Use golang.org/x/crypto/cryptobyte to unpack DNS records

client.go

@@ -300,7 +300,8 @@ func (co *Conn) ReadMsgHeader(hdr *Header) ([]byte, error) {
 
 	p = p[:n]
 	if hdr != nil {
-		dh, _, err := unpackMsgHdr(p, 0)
+		s := newDNSString(p, 0)
+		dh, err := unpackMsgHdr(s)
 		if err != nil {
 			return nil, err
 		}

dns.go

@@ -52,7 +52,7 @@ type RR interface {
 	//
 	// This will only be called on a new and empty RR type with only the header populated. It
 	// will only be called if the record's RDATA is non-empty.
-	unpack(msg []byte, off int) (off1 int, err error)
+	unpack(msg *dnsString) error
 
 	// parse parses an RR from zone file format.
 	//
@@ -104,7 +104,7 @@ func (h *RR_Header) pack(msg []byte, off int, compression compressionMap, compre
 	return off, nil
 }
 
-func (h *RR_Header) unpack(msg []byte, off int) (int, error) {
+func (h *RR_Header) unpack(msg *dnsString) error {
 	panic("dns: internal error: unpack should never be called on RR_Header")
 }
 
@@ -128,8 +128,8 @@ func (rr *RFC3597) ToRFC3597(r RR) error {
 		return nil
 	}
 
-	_, err = rr.unpack(buf, headerEnd)
-	return err
+	s := newDNSString(buf, headerEnd)
+	return rr.unpack(s)
 }
 
 // fromRFC3597 converts an unknown RR representation from RFC 3597 to the known RR type.
@@ -153,6 +153,6 @@ func (rr *RFC3597) fromRFC3597(r RR) error {
 		return err
 	}
 
-	_, err = r.unpack(msg, 0)
-	return err
+	s := newDNSString(msg, 0)
+	return r.unpack(s)
 }

dns_test.go

@@ -254,8 +254,7 @@ func TestMsgPackBuffer(t *testing.T) {
 		input, _ := hex.DecodeString(hexData)
 		m := new(Msg)
 		if err := m.Unpack(input); err != nil {
-			t.Errorf("packet %d failed to unpack", i)
-			continue
+			t.Errorf("packet %d failed to unpack: %v", i, err)
 		}
 	}
 }

go.mod

@@ -3,6 +3,7 @@ module github.com/miekg/dns
 go 1.19
 
 require (
+	golang.org/x/crypto v0.14.0
 	golang.org/x/net v0.17.0
 	golang.org/x/sync v0.4.0
 	golang.org/x/sys v0.13.0

go.sum

@@ -1,3 +1,5 @@
+golang.org/x/crypto v0.14.0 h1:wBqGXzWJW6m1XrIKlAH0Hs1JJ7+9KBwnIO8v66Q9cHc=
+golang.org/x/crypto v0.14.0/go.mod h1:MVFd36DqK4CsrnJYDkBA3VC4m2GkXAM0PvzMCn4JQf4=
 golang.org/x/mod v0.12.0 h1:rmsUpXtvNzj340zd98LZ4KntptpfRHwpFOHG188oHXc=
 golang.org/x/mod v0.12.0/go.mod h1:iBbtSCu2XBx23ZKBPSOrRkjjQPZFPuis4dIYUhu/chs=
 golang.org/x/net v0.17.0 h1:pVaXccu2ozPjCXewfr1S7xza/zcXTity9cCdXQYSjIM=