use xml marshaling to render error

Signed-off-by: Jörn Friedrich Dreyer <jfd@butonic.de>

internal/http/services/owncloud/ocdav/error.go

@@ -23,18 +23,23 @@ import (
 	"net/http"
 
 	rpc "github.com/cs3org/go-cs3apis/cs3/rpc/v1beta1"
+	"github.com/pkg/errors"
 	"github.com/rs/zerolog"
 )
 
 type code int
 
 const (
+
+	// SabredavMethodBadRequest maps to HTTP 400
+	SabredavMethodBadRequest code = iota
 	// SabredavMethodNotAllowed maps to HTTP 405
-	SabredavMethodNotAllowed code = iota
+	SabredavMethodNotAllowed
 )
 
 var (
 	codesEnum = []string{
+		"Sabre\\DAV\\Exception\\BadRequest",
 		"Sabre\\DAV\\Exception\\MethodNotAllowed",
 	}
 )
@@ -54,6 +59,18 @@ func Marshal(e exception) ([]byte, error) {
 	})
 }
 
+// http://www.webdav.org/specs/rfc4918.html#ELEMENT_error
+type errorXML struct {
+	XMLName   xml.Name `xml:"d:error"`
+	Xmlnsd    string   `xml:"xmlns:d,attr"`
+	Xmlnss    string   `xml:"xmlns:s,attr"`
+	Exception string   `xml:"s:exception"`
+	Message   string   `xml:"s:message"`
+	InnerXML  []byte   `xml:",innerxml"`
+}
+
+var errInvalidPropfind = errors.New("webdav: invalid propfind")
+
 // HandleErrorStatus checks the status code, logs a Debug or Error level message
 // and writes an appropriate http status
 func HandleErrorStatus(log *zerolog.Logger, w http.ResponseWriter, s *rpc.Status) {

internal/http/services/owncloud/ocdav/put.go

@@ -283,12 +283,16 @@ func (s *svc) handlePutHelper(w http.ResponseWriter, r *http.Request, content io
 			}
 			if httpRes.StatusCode == errtypes.StatusChecksumMismatch {
 				w.WriteHeader(http.StatusBadRequest)
-				xml := `<?xml version="1.0" encoding="utf-8"?>
-<d:error xmlns:d="DAV:" xmlns:s="http://sabredav.org/ns">
-  <s:exception>Sabre\DAV\Exception\BadRequest</s:exception>
-  <s:message>The computed checksum does not match the one received from the client.</s:message>
-</d:error>`
-				_, err := w.Write([]byte(xml))
+				b, err := Marshal(exception{
+					code:    SabredavMethodBadRequest,
+					message: "The computed checksum does not match the one received from the client.",
+				})
+				if err != nil {
+					sublog.Error().Msgf("error marshaling xml response: %s", b)
+					w.WriteHeader(http.StatusInternalServerError)
+					return
+				}
+				_, err = w.Write(b)
 				if err != nil {
 					sublog.Err(err).Msg("error writing response")
 				}