Move Invite logic to GMSL (#3086)

This is both the federation receiving & sending side logic (which were
previously entangeld in a single function)

15 files changed, 342 insertions, 425 deletions

diff --git a/clientapi/routing/createroom.go b/clientapi/routing/createroom.go
index aaa305f0..799fc797 100644
--- a/clientapi/routing/createroom.go
+++ b/clientapi/routing/createroom.go
@@ -135,7 +135,6 @@ func CreateRoom(
 // createRoom implements /createRoom
 func createRoom(
 	ctx context.Context,
-	// TODO: remove dependency on createRoomRequest
 	createRequest createRoomRequest, device *api.Device,
 	cfg *config.ClientAPI,
 	profileAPI api.ClientUserAPI, rsAPI roomserverAPI.ClientRoomserverAPI,
diff --git a/federationapi/api/api.go b/federationapi/api/api.go
index b53ec3dd..5b49e509 100644
--- a/federationapi/api/api.go
+++ b/federationapi/api/api.go
@@ -62,7 +62,7 @@ type RoomserverFederationAPI interface {
 	// Handle an instruction to make_leave & send_leave with a remote server.
 	PerformLeave(ctx context.Context, request *PerformLeaveRequest, response *PerformLeaveResponse) error
 	// Handle sending an invite to a remote server.
-	PerformInvite(ctx context.Context, request *PerformInviteRequest, response *PerformInviteResponse) error
+	SendInvite(ctx context.Context, event gomatrixserverlib.PDU, strippedState []gomatrixserverlib.InviteStrippedState) (gomatrixserverlib.PDU, error)
 	// Handle an instruction to peek a room on a remote server.
 	PerformOutboundPeek(ctx context.Context, request *PerformOutboundPeekRequest, response *PerformOutboundPeekResponse) error
 	// Query the server names of the joined hosts in a room.
@@ -190,9 +190,9 @@ type PerformLeaveResponse struct {
 }
 
 type PerformInviteRequest struct {
-	RoomVersion     gomatrixserverlib.RoomVersion   `json:"room_version"`
-	Event           *rstypes.HeaderedEvent          `json:"event"`
-	InviteRoomState []fclient.InviteV2StrippedState `json:"invite_room_state"`
+	RoomVersion     gomatrixserverlib.RoomVersion           `json:"room_version"`
+	Event           *rstypes.HeaderedEvent                  `json:"event"`
+	InviteRoomState []gomatrixserverlib.InviteStrippedState `json:"invite_room_state"`
 }
 
 type PerformInviteResponse struct {
diff --git a/federationapi/internal/perform.go b/federationapi/internal/perform.go
index 99943d86..ed800d03 100644
--- a/federationapi/internal/perform.go
+++ b/federationapi/internal/perform.go
@@ -503,60 +503,59 @@ func (r *FederationInternalAPI) PerformLeave(
 	)
 }
 
-// PerformLeaveRequest implements api.FederationInternalAPI
-func (r *FederationInternalAPI) PerformInvite(
+// SendInvite implements api.FederationInternalAPI
+func (r *FederationInternalAPI) SendInvite(
 	ctx context.Context,
-	request *api.PerformInviteRequest,
-	response *api.PerformInviteResponse,
-) (err error) {
-	_, origin, err := r.cfg.Matrix.SplitLocalID('@', request.Event.Sender())
+	event gomatrixserverlib.PDU,
+	strippedState []gomatrixserverlib.InviteStrippedState,
+) (gomatrixserverlib.PDU, error) {
+	_, origin, err := r.cfg.Matrix.SplitLocalID('@', event.Sender())
 	if err != nil {
-		return err
+		return nil, err
 	}
 
-	if request.Event.StateKey() == nil {
-		return errors.New("invite must be a state event")
+	if event.StateKey() == nil {
+		return nil, errors.New("invite must be a state event")
 	}
 
-	_, destination, err := gomatrixserverlib.SplitID('@', *request.Event.StateKey())
+	_, destination, err := gomatrixserverlib.SplitID('@', *event.StateKey())
 	if err != nil {
-		return fmt.Errorf("gomatrixserverlib.SplitID: %w", err)
+		return nil, fmt.Errorf("gomatrixserverlib.SplitID: %w", err)
 	}
 
 	// TODO (devon): This should be allowed via a relay. Currently only transactions
 	// can be sent to relays. Would need to extend relays to handle invites.
 	if !r.shouldAttemptDirectFederation(destination) {
-		return fmt.Errorf("relay servers have no meaningful response for invite.")
+		return nil, fmt.Errorf("relay servers have no meaningful response for invite.")
 	}
 
 	logrus.WithFields(logrus.Fields{
-		"event_id":     request.Event.EventID(),
-		"user_id":      *request.Event.StateKey(),
-		"room_id":      request.Event.RoomID(),
-		"room_version": request.RoomVersion,
+		"event_id":     event.EventID(),
+		"user_id":      *event.StateKey(),
+		"room_id":      event.RoomID(),
+		"room_version": event.Version(),
 		"destination":  destination,
 	}).Info("Sending invite")
 
-	inviteReq, err := fclient.NewInviteV2Request(request.Event.PDU, request.InviteRoomState)
+	inviteReq, err := fclient.NewInviteV2Request(event, strippedState)
 	if err != nil {
-		return fmt.Errorf("gomatrixserverlib.NewInviteV2Request: %w", err)
+		return nil, fmt.Errorf("gomatrixserverlib.NewInviteV2Request: %w", err)
 	}
 
 	inviteRes, err := r.federation.SendInviteV2(ctx, origin, destination, inviteReq)
 	if err != nil {
-		return fmt.Errorf("r.federation.SendInviteV2: failed to send invite: %w", err)
+		return nil, fmt.Errorf("r.federation.SendInviteV2: failed to send invite: %w", err)
 	}
-	verImpl, err := gomatrixserverlib.GetRoomVersion(request.RoomVersion)
+	verImpl, err := gomatrixserverlib.GetRoomVersion(event.Version())
 	if err != nil {
-		return err
+		return nil, err
 	}
 
 	inviteEvent, err := verImpl.NewEventFromUntrustedJSON(inviteRes.Event)
 	if err != nil {
-		return fmt.Errorf("r.federation.SendInviteV2 failed to decode event response: %w", err)
+		return nil, fmt.Errorf("r.federation.SendInviteV2 failed to decode event response: %w", err)
 	}
-	response.Event = &types.HeaderedEvent{PDU: inviteEvent}
-	return nil
+	return inviteEvent, nil
 }
 
 // PerformServersAlive implements api.FederationInternalAPI
diff --git a/federationapi/routing/invite.go b/federationapi/routing/invite.go
index 993d4046..78a09d94 100644
--- a/federationapi/routing/invite.go
+++ b/federationapi/routing/invite.go
@@ -20,7 +20,6 @@ import (
 	"fmt"
 	"net/http"
 
-	"github.com/getsentry/sentry-go"
 	"github.com/matrix-org/dendrite/roomserver/api"
 	"github.com/matrix-org/dendrite/roomserver/types"
 	"github.com/matrix-org/dendrite/setup/config"
@@ -34,7 +33,7 @@ import (
 func InviteV2(
 	httpReq *http.Request,
 	request *fclient.FederationRequest,
-	roomID string,
+	roomID spec.RoomID,
 	eventID string,
 	cfg *config.FederationAPI,
 	rsAPI api.FederationRoomserverAPI,
@@ -56,9 +55,55 @@ func InviteV2(
 			JSON: spec.BadJSON(err.Error()),
 		}
 	case nil:
-		return processInvite(
-			httpReq.Context(), true, inviteReq.Event(), inviteReq.RoomVersion(), inviteReq.InviteRoomState(), roomID, eventID, cfg, rsAPI, keys,
-		)
+		if inviteReq.Event().StateKey() == nil {
+			return util.JSONResponse{
+				Code: http.StatusBadRequest,
+				JSON: spec.BadJSON("The invite event has no state key"),
+			}
+		}
+
+		invitedUser, userErr := spec.NewUserID(*inviteReq.Event().StateKey(), true)
+		if userErr != nil {
+			return util.JSONResponse{
+				Code: http.StatusBadRequest,
+				JSON: spec.InvalidParam("The user ID is invalid"),
+			}
+		}
+		if !cfg.Matrix.IsLocalServerName(invitedUser.Domain()) {
+			return util.JSONResponse{
+				Code: http.StatusBadRequest,
+				JSON: spec.InvalidParam("The invited user domain does not belong to this server"),
+			}
+		}
+
+		if inviteReq.Event().EventID() != eventID {
+			return util.JSONResponse{
+				Code: http.StatusBadRequest,
+				JSON: spec.BadJSON("The event ID in the request path must match the event ID in the invite event JSON"),
+			}
+		}
+
+		input := gomatrixserverlib.HandleInviteInput{
+			RoomVersion:       inviteReq.RoomVersion(),
+			RoomID:            roomID,
+			InvitedUser:       *invitedUser,
+			KeyID:             cfg.Matrix.KeyID,
+			PrivateKey:        cfg.Matrix.PrivateKey,
+			Verifier:          keys,
+			RoomQuerier:       rsAPI,
+			MembershipQuerier: &api.MembershipQuerier{Roomserver: rsAPI},
+			StateQuerier:      rsAPI.StateQuerier(),
+			InviteEvent:       inviteReq.Event(),
+			StrippedState:     inviteReq.InviteRoomState(),
+		}
+		event, jsonErr := handleInvite(httpReq.Context(), input, rsAPI)
+		if jsonErr != nil {
+			return *jsonErr
+		}
+		return util.JSONResponse{
+			Code: http.StatusOK,
+			JSON: fclient.RespInviteV2{Event: event.JSON()},
+		}
 	default:
 		return util.JSONResponse{
 			Code: http.StatusBadRequest,
@@ -71,7 +116,7 @@ func InviteV2(
 func InviteV1(
 	httpReq *http.Request,
 	request *fclient.FederationRequest,
-	roomID string,
+	roomID spec.RoomID,
 	eventID string,
 	cfg *config.FederationAPI,
 	rsAPI api.FederationRoomserverAPI,
@@ -94,55 +139,11 @@ func InviteV1(
 			JSON: spec.NotJSON("The request body could not be decoded into an invite v1 request. " + err.Error()),
 		}
 	}
-	var strippedState []fclient.InviteV2StrippedState
-	if err := json.Unmarshal(event.Unsigned(), &strippedState); err != nil {
+	var strippedState []gomatrixserverlib.InviteStrippedState
+	if jsonErr := json.Unmarshal(event.Unsigned(), &strippedState); jsonErr != nil {
 		// just warn, they may not have added any.
 		util.GetLogger(httpReq.Context()).Warnf("failed to extract stripped state from invite event")
 	}
-	return processInvite(
-		httpReq.Context(), false, event, roomVer, strippedState, roomID, eventID, cfg, rsAPI, keys,
-	)
-}
-
-func processInvite(
-	ctx context.Context,
-	isInviteV2 bool,
-	event gomatrixserverlib.PDU,
-	roomVer gomatrixserverlib.RoomVersion,
-	strippedState []fclient.InviteV2StrippedState,
-	roomID string,
-	eventID string,
-	cfg *config.FederationAPI,
-	rsAPI api.FederationRoomserverAPI,
-	keys gomatrixserverlib.JSONVerifier,
-) util.JSONResponse {
-
-	// Check that we can accept invites for this room version.
-	verImpl, err := gomatrixserverlib.GetRoomVersion(roomVer)
-	if err != nil {
-		return util.JSONResponse{
-			Code: http.StatusBadRequest,
-			JSON: spec.UnsupportedRoomVersion(
-				fmt.Sprintf("Room version %q is not supported by this server.", roomVer),
-			),
-		}
-	}
-
-	// Check that the room ID is correct.
-	if event.RoomID() != roomID {
-		return util.JSONResponse{
-			Code: http.StatusBadRequest,
-			JSON: spec.BadJSON("The room ID in the request path must match the room ID in the invite event JSON"),
-		}
-	}
-
-	// Check that the event ID is correct.
-	if event.EventID() != eventID {
-		return util.JSONResponse{
-			Code: http.StatusBadRequest,
-			JSON: spec.BadJSON("The event ID in the request path must match the event ID in the invite event JSON"),
-		}
-	}
 
 	if event.StateKey() == nil {
 		return util.JSONResponse{
@@ -151,105 +152,91 @@ func processInvite(
 		}
 	}
 
-	_, domain, err := cfg.Matrix.SplitLocalID('@', *event.StateKey())
+	invitedUser, err := spec.NewUserID(*event.StateKey(), true)
 	if err != nil {
 		return util.JSONResponse{
 			Code: http.StatusBadRequest,
-			JSON: spec.InvalidParam(fmt.Sprintf("The user ID is invalid or domain %q does not belong to this server", domain)),
+			JSON: spec.InvalidParam("The user ID is invalid"),
 		}
 	}
-
-	// Check that the event is signed by the server sending the request.
-	redacted, err := verImpl.RedactEventJSON(event.JSON())
-	if err != nil {
+	if !cfg.Matrix.IsLocalServerName(invitedUser.Domain()) {
 		return util.JSONResponse{
 			Code: http.StatusBadRequest,
-			JSON: spec.BadJSON("The event JSON could not be redacted"),
+			JSON: spec.InvalidParam("The invited user domain does not belong to this server"),
 		}
 	}
-	_, serverName, err := gomatrixserverlib.SplitID('@', event.Sender())
-	if err != nil {
+
+	if event.EventID() != eventID {
 		return util.JSONResponse{
 			Code: http.StatusBadRequest,
-			JSON: spec.BadJSON("The event JSON contains an invalid sender"),
+			JSON: spec.BadJSON("The event ID in the request path must match the event ID in the invite event JSON"),
 		}
 	}
-	verifyRequests := []gomatrixserverlib.VerifyJSONRequest{{
-		ServerName:             serverName,
-		Message:                redacted,
-		AtTS:                   event.OriginServerTS(),
-		StrictValidityChecking: true,
-	}}
-	verifyResults, err := keys.VerifyJSONs(ctx, verifyRequests)
-	if err != nil {
-		util.GetLogger(ctx).WithError(err).Error("keys.VerifyJSONs failed")
-		return util.JSONResponse{
-			Code: http.StatusInternalServerError,
-			JSON: spec.InternalServerError{},
-		}
+
+	input := gomatrixserverlib.HandleInviteInput{
+		RoomVersion:       roomVer,
+		RoomID:            roomID,
+		InvitedUser:       *invitedUser,
+		KeyID:             cfg.Matrix.KeyID,
+		PrivateKey:        cfg.Matrix.PrivateKey,
+		Verifier:          keys,
+		RoomQuerier:       rsAPI,
+		MembershipQuerier: &api.MembershipQuerier{Roomserver: rsAPI},
+		StateQuerier:      rsAPI.StateQuerier(),
+		InviteEvent:       event,
+		StrippedState:     strippedState,
 	}
-	if verifyResults[0].Error != nil {
-		return util.JSONResponse{
-			Code: http.StatusForbidden,
-			JSON: spec.Forbidden("The invite must be signed by the server it originated on"),
-		}
+	event, jsonErr := handleInvite(httpReq.Context(), input, rsAPI)
+	if jsonErr != nil {
+		return *jsonErr
 	}
-
-	// Sign the event so that other servers will know that we have received the invite.
-	signedEvent := event.Sign(
-		string(domain), cfg.Matrix.KeyID, cfg.Matrix.PrivateKey,
-	)
-
-	// Add the invite event to the roomserver.
-	inviteEvent := &types.HeaderedEvent{PDU: signedEvent}
-	request := &api.PerformInviteRequest{
-		Event:           inviteEvent,
-		InviteRoomState: strippedState,
-		RoomVersion:     inviteEvent.Version(),
-		SendAsServer:    string(api.DoNotSendToOtherServers),
-		TransactionID:   nil,
+	return util.JSONResponse{
+		Code: http.StatusOK,
+		JSON: fclient.RespInvite{Event: event.JSON()},
 	}
+}
 
-	if err = rsAPI.PerformInvite(ctx, request); err != nil {
-		util.GetLogger(ctx).WithError(err).Error("PerformInvite failed")
-		return util.JSONResponse{
+func handleInvite(ctx context.Context, input gomatrixserverlib.HandleInviteInput, rsAPI api.FederationRoomserverAPI) (gomatrixserverlib.PDU, *util.JSONResponse) {
+	inviteEvent, err := gomatrixserverlib.HandleInvite(ctx, input)
+	switch e := err.(type) {
+	case nil:
+	case spec.InternalServerError:
+		util.GetLogger(ctx).WithError(err)
+		return nil, &util.JSONResponse{
 			Code: http.StatusInternalServerError,
 			JSON: spec.InternalServerError{},
 		}
-	}
-
-	switch e := err.(type) {
-	case api.ErrInvalidID:
-		return util.JSONResponse{
-			Code: http.StatusBadRequest,
-			JSON: spec.Unknown(e.Error()),
+	case spec.MatrixError:
+		util.GetLogger(ctx).WithError(err)
+		code := http.StatusInternalServerError
+		switch e.ErrCode {
+		case spec.ErrorForbidden:
+			code = http.StatusForbidden
+		case spec.ErrorUnsupportedRoomVersion:
+			fallthrough // http.StatusBadRequest
+		case spec.ErrorBadJSON:
+			code = http.StatusBadRequest
 		}
-	case api.ErrNotAllowed:
-		return util.JSONResponse{
-			Code: http.StatusForbidden,
-			JSON: spec.Forbidden(e.Error()),
+
+		return nil, &util.JSONResponse{
+			Code: code,
+			JSON: e,
 		}
-	case nil:
 	default:
-		util.GetLogger(ctx).WithError(err).Error("PerformInvite failed")
-		sentry.CaptureException(err)
-		return util.JSONResponse{
-			Code: http.StatusInternalServerError,
-			JSON: spec.InternalServerError{},
+		util.GetLogger(ctx).WithError(err)
+		return nil, &util.JSONResponse{
+			Code: http.StatusBadRequest,
+			JSON: spec.Unknown("unknown error"),
 		}
 	}
 
-	// Return the signed event to the originating server, it should then tell
-	// the other servers in the room that we have been invited.
-	if isInviteV2 {
-		return util.JSONResponse{
-			Code: http.StatusOK,
-			JSON: fclient.RespInviteV2{Event: signedEvent.JSON()},
-		}
-	} else {
-		return util.JSONResponse{
-			Code: http.StatusOK,
-			JSON: fclient.RespInvite{Event: signedEvent.JSON()},
+	headeredInvite := &types.HeaderedEvent{PDU: inviteEvent}
+	if err = rsAPI.HandleInvite(ctx, headeredInvite); err != nil {
+		util.GetLogger(ctx).WithError(err).Error("HandleInvite failed")
+		return nil, &util.JSONResponse{
+			Code: http.StatusInternalServerError,
+			JSON: spec.InternalServerError{},
 		}
 	}
+	return inviteEvent, nil
 }
diff --git a/federationapi/routing/join.go b/federationapi/routing/join.go
index 03d3309a..c6f96375 100644
--- a/federationapi/routing/join.go
+++ b/federationapi/routing/join.go
@@ -216,25 +216,6 @@ func MakeJoin(
 	}
 }
 
-type MembershipQuerier struct {
-	roomserver api.FederationRoomserverAPI
-}
-
-func (mq *MembershipQuerier) CurrentMembership(ctx context.Context, roomID spec.RoomID, userID spec.UserID) (string, error) {
-	req := api.QueryMembershipForUserRequest{
-		RoomID: roomID.String(),
-		UserID: userID.String(),
-	}
-	res := api.QueryMembershipForUserResponse{}
-	err := mq.roomserver.QueryMembershipForUser(ctx, &req, &res)
-
-	membership := ""
-	if err == nil {
-		membership = res.Membership
-	}
-	return membership, err
-}
-
 // SendJoin implements the /send_join API
 // The make-join send-join dance makes much more sense as a single
 // flow so the cyclomatic complexity is high:
@@ -268,7 +249,7 @@ func SendJoin(
 		KeyID:             cfg.Matrix.KeyID,
 		PrivateKey:        cfg.Matrix.PrivateKey,
 		Verifier:          keys,
-		MembershipQuerier: &MembershipQuerier{roomserver: rsAPI},
+		MembershipQuerier: &api.MembershipQuerier{Roomserver: rsAPI},
 	}
 	response, joinErr := gomatrixserverlib.HandleSendJoin(input)
 	switch e := joinErr.(type) {
diff --git a/federationapi/routing/routing.go b/federationapi/routing/routing.go
index fad06c1c..8865022f 100644
--- a/federationapi/routing/routing.go
+++ b/federationapi/routing/routing.go
@@ -152,8 +152,16 @@ func Setup(
 					JSON: spec.Forbidden("Forbidden by server ACLs"),
 				}
 			}
+
+			roomID, err := spec.NewRoomID(vars["roomID"])
+			if err != nil {
+				return util.JSONResponse{
+					Code: http.StatusBadRequest,
+					JSON: spec.InvalidParam("Invalid RoomID"),
+				}
+			}
 			return InviteV1(
-				httpReq, request, vars["roomID"], vars["eventID"],
+				httpReq, request, *roomID, vars["eventID"],
 				cfg, rsAPI, keys,
 			)
 		},
@@ -168,8 +176,16 @@ func Setup(
 					JSON: spec.Forbidden("Forbidden by server ACLs"),
 				}
 			}
+
+			roomID, err := spec.NewRoomID(vars["roomID"])
+			if err != nil {
+				return util.JSONResponse{
+					Code: http.StatusBadRequest,
+					JSON: spec.InvalidParam("Invalid RoomID"),
+				}
+			}
 			return InviteV2(
-				httpReq, request, vars["roomID"], vars["eventID"],
+				httpReq, request, *roomID, vars["eventID"],
 				cfg, rsAPI, keys,
 			)
 		},
diff --git a/go.mod b/go.mod
index 0e979de6..a20757bb 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 v0.0.0-20230531143710-c681a0658246
+	github.com/matrix-org/gomatrixserverlib v0.0.0-20230531155817-0e3adf17bee6
 	github.com/matrix-org/pinecone v0.11.1-0.20230210171230-8c3b24f2649a
 	github.com/matrix-org/util v0.0.0-20221111132719-399730281e66
 	github.com/mattn/go-sqlite3 v1.14.16
diff --git a/go.sum b/go.sum
index 8baa50e8..a1946ada 100644
--- a/go.sum
+++ b/go.sum
@@ -323,8 +323,8 @@ 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 v0.0.0-20230531143710-c681a0658246 h1:1sYXx7p9BIf0R7OIV/TZg3SCvNehEQPCKNqwV1ONfwU=
-github.com/matrix-org/gomatrixserverlib v0.0.0-20230531143710-c681a0658246/go.mod h1:H9V9N3Uqn1bBJqYJNGK1noqtgJTaCEhtTdcH/mp50uU=
+github.com/matrix-org/gomatrixserverlib v0.0.0-20230531155817-0e3adf17bee6 h1:Kh1TNvJDhWN5CdgtICNUC4G0wV2km51LGr46Dvl153A=
+github.com/matrix-org/gomatrixserverlib v0.0.0-20230531155817-0e3adf17bee6/go.mod h1:H9V9N3Uqn1bBJqYJNGK1noqtgJTaCEhtTdcH/mp50uU=
 github.com/matrix-org/pinecone v0.11.1-0.20230210171230-8c3b24f2649a h1:awrPDf9LEFySxTLKYBMCiObelNx/cBuv/wzllvCCH3A=
 github.com/matrix-org/pinecone v0.11.1-0.20230210171230-8c3b24f2649a/go.mod h1:HchJX9oKMXaT2xYFs0Ha/6Zs06mxLU8k6F1ODnrGkeQ=
 github.com/matrix-org/util v0.0.0-20221111132719-399730281e66 h1:6z4KxomXSIGWqhHcfzExgkH3Z3UkIXry4ibJS4Aqz2Y=
diff --git a/roomserver/api/api.go b/roomserver/api/api.go
index 571aa40b..7cb3379e 100644
--- a/roomserver/api/api.go
+++ b/roomserver/api/api.go
@@ -225,6 +225,8 @@ type FederationRoomserverAPI interface {
 	QueryRoomsForUser(ctx context.Context, req *QueryRoomsForUserRequest, res *QueryRoomsForUserResponse) error
 	QueryRestrictedJoinAllowed(ctx context.Context, req *QueryRestrictedJoinAllowedRequest, res *QueryRestrictedJoinAllowedResponse) error
 	PerformInboundPeek(ctx context.Context, req *PerformInboundPeekRequest, res *PerformInboundPeekResponse) error
+	HandleInvite(ctx context.Context, event *types.HeaderedEvent) error
+
 	PerformInvite(ctx context.Context, req *PerformInviteRequest) error
 	// Query a given amount (or less) of events prior to a given set of events.
 	PerformBackfill(ctx context.Context, req *PerformBackfillRequest, res *PerformBackfillResponse) error
@@ -234,6 +236,9 @@ type FederationRoomserverAPI interface {
 	QueryRoomInfo(ctx context.Context, roomID spec.RoomID) (*types.RoomInfo, error)
 	UserJoinedToRoom(ctx context.Context, roomID types.RoomNID, userID spec.UserID) (bool, error)
 	LocallyJoinedUsers(ctx context.Context, roomVersion gomatrixserverlib.RoomVersion, roomNID types.RoomNID) ([]gomatrixserverlib.PDU, error)
+
+	IsKnownRoom(ctx context.Context, roomID spec.RoomID) (bool, error)
+	StateQuerier() gomatrixserverlib.StateQuerier
 }
 
 type KeyserverRoomserverAPI interface {
diff --git a/roomserver/api/perform.go b/roomserver/api/perform.go
index 8d9742c6..6cbaf5b1 100644
--- a/roomserver/api/perform.go
+++ b/roomserver/api/perform.go
@@ -7,7 +7,6 @@ import (
 
 	"github.com/matrix-org/dendrite/roomserver/types"
 	"github.com/matrix-org/gomatrixserverlib"
-	"github.com/matrix-org/gomatrixserverlib/fclient"
 	"github.com/matrix-org/gomatrixserverlib/spec"
 	"github.com/matrix-org/util"
 )
@@ -52,11 +51,11 @@ type PerformLeaveResponse struct {
 }
 
 type PerformInviteRequest struct {
-	RoomVersion     gomatrixserverlib.RoomVersion   `json:"room_version"`
-	Event           *types.HeaderedEvent            `json:"event"`
-	InviteRoomState []fclient.InviteV2StrippedState `json:"invite_room_state"`
-	SendAsServer    string                          `json:"send_as_server"`
-	TransactionID   *TransactionID                  `json:"transaction_id"`
+	RoomVersion     gomatrixserverlib.RoomVersion           `json:"room_version"`
+	Event           *types.HeaderedEvent                    `json:"event"`
+	InviteRoomState []gomatrixserverlib.InviteStrippedState `json:"invite_room_state"`
+	SendAsServer    string                                  `json:"send_as_server"`
+	TransactionID   *TransactionID                          `json:"transaction_id"`
 }
 
 type PerformPeekRequest struct {
diff --git a/roomserver/api/query.go b/roomserver/api/query.go
index 1726bfe1..b33698c8 100644
--- a/roomserver/api/query.go
+++ b/roomserver/api/query.go
@@ -17,6 +17,7 @@
 package api
 
 import (
+	"context"
 	"encoding/json"
 	"fmt"
 	"strings"
@@ -457,3 +458,22 @@ type QueryLeftUsersRequest struct {
 type QueryLeftUsersResponse struct {
 	LeftUsers []string `json:"user_ids"`
 }
+
+type MembershipQuerier struct {
+	Roomserver FederationRoomserverAPI
+}
+
+func (mq *MembershipQuerier) CurrentMembership(ctx context.Context, roomID spec.RoomID, userID spec.UserID) (string, error) {
+	req := QueryMembershipForUserRequest{
+		RoomID: roomID.String(),
+		UserID: userID.String(),
+	}
+	res := QueryMembershipForUserResponse{}
+	err := mq.Roomserver.QueryMembershipForUser(ctx, &req, &res)
+
+	membership := ""
+	if err == nil {
+		membership = res.Membership
+	}
+	return membership, err
+}
diff --git a/roomserver/internal/api.go b/roomserver/internal/api.go
index f61f8918..ee433f0d 100644
--- a/roomserver/internal/api.go
+++ b/roomserver/internal/api.go
@@ -20,6 +20,7 @@ import (
 	"github.com/matrix-org/dendrite/roomserver/internal/query"
 	"github.com/matrix-org/dendrite/roomserver/producers"
 	"github.com/matrix-org/dendrite/roomserver/storage"
+	"github.com/matrix-org/dendrite/roomserver/types"
 	"github.com/matrix-org/dendrite/setup/config"
 	"github.com/matrix-org/dendrite/setup/jetstream"
 	"github.com/matrix-org/dendrite/setup/process"
@@ -132,6 +133,7 @@ func (r *RoomserverInternalAPI) SetFederationAPI(fsAPI fsAPI.RoomserverFederatio
 		DB:      r.DB,
 		Cfg:     &r.Cfg.RoomServer,
 		FSAPI:   r.fsAPI,
+		RSAPI:   r,
 		Inputer: r.Inputer,
 	}
 	r.Joiner = &perform.Joiner{
@@ -213,6 +215,24 @@ func (r *RoomserverInternalAPI) SetAppserviceAPI(asAPI asAPI.AppServiceInternalA
 	r.asAPI = asAPI
 }
 
+func (r *RoomserverInternalAPI) IsKnownRoom(ctx context.Context, roomID spec.RoomID) (bool, error) {
+	return r.Inviter.IsKnownRoom(ctx, roomID)
+}
+
+func (r *RoomserverInternalAPI) StateQuerier() gomatrixserverlib.StateQuerier {
+	return r.Inviter.StateQuerier()
+}
+
+func (r *RoomserverInternalAPI) HandleInvite(
+	ctx context.Context, inviteEvent *types.HeaderedEvent,
+) error {
+	outputEvents, err := r.Inviter.ProcessInviteMembership(ctx, inviteEvent)
+	if err != nil {
+		return err
+	}
+	return r.OutputProducer.ProduceRoomEvents(inviteEvent.RoomID(), outputEvents)
+}
+
 func (r *RoomserverInternalAPI) PerformCreateRoom(
 	ctx context.Context, userID spec.UserID, roomID spec.RoomID, createRequest *api.PerformCreateRoomRequest,
 ) (string, *util.JSONResponse) {
@@ -223,14 +243,7 @@ func (r *RoomserverInternalAPI) PerformInvite(
 	ctx context.Context,
 	req *api.PerformInviteRequest,
 ) error {
-	outputEvents, err := r.Inviter.PerformInvite(ctx, req)
-	if err != nil {
-		return err
-	}
-	if len(outputEvents) == 0 {
-		return nil
-	}
-	return r.OutputProducer.ProduceRoomEvents(req.Event.RoomID(), outputEvents)
+	return r.Inviter.PerformInvite(ctx, req)
 }
 
 func (r *RoomserverInternalAPI) PerformLeave(
diff --git a/roomserver/internal/helpers/auth.go b/roomserver/internal/helpers/auth.go
index 24958091..7ec0892e 100644
--- a/roomserver/internal/helpers/auth.go
+++ b/roomserver/internal/helpers/auth.go
@@ -70,7 +70,7 @@ func CheckForSoftFail(
 	)
 
 	// Load the actual auth events from the database.
-	authEvents, err := loadAuthEvents(ctx, db, roomInfo, stateNeeded, authStateEntries)
+	authEvents, err := loadAuthEvents(ctx, db, roomInfo.RoomVersion, stateNeeded, authStateEntries)
 	if err != nil {
 		return true, fmt.Errorf("loadAuthEvents: %w", err)
 	}
@@ -83,15 +83,14 @@ func CheckForSoftFail(
 	return false, nil
 }
 
-// CheckAuthEvents checks that the event passes authentication checks
-// Returns the numeric IDs for the auth events.
-func CheckAuthEvents(
+// GetAuthEvents returns the numeric IDs for the auth events.
+func GetAuthEvents(
 	ctx context.Context,
 	db storage.RoomDatabase,
-	roomInfo *types.RoomInfo,
-	event *types.HeaderedEvent,
+	roomVersion gomatrixserverlib.RoomVersion,
+	event gomatrixserverlib.PDU,
 	authEventIDs []string,
-) ([]types.EventNID, error) {
+) (gomatrixserverlib.AuthEventProvider, error) {
 	// Grab the numeric IDs for the supplied auth state events from the database.
 	authStateEntries, err := db.StateEntriesForEventIDs(ctx, authEventIDs, true)
 	if err != nil {
@@ -100,25 +99,14 @@ func CheckAuthEvents(
 	authStateEntries = types.DeduplicateStateEntries(authStateEntries)
 
 	// Work out which of the state events we actually need.
-	stateNeeded := gomatrixserverlib.StateNeededForAuth([]gomatrixserverlib.PDU{event.PDU})
+	stateNeeded := gomatrixserverlib.StateNeededForAuth([]gomatrixserverlib.PDU{event})
 
 	// Load the actual auth events from the database.
-	authEvents, err := loadAuthEvents(ctx, db, roomInfo, stateNeeded, authStateEntries)
+	authEvents, err := loadAuthEvents(ctx, db, roomVersion, stateNeeded, authStateEntries)
 	if err != nil {
 		return nil, fmt.Errorf("loadAuthEvents: %w", err)
 	}
-
-	// Check if the event is allowed.
-	if err = gomatrixserverlib.Allowed(event.PDU, &authEvents); err != nil {
-		return nil, err
-	}
-
-	// Return the numeric IDs for the auth events.
-	result := make([]types.EventNID, len(authStateEntries))
-	for i := range authStateEntries {
-		result[i] = authStateEntries[i].EventNID
-	}
-	return result, nil
+	return &authEvents, nil
 }
 
 type authEvents struct {
@@ -196,7 +184,7 @@ func (ae *authEvents) lookupEvent(typeNID types.EventTypeNID, stateKey string) g
 func loadAuthEvents(
 	ctx context.Context,
 	db state.StateResolutionStorage,
-	roomInfo *types.RoomInfo,
+	roomVersion gomatrixserverlib.RoomVersion,
 	needed gomatrixserverlib.StateNeeded,
 	state []types.StateEntry,
 ) (result authEvents, err error) {
@@ -220,11 +208,7 @@ func loadAuthEvents(
 		}
 	}
 
-	if roomInfo == nil {
-		err = types.ErrorInvalidRoomInfo
-		return
-	}
-	if result.events, err = db.Events(ctx, roomInfo.RoomVersion, eventNIDs); err != nil {
+	if result.events, err = db.Events(ctx, roomVersion, eventNIDs); err != nil {
 		return
 	}
 	roomID := ""
diff --git a/roomserver/internal/perform/perform_create_room.go b/roomserver/internal/perform/perform_create_room.go
index 0f917008..41194832 100644
--- a/roomserver/internal/perform/perform_create_room.go
+++ b/roomserver/internal/perform/perform_create_room.go
@@ -376,7 +376,7 @@ func (c *Creator) PerformCreateRoom(ctx context.Context, userID spec.UserID, roo
 	// If this is a direct message then we should invite the participants.
 	if len(createRequest.InvitedUsers) > 0 {
 		// Build some stripped state for the invite.
-		var globalStrippedState []fclient.InviteV2StrippedState
+		var globalStrippedState []gomatrixserverlib.InviteStrippedState
 		for _, event := range builtEvents {
 			// Chosen events from the spec:
 			// https://spec.matrix.org/v1.3/client-server-api/#stripped-state
@@ -399,7 +399,7 @@ func (c *Creator) PerformCreateRoom(ctx context.Context, userID spec.UserID, roo
 				ev := event.PDU
 				globalStrippedState = append(
 					globalStrippedState,
-					fclient.NewInviteV2StrippedState(ev),
+					gomatrixserverlib.NewInviteStrippedState(ev),
 				)
 			}
 		}
@@ -443,7 +443,7 @@ func (c *Creator) PerformCreateRoom(ctx context.Context, userID spec.UserID, roo
 			}
 			inviteStrippedState := append(
 				globalStrippedState,
-				fclient.NewInviteV2StrippedState(inviteEvent.PDU),
+				gomatrixserverlib.NewInviteStrippedState(inviteEvent.PDU),
 			)
 			// Send the invite event to the roomserver.
 			event := inviteEvent
diff --git a/roomserver/internal/perform/perform_invite.go b/roomserver/internal/perform/perform_invite.go
index a3fa2e01..1930b5ac 100644
--- a/roomserver/internal/perform/perform_invite.go
+++ b/roomserver/internal/perform/perform_invite.go
@@ -28,186 +28,149 @@ import (
 	"github.com/matrix-org/dendrite/roomserver/types"
 	"github.com/matrix-org/dendrite/setup/config"
 	"github.com/matrix-org/gomatrixserverlib"
-	"github.com/matrix-org/gomatrixserverlib/fclient"
 	"github.com/matrix-org/gomatrixserverlib/spec"
 	"github.com/matrix-org/util"
-	log "github.com/sirupsen/logrus"
 )
 
+type QueryState struct {
+	storage.Database
+}
+
+func (q *QueryState) GetAuthEvents(ctx context.Context, event gomatrixserverlib.PDU) (gomatrixserverlib.AuthEventProvider, error) {
+	return helpers.GetAuthEvents(ctx, q.Database, event.Version(), event, event.AuthEventIDs())
+}
+
+func (q *QueryState) GetState(ctx context.Context, roomID spec.RoomID, stateWanted []gomatrixserverlib.StateKeyTuple) ([]gomatrixserverlib.PDU, error) {
+	info, err := q.Database.RoomInfo(ctx, roomID.String())
+	if err != nil {
+		return nil, fmt.Errorf("failed to load RoomInfo: %w", err)
+	}
+	if info != nil {
+		roomState := state.NewStateResolution(q.Database, info)
+		stateEntries, err := roomState.LoadStateAtSnapshotForStringTuples(
+			ctx, info.StateSnapshotNID(), stateWanted,
+		)
+		if err != nil {
+			return nil, nil
+		}
+		stateNIDs := []types.EventNID{}
+		for _, stateNID := range stateEntries {
+			stateNIDs = append(stateNIDs, stateNID.EventNID)
+		}
+		stateEvents, err := q.Database.Events(ctx, info.RoomVersion, stateNIDs)
+		if err != nil {
+			return nil, fmt.Errorf("failed to obtain required events: %w", err)
+		}
+
+		events := []gomatrixserverlib.PDU{}
+		for _, event := range stateEvents {
+			events = append(events, event.PDU)
+		}
+		return events, nil
+	}
+
+	return nil, nil
+}
+
 type Inviter struct {
 	DB      storage.Database
 	Cfg     *config.RoomServer
 	FSAPI   federationAPI.RoomserverFederationAPI
+	RSAPI   api.RoomserverInternalAPI
 	Inputer *input.Inputer
 }
 
-// nolint:gocyclo
-func (r *Inviter) PerformInvite(
-	ctx context.Context,
-	req *api.PerformInviteRequest,
-) ([]api.OutputEvent, error) {
-	var outputUpdates []api.OutputEvent
-	event := req.Event
-	if event.StateKey() == nil {
-		return nil, fmt.Errorf("invite must be a state event")
-	}
-	_, senderDomain, err := gomatrixserverlib.SplitID('@', event.Sender())
+func (r *Inviter) IsKnownRoom(ctx context.Context, roomID spec.RoomID) (bool, error) {
+	info, err := r.DB.RoomInfo(ctx, roomID.String())
 	if err != nil {
-		return nil, fmt.Errorf("sender %q is invalid", event.Sender())
+		return false, fmt.Errorf("failed to load RoomInfo: %w", err)
 	}
+	return (info != nil && !info.IsStub()), nil
+}
 
-	roomID := event.RoomID()
-	targetUserID := *event.StateKey()
-	info, err := r.DB.RoomInfo(ctx, roomID)
-	if err != nil {
-		return nil, fmt.Errorf("failed to load RoomInfo: %w", err)
-	}
+func (r *Inviter) StateQuerier() gomatrixserverlib.StateQuerier {
+	return &QueryState{Database: r.DB}
+}
 
-	_, domain, err := gomatrixserverlib.SplitID('@', targetUserID)
+func (r *Inviter) ProcessInviteMembership(
+	ctx context.Context, inviteEvent *types.HeaderedEvent,
+) ([]api.OutputEvent, error) {
+	var outputUpdates []api.OutputEvent
+	var updater *shared.MembershipUpdater
+	_, domain, err := gomatrixserverlib.SplitID('@', *inviteEvent.StateKey())
 	if err != nil {
-		return nil, api.ErrInvalidID{Err: fmt.Errorf("the user ID %s is invalid", targetUserID)}
+		return nil, api.ErrInvalidID{Err: fmt.Errorf("the user ID %s is invalid", *inviteEvent.StateKey())}
 	}
 	isTargetLocal := r.Cfg.Matrix.IsLocalServerName(domain)
-	isOriginLocal := r.Cfg.Matrix.IsLocalServerName(senderDomain)
-	if !isOriginLocal && !isTargetLocal {
-		return nil, api.ErrInvalidID{Err: fmt.Errorf("the invite must be either from or to a local user")}
+	if updater, err = r.DB.MembershipUpdater(ctx, inviteEvent.RoomID(), *inviteEvent.StateKey(), isTargetLocal, inviteEvent.Version()); err != nil {
+		return nil, fmt.Errorf("r.DB.MembershipUpdater: %w", err)
 	}
-
-	logger := util.GetLogger(ctx).WithFields(map[string]interface{}{
-		"inviter":  event.Sender(),
-		"invitee":  *event.StateKey(),
-		"room_id":  roomID,
-		"event_id": event.EventID(),
-	})
-	logger.WithFields(log.Fields{
-		"room_version":     req.RoomVersion,
-		"room_info_exists": info != nil,
-		"target_local":     isTargetLocal,
-		"origin_local":     isOriginLocal,
-	}).Debug("processing invite event")
-
-	inviteState := req.InviteRoomState
-	if len(inviteState) == 0 && info != nil {
-		var is []fclient.InviteV2StrippedState
-		if is, err = buildInviteStrippedState(ctx, r.DB, info, req); err == nil {
-			inviteState = is
-		}
+	outputUpdates, err = helpers.UpdateToInviteMembership(updater, &types.Event{
+		EventNID: 0,
+		PDU:      inviteEvent.PDU,
+	}, outputUpdates, inviteEvent.Version())
+	if err != nil {
+		return nil, fmt.Errorf("updateToInviteMembership: %w", err)
 	}
-	if len(inviteState) == 0 {
-		if err = event.SetUnsignedField("invite_room_state", struct{}{}); err != nil {
-			return nil, fmt.Errorf("event.SetUnsignedField: %w", err)
-		}
-	} else {
-		if err = event.SetUnsignedField("invite_room_state", inviteState); err != nil {
-			return nil, fmt.Errorf("event.SetUnsignedField: %w", err)
-		}
+	if err = updater.Commit(); err != nil {
+		return nil, fmt.Errorf("updater.Commit: %w", err)
 	}
+	return outputUpdates, nil
+}
 
-	updateMembershipTableManually := func() ([]api.OutputEvent, error) {
-		var updater *shared.MembershipUpdater
-		if updater, err = r.DB.MembershipUpdater(ctx, roomID, targetUserID, isTargetLocal, req.RoomVersion); err != nil {
-			return nil, fmt.Errorf("r.DB.MembershipUpdater: %w", err)
-		}
-		outputUpdates, err = helpers.UpdateToInviteMembership(updater, &types.Event{
-			EventNID: 0,
-			PDU:      event.PDU,
-		}, outputUpdates, req.Event.Version())
-		if err != nil {
-			return nil, fmt.Errorf("updateToInviteMembership: %w", err)
-		}
-		if err = updater.Commit(); err != nil {
-			return nil, fmt.Errorf("updater.Commit: %w", err)
-		}
-		logger.Debugf("updated membership to invite and sending invite OutputEvent")
-		return outputUpdates, nil
-	}
+// nolint:gocyclo
+func (r *Inviter) PerformInvite(
+	ctx context.Context,
+	req *api.PerformInviteRequest,
+) error {
+	event := req.Event
 
-	if (info == nil || info.IsStub()) && !isOriginLocal && isTargetLocal {
-		// The invite came in over federation for a room that we don't know about
-		// yet. We need to handle this a bit differently to most invites because
-		// we don't know the room state, therefore the roomserver can't process
-		// an input event. Instead we will update the membership table with the
-		// new invite and generate an output event.
-		return updateMembershipTableManually()
+	sender, err := spec.NewUserID(event.Sender(), true)
+	if err != nil {
+		return spec.InvalidParam("The user ID is invalid")
+	}
+	if !r.Cfg.Matrix.IsLocalServerName(sender.Domain()) {
+		return api.ErrInvalidID{Err: fmt.Errorf("the invite must be from a local user")}
 	}
 
-	var isAlreadyJoined bool
-	if info != nil {
-		_, isAlreadyJoined, _, err = r.DB.GetMembership(ctx, info.RoomNID, *event.StateKey())
-		if err != nil {
-			return nil, fmt.Errorf("r.DB.GetMembership: %w", err)
-		}
+	if event.StateKey() == nil {
+		return fmt.Errorf("invite must be a state event")
 	}
-	if isAlreadyJoined {
-		// If the user is joined to the room then that takes precedence over this
-		// invite event. It makes little sense to move a user that is already
-		// joined to the room into the invite state.
-		// This could plausibly happen if an invite request raced with a join
-		// request for a user. For example if a user was invited to a public
-		// room and they joined the room at the same time as the invite was sent.
-		// The other way this could plausibly happen is if an invite raced with
-		// a kick. For example if a user was kicked from a room in error and in
-		// response someone else in the room re-invited them then it is possible
-		// for the invite request to race with the leave event so that the
-		// target receives invite before it learns that it has been kicked.
-		// There are a few ways this could be plausibly handled in the roomserver.
-		// 1) Store the invite, but mark it as retired. That will result in the
-		//    permanent rejection of that invite event. So even if the target
-		//    user leaves the room and the invite is retransmitted it will be
-		//    ignored. However a new invite with a new event ID would still be
-		//    accepted.
-		// 2) Silently discard the invite event. This means that if the event
-		//    was retransmitted at a later date after the target user had left
-		//    the room we would accept the invite. However since we hadn't told
-		//    the sending server that the invite had been discarded it would
-		//    have no reason to attempt to retry.
-		// 3) Signal the sending server that the user is already joined to the
-		//    room.
-		// For now we will implement option 2. Since in the abesence of a retry
-		// mechanism it will be equivalent to option 1, and we don't have a
-		// signalling mechanism to implement option 3.
-		logger.Debugf("user already joined")
-		return nil, api.ErrNotAllowed{Err: fmt.Errorf("user is already joined to room")}
+	invitedUser, err := spec.NewUserID(*event.StateKey(), true)
+	if err != nil {
+		return spec.InvalidParam("The user ID is invalid")
 	}
+	isTargetLocal := r.Cfg.Matrix.IsLocalServerName(invitedUser.Domain())
 
-	// If the invite originated remotely then we can't send an
-	// InputRoomEvent for the invite as it will never pass auth checks
-	// due to lacking room state, but we still need to tell the client
-	// about the invite so we can accept it, hence we return an output
-	// event to send to the Sync API.
-	if !isOriginLocal {
-		return updateMembershipTableManually()
+	validRoomID, err := spec.NewRoomID(event.RoomID())
+	if err != nil {
+		return err
 	}
 
-	// The invite originated locally. Therefore we have a responsibility to
-	// try and see if the user is allowed to make this invite. We can't do
-	// this for invites coming in over federation - we have to take those on
-	// trust.
-	_, err = helpers.CheckAuthEvents(ctx, r.DB, info, event, event.AuthEventIDs())
+	input := gomatrixserverlib.PerformInviteInput{
+		RoomID:            *validRoomID,
+		InviteEvent:       event.PDU,
+		InvitedUser:       *invitedUser,
+		IsTargetLocal:     isTargetLocal,
+		StrippedState:     req.InviteRoomState,
+		MembershipQuerier: &api.MembershipQuerier{Roomserver: r.RSAPI},
+		StateQuerier:      &QueryState{r.DB},
+	}
+	inviteEvent, err := gomatrixserverlib.PerformInvite(ctx, input, r.FSAPI)
 	if err != nil {
-		logger.WithError(err).WithField("event_id", event.EventID()).WithField("auth_event_ids", event.AuthEventIDs()).Error(
-			"processInviteEvent.checkAuthEvents failed for event",
-		)
-		return nil, api.ErrNotAllowed{Err: err}
+		switch e := err.(type) {
+		case spec.MatrixError:
+			if e.ErrCode == spec.ErrorForbidden {
+				return api.ErrNotAllowed{Err: fmt.Errorf("%s", e.Err)}
+			}
+		}
+		return err
 	}
 
-	// If the invite originated from us and the target isn't local then we
-	// should try and send the invite over federation first. It might be
-	// that the remote user doesn't exist, in which case we can give up
-	// processing here.
-	if req.SendAsServer != api.DoNotSendToOtherServers && !isTargetLocal {
-		fsReq := &federationAPI.PerformInviteRequest{
-			RoomVersion:     req.RoomVersion,
-			Event:           event,
-			InviteRoomState: inviteState,
-		}
-		fsRes := &federationAPI.PerformInviteResponse{}
-		if err = r.FSAPI.PerformInvite(ctx, fsReq, fsRes); err != nil {
-			logger.WithError(err).WithField("event_id", event.EventID()).Error("r.FSAPI.PerformInvite failed")
-			return nil, api.ErrNotAllowed{Err: err}
-		}
-		event = fsRes.Event
-		logger.Debugf("Federated PerformInvite success with event ID %s", event.EventID())
+	// Use the returned event if there was one (due to federation), otherwise
+	// send the original invite event to the roomserver.
+	if inviteEvent == nil {
+		inviteEvent = event
 	}
 
 	// Send the invite event to the roomserver input stream. This will
@@ -219,67 +182,18 @@ func (r *Inviter) PerformInvite(
 		InputRoomEvents: []api.InputRoomEvent{
 			{
 				Kind:         api.KindNew,
-				Event:        event,
-				Origin:       senderDomain,
+				Event:        &types.HeaderedEvent{PDU: inviteEvent},
+				Origin:       sender.Domain(),
 				SendAsServer: req.SendAsServer,
 			},
 		},
 	}
 	inputRes := &api.InputRoomEventsResponse{}
 	r.Inputer.InputRoomEvents(context.Background(), inputReq, inputRes)
-	if err = inputRes.Err(); err != nil {
-		logger.WithError(err).WithField("event_id", event.EventID()).Error("r.InputRoomEvents failed")
-		return nil, api.ErrNotAllowed{Err: err}
+	if err := inputRes.Err(); err != nil {
+		util.GetLogger(ctx).WithField("event_id", event.EventID()).Error("r.InputRoomEvents failed")
+		return api.ErrNotAllowed{Err: err}
 	}
 
-	// Don't notify the sync api of this event in the same way as a federated invite so the invitee
-	// gets the invite, as the roomserver will do this when it processes the m.room.member invite.
-	return outputUpdates, nil
-}
-
-func buildInviteStrippedState(
-	ctx context.Context,
-	db storage.Database,
-	info *types.RoomInfo,
-	input *api.PerformInviteRequest,
-) ([]fclient.InviteV2StrippedState, error) {
-	stateWanted := []gomatrixserverlib.StateKeyTuple{}
-	// "If they are set on the room, at least the state for m.room.avatar, m.room.canonical_alias, m.room.join_rules, and m.room.name SHOULD be included."
-	// https://matrix.org/docs/spec/client_server/r0.6.0#m-room-member
-	for _, t := range []string{
-		spec.MRoomName, spec.MRoomCanonicalAlias,
-		spec.MRoomJoinRules, spec.MRoomAvatar,
-		spec.MRoomEncryption, spec.MRoomCreate,
-	} {
-		stateWanted = append(stateWanted, gomatrixserverlib.StateKeyTuple{
-			EventType: t,
-			StateKey:  "",
-		})
-	}
-	roomState := state.NewStateResolution(db, info)
-	stateEntries, err := roomState.LoadStateAtSnapshotForStringTuples(
-		ctx, info.StateSnapshotNID(), stateWanted,
-	)
-	if err != nil {
-		return nil, err
-	}
-	stateNIDs := []types.EventNID{}
-	for _, stateNID := range stateEntries {
-		stateNIDs = append(stateNIDs, stateNID.EventNID)
-	}
-	if info == nil {
-		return nil, types.ErrorInvalidRoomInfo
-	}
-	stateEvents, err := db.Events(ctx, info.RoomVersion, stateNIDs)
-	if err != nil {
-		return nil, err
-	}
-	inviteState := []fclient.InviteV2StrippedState{
-		fclient.NewInviteV2StrippedState(input.Event.PDU),
-	}
-	stateEvents = append(stateEvents, types.Event{PDU: input.Event.PDU})
-	for _, event := range stateEvents {
-		inviteState = append(inviteState, fclient.NewInviteV2StrippedState(event.PDU))
-	}
-	return inviteState, nil
+	return nil
 }