Initial support for multiple server names (#2829)

This PR is the first step towards virtual hosting by laying the
groundwork for multiple server names being configured.

46 files changed, 291 insertions, 155 deletions

diff --git a/clientapi/auth/password.go b/clientapi/auth/password.go
index 890b1818..700a72f5 100644
--- a/clientapi/auth/password.go
+++ b/clientapi/auth/password.go
@@ -74,7 +74,7 @@ func (t *LoginTypePassword) Login(ctx context.Context, req interface{}) (*Login,
 			JSON: jsonerror.BadJSON("A password must be supplied."),
 		}
 	}
-	localpart, err := userutil.ParseUsernameParam(username, &t.Config.Matrix.ServerName)
+	localpart, _, err := userutil.ParseUsernameParam(username, t.Config.Matrix)
 	if err != nil {
 		return nil, &util.JSONResponse{
 			Code: http.StatusUnauthorized,
diff --git a/clientapi/routing/admin.go b/clientapi/routing/admin.go
index 89c269f1..69bca13b 100644
--- a/clientapi/routing/admin.go
+++ b/clientapi/routing/admin.go
@@ -70,7 +70,7 @@ func AdminEvacuateUser(req *http.Request, cfg *config.ClientAPI, device *userapi
 	if err != nil {
 		return util.MessageResponse(http.StatusBadRequest, err.Error())
 	}
-	if domain != cfg.Matrix.ServerName {
+	if !cfg.Matrix.IsLocalServerName(domain) {
 		return util.JSONResponse{
 			Code: http.StatusBadRequest,
 			JSON: jsonerror.MissingArgument("User ID must belong to this server."),
@@ -169,7 +169,7 @@ func AdminMarkAsStale(req *http.Request, cfg *config.ClientAPI, keyAPI api.Clien
 	if err != nil {
 		return util.MessageResponse(http.StatusBadRequest, err.Error())
 	}
-	if domain == cfg.Matrix.ServerName {
+	if cfg.Matrix.IsLocalServerName(domain) {
 		return util.JSONResponse{
 			Code: http.StatusBadRequest,
 			JSON: jsonerror.InvalidParam("Can not mark local device list as stale"),
diff --git a/clientapi/routing/createroom.go b/clientapi/routing/createroom.go
index 3e837c86..eefe8e24 100644
--- a/clientapi/routing/createroom.go
+++ b/clientapi/routing/createroom.go
@@ -169,9 +169,21 @@ func createRoom(
 	asAPI appserviceAPI.AppServiceInternalAPI,
 	evTime time.Time,
 ) util.JSONResponse {
+	_, userDomain, err := gomatrixserverlib.SplitID('@', device.UserID)
+	if err != nil {
+		util.GetLogger(ctx).WithError(err).Error("gomatrixserverlib.SplitID failed")
+		return jsonerror.InternalServerError()
+	}
+	if !cfg.Matrix.IsLocalServerName(userDomain) {
+		return util.JSONResponse{
+			Code: http.StatusForbidden,
+			JSON: jsonerror.Forbidden(fmt.Sprintf("User domain %q not configured locally", userDomain)),
+		}
+	}
+
 	// TODO (#267): Check room ID doesn't clash with an existing one, and we
 	//              probably shouldn't be using pseudo-random strings, maybe GUIDs?
-	roomID := fmt.Sprintf("!%s:%s", util.RandomString(16), cfg.Matrix.ServerName)
+	roomID := fmt.Sprintf("!%s:%s", util.RandomString(16), userDomain)
 
 	logger := util.GetLogger(ctx)
 	userID := device.UserID
@@ -314,7 +326,7 @@ func createRoom(
 
 	var roomAlias string
 	if r.RoomAliasName != "" {
-		roomAlias = fmt.Sprintf("#%s:%s", r.RoomAliasName, cfg.Matrix.ServerName)
+		roomAlias = fmt.Sprintf("#%s:%s", r.RoomAliasName, userDomain)
 		// check it's free TODO: This races but is better than nothing
 		hasAliasReq := roomserverAPI.GetRoomIDForAliasRequest{
 			Alias:              roomAlias,
@@ -436,7 +448,7 @@ func createRoom(
 			builder.PrevEvents = []gomatrixserverlib.EventReference{builtEvents[i-1].EventReference()}
 		}
 		var ev *gomatrixserverlib.Event
-		ev, err = buildEvent(&builder, &authEvents, cfg, evTime, roomVersion)
+		ev, err = buildEvent(&builder, userDomain, &authEvents, cfg, evTime, roomVersion)
 		if err != nil {
 			util.GetLogger(ctx).WithError(err).Error("buildEvent failed")
 			return jsonerror.InternalServerError()
@@ -461,7 +473,7 @@ func createRoom(
 		inputs = append(inputs, roomserverAPI.InputRoomEvent{
 			Kind:         roomserverAPI.KindNew,
 			Event:        event,
-			Origin:       cfg.Matrix.ServerName,
+			Origin:       userDomain,
 			SendAsServer: roomserverAPI.DoNotSendToOtherServers,
 		})
 	}
@@ -548,7 +560,7 @@ func createRoom(
 				Event:           event,
 				InviteRoomState: inviteStrippedState,
 				RoomVersion:     event.RoomVersion,
-				SendAsServer:    string(cfg.Matrix.ServerName),
+				SendAsServer:    string(userDomain),
 			}, &inviteRes); err != nil {
 				util.GetLogger(ctx).WithError(err).Error("PerformInvite failed")
 				return util.JSONResponse{
@@ -591,6 +603,7 @@ func createRoom(
 // buildEvent fills out auth_events for the builder then builds the event
 func buildEvent(
 	builder *gomatrixserverlib.EventBuilder,
+	serverName gomatrixserverlib.ServerName,
 	provider gomatrixserverlib.AuthEventProvider,
 	cfg *config.ClientAPI,
 	evTime time.Time,
@@ -606,7 +619,7 @@ func buildEvent(
 	}
 	builder.AuthEvents = refs
 	event, err := builder.Build(
-		evTime, cfg.Matrix.ServerName, cfg.Matrix.KeyID,
+		evTime, serverName, cfg.Matrix.KeyID,
 		cfg.Matrix.PrivateKey, roomVersion,
 	)
 	if err != nil {
diff --git a/clientapi/routing/directory.go b/clientapi/routing/directory.go
index 836d9e15..33bc63d1 100644
--- a/clientapi/routing/directory.go
+++ b/clientapi/routing/directory.go
@@ -75,7 +75,7 @@ func DirectoryRoom(
 	if res.RoomID == "" {
 		// If we don't know it locally, do a federation query.
 		// But don't send the query to ourselves.
-		if domain != cfg.Matrix.ServerName {
+		if !cfg.Matrix.IsLocalServerName(domain) {
 			fedRes, fedErr := federation.LookupRoomAlias(req.Context(), domain, roomAlias)
 			if fedErr != nil {
 				// TODO: Return 502 if the remote server errored.
@@ -127,7 +127,7 @@ func SetLocalAlias(
 		}
 	}
 
-	if domain != cfg.Matrix.ServerName {
+	if !cfg.Matrix.IsLocalServerName(domain) {
 		return util.JSONResponse{
 			Code: http.StatusForbidden,
 			JSON: jsonerror.Forbidden("Alias must be on local homeserver"),
diff --git a/clientapi/routing/directory_public.go b/clientapi/routing/directory_public.go
index 8ddb3267..4ebf2295 100644
--- a/clientapi/routing/directory_public.go
+++ b/clientapi/routing/directory_public.go
@@ -62,8 +62,7 @@ func GetPostPublicRooms(
 	}
 
 	serverName := gomatrixserverlib.ServerName(request.Server)
-
-	if serverName != "" && serverName != cfg.Matrix.ServerName {
+	if serverName != "" && !cfg.Matrix.IsLocalServerName(serverName) {
 		res, err := federation.GetPublicRoomsFiltered(
 			req.Context(), serverName,
 			int(request.Limit), request.Since,
diff --git a/clientapi/routing/login.go b/clientapi/routing/login.go
index 6017b584..7f5a8c4f 100644
--- a/clientapi/routing/login.go
+++ b/clientapi/routing/login.go
@@ -68,7 +68,7 @@ func Login(
 			return *authErr
 		}
 		// make a device/access token
-		authErr2 := completeAuth(req.Context(), cfg.Matrix.ServerName, userAPI, login, req.RemoteAddr, req.UserAgent())
+		authErr2 := completeAuth(req.Context(), cfg.Matrix, userAPI, login, req.RemoteAddr, req.UserAgent())
 		cleanup(req.Context(), &authErr2)
 		return authErr2
 	}
@@ -79,7 +79,7 @@ func Login(
 }
 
 func completeAuth(
-	ctx context.Context, serverName gomatrixserverlib.ServerName, userAPI userapi.ClientUserAPI, login *auth.Login,
+	ctx context.Context, cfg *config.Global, userAPI userapi.ClientUserAPI, login *auth.Login,
 	ipAddr, userAgent string,
 ) util.JSONResponse {
 	token, err := auth.GenerateAccessToken()
@@ -88,7 +88,7 @@ func completeAuth(
 		return jsonerror.InternalServerError()
 	}
 
-	localpart, err := userutil.ParseUsernameParam(login.Username(), &serverName)
+	localpart, serverName, err := userutil.ParseUsernameParam(login.Username(), cfg)
 	if err != nil {
 		util.GetLogger(ctx).WithError(err).Error("auth.ParseUsernameParam failed")
 		return jsonerror.InternalServerError()
diff --git a/clientapi/routing/membership.go b/clientapi/routing/membership.go
index 77f627eb..94ba17a0 100644
--- a/clientapi/routing/membership.go
+++ b/clientapi/routing/membership.go
@@ -105,12 +105,13 @@ func sendMembership(ctx context.Context, profileAPI userapi.ClientUserAPI, devic
 		return jsonerror.InternalServerError()
 	}
 
+	serverName := device.UserDomain()
 	if err = roomserverAPI.SendEvents(
 		ctx, rsAPI,
 		roomserverAPI.KindNew,
 		[]*gomatrixserverlib.HeaderedEvent{event.Event.Headered(roomVer)},
-		cfg.Matrix.ServerName,
-		cfg.Matrix.ServerName,
+		serverName,
+		serverName,
 		nil,
 		false,
 	); err != nil {
@@ -271,7 +272,7 @@ func sendInvite(
 		Event:           event,
 		InviteRoomState: nil, // ask the roomserver to draw up invite room state for us
 		RoomVersion:     event.RoomVersion,
-		SendAsServer:    string(cfg.Matrix.ServerName),
+		SendAsServer:    string(device.UserDomain()),
 	}, &inviteRes); err != nil {
 		util.GetLogger(ctx).WithError(err).Error("PerformInvite failed")
 		return util.JSONResponse{
@@ -341,7 +342,7 @@ func loadProfile(
 	}
 
 	var profile *authtypes.Profile
-	if serverName == cfg.Matrix.ServerName {
+	if cfg.Matrix.IsLocalServerName(serverName) {
 		profile, err = appserviceAPI.RetrieveUserProfile(ctx, userID, asAPI, profileAPI)
 	} else {
 		profile = &authtypes.Profile{}
diff --git a/clientapi/routing/openid.go b/clientapi/routing/openid.go
index cfb440be..8e9be788 100644
--- a/clientapi/routing/openid.go
+++ b/clientapi/routing/openid.go
@@ -63,7 +63,7 @@ func CreateOpenIDToken(
 		JSON: openIDTokenResponse{
 			AccessToken:      response.Token.Token,
 			TokenType:        "Bearer",
-			MatrixServerName: string(cfg.Matrix.ServerName),
+			MatrixServerName: string(device.UserDomain()),
 			ExpiresIn:        response.Token.ExpiresAtMS / 1000, // convert ms to s
 		},
 	}
diff --git a/clientapi/routing/profile.go b/clientapi/routing/profile.go
index c9647eb1..4d9e1f8a 100644
--- a/clientapi/routing/profile.go
+++ b/clientapi/routing/profile.go
@@ -113,12 +113,19 @@ func SetAvatarURL(
 		}
 	}
 
-	localpart, _, err := gomatrixserverlib.SplitID('@', userID)
+	localpart, domain, err := gomatrixserverlib.SplitID('@', userID)
 	if err != nil {
 		util.GetLogger(req.Context()).WithError(err).Error("gomatrixserverlib.SplitID failed")
 		return jsonerror.InternalServerError()
 	}
 
+	if !cfg.Matrix.IsLocalServerName(domain) {
+		return util.JSONResponse{
+			Code: http.StatusForbidden,
+			JSON: jsonerror.Forbidden("userID does not belong to a locally configured domain"),
+		}
+	}
+
 	evTime, err := httputil.ParseTSParam(req)
 	if err != nil {
 		return util.JSONResponse{
@@ -129,8 +136,9 @@ func SetAvatarURL(
 
 	setRes := &userapi.PerformSetAvatarURLResponse{}
 	if err = profileAPI.SetAvatarURL(req.Context(), &userapi.PerformSetAvatarURLRequest{
-		Localpart: localpart,
-		AvatarURL: r.AvatarURL,
+		Localpart:  localpart,
+		ServerName: domain,
+		AvatarURL:  r.AvatarURL,
 	}, setRes); err != nil {
 		util.GetLogger(req.Context()).WithError(err).Error("profileAPI.SetAvatarURL failed")
 		return jsonerror.InternalServerError()
@@ -204,12 +212,19 @@ func SetDisplayName(
 		}
 	}
 
-	localpart, _, err := gomatrixserverlib.SplitID('@', userID)
+	localpart, domain, err := gomatrixserverlib.SplitID('@', userID)
 	if err != nil {
 		util.GetLogger(req.Context()).WithError(err).Error("gomatrixserverlib.SplitID failed")
 		return jsonerror.InternalServerError()
 	}
 
+	if !cfg.Matrix.IsLocalServerName(domain) {
+		return util.JSONResponse{
+			Code: http.StatusForbidden,
+			JSON: jsonerror.Forbidden("userID does not belong to a locally configured domain"),
+		}
+	}
+
 	evTime, err := httputil.ParseTSParam(req)
 	if err != nil {
 		return util.JSONResponse{
@@ -221,6 +236,7 @@ func SetDisplayName(
 	profileRes := &userapi.PerformUpdateDisplayNameResponse{}
 	err = profileAPI.SetDisplayName(req.Context(), &userapi.PerformUpdateDisplayNameRequest{
 		Localpart:   localpart,
+		ServerName:  domain,
 		DisplayName: r.DisplayName,
 	}, profileRes)
 	if err != nil {
@@ -261,6 +277,12 @@ func updateProfile(
 		return jsonerror.InternalServerError(), err
 	}
 
+	_, domain, err := gomatrixserverlib.SplitID('@', userID)
+	if err != nil {
+		util.GetLogger(ctx).WithError(err).Error("gomatrixserverlib.SplitID failed")
+		return jsonerror.InternalServerError(), err
+	}
+
 	events, err := buildMembershipEvents(
 		ctx, res.RoomIDs, *profile, userID, cfg, evTime, rsAPI,
 	)
@@ -276,7 +298,7 @@ func updateProfile(
 		return jsonerror.InternalServerError(), e
 	}
 
-	if err := api.SendEvents(ctx, rsAPI, api.KindNew, events, cfg.Matrix.ServerName, cfg.Matrix.ServerName, nil, true); err != nil {
+	if err := api.SendEvents(ctx, rsAPI, api.KindNew, events, domain, domain, nil, true); err != nil {
 		util.GetLogger(ctx).WithError(err).Error("SendEvents failed")
 		return jsonerror.InternalServerError(), err
 	}
@@ -298,7 +320,7 @@ func getProfile(
 		return nil, err
 	}
 
-	if domain != cfg.Matrix.ServerName {
+	if !cfg.Matrix.IsLocalServerName(domain) {
 		profile, fedErr := federation.LookupProfile(ctx, domain, userID, "")
 		if fedErr != nil {
 			if x, ok := fedErr.(gomatrix.HTTPError); ok {
diff --git a/clientapi/routing/redaction.go b/clientapi/routing/redaction.go
index a0f3b115..778a02fd 100644
--- a/clientapi/routing/redaction.go
+++ b/clientapi/routing/redaction.go
@@ -131,7 +131,8 @@ func SendRedaction(
 			JSON: jsonerror.NotFound("Room does not exist"),
 		}
 	}
-	if err = roomserverAPI.SendEvents(context.Background(), rsAPI, roomserverAPI.KindNew, []*gomatrixserverlib.HeaderedEvent{e}, cfg.Matrix.ServerName, cfg.Matrix.ServerName, nil, false); err != nil {
+	domain := device.UserDomain()
+	if err = roomserverAPI.SendEvents(context.Background(), rsAPI, roomserverAPI.KindNew, []*gomatrixserverlib.HeaderedEvent{e}, domain, domain, nil, false); err != nil {
 		util.GetLogger(req.Context()).WithError(err).Errorf("failed to SendEvents")
 		return jsonerror.InternalServerError()
 	}
diff --git a/clientapi/routing/register.go b/clientapi/routing/register.go
index 0bda1e48..698d185b 100644
--- a/clientapi/routing/register.go
+++ b/clientapi/routing/register.go
@@ -412,7 +412,7 @@ func UserIDIsWithinApplicationServiceNamespace(
 		return false
 	}
 
-	if domain != cfg.Matrix.ServerName {
+	if !cfg.Matrix.IsLocalServerName(domain) {
 		return false
 	}
 
diff --git a/clientapi/routing/sendevent.go b/clientapi/routing/sendevent.go
index 114e9088..bb66cf6f 100644
--- a/clientapi/routing/sendevent.go
+++ b/clientapi/routing/sendevent.go
@@ -94,6 +94,7 @@ func SendEvent(
 	// create a mutex for the specific user in the specific room
 	// this avoids a situation where events that are received in quick succession are sent to the roomserver in a jumbled order
 	userID := device.UserID
+	domain := device.UserDomain()
 	mutex, _ := userRoomSendMutexes.LoadOrStore(roomID+userID, &sync.Mutex{})
 	mutex.(*sync.Mutex).Lock()
 	defer mutex.(*sync.Mutex).Unlock()
@@ -185,8 +186,8 @@ func SendEvent(
 		[]*gomatrixserverlib.HeaderedEvent{
 			e.Headered(verRes.RoomVersion),
 		},
-		cfg.Matrix.ServerName,
-		cfg.Matrix.ServerName,
+		domain,
+		domain,
 		txnAndSessionID,
 		false,
 	); err != nil {
diff --git a/clientapi/threepid/invites.go b/clientapi/threepid/invites.go
index 9670feca..99fb8171 100644
--- a/clientapi/threepid/invites.go
+++ b/clientapi/threepid/invites.go
@@ -215,7 +215,7 @@ func queryIDServerStoreInvite(
 	}
 
 	var profile *authtypes.Profile
-	if serverName == cfg.Matrix.ServerName {
+	if cfg.Matrix.IsLocalServerName(serverName) {
 		res := &userapi.QueryProfileResponse{}
 		err = userAPI.QueryProfile(ctx, &userapi.QueryProfileRequest{UserID: device.UserID}, res)
 		if err != nil {
diff --git a/clientapi/userutil/userutil.go b/clientapi/userutil/userutil.go
index 7e909ffa..9be1e9b3 100644
--- a/clientapi/userutil/userutil.go
+++ b/clientapi/userutil/userutil.go
@@ -17,6 +17,7 @@ import (
 	"fmt"
 	"strings"
 
+	"github.com/matrix-org/dendrite/setup/config"
 	"github.com/matrix-org/gomatrixserverlib"
 )
 
@@ -24,23 +25,23 @@ import (
 // usernameParam can either be a user ID or just the localpart/username.
 // If serverName is passed, it is verified against the domain obtained from usernameParam (if present)
 // Returns error in case of invalid usernameParam.
-func ParseUsernameParam(usernameParam string, expectedServerName *gomatrixserverlib.ServerName) (string, error) {
+func ParseUsernameParam(usernameParam string, cfg *config.Global) (string, gomatrixserverlib.ServerName, error) {
 	localpart := usernameParam
 
 	if strings.HasPrefix(usernameParam, "@") {
 		lp, domain, err := gomatrixserverlib.SplitID('@', usernameParam)
 
 		if err != nil {
-			return "", errors.New("invalid username")
+			return "", "", errors.New("invalid username")
 		}
 
-		if expectedServerName != nil && domain != *expectedServerName {
-			return "", errors.New("user ID does not belong to this server")
+		if !cfg.IsLocalServerName(domain) {
+			return "", "", errors.New("user ID does not belong to this server")
 		}
 
-		localpart = lp
+		return lp, domain, nil
 	}
-	return localpart, nil
+	return localpart, cfg.ServerName, nil
 }
 
 // MakeUserID generates user ID from localpart & server name
diff --git a/clientapi/userutil/userutil_test.go b/clientapi/userutil/userutil_test.go
index 2628642f..ccd6647b 100644
--- a/clientapi/userutil/userutil_test.go
+++ b/clientapi/userutil/userutil_test.go
@@ -15,6 +15,7 @@ package userutil
 import (
 	"testing"
 
+	"github.com/matrix-org/dendrite/setup/config"
 	"github.com/matrix-org/gomatrixserverlib"
 )
 
@@ -28,7 +29,11 @@ var (
 
 // TestGoodUserID checks that correct localpart is returned for a valid user ID.
 func TestGoodUserID(t *testing.T) {
-	lp, err := ParseUsernameParam(goodUserID, &serverName)
+	cfg := &config.Global{
+		ServerName: serverName,
+	}
+
+	lp, _, err := ParseUsernameParam(goodUserID, cfg)
 
 	if err != nil {
 		t.Error("User ID Parsing failed for ", goodUserID, " with error: ", err.Error())
@@ -41,7 +46,11 @@ func TestGoodUserID(t *testing.T) {
 
 // TestWithLocalpartOnly checks that localpart is returned when usernameParam contains only localpart.
 func TestWithLocalpartOnly(t *testing.T) {
-	lp, err := ParseUsernameParam(localpart, &serverName)
+	cfg := &config.Global{
+		ServerName: serverName,
+	}
+
+	lp, _, err := ParseUsernameParam(localpart, cfg)
 
 	if err != nil {
 		t.Error("User ID Parsing failed for ", localpart, " with error: ", err.Error())
@@ -54,7 +63,11 @@ func TestWithLocalpartOnly(t *testing.T) {
 
 // TestIncorrectDomain checks for error when there's server name mismatch.
 func TestIncorrectDomain(t *testing.T) {
-	_, err := ParseUsernameParam(goodUserID, &invalidServerName)
+	cfg := &config.Global{
+		ServerName: invalidServerName,
+	}
+
+	_, _, err := ParseUsernameParam(goodUserID, cfg)
 
 	if err == nil {
 		t.Error("Invalid Domain should return an error")
@@ -63,7 +76,11 @@ func TestIncorrectDomain(t *testing.T) {
 
 // TestBadUserID checks that ParseUsernameParam fails for invalid user ID
 func TestBadUserID(t *testing.T) {
-	_, err := ParseUsernameParam(badUserID, &serverName)
+	cfg := &config.Global{
+		ServerName: serverName,
+	}
+
+	_, _, err := ParseUsernameParam(badUserID, cfg)
 
 	if err == nil {
 		t.Error("Illegal User ID should return an error")
diff --git a/federationapi/federationapi.go b/federationapi/federationapi.go
index f6dace70..a58cba1b 100644
--- a/federationapi/federationapi.go
+++ b/federationapi/federationapi.go
@@ -69,7 +69,7 @@ func AddPublicRoutes(
 		TopicPresenceEvent:     cfg.Matrix.JetStream.Prefixed(jetstream.OutputPresenceEvent),
 		TopicDeviceListUpdate:  cfg.Matrix.JetStream.Prefixed(jetstream.InputDeviceListUpdate),
 		TopicSigningKeyUpdate:  cfg.Matrix.JetStream.Prefixed(jetstream.InputSigningKeyUpdate),
-		ServerName:             cfg.Matrix.ServerName,
+		Config:                 cfg,
 		UserAPI:                userAPI,
 	}
 
@@ -107,7 +107,7 @@ func NewInternalAPI(
 ) api.FederationInternalAPI {
 	cfg := &base.Cfg.FederationAPI
 
-	federationDB, err := storage.NewDatabase(base, &cfg.Database, base.Caches, base.Cfg.Global.ServerName)
+	federationDB, err := storage.NewDatabase(base, &cfg.Database, base.Caches, base.Cfg.Global.IsLocalServerName)
 	if err != nil {
 		logrus.WithError(err).Panic("failed to connect to federation sender db")
 	}
diff --git a/federationapi/federationapi_keys_test.go b/federationapi/federationapi_keys_test.go
index 85cc43aa..7ccc02f7 100644
--- a/federationapi/federationapi_keys_test.go
+++ b/federationapi/federationapi_keys_test.go
@@ -87,6 +87,7 @@ func TestMain(m *testing.M) {
 			cfg.Global.JetStream.StoragePath = config.Path(d)
 			cfg.Global.KeyID = serverKeyID
 			cfg.Global.KeyValidityPeriod = s.validity
+			cfg.FederationAPI.KeyPerspectives = nil
 			f, err := os.CreateTemp(d, "federation_keys_test*.db")
 			if err != nil {
 				return -1
@@ -207,7 +208,6 @@ func TestRenewalBehaviour(t *testing.T) {
 	// happy at this point that the key that we already have is from the past
 	// then repeating a key fetch should cause us to try and renew the key.
 	// If so, then the new key will end up in our cache.
-
 	serverC.renew()
 
 	res, err = serverA.api.FetchKeys(
diff --git a/federationapi/federationapi_test.go b/federationapi/federationapi_test.go
index e923143a..c37bc87c 100644
--- a/federationapi/federationapi_test.go
+++ b/federationapi/federationapi_test.go
@@ -164,6 +164,7 @@ func TestFederationAPIJoinThenKeyUpdate(t *testing.T) {
 func testFederationAPIJoinThenKeyUpdate(t *testing.T, dbType test.DBType) {
 	base, close := testrig.CreateBaseDendrite(t, dbType)
 	base.Cfg.FederationAPI.PreferDirectFetch = true
+	base.Cfg.FederationAPI.KeyPerspectives = nil
 	defer close()
 	jsctx, _ := base.NATS.Prepare(base.ProcessContext, &base.Cfg.Global.JetStream)
 	defer jetstream.DeleteAllStreams(jsctx, &base.Cfg.Global.JetStream)
diff --git a/federationapi/internal/keys.go b/federationapi/internal/keys.go
index 2b7a8219..258bd88b 100644
--- a/federationapi/internal/keys.go
+++ b/federationapi/internal/keys.go
@@ -99,7 +99,7 @@ func (s *FederationInternalAPI) handleLocalKeys(
 	results map[gomatrixserverlib.PublicKeyLookupRequest]gomatrixserverlib.PublicKeyLookupResult,
 ) {
 	for req := range requests {
-		if req.ServerName != s.cfg.Matrix.ServerName {
+		if !s.cfg.Matrix.IsLocalServerName(req.ServerName) {
 			continue
 		}
 		if req.KeyID == s.cfg.Matrix.KeyID {
diff --git a/federationapi/internal/perform.go b/federationapi/internal/perform.go
index 28ec48d7..1b61ec71 100644
--- a/federationapi/internal/perform.go
+++ b/federationapi/internal/perform.go
@@ -77,7 +77,7 @@ func (r *FederationInternalAPI) PerformJoin(
 	seenSet := make(map[gomatrixserverlib.ServerName]bool)
 	var uniqueList []gomatrixserverlib.ServerName
 	for _, srv := range request.ServerNames {
-		if seenSet[srv] || srv == r.cfg.Matrix.ServerName {
+		if seenSet[srv] || r.cfg.Matrix.IsLocalServerName(srv) {
 			continue
 		}
 		seenSet[srv] = true
diff --git a/federationapi/producers/syncapi.go b/federationapi/producers/syncapi.go
index 659ff1bc..7cce13a7 100644
--- a/federationapi/producers/syncapi.go
+++ b/federationapi/producers/syncapi.go
@@ -25,6 +25,7 @@ import (
 	"github.com/nats-io/nats.go"
 	log "github.com/sirupsen/logrus"
 
+	"github.com/matrix-org/dendrite/setup/config"
 	"github.com/matrix-org/dendrite/setup/jetstream"
 	"github.com/matrix-org/dendrite/syncapi/types"
 	userapi "github.com/matrix-org/dendrite/userapi/api"
@@ -39,7 +40,7 @@ type SyncAPIProducer struct {
 	TopicDeviceListUpdate  string
 	TopicSigningKeyUpdate  string
 	JetStream              nats.JetStreamContext
-	ServerName             gomatrixserverlib.ServerName
+	Config                 *config.FederationAPI
 	UserAPI                userapi.UserInternalAPI
 }
 
@@ -77,7 +78,7 @@ func (p *SyncAPIProducer) SendToDevice(
 	// device. If the event isn't targeted locally then we can't expand the
 	// wildcard as we don't know about the remote devices, so instead we leave it
 	// as-is, so that the federation sender can send it on with the wildcard intact.
-	if domain == p.ServerName && deviceID == "*" {
+	if p.Config.Matrix.IsLocalServerName(domain) && deviceID == "*" {
 		var res userapi.QueryDevicesResponse
 		err = p.UserAPI.QueryDevices(context.TODO(), &userapi.QueryDevicesRequest{
 			UserID: userID,
diff --git a/federationapi/queue/queue_test.go b/federationapi/queue/queue_test.go
index a1b28010..7ef4646f 100644
--- a/federationapi/queue/queue_test.go
+++ b/federationapi/queue/queue_test.go
@@ -47,7 +47,7 @@ func mustCreateFederationDatabase(t *testing.T, dbType test.DBType, realDatabase
 		connStr, dbClose := test.PrepareDBConnectionString(t, dbType)
 		db, err := storage.NewDatabase(b, &config.DatabaseOptions{
 			ConnectionString: config.DataSource(connStr),
-		}, b.Caches, b.Cfg.Global.ServerName)
+		}, b.Caches, b.Cfg.Global.IsLocalServerName)
 		if err != nil {
 			t.Fatalf("NewDatabase returned %s", err)
 		}
diff --git a/federationapi/routing/routing.go b/federationapi/routing/routing.go
index e25f9866..9f16e509 100644
--- a/federationapi/routing/routing.go
+++ b/federationapi/routing/routing.go
@@ -124,7 +124,7 @@ func Setup(
 
 	mu := internal.NewMutexByRoom()
 	v1fedmux.Handle("/send/{txnID}", MakeFedAPI(
-		"federation_send", cfg.Matrix.ServerName, keys, wakeup,
+		"federation_send", cfg.Matrix.ServerName, cfg.Matrix.IsLocalServerName, keys, wakeup,
 		func(httpReq *http.Request, request *gomatrixserverlib.FederationRequest, vars map[string]string) util.JSONResponse {
 			return Send(
 				httpReq, request, gomatrixserverlib.TransactionID(vars["txnID"]),
@@ -134,7 +134,7 @@ func Setup(
 	)).Methods(http.MethodPut, http.MethodOptions)
 
 	v1fedmux.Handle("/invite/{roomID}/{eventID}", MakeFedAPI(
-		"federation_invite", cfg.Matrix.ServerName, keys, wakeup,
+		"federation_invite", cfg.Matrix.ServerName, cfg.Matrix.IsLocalServerName, keys, wakeup,
 		func(httpReq *http.Request, request *gomatrixserverlib.FederationRequest, vars map[string]string) util.JSONResponse {
 			if roomserverAPI.IsServerBannedFromRoom(httpReq.Context(), rsAPI, vars["roomID"], request.Origin()) {
 				return util.JSONResponse{
@@ -150,7 +150,7 @@ func Setup(
 	)).Methods(http.MethodPut, http.MethodOptions)
 
 	v2fedmux.Handle("/invite/{roomID}/{eventID}", MakeFedAPI(
-		"federation_invite", cfg.Matrix.ServerName, keys, wakeup,
+		"federation_invite", cfg.Matrix.ServerName, cfg.Matrix.IsLocalServerName, keys, wakeup,
 		func(httpReq *http.Request, request *gomatrixserverlib.FederationRequest, vars map[string]string) util.JSONResponse {
 			if roomserverAPI.IsServerBannedFromRoom(httpReq.Context(), rsAPI, vars["roomID"], request.Origin()) {
 				return util.JSONResponse{
@@ -172,7 +172,7 @@ func Setup(
 	)).Methods(http.MethodPost, http.MethodOptions)
 
 	v1fedmux.Handle("/exchange_third_party_invite/{roomID}", MakeFedAPI(
-		"exchange_third_party_invite", cfg.Matrix.ServerName, keys, wakeup,
+		"exchange_third_party_invite", cfg.Matrix.ServerName, cfg.Matrix.IsLocalServerName, keys, wakeup,
 		func(httpReq *http.Request, request *gomatrixserverlib.FederationRequest, vars map[string]string) util.JSONResponse {
 			return ExchangeThirdPartyInvite(
 				httpReq, request, vars["roomID"], rsAPI, cfg, federation,
@@ -181,7 +181,7 @@ func Setup(
 	)).Methods(http.MethodPut, http.MethodOptions)
 
 	v1fedmux.Handle("/event/{eventID}", MakeFedAPI(
-		"federation_get_event", cfg.Matrix.ServerName, keys, wakeup,
+		"federation_get_event", cfg.Matrix.ServerName, cfg.Matrix.IsLocalServerName, keys, wakeup,
 		func(httpReq *http.Request, request *gomatrixserverlib.FederationRequest, vars map[string]string) util.JSONResponse {
 			return GetEvent(
 				httpReq.Context(), request, rsAPI, vars["eventID"], cfg.Matrix.ServerName,
@@ -190,7 +190,7 @@ func Setup(
 	)).Methods(http.MethodGet)
 
 	v1fedmux.Handle("/state/{roomID}", MakeFedAPI(
-		"federation_get_state", cfg.Matrix.ServerName, keys, wakeup,
+		"federation_get_state", cfg.Matrix.ServerName, cfg.Matrix.IsLocalServerName, keys, wakeup,
 		func(httpReq *http.Request, request *gomatrixserverlib.FederationRequest, vars map[string]string) util.JSONResponse {
 			if roomserverAPI.IsServerBannedFromRoom(httpReq.Context(), rsAPI, vars["roomID"], request.Origin()) {
 				return util.JSONResponse{
@@ -205,7 +205,7 @@ func Setup(
 	)).Methods(http.MethodGet)
 
 	v1fedmux.Handle("/state_ids/{roomID}", MakeFedAPI(
-		"federation_get_state_ids", cfg.Matrix.ServerName, keys, wakeup,
+		"federation_get_state_ids", cfg.Matrix.ServerName, cfg.Matrix.IsLocalServerName, keys, wakeup,
 		func(httpReq *http.Request, request *gomatrixserverlib.FederationRequest, vars map[string]string) util.JSONResponse {
 			if roomserverAPI.IsServerBannedFromRoom(httpReq.Context(), rsAPI, vars["roomID"], request.Origin()) {
 				return util.JSONResponse{
@@ -220,7 +220,7 @@ func Setup(
 	)).Methods(http.MethodGet)
 
 	v1fedmux.Handle("/event_auth/{roomID}/{eventID}", MakeFedAPI(
-		"federation_get_event_auth", cfg.Matrix.ServerName, keys, wakeup,
+		"federation_get_event_auth", cfg.Matrix.ServerName, cfg.Matrix.IsLocalServerName, keys, wakeup,
 		func(httpReq *http.Request, request *gomatrixserverlib.FederationRequest, vars map[string]string) util.JSONResponse {
 			if roomserverAPI.IsServerBannedFromRoom(httpReq.Context(), rsAPI, vars["roomID"], request.Origin()) {
 				return util.JSONResponse{
@@ -235,7 +235,7 @@ func Setup(
 	)).Methods(http.MethodGet)
 
 	v1fedmux.Handle("/query/directory", MakeFedAPI(
-		"federation_query_room_alias", cfg.Matrix.ServerName, keys, wakeup,
+		"federation_query_room_alias", cfg.Matrix.ServerName, cfg.Matrix.IsLocalServerName, keys, wakeup,
 		func(httpReq *http.Request, request *gomatrixserverlib.FederationRequest, vars map[string]string) util.JSONResponse {
 			return RoomAliasToID(
 				httpReq, federation, cfg, rsAPI, fsAPI,
@@ -244,7 +244,7 @@ func Setup(
 	)).Methods(http.MethodGet)
 
 	v1fedmux.Handle("/query/profile", MakeFedAPI(
-		"federation_query_profile", cfg.Matrix.ServerName, keys, wakeup,
+		"federation_query_profile", cfg.Matrix.ServerName, cfg.Matrix.IsLocalServerName, keys, wakeup,
 		func(httpReq *http.Request, request *gomatrixserverlib.FederationRequest, vars map[string]string) util.JSONResponse {
 			return GetProfile(
 				httpReq, userAPI, cfg,
@@ -253,7 +253,7 @@ func Setup(
 	)).Methods(http.MethodGet)
 
 	v1fedmux.Handle("/user/devices/{userID}", MakeFedAPI(
-		"federation_user_devices", cfg.Matrix.ServerName, keys, wakeup,
+		"federation_user_devices", cfg.Matrix.ServerName, cfg.Matrix.IsLocalServerName, keys, wakeup,
 		func(httpReq *http.Request, request *gomatrixserverlib.FederationRequest, vars map[string]string) util.JSONResponse {
 			return GetUserDevices(
 				httpReq, keyAPI, vars["userID"],
@@ -263,7 +263,7 @@ func Setup(
 
 	if mscCfg.Enabled("msc2444") {
 		v1fedmux.Handle("/peek/{roomID}/{peekID}", MakeFedAPI(
-			"federation_peek", cfg.Matrix.ServerName, keys, wakeup,
+			"federation_peek", cfg.Matrix.ServerName, cfg.Matrix.IsLocalServerName, keys, wakeup,
 			func(httpReq *http.Request, request *gomatrixserverlib.FederationRequest, vars map[string]string) util.JSONResponse {
 				if roomserverAPI.IsServerBannedFromRoom(httpReq.Context(), rsAPI, vars["roomID"], request.Origin()) {
 					return util.JSONResponse{
@@ -294,7 +294,7 @@ func Setup(
 	}
 
 	v1fedmux.Handle("/make_join/{roomID}/{userID}", MakeFedAPI(
-		"federation_make_join", cfg.Matrix.ServerName, keys, wakeup,
+		"federation_make_join", cfg.Matrix.ServerName, cfg.Matrix.IsLocalServerName, keys, wakeup,
 		func(httpReq *http.Request, request *gomatrixserverlib.FederationRequest, vars map[string]string) util.JSONResponse {
 			if roomserverAPI.IsServerBannedFromRoom(httpReq.Context(), rsAPI, vars["roomID"], request.Origin()) {
 				return util.JSONResponse{
@@ -325,7 +325,7 @@ func Setup(
 	)).Methods(http.MethodGet)
 
 	v1fedmux.Handle("/send_join/{roomID}/{eventID}", MakeFedAPI(
-		"federation_send_join", cfg.Matrix.ServerName, keys, wakeup,
+		"federation_send_join", cfg.Matrix.ServerName, cfg.Matrix.IsLocalServerName, keys, wakeup,
 		func(httpReq *http.Request, request *gomatrixserverlib.FederationRequest, vars map[string]string) util.JSONResponse {
 			if roomserverAPI.IsServerBannedFromRoom(httpReq.Context(), rsAPI, vars["roomID"], request.Origin()) {
 				return util.JSONResponse{
@@ -357,7 +357,7 @@ func Setup(
 	)).Methods(http.MethodPut)
 
 	v2fedmux.Handle("/send_join/{roomID}/{eventID}", MakeFedAPI(
-		"federation_send_join", cfg.Matrix.ServerName, keys, wakeup,
+		"federation_send_join", cfg.Matrix.ServerName, cfg.Matrix.IsLocalServerName, keys, wakeup,
 		func(httpReq *http.Request, request *gomatrixserverlib.FederationRequest, vars map[string]string) util.JSONResponse {
 			if roomserverAPI.IsServerBannedFromRoom(httpReq.Context(), rsAPI, vars["roomID"], request.Origin()) {
 				return util.JSONResponse{
@@ -374,7 +374,7 @@ func Setup(
 	)).Methods(http.MethodPut)
 
 	v1fedmux.Handle("/make_leave/{roomID}/{eventID}", MakeFedAPI(
-		"federation_make_leave", cfg.Matrix.ServerName, keys, wakeup,
+		"federation_make_leave", cfg.Matrix.ServerName, cfg.Matrix.IsLocalServerName, keys, wakeup,
 		func(httpReq *http.Request, request *gomatrixserverlib.FederationRequest, vars map[string]string) util.JSONResponse {
 			if roomserverAPI.IsServerBannedFromRoom(httpReq.Context(), rsAPI, vars["roomID"], request.Origin()) {
 				return util.JSONResponse{
@@ -391,7 +391,7 @@ func Setup(
 	)).Methods(http.MethodGet)
 
 	v1fedmux.Handle("/send_leave/{roomID}/{eventID}", MakeFedAPI(
-		"federation_send_leave", cfg.Matrix.ServerName, keys, wakeup,
+		"federation_send_leave", cfg.Matrix.ServerName, cfg.Matrix.IsLocalServerName, keys, wakeup,
 		func(httpReq *http.Request, request *gomatrixserverlib.FederationRequest, vars map[string]string) util.JSONResponse {
 			if roomserverAPI.IsServerBannedFromRoom(httpReq.Context(), rsAPI, vars["roomID"], request.Origin()) {
 				return util.JSONResponse{
@@ -423,7 +423,7 @@ func Setup(
 	)).Methods(http.MethodPut)
 
 	v2fedmux.Handle("/send_leave/{roomID}/{eventID}", MakeFedAPI(
-		"federation_send_leave", cfg.Matrix.ServerName, keys, wakeup,
+		"federation_send_leave", cfg.Matrix.ServerName, cfg.Matrix.IsLocalServerName, keys, wakeup,
 		func(httpReq *http.Request, request *gomatrixserverlib.FederationRequest, vars map[string]string) util.JSONResponse {
 			if roomserverAPI.IsServerBannedFromRoom(httpReq.Context(), rsAPI, vars["roomID"], request.Origin()) {
 				return util.JSONResponse{
@@ -447,7 +447,7 @@ func Setup(
 	)).Methods(http.MethodGet)
 
 	v1fedmux.Handle("/get_missing_events/{roomID}", MakeFedAPI(
-		"federation_get_missing_events", cfg.Matrix.ServerName, keys, wakeup,
+		"federation_get_missing_events", cfg.Matrix.ServerName, cfg.Matrix.IsLocalServerName, keys, wakeup,
 		func(httpReq *http.Request, request *gomatrixserverlib.FederationRequest, vars map[string]string) util.JSONResponse {
 			if roomserverAPI.IsServerBannedFromRoom(httpReq.Context(), rsAPI, vars["roomID"], request.Origin()) {
 				return util.JSONResponse{
@@ -460,7 +460,7 @@ func Setup(
 	)).Methods(http.MethodPost)
 
 	v1fedmux.Handle("/backfill/{roomID}", MakeFedAPI(
-		"federation_backfill", cfg.Matrix.ServerName, keys, wakeup,
+		"federation_backfill", cfg.Matrix.ServerName, cfg.Matrix.IsLocalServerName, keys, wakeup,
 		func(httpReq *http.Request, request *gomatrixserverlib.FederationRequest, vars map[string]string) util.JSONResponse {
 			if roomserverAPI.IsServerBannedFromRoom(httpReq.Context(), rsAPI, vars["roomID"], request.Origin()) {
 				return util.JSONResponse{
@@ -479,14 +479,14 @@ func Setup(
 	).Methods(http.MethodGet, http.MethodPost)
 
 	v1fedmux.Handle("/user/keys/claim", MakeFedAPI(
-		"federation_keys_claim", cfg.Matrix.ServerName, keys, wakeup,
+		"federation_keys_claim", cfg.Matrix.ServerName, cfg.Matrix.IsLocalServerName, keys, wakeup,
 		func(httpReq *http.Request, request *gomatrixserverlib.FederationRequest, vars map[string]string) util.JSONResponse {
 			return ClaimOneTimeKeys(httpReq, request, keyAPI, cfg.Matrix.ServerName)
 		},
 	)).Methods(http.MethodPost)
 
 	v1fedmux.Handle("/user/keys/query", MakeFedAPI(
-		"federation_keys_query", cfg.Matrix.ServerName, keys, wakeup,
+		"federation_keys_query", cfg.Matrix.ServerName, cfg.Matrix.IsLocalServerName, keys, wakeup,
 		func(httpReq *http.Request, request *gomatrixserverlib.FederationRequest, vars map[string]string) util.JSONResponse {
 			return QueryDeviceKeys(httpReq, request, keyAPI, cfg.Matrix.ServerName)
 		},
@@ -525,15 +525,15 @@ func ErrorIfLocalServerNotInRoom(
 
 // MakeFedAPI makes an http.Handler that checks matrix federation authentication.
 func MakeFedAPI(
-	metricsName string,
-	serverName gomatrixserverlib.ServerName,
+	metricsName string, serverName gomatrixserverlib.ServerName,
+	isLocalServerName func(gomatrixserverlib.ServerName) bool,
 	keyRing gomatrixserverlib.JSONVerifier,
 	wakeup *FederationWakeups,
 	f func(*http.Request, *gomatrixserverlib.FederationRequest, map[string]string) util.JSONResponse,
 ) http.Handler {
 	h := func(req *http.Request) util.JSONResponse {
 		fedReq, errResp := gomatrixserverlib.VerifyHTTPRequest(
-			req, time.Now(), serverName, keyRing,
+			req, time.Now(), serverName, isLocalServerName, keyRing,
 		)
 		if fedReq == nil {
 			return errResp
diff --git a/federationapi/storage/postgres/storage.go b/federationapi/storage/postgres/storage.go
index 6e208d09..a33fa4a4 100644
--- a/federationapi/storage/postgres/storage.go
+++ b/federationapi/storage/postgres/storage.go
@@ -36,7 +36,7 @@ type Database struct {
 }
 
 // NewDatabase opens a new database
-func NewDatabase(base *base.BaseDendrite, dbProperties *config.DatabaseOptions, cache caching.FederationCache, serverName gomatrixserverlib.ServerName) (*Database, error) {
+func NewDatabase(base *base.BaseDendrite, dbProperties *config.DatabaseOptions, cache caching.FederationCache, isLocalServerName func(gomatrixserverlib.ServerName) bool) (*Database, error) {
 	var d Database
 	var err error
 	if d.db, d.writer, err = base.DatabaseConnection(dbProperties, sqlutil.NewDummyWriter()); err != nil {
@@ -96,7 +96,7 @@ func NewDatabase(base *base.BaseDendrite, dbProperties *config.DatabaseOptions,
 	}
 	d.Database = shared.Database{
 		DB:                       d.db,
-		ServerName:               serverName,
+		IsLocalServerName:        isLocalServerName,
 		Cache:                    cache,
 		Writer:                   d.writer,
 		FederationJoinedHosts:    joinedHosts,
diff --git a/federationapi/storage/shared/storage.go b/federationapi/storage/shared/storage.go
index 6afb313a..4fabff7d 100644
--- a/federationapi/storage/shared/storage.go
+++ b/federationapi/storage/shared/storage.go
@@ -29,7 +29,7 @@ import (
 
 type Database struct {
 	DB                       *sql.DB
-	ServerName               gomatrixserverlib.ServerName
+	IsLocalServerName        func(gomatrixserverlib.ServerName) bool
 	Cache                    caching.FederationCache
 	Writer                   sqlutil.Writer
 	FederationQueuePDUs      tables.FederationQueuePDUs
@@ -124,7 +124,7 @@ func (d *Database) GetJoinedHostsForRooms(ctx context.Context, roomIDs []string,
 	}
 	if excludeSelf {
 		for i, server := range servers {
-			if server == d.ServerName {
+			if d.IsLocalServerName(server) {
 				servers = append(servers[:i], servers[i+1:]...)
 			}
 		}
diff --git a/federationapi/storage/sqlite3/storage.go b/federationapi/storage/sqlite3/storage.go
index c89cb6be..e86ac817 100644
--- a/federationapi/storage/sqlite3/storage.go
+++ b/federationapi/storage/sqlite3/storage.go
@@ -35,7 +35,7 @@ type Database struct {
 }
 
 // NewDatabase opens a new database
-func NewDatabase(base *base.BaseDendrite, dbProperties *config.DatabaseOptions, cache caching.FederationCache, serverName gomatrixserverlib.ServerName) (*Database, error) {
+func NewDatabase(base *base.BaseDendrite, dbProperties *config.DatabaseOptions, cache caching.FederationCache, isLocalServerName func(gomatrixserverlib.ServerName) bool) (*Database, error) {
 	var d Database
 	var err error
 	if d.db, d.writer, err = base.DatabaseConnection(dbProperties, sqlutil.NewExclusiveWriter()); err != nil {
@@ -95,7 +95,7 @@ func NewDatabase(base *base.BaseDendrite, dbProperties *config.DatabaseOptions,
 	}
 	d.Database = shared.Database{
 		DB:                       d.db,
-		ServerName:               serverName,
+		IsLocalServerName:        isLocalServerName,
 		Cache:                    cache,
 		Writer:                   d.writer,
 		FederationJoinedHosts:    joinedHosts,
diff --git a/federationapi/storage/storage.go b/federationapi/storage/storage.go
index f246b9bc..142e281e 100644
--- a/federationapi/storage/storage.go
+++ b/federationapi/storage/storage.go
@@ -29,12 +29,12 @@ import (
 )
 
 // NewDatabase opens a new database
-func NewDatabase(base *base.BaseDendrite, dbProperties *config.DatabaseOptions, cache caching.FederationCache, serverName gomatrixserverlib.ServerName) (Database, error) {
+func NewDatabase(base *base.BaseDendrite, dbProperties *config.DatabaseOptions, cache caching.FederationCache, isLocalServerName func(gomatrixserverlib.ServerName) bool) (Database, error) {
 	switch {
 	case dbProperties.ConnectionString.IsSQLite():
-		return sqlite3.NewDatabase(base, dbProperties, cache, serverName)
+		return sqlite3.NewDatabase(base, dbProperties, cache, isLocalServerName)
 	case dbProperties.ConnectionString.IsPostgres():
-		return postgres.NewDatabase(base, dbProperties, cache, serverName)
+		return postgres.NewDatabase(base, dbProperties, cache, isLocalServerName)
 	default:
 		return nil, fmt.Errorf("unexpected database type")
 	}
diff --git a/federationapi/storage/storage_test.go b/federationapi/storage/storage_test.go
index 6272fd2b..f7408fa9 100644
--- a/federationapi/storage/storage_test.go
+++ b/federationapi/storage/storage_test.go
@@ -19,7 +19,7 @@ func mustCreateFederationDatabase(t *testing.T, dbType test.DBType) (storage.Dat
 	connStr, dbClose := test.PrepareDBConnectionString(t, dbType)
 	db, err := storage.NewDatabase(b, &config.DatabaseOptions{
 		ConnectionString: config.DataSource(connStr),
-	}, b.Caches, b.Cfg.Global.ServerName)
+	}, b.Caches, func(server gomatrixserverlib.ServerName) bool { return server == "localhost" })
 	if err != nil {
 		t.Fatalf("NewDatabase returned %s", err)
 	}
diff --git a/go.mod b/go.mod
index 7f9bb389..39dfb0fe 100644
--- a/go.mod
+++ b/go.mod
@@ -22,7 +22,7 @@ require (
 	github.com/matrix-org/dugong v0.0.0-20210921133753-66e6b1c67e2e
 	github.com/matrix-org/go-sqlite3-js v0.0.0-20220419092513-28aa791a1c91
 	github.com/matrix-org/gomatrix v0.0.0-20220926102614-ceba4d9f7530
-	github.com/matrix-org/gomatrixserverlib v0.0.0-20221021091412-7c772f1b388a
+	github.com/matrix-org/gomatrixserverlib v0.0.0-20221025142407-17b0be811afa
 	github.com/matrix-org/pinecone v0.0.0-20221007145426-3adc85477dd3
 	github.com/matrix-org/util v0.0.0-20200807132607-55161520e1d4
 	github.com/mattn/go-sqlite3 v1.14.15
diff --git a/go.sum b/go.sum
index 5cce7e0d..5e625386 100644
--- a/go.sum
+++ b/go.sum
@@ -387,8 +387,8 @@ github.com/matrix-org/go-sqlite3-js v0.0.0-20220419092513-28aa791a1c91 h1:s7fexw
 github.com/matrix-org/go-sqlite3-js v0.0.0-20220419092513-28aa791a1c91/go.mod h1:e+cg2q7C7yE5QnAXgzo512tgFh1RbQLC0+jozuegKgo=
 github.com/matrix-org/gomatrix v0.0.0-20220926102614-ceba4d9f7530 h1:kHKxCOLcHH8r4Fzarl4+Y3K5hjothkVW5z7T1dUM11U=
 github.com/matrix-org/gomatrix v0.0.0-20220926102614-ceba4d9f7530/go.mod h1:/gBX06Kw0exX1HrwmoBibFA98yBk/jxKpGVeyQbff+s=
-github.com/matrix-org/gomatrixserverlib v0.0.0-20221021091412-7c772f1b388a h1:6rJFN5NBuzZ7h5meYkLtXKa6VFZfDc8oVXHd4SDXr5o=
-github.com/matrix-org/gomatrixserverlib v0.0.0-20221021091412-7c772f1b388a/go.mod h1:Mtifyr8q8htcBeugvlDnkBcNUy5LO8OzUoplAf1+mb4=
+github.com/matrix-org/gomatrixserverlib v0.0.0-20221025142407-17b0be811afa h1:S98DShDv3sn7O4n4HjtJOejypseYVpv1R/XPg+cDnfI=
+github.com/matrix-org/gomatrixserverlib v0.0.0-20221025142407-17b0be811afa/go.mod h1:Mtifyr8q8htcBeugvlDnkBcNUy5LO8OzUoplAf1+mb4=
 github.com/matrix-org/pinecone v0.0.0-20221007145426-3adc85477dd3 h1:lzkSQvBv8TuqKJCPoVwOVvEnARTlua5rrNy/Qw2Vxeo=
 github.com/matrix-org/pinecone v0.0.0-20221007145426-3adc85477dd3/go.mod h1:K0N1ixHQxXoCyqolDqVxPM3ArrDtcMs8yegOx2Lfv9k=
 github.com/matrix-org/util v0.0.0-20200807132607-55161520e1d4 h1:eCEHXWDv9Rm335MSuB49mFUK44bwZPFSDde3ORE3syk=
diff --git a/roomserver/internal/perform/perform_admin.go b/roomserver/internal/perform/perform_admin.go
index cb6b22d3..6a6d51b0 100644
--- a/roomserver/internal/perform/perform_admin.go
+++ b/roomserver/internal/perform/perform_admin.go
@@ -117,6 +117,11 @@ func (r *Admin) PerformAdminEvacuateRoom(
 			PrevEvents: prevEvents,
 		}
 
+		_, senderDomain, err := gomatrixserverlib.SplitID('@', fledglingEvent.Sender)
+		if err != nil {
+			continue
+		}
+
 		if fledglingEvent.Content, err = json.Marshal(memberContent); err != nil {
 			res.Error = &api.PerformError{
 				Code: api.PerformErrorBadRequest,
@@ -146,8 +151,8 @@ func (r *Admin) PerformAdminEvacuateRoom(
 		inputEvents = append(inputEvents, api.InputRoomEvent{
 			Kind:         api.KindNew,
 			Event:        event,
-			Origin:       r.Cfg.Matrix.ServerName,
-			SendAsServer: string(r.Cfg.Matrix.ServerName),
+			Origin:       senderDomain,
+			SendAsServer: string(senderDomain),
 		})
 		res.Affected = append(res.Affected, stateKey)
 		prevEvents = []gomatrixserverlib.EventReference{
@@ -176,7 +181,7 @@ func (r *Admin) PerformAdminEvacuateUser(
 		}
 		return nil
 	}
-	if domain != r.Cfg.Matrix.ServerName {
+	if !r.Cfg.Matrix.IsLocalServerName(domain) {
 		res.Error = &api.PerformError{
 			Code: api.PerformErrorBadRequest,
 			Msg:  "Can only evacuate local users using this endpoint",
diff --git a/roomserver/internal/perform/perform_invite.go b/roomserver/internal/perform/perform_invite.go
index 3fbdf332..f60247cd 100644
--- a/roomserver/internal/perform/perform_invite.go
+++ b/roomserver/internal/perform/perform_invite.go
@@ -70,8 +70,8 @@ func (r *Inviter) PerformInvite(
 		}
 		return nil, nil
 	}
-	isTargetLocal := domain == r.Cfg.Matrix.ServerName
-	isOriginLocal := senderDomain == r.Cfg.Matrix.ServerName
+	isTargetLocal := r.Cfg.Matrix.IsLocalServerName(domain)
+	isOriginLocal := r.Cfg.Matrix.IsLocalServerName(senderDomain)
 	if !isOriginLocal && !isTargetLocal {
 		res.Error = &api.PerformError{
 			Code: api.PerformErrorBadRequest,
diff --git a/roomserver/internal/perform/perform_join.go b/roomserver/internal/perform/perform_join.go
index 262273ff..9d596ab3 100644
--- a/roomserver/internal/perform/perform_join.go
+++ b/roomserver/internal/perform/perform_join.go
@@ -92,7 +92,7 @@ func (r *Joiner) performJoin(
 			Msg:  fmt.Sprintf("Supplied user ID %q in incorrect format", req.UserID),
 		}
 	}
-	if domain != r.Cfg.Matrix.ServerName {
+	if !r.Cfg.Matrix.IsLocalServerName(domain) {
 		return "", "", &rsAPI.PerformError{
 			Code: rsAPI.PerformErrorBadRequest,
 			Msg:  fmt.Sprintf("User %q does not belong to this homeserver", req.UserID),
@@ -124,7 +124,7 @@ func (r *Joiner) performJoinRoomByAlias(
 	// Check if this alias matches our own server configuration. If it
 	// doesn't then we'll need to try a federated join.
 	var roomID string
-	if domain != r.Cfg.Matrix.ServerName {
+	if !r.Cfg.Matrix.IsLocalServerName(domain) {
 		// The alias isn't owned by us, so we will need to try joining using
 		// a remote server.
 		dirReq := fsAPI.PerformDirectoryLookupRequest{
@@ -172,7 +172,7 @@ func (r *Joiner) performJoinRoomByID(
 	// The original client request ?server_name=... may include this HS so filter that out so we
 	// don't attempt to make_join with ourselves
 	for i := 0; i < len(req.ServerNames); i++ {
-		if req.ServerNames[i] == r.Cfg.Matrix.ServerName {
+		if r.Cfg.Matrix.IsLocalServerName(req.ServerNames[i]) {
 			// delete this entry
 			req.ServerNames = append(req.ServerNames[:i], req.ServerNames[i+1:]...)
 			i--
@@ -191,12 +191,19 @@ func (r *Joiner) performJoinRoomByID(
 	// If the server name in the room ID isn't ours then it's a
 	// possible candidate for finding the room via federation. Add
 	// it to the list of servers to try.
-	if domain != r.Cfg.Matrix.ServerName {
+	if !r.Cfg.Matrix.IsLocalServerName(domain) {
 		req.ServerNames = append(req.ServerNames, domain)
 	}
 
 	// Prepare the template for the join event.
 	userID := req.UserID
+	_, userDomain, err := gomatrixserverlib.SplitID('@', userID)
+	if err != nil {
+		return "", "", &rsAPI.PerformError{
+			Code: rsAPI.PerformErrorBadRequest,
+			Msg:  fmt.Sprintf("User ID %q is invalid: %s", userID, err),
+		}
+	}
 	eb := gomatrixserverlib.EventBuilder{
 		Type:     gomatrixserverlib.MRoomMember,
 		Sender:   userID,
@@ -247,7 +254,7 @@ func (r *Joiner) performJoinRoomByID(
 
 		// If we were invited by someone from another server then we can
 		// assume they are in the room so we can join via them.
-		if inviterDomain != r.Cfg.Matrix.ServerName {
+		if !r.Cfg.Matrix.IsLocalServerName(inviterDomain) {
 			req.ServerNames = append(req.ServerNames, inviterDomain)
 			forceFederatedJoin = true
 			memberEvent := gjson.Parse(string(inviteEvent.JSON()))
@@ -300,7 +307,7 @@ func (r *Joiner) performJoinRoomByID(
 					{
 						Kind:         rsAPI.KindNew,
 						Event:        event.Headered(buildRes.RoomVersion),
-						SendAsServer: string(r.Cfg.Matrix.ServerName),
+						SendAsServer: string(userDomain),
 					},
 				},
 			}
@@ -323,7 +330,7 @@ func (r *Joiner) performJoinRoomByID(
 		// The room doesn't exist locally. If the room ID looks like it should
 		// be ours then this probably means that we've nuked our database at
 		// some point.
-		if domain == r.Cfg.Matrix.ServerName {
+		if r.Cfg.Matrix.IsLocalServerName(domain) {
 			// If there are no more server names to try then give up here.
 			// Otherwise we'll try a federated join as normal, since it's quite
 			// possible that the room still exists on other servers.
@@ -348,7 +355,7 @@ func (r *Joiner) performJoinRoomByID(
 	// it will have been overwritten with a room ID by performJoinRoomByAlias.
 	// We should now include this in the response so that the CS API can
 	// return the right room ID.
-	return req.RoomIDOrAlias, r.Cfg.Matrix.ServerName, nil
+	return req.RoomIDOrAlias, userDomain, nil
 }
 
 func (r *Joiner) performFederatedJoinRoomByID(
diff --git a/roomserver/internal/perform/perform_leave.go b/roomserver/internal/perform/perform_leave.go
index 85b65981..49e4b479 100644
--- a/roomserver/internal/perform/perform_leave.go
+++ b/roomserver/internal/perform/perform_leave.go
@@ -52,7 +52,7 @@ func (r *Leaver) PerformLeave(
 	if err != nil {
 		return nil, fmt.Errorf("supplied user ID %q in incorrect format", req.UserID)
 	}
-	if domain != r.Cfg.Matrix.ServerName {
+	if !r.Cfg.Matrix.IsLocalServerName(domain) {
 		return nil, fmt.Errorf("user %q does not belong to this homeserver", req.UserID)
 	}
 	logger := logrus.WithContext(ctx).WithFields(logrus.Fields{
@@ -85,7 +85,7 @@ func (r *Leaver) performLeaveRoomByID(
 		if serr != nil {
 			return nil, fmt.Errorf("sender %q is invalid", senderUser)
 		}
-		if senderDomain != r.Cfg.Matrix.ServerName {
+		if !r.Cfg.Matrix.IsLocalServerName(senderDomain) {
 			return r.performFederatedRejectInvite(ctx, req, res, senderUser, eventID)
 		}
 		// check that this is not a "server notice room"
@@ -186,7 +186,7 @@ func (r *Leaver) performLeaveRoomByID(
 				Kind:         api.KindNew,
 				Event:        event.Headered(buildRes.RoomVersion),
 				Origin:       senderDomain,
-				SendAsServer: string(r.Cfg.Matrix.ServerName),
+				SendAsServer: string(senderDomain),
 			},
 		},
 	}
diff --git a/roomserver/internal/perform/perform_peek.go b/roomserver/internal/perform/perform_peek.go
index 74d87a5b..436d137f 100644
--- a/roomserver/internal/perform/perform_peek.go
+++ b/roomserver/internal/perform/perform_peek.go
@@ -72,7 +72,7 @@ func (r *Peeker) performPeek(
 			Msg:  fmt.Sprintf("Supplied user ID %q in incorrect format", req.UserID),
 		}
 	}
-	if domain != r.Cfg.Matrix.ServerName {
+	if !r.Cfg.Matrix.IsLocalServerName(domain) {
 		return "", &api.PerformError{
 			Code: api.PerformErrorBadRequest,
 			Msg:  fmt.Sprintf("User %q does not belong to this homeserver", req.UserID),
@@ -104,7 +104,7 @@ func (r *Peeker) performPeekRoomByAlias(
 	// Check if this alias matches our own server configuration. If it
 	// doesn't then we'll need to try a federated peek.
 	var roomID string
-	if domain != r.Cfg.Matrix.ServerName {
+	if !r.Cfg.Matrix.IsLocalServerName(domain) {
 		// The alias isn't owned by us, so we will need to try peeking using
 		// a remote server.
 		dirReq := fsAPI.PerformDirectoryLookupRequest{
@@ -154,7 +154,7 @@ func (r *Peeker) performPeekRoomByID(
 
 	// handle federated peeks
 	// FIXME: don't create an outbound peek if we already have one going.
-	if domain != r.Cfg.Matrix.ServerName {
+	if !r.Cfg.Matrix.IsLocalServerName(domain) {
 		// If the server name in the room ID isn't ours then it's a
 		// possible candidate for finding the room via federation. Add
 		// it to the list of servers to try.
diff --git a/roomserver/internal/perform/perform_unpeek.go b/roomserver/internal/perform/perform_unpeek.go
index 49e9067c..0d97da4d 100644
--- a/roomserver/internal/perform/perform_unpeek.go
+++ b/roomserver/internal/perform/perform_unpeek.go
@@ -67,7 +67,7 @@ func (r *Unpeeker) performUnpeek(
 			Msg:  fmt.Sprintf("Supplied user ID %q in incorrect format", req.UserID),
 		}
 	}
-	if domain != r.Cfg.Matrix.ServerName {
+	if !r.Cfg.Matrix.IsLocalServerName(domain) {
 		return &api.PerformError{
 			Code: api.PerformErrorBadRequest,
 			Msg:  fmt.Sprintf("User %q does not belong to this homeserver", req.UserID),
diff --git a/roomserver/internal/perform/perform_upgrade.go b/roomserver/internal/perform/perform_upgrade.go
index d6dc9708..38abe323 100644
--- a/roomserver/internal/perform/perform_upgrade.go
+++ b/roomserver/internal/perform/perform_upgrade.go
@@ -60,6 +60,13 @@ func (r *Upgrader) performRoomUpgrade(
 ) (string, *api.PerformError) {
 	roomID := req.RoomID
 	userID := req.UserID
+	_, userDomain, err := gomatrixserverlib.SplitID('@', userID)
+	if err != nil {
+		return "", &api.PerformError{
+			Code: api.PerformErrorNotAllowed,
+			Msg:  "Error validating the user ID",
+		}
+	}
 	evTime := time.Now()
 
 	// Return an immediate error if the room does not exist
@@ -80,7 +87,7 @@ func (r *Upgrader) performRoomUpgrade(
 
 	// TODO (#267): Check room ID doesn't clash with an existing one, and we
 	//              probably shouldn't be using pseudo-random strings, maybe GUIDs?
-	newRoomID := fmt.Sprintf("!%s:%s", util.RandomString(16), r.Cfg.Matrix.ServerName)
+	newRoomID := fmt.Sprintf("!%s:%s", util.RandomString(16), userDomain)
 
 	// Get the existing room state for the old room.
 	oldRoomReq := &api.QueryLatestEventsAndStateRequest{
@@ -107,12 +114,12 @@ func (r *Upgrader) performRoomUpgrade(
 	}
 
 	// Send the setup events to the new room
-	if pErr = r.sendInitialEvents(ctx, evTime, userID, newRoomID, string(req.RoomVersion), eventsToMake); pErr != nil {
+	if pErr = r.sendInitialEvents(ctx, evTime, userID, userDomain, newRoomID, string(req.RoomVersion), eventsToMake); pErr != nil {
 		return "", pErr
 	}
 
 	// 5. Send the tombstone event to the old room
-	if pErr = r.sendHeaderedEvent(ctx, tombstoneEvent, string(r.Cfg.Matrix.ServerName)); pErr != nil {
+	if pErr = r.sendHeaderedEvent(ctx, userDomain, tombstoneEvent, string(userDomain)); pErr != nil {
 		return "", pErr
 	}
 
@@ -122,7 +129,7 @@ func (r *Upgrader) performRoomUpgrade(
 	}
 
 	// If the old room had a canonical alias event, it should be deleted in the old room
-	if pErr = r.clearOldCanonicalAliasEvent(ctx, oldRoomRes, evTime, userID, roomID); pErr != nil {
+	if pErr = r.clearOldCanonicalAliasEvent(ctx, oldRoomRes, evTime, userID, userDomain, roomID); pErr != nil {
 		return "", pErr
 	}
 
@@ -132,7 +139,7 @@ func (r *Upgrader) performRoomUpgrade(
 	}
 
 	// 6. Restrict power levels in the old room
-	if pErr = r.restrictOldRoomPowerLevels(ctx, evTime, userID, roomID); pErr != nil {
+	if pErr = r.restrictOldRoomPowerLevels(ctx, evTime, userID, userDomain, roomID); pErr != nil {
 		return "", pErr
 	}
 
@@ -154,7 +161,7 @@ func (r *Upgrader) getRoomPowerLevels(ctx context.Context, roomID string) (*goma
 	return powerLevelContent, nil
 }
 
-func (r *Upgrader) restrictOldRoomPowerLevels(ctx context.Context, evTime time.Time, userID, roomID string) *api.PerformError {
+func (r *Upgrader) restrictOldRoomPowerLevels(ctx context.Context, evTime time.Time, userID string, userDomain gomatrixserverlib.ServerName, roomID string) *api.PerformError {
 	restrictedPowerLevelContent, pErr := r.getRoomPowerLevels(ctx, roomID)
 	if pErr != nil {
 		return pErr
@@ -183,7 +190,7 @@ func (r *Upgrader) restrictOldRoomPowerLevels(ctx context.Context, evTime time.T
 			return resErr
 		}
 	} else {
-		if resErr = r.sendHeaderedEvent(ctx, restrictedPowerLevelsHeadered, api.DoNotSendToOtherServers); resErr != nil {
+		if resErr = r.sendHeaderedEvent(ctx, userDomain, restrictedPowerLevelsHeadered, api.DoNotSendToOtherServers); resErr != nil {
 			return resErr
 		}
 	}
@@ -223,7 +230,7 @@ func moveLocalAliases(ctx context.Context,
 	return nil
 }
 
-func (r *Upgrader) clearOldCanonicalAliasEvent(ctx context.Context, oldRoom *api.QueryLatestEventsAndStateResponse, evTime time.Time, userID, roomID string) *api.PerformError {
+func (r *Upgrader) clearOldCanonicalAliasEvent(ctx context.Context, oldRoom *api.QueryLatestEventsAndStateResponse, evTime time.Time, userID string, userDomain gomatrixserverlib.ServerName, roomID string) *api.PerformError {
 	for _, event := range oldRoom.StateEvents {
 		if event.Type() != gomatrixserverlib.MRoomCanonicalAlias || !event.StateKeyEquals("") {
 			continue
@@ -254,7 +261,7 @@ func (r *Upgrader) clearOldCanonicalAliasEvent(ctx context.Context, oldRoom *api
 			return resErr
 		}
 	} else {
-		if resErr = r.sendHeaderedEvent(ctx, emptyCanonicalAliasEvent, api.DoNotSendToOtherServers); resErr != nil {
+		if resErr = r.sendHeaderedEvent(ctx, userDomain, emptyCanonicalAliasEvent, api.DoNotSendToOtherServers); resErr != nil {
 			return resErr
 		}
 	}
@@ -495,7 +502,7 @@ func (r *Upgrader) generateInitialEvents(ctx context.Context, oldRoom *api.Query
 	return eventsToMake, nil
 }
 
-func (r *Upgrader) sendInitialEvents(ctx context.Context, evTime time.Time, userID, newRoomID, newVersion string, eventsToMake []fledglingEvent) *api.PerformError {
+func (r *Upgrader) sendInitialEvents(ctx context.Context, evTime time.Time, userID string, userDomain gomatrixserverlib.ServerName, newRoomID, newVersion string, eventsToMake []fledglingEvent) *api.PerformError {
 	var err error
 	var builtEvents []*gomatrixserverlib.HeaderedEvent
 	authEvents := gomatrixserverlib.NewAuthEvents(nil)
@@ -519,7 +526,7 @@ func (r *Upgrader) sendInitialEvents(ctx context.Context, evTime time.Time, user
 			builder.PrevEvents = []gomatrixserverlib.EventReference{builtEvents[i-1].EventReference()}
 		}
 		var event *gomatrixserverlib.Event
-		event, err = r.buildEvent(&builder, &authEvents, evTime, gomatrixserverlib.RoomVersion(newVersion))
+		event, err = r.buildEvent(&builder, userDomain, &authEvents, evTime, gomatrixserverlib.RoomVersion(newVersion))
 		if err != nil {
 			return &api.PerformError{
 				Msg: fmt.Sprintf("Failed to build new %q event: %s", builder.Type, err),
@@ -547,7 +554,7 @@ func (r *Upgrader) sendInitialEvents(ctx context.Context, evTime time.Time, user
 		inputs = append(inputs, api.InputRoomEvent{
 			Kind:         api.KindNew,
 			Event:        event,
-			Origin:       r.Cfg.Matrix.ServerName,
+			Origin:       userDomain,
 			SendAsServer: api.DoNotSendToOtherServers,
 		})
 	}
@@ -668,6 +675,7 @@ func createTemporaryPowerLevels(powerLevelContent *gomatrixserverlib.PowerLevelC
 
 func (r *Upgrader) sendHeaderedEvent(
 	ctx context.Context,
+	serverName gomatrixserverlib.ServerName,
 	headeredEvent *gomatrixserverlib.HeaderedEvent,
 	sendAsServer string,
 ) *api.PerformError {
@@ -675,7 +683,7 @@ func (r *Upgrader) sendHeaderedEvent(
 	inputs = append(inputs, api.InputRoomEvent{
 		Kind:         api.KindNew,
 		Event:        headeredEvent,
-		Origin:       r.Cfg.Matrix.ServerName,
+		Origin:       serverName,
 		SendAsServer: sendAsServer,
 	})
 	if err := api.SendInputRoomEvents(ctx, r.URSAPI, inputs, false); err != nil {
@@ -689,6 +697,7 @@ func (r *Upgrader) sendHeaderedEvent(
 
 func (r *Upgrader) buildEvent(
 	builder *gomatrixserverlib.EventBuilder,
+	serverName gomatrixserverlib.ServerName,
 	provider gomatrixserverlib.AuthEventProvider,
 	evTime time.Time,
 	roomVersion gomatrixserverlib.RoomVersion,
@@ -703,7 +712,7 @@ func (r *Upgrader) buildEvent(
 	}
 	builder.AuthEvents = refs
 	event, err := builder.Build(
-		evTime, r.Cfg.Matrix.ServerName, r.Cfg.Matrix.KeyID,
+		evTime, serverName, r.Cfg.Matrix.KeyID,
 		r.Cfg.Matrix.PrivateKey, roomVersion,
 	)
 	if err != nil {
diff --git a/setup/config/config_global.go b/setup/config/config_global.go
index 784893d2..82577282 100644
--- a/setup/config/config_global.go
+++ b/setup/config/config_global.go
@@ -14,6 +14,9 @@ type Global struct {
 	// The name of the server. This is usually the domain name, e.g 'matrix.org', 'localhost'.
 	ServerName gomatrixserverlib.ServerName `yaml:"server_name"`
 
+	// The secondary server names, used for virtual hosting.
+	SecondaryServerNames []gomatrixserverlib.ServerName `yaml:"-"`
+
 	// Path to the private key which will be used to sign requests and events.
 	PrivateKeyPath Path `yaml:"private_key"`
 
@@ -120,6 +123,18 @@ func (c *Global) Verify(configErrs *ConfigErrors, isMonolith bool) {
 	c.Cache.Verify(configErrs, isMonolith)
 }
 
+func (c *Global) IsLocalServerName(serverName gomatrixserverlib.ServerName) bool {
+	if c.ServerName == serverName {
+		return true
+	}
+	for _, secondaryName := range c.SecondaryServerNames {
+		if secondaryName == serverName {
+			return true
+		}
+	}
+	return false
+}
+
 type OldVerifyKeys struct {
 	// Path to the private key.
 	PrivateKeyPath Path `yaml:"private_key"`
diff --git a/setup/mscs/msc2836/msc2836.go b/setup/mscs/msc2836/msc2836.go
index 452b1458..98502f5c 100644
--- a/setup/mscs/msc2836/msc2836.go
+++ b/setup/mscs/msc2836/msc2836.go
@@ -132,7 +132,7 @@ func Enable(
 	base.PublicFederationAPIMux.Handle("/unstable/event_relationships", httputil.MakeExternalAPI(
 		"msc2836_event_relationships", func(req *http.Request) util.JSONResponse {
 			fedReq, errResp := gomatrixserverlib.VerifyHTTPRequest(
-				req, time.Now(), base.Cfg.Global.ServerName, keyRing,
+				req, time.Now(), base.Cfg.Global.ServerName, base.Cfg.Global.IsLocalServerName, keyRing,
 			)
 			if fedReq == nil {
 				return errResp
diff --git a/setup/mscs/msc2946/msc2946.go b/setup/mscs/msc2946/msc2946.go
index a92a16a2..bc9df0f9 100644
--- a/setup/mscs/msc2946/msc2946.go
+++ b/setup/mscs/msc2946/msc2946.go
@@ -64,7 +64,7 @@ func Enable(
 	fedAPI := httputil.MakeExternalAPI(
 		"msc2946_fed_spaces", func(req *http.Request) util.JSONResponse {
 			fedReq, errResp := gomatrixserverlib.VerifyHTTPRequest(
-				req, time.Now(), base.Cfg.Global.ServerName, keyRing,
+				req, time.Now(), base.Cfg.Global.ServerName, base.Cfg.Global.IsLocalServerName, keyRing,
 			)
 			if fedReq == nil {
 				return errResp
diff --git a/test/testrig/base.go b/test/testrig/base.go
index 10cc2407..15fb5c37 100644
--- a/test/testrig/base.go
+++ b/test/testrig/base.go
@@ -36,6 +36,7 @@ func CreateBaseDendrite(t *testing.T, dbType test.DBType) (*base.BaseDendrite, f
 		Monolithic: true,
 	})
 	cfg.Global.JetStream.InMemory = true
+	cfg.FederationAPI.KeyPerspectives = nil
 	switch dbType {
 	case test.DBTypePostgres:
 		cfg.Global.Defaults(config.DefaultOpts{ // autogen a signing key
@@ -106,6 +107,7 @@ func Base(cfg *config.Dendrite) (*base.BaseDendrite, nats.JetStreamContext, *nat
 	}
 	cfg.Global.JetStream.InMemory = true
 	cfg.SyncAPI.Fulltext.InMemory = true
+	cfg.FederationAPI.KeyPerspectives = nil
 	base := base.NewBaseDendrite(cfg, "Tests")
 	js, jc := base.NATS.Prepare(base.ProcessContext, &cfg.Global.JetStream)
 	return base, js, jc
diff --git a/userapi/api/api.go b/userapi/api/api.go
index eef29144..8d7f783d 100644
--- a/userapi/api/api.go
+++ b/userapi/api/api.go
@@ -318,8 +318,9 @@ type QuerySearchProfilesResponse struct {
 
 // PerformAccountCreationRequest is the request for PerformAccountCreation
 type PerformAccountCreationRequest struct {
-	AccountType AccountType // Required: whether this is a guest or user account
-	Localpart   string      // Required: The localpart for this account. Ignored if account type is guest.
+	AccountType AccountType                  // Required: whether this is a guest or user account
+	Localpart   string                       // Required: The localpart for this account. Ignored if account type is guest.
+	ServerName  gomatrixserverlib.ServerName // optional: if not specified, default server name used instead
 
 	AppServiceID string // optional: the application service ID (not user ID) creating this account, if any.
 	Password     string // optional: if missing then this account will be a passwordless account
@@ -360,7 +361,8 @@ type PerformLastSeenUpdateResponse struct {
 // PerformDeviceCreationRequest is the request for PerformDeviceCreation
 type PerformDeviceCreationRequest struct {
 	Localpart   string
-	AccessToken string // optional: if blank one will be made on your behalf
+	ServerName  gomatrixserverlib.ServerName // optional: if blank, default server name used
+	AccessToken string                       // optional: if blank one will be made on your behalf
 	// optional: if nil an ID is generated for you. If set, replaces any existing device session,
 	// which will generate a new access token and invalidate the old one.
 	DeviceID *string
@@ -384,7 +386,8 @@ type PerformDeviceCreationResponse struct {
 
 // PerformAccountDeactivationRequest is the request for PerformAccountDeactivation
 type PerformAccountDeactivationRequest struct {
-	Localpart string
+	Localpart  string
+	ServerName gomatrixserverlib.ServerName // optional: if blank, default server name used
 }
 
 // PerformAccountDeactivationResponse is the response for PerformAccountDeactivation
@@ -434,6 +437,18 @@ type Device struct {
 	AccountType  AccountType
 }
 
+func (d *Device) UserDomain() gomatrixserverlib.ServerName {
+	_, domain, err := gomatrixserverlib.SplitID('@', d.UserID)
+	if err != nil {
+		// This really is catastrophic because it means that someone
+		// managed to forge a malformed user ID for a device during
+		// login.
+		// TODO: Is there a better way to deal with this than panic?
+		panic(err)
+	}
+	return domain
+}
+
 // Account represents a Matrix account on this home server.
 type Account struct {
 	UserID       string
@@ -577,7 +592,9 @@ type Notification struct {
 }
 
 type PerformSetAvatarURLRequest struct {
-	Localpart, AvatarURL string
+	Localpart  string
+	ServerName gomatrixserverlib.ServerName
+	AvatarURL  string
 }
 type PerformSetAvatarURLResponse struct {
 	Profile *authtypes.Profile `json:"profile"`
@@ -606,7 +623,9 @@ type QueryAccountByPasswordResponse struct {
 }
 
 type PerformUpdateDisplayNameRequest struct {
-	Localpart, DisplayName string
+	Localpart   string
+	ServerName  gomatrixserverlib.ServerName
+	DisplayName string
 }
 
 type PerformUpdateDisplayNameResponse struct {
diff --git a/userapi/internal/api.go b/userapi/internal/api.go
index 7b94b3da..9ca76965 100644
--- a/userapi/internal/api.go
+++ b/userapi/internal/api.go
@@ -46,9 +46,9 @@ import (
 type UserInternalAPI struct {
 	DB           storage.Database
 	SyncProducer *producers.SyncAPI
+	Config       *config.UserAPI
 
 	DisableTLSValidation bool
-	ServerName           gomatrixserverlib.ServerName
 	// AppServices is the list of all registered AS
 	AppServices []config.ApplicationService
 	KeyAPI      keyapi.UserKeyAPI
@@ -62,8 +62,8 @@ func (a *UserInternalAPI) InputAccountData(ctx context.Context, req *api.InputAc
 	if err != nil {
 		return err
 	}
-	if domain != a.ServerName {
-		return fmt.Errorf("cannot query profile of remote users: got %s want %s", domain, a.ServerName)
+	if !a.Config.Matrix.IsLocalServerName(domain) {
+		return fmt.Errorf("cannot update account data of remote users (server name %s)", domain)
 	}
 	if req.DataType == "" {
 		return fmt.Errorf("data type must not be empty")
@@ -104,7 +104,7 @@ func (a *UserInternalAPI) setFullyRead(ctx context.Context, req *api.InputAccoun
 		logrus.WithError(err).Error("UserInternalAPI.setFullyRead: SplitID failure")
 		return nil
 	}
-	if domain != a.ServerName {
+	if !a.Config.Matrix.IsLocalServerName(domain) {
 		return nil
 	}
 
@@ -171,6 +171,11 @@ func addUserToRoom(
 }
 
 func (a *UserInternalAPI) PerformAccountCreation(ctx context.Context, req *api.PerformAccountCreationRequest, res *api.PerformAccountCreationResponse) error {
+	serverName := req.ServerName
+	if serverName == "" {
+		serverName = a.Config.Matrix.ServerName
+	}
+	// XXXX: Use the server name here
 	acc, err := a.DB.CreateAccount(ctx, req.Localpart, req.Password, req.AppServiceID, req.AccountType)
 	if err != nil {
 		if errors.Is(err, sqlutil.ErrUserExists) { // This account already exists
@@ -188,8 +193,8 @@ func (a *UserInternalAPI) PerformAccountCreation(ctx context.Context, req *api.P
 		res.Account = &api.Account{
 			AppServiceID: req.AppServiceID,
 			Localpart:    req.Localpart,
-			ServerName:   a.ServerName,
-			UserID:       fmt.Sprintf("@%s:%s", req.Localpart, a.ServerName),
+			ServerName:   serverName,
+			UserID:       fmt.Sprintf("@%s:%s", req.Localpart, serverName),
 			AccountType:  req.AccountType,
 		}
 		return nil
@@ -235,6 +240,12 @@ func (a *UserInternalAPI) PerformPasswordUpdate(ctx context.Context, req *api.Pe
 }
 
 func (a *UserInternalAPI) PerformDeviceCreation(ctx context.Context, req *api.PerformDeviceCreationRequest, res *api.PerformDeviceCreationResponse) error {
+	serverName := req.ServerName
+	if serverName == "" {
+		serverName = a.Config.Matrix.ServerName
+	}
+	_ = serverName
+	// XXXX: Use the server name here
 	util.GetLogger(ctx).WithFields(logrus.Fields{
 		"localpart":    req.Localpart,
 		"device_id":    req.DeviceID,
@@ -259,8 +270,8 @@ func (a *UserInternalAPI) PerformDeviceDeletion(ctx context.Context, req *api.Pe
 	if err != nil {
 		return err
 	}
-	if domain != a.ServerName {
-		return fmt.Errorf("cannot PerformDeviceDeletion of remote users: got %s want %s", domain, a.ServerName)
+	if !a.Config.Matrix.IsLocalServerName(domain) {
+		return fmt.Errorf("cannot PerformDeviceDeletion of remote users (server name %s)", domain)
 	}
 	deletedDeviceIDs := req.DeviceIDs
 	if len(req.DeviceIDs) == 0 {
@@ -392,8 +403,8 @@ func (a *UserInternalAPI) QueryProfile(ctx context.Context, req *api.QueryProfil
 	if err != nil {
 		return err
 	}
-	if domain != a.ServerName {
-		return fmt.Errorf("cannot query profile of remote users: got %s want %s", domain, a.ServerName)
+	if !a.Config.Matrix.IsLocalServerName(domain) {
+		return fmt.Errorf("cannot query profile of remote users (server name %s)", domain)
 	}
 	prof, err := a.DB.GetProfileByLocalpart(ctx, local)
 	if err != nil {
@@ -443,8 +454,8 @@ func (a *UserInternalAPI) QueryDevices(ctx context.Context, req *api.QueryDevice
 	if err != nil {
 		return err
 	}
-	if domain != a.ServerName {
-		return fmt.Errorf("cannot query devices of remote users: got %s want %s", domain, a.ServerName)
+	if !a.Config.Matrix.IsLocalServerName(domain) {
+		return fmt.Errorf("cannot query devices of remote users (server name %s)", domain)
 	}
 	devs, err := a.DB.GetDevicesByLocalpart(ctx, local)
 	if err != nil {
@@ -460,8 +471,8 @@ func (a *UserInternalAPI) QueryAccountData(ctx context.Context, req *api.QueryAc
 	if err != nil {
 		return err
 	}
-	if domain != a.ServerName {
-		return fmt.Errorf("cannot query account data of remote users: got %s want %s", domain, a.ServerName)
+	if !a.Config.Matrix.IsLocalServerName(domain) {
+		return fmt.Errorf("cannot query account data of remote users (server name %s)", domain)
 	}
 	if req.DataType != "" {
 		var data json.RawMessage
@@ -509,10 +520,13 @@ func (a *UserInternalAPI) QueryAccessToken(ctx context.Context, req *api.QueryAc
 		}
 		return err
 	}
-	localPart, _, err := gomatrixserverlib.SplitID('@', device.UserID)
+	localPart, domain, err := gomatrixserverlib.SplitID('@', device.UserID)
 	if err != nil {
 		return err
 	}
+	if !a.Config.Matrix.IsLocalServerName(domain) {
+		return nil
+	}
 	acc, err := a.DB.GetAccountByLocalpart(ctx, localPart)
 	if err != nil {
 		return err
@@ -547,7 +561,7 @@ func (a *UserInternalAPI) queryAppServiceToken(ctx context.Context, token, appSe
 		AccountType:  api.AccountTypeAppService,
 	}
 
-	localpart, err := userutil.ParseUsernameParam(appServiceUserID, &a.ServerName)
+	localpart, _, err := userutil.ParseUsernameParam(appServiceUserID, a.Config.Matrix)
 	if err != nil {
 		return nil, err
 	}
@@ -572,8 +586,16 @@ func (a *UserInternalAPI) queryAppServiceToken(ctx context.Context, token, appSe
 
 // PerformAccountDeactivation deactivates the user's account, removing all ability for the user to login again.
 func (a *UserInternalAPI) PerformAccountDeactivation(ctx context.Context, req *api.PerformAccountDeactivationRequest, res *api.PerformAccountDeactivationResponse) error {
+	serverName := req.ServerName
+	if serverName == "" {
+		serverName = a.Config.Matrix.ServerName
+	}
+	if !a.Config.Matrix.IsLocalServerName(serverName) {
+		return fmt.Errorf("server name %q not locally configured", serverName)
+	}
+
 	evacuateReq := &rsapi.PerformAdminEvacuateUserRequest{
-		UserID: fmt.Sprintf("@%s:%s", req.Localpart, a.ServerName),
+		UserID: fmt.Sprintf("@%s:%s", req.Localpart, serverName),
 	}
 	evacuateRes := &rsapi.PerformAdminEvacuateUserResponse{}
 	if err := a.RSAPI.PerformAdminEvacuateUser(ctx, evacuateReq, evacuateRes); err != nil {
@@ -584,7 +606,7 @@ func (a *UserInternalAPI) PerformAccountDeactivation(ctx context.Context, req *a
 	}
 
 	deviceReq := &api.PerformDeviceDeletionRequest{
-		UserID: fmt.Sprintf("@%s:%s", req.Localpart, a.ServerName),
+		UserID: fmt.Sprintf("@%s:%s", req.Localpart, serverName),
 	}
 	deviceRes := &api.PerformDeviceDeletionResponse{}
 	if err := a.PerformDeviceDeletion(ctx, deviceReq, deviceRes); err != nil {
diff --git a/userapi/internal/api_logintoken.go b/userapi/internal/api_logintoken.go
index f1bf391e..87f25e5e 100644
--- a/userapi/internal/api_logintoken.go
+++ b/userapi/internal/api_logintoken.go
@@ -31,8 +31,8 @@ func (a *UserInternalAPI) PerformLoginTokenCreation(ctx context.Context, req *ap
 	if err != nil {
 		return err
 	}
-	if domain != a.ServerName {
-		return fmt.Errorf("cannot create a login token for a remote user: got %s want %s", domain, a.ServerName)
+	if !a.Config.Matrix.IsLocalServerName(domain) {
+		return fmt.Errorf("cannot create a login token for a remote user (server name %s)", domain)
 	}
 	tokenMeta, err := a.DB.CreateLoginToken(ctx, &req.Data)
 	if err != nil {
@@ -63,8 +63,8 @@ func (a *UserInternalAPI) QueryLoginToken(ctx context.Context, req *api.QueryLog
 	if err != nil {
 		return err
 	}
-	if domain != a.ServerName {
-		return fmt.Errorf("cannot return a login token for a remote user: got %s want %s", domain, a.ServerName)
+	if !a.Config.Matrix.IsLocalServerName(domain) {
+		return fmt.Errorf("cannot return a login token for a remote user (server name %s)", domain)
 	}
 	if _, err := a.DB.GetAccountByLocalpart(ctx, localpart); err != nil {
 		res.Data = nil
diff --git a/userapi/userapi.go b/userapi/userapi.go
index c077248e..e46a8e76 100644
--- a/userapi/userapi.go
+++ b/userapi/userapi.go
@@ -76,7 +76,7 @@ func NewInternalAPI(
 	userAPI := &internal.UserInternalAPI{
 		DB:                   db,
 		SyncProducer:         syncProducer,
-		ServerName:           cfg.Matrix.ServerName,
+		Config:               cfg,
 		AppServices:          appServices,
 		KeyAPI:               keyAPI,
 		RSAPI:                rsAPI,
diff --git a/userapi/userapi_test.go b/userapi/userapi_test.go
index aaa93f45..2a43c0bd 100644
--- a/userapi/userapi_test.go
+++ b/userapi/userapi_test.go
@@ -66,8 +66,8 @@ func MustMakeInternalAPI(t *testing.T, opts apiTestOpts, dbType test.DBType) (ap
 	}
 
 	return &internal.UserInternalAPI{
-			DB:         accountDB,
-			ServerName: cfg.Matrix.ServerName,
+			DB:     accountDB,
+			Config: cfg,
 		}, accountDB, func() {
 			close()
 			baseclose()