From fb16e4c487418c6f0787e6b1468d5def5b841354 Mon Sep 17 00:00:00 2001
From: Roland Bracewell Shoemaker <roland@bracewel.net>
Date: Tue, 21 Mar 2017 12:35:21 -0700
Subject: [PATCH] Only pack NSEC3/NSEC3PARAM salt when it is not empty (#474)

* Only pack when salt is not empty

* Actually generate things properly

* Use string literal
---
 msg_generate.go | 13 +++++++++++--
 zmsg.go         | 20 ++++++++++++--------
 2 files changed, 23 insertions(+), 10 deletions(-)

diff --git a/msg_generate.go b/msg_generate.go
index c29447a1..4d9f81d4 100644
--- a/msg_generate.go
+++ b/msg_generate.go
@@ -139,8 +139,17 @@ return off, err
 			case st.Tag(i) == `dns:"base64"`:
 				o("off, err = packStringBase64(rr.%s, msg, off)\n")
 
-			case strings.HasPrefix(st.Tag(i), `dns:"size-hex:SaltLength`): // Hack to fix empty salt length for NSEC3
-				o("if rr.%s == \"-\" { /* do nothing, empty salt */ }\n")
+			case strings.HasPrefix(st.Tag(i), `dns:"size-hex:SaltLength`):
+				// directly write instead of using o() so we get the error check in the correct place
+				field := st.Field(i).Name()
+				fmt.Fprintf(b, `// Only pack salt if value is not "-", i.e. empty
+if rr.%s != "-" {
+  off, err = packStringHex(rr.%s, msg, off)
+  if err != nil {
+    return off, err
+  }
+}
+`, field, field)
 				continue
 			case strings.HasPrefix(st.Tag(i), `dns:"size-hex`): // size-hex can be packed just like hex
 				fallthrough
diff --git a/zmsg.go b/zmsg.go
index 94627e35..9b98e1bb 100644
--- a/zmsg.go
+++ b/zmsg.go
@@ -801,10 +801,12 @@ func (rr *NSEC3) pack(msg []byte, off int, compression map[string]int, compress
 	if err != nil {
 		return off, err
 	}
-	if rr.Salt == "-" { /* do nothing, empty salt */
-	}
-	if err != nil {
-		return off, err
+	// Only pack salt if value is not "-", i.e. empty
+	if rr.Salt != "-" {
+		off, err = packStringHex(rr.Salt, msg, off)
+		if err != nil {
+			return off, err
+		}
 	}
 	off, err = packUint8(rr.HashLength, msg, off)
 	if err != nil {
@@ -844,10 +846,12 @@ func (rr *NSEC3PARAM) pack(msg []byte, off int, compression map[string]int, comp
 	if err != nil {
 		return off, err
 	}
-	if rr.Salt == "-" { /* do nothing, empty salt */
-	}
-	if err != nil {
-		return off, err
+	// Only pack salt if value is not "-", i.e. empty
+	if rr.Salt != "-" {
+		off, err = packStringHex(rr.Salt, msg, off)
+		if err != nil {
+			return off, err
+		}
 	}
 	rr.Header().Rdlength = uint16(off - headerEnd)
 	return off, nil