Improve read.ProtoJSON bad protobuf body error handling

api/read/read.go

@@ -10,6 +10,7 @@ import (
 	"google.golang.org/protobuf/encoding/protojson"
 	"google.golang.org/protobuf/proto"
 
+	"github.com/smallstep/certificates/api/render"
 	"github.com/smallstep/certificates/errs"
 )
 
@@ -29,49 +30,35 @@ func ProtoJSON(r io.Reader, m proto.Message) error {
 	if err != nil {
 		return errs.BadRequestErr(err, "error reading request body")
 	}
-	if err := protojson.Unmarshal(data, m); err != nil {
-		if errors.Is(err, proto.Error) {
-			return newBadProtoJSONError(err)
-		}
+
+	switch err := protojson.Unmarshal(data, m); {
+	case errors.Is(err, proto.Error):
+		return badProtoJSONError(err.Error())
+	default:
+		return err
 	}
-	return err
 }
 
-// BadProtoJSONError is an error type that is used when a proto
-// message cannot be unmarshaled. Usually this is caused by an error
-// in the request body.
-type BadProtoJSONError struct {
-	err     error
-	Type    string `json:"type"`
-	Detail  string `json:"detail"`
-	Message string `json:"message"`
+// badProtoJSONError is an error type that is returned by ProtoJSON
+// when a proto message cannot be unmarshaled. Usually this is caused
+// by an error in the request body.
+type badProtoJSONError string
+
+// Error implements error for badProtoJSONError
+func (e badProtoJSONError) Error() string {
+	return string(e)
 }
 
-// newBadProtoJSONError returns a new instance of BadProtoJSONError
-// This error type is always caused by an error in the request body.
-func newBadProtoJSONError(err error) *BadProtoJSONError {
-	return &BadProtoJSONError{
-		err:     err,
+// Render implements render.RenderableError for badProtoJSONError
+func (e badProtoJSONError) Render(w http.ResponseWriter) {
+	v := struct {
+		Type    string `json:"type"`
+		Detail  string `json:"detail"`
+		Message string `json:"message"`
+	}{
 		Type:    "badRequest",
 		Detail:  "bad request",
-		Message: err.Error(),
+		Message: e.Error(),
 	}
-}
-
-// Error implements the error interface
-func (e *BadProtoJSONError) Error() string {
-	return e.err.Error()
-}
-
-// Render implements render.RenderableError for BadProtoError
-func (e *BadProtoJSONError) Render(w http.ResponseWriter) {
-
-	errData, err := json.Marshal(e)
-	if err != nil {
-		panic(err)
-	}
-
-	w.Header().Set("Content-Type", "application/json")
-	w.WriteHeader(http.StatusBadRequest)
-	w.Write(errData)
+	render.JSONStatus(w, v, http.StatusBadRequest)
 }