use correct xml package for custom MarshalXML() (#16421)

cmd/api-headers.go

@@ -20,6 +20,7 @@ package cmd
 import (
 	"bytes"
 	"encoding/json"
+	"encoding/xml"
 	"fmt"
 	"net/http"
 	"net/url"
@@ -64,15 +65,31 @@ func setCommonHeaders(w http.ResponseWriter) {
 
 // Encodes the response headers into XML format.
 func encodeResponse(response interface{}) []byte {
-	var bytesBuffer bytes.Buffer
-	bytesBuffer.WriteString(xxml.Header)
-	buf, err := xxml.Marshal(response)
-	if err != nil {
+	var buf bytes.Buffer
+	buf.WriteString(xml.Header)
+	if err := xml.NewEncoder(&buf).Encode(response); err != nil {
 		logger.LogIf(GlobalContext, err)
 		return nil
 	}
-	bytesBuffer.Write(buf)
-	return bytesBuffer.Bytes()
+	return buf.Bytes()
+}
+
+// Use this encodeResponseList() to support control characters
+// this function must be used by only ListObjects() for objects
+// with control characters, this is a specialized extension
+// to support AWS S3 compatible behavior.
+//
+// Do not use this function for anything other than ListObjects()
+// variants, please open a github discussion if you wish to use
+// this in other places.
+func encodeResponseList(response interface{}) []byte {
+	var buf bytes.Buffer
+	buf.WriteString(xxml.Header)
+	if err := xxml.NewEncoder(&buf).Encode(response); err != nil {
+		logger.LogIf(GlobalContext, err)
+		return nil
+	}
+	return buf.Bytes()
 }
 
 // Encodes the response headers into JSON format.

cmd/api-response.go

@@ -314,12 +314,12 @@ func (s *Metadata) Set(k, v string) {
 }
 
 type xmlKeyEntry struct {
-	XMLName xml.Name
+	XMLName xxml.Name
 	Value   string `xml:",chardata"`
 }
 
 // MarshalXML - StringMap marshals into XML.
-func (s *Metadata) MarshalXML(e *xml.Encoder, start xml.StartElement) error {
+func (s *Metadata) MarshalXML(e *xxml.Encoder, start xxml.StartElement) error {
 	if s == nil {
 		return nil
 	}
@@ -334,7 +334,7 @@ func (s *Metadata) MarshalXML(e *xml.Encoder, start xml.StartElement) error {
 
 	for _, item := range s.Items {
 		if err := e.Encode(xmlKeyEntry{
-			XMLName: xml.Name{Local: item.Key},
+			XMLName: xxml.Name{Local: item.Key},
 			Value:   item.Value,
 		}); err != nil {
 			return err

cmd/bucket-listobjects-handlers.go

@@ -115,7 +115,7 @@ func (api objectAPIHandlers) ListObjectVersionsHandler(w http.ResponseWriter, r
 	response := generateListVersionsResponse(bucket, prefix, marker, versionIDMarker, delimiter, encodingType, maxkeys, listObjectVersionsInfo)
 
 	// Write success response.
-	writeSuccessResponseXML(w, encodeResponse(response))
+	writeSuccessResponseXML(w, encodeResponseList(response))
 }
 
 // ListObjectsV2MHandler - GET Bucket (List Objects) Version 2 with metadata.
@@ -185,7 +185,7 @@ func (api objectAPIHandlers) ListObjectsV2MHandler(w http.ResponseWriter, r *htt
 		maxKeys, listObjectsV2Info.Objects, listObjectsV2Info.Prefixes, true)
 
 	// Write success response.
-	writeSuccessResponseXML(w, encodeResponse(response))
+	writeSuccessResponseXML(w, encodeResponseList(response))
 }
 
 // ListObjectsV2Handler - GET Bucket (List Objects) Version 2.
@@ -260,7 +260,7 @@ func (api objectAPIHandlers) ListObjectsV2Handler(w http.ResponseWriter, r *http
 		maxKeys, listObjectsV2Info.Objects, listObjectsV2Info.Prefixes, false)
 
 	// Write success response.
-	writeSuccessResponseXML(w, encodeResponse(response))
+	writeSuccessResponseXML(w, encodeResponseList(response))
 }
 
 func parseRequestToken(token string) (subToken string, nodeIndex int) {
@@ -357,5 +357,5 @@ func (api objectAPIHandlers) ListObjectsV1Handler(w http.ResponseWriter, r *http
 	response := generateListObjectsV1Response(bucket, prefix, marker, delimiter, encodingType, maxKeys, listObjectsInfo)
 
 	// Write success response.
-	writeSuccessResponseXML(w, encodeResponse(response))
+	writeSuccessResponseXML(w, encodeResponseList(response))
 }