Handle HEAD/GET requests for virtual DNS requests (#7839)

r.URL.Path is empty when HEAD bucket with virtual
DNS requests come in since bucket is now part of
r.Host, we should use our domain names and fetch
the right bucket/object names.

This fixes an really old issue in our federation
setups.

cmd/generic-handlers.go

@@ -294,7 +294,7 @@ func (h minioReservedBucketHandler) ServeHTTP(w http.ResponseWriter, r *http.Req
 	default:
 		// For all other requests reject access to reserved
 		// buckets
-		bucketName, _ := urlPath2BucketObjectName(r.URL.Path)
+		bucketName, _ := request2BucketObjectName(r)
 		if isMinioReservedBucket(bucketName) || isMinioMetaBucket(bucketName) {
 			writeErrorResponse(context.Background(), w, errorCodes.ToAPIErr(ErrAllAccessDisabled), r.URL, guessIsBrowserReq(r))
 			return
@@ -494,7 +494,7 @@ var notimplementedObjectResourceNames = map[string]bool{
 
 // Resource handler ServeHTTP() wrapper
 func (h resourceHandler) ServeHTTP(w http.ResponseWriter, r *http.Request) {
-	bucketName, objectName := urlPath2BucketObjectName(r.URL.Path)
+	bucketName, objectName := request2BucketObjectName(r)
 
 	// If bucketName is present and not objectName check for bucket level resource queries.
 	if bucketName != "" && objectName == "" {
@@ -696,7 +696,8 @@ func (f bucketForwardingHandler) ServeHTTP(w http.ResponseWriter, r *http.Reques
 		return
 	}
 
-	bucket, object := urlPath2BucketObjectName(r.URL.Path)
+	bucket, object := request2BucketObjectName(r)
+
 	// ListBucket requests should be handled at current endpoint as
 	// all buckets data can be fetched from here.
 	if r.Method == http.MethodGet && bucket == "" && object == "" {

cmd/utils.go

@@ -71,8 +71,20 @@ func cloneHeader(h http.Header) http.Header {
 	return h2
 }
 
+func request2BucketObjectName(r *http.Request) (bucketName, objectName string) {
+	path, err := getResource(r.URL.Path, r.Host, globalDomainNames)
+	if err != nil {
+		logger.CriticalIf(context.Background(), err)
+	}
+	return urlPath2BucketObjectName(path)
+}
+
 // Convert url path into bucket and object name.
 func urlPath2BucketObjectName(path string) (bucketName, objectName string) {
+	if path == "" || path == slashSeparator {
+		return "", ""
+	}
+
 	// Trim any preceding slash separator.
 	urlPath := strings.TrimPrefix(path, slashSeparator)