From 04cbdae47a19c4a396a22f488840565638c47c39 Mon Sep 17 00:00:00 2001
From: Miek Gieben <miek@miek.nl>
Date: Mon, 23 Jan 2012 20:29:47 +0100
Subject: [PATCH] Fix DS overflow when unpacking

---
 msg.go | 8 ++++----
 1 file changed, 4 insertions(+), 4 deletions(-)

diff --git a/msg.go b/msg.go
index 72a18e1b..1abfb708 100644
--- a/msg.go
+++ b/msg.go
@@ -764,10 +764,6 @@ func unpackStructValue(val reflect.Value, msg []byte, off int) (off1 int, ok boo
 			case "hex":
 				// Rest of the RR is hex encoded, network order an issue here?
 				rdlength := int(val.FieldByName("Hdr").FieldByName("Rdlength").Uint())
-				if off+rdlength > lenmsg {
-					// too large
-					return lenmsg, false
-				}
 				var consumed int
 				switch val.Type().Name() {
 				case "RR_DS":
@@ -781,6 +777,10 @@ func unpackStructValue(val reflect.Value, msg []byte, off int) (off1 int, ok boo
 				default:
 					consumed = 0 // return len(msg), false?
 				}
+				if off+rdlength-consumed > lenmsg {
+                                        println("dns: overflow when unpacking hex string")
+					return lenmsg, false
+				}
 				s = hex.EncodeToString(msg[off : off+rdlength-consumed])
 				off += rdlength - consumed
 			case "base64":