Move MakeJoin logic to GMSL (#3081)

46 files changed, 597 insertions, 200 deletions

diff --git a/clientapi/auth/auth.go b/clientapi/auth/auth.go
index 479b9ac7..8fae45b8 100644
--- a/clientapi/auth/auth.go
+++ b/clientapi/auth/auth.go
@@ -68,8 +68,10 @@ func VerifyUserFromRequest(
 	}, &res)
 	if err != nil {
 		util.GetLogger(req.Context()).WithError(err).Error("userAPI.QueryAccessToken failed")
-		jsonErr := spec.InternalServerError()
-		return nil, &jsonErr
+		return nil, &util.JSONResponse{
+			Code: http.StatusInternalServerError,
+			JSON: spec.InternalServerError{},
+		}
 	}
 	if res.Err != "" {
 		if strings.HasPrefix(strings.ToLower(res.Err), "forbidden:") { // TODO: use actual error and no string comparison
diff --git a/clientapi/auth/login_test.go b/clientapi/auth/login_test.go
index eb87d5e8..93d3e271 100644
--- a/clientapi/auth/login_test.go
+++ b/clientapi/auth/login_test.go
@@ -107,13 +107,13 @@ func TestBadLoginFromJSONReader(t *testing.T) {
 		Name string
 		Body string
 
-		WantErrCode string
+		WantErrCode spec.MatrixErrorCode
 	}{
-		{Name: "empty", WantErrCode: "M_BAD_JSON"},
+		{Name: "empty", WantErrCode: spec.ErrorBadJSON},
 		{
 			Name:        "badUnmarshal",
 			Body:        `badsyntaxJSON`,
-			WantErrCode: "M_BAD_JSON",
+			WantErrCode: spec.ErrorBadJSON,
 		},
 		{
 			Name: "badPassword",
@@ -123,7 +123,7 @@ func TestBadLoginFromJSONReader(t *testing.T) {
 				"password": "invalidpassword",
 				"device_id": "adevice"
             }`,
-			WantErrCode: "M_FORBIDDEN",
+			WantErrCode: spec.ErrorForbidden,
 		},
 		{
 			Name: "badToken",
@@ -132,7 +132,7 @@ func TestBadLoginFromJSONReader(t *testing.T) {
 				"token": "invalidtoken",
 				"device_id": "adevice"
             }`,
-			WantErrCode: "M_FORBIDDEN",
+			WantErrCode: spec.ErrorForbidden,
 		},
 		{
 			Name: "badType",
@@ -140,7 +140,7 @@ func TestBadLoginFromJSONReader(t *testing.T) {
 				"type": "m.login.invalid",
 				"device_id": "adevice"
             }`,
-			WantErrCode: "M_INVALID_PARAM",
+			WantErrCode: spec.ErrorInvalidParam,
 		},
 	}
 	for _, tst := range tsts {
@@ -157,7 +157,7 @@ func TestBadLoginFromJSONReader(t *testing.T) {
 			if errRes == nil {
 				cleanup(ctx, nil)
 				t.Fatalf("LoginFromJSONReader err: got %+v, want code %q", errRes, tst.WantErrCode)
-			} else if merr, ok := errRes.JSON.(*spec.MatrixError); ok && merr.ErrCode != tst.WantErrCode {
+			} else if merr, ok := errRes.JSON.(spec.MatrixError); ok && merr.ErrCode != tst.WantErrCode {
 				t.Fatalf("LoginFromJSONReader err: got %+v, want code %q", errRes, tst.WantErrCode)
 			}
 		})
diff --git a/clientapi/auth/login_token.go b/clientapi/auth/login_token.go
index 073f728d..eb631481 100644
--- a/clientapi/auth/login_token.go
+++ b/clientapi/auth/login_token.go
@@ -48,8 +48,10 @@ func (t *LoginTypeToken) LoginFromJSON(ctx context.Context, reqBytes []byte) (*L
 	var res uapi.QueryLoginTokenResponse
 	if err := t.UserAPI.QueryLoginToken(ctx, &uapi.QueryLoginTokenRequest{Token: r.Token}, &res); err != nil {
 		util.GetLogger(ctx).WithError(err).Error("UserAPI.QueryLoginToken failed")
-		jsonErr := spec.InternalServerError()
-		return nil, nil, &jsonErr
+		return nil, nil, &util.JSONResponse{
+			Code: http.StatusInternalServerError,
+			JSON: spec.InternalServerError{},
+		}
 	}
 	if res.Data == nil {
 		return nil, nil, &util.JSONResponse{
diff --git a/clientapi/auth/user_interactive.go b/clientapi/auth/user_interactive.go
index 58d34865..92d83ad2 100644
--- a/clientapi/auth/user_interactive.go
+++ b/clientapi/auth/user_interactive.go
@@ -178,8 +178,10 @@ func (u *UserInteractive) NewSession() *util.JSONResponse {
 	sessionID, err := GenerateAccessToken()
 	if err != nil {
 		logrus.WithError(err).Error("failed to generate session ID")
-		res := spec.InternalServerError()
-		return &res
+		return &util.JSONResponse{
+			Code: http.StatusInternalServerError,
+			JSON: spec.InternalServerError{},
+		}
 	}
 	u.Lock()
 	u.Sessions[sessionID] = []string{}
@@ -193,15 +195,19 @@ func (u *UserInteractive) ResponseWithChallenge(sessionID string, response inter
 	mixedObjects := make(map[string]interface{})
 	b, err := json.Marshal(response)
 	if err != nil {
-		ise := spec.InternalServerError()
-		return &ise
+		return &util.JSONResponse{
+			Code: http.StatusInternalServerError,
+			JSON: spec.InternalServerError{},
+		}
 	}
 	_ = json.Unmarshal(b, &mixedObjects)
 	challenge := u.challenge(sessionID)
 	b, err = json.Marshal(challenge.JSON)
 	if err != nil {
-		ise := spec.InternalServerError()
-		return &ise
+		return &util.JSONResponse{
+			Code: http.StatusInternalServerError,
+			JSON: spec.InternalServerError{},
+		}
 	}
 	_ = json.Unmarshal(b, &mixedObjects)
 
diff --git a/clientapi/clientapi_test.go b/clientapi/clientapi_test.go
index 2c34c109..b339818a 100644
--- a/clientapi/clientapi_test.go
+++ b/clientapi/clientapi_test.go
@@ -33,6 +33,7 @@ import (
 	uapi "github.com/matrix-org/dendrite/userapi/api"
 	"github.com/matrix-org/gomatrix"
 	"github.com/matrix-org/gomatrixserverlib"
+	"github.com/matrix-org/gomatrixserverlib/spec"
 	"github.com/matrix-org/util"
 	"github.com/stretchr/testify/assert"
 	"github.com/tidwall/gjson"
@@ -1105,7 +1106,7 @@ func Test3PID(t *testing.T) {
 				resp := threepid.GetValidatedResponse{}
 				switch r.URL.Query().Get("client_secret") {
 				case "fail":
-					resp.ErrCode = "M_SESSION_NOT_VALIDATED"
+					resp.ErrCode = string(spec.ErrorSessionNotValidated)
 				case "fail2":
 					resp.ErrCode = "some other error"
 				case "fail3":
diff --git a/clientapi/httputil/httputil.go b/clientapi/httputil/httputil.go
index aea0c3db..d9f44232 100644
--- a/clientapi/httputil/httputil.go
+++ b/clientapi/httputil/httputil.go
@@ -32,8 +32,10 @@ func UnmarshalJSONRequest(req *http.Request, iface interface{}) *util.JSONRespon
 	body, err := io.ReadAll(req.Body)
 	if err != nil {
 		util.GetLogger(req.Context()).WithError(err).Error("io.ReadAll failed")
-		resp := spec.InternalServerError()
-		return &resp
+		return &util.JSONResponse{
+			Code: http.StatusInternalServerError,
+			JSON: spec.InternalServerError{},
+		}
 	}
 
 	return UnmarshalJSON(body, iface)
diff --git a/clientapi/routing/account_data.go b/clientapi/routing/account_data.go
index 572b28ef..7eacf9cc 100644
--- a/clientapi/routing/account_data.go
+++ b/clientapi/routing/account_data.go
@@ -104,7 +104,10 @@ func SaveAccountData(
 	body, err := io.ReadAll(req.Body)
 	if err != nil {
 		util.GetLogger(req.Context()).WithError(err).Error("io.ReadAll failed")
-		return spec.InternalServerError()
+		return util.JSONResponse{
+			Code: http.StatusInternalServerError,
+			JSON: spec.InternalServerError{},
+		}
 	}
 
 	if !json.Valid(body) {
@@ -157,7 +160,10 @@ func SaveReadMarker(
 	if r.FullyRead != "" {
 		data, err := json.Marshal(fullyReadEvent{EventID: r.FullyRead})
 		if err != nil {
-			return spec.InternalServerError()
+			return util.JSONResponse{
+				Code: http.StatusInternalServerError,
+				JSON: spec.InternalServerError{},
+			}
 		}
 
 		dataReq := api.InputAccountDataRequest{
diff --git a/clientapi/routing/admin.go b/clientapi/routing/admin.go
index 4d2cea68..8dd662a1 100644
--- a/clientapi/routing/admin.go
+++ b/clientapi/routing/admin.go
@@ -31,7 +31,7 @@ func AdminEvacuateRoom(req *http.Request, rsAPI roomserverAPI.ClientRoomserverAP
 	}
 
 	affected, err := rsAPI.PerformAdminEvacuateRoom(req.Context(), vars["roomID"])
-	switch err {
+	switch err.(type) {
 	case nil:
 	case eventutil.ErrRoomNoExists:
 		return util.JSONResponse{
@@ -113,7 +113,7 @@ func AdminResetPassword(req *http.Request, cfg *config.ClientAPI, device *api.De
 	}, accAvailableResp); err != nil {
 		return util.JSONResponse{
 			Code: http.StatusInternalServerError,
-			JSON: spec.InternalServerError(),
+			JSON: spec.InternalServerError{},
 		}
 	}
 	if accAvailableResp.Available {
@@ -169,7 +169,10 @@ func AdminReindex(req *http.Request, cfg *config.ClientAPI, device *api.Device,
 	_, err := natsClient.RequestMsg(nats.NewMsg(cfg.Matrix.JetStream.Prefixed(jetstream.InputFulltextReindex)), time.Second*10)
 	if err != nil {
 		logrus.WithError(err).Error("failed to publish nats message")
-		return spec.InternalServerError()
+		return util.JSONResponse{
+			Code: http.StatusInternalServerError,
+			JSON: spec.InternalServerError{},
+		}
 	}
 	return util.JSONResponse{
 		Code: http.StatusOK,
@@ -231,10 +234,10 @@ func AdminDownloadState(req *http.Request, device *api.Device, rsAPI roomserverA
 		}
 	}
 	if err = rsAPI.PerformAdminDownloadState(req.Context(), roomID, device.UserID, spec.ServerName(serverName)); err != nil {
-		if errors.Is(err, eventutil.ErrRoomNoExists) {
+		if errors.Is(err, eventutil.ErrRoomNoExists{}) {
 			return util.JSONResponse{
 				Code: 200,
-				JSON: spec.NotFound(eventutil.ErrRoomNoExists.Error()),
+				JSON: spec.NotFound(err.Error()),
 			}
 		}
 		logrus.WithError(err).WithFields(logrus.Fields{
diff --git a/clientapi/routing/admin_whois.go b/clientapi/routing/admin_whois.go
index cb2b8a26..7d753656 100644
--- a/clientapi/routing/admin_whois.go
+++ b/clientapi/routing/admin_whois.go
@@ -61,7 +61,10 @@ func GetAdminWhois(
 	}, &queryRes)
 	if err != nil {
 		util.GetLogger(req.Context()).WithError(err).Error("GetAdminWhois failed to query user devices")
-		return spec.InternalServerError()
+		return util.JSONResponse{
+			Code: http.StatusInternalServerError,
+			JSON: spec.InternalServerError{},
+		}
 	}
 
 	devices := make(map[string]deviceInfo)
diff --git a/clientapi/routing/aliases.go b/clientapi/routing/aliases.go
index 87c1f9ff..f6603be8 100644
--- a/clientapi/routing/aliases.go
+++ b/clientapi/routing/aliases.go
@@ -62,7 +62,10 @@ func GetAliases(
 		var queryRes api.QueryMembershipForUserResponse
 		if err := rsAPI.QueryMembershipForUser(req.Context(), &queryReq, &queryRes); err != nil {
 			util.GetLogger(req.Context()).WithError(err).Error("rsAPI.QueryMembershipsForRoom failed")
-			return spec.InternalServerError()
+			return util.JSONResponse{
+				Code: http.StatusInternalServerError,
+				JSON: spec.InternalServerError{},
+			}
 		}
 		if !queryRes.IsInRoom {
 			return util.JSONResponse{
diff --git a/clientapi/routing/createroom.go b/clientapi/routing/createroom.go
index f0cdd6f5..bc960006 100644
--- a/clientapi/routing/createroom.go
+++ b/clientapi/routing/createroom.go
@@ -174,7 +174,10 @@ func createRoom(
 	_, userDomain, err := gomatrixserverlib.SplitID('@', device.UserID)
 	if err != nil {
 		util.GetLogger(ctx).WithError(err).Error("gomatrixserverlib.SplitID failed")
-		return spec.InternalServerError()
+		return util.JSONResponse{
+			Code: http.StatusInternalServerError,
+			JSON: spec.InternalServerError{},
+		}
 	}
 	if !cfg.Matrix.IsLocalServerName(userDomain) {
 		return util.JSONResponse{
@@ -218,7 +221,10 @@ func createRoom(
 	profile, err := appserviceAPI.RetrieveUserProfile(ctx, userID, asAPI, profileAPI)
 	if err != nil {
 		util.GetLogger(ctx).WithError(err).Error("appserviceAPI.RetrieveUserProfile failed")
-		return spec.InternalServerError()
+		return util.JSONResponse{
+			Code: http.StatusInternalServerError,
+			JSON: spec.InternalServerError{},
+		}
 	}
 
 	createContent := map[string]interface{}{}
@@ -342,7 +348,10 @@ func createRoom(
 		err = rsAPI.GetRoomIDForAlias(ctx, &hasAliasReq, &aliasResp)
 		if err != nil {
 			util.GetLogger(ctx).WithError(err).Error("aliasAPI.GetRoomIDForAlias failed")
-			return spec.InternalServerError()
+			return util.JSONResponse{
+				Code: http.StatusInternalServerError,
+				JSON: spec.InternalServerError{},
+			}
 		}
 		if aliasResp.RoomID != "" {
 			return util.JSONResponse{
@@ -455,7 +464,10 @@ func createRoom(
 		err = builder.SetContent(e.Content)
 		if err != nil {
 			util.GetLogger(ctx).WithError(err).Error("builder.SetContent failed")
-			return spec.InternalServerError()
+			return util.JSONResponse{
+				Code: http.StatusInternalServerError,
+				JSON: spec.InternalServerError{},
+			}
 		}
 		if i > 0 {
 			builder.PrevEvents = []gomatrixserverlib.EventReference{builtEvents[i-1].EventReference()}
@@ -463,17 +475,26 @@ func createRoom(
 		var ev gomatrixserverlib.PDU
 		if err = builder.AddAuthEvents(&authEvents); err != nil {
 			util.GetLogger(ctx).WithError(err).Error("AddAuthEvents failed")
-			return spec.InternalServerError()
+			return util.JSONResponse{
+				Code: http.StatusInternalServerError,
+				JSON: spec.InternalServerError{},
+			}
 		}
 		ev, err = builder.Build(evTime, userDomain, cfg.Matrix.KeyID, cfg.Matrix.PrivateKey)
 		if err != nil {
 			util.GetLogger(ctx).WithError(err).Error("buildEvent failed")
-			return spec.InternalServerError()
+			return util.JSONResponse{
+				Code: http.StatusInternalServerError,
+				JSON: spec.InternalServerError{},
+			}
 		}
 
 		if err = gomatrixserverlib.Allowed(ev, &authEvents); err != nil {
 			util.GetLogger(ctx).WithError(err).Error("gomatrixserverlib.Allowed failed")
-			return spec.InternalServerError()
+			return util.JSONResponse{
+				Code: http.StatusInternalServerError,
+				JSON: spec.InternalServerError{},
+			}
 		}
 
 		// Add the event to the list of auth events
@@ -481,7 +502,10 @@ func createRoom(
 		err = authEvents.AddEvent(ev)
 		if err != nil {
 			util.GetLogger(ctx).WithError(err).Error("authEvents.AddEvent failed")
-			return spec.InternalServerError()
+			return util.JSONResponse{
+				Code: http.StatusInternalServerError,
+				JSON: spec.InternalServerError{},
+			}
 		}
 	}
 
@@ -496,7 +520,10 @@ func createRoom(
 	}
 	if err = roomserverAPI.SendInputRoomEvents(ctx, rsAPI, device.UserDomain(), inputs, false); err != nil {
 		util.GetLogger(ctx).WithError(err).Error("roomserverAPI.SendInputRoomEvents failed")
-		return spec.InternalServerError()
+		return util.JSONResponse{
+			Code: http.StatusInternalServerError,
+			JSON: spec.InternalServerError{},
+		}
 	}
 
 	// TODO(#269): Reserve room alias while we create the room. This stops us
@@ -513,7 +540,10 @@ func createRoom(
 		err = rsAPI.SetRoomAlias(ctx, &aliasReq, &aliasResp)
 		if err != nil {
 			util.GetLogger(ctx).WithError(err).Error("aliasAPI.SetRoomAlias failed")
-			return spec.InternalServerError()
+			return util.JSONResponse{
+				Code: http.StatusInternalServerError,
+				JSON: spec.InternalServerError{},
+			}
 		}
 
 		if aliasResp.AliasExists {
@@ -596,7 +626,7 @@ func createRoom(
 				sentry.CaptureException(err)
 				return util.JSONResponse{
 					Code: http.StatusInternalServerError,
-					JSON: spec.InternalServerError(),
+					JSON: spec.InternalServerError{},
 				}
 			}
 		}
@@ -609,7 +639,10 @@ func createRoom(
 			Visibility: spec.Public,
 		}); err != nil {
 			util.GetLogger(ctx).WithError(err).Error("failed to publish room")
-			return spec.InternalServerError()
+			return util.JSONResponse{
+				Code: http.StatusInternalServerError,
+				JSON: spec.InternalServerError{},
+			}
 		}
 	}
 
diff --git a/clientapi/routing/deactivate.go b/clientapi/routing/deactivate.go
index 78cf9fe3..c151c130 100644
--- a/clientapi/routing/deactivate.go
+++ b/clientapi/routing/deactivate.go
@@ -36,7 +36,10 @@ func Deactivate(
 	localpart, serverName, err := gomatrixserverlib.SplitID('@', login.Username())
 	if err != nil {
 		util.GetLogger(req.Context()).WithError(err).Error("gomatrixserverlib.SplitID failed")
-		return spec.InternalServerError()
+		return util.JSONResponse{
+			Code: http.StatusInternalServerError,
+			JSON: spec.InternalServerError{},
+		}
 	}
 
 	var res api.PerformAccountDeactivationResponse
@@ -46,7 +49,10 @@ func Deactivate(
 	}, &res)
 	if err != nil {
 		util.GetLogger(ctx).WithError(err).Error("userAPI.PerformAccountDeactivation failed")
-		return spec.InternalServerError()
+		return util.JSONResponse{
+			Code: http.StatusInternalServerError,
+			JSON: spec.InternalServerError{},
+		}
 	}
 
 	return util.JSONResponse{
diff --git a/clientapi/routing/device.go b/clientapi/routing/device.go
index 6209d8e9..6f2de353 100644
--- a/clientapi/routing/device.go
+++ b/clientapi/routing/device.go
@@ -60,7 +60,10 @@ func GetDeviceByID(
 	}, &queryRes)
 	if err != nil {
 		util.GetLogger(req.Context()).WithError(err).Error("QueryDevices failed")
-		return spec.InternalServerError()
+		return util.JSONResponse{
+			Code: http.StatusInternalServerError,
+			JSON: spec.InternalServerError{},
+		}
 	}
 	var targetDevice *api.Device
 	for _, device := range queryRes.Devices {
@@ -97,7 +100,10 @@ func GetDevicesByLocalpart(
 	}, &queryRes)
 	if err != nil {
 		util.GetLogger(req.Context()).WithError(err).Error("QueryDevices failed")
-		return spec.InternalServerError()
+		return util.JSONResponse{
+			Code: http.StatusInternalServerError,
+			JSON: spec.InternalServerError{},
+		}
 	}
 
 	res := devicesJSON{}
@@ -139,7 +145,10 @@ func UpdateDeviceByID(
 	}, &performRes)
 	if err != nil {
 		util.GetLogger(req.Context()).WithError(err).Error("PerformDeviceUpdate failed")
-		return spec.InternalServerError()
+		return util.JSONResponse{
+			Code: http.StatusInternalServerError,
+			JSON: spec.InternalServerError{},
+		}
 	}
 	if !performRes.DeviceExists {
 		return util.JSONResponse{
@@ -206,7 +215,10 @@ func DeleteDeviceById(
 	localpart, _, err := gomatrixserverlib.SplitID('@', device.UserID)
 	if err != nil {
 		util.GetLogger(ctx).WithError(err).Error("gomatrixserverlib.SplitID failed")
-		return spec.InternalServerError()
+		return util.JSONResponse{
+			Code: http.StatusInternalServerError,
+			JSON: spec.InternalServerError{},
+		}
 	}
 
 	// make sure that the access token being used matches the login creds used for user interactive auth, else
@@ -224,7 +236,10 @@ func DeleteDeviceById(
 		DeviceIDs: []string{deviceID},
 	}, &res); err != nil {
 		util.GetLogger(ctx).WithError(err).Error("userAPI.PerformDeviceDeletion failed")
-		return spec.InternalServerError()
+		return util.JSONResponse{
+			Code: http.StatusInternalServerError,
+			JSON: spec.InternalServerError{},
+		}
 	}
 
 	deleteOK = true
@@ -266,7 +281,10 @@ func DeleteDevices(
 	payload := devicesDeleteJSON{}
 	if err = json.Unmarshal(bodyBytes, &payload); err != nil {
 		util.GetLogger(ctx).WithError(err).Error("unable to unmarshal device deletion request")
-		return spec.InternalServerError()
+		return util.JSONResponse{
+			Code: http.StatusInternalServerError,
+			JSON: spec.InternalServerError{},
+		}
 	}
 
 	var res api.PerformDeviceDeletionResponse
@@ -275,7 +293,10 @@ func DeleteDevices(
 		DeviceIDs: payload.Devices,
 	}, &res); err != nil {
 		util.GetLogger(ctx).WithError(err).Error("userAPI.PerformDeviceDeletion failed")
-		return spec.InternalServerError()
+		return util.JSONResponse{
+			Code: http.StatusInternalServerError,
+			JSON: spec.InternalServerError{},
+		}
 	}
 
 	return util.JSONResponse{
diff --git a/clientapi/routing/directory.go b/clientapi/routing/directory.go
index 0ca9475d..c786f8cc 100644
--- a/clientapi/routing/directory.go
+++ b/clientapi/routing/directory.go
@@ -69,7 +69,10 @@ func DirectoryRoom(
 	queryRes := &roomserverAPI.GetRoomIDForAliasResponse{}
 	if err = rsAPI.GetRoomIDForAlias(req.Context(), queryReq, queryRes); err != nil {
 		util.GetLogger(req.Context()).WithError(err).Error("rsAPI.GetRoomIDForAlias failed")
-		return spec.InternalServerError()
+		return util.JSONResponse{
+			Code: http.StatusInternalServerError,
+			JSON: spec.InternalServerError{},
+		}
 	}
 
 	res.RoomID = queryRes.RoomID
@@ -83,7 +86,10 @@ func DirectoryRoom(
 				// TODO: Return 502 if the remote server errored.
 				// TODO: Return 504 if the remote server timed out.
 				util.GetLogger(req.Context()).WithError(fedErr).Error("federation.LookupRoomAlias failed")
-				return spec.InternalServerError()
+				return util.JSONResponse{
+					Code: http.StatusInternalServerError,
+					JSON: spec.InternalServerError{},
+				}
 			}
 			res.RoomID = fedRes.RoomID
 			res.fillServers(fedRes.Servers)
@@ -102,7 +108,10 @@ func DirectoryRoom(
 		var joinedHostsRes federationAPI.QueryJoinedHostServerNamesInRoomResponse
 		if err = fedSenderAPI.QueryJoinedHostServerNamesInRoom(req.Context(), &joinedHostsReq, &joinedHostsRes); err != nil {
 			util.GetLogger(req.Context()).WithError(err).Error("fedSenderAPI.QueryJoinedHostServerNamesInRoom failed")
-			return spec.InternalServerError()
+			return util.JSONResponse{
+				Code: http.StatusInternalServerError,
+				JSON: spec.InternalServerError{},
+			}
 		}
 		res.fillServers(joinedHostsRes.ServerNames)
 	}
@@ -180,7 +189,10 @@ func SetLocalAlias(
 	var queryRes roomserverAPI.SetRoomAliasResponse
 	if err := rsAPI.SetRoomAlias(req.Context(), &queryReq, &queryRes); err != nil {
 		util.GetLogger(req.Context()).WithError(err).Error("aliasAPI.SetRoomAlias failed")
-		return spec.InternalServerError()
+		return util.JSONResponse{
+			Code: http.StatusInternalServerError,
+			JSON: spec.InternalServerError{},
+		}
 	}
 
 	if queryRes.AliasExists {
@@ -210,7 +222,10 @@ func RemoveLocalAlias(
 	var queryRes roomserverAPI.RemoveRoomAliasResponse
 	if err := rsAPI.RemoveRoomAlias(req.Context(), &queryReq, &queryRes); err != nil {
 		util.GetLogger(req.Context()).WithError(err).Error("aliasAPI.RemoveRoomAlias failed")
-		return spec.InternalServerError()
+		return util.JSONResponse{
+			Code: http.StatusInternalServerError,
+			JSON: spec.InternalServerError{},
+		}
 	}
 
 	if !queryRes.Found {
@@ -248,7 +263,10 @@ func GetVisibility(
 	}, &res)
 	if err != nil {
 		util.GetLogger(req.Context()).WithError(err).Error("QueryPublishedRooms failed")
-		return spec.InternalServerError()
+		return util.JSONResponse{
+			Code: http.StatusInternalServerError,
+			JSON: spec.InternalServerError{},
+		}
 	}
 
 	var v roomVisibility
@@ -286,7 +304,10 @@ func SetVisibility(
 	err := rsAPI.QueryLatestEventsAndState(req.Context(), &queryEventsReq, &queryEventsRes)
 	if err != nil || len(queryEventsRes.StateEvents) == 0 {
 		util.GetLogger(req.Context()).WithError(err).Error("could not query events from room")
-		return spec.InternalServerError()
+		return util.JSONResponse{
+			Code: http.StatusInternalServerError,
+			JSON: spec.InternalServerError{},
+		}
 	}
 
 	// NOTSPEC: Check if the user's power is greater than power required to change m.room.canonical_alias event
@@ -308,7 +329,10 @@ func SetVisibility(
 		Visibility: v.Visibility,
 	}); err != nil {
 		util.GetLogger(req.Context()).WithError(err).Error("failed to publish room")
-		return spec.InternalServerError()
+		return util.JSONResponse{
+			Code: http.StatusInternalServerError,
+			JSON: spec.InternalServerError{},
+		}
 	}
 
 	return util.JSONResponse{
@@ -344,7 +368,10 @@ func SetVisibilityAS(
 		AppserviceID: dev.AppserviceID,
 	}); err != nil {
 		util.GetLogger(req.Context()).WithError(err).Error("failed to publish room")
-		return spec.InternalServerError()
+		return util.JSONResponse{
+			Code: http.StatusInternalServerError,
+			JSON: spec.InternalServerError{},
+		}
 	}
 
 	return util.JSONResponse{
diff --git a/clientapi/routing/directory_public.go b/clientapi/routing/directory_public.go
index 9718ccab..67146630 100644
--- a/clientapi/routing/directory_public.go
+++ b/clientapi/routing/directory_public.go
@@ -81,7 +81,10 @@ func GetPostPublicRooms(
 		)
 		if err != nil {
 			util.GetLogger(req.Context()).WithError(err).Error("failed to get public rooms")
-			return spec.InternalServerError()
+			return util.JSONResponse{
+				Code: http.StatusInternalServerError,
+				JSON: spec.InternalServerError{},
+			}
 		}
 		return util.JSONResponse{
 			Code: http.StatusOK,
@@ -92,7 +95,10 @@ func GetPostPublicRooms(
 	response, err := publicRooms(req.Context(), request, rsAPI, extRoomsProvider)
 	if err != nil {
 		util.GetLogger(req.Context()).WithError(err).Errorf("failed to work out public rooms")
-		return spec.InternalServerError()
+		return util.JSONResponse{
+			Code: http.StatusInternalServerError,
+			JSON: spec.InternalServerError{},
+		}
 	}
 	return util.JSONResponse{
 		Code: http.StatusOK,
diff --git a/clientapi/routing/joined_rooms.go b/clientapi/routing/joined_rooms.go
index 51a96e4d..f664183f 100644
--- a/clientapi/routing/joined_rooms.go
+++ b/clientapi/routing/joined_rooms.go
@@ -40,7 +40,10 @@ func GetJoinedRooms(
 	}, &res)
 	if err != nil {
 		util.GetLogger(req.Context()).WithError(err).Error("QueryRoomsForUser failed")
-		return spec.InternalServerError()
+		return util.JSONResponse{
+			Code: http.StatusInternalServerError,
+			JSON: spec.InternalServerError{},
+		}
 	}
 	if res.RoomIDs == nil {
 		res.RoomIDs = []string{}
diff --git a/clientapi/routing/joinroom.go b/clientapi/routing/joinroom.go
index a67d5132..43331b42 100644
--- a/clientapi/routing/joinroom.go
+++ b/clientapi/routing/joinroom.go
@@ -16,7 +16,6 @@ package routing
 
 import (
 	"encoding/json"
-	"errors"
 	"net/http"
 	"time"
 
@@ -114,16 +113,15 @@ func JoinRoomByIDOrAlias(
 				Code: e.Code,
 				JSON: json.RawMessage(e.Message),
 			}
+		case eventutil.ErrRoomNoExists:
+			response = util.JSONResponse{
+				Code: http.StatusNotFound,
+				JSON: spec.NotFound(e.Error()),
+			}
 		default:
 			response = util.JSONResponse{
 				Code: http.StatusInternalServerError,
-				JSON: spec.InternalServerError(),
-			}
-			if errors.Is(err, eventutil.ErrRoomNoExists) {
-				response = util.JSONResponse{
-					Code: http.StatusNotFound,
-					JSON: spec.NotFound(e.Error()),
-				}
+				JSON: spec.InternalServerError{},
 			}
 		}
 		done <- response
diff --git a/clientapi/routing/key_backup.go b/clientapi/routing/key_backup.go
index b7b1cadd..7f8bd9f4 100644
--- a/clientapi/routing/key_backup.go
+++ b/clientapi/routing/key_backup.go
@@ -128,7 +128,7 @@ func ModifyKeyBackupVersionAuthData(req *http.Request, userAPI userapi.ClientUse
 		Algorithm: kb.Algorithm,
 	})
 	switch e := err.(type) {
-	case *spec.ErrRoomKeysVersion:
+	case spec.ErrRoomKeysVersion:
 		return util.JSONResponse{
 			Code: http.StatusForbidden,
 			JSON: e,
@@ -182,7 +182,7 @@ func UploadBackupKeys(
 	})
 
 	switch e := err.(type) {
-	case *spec.ErrRoomKeysVersion:
+	case spec.ErrRoomKeysVersion:
 		return util.JSONResponse{
 			Code: http.StatusForbidden,
 			JSON: e,
diff --git a/clientapi/routing/keys.go b/clientapi/routing/keys.go
index 363ae3dc..72785cda 100644
--- a/clientapi/routing/keys.go
+++ b/clientapi/routing/keys.go
@@ -67,7 +67,10 @@ func UploadKeys(req *http.Request, keyAPI api.ClientKeyAPI, device *api.Device)
 	}
 	if uploadRes.Error != nil {
 		util.GetLogger(req.Context()).WithError(uploadRes.Error).Error("Failed to PerformUploadKeys")
-		return spec.InternalServerError()
+		return util.JSONResponse{
+			Code: http.StatusInternalServerError,
+			JSON: spec.InternalServerError{},
+		}
 	}
 	if len(uploadRes.KeyErrors) > 0 {
 		util.GetLogger(req.Context()).WithField("key_errors", uploadRes.KeyErrors).Error("Failed to upload one or more keys")
@@ -156,7 +159,10 @@ func ClaimKeys(req *http.Request, keyAPI api.ClientKeyAPI) util.JSONResponse {
 	}, &claimRes)
 	if claimRes.Error != nil {
 		util.GetLogger(req.Context()).WithError(claimRes.Error).Error("failed to PerformClaimKeys")
-		return spec.InternalServerError()
+		return util.JSONResponse{
+			Code: http.StatusInternalServerError,
+			JSON: spec.InternalServerError{},
+		}
 	}
 	return util.JSONResponse{
 		Code: 200,
diff --git a/clientapi/routing/login.go b/clientapi/routing/login.go
index d326bff7..bc38b834 100644
--- a/clientapi/routing/login.go
+++ b/clientapi/routing/login.go
@@ -83,13 +83,19 @@ func completeAuth(
 	token, err := auth.GenerateAccessToken()
 	if err != nil {
 		util.GetLogger(ctx).WithError(err).Error("auth.GenerateAccessToken failed")
-		return spec.InternalServerError()
+		return util.JSONResponse{
+			Code: http.StatusInternalServerError,
+			JSON: spec.InternalServerError{},
+		}
 	}
 
 	localpart, serverName, err := userutil.ParseUsernameParam(login.Username(), cfg)
 	if err != nil {
 		util.GetLogger(ctx).WithError(err).Error("auth.ParseUsernameParam failed")
-		return spec.InternalServerError()
+		return util.JSONResponse{
+			Code: http.StatusInternalServerError,
+			JSON: spec.InternalServerError{},
+		}
 	}
 
 	var performRes userapi.PerformDeviceCreationResponse
diff --git a/clientapi/routing/logout.go b/clientapi/routing/logout.go
index 049c88d5..d06bac78 100644
--- a/clientapi/routing/logout.go
+++ b/clientapi/routing/logout.go
@@ -33,7 +33,10 @@ func Logout(
 	}, &performRes)
 	if err != nil {
 		util.GetLogger(req.Context()).WithError(err).Error("PerformDeviceDeletion failed")
-		return spec.InternalServerError()
+		return util.JSONResponse{
+			Code: http.StatusInternalServerError,
+			JSON: spec.InternalServerError{},
+		}
 	}
 
 	return util.JSONResponse{
@@ -53,7 +56,10 @@ func LogoutAll(
 	}, &performRes)
 	if err != nil {
 		util.GetLogger(req.Context()).WithError(err).Error("PerformDeviceDeletion failed")
-		return spec.InternalServerError()
+		return util.JSONResponse{
+			Code: http.StatusInternalServerError,
+			JSON: spec.InternalServerError{},
+		}
 	}
 
 	return util.JSONResponse{
diff --git a/clientapi/routing/membership.go b/clientapi/routing/membership.go
index 9b95ba5d..4f2a0e39 100644
--- a/clientapi/routing/membership.go
+++ b/clientapi/routing/membership.go
@@ -85,7 +85,10 @@ func sendMembership(ctx context.Context, profileAPI userapi.ClientUserAPI, devic
 	)
 	if err != nil {
 		util.GetLogger(ctx).WithError(err).Error("buildMembershipEvent failed")
-		return spec.InternalServerError()
+		return util.JSONResponse{
+			Code: http.StatusInternalServerError,
+			JSON: spec.InternalServerError{},
+		}
 	}
 
 	serverName := device.UserDomain()
@@ -100,7 +103,10 @@ func sendMembership(ctx context.Context, profileAPI userapi.ClientUserAPI, devic
 		false,
 	); err != nil {
 		util.GetLogger(ctx).WithError(err).Error("SendEvents failed")
-		return spec.InternalServerError()
+		return util.JSONResponse{
+			Code: http.StatusInternalServerError,
+			JSON: spec.InternalServerError{},
+		}
 	}
 
 	return util.JSONResponse{
@@ -262,7 +268,10 @@ func sendInvite(
 	)
 	if err != nil {
 		util.GetLogger(ctx).WithError(err).Error("buildMembershipEvent failed")
-		return spec.InternalServerError(), err
+		return util.JSONResponse{
+			Code: http.StatusInternalServerError,
+			JSON: spec.InternalServerError{},
+		}, err
 	}
 
 	err = rsAPI.PerformInvite(ctx, &api.PerformInviteRequest{
@@ -289,7 +298,7 @@ func sendInvite(
 		sentry.CaptureException(err)
 		return util.JSONResponse{
 			Code: http.StatusInternalServerError,
-			JSON: spec.InternalServerError(),
+			JSON: spec.InternalServerError{},
 		}, err
 	}
 
@@ -398,31 +407,38 @@ func checkAndProcessThreepid(
 		req.Context(), device, body, cfg, rsAPI, profileAPI,
 		roomID, evTime,
 	)
-	if err == threepid.ErrMissingParameter {
+	switch e := err.(type) {
+	case nil:
+	case threepid.ErrMissingParameter:
+		util.GetLogger(req.Context()).WithError(err).Error("threepid.CheckAndProcessInvite failed")
 		return inviteStored, &util.JSONResponse{
 			Code: http.StatusBadRequest,
 			JSON: spec.BadJSON(err.Error()),
 		}
-	} else if err == threepid.ErrNotTrusted {
+	case threepid.ErrNotTrusted:
+		util.GetLogger(req.Context()).WithError(err).Error("threepid.CheckAndProcessInvite failed")
 		return inviteStored, &util.JSONResponse{
 			Code: http.StatusBadRequest,
 			JSON: spec.NotTrusted(body.IDServer),
 		}
-	} else if err == eventutil.ErrRoomNoExists {
+	case eventutil.ErrRoomNoExists:
+		util.GetLogger(req.Context()).WithError(err).Error("threepid.CheckAndProcessInvite failed")
 		return inviteStored, &util.JSONResponse{
 			Code: http.StatusNotFound,
 			JSON: spec.NotFound(err.Error()),
 		}
-	} else if e, ok := err.(gomatrixserverlib.BadJSONError); ok {
+	case gomatrixserverlib.BadJSONError:
+		util.GetLogger(req.Context()).WithError(err).Error("threepid.CheckAndProcessInvite failed")
 		return inviteStored, &util.JSONResponse{
 			Code: http.StatusBadRequest,
 			JSON: spec.BadJSON(e.Error()),
 		}
-	}
-	if err != nil {
+	default:
 		util.GetLogger(req.Context()).WithError(err).Error("threepid.CheckAndProcessInvite failed")
-		er := spec.InternalServerError()
-		return inviteStored, &er
+		return inviteStored, &util.JSONResponse{
+			Code: http.StatusInternalServerError,
+			JSON: spec.InternalServerError{},
+		}
 	}
 	return
 }
@@ -435,8 +451,10 @@ func checkMemberInRoom(ctx context.Context, rsAPI roomserverAPI.ClientRoomserver
 	}, &membershipRes)
 	if err != nil {
 		util.GetLogger(ctx).WithError(err).Error("QueryMembershipForUser: could not query membership for user")
-		e := spec.InternalServerError()
-		return &e
+		return &util.JSONResponse{
+			Code: http.StatusInternalServerError,
+			JSON: spec.InternalServerError{},
+		}
 	}
 	if !membershipRes.IsInRoom {
 		return &util.JSONResponse{
@@ -461,7 +479,10 @@ func SendForget(
 	err := rsAPI.QueryMembershipForUser(ctx, &membershipReq, &membershipRes)
 	if err != nil {
 		logger.WithError(err).Error("QueryMembershipForUser: could not query membership for user")
-		return spec.InternalServerError()
+		return util.JSONResponse{
+			Code: http.StatusInternalServerError,
+			JSON: spec.InternalServerError{},
+		}
 	}
 	if !membershipRes.RoomExists {
 		return util.JSONResponse{
@@ -483,7 +504,10 @@ func SendForget(
 	response := roomserverAPI.PerformForgetResponse{}
 	if err := rsAPI.PerformForget(ctx, &request, &response); err != nil {
 		logger.WithError(err).Error("PerformForget: unable to forget room")
-		return spec.InternalServerError()
+		return util.JSONResponse{
+			Code: http.StatusInternalServerError,
+			JSON: spec.InternalServerError{},
+		}
 	}
 	return util.JSONResponse{
 		Code: http.StatusOK,
diff --git a/clientapi/routing/notification.go b/clientapi/routing/notification.go
index 8ac12ce5..4b9043fa 100644
--- a/clientapi/routing/notification.go
+++ b/clientapi/routing/notification.go
@@ -35,7 +35,10 @@ func GetNotifications(
 		limit, err = strconv.ParseInt(limitStr, 10, 64)
 		if err != nil {
 			util.GetLogger(req.Context()).WithError(err).Error("ParseInt(limit) failed")
-			return spec.InternalServerError()
+			return util.JSONResponse{
+				Code: http.StatusInternalServerError,
+				JSON: spec.InternalServerError{},
+			}
 		}
 	}
 
@@ -43,7 +46,10 @@ func GetNotifications(
 	localpart, domain, err := gomatrixserverlib.SplitID('@', device.UserID)
 	if err != nil {
 		util.GetLogger(req.Context()).WithError(err).Error("SplitID failed")
-		return spec.InternalServerError()
+		return util.JSONResponse{
+			Code: http.StatusInternalServerError,
+			JSON: spec.InternalServerError{},
+		}
 	}
 	err = userAPI.QueryNotifications(req.Context(), &userapi.QueryNotificationsRequest{
 		Localpart:  localpart,
@@ -54,7 +60,10 @@ func GetNotifications(
 	}, &queryRes)
 	if err != nil {
 		util.GetLogger(req.Context()).WithError(err).Error("QueryNotifications failed")
-		return spec.InternalServerError()
+		return util.JSONResponse{
+			Code: http.StatusInternalServerError,
+			JSON: spec.InternalServerError{},
+		}
 	}
 	util.GetLogger(req.Context()).WithField("from", req.URL.Query().Get("from")).WithField("limit", limit).WithField("only", req.URL.Query().Get("only")).WithField("next", queryRes.NextToken).Infof("QueryNotifications: len %d", len(queryRes.Notifications))
 	return util.JSONResponse{
diff --git a/clientapi/routing/openid.go b/clientapi/routing/openid.go
index 1ead00eb..8dfba8af 100644
--- a/clientapi/routing/openid.go
+++ b/clientapi/routing/openid.go
@@ -55,7 +55,10 @@ func CreateOpenIDToken(
 	err := userAPI.PerformOpenIDTokenCreation(req.Context(), &request, &response)
 	if err != nil {
 		util.GetLogger(req.Context()).WithError(err).Error("userAPI.CreateOpenIDToken failed")
-		return spec.InternalServerError()
+		return util.JSONResponse{
+			Code: http.StatusInternalServerError,
+			JSON: spec.InternalServerError{},
+		}
 	}
 
 	return util.JSONResponse{
diff --git a/clientapi/routing/password.go b/clientapi/routing/password.go
index 68466a77..24c52b06 100644
--- a/clientapi/routing/password.go
+++ b/clientapi/routing/password.go
@@ -90,7 +90,10 @@ func Password(
 	localpart, domain, err := gomatrixserverlib.SplitID('@', device.UserID)
 	if err != nil {
 		util.GetLogger(req.Context()).WithError(err).Error("gomatrixserverlib.SplitID failed")
-		return spec.InternalServerError()
+		return util.JSONResponse{
+			Code: http.StatusInternalServerError,
+			JSON: spec.InternalServerError{},
+		}
 	}
 
 	// Ask the user API to perform the password change.
@@ -102,11 +105,17 @@ func Password(
 	passwordRes := &api.PerformPasswordUpdateResponse{}
 	if err := userAPI.PerformPasswordUpdate(req.Context(), passwordReq, passwordRes); err != nil {
 		util.GetLogger(req.Context()).WithError(err).Error("PerformPasswordUpdate failed")
-		return spec.InternalServerError()
+		return util.JSONResponse{
+			Code: http.StatusInternalServerError,
+			JSON: spec.InternalServerError{},
+		}
 	}
 	if !passwordRes.PasswordUpdated {
 		util.GetLogger(req.Context()).Error("Expected password to have been updated but wasn't")
-		return spec.InternalServerError()
+		return util.JSONResponse{
+			Code: http.StatusInternalServerError,
+			JSON: spec.InternalServerError{},
+		}
 	}
 
 	// If the request asks us to log out all other devices then
@@ -120,7 +129,10 @@ func Password(
 		logoutRes := &api.PerformDeviceDeletionResponse{}
 		if err := userAPI.PerformDeviceDeletion(req.Context(), logoutReq, logoutRes); err != nil {
 			util.GetLogger(req.Context()).WithError(err).Error("PerformDeviceDeletion failed")
-			return spec.InternalServerError()
+			return util.JSONResponse{
+				Code: http.StatusInternalServerError,
+				JSON: spec.InternalServerError{},
+			}
 		}
 
 		pushersReq := &api.PerformPusherDeletionRequest{
@@ -130,7 +142,10 @@ func Password(
 		}
 		if err := userAPI.PerformPusherDeletion(req.Context(), pushersReq, &struct{}{}); err != nil {
 			util.GetLogger(req.Context()).WithError(err).Error("PerformPusherDeletion failed")
-			return spec.InternalServerError()
+			return util.JSONResponse{
+				Code: http.StatusInternalServerError,
+				JSON: spec.InternalServerError{},
+			}
 		}
 	}
 
diff --git a/clientapi/routing/peekroom.go b/clientapi/routing/peekroom.go
index af486f6d..772dc847 100644
--- a/clientapi/routing/peekroom.go
+++ b/clientapi/routing/peekroom.go
@@ -75,7 +75,10 @@ func PeekRoomByIDOrAlias(
 	case nil:
 	default:
 		logrus.WithError(err).WithField("roomID", roomIDOrAlias).Errorf("Failed to peek room")
-		return spec.InternalServerError()
+		return util.JSONResponse{
+			Code: http.StatusInternalServerError,
+			JSON: spec.InternalServerError{},
+		}
 	}
 
 	// if this user is already joined to the room, we let them peek anyway
@@ -111,7 +114,10 @@ func UnpeekRoomByID(
 	case nil:
 	default:
 		logrus.WithError(err).WithField("roomID", roomID).Errorf("Failed to un-peek room")
-		return spec.InternalServerError()
+		return util.JSONResponse{
+			Code: http.StatusInternalServerError,
+			JSON: spec.InternalServerError{},
+		}
 	}
 
 	return util.JSONResponse{
diff --git a/clientapi/routing/presence.go b/clientapi/routing/presence.go
index d915f060..5aa6d8dd 100644
--- a/clientapi/routing/presence.go
+++ b/clientapi/routing/presence.go
@@ -74,7 +74,7 @@ func SetPresence(
 		log.WithError(err).Errorf("failed to update presence")
 		return util.JSONResponse{
 			Code: http.StatusInternalServerError,
-			JSON: spec.InternalServerError(),
+			JSON: spec.InternalServerError{},
 		}
 	}
 
@@ -99,7 +99,7 @@ func GetPresence(
 		log.WithError(err).Errorf("unable to get presence")
 		return util.JSONResponse{
 			Code: http.StatusInternalServerError,
-			JSON: spec.InternalServerError(),
+			JSON: spec.InternalServerError{},
 		}
 	}
 
@@ -118,7 +118,7 @@ func GetPresence(
 	if err != nil {
 		return util.JSONResponse{
 			Code: http.StatusInternalServerError,
-			JSON: spec.InternalServerError(),
+			JSON: spec.InternalServerError{},
 		}
 	}
 
diff --git a/clientapi/routing/profile.go b/clientapi/routing/profile.go
index 8e88e7c8..76129f0a 100644
--- a/clientapi/routing/profile.go
+++ b/clientapi/routing/profile.go
@@ -52,7 +52,10 @@ func GetProfile(
 		}
 
 		util.GetLogger(req.Context()).WithError(err).Error("getProfile failed")
-		return spec.InternalServerError()
+		return util.JSONResponse{
+			Code: http.StatusInternalServerError,
+			JSON: spec.InternalServerError{},
+		}
 	}
 
 	return util.JSONResponse{
@@ -111,7 +114,10 @@ func SetAvatarURL(
 	localpart, domain, err := gomatrixserverlib.SplitID('@', userID)
 	if err != nil {
 		util.GetLogger(req.Context()).WithError(err).Error("gomatrixserverlib.SplitID failed")
-		return spec.InternalServerError()
+		return util.JSONResponse{
+			Code: http.StatusInternalServerError,
+			JSON: spec.InternalServerError{},
+		}
 	}
 
 	if !cfg.Matrix.IsLocalServerName(domain) {
@@ -132,7 +138,10 @@ func SetAvatarURL(
 	profile, changed, err := profileAPI.SetAvatarURL(req.Context(), localpart, domain, r.AvatarURL)
 	if err != nil {
 		util.GetLogger(req.Context()).WithError(err).Error("profileAPI.SetAvatarURL failed")
-		return spec.InternalServerError()
+		return util.JSONResponse{
+			Code: http.StatusInternalServerError,
+			JSON: spec.InternalServerError{},
+		}
 	}
 	// No need to build new membership events, since nothing changed
 	if !changed {
@@ -200,7 +209,10 @@ func SetDisplayName(
 	localpart, domain, err := gomatrixserverlib.SplitID('@', userID)
 	if err != nil {
 		util.GetLogger(req.Context()).WithError(err).Error("gomatrixserverlib.SplitID failed")
-		return spec.InternalServerError()
+		return util.JSONResponse{
+			Code: http.StatusInternalServerError,
+			JSON: spec.InternalServerError{},
+		}
 	}
 
 	if !cfg.Matrix.IsLocalServerName(domain) {
@@ -221,7 +233,10 @@ func SetDisplayName(
 	profile, changed, err := profileAPI.SetDisplayName(req.Context(), localpart, domain, r.DisplayName)
 	if err != nil {
 		util.GetLogger(req.Context()).WithError(err).Error("profileAPI.SetDisplayName failed")
-		return spec.InternalServerError()
+		return util.JSONResponse{
+			Code: http.StatusInternalServerError,
+			JSON: spec.InternalServerError{},
+		}
 	}
 	// No need to build new membership events, since nothing changed
 	if !changed {
@@ -254,13 +269,19 @@ func updateProfile(
 	}, &res)
 	if err != nil {
 		util.GetLogger(ctx).WithError(err).Error("QueryRoomsForUser failed")
-		return spec.InternalServerError(), err
+		return util.JSONResponse{
+			Code: http.StatusInternalServerError,
+			JSON: spec.InternalServerError{},
+		}, err
 	}
 
 	_, domain, err := gomatrixserverlib.SplitID('@', userID)
 	if err != nil {
 		util.GetLogger(ctx).WithError(err).Error("gomatrixserverlib.SplitID failed")
-		return spec.InternalServerError(), err
+		return util.JSONResponse{
+			Code: http.StatusInternalServerError,
+			JSON: spec.InternalServerError{},
+		}, err
 	}
 
 	events, err := buildMembershipEvents(
@@ -275,12 +296,18 @@ func updateProfile(
 		}, e
 	default:
 		util.GetLogger(ctx).WithError(err).Error("buildMembershipEvents failed")
-		return spec.InternalServerError(), e
+		return util.JSONResponse{
+			Code: http.StatusInternalServerError,
+			JSON: spec.InternalServerError{},
+		}, e
 	}
 
 	if err := api.SendEvents(ctx, rsAPI, api.KindNew, events, device.UserDomain(), domain, domain, nil, true); err != nil {
 		util.GetLogger(ctx).WithError(err).Error("SendEvents failed")
-		return spec.InternalServerError(), err
+		return util.JSONResponse{
+			Code: http.StatusInternalServerError,
+			JSON: spec.InternalServerError{},
+		}, err
 	}
 	return util.JSONResponse{}, nil
 }
diff --git a/clientapi/routing/pusher.go b/clientapi/routing/pusher.go
index 2f51583f..ed59129c 100644
--- a/clientapi/routing/pusher.go
+++ b/clientapi/routing/pusher.go
@@ -34,7 +34,10 @@ func GetPushers(
 	localpart, domain, err := gomatrixserverlib.SplitID('@', device.UserID)
 	if err != nil {
 		util.GetLogger(req.Context()).WithError(err).Error("SplitID failed")
-		return spec.InternalServerError()
+		return util.JSONResponse{
+			Code: http.StatusInternalServerError,
+			JSON: spec.InternalServerError{},
+		}
 	}
 	err = userAPI.QueryPushers(req.Context(), &userapi.QueryPushersRequest{
 		Localpart:  localpart,
@@ -42,7 +45,10 @@ func GetPushers(
 	}, &queryRes)
 	if err != nil {
 		util.GetLogger(req.Context()).WithError(err).Error("QueryPushers failed")
-		return spec.InternalServerError()
+		return util.JSONResponse{
+			Code: http.StatusInternalServerError,
+			JSON: spec.InternalServerError{},
+		}
 	}
 	for i := range queryRes.Pushers {
 		queryRes.Pushers[i].SessionID = 0
@@ -63,7 +69,10 @@ func SetPusher(
 	localpart, domain, err := gomatrixserverlib.SplitID('@', device.UserID)
 	if err != nil {
 		util.GetLogger(req.Context()).WithError(err).Error("SplitID failed")
-		return spec.InternalServerError()
+		return util.JSONResponse{
+			Code: http.StatusInternalServerError,
+			JSON: spec.InternalServerError{},
+		}
 	}
 	body := userapi.PerformPusherSetRequest{}
 	if resErr := httputil.UnmarshalJSONRequest(req, &body); resErr != nil {
@@ -99,7 +108,10 @@ func SetPusher(
 	err = userAPI.PerformPusherSet(req.Context(), &body, &struct{}{})
 	if err != nil {
 		util.GetLogger(req.Context()).WithError(err).Error("PerformPusherSet failed")
-		return spec.InternalServerError()
+		return util.JSONResponse{
+			Code: http.StatusInternalServerError,
+			JSON: spec.InternalServerError{},
+		}
 	}
 
 	return util.JSONResponse{
diff --git a/clientapi/routing/pushrules.go b/clientapi/routing/pushrules.go
index 7be6d2a7..74873d5c 100644
--- a/clientapi/routing/pushrules.go
+++ b/clientapi/routing/pushrules.go
@@ -14,20 +14,23 @@ import (
 )
 
 func errorResponse(ctx context.Context, err error, msg string, args ...interface{}) util.JSONResponse {
-	if eerr, ok := err.(*spec.MatrixError); ok {
+	if eerr, ok := err.(spec.MatrixError); ok {
 		var status int
 		switch eerr.ErrCode {
-		case "M_INVALID_PARAM":
+		case spec.ErrorInvalidParam:
 			status = http.StatusBadRequest
-		case "M_NOT_FOUND":
+		case spec.ErrorNotFound:
 			status = http.StatusNotFound
 		default:
 			status = http.StatusInternalServerError
 		}
-		return util.MatrixErrorResponse(status, eerr.ErrCode, eerr.Err)
+		return util.MatrixErrorResponse(status, string(eerr.ErrCode), eerr.Err)
 	}
 	util.GetLogger(ctx).WithError(err).Errorf(msg, args...)
-	return spec.InternalServerError()
+	return util.JSONResponse{
+		Code: http.StatusInternalServerError,
+		JSON: spec.InternalServerError{},
+	}
 }
 
 func GetAllPushRules(ctx context.Context, device *userapi.Device, userAPI userapi.ClientUserAPI) util.JSONResponse {
diff --git a/clientapi/routing/receipt.go b/clientapi/routing/receipt.go
index 0bbb20b9..be654297 100644
--- a/clientapi/routing/receipt.go
+++ b/clientapi/routing/receipt.go
@@ -48,7 +48,10 @@ func SetReceipt(req *http.Request, userAPI api.ClientUserAPI, syncProducer *prod
 	case "m.fully_read":
 		data, err := json.Marshal(fullyReadEvent{EventID: eventID})
 		if err != nil {
-			return spec.InternalServerError()
+			return util.JSONResponse{
+				Code: http.StatusInternalServerError,
+				JSON: spec.InternalServerError{},
+			}
 		}
 
 		dataReq := api.InputAccountDataRequest{
diff --git a/clientapi/routing/redaction.go b/clientapi/routing/redaction.go
index 12391d26..ed70e5c5 100644
--- a/clientapi/routing/redaction.go
+++ b/clientapi/routing/redaction.go
@@ -16,6 +16,7 @@ package routing
 
 import (
 	"context"
+	"errors"
 	"net/http"
 	"time"
 
@@ -121,17 +122,23 @@ func SendRedaction(
 	err := proto.SetContent(r)
 	if err != nil {
 		util.GetLogger(req.Context()).WithError(err).Error("proto.SetContent failed")
-		return spec.InternalServerError()
+		return util.JSONResponse{
+			Code: http.StatusInternalServerError,
+			JSON: spec.InternalServerError{},
+		}
 	}
 
 	identity, err := cfg.Matrix.SigningIdentityFor(device.UserDomain())
 	if err != nil {
-		return spec.InternalServerError()
+		return util.JSONResponse{
+			Code: http.StatusInternalServerError,
+			JSON: spec.InternalServerError{},
+		}
 	}
 
 	var queryRes roomserverAPI.QueryLatestEventsAndStateResponse
 	e, err := eventutil.QueryAndBuildEvent(req.Context(), &proto, cfg.Matrix, identity, time.Now(), rsAPI, &queryRes)
-	if err == eventutil.ErrRoomNoExists {
+	if errors.Is(err, eventutil.ErrRoomNoExists{}) {
 		return util.JSONResponse{
 			Code: http.StatusNotFound,
 			JSON: spec.NotFound("Room does not exist"),
@@ -140,7 +147,10 @@ func SendRedaction(
 	domain := device.UserDomain()
 	if err = roomserverAPI.SendEvents(context.Background(), rsAPI, roomserverAPI.KindNew, []*types.HeaderedEvent{e}, device.UserDomain(), domain, domain, nil, false); err != nil {
 		util.GetLogger(req.Context()).WithError(err).Errorf("failed to SendEvents")
-		return spec.InternalServerError()
+		return util.JSONResponse{
+			Code: http.StatusInternalServerError,
+			JSON: spec.InternalServerError{},
+		}
 	}
 
 	res := util.JSONResponse{
diff --git a/clientapi/routing/register.go b/clientapi/routing/register.go
index 615ff201..565c4153 100644
--- a/clientapi/routing/register.go
+++ b/clientapi/routing/register.go
@@ -528,7 +528,10 @@ func Register(
 		nres := &userapi.QueryNumericLocalpartResponse{}
 		if err = userAPI.QueryNumericLocalpart(req.Context(), nreq, nres); err != nil {
 			util.GetLogger(req.Context()).WithError(err).Error("userAPI.QueryNumericLocalpart failed")
-			return spec.InternalServerError()
+			return util.JSONResponse{
+				Code: http.StatusInternalServerError,
+				JSON: spec.InternalServerError{},
+			}
 		}
 		r.Username = strconv.FormatInt(nres.ID, 10)
 	}
@@ -713,7 +716,7 @@ func handleRegistrationFlow(
 		case nil:
 		default:
 			util.GetLogger(req.Context()).WithError(err).Error("failed to validate recaptcha")
-			return util.JSONResponse{Code: http.StatusInternalServerError, JSON: spec.InternalServerError()}
+			return util.JSONResponse{Code: http.StatusInternalServerError, JSON: spec.InternalServerError{}}
 		}
 
 		// Add Recaptcha to the list of completed registration stages
diff --git a/clientapi/routing/register_test.go b/clientapi/routing/register_test.go
index 9a60f531..2a88ec38 100644
--- a/clientapi/routing/register_test.go
+++ b/clientapi/routing/register_test.go
@@ -402,7 +402,7 @@ func Test_register(t *testing.T) {
 			enableRecaptcha: true,
 			loginType:       authtypes.LoginTypeRecaptcha,
 			captchaBody:     `i should fail for other reasons`,
-			wantResponse:    util.JSONResponse{Code: http.StatusInternalServerError, JSON: spec.InternalServerError()},
+			wantResponse:    util.JSONResponse{Code: http.StatusInternalServerError, JSON: spec.InternalServerError{}},
 		},
 	}
 
@@ -484,7 +484,7 @@ func Test_register(t *testing.T) {
 					if !reflect.DeepEqual(r.Flows, cfg.Derived.Registration.Flows) {
 						t.Fatalf("unexpected registration flows: %+v, want %+v", r.Flows, cfg.Derived.Registration.Flows)
 					}
-				case *spec.MatrixError:
+				case spec.MatrixError:
 					if !reflect.DeepEqual(tc.wantResponse, resp) {
 						t.Fatalf("(%s), unexpected response: %+v, want: %+v", tc.name, resp, tc.wantResponse)
 					}
@@ -541,7 +541,12 @@ func Test_register(t *testing.T) {
 				resp = Register(req, userAPI, &cfg.ClientAPI)
 
 				switch resp.JSON.(type) {
-				case *spec.MatrixError:
+				case spec.InternalServerError:
+					if !reflect.DeepEqual(tc.wantResponse, resp) {
+						t.Fatalf("unexpected response: %+v, want: %+v", resp, tc.wantResponse)
+					}
+					return
+				case spec.MatrixError:
 					if !reflect.DeepEqual(tc.wantResponse, resp) {
 						t.Fatalf("unexpected response: %+v, want: %+v", resp, tc.wantResponse)
 					}
diff --git a/clientapi/routing/room_tagging.go b/clientapi/routing/room_tagging.go
index 8802d22a..5a5296bf 100644
--- a/clientapi/routing/room_tagging.go
+++ b/clientapi/routing/room_tagging.go
@@ -46,7 +46,10 @@ func GetTags(
 	tagContent, err := obtainSavedTags(req, userID, roomID, userAPI)
 	if err != nil {
 		util.GetLogger(req.Context()).WithError(err).Error("obtainSavedTags failed")
-		return spec.InternalServerError()
+		return util.JSONResponse{
+			Code: http.StatusInternalServerError,
+			JSON: spec.InternalServerError{},
+		}
 	}
 
 	return util.JSONResponse{
@@ -83,7 +86,10 @@ func PutTag(
 	tagContent, err := obtainSavedTags(req, userID, roomID, userAPI)
 	if err != nil {
 		util.GetLogger(req.Context()).WithError(err).Error("obtainSavedTags failed")
-		return spec.InternalServerError()
+		return util.JSONResponse{
+			Code: http.StatusInternalServerError,
+			JSON: spec.InternalServerError{},
+		}
 	}
 
 	if tagContent.Tags == nil {
@@ -93,7 +99,10 @@ func PutTag(
 
 	if err = saveTagData(req, userID, roomID, userAPI, tagContent); err != nil {
 		util.GetLogger(req.Context()).WithError(err).Error("saveTagData failed")
-		return spec.InternalServerError()
+		return util.JSONResponse{
+			Code: http.StatusInternalServerError,
+			JSON: spec.InternalServerError{},
+		}
 	}
 
 	return util.JSONResponse{
@@ -125,7 +134,10 @@ func DeleteTag(
 	tagContent, err := obtainSavedTags(req, userID, roomID, userAPI)
 	if err != nil {
 		util.GetLogger(req.Context()).WithError(err).Error("obtainSavedTags failed")
-		return spec.InternalServerError()
+		return util.JSONResponse{
+			Code: http.StatusInternalServerError,
+			JSON: spec.InternalServerError{},
+		}
 	}
 
 	// Check whether the tag to be deleted exists
@@ -141,7 +153,10 @@ func DeleteTag(
 
 	if err = saveTagData(req, userID, roomID, userAPI, tagContent); err != nil {
 		util.GetLogger(req.Context()).WithError(err).Error("saveTagData failed")
-		return spec.InternalServerError()
+		return util.JSONResponse{
+			Code: http.StatusInternalServerError,
+			JSON: spec.InternalServerError{},
+		}
 	}
 
 	return util.JSONResponse{
diff --git a/clientapi/routing/sendevent.go b/clientapi/routing/sendevent.go
index 2e3cd411..bc14642f 100644
--- a/clientapi/routing/sendevent.go
+++ b/clientapi/routing/sendevent.go
@@ -149,7 +149,10 @@ func SendEvent(
 		}
 		aliasRes := &api.GetAliasesForRoomIDResponse{}
 		if err = rsAPI.GetAliasesForRoomID(req.Context(), &api.GetAliasesForRoomIDRequest{RoomID: roomID}, aliasRes); err != nil {
-			return spec.InternalServerError()
+			return util.JSONResponse{
+				Code: http.StatusInternalServerError,
+				JSON: spec.InternalServerError{},
+			}
 		}
 		var found int
 		requestAliases := append(aliasReq.AltAliases, aliasReq.Alias)
@@ -193,7 +196,10 @@ func SendEvent(
 		false,
 	); err != nil {
 		util.GetLogger(req.Context()).WithError(err).Error("SendEvents failed")
-		return spec.InternalServerError()
+		return util.JSONResponse{
+			Code: http.StatusInternalServerError,
+			JSON: spec.InternalServerError{},
+		}
 	}
 	timeToSubmitEvent := time.Since(startedSubmittingEvent)
 	util.GetLogger(req.Context()).WithFields(logrus.Fields{
@@ -272,43 +278,51 @@ func generateSendEvent(
 	err := proto.SetContent(r)
 	if err != nil {
 		util.GetLogger(ctx).WithError(err).Error("proto.SetContent failed")
-		resErr := spec.InternalServerError()
-		return nil, &resErr
+		return nil, &util.JSONResponse{
+			Code: http.StatusInternalServerError,
+			JSON: spec.InternalServerError{},
+		}
 	}
 
 	identity, err := cfg.Matrix.SigningIdentityFor(device.UserDomain())
 	if err != nil {
-		resErr := spec.InternalServerError()
-		return nil, &resErr
+		return nil, &util.JSONResponse{
+			Code: http.StatusInternalServerError,
+			JSON: spec.InternalServerError{},
+		}
 	}
 
 	var queryRes api.QueryLatestEventsAndStateResponse
 	e, err := eventutil.QueryAndBuildEvent(ctx, &proto, cfg.Matrix, identity, evTime, rsAPI, &queryRes)
-	if err == eventutil.ErrRoomNoExists {
+	switch specificErr := err.(type) {
+	case nil:
+	case eventutil.ErrRoomNoExists:
 		return nil, &util.JSONResponse{
 			Code: http.StatusNotFound,
 			JSON: spec.NotFound("Room does not exist"),
 		}
-	} else if e, ok := err.(gomatrixserverlib.BadJSONError); ok {
+	case gomatrixserverlib.BadJSONError:
 		return nil, &util.JSONResponse{
 			Code: http.StatusBadRequest,
-			JSON: spec.BadJSON(e.Error()),
+			JSON: spec.BadJSON(specificErr.Error()),
 		}
-	} else if e, ok := err.(gomatrixserverlib.EventValidationError); ok {
-		if e.Code == gomatrixserverlib.EventValidationTooLarge {
+	case gomatrixserverlib.EventValidationError:
+		if specificErr.Code == gomatrixserverlib.EventValidationTooLarge {
 			return nil, &util.JSONResponse{
 				Code: http.StatusRequestEntityTooLarge,
-				JSON: spec.BadJSON(e.Error()),
+				JSON: spec.BadJSON(specificErr.Error()),
 			}
 		}
 		return nil, &util.JSONResponse{
 			Code: http.StatusBadRequest,
-			JSON: spec.BadJSON(e.Error()),
+			JSON: spec.BadJSON(specificErr.Error()),
 		}
-	} else if err != nil {
+	default:
 		util.GetLogger(ctx).WithError(err).Error("eventutil.BuildEvent failed")
-		resErr := spec.InternalServerError()
-		return nil, &resErr
+		return nil, &util.JSONResponse{
+			Code: http.StatusInternalServerError,
+			JSON: spec.InternalServerError{},
+		}
 	}
 
 	// check to see if this user can perform this operation
diff --git a/clientapi/routing/sendtodevice.go b/clientapi/routing/sendtodevice.go
index 6d4af072..58d3053e 100644
--- a/clientapi/routing/sendtodevice.go
+++ b/clientapi/routing/sendtodevice.go
@@ -53,7 +53,10 @@ func SendToDevice(
 				req.Context(), device.UserID, userID, deviceID, eventType, message,
 			); err != nil {
 				util.GetLogger(req.Context()).WithError(err).Error("eduProducer.SendToDevice failed")
-				return spec.InternalServerError()
+				return util.JSONResponse{
+					Code: http.StatusInternalServerError,
+					JSON: spec.InternalServerError{},
+				}
 			}
 		}
 	}
diff --git a/clientapi/routing/sendtyping.go b/clientapi/routing/sendtyping.go
index 17532a2d..c5b29297 100644
--- a/clientapi/routing/sendtyping.go
+++ b/clientapi/routing/sendtyping.go
@@ -58,7 +58,10 @@ func SendTyping(
 
 	if err := syncProducer.SendTyping(req.Context(), userID, roomID, r.Typing, r.Timeout); err != nil {
 		util.GetLogger(req.Context()).WithError(err).Error("eduProducer.Send failed")
-		return spec.InternalServerError()
+		return util.JSONResponse{
+			Code: http.StatusInternalServerError,
+			JSON: spec.InternalServerError{},
+		}
 	}
 
 	return util.JSONResponse{
diff --git a/clientapi/routing/server_notices.go b/clientapi/routing/server_notices.go
index a418677e..ad50cc80 100644
--- a/clientapi/routing/server_notices.go
+++ b/clientapi/routing/server_notices.go
@@ -175,7 +175,10 @@ func SendServerNotice(
 			}}
 			if err = saveTagData(req, r.UserID, roomID, userAPI, serverAlertTag); err != nil {
 				util.GetLogger(ctx).WithError(err).Error("saveTagData failed")
-				return spec.InternalServerError()
+				return util.JSONResponse{
+					Code: http.StatusInternalServerError,
+					JSON: spec.InternalServerError{},
+				}
 			}
 
 		default:
@@ -189,7 +192,10 @@ func SendServerNotice(
 		err := rsAPI.QueryMembershipForUser(ctx, &api.QueryMembershipForUserRequest{UserID: r.UserID, RoomID: roomID}, &membershipRes)
 		if err != nil {
 			util.GetLogger(ctx).WithError(err).Error("unable to query membership for user")
-			return spec.InternalServerError()
+			return util.JSONResponse{
+				Code: http.StatusInternalServerError,
+				JSON: spec.InternalServerError{},
+			}
 		}
 		if !membershipRes.IsInRoom {
 			// re-invite the user
@@ -237,7 +243,10 @@ func SendServerNotice(
 		false,
 	); err != nil {
 		util.GetLogger(ctx).WithError(err).Error("SendEvents failed")
-		return spec.InternalServerError()
+		return util.JSONResponse{
+			Code: http.StatusInternalServerError,
+			JSON: spec.InternalServerError{},
+		}
 	}
 	util.GetLogger(ctx).WithFields(logrus.Fields{
 		"event_id":     e.EventID(),
diff --git a/clientapi/routing/state.go b/clientapi/routing/state.go
index 75abbda9..319f4eba 100644
--- a/clientapi/routing/state.go
+++ b/clientapi/routing/state.go
@@ -56,7 +56,10 @@ func OnIncomingStateRequest(ctx context.Context, device *userapi.Device, rsAPI a
 		StateToFetch: []gomatrixserverlib.StateKeyTuple{},
 	}, &stateRes); err != nil {
 		util.GetLogger(ctx).WithError(err).Error("queryAPI.QueryLatestEventsAndState failed")
-		return spec.InternalServerError()
+		return util.JSONResponse{
+			Code: http.StatusInternalServerError,
+			JSON: spec.InternalServerError{},
+		}
 	}
 	if !stateRes.RoomExists {
 		return util.JSONResponse{
@@ -73,7 +76,10 @@ func OnIncomingStateRequest(ctx context.Context, device *userapi.Device, rsAPI a
 			content := map[string]string{}
 			if err := json.Unmarshal(ev.Content(), &content); err != nil {
 				util.GetLogger(ctx).WithError(err).Error("json.Unmarshal for history visibility failed")
-				return spec.InternalServerError()
+				return util.JSONResponse{
+					Code: http.StatusInternalServerError,
+					JSON: spec.InternalServerError{},
+				}
 			}
 			if visibility, ok := content["history_visibility"]; ok {
 				worldReadable = visibility == "world_readable"
@@ -99,7 +105,10 @@ func OnIncomingStateRequest(ctx context.Context, device *userapi.Device, rsAPI a
 		}, &membershipRes)
 		if err != nil {
 			util.GetLogger(ctx).WithError(err).Error("Failed to QueryMembershipForUser")
-			return spec.InternalServerError()
+			return util.JSONResponse{
+				Code: http.StatusInternalServerError,
+				JSON: spec.InternalServerError{},
+			}
 		}
 		// If the user has never been in the room then stop at this point.
 		// We won't tell the user about a room they have never joined.
@@ -147,7 +156,10 @@ func OnIncomingStateRequest(ctx context.Context, device *userapi.Device, rsAPI a
 		}, &stateAfterRes)
 		if err != nil {
 			util.GetLogger(ctx).WithError(err).Error("Failed to QueryMembershipForUser")
-			return spec.InternalServerError()
+			return util.JSONResponse{
+				Code: http.StatusInternalServerError,
+				JSON: spec.InternalServerError{},
+			}
 		}
 		for _, ev := range stateAfterRes.StateEvents {
 			stateEvents = append(
@@ -202,7 +214,10 @@ func OnIncomingStateTypeRequest(
 		StateToFetch: stateToFetch,
 	}, &stateRes); err != nil {
 		util.GetLogger(ctx).WithError(err).Error("queryAPI.QueryLatestEventsAndState failed")
-		return spec.InternalServerError()
+		return util.JSONResponse{
+			Code: http.StatusInternalServerError,
+			JSON: spec.InternalServerError{},
+		}
 	}
 
 	// Look at the room state and see if we have a history visibility event
@@ -213,7 +228,10 @@ func OnIncomingStateTypeRequest(
 			content := map[string]string{}
 			if err := json.Unmarshal(ev.Content(), &content); err != nil {
 				util.GetLogger(ctx).WithError(err).Error("json.Unmarshal for history visibility failed")
-				return spec.InternalServerError()
+				return util.JSONResponse{
+					Code: http.StatusInternalServerError,
+					JSON: spec.InternalServerError{},
+				}
 			}
 			if visibility, ok := content["history_visibility"]; ok {
 				worldReadable = visibility == "world_readable"
@@ -239,7 +257,10 @@ func OnIncomingStateTypeRequest(
 		}, &membershipRes)
 		if err != nil {
 			util.GetLogger(ctx).WithError(err).Error("Failed to QueryMembershipForUser")
-			return spec.InternalServerError()
+			return util.JSONResponse{
+				Code: http.StatusInternalServerError,
+				JSON: spec.InternalServerError{},
+			}
 		}
 		// If the user has never been in the room then stop at this point.
 		// We won't tell the user about a room they have never joined.
@@ -294,7 +315,10 @@ func OnIncomingStateTypeRequest(
 		}, &stateAfterRes)
 		if err != nil {
 			util.GetLogger(ctx).WithError(err).Error("Failed to QueryMembershipForUser")
-			return spec.InternalServerError()
+			return util.JSONResponse{
+				Code: http.StatusInternalServerError,
+				JSON: spec.InternalServerError{},
+			}
 		}
 		if len(stateAfterRes.StateEvents) > 0 {
 			event = stateAfterRes.StateEvents[0]
diff --git a/clientapi/routing/thirdparty.go b/clientapi/routing/thirdparty.go
index 0ee21855..b805d4b5 100644
--- a/clientapi/routing/thirdparty.go
+++ b/clientapi/routing/thirdparty.go
@@ -33,7 +33,10 @@ func Protocols(req *http.Request, asAPI appserviceAPI.AppServiceInternalAPI, dev
 	resp := &appserviceAPI.ProtocolResponse{}
 
 	if err := asAPI.Protocols(req.Context(), &appserviceAPI.ProtocolRequest{Protocol: protocol}, resp); err != nil {
-		return spec.InternalServerError()
+		return util.JSONResponse{
+			Code: http.StatusInternalServerError,
+			JSON: spec.InternalServerError{},
+		}
 	}
 	if !resp.Exists {
 		if protocol != "" {
@@ -71,7 +74,10 @@ func User(req *http.Request, asAPI appserviceAPI.AppServiceInternalAPI, device *
 		Protocol: protocol,
 		Params:   params.Encode(),
 	}, resp); err != nil {
-		return spec.InternalServerError()
+		return util.JSONResponse{
+			Code: http.StatusInternalServerError,
+			JSON: spec.InternalServerError{},
+		}
 	}
 	if !resp.Exists {
 		return util.JSONResponse{
@@ -97,7 +103,10 @@ func Location(req *http.Request, asAPI appserviceAPI.AppServiceInternalAPI, devi
 		Protocol: protocol,
 		Params:   params.Encode(),
 	}, resp); err != nil {
-		return spec.InternalServerError()
+		return util.JSONResponse{
+			Code: http.StatusInternalServerError,
+			JSON: spec.InternalServerError{},
+		}
 	}
 	if !resp.Exists {
 		return util.JSONResponse{
diff --git a/clientapi/routing/threepid.go b/clientapi/routing/threepid.go
index 64fa59e4..5261a140 100644
--- a/clientapi/routing/threepid.go
+++ b/clientapi/routing/threepid.go
@@ -60,28 +60,37 @@ func RequestEmailToken(req *http.Request, threePIDAPI api.ClientUserAPI, cfg *co
 
 	if err != nil {
 		util.GetLogger(req.Context()).WithError(err).Error("threePIDAPI.QueryLocalpartForThreePID failed")
-		return spec.InternalServerError()
+		return util.JSONResponse{
+			Code: http.StatusInternalServerError,
+			JSON: spec.InternalServerError{},
+		}
 	}
 
 	if len(res.Localpart) > 0 {
 		return util.JSONResponse{
 			Code: http.StatusBadRequest,
 			JSON: spec.MatrixError{
-				ErrCode: "M_THREEPID_IN_USE",
+				ErrCode: spec.ErrorThreePIDInUse,
 				Err:     userdb.Err3PIDInUse.Error(),
 			},
 		}
 	}
 
 	resp.SID, err = threepid.CreateSession(req.Context(), body, cfg, client)
-	if err == threepid.ErrNotTrusted {
+	switch err.(type) {
+	case nil:
+	case threepid.ErrNotTrusted:
+		util.GetLogger(req.Context()).WithError(err).Error("threepid.CreateSession failed")
 		return util.JSONResponse{
 			Code: http.StatusBadRequest,
 			JSON: spec.NotTrusted(body.IDServer),
 		}
-	} else if err != nil {
+	default:
 		util.GetLogger(req.Context()).WithError(err).Error("threepid.CreateSession failed")
-		return spec.InternalServerError()
+		return util.JSONResponse{
+			Code: http.StatusInternalServerError,
+			JSON: spec.InternalServerError{},
+		}
 	}
 
 	return util.JSONResponse{
@@ -102,21 +111,27 @@ func CheckAndSave3PIDAssociation(
 
 	// Check if the association has been validated
 	verified, address, medium, err := threepid.CheckAssociation(req.Context(), body.Creds, cfg, client)
-	if err == threepid.ErrNotTrusted {
+	switch err.(type) {
+	case nil:
+	case threepid.ErrNotTrusted:
+		util.GetLogger(req.Context()).WithError(err).Error("threepid.CheckAssociation failed")
 		return util.JSONResponse{
 			Code: http.StatusBadRequest,
 			JSON: spec.NotTrusted(body.Creds.IDServer),
 		}
-	} else if err != nil {
+	default:
 		util.GetLogger(req.Context()).WithError(err).Error("threepid.CheckAssociation failed")
-		return spec.InternalServerError()
+		return util.JSONResponse{
+			Code: http.StatusInternalServerError,
+			JSON: spec.InternalServerError{},
+		}
 	}
 
 	if !verified {
 		return util.JSONResponse{
 			Code: http.StatusBadRequest,
 			JSON: spec.MatrixError{
-				ErrCode: "M_THREEPID_AUTH_FAILED",
+				ErrCode: spec.ErrorThreePIDAuthFailed,
 				Err:     "Failed to auth 3pid",
 			},
 		}
@@ -127,7 +142,10 @@ func CheckAndSave3PIDAssociation(
 		err = threepid.PublishAssociation(req.Context(), body.Creds, device.UserID, cfg, client)
 		if err != nil {
 			util.GetLogger(req.Context()).WithError(err).Error("threepid.PublishAssociation failed")
-			return spec.InternalServerError()
+			return util.JSONResponse{
+				Code: http.StatusInternalServerError,
+				JSON: spec.InternalServerError{},
+			}
 		}
 	}
 
@@ -135,7 +153,10 @@ func CheckAndSave3PIDAssociation(
 	localpart, domain, err := gomatrixserverlib.SplitID('@', device.UserID)
 	if err != nil {
 		util.GetLogger(req.Context()).WithError(err).Error("gomatrixserverlib.SplitID failed")
-		return spec.InternalServerError()
+		return util.JSONResponse{
+			Code: http.StatusInternalServerError,
+			JSON: spec.InternalServerError{},
+		}
 	}
 
 	if err = threePIDAPI.PerformSaveThreePIDAssociation(req.Context(), &api.PerformSaveThreePIDAssociationRequest{
@@ -145,7 +166,10 @@ func CheckAndSave3PIDAssociation(
 		Medium:     medium,
 	}, &struct{}{}); err != nil {
 		util.GetLogger(req.Context()).WithError(err).Error("threePIDAPI.PerformSaveThreePIDAssociation failed")
-		return spec.InternalServerError()
+		return util.JSONResponse{
+			Code: http.StatusInternalServerError,
+			JSON: spec.InternalServerError{},
+		}
 	}
 
 	return util.JSONResponse{
@@ -161,7 +185,10 @@ func GetAssociated3PIDs(
 	localpart, domain, err := gomatrixserverlib.SplitID('@', device.UserID)
 	if err != nil {
 		util.GetLogger(req.Context()).WithError(err).Error("gomatrixserverlib.SplitID failed")
-		return spec.InternalServerError()
+		return util.JSONResponse{
+			Code: http.StatusInternalServerError,
+			JSON: spec.InternalServerError{},
+		}
 	}
 
 	res := &api.QueryThreePIDsForLocalpartResponse{}
@@ -171,7 +198,10 @@ func GetAssociated3PIDs(
 	}, res)
 	if err != nil {
 		util.GetLogger(req.Context()).WithError(err).Error("threepidAPI.QueryThreePIDsForLocalpart failed")
-		return spec.InternalServerError()
+		return util.JSONResponse{
+			Code: http.StatusInternalServerError,
+			JSON: spec.InternalServerError{},
+		}
 	}
 
 	return util.JSONResponse{
@@ -192,7 +222,10 @@ func Forget3PID(req *http.Request, threepidAPI api.ClientUserAPI) util.JSONRespo
 		Medium:   body.Medium,
 	}, &struct{}{}); err != nil {
 		util.GetLogger(req.Context()).WithError(err).Error("threepidAPI.PerformForgetThreePID failed")
-		return spec.InternalServerError()
+		return util.JSONResponse{
+			Code: http.StatusInternalServerError,
+			JSON: spec.InternalServerError{},
+		}
 	}
 
 	return util.JSONResponse{
diff --git a/clientapi/routing/upgrade_room.go b/clientapi/routing/upgrade_room.go
index 43f8d3e2..a0b28078 100644
--- a/clientapi/routing/upgrade_room.go
+++ b/clientapi/routing/upgrade_room.go
@@ -68,13 +68,16 @@ func UpgradeRoom(
 			JSON: spec.Forbidden(e.Error()),
 		}
 	default:
-		if errors.Is(err, eventutil.ErrRoomNoExists) {
+		if errors.Is(err, eventutil.ErrRoomNoExists{}) {
 			return util.JSONResponse{
 				Code: http.StatusNotFound,
 				JSON: spec.NotFound("Room does not exist"),
 			}
 		}
-		return spec.InternalServerError()
+		return util.JSONResponse{
+			Code: http.StatusInternalServerError,
+			JSON: spec.InternalServerError{},
+		}
 	}
 
 	return util.JSONResponse{
diff --git a/clientapi/routing/voip.go b/clientapi/routing/voip.go
index f3db0cbe..14a08b79 100644
--- a/clientapi/routing/voip.go
+++ b/clientapi/routing/voip.go
@@ -60,7 +60,10 @@ func RequestTurnServer(req *http.Request, device *api.Device, cfg *config.Client
 
 		if err != nil {
 			util.GetLogger(req.Context()).WithError(err).Error("mac.Write failed")
-			return spec.InternalServerError()
+			return util.JSONResponse{
+				Code: http.StatusInternalServerError,
+				JSON: spec.InternalServerError{},
+			}
 		}
 
 		resp.Password = base64.StdEncoding.EncodeToString(mac.Sum(nil))
diff --git a/clientapi/threepid/invites.go b/clientapi/threepid/invites.go
index 2e9c1261..c296939d 100644
--- a/clientapi/threepid/invites.go
+++ b/clientapi/threepid/invites.go
@@ -64,14 +64,34 @@ type idServerStoreInviteResponse struct {
 }
 
 var (
-	// ErrMissingParameter is the error raised if a request for 3PID invite has
-	// an incomplete body
-	ErrMissingParameter = errors.New("'address', 'id_server' and 'medium' must all be supplied")
-	// ErrNotTrusted is the error raised if an identity server isn't in the list
-	// of trusted servers in the configuration file.
-	ErrNotTrusted = errors.New("untrusted server")
+	errMissingParameter = fmt.Errorf("'address', 'id_server' and 'medium' must all be supplied")
+	errNotTrusted       = fmt.Errorf("untrusted server")
 )
 
+// ErrMissingParameter is the error raised if a request for 3PID invite has
+// an incomplete body
+type ErrMissingParameter struct{}
+
+func (e ErrMissingParameter) Error() string {
+	return errMissingParameter.Error()
+}
+
+func (e ErrMissingParameter) Unwrap() error {
+	return errMissingParameter
+}
+
+// ErrNotTrusted is the error raised if an identity server isn't in the list
+// of trusted servers in the configuration file.
+type ErrNotTrusted struct{}
+
+func (e ErrNotTrusted) Error() string {
+	return errNotTrusted.Error()
+}
+
+func (e ErrNotTrusted) Unwrap() error {
+	return errNotTrusted
+}
+
 // CheckAndProcessInvite analyses the body of an incoming membership request.
 // If the fields relative to a third-party-invite are all supplied, lookups the
 // matching Matrix ID from the given identity server. If no Matrix ID is
@@ -99,7 +119,7 @@ func CheckAndProcessInvite(
 	} else if body.Address == "" || body.IDServer == "" || body.Medium == "" {
 		// If at least one of the 3PID-specific fields is supplied but not all
 		// of them, return an error
-		err = ErrMissingParameter
+		err = ErrMissingParameter{}
 		return
 	}
 
diff --git a/clientapi/threepid/threepid.go b/clientapi/threepid/threepid.go
index 1fe573b1..d61052cc 100644
--- a/clientapi/threepid/threepid.go
+++ b/clientapi/threepid/threepid.go
@@ -26,6 +26,7 @@ import (
 
 	"github.com/matrix-org/dendrite/setup/config"
 	"github.com/matrix-org/gomatrixserverlib/fclient"
+	"github.com/matrix-org/gomatrixserverlib/spec"
 )
 
 // EmailAssociationRequest represents the request defined at https://matrix.org/docs/spec/client_server/r0.2.0.html#post-matrix-client-r0-register-email-requesttoken
@@ -133,7 +134,7 @@ func CheckAssociation(
 		return false, "", "", err
 	}
 
-	if respBody.ErrCode == "M_SESSION_NOT_VALIDATED" {
+	if respBody.ErrCode == string(spec.ErrorSessionNotValidated) {
 		return false, "", "", nil
 	} else if len(respBody.ErrCode) > 0 {
 		return false, "", "", errors.New(respBody.Error)
@@ -186,5 +187,5 @@ func isTrusted(idServer string, cfg *config.ClientAPI) error {
 			return nil
 		}
 	}
-	return ErrNotTrusted
+	return ErrNotTrusted{}
 }