Decode partial domain name labels

Signed-off-by: Erik Geiser <erik.geiser@redteam-pentesting.de>

2 files changed, 11 insertions, 1 deletions

diff --git a/rfc1035label/label.go b/rfc1035label/label.go
index 5a67d7c..561008e 100644
--- a/rfc1035label/label.go
+++ b/rfc1035label/label.go
@@ -100,6 +100,14 @@ func labelsFromBytes(buf []byte) ([]string, error) {
 
 	for {
 		if pos >= len(buf) {
+			// interpret label without trailing zero-length byte as a partial
+			// domain name field as per RFC 4704 Section 4.2
+			if label != "" {
+				labels = append(labels, label)
+
+				return labels, nil
+			}
+
 			break
 		}
 		length := int(buf[pos])
diff --git a/rfc1035label/label_test.go b/rfc1035label/label_test.go
index 2e20736..865b41a 100644
--- a/rfc1035label/label_test.go
+++ b/rfc1035label/label_test.go
@@ -28,7 +28,9 @@ func TestLabelsFromBytesZeroLength(t *testing.T) {
 	require.Equal(t, []byte{}, labels.ToBytes())
 }
 
-func TestLabelsFromBytesWithoutZeroLength(t *testing.T) {
+func TestLabelsFromBytesPartialDomainName(t *testing.T) {
+	// Partial domain name without trailing zero-length byte as per RFC 4704
+	// Section 4.2
 	expected := []byte{
 		0x8, 'h', 'o', 's', 't', 'n', 'a', 'm', 'e',
 	}