserverAPI(t *testing.T) (api.RoomserverInternalAPI, *dummyProducer) {
+	t.Helper()
 	cfg := &config.Dendrite{}
 	cfg.Defaults()
 	cfg.Global.ServerName = testOrigin
@@ -102,7 +164,7 @@ func mustSendEvents(t *testing.T, ver gomatrixserverlib.RoomVersion, events []js
 	dp := &dummyProducer{
 		topic: cfg.Global.Kafka.TopicFor(config.TopicOutputRoomEvent),
 	}
-	cache, err := caching.NewInMemoryLRUCache(true)
+	cache, err := caching.NewInMemoryLRUCache(false)
 	if err != nil {
 		t.Fatalf("failed to make caches: %s", err)
 	}
@@ -112,9 +174,14 @@ func mustSendEvents(t *testing.T, ver gomatrixserverlib.RoomVersion, events []js
 		Cfg:           cfg,
 	}
 
-	rsAPI := NewInternalAPI(base, &test.NopJSONVerifier{})
+	return NewInternalAPI(base, &test.NopJSONVerifier{}), dp
-	hevents := mustLoadEvents(t, ver, events)
+}
-	if err = api.SendEvents(ctx, rsAPI, hevents, testOrigin, nil); err != nil {
+
+func mustSendEvents(t *testing.T, ver gomatrixserverlib.RoomVersion, events []json.RawMessage) (api.RoomserverInternalAPI, *dummyProducer, []gomatrixserverlib.HeaderedEvent) {
+	t.Helper()
+	rsAPI, dp := mustCreateRoomserverAPI(t)
+	hevents := mustLoadRawEvents(t, ver, events)
+	if err := api.SendEvents(ctx, rsAPI, hevents, testOrigin, nil); err != nil {
 		t.Errorf("failed to SendEvents: %s", err)
 	}
 	return rsAPI, dp, hevents
@@ -170,3 +237,163 @@ func TestOutputRedactedEvent(t *testing.T) {
 		}
 	}
 }
+
+// This tests that rewriting state via KindRewrite works correctly.
+// This creates a small room with a create/join/name state, then replays it
+// with a new room name. We expect the output events to contain the original events,
+// followed by a single OutputNewRoomEvent with RewritesState set to true with the
+// rewritten state events (with the 2nd room name).
+func TestOutputRewritesState(t *testing.T) {
+	roomID := "!foo:" + string(testOrigin)
+	alice := "@alice:" + string(testOrigin)
+	emptyKey := ""
+	originalEvents := mustCreateEvents(t, gomatrixserverlib.RoomVersionV6, []fledglingEvent{
+		{
+			RoomID: roomID,
+			Sender: alice,
+			Content: map[string]interface{}{
+				"creator":      alice,
+				"room_version": "6",
+			},
+			StateKey: &emptyKey,
+			Type:     gomatrixserverlib.MRoomCreate,
+		},
+		{
+			RoomID: roomID,
+			Sender: alice,
+			Content: map[string]interface{}{
+				"membership": "join",
+			},
+			StateKey: &alice,
+			Type:     gomatrixserverlib.MRoomMember,
+		},
+		{
+			RoomID: roomID,
+			Sender: alice,
+			Content: map[string]interface{}{
+				"body": "hello world",
+			},
+			StateKey: nil,
+			Type:     "m.room.message",
+		},
+		{
+			RoomID: roomID,
+			Sender: alice,
+			Content: map[string]interface{}{
+				"name": "Room Name",
+			},
+			StateKey: &emptyKey,
+			Type:     "m.room.name",
+		},
+	})
+	rewriteEvents := mustCreateEvents(t, gomatrixserverlib.RoomVersionV6, []fledglingEvent{
+		{
+			RoomID: roomID,
+			Sender: alice,
+			Content: map[string]interface{}{
+				"creator": alice,
+			},
+			StateKey: &emptyKey,
+			Type:     gomatrixserverlib.MRoomCreate,
+		},
+		{
+			RoomID: roomID,
+			Sender: alice,
+			Content: map[string]interface{}{
+				"membership": "join",
+			},
+			StateKey: &alice,
+			Type:     gomatrixserverlib.MRoomMember,
+		},
+		{
+			RoomID: roomID,
+			Sender: alice,
+			Content: map[string]interface{}{
+				"name": "Room Name 2",
+			},
+			StateKey: &emptyKey,
+			Type:     "m.room.name",
+		},
+		{
+			RoomID: roomID,
+			Sender: alice,
+			Content: map[string]interface{}{
+				"body": "hello world 2",
+			},
+			StateKey: nil,
+			Type:     "m.room.message",
+		},
+	})
+	deleteDatabase()
+	rsAPI, producer := mustCreateRoomserverAPI(t)
+	defer deleteDatabase()
+	err := api.SendEvents(context.Background(), rsAPI, originalEvents, testOrigin, nil)
+	if err != nil {
+		t.Fatalf("failed to send original events: %s", err)
+	}
+	// assert we got them produced, this is just a sanity check and isn't the intention of this test
+	if len(producer.producedMessages) != len(originalEvents) {
+		t.Fatalf("SendEvents didn't result in same number of produced output events: got %d want %d", len(producer.producedMessages), len(originalEvents))
+	}
+	producer.producedMessages = nil // we aren't actually interested in these events, just the rewrite ones
+
+	var inputEvents []api.InputRoomEvent
+	// slowly build up the state IDs again, we're basically telling the roomserver what to store as a snapshot
+	var stateIDs []string
+	// skip the last event, we'll use this to tie together the rewrite as the KindNew event
+	for i := 0; i < len(rewriteEvents)-1; i++ {
+		ev := rewriteEvents[i]
+		inputEvents = append(inputEvents, api.InputRoomEvent{
+			Kind:          api.KindRewrite,
+			Event:         ev,
+			AuthEventIDs:  ev.AuthEventIDs(),
+			HasState:      true,
+			StateEventIDs: stateIDs,
+		})
+		if ev.StateKey() != nil {
+			stateIDs = append(stateIDs, ev.EventID())
+		}
+	}
+	lastEv := rewriteEvents[len(rewriteEvents)-1]
+	inputEvents = append(inputEvents, api.InputRoomEvent{
+		Kind:          api.KindNew,
+		Event:         lastEv,
+		AuthEventIDs:  lastEv.AuthEventIDs(),
+		HasState:      true,
+		StateEventIDs: stateIDs,
+	})
+	if err := api.SendInputRoomEvents(context.Background(), rsAPI, inputEvents); err != nil {
+		t.Fatalf("SendInputRoomEvents returned error for rewrite events: %s", err)
+	}
+	// we should just have one output event with the entire state of the room in it
+	if len(producer.producedMessages) != 1 {
+		t.Fatalf("Rewritten events got output, want only 1 got %d", len(producer.producedMessages))
+	}
+	outputEvent := producer.producedMessages[0]
+	if !outputEvent.NewRoomEvent.RewritesState {
+		t.Errorf("RewritesState flag not set on output event")
+	}
+	if !reflect.DeepEqual(stateIDs, outputEvent.NewRoomEvent.AddsStateEventIDs) {
+		t.Errorf("Output event is missing room state event IDs, got %v want %v", outputEvent.NewRoomEvent.AddsStateEventIDs, stateIDs)
+	}
+	if !bytes.Equal(outputEvent.NewRoomEvent.Event.JSON(), lastEv.JSON()) {
+		t.Errorf(
+			"Output event isn't the latest KindNew event:\ngot  %s\nwant %s",
+			string(outputEvent.NewRoomEvent.Event.JSON()),
+			string(lastEv.JSON()),
+		)
+	}
+	if len(outputEvent.NewRoomEvent.AddStateEvents) != len(stateIDs) {
+		t.Errorf("Output event is missing room state events themselves, got %d want %d", len(outputEvent.NewRoomEvent.AddStateEvents), len(stateIDs))
+	}
+	// make sure the state got overwritten, check the room name
+	hasRoomName := false
+	for _, ev := range outputEvent.NewRoomEvent.AddStateEvents {
+		if ev.Type() == "m.room.name" {
+			hasRoomName = string(ev.Content()) == `{"name":"Room Name 2"}`
+		}
+	}
+	if !hasRoomName {
+		t.Errorf("Output event did not overwrite room state")
+	}
+}

roomserver/state/state.go

@@ -159,7 +159,7 @@ func (v StateResolution) LoadCombinedStateAfterEvents(
 			}
 			fullState = append(fullState, entries...)
 		}
-		if prevState.IsStateEvent() {
+		if prevState.IsStateEvent() && !prevState.IsRejected {
 			// If the prev event was a state event then add an entry for the event itself
 			// so that we get the state after the event rather than the state before.
 			fullState = append(fullState, prevState.StateEntry)
@@ -523,6 +523,7 @@ func init() {
 func (v StateResolution) CalculateAndStoreStateBeforeEvent(
 	ctx context.Context,
 	event gomatrixserverlib.Event,
+	isRejected bool,
 ) (types.StateSnapshotNID, error) {
 	// Load the state at the prev events.
 	prevEventRefs := event.PrevEvents()
@@ -561,7 +562,7 @@ func (v StateResolution) CalculateAndStoreStateAfterEvents(
 
 	if len(prevStates) == 1 {
 		prevState := prevStates[0]
-		if prevState.EventStateKeyNID == 0 {
+		if prevState.EventStateKeyNID == 0 || prevState.IsRejected {
 			// 3) None of the previous events were state events and they all
 			// have the same state, so this event has exactly the same state
 			// as the previous events.

roomserver/storage/interface.go

@@ -70,6 +70,7 @@ type Database interface {
 	// Stores a matrix room event in the database. Returns the room NID, the state snapshot and the redacted event ID if any, or an error.
 	StoreEvent(
 		ctx context.Context, event gomatrixserverlib.Event, txnAndSessionID *api.TransactionID, authEventNIDs []types.EventNID,
+		isRejected bool,
 	) (types.RoomNID, types.StateAtEvent, *gomatrixserverlib.Event, string, error)
 	// Look up the state entries for a list of string event IDs
 	// Returns an error if the there is an error talking to the database

roomserver/storage/postgres/events_table.go

@@ -65,13 +65,14 @@ CREATE TABLE IF NOT EXISTS roomserver_events (
     -- Needed for setting reference hashes when sending new events.
     reference_sha256 BYTEA NOT NULL,
     -- A list of numeric IDs for events that can authenticate this event.
-    auth_event_nids BIGINT[] NOT NULL
+	auth_event_nids BIGINT[] NOT NULL,
+	is_rejected BOOLEAN NOT NULL DEFAULT FALSE
 );
 `
 
 const insertEventSQL = "" +
-	"INSERT INTO roomserver_events (room_nid, event_type_nid, event_state_key_nid, event_id, reference_sha256, auth_event_nids, depth)" +
+	"INSERT INTO roomserver_events (room_nid, event_type_nid, event_state_key_nid, event_id, reference_sha256, auth_event_nids, depth, is_rejected)" +
-	" VALUES ($1, $2, $3, $4, $5, $6, $7)" +
+	" VALUES ($1, $2, $3, $4, $5, $6, $7, $8)" +
 	" ON CONFLICT ON CONSTRAINT roomserver_event_id_unique" +
 	" DO NOTHING" +
 	" RETURNING event_nid, state_snapshot_nid"
@@ -88,7 +89,7 @@ const bulkSelectStateEventByIDSQL = "" +
 	" ORDER BY event_type_nid, event_state_key_nid ASC"
 
 const bulkSelectStateAtEventByIDSQL = "" +
-	"SELECT event_type_nid, event_state_key_nid, event_nid, state_snapshot_nid FROM roomserver_events" +
+	"SELECT event_type_nid, event_state_key_nid, event_nid, state_snapshot_nid, is_rejected FROM roomserver_events" +
 	" WHERE event_id = ANY($1)"
 
 const updateEventStateSQL = "" +
@@ -174,12 +175,14 @@ func (s *eventStatements) InsertEvent(
 	referenceSHA256 []byte,
 	authEventNIDs []types.EventNID,
 	depth int64,
+	isRejected bool,
 ) (types.EventNID, types.StateSnapshotNID, error) {
 	var eventNID int64
 	var stateNID int64
 	err := s.insertEventStmt.QueryRowContext(
 		ctx, int64(roomNID), int64(eventTypeNID), int64(eventStateKeyNID),
 		eventID, referenceSHA256, eventNIDsAsArray(authEventNIDs), depth,
+		isRejected,
 	).Scan(&eventNID, &stateNID)
 	return types.EventNID(eventNID), types.StateSnapshotNID(stateNID), err
 }
@@ -255,6 +258,7 @@ func (s *eventStatements) BulkSelectStateAtEventByID(
 			&result.EventStateKeyNID,
 			&result.EventNID,
 			&result.BeforeStateSnapshotNID,
+			&result.IsRejected,
 		); err != nil {
 			return nil, err
 		}

roomserver/storage/shared/storage.go

@@ -320,10 +320,15 @@ func (d *Database) Events(
 		if err != nil {
 			return nil, err
 		}
+		if roomID, ok := d.Cache.GetRoomServerRoomID(roomNID); ok {
+			roomVersion, _ = d.Cache.GetRoomVersion(roomID)
+		}
+		if roomVersion == "" {
 			roomVersion, err = d.RoomsTable.SelectRoomVersionForRoomNID(ctx, roomNID)
 			if err != nil {
 				return nil, err
 			}
+		}
 		result.Event, err = gomatrixserverlib.NewEventFromTrustedJSON(
 			eventJSON.EventJSON, false, roomVersion,
 		)
@@ -382,7 +387,7 @@ func (d *Database) GetLatestEventsForUpdate(
 // nolint:gocyclo
 func (d *Database) StoreEvent(
 	ctx context.Context, event gomatrixserverlib.Event,
-	txnAndSessionID *api.TransactionID, authEventNIDs []types.EventNID,
+	txnAndSessionID *api.TransactionID, authEventNIDs []types.EventNID, isRejected bool,
 ) (types.RoomNID, types.StateAtEvent, *gomatrixserverlib.Event, string, error) {
 	var (
 		roomNID          types.RoomNID
@@ -446,6 +451,7 @@ func (d *Database) StoreEvent(
 			event.EventReference().EventSHA256,
 			authEventNIDs,
 			event.Depth(),
+			isRejected,
 		); err != nil {
 			if err == sql.ErrNoRows {
 				// We've already inserted the event so select the numeric event ID
@@ -459,7 +465,9 @@ func (d *Database) StoreEvent(
 		if err = d.EventJSONTable.InsertEventJSON(ctx, txn, eventNID, event.JSON()); err != nil {
 			return fmt.Errorf("d.EventJSONTable.InsertEventJSON: %w", err)
 		}
+		if !isRejected { // ignore rejected redaction events
 			redactionEvent, redactedEventID, err = d.handleRedactions(ctx, txn, eventNID, event)
+		}
 		return nil
 	})
 	if err != nil {

roomserver/storage/sqlite3/events_table.go

@@ -41,13 +41,14 @@ const eventsSchema = `
     depth INTEGER NOT NULL,
     event_id TEXT NOT NULL UNIQUE,
     reference_sha256 BLOB NOT NULL,
-    auth_event_nids TEXT NOT NULL DEFAULT '[]'
+	auth_event_nids TEXT NOT NULL DEFAULT '[]',
+	is_rejected BOOLEAN NOT NULL DEFAULT FALSE
   );
 `
 
 const insertEventSQL = `
-	INSERT INTO roomserver_events (room_nid, event_type_nid, event_state_key_nid, event_id, reference_sha256, auth_event_nids, depth)
+	INSERT INTO roomserver_events (room_nid, event_type_nid, event_state_key_nid, event_id, reference_sha256, auth_event_nids, depth, is_rejected)
-	  VALUES ($1, $2, $3, $4, $5, $6, $7)
+	  VALUES ($1, $2, $3, $4, $5, $6, $7, $8)
 	  ON CONFLICT DO NOTHING;
 `
 
@@ -63,7 +64,7 @@ const bulkSelectStateEventByIDSQL = "" +
 	" ORDER BY event_type_nid, event_state_key_nid ASC"
 
 const bulkSelectStateAtEventByIDSQL = "" +
-	"SELECT event_type_nid, event_state_key_nid, event_nid, state_snapshot_nid FROM roomserver_events" +
+	"SELECT event_type_nid, event_state_key_nid, event_nid, state_snapshot_nid, is_rejected FROM roomserver_events" +
 	" WHERE event_id IN ($1)"
 
 const updateEventStateSQL = "" +
@@ -150,13 +151,14 @@ func (s *eventStatements) InsertEvent(
 	referenceSHA256 []byte,
 	authEventNIDs []types.EventNID,
 	depth int64,
+	isRejected bool,
 ) (types.EventNID, types.StateSnapshotNID, error) {
 	// attempt to insert: the last_row_id is the event NID
 	var eventNID int64
 	insertStmt := sqlutil.TxStmt(txn, s.insertEventStmt)
 	result, err := insertStmt.ExecContext(
 		ctx, int64(roomNID), int64(eventTypeNID), int64(eventStateKeyNID),
-		eventID, referenceSHA256, eventNIDsAsArray(authEventNIDs), depth,
+		eventID, referenceSHA256, eventNIDsAsArray(authEventNIDs), depth, isRejected,
 	)
 	if err != nil {
 		return 0, 0, err
@@ -261,6 +263,7 @@ func (s *eventStatements) BulkSelectStateAtEventByID(
 			&result.EventStateKeyNID,
 			&result.EventNID,
 			&result.BeforeStateSnapshotNID,
+			&result.IsRejected,
 		); err != nil {
 			return nil, err
 		}

roomserver/storage/sqlite3/previous_events_table.go

@@ -18,6 +18,8 @@ package sqlite3
 import (
 	"context"
 	"database/sql"
+	"fmt"
+	"strings"
 
 	"github.com/matrix-org/dendrite/internal/sqlutil"
 	"github.com/matrix-org/dendrite/roomserver/storage/shared"
@@ -25,10 +27,15 @@ import (
 	"github.com/matrix-org/dendrite/roomserver/types"
 )
 
+// TODO: previous_reference_sha256 was NOT NULL before but it broke sytest because
+// sytest sends no SHA256 sums in the prev_events references in the soft-fail tests.
+// In Postgres an empty BYTEA field is not NULL so it's fine there. In SQLite it
+// seems to care that it's empty and therefore hits a NOT NULL constraint on insert.
+// We should really work out what the right thing to do here is.
 const previousEventSchema = `
   CREATE TABLE IF NOT EXISTS roomserver_previous_events (
     previous_event_id TEXT NOT NULL,
-    previous_reference_sha256 BLOB NOT NULL,
+    previous_reference_sha256 BLOB,
     event_nids TEXT NOT NULL,
     UNIQUE (previous_event_id, previous_reference_sha256)
   );
@@ -45,6 +52,11 @@ const insertPreviousEventSQL = `
 	  VALUES ($1, $2, $3)
 `
 
+const selectPreviousEventNIDsSQL = `
+	SELECT event_nids FROM roomserver_previous_events
+	  WHERE previous_event_id = $1 AND previous_reference_sha256 = $2
+`
+
 // Check if the event is referenced by another event in the table.
 // This should only be done while holding a "FOR UPDATE" lock on the row in the rooms table for this room.
 const selectPreviousEventExistsSQL = `
@@ -55,6 +67,7 @@ const selectPreviousEventExistsSQL = `
 type previousEventStatements struct {
 	db                            *sql.DB
 	insertPreviousEventStmt       *sql.Stmt
+	selectPreviousEventNIDsStmt   *sql.Stmt
 	selectPreviousEventExistsStmt *sql.Stmt
 }
 
@@ -69,6 +82,7 @@ func NewSqlitePrevEventsTable(db *sql.DB) (tables.PreviousEvents, error) {
 
 	return s, shared.StatementList{
 		{&s.insertPreviousEventStmt, insertPreviousEventSQL},
+		{&s.selectPreviousEventNIDsStmt, selectPreviousEventNIDsSQL},
 		{&s.selectPreviousEventExistsStmt, selectPreviousEventExistsSQL},
 	}.Prepare(db)
 }
@@ -80,9 +94,28 @@ func (s *previousEventStatements) InsertPreviousEvent(
 	previousEventReferenceSHA256 []byte,
 	eventNID types.EventNID,
 ) error {
-	stmt := sqlutil.TxStmt(txn, s.insertPreviousEventStmt)
+	var eventNIDs string
-	_, err := stmt.ExecContext(
+	eventNIDAsString := fmt.Sprintf("%d", eventNID)
-		ctx, previousEventID, previousEventReferenceSHA256, int64(eventNID),
+	selectStmt := sqlutil.TxStmt(txn, s.selectPreviousEventExistsStmt)
+	err := selectStmt.QueryRowContext(ctx, previousEventID, previousEventReferenceSHA256).Scan(&eventNIDs)
+	if err != sql.ErrNoRows {
+		return fmt.Errorf("selectStmt.QueryRowContext.Scan: %w", err)
+	}
+	var nids []string
+	if eventNIDs != "" {
+		nids = strings.Split(eventNIDs, ",")
+		for _, nid := range nids {
+			if nid == eventNIDAsString {
+				return nil
+			}
+		}
+		eventNIDs = strings.Join(append(nids, eventNIDAsString), ",")
+	} else {
+		eventNIDs = eventNIDAsString
+	}
+	insertStmt := sqlutil.TxStmt(txn, s.insertPreviousEventStmt)
+	_, err = insertStmt.ExecContext(
+		ctx, previousEventID, previousEventReferenceSHA256, eventNIDs,
 	)
 	return err
 }

roomserver/storage/tables/interface.go

@@ -34,7 +34,10 @@ type EventStateKeys interface {
 }
 
 type Events interface {
-	InsertEvent(c context.Context, txn *sql.Tx, i types.RoomNID, j types.EventTypeNID, k types.EventStateKeyNID, eventID string, referenceSHA256 []byte, authEventNIDs []types.EventNID, depth int64) (types.EventNID, types.StateSnapshotNID, error)
+	InsertEvent(
+		ctx context.Context, txn *sql.Tx, i types.RoomNID, j types.EventTypeNID, k types.EventStateKeyNID, eventID string,
+		referenceSHA256 []byte, authEventNIDs []types.EventNID, depth int64, isRejected bool,
+	) (types.EventNID, types.StateSnapshotNID, error)
 	SelectEvent(ctx context.Context, txn *sql.Tx, eventID string) (types.EventNID, types.StateSnapshotNID, error)
 	// bulkSelectStateEventByID lookups a list of state events by event ID.
 	// If any of the requested events are missing from the database it returns a types.MissingEventError

roomserver/types/types.go

@@ -16,6 +16,8 @@
 package types
 
 import (
+	"sort"
+
 	"github.com/matrix-org/gomatrixserverlib"
 )
 
@@ -72,6 +74,25 @@ func (a StateEntry) LessThan(b StateEntry) bool {
 	return a.EventNID < b.EventNID
 }
 
+// Deduplicate takes a set of state entries and ensures that there are no
+// duplicate (event type, state key) tuples. If there are then we dedupe
+// them, making sure that the latest/highest NIDs are always chosen.
+func DeduplicateStateEntries(a []StateEntry) []StateEntry {
+	if len(a) < 2 {
+		return a
+	}
+	sort.SliceStable(a, func(i, j int) bool {
+		return a[i].LessThan(a[j])
+	})
+	for i := 0; i < len(a)-1; i++ {
+		if a[i].StateKeyTuple == a[i+1].StateKeyTuple {
+			a = append(a[:i], a[i+1:]...)
+			i--
+		}
+	}
+	return a
+}
+
 // StateAtEvent is the state before and after a matrix event.
 type StateAtEvent struct {
 	// Should this state overwrite the latest events and memberships of the room?
@@ -80,6 +101,9 @@ type StateAtEvent struct {
 	Overwrite bool
 	// The state before the event.
 	BeforeStateSnapshotNID StateSnapshotNID
+	// True if this StateEntry is rejected. State resolution should then treat this
+	// StateEntry as being a message event (not a state event).
+	IsRejected bool
 	// The state entry for the event itself, allows us to calculate the state after the event.
 	StateEntry
 }

roomserver/types/types_test.go

@@ -0,0 +1,26 @@
+package types
+
+import (
+	"testing"
+)
+
+func TestDeduplicateStateEntries(t *testing.T) {
+	entries := []StateEntry{
+		{StateKeyTuple{1, 1}, 1},
+		{StateKeyTuple{1, 1}, 2},
+		{StateKeyTuple{1, 1}, 3},
+		{StateKeyTuple{2, 2}, 4},
+		{StateKeyTuple{2, 3}, 5},
+		{StateKeyTuple{3, 3}, 6},
+	}
+	expected := []EventNID{3, 4, 5, 6}
+	entries = DeduplicateStateEntries(entries)
+	if len(entries) != 4 {
+		t.Fatalf("Expected 4 entries, got %d entries", len(entries))
+	}
+	for i, v := range entries {
+		if v.EventNID != expected[i] {
+			t.Fatalf("Expected position %d to be %d but got %d", i, expected[i], v.EventNID)
+		}
+	}
+}

serverkeyapi/internal/api.go

@@ -20,7 +20,7 @@ type ServerKeyAPI struct {
 	ServerKeyValidity time.Duration
 
 	OurKeyRing gomatrixserverlib.KeyRing
-	FedClient  *gomatrixserverlib.FederationClient
+	FedClient  gomatrixserverlib.KeyClient
 }
 
 func (s *ServerKeyAPI) KeyRing() *gomatrixserverlib.KeyRing {

serverkeyapi/serverkeyapi.go

@@ -26,7 +26,7 @@ func AddInternalRoutes(router *mux.Router, intAPI api.ServerKeyInternalAPI, cach
 // can call functions directly on the returned API or via an HTTP interface using AddInternalRoutes.
 func NewInternalAPI(
 	cfg *config.ServerKeyAPI,
-	fedClient *gomatrixserverlib.FederationClient,
+	fedClient gomatrixserverlib.KeyClient,
 	caches *caching.Caches,
 ) api.ServerKeyInternalAPI {
 	innerDB, err := storage.NewDatabase(
@@ -53,7 +53,7 @@ func NewInternalAPI(
 		OurKeyRing: gomatrixserverlib.KeyRing{
 			KeyFetchers: []gomatrixserverlib.KeyFetcher{
 				&gomatrixserverlib.DirectKeyFetcher{
-					Client: fedClient.Client,
+					Client: fedClient,
 				},
 			},
 			KeyDatabase: serverKeyDB,
@@ -65,7 +65,7 @@ func NewInternalAPI(
 		perspective := &gomatrixserverlib.PerspectiveKeyFetcher{
 			PerspectiveServerName: ps.ServerName,
 			PerspectiveServerKeys: map[gomatrixserverlib.KeyID]ed25519.PublicKey{},
-			Client:                fedClient.Client,
+			Client:                fedClient,
 		}
 
 		for _, key := range ps.Keys {

serverkeyapi/storage/sqlite3/server_key_table.go

@@ -18,9 +18,8 @@ package sqlite3
 import (
 	"context"
 	"database/sql"
-	"strings"
+	"fmt"
 
-	"github.com/matrix-org/dendrite/internal"
 	"github.com/matrix-org/dendrite/internal/sqlutil"
 	"github.com/matrix-org/gomatrixserverlib"
 )
@@ -88,41 +87,36 @@ func (s *serverKeyStatements) bulkSelectServerKeys(
 	ctx context.Context,
 	requests map[gomatrixserverlib.PublicKeyLookupRequest]gomatrixserverlib.Timestamp,
 ) (map[gomatrixserverlib.PublicKeyLookupRequest]gomatrixserverlib.PublicKeyLookupResult, error) {
-	var nameAndKeyIDs []string
+	nameAndKeyIDs := make([]string, 0, len(requests))
 	for request := range requests {
 		nameAndKeyIDs = append(nameAndKeyIDs, nameAndKeyID(request))
 	}
-
+	results := make(map[gomatrixserverlib.PublicKeyLookupRequest]gomatrixserverlib.PublicKeyLookupResult, len(requests))
-	query := strings.Replace(bulkSelectServerKeysSQL, "($1)", sqlutil.QueryVariadic(len(nameAndKeyIDs)), 1)
-
 	iKeyIDs := make([]interface{}, len(nameAndKeyIDs))
 	for i, v := range nameAndKeyIDs {
 		iKeyIDs[i] = v
 	}
 
-	rows, err := s.db.QueryContext(ctx, query, iKeyIDs...)
+	err := sqlutil.RunLimitedVariablesQuery(
-	if err != nil {
+		ctx, bulkSelectServerKeysSQL, s.db, iKeyIDs, sqlutil.SQLite3MaxVariables,
-		return nil, err
+		func(rows *sql.Rows) error {
-	}
-	defer internal.CloseAndLogIfError(ctx, rows, "bulkSelectServerKeys: rows.close() failed")
-	results := map[gomatrixserverlib.PublicKeyLookupRequest]gomatrixserverlib.PublicKeyLookupResult{}
 			for rows.Next() {
 				var serverName string
 				var keyID string
 				var key string
 				var validUntilTS int64
 				var expiredTS int64
-		if err = rows.Scan(&serverName, &keyID, &validUntilTS, &expiredTS, &key); err != nil {
+				if err := rows.Scan(&serverName, &keyID, &validUntilTS, &expiredTS, &key); err != nil {
-			return nil, err
+					return fmt.Errorf("bulkSelectServerKeys: %v", err)
 				}
 				r := gomatrixserverlib.PublicKeyLookupRequest{
 					ServerName: gomatrixserverlib.ServerName(serverName),
 					KeyID:      gomatrixserverlib.KeyID(keyID),
 				}
 				vk := gomatrixserverlib.VerifyKey{}
-		err = vk.Key.Decode(key)
+				err := vk.Key.Decode(key)
 				if err != nil {
-			return nil, err
+					return fmt.Errorf("bulkSelectServerKeys: %v", err)
 				}
 				results[r] = gomatrixserverlib.PublicKeyLookupResult{
 					VerifyKey:    vk,
@@ -130,6 +124,13 @@ func (s *serverKeyStatements) bulkSelectServerKeys(
 					ExpiredTS:    gomatrixserverlib.Timestamp(expiredTS),
 				}
 			}
+			return nil
+		},
+	)
+
+	if err != nil {
+		return nil, err
+	}
 	return results, nil
 }
 

syncapi/consumers/roomserver.go

@@ -149,6 +149,12 @@ func (s *OutputRoomEventConsumer) onNewRoomEvent(
 		}
 	}
 
+	if msg.RewritesState {
+		if err = s.db.PurgeRoom(ctx, ev.RoomID()); err != nil {
+			return fmt.Errorf("s.db.PurgeRoom: %w", err)
+		}
+	}
+
 	pduPos, err := s.db.WriteEvent(
 		ctx,
 		&ev,

syncapi/storage/interface.go

@@ -43,6 +43,9 @@ type Database interface {
 	// Returns an error if there was a problem inserting this event.
 	WriteEvent(ctx context.Context, ev *gomatrixserverlib.HeaderedEvent, addStateEvents []gomatrixserverlib.HeaderedEvent,
 		addStateEventIDs []string, removeStateEventIDs []string, transactionID *api.TransactionID, excludeFromSync bool) (types.StreamPosition, error)
+	// PurgeRoom completely purges room state from the sync API. This is done when
+	// receiving an output event that completely resets the state.
+	PurgeRoom(ctx context.Context, roomID string) error
 	// GetStateEvent returns the Matrix state event of a given type for a given room with a given state key
 	// If no event could be found, returns nil
 	// If there was an issue during the retrieval, returns an error

syncapi/storage/postgres/backwards_extremities_table.go

@@ -19,6 +19,7 @@ import (
 	"database/sql"
 
 	"github.com/matrix-org/dendrite/internal"
+	"github.com/matrix-org/dendrite/internal/sqlutil"
 	"github.com/matrix-org/dendrite/syncapi/storage/tables"
 )
 
@@ -46,10 +47,14 @@ const selectBackwardExtremitiesForRoomSQL = "" +
 const deleteBackwardExtremitySQL = "" +
 	"DELETE FROM syncapi_backward_extremities WHERE room_id = $1 AND prev_event_id = $2"
 
+const deleteBackwardExtremitiesForRoomSQL = "" +
+	"DELETE FROM syncapi_backward_extremities WHERE room_id = $1"
+
 type backwardExtremitiesStatements struct {
 	insertBackwardExtremityStmt          *sql.Stmt
 	selectBackwardExtremitiesForRoomStmt *sql.Stmt
 	deleteBackwardExtremityStmt          *sql.Stmt
+	deleteBackwardExtremitiesForRoomStmt *sql.Stmt
 }
 
 func NewPostgresBackwardsExtremitiesTable(db *sql.DB) (tables.BackwardsExtremities, error) {
@@ -67,6 +72,9 @@ func NewPostgresBackwardsExtremitiesTable(db *sql.DB) (tables.BackwardsExtremiti
 	if s.deleteBackwardExtremityStmt, err = db.Prepare(deleteBackwardExtremitySQL); err != nil {
 		return nil, err
 	}
+	if s.deleteBackwardExtremitiesForRoomStmt, err = db.Prepare(deleteBackwardExtremitiesForRoomSQL); err != nil {
+		return nil, err
+	}
 	return s, nil
 }
 
@@ -105,3 +113,10 @@ func (s *backwardExtremitiesStatements) DeleteBackwardExtremity(
 	_, err = txn.Stmt(s.deleteBackwardExtremityStmt).ExecContext(ctx, roomID, knownEventID)
 	return
 }
+
+func (s *backwardExtremitiesStatements) DeleteBackwardExtremitiesForRoom(
+	ctx context.Context, txn *sql.Tx, roomID string,
+) (err error) {
+	_, err = sqlutil.TxStmt(txn, s.deleteBackwardExtremitiesForRoomStmt).ExecContext(ctx, roomID)
+	return err
+}

syncapi/storage/postgres/current_room_state_table.go

@@ -69,6 +69,9 @@ const upsertRoomStateSQL = "" +
 const deleteRoomStateByEventIDSQL = "" +
 	"DELETE FROM syncapi_current_room_state WHERE event_id = $1"
 
+const DeleteRoomStateForRoomSQL = "" +
+	"DELETE FROM syncapi_current_room_state WHERE event_id = $1"
+
 const selectRoomIDsWithMembershipSQL = "" +
 	"SELECT DISTINCT room_id FROM syncapi_current_room_state WHERE type = 'm.room.member' AND state_key = $1 AND membership = $2"
 
@@ -98,6 +101,7 @@ const selectEventsWithEventIDsSQL = "" +
 type currentRoomStateStatements struct {
 	upsertRoomStateStmt             *sql.Stmt
 	deleteRoomStateByEventIDStmt    *sql.Stmt
+	DeleteRoomStateForRoomStmt      *sql.Stmt
 	selectRoomIDsWithMembershipStmt *sql.Stmt
 	selectCurrentStateStmt          *sql.Stmt
 	selectJoinedUsersStmt           *sql.Stmt
@@ -117,6 +121,9 @@ func NewPostgresCurrentRoomStateTable(db *sql.DB) (tables.CurrentRoomState, erro
 	if s.deleteRoomStateByEventIDStmt, err = db.Prepare(deleteRoomStateByEventIDSQL); err != nil {
 		return nil, err
 	}
+	if s.DeleteRoomStateForRoomStmt, err = db.Prepare(DeleteRoomStateForRoomSQL); err != nil {
+		return nil, err
+	}
 	if s.selectRoomIDsWithMembershipStmt, err = db.Prepare(selectRoomIDsWithMembershipSQL); err != nil {
 		return nil, err
 	}
@@ -214,6 +221,14 @@ func (s *currentRoomStateStatements) DeleteRoomStateByEventID(
 	return err
 }
 
+func (s *currentRoomStateStatements) DeleteRoomStateForRoom(
+	ctx context.Context, txn *sql.Tx, roomID string,
+) error {
+	stmt := sqlutil.TxStmt(txn, s.DeleteRoomStateForRoomStmt)
+	_, err := stmt.ExecContext(ctx, roomID)
+	return err
+}
+
 func (s *currentRoomStateStatements) UpsertRoomState(
 	ctx context.Context, txn *sql.Tx,
 	event gomatrixserverlib.HeaderedEvent, membership *string, addedAt types.StreamPosition,

syncapi/storage/postgres/output_room_events_table.go

@@ -115,6 +115,9 @@ const selectStateInRangeSQL = "" +
 	" ORDER BY id ASC" +
 	" LIMIT $8"
 
+const deleteEventsForRoomSQL = "" +
+	"DELETE FROM syncapi_output_room_events WHERE room_id = $1"
+
 type outputRoomEventsStatements struct {
 	insertEventStmt               *sql.Stmt
 	selectEventsStmt              *sql.Stmt
@@ -124,6 +127,7 @@ type outputRoomEventsStatements struct {
 	selectEarlyEventsStmt         *sql.Stmt
 	selectStateInRangeStmt        *sql.Stmt
 	updateEventJSONStmt           *sql.Stmt
+	deleteEventsForRoomStmt       *sql.Stmt
 }
 
 func NewPostgresEventsTable(db *sql.DB) (tables.Events, error) {
@@ -156,6 +160,9 @@ func NewPostgresEventsTable(db *sql.DB) (tables.Events, error) {
 	if s.updateEventJSONStmt, err = db.Prepare(updateEventJSONSQL); err != nil {
 		return nil, err
 	}
+	if s.deleteEventsForRoomStmt, err = db.Prepare(deleteEventsForRoomSQL); err != nil {
+		return nil, err
+	}
 	return s, nil
 }
 
@@ -395,6 +402,13 @@ func (s *outputRoomEventsStatements) SelectEvents(
 	return rowsToStreamEvents(rows)
 }
 
+func (s *outputRoomEventsStatements) DeleteEventsForRoom(
+	ctx context.Context, txn *sql.Tx, roomID string,
+) (err error) {
+	_, err = sqlutil.TxStmt(txn, s.deleteEventsForRoomStmt).ExecContext(ctx, roomID)
+	return err
+}
+
 func rowsToStreamEvents(rows *sql.Rows) ([]types.StreamEvent, error) {
 	var result []types.StreamEvent
 	for rows.Next() {

syncapi/storage/postgres/output_room_events_topology_table.go

@@ -19,6 +19,7 @@ import (
 	"database/sql"
 
 	"github.com/matrix-org/dendrite/internal"
+	"github.com/matrix-org/dendrite/internal/sqlutil"
 	"github.com/matrix-org/dendrite/syncapi/storage/tables"
 	"github.com/matrix-org/dendrite/syncapi/types"
 	"github.com/matrix-org/gomatrixserverlib"
@@ -71,12 +72,16 @@ const selectMaxPositionInTopologySQL = "" +
 	"SELECT MAX(topological_position) FROM syncapi_output_room_events_topology WHERE room_id=$1" +
 	") ORDER BY stream_position DESC LIMIT 1"
 
+const deleteTopologyForRoomSQL = "" +
+	"DELETE FROM syncapi_output_room_events_topology WHERE room_id = $1"
+
 type outputRoomEventsTopologyStatements struct {
 	insertEventInTopologyStmt       *sql.Stmt
 	selectEventIDsInRangeASCStmt    *sql.Stmt
 	selectEventIDsInRangeDESCStmt   *sql.Stmt
 	selectPositionInTopologyStmt    *sql.Stmt
 	selectMaxPositionInTopologyStmt *sql.Stmt
+	deleteTopologyForRoomStmt       *sql.Stmt
 }
 
 func NewPostgresTopologyTable(db *sql.DB) (tables.Topology, error) {
@@ -100,6 +105,9 @@ func NewPostgresTopologyTable(db *sql.DB) (tables.Topology, error) {
 	if s.selectMaxPositionInTopologyStmt, err = db.Prepare(selectMaxPositionInTopologySQL); err != nil {
 		return nil, err
 	}
+	if s.deleteTopologyForRoomStmt, err = db.Prepare(deleteTopologyForRoomSQL); err != nil {
+		return nil, err
+	}
 	return s, nil
 }
 
@@ -167,3 +175,10 @@ func (s *outputRoomEventsTopologyStatements) SelectMaxPositionInTopology(
 	err = s.selectMaxPositionInTopologyStmt.QueryRowContext(ctx, roomID).Scan(&pos, &spos)
 	return
 }
+
+func (s *outputRoomEventsTopologyStatements) DeleteTopologyForRoom(
+	ctx context.Context, txn *sql.Tx, roomID string,
+) (err error) {
+	_, err = sqlutil.TxStmt(txn, s.deleteTopologyForRoomStmt).ExecContext(ctx, roomID)
+	return err
+}

syncapi/storage/shared/syncserver.go

@@ -276,6 +276,29 @@ func (d *Database) handleBackwardExtremities(ctx context.Context, txn *sql.Tx, e
 	return nil
 }
 
+func (d *Database) PurgeRoom(
+	ctx context.Context, roomID string,
+) error {
+	return d.Writer.Do(d.DB, nil, func(txn *sql.Tx) error {
+		// If the event is a create event then we'll delete all of the existing
+		// data for the room. The only reason that a create event would be replayed
+		// to us in this way is if we're about to receive the entire room state.
+		if err := d.CurrentRoomState.DeleteRoomStateForRoom(ctx, txn, roomID); err != nil {
+			return fmt.Errorf("d.CurrentRoomState.DeleteRoomStateForRoom: %w", err)
+		}
+		if err := d.OutputEvents.DeleteEventsForRoom(ctx, txn, roomID); err != nil {
+			return fmt.Errorf("d.Events.DeleteEventsForRoom: %w", err)
+		}
+		if err := d.Topology.DeleteTopologyForRoom(ctx, txn, roomID); err != nil {
+			return fmt.Errorf("d.Topology.DeleteTopologyForRoom: %w", err)
+		}
+		if err := d.BackwardExtremities.DeleteBackwardExtremitiesForRoom(ctx, txn, roomID); err != nil {
+			return fmt.Errorf("d.BackwardExtremities.DeleteBackwardExtremitiesForRoom: %w", err)
+		}
+		return nil
+	})
+}
+
 func (d *Database) WriteEvent(
 	ctx context.Context,
 	ev *gomatrixserverlib.HeaderedEvent,

syncapi/storage/sqlite3/backwards_extremities_table.go

@@ -19,6 +19,7 @@ import (
 	"database/sql"
 
 	"github.com/matrix-org/dendrite/internal"
+	"github.com/matrix-org/dendrite/internal/sqlutil"
 	"github.com/matrix-org/dendrite/syncapi/storage/tables"
 )
 
@@ -46,11 +47,15 @@ const selectBackwardExtremitiesForRoomSQL = "" +
 const deleteBackwardExtremitySQL = "" +
 	"DELETE FROM syncapi_backward_extremities WHERE room_id = $1 AND prev_event_id = $2"
 
+const deleteBackwardExtremitiesForRoomSQL = "" +
+	"DELETE FROM syncapi_backward_extremities WHERE room_id = $1"
+
 type backwardExtremitiesStatements struct {
 	db                                   *sql.DB
 	insertBackwardExtremityStmt          *sql.Stmt
 	selectBackwardExtremitiesForRoomStmt *sql.Stmt
 	deleteBackwardExtremityStmt          *sql.Stmt
+	deleteBackwardExtremitiesForRoomStmt *sql.Stmt
 }
 
 func NewSqliteBackwardsExtremitiesTable(db *sql.DB) (tables.BackwardsExtremities, error) {
@@ -70,6 +75,9 @@ func NewSqliteBackwardsExtremitiesTable(db *sql.DB) (tables.BackwardsExtremities
 	if s.deleteBackwardExtremityStmt, err = db.Prepare(deleteBackwardExtremitySQL); err != nil {
 		return nil, err
 	}
+	if s.deleteBackwardExtremitiesForRoomStmt, err = db.Prepare(deleteBackwardExtremitiesForRoomSQL); err != nil {
+		return nil, err
+	}
 	return s, nil
 }
 
@@ -108,3 +116,10 @@ func (s *backwardExtremitiesStatements) DeleteBackwardExtremity(
 	_, err = txn.Stmt(s.deleteBackwardExtremityStmt).ExecContext(ctx, roomID, knownEventID)
 	return err
 }
+
+func (s *backwardExtremitiesStatements) DeleteBackwardExtremitiesForRoom(
+	ctx context.Context, txn *sql.Tx, roomID string,
+) (err error) {
+	_, err = sqlutil.TxStmt(txn, s.deleteBackwardExtremitiesForRoomStmt).ExecContext(ctx, roomID)
+	return err
+}

syncapi/storage/sqlite3/current_room_state_table.go

@@ -51,12 +51,15 @@ CREATE UNIQUE INDEX IF NOT EXISTS syncapi_event_id_idx ON syncapi_current_room_s
 const upsertRoomStateSQL = "" +
 	"INSERT INTO syncapi_current_room_state (room_id, event_id, type, sender, contains_url, state_key, headered_event_json, membership, added_at)" +
 	" VALUES ($1, $2, $3, $4, $5, $6, $7, $8, $9)" +
-	" ON CONFLICT (event_id, room_id, type, sender, contains_url)" +
+	" ON CONFLICT (room_id, type, state_key)" +
 	" DO UPDATE SET event_id = $2, sender=$4, contains_url=$5, headered_event_json = $7, membership = $8, added_at = $9"
 
 const deleteRoomStateByEventIDSQL = "" +
 	"DELETE FROM syncapi_current_room_state WHERE event_id = $1"
 
+const DeleteRoomStateForRoomSQL = "" +
+	"DELETE FROM syncapi_current_room_state WHERE event_id = $1"
+
 const selectRoomIDsWithMembershipSQL = "" +
 	"SELECT DISTINCT room_id FROM syncapi_current_room_state WHERE type = 'm.room.member' AND state_key = $1 AND membership = $2"
 
@@ -88,6 +91,7 @@ type currentRoomStateStatements struct {
 	streamIDStatements              *streamIDStatements
 	upsertRoomStateStmt             *sql.Stmt
 	deleteRoomStateByEventIDStmt    *sql.Stmt
+	DeleteRoomStateForRoomStmt      *sql.Stmt
 	selectRoomIDsWithMembershipStmt *sql.Stmt
 	selectCurrentStateStmt          *sql.Stmt
 	selectJoinedUsersStmt           *sql.Stmt
@@ -109,6 +113,9 @@ func NewSqliteCurrentRoomStateTable(db *sql.DB, streamID *streamIDStatements) (t
 	if s.deleteRoomStateByEventIDStmt, err = db.Prepare(deleteRoomStateByEventIDSQL); err != nil {
 		return nil, err
 	}
+	if s.DeleteRoomStateForRoomStmt, err = db.Prepare(DeleteRoomStateForRoomSQL); err != nil {
+		return nil, err
+	}
 	if s.selectRoomIDsWithMembershipStmt, err = db.Prepare(selectRoomIDsWithMembershipSQL); err != nil {
 		return nil, err
 	}
@@ -203,6 +210,14 @@ func (s *currentRoomStateStatements) DeleteRoomStateByEventID(
 	return err
 }
 
+func (s *currentRoomStateStatements) DeleteRoomStateForRoom(
+	ctx context.Context, txn *sql.Tx, roomID string,
+) error {
+	stmt := sqlutil.TxStmt(txn, s.DeleteRoomStateForRoomStmt)
+	_, err := stmt.ExecContext(ctx, roomID)
+	return err
+}
+
 func (s *currentRoomStateStatements) UpsertRoomState(
 	ctx context.Context, txn *sql.Tx,
 	event gomatrixserverlib.HeaderedEvent, membership *string, addedAt types.StreamPosition,

syncapi/storage/sqlite3/output_room_events_table.go

@@ -103,6 +103,9 @@ const selectStateInRangeSQL = "" +
 	" ORDER BY id ASC" +
 	" LIMIT $8" // limit
 
+const deleteEventsForRoomSQL = "" +
+	"DELETE FROM syncapi_output_room_events WHERE room_id = $1"
+
 type outputRoomEventsStatements struct {
 	db                            *sql.DB
 	streamIDStatements            *streamIDStatements
@@ -114,6 +117,7 @@ type outputRoomEventsStatements struct {
 	selectEarlyEventsStmt         *sql.Stmt
 	selectStateInRangeStmt        *sql.Stmt
 	updateEventJSONStmt           *sql.Stmt
+	deleteEventsForRoomStmt       *sql.Stmt
 }
 
 func NewSqliteEventsTable(db *sql.DB, streamID *streamIDStatements) (tables.Events, error) {
@@ -149,6 +153,9 @@ func NewSqliteEventsTable(db *sql.DB, streamID *streamIDStatements) (tables.Even
 	if s.updateEventJSONStmt, err = db.Prepare(updateEventJSONSQL); err != nil {
 		return nil, err
 	}
+	if s.deleteEventsForRoomStmt, err = db.Prepare(deleteEventsForRoomSQL); err != nil {
+		return nil, err
+	}
 	return s, nil
 }
 
@@ -410,6 +417,13 @@ func (s *outputRoomEventsStatements) SelectEvents(
 	return returnEvents, nil
 }
 
+func (s *outputRoomEventsStatements) DeleteEventsForRoom(
+	ctx context.Context, txn *sql.Tx, roomID string,
+) (err error) {
+	_, err = sqlutil.TxStmt(txn, s.deleteEventsForRoomStmt).ExecContext(ctx, roomID)
+	return err
+}
+
 func rowsToStreamEvents(rows *sql.Rows) ([]types.StreamEvent, error) {
 	var result []types.StreamEvent
 	for rows.Next() {

syncapi/storage/sqlite3/output_room_events_topology_table.go

@@ -65,6 +65,9 @@ const selectMaxPositionInTopologySQL = "" +
 	"SELECT MAX(topological_position), stream_position FROM syncapi_output_room_events_topology" +
 	" WHERE room_id = $1 ORDER BY stream_position DESC"
 
+const deleteTopologyForRoomSQL = "" +
+	"DELETE FROM syncapi_output_room_events_topology WHERE room_id = $1"
+
 type outputRoomEventsTopologyStatements struct {
 	db                              *sql.DB
 	insertEventInTopologyStmt       *sql.Stmt
@@ -72,6 +75,7 @@ type outputRoomEventsTopologyStatements struct {
 	selectEventIDsInRangeDESCStmt   *sql.Stmt
 	selectPositionInTopologyStmt    *sql.Stmt
 	selectMaxPositionInTopologyStmt *sql.Stmt
+	deleteTopologyForRoomStmt       *sql.Stmt
 }
 
 func NewSqliteTopologyTable(db *sql.DB) (tables.Topology, error) {
@@ -97,6 +101,9 @@ func NewSqliteTopologyTable(db *sql.DB) (tables.Topology, error) {
 	if s.selectMaxPositionInTopologyStmt, err = db.Prepare(selectMaxPositionInTopologySQL); err != nil {
 		return nil, err
 	}
+	if s.deleteTopologyForRoomStmt, err = db.Prepare(deleteTopologyForRoomSQL); err != nil {
+		return nil, err
+	}
 	return s, nil
 }
 
@@ -164,3 +171,10 @@ func (s *outputRoomEventsTopologyStatements) SelectMaxPositionInTopology(
 	err = stmt.QueryRowContext(ctx, roomID).Scan(&pos, &spos)
 	return
 }
+
+func (s *outputRoomEventsTopologyStatements) DeleteTopologyForRoom(
+	ctx context.Context, txn *sql.Tx, roomID string,
+) (err error) {
+	_, err = sqlutil.TxStmt(txn, s.deleteTopologyForRoomStmt).ExecContext(ctx, roomID)
+	return err
+}

syncapi/storage/tables/interface.go

@@ -60,6 +60,8 @@ type Events interface {
 	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
+	// DeleteEventsForRoom removes all event information for a room. This should only be done when removing the room entirely.
+	DeleteEventsForRoom(ctx context.Context, txn *sql.Tx, roomID string) (err error)
 }
 
 // Topology keeps track of the depths and stream positions for all events.
@@ -77,6 +79,8 @@ type Topology interface {
 	SelectPositionInTopology(ctx context.Context, txn *sql.Tx, eventID string) (depth, spos types.StreamPosition, err error)
 	// SelectMaxPositionInTopology returns the event which has the highest depth, and if there are multiple, the event with the highest stream position.
 	SelectMaxPositionInTopology(ctx context.Context, txn *sql.Tx, roomID string) (depth types.StreamPosition, spos types.StreamPosition, err error)
+	// DeleteTopologyForRoom removes all topological information for a room. This should only be done when removing the room entirely.
+	DeleteTopologyForRoom(ctx context.Context, txn *sql.Tx, roomID string) (err error)
 }
 
 type CurrentRoomState interface {
@@ -84,6 +88,7 @@ type CurrentRoomState interface {
 	SelectEventsWithEventIDs(ctx context.Context, txn *sql.Tx, eventIDs []string) ([]types.StreamEvent, error)
 	UpsertRoomState(ctx context.Context, txn *sql.Tx, event gomatrixserverlib.HeaderedEvent, membership *string, addedAt types.StreamPosition) error
 	DeleteRoomStateByEventID(ctx context.Context, txn *sql.Tx, eventID string) error
+	DeleteRoomStateForRoom(ctx context.Context, txn *sql.Tx, roomID string) error
 	// SelectCurrentState returns all the current state events for the given room.
 	SelectCurrentState(ctx context.Context, txn *sql.Tx, roomID string, stateFilter *gomatrixserverlib.StateFilter) ([]gomatrixserverlib.HeaderedEvent, error)
 	// SelectRoomIDsWithMembership returns the list of room IDs which have the given user in the given membership state.
@@ -118,6 +123,8 @@ type BackwardsExtremities interface {
 	SelectBackwardExtremitiesForRoom(ctx context.Context, roomID string) (bwExtrems map[string][]string, err error)
 	// DeleteBackwardExtremity removes a backwards extremity for a room, if one existed.
 	DeleteBackwardExtremity(ctx context.Context, txn *sql.Tx, roomID, knownEventID string) (err error)
+	// DeleteBackwardExtremitiesFoorRoomID removes all backward extremities for a room. This should only be done when removing the room entirely.
+	DeleteBackwardExtremitiesForRoom(ctx context.Context, txn *sql.Tx, roomID string) (err error)
 }
 
 // SendToDevice tracks send-to-device messages which are sent to individual

sytest-blacklist

@@ -40,11 +40,6 @@ Ignore invite in incremental sync
 New room members see their own join event
 Existing members see new members' join events
 
-# Blacklisted because the federation work for these hasn't been finished yet. 
-Can recv device messages over federation
-Device messages over federation wake up /sync
-Wildcard device messages over federation wake up /sync
-
 # See https://github.com/matrix-org/sytest/pull/901
 Remote invited user can see room metadata
 
@@ -56,8 +51,5 @@ Inbound federation accepts a second soft-failed event
 # Caused by https://github.com/matrix-org/sytest/pull/911
 Outbound federation requests missing prev_events and then asks for /state_ids and resolves the state
 
-# We don't implement device lists yet
-Device list doesn't change if remote server is down
-
 # We don't implement lazy membership loading yet.
 The only membership state included in a gapped incremental sync is for senders in the timeline

sytest-whitelist

@@ -471,3 +471,9 @@ We can't peek into rooms with invited history_visibility
 We can't peek into rooms with joined history_visibility
 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
+Federation key API can act as a notary server via a POST request
+Federation key API can act as a notary server via a GET request