Introduce a generic slice clone function

clientconfig.go

@@ -68,7 +68,7 @@ func ClientConfigFromReader(resolvconf io.Reader) (*ClientConfig, error) {
 			}
 
 		case "search": // set search path to given servers
-			c.Search = append([]string(nil), f[1:]...)
+			c.Search = cloneSlice(f[1:])
 
 		case "options": // magic options
 			for _, s := range f[1:] {

edns.go

@@ -263,7 +263,7 @@ func (e *EDNS0_NSID) copy() EDNS0           { return &EDNS0_NSID{e.Code, e.Nsid}
 //	o.Hdr.Name = "."
 //	o.Hdr.Rrtype = dns.TypeOPT
 //	e := new(dns.EDNS0_SUBNET)
-//	e.Code = dns.EDNS0SUBNET // by default this is filled in through unpacking OPT packets (unpackDataOpt)  
+//	e.Code = dns.EDNS0SUBNET // by default this is filled in through unpacking OPT packets (unpackDataOpt)
 //	e.Family = 1	// 1 for IPv4 source address, 2 for IPv6
 //	e.SourceNetmask = 32	// 32 for IPV4, 128 for IPv6
 //	e.SourceScope = 0
@@ -520,8 +520,8 @@ type EDNS0_DAU struct {
 
 // Option implements the EDNS0 interface.
 func (e *EDNS0_DAU) Option() uint16        { return EDNS0DAU }
-func (e *EDNS0_DAU) pack() ([]byte, error) { return e.AlgCode, nil }
-func (e *EDNS0_DAU) unpack(b []byte) error { e.AlgCode = b; return nil }
+func (e *EDNS0_DAU) pack() ([]byte, error) { return cloneSlice(e.AlgCode), nil }
+func (e *EDNS0_DAU) unpack(b []byte) error { e.AlgCode = cloneSlice(b); return nil }
 
 func (e *EDNS0_DAU) String() string {
 	s := ""
@@ -544,8 +544,8 @@ type EDNS0_DHU struct {
 
 // Option implements the EDNS0 interface.
 func (e *EDNS0_DHU) Option() uint16        { return EDNS0DHU }
-func (e *EDNS0_DHU) pack() ([]byte, error) { return e.AlgCode, nil }
-func (e *EDNS0_DHU) unpack(b []byte) error { e.AlgCode = b; return nil }
+func (e *EDNS0_DHU) pack() ([]byte, error) { return cloneSlice(e.AlgCode), nil }
+func (e *EDNS0_DHU) unpack(b []byte) error { e.AlgCode = cloneSlice(b); return nil }
 
 func (e *EDNS0_DHU) String() string {
 	s := ""
@@ -568,8 +568,8 @@ type EDNS0_N3U struct {
 
 // Option implements the EDNS0 interface.
 func (e *EDNS0_N3U) Option() uint16        { return EDNS0N3U }
-func (e *EDNS0_N3U) pack() ([]byte, error) { return e.AlgCode, nil }
-func (e *EDNS0_N3U) unpack(b []byte) error { e.AlgCode = b; return nil }
+func (e *EDNS0_N3U) pack() ([]byte, error) { return cloneSlice(e.AlgCode), nil }
+func (e *EDNS0_N3U) unpack(b []byte) error { e.AlgCode = cloneSlice(b); return nil }
 
 func (e *EDNS0_N3U) String() string {
 	// Re-use the hash map
@@ -646,30 +646,21 @@ type EDNS0_LOCAL struct {
 
 // Option implements the EDNS0 interface.
 func (e *EDNS0_LOCAL) Option() uint16 { return e.Code }
+
 func (e *EDNS0_LOCAL) String() string {
 	return strconv.FormatInt(int64(e.Code), 10) + ":0x" + hex.EncodeToString(e.Data)
 }
+
 func (e *EDNS0_LOCAL) copy() EDNS0 {
-	b := make([]byte, len(e.Data))
-	copy(b, e.Data)
-	return &EDNS0_LOCAL{e.Code, b}
+	return &EDNS0_LOCAL{e.Code, cloneSlice(e.Data)}
 }
 
 func (e *EDNS0_LOCAL) pack() ([]byte, error) {
-	b := make([]byte, len(e.Data))
-	copied := copy(b, e.Data)
-	if copied != len(e.Data) {
-		return nil, ErrBuf
-	}
-	return b, nil
+	return cloneSlice(e.Data), nil
 }
 
 func (e *EDNS0_LOCAL) unpack(b []byte) error {
-	e.Data = make([]byte, len(b))
-	copied := copy(e.Data, b)
-	if copied != len(b) {
-		return ErrBuf
-	}
+	e.Data = cloneSlice(b)
 	return nil
 }
 
@@ -732,14 +723,10 @@ type EDNS0_PADDING struct {
 
 // Option implements the EDNS0 interface.
 func (e *EDNS0_PADDING) Option() uint16        { return EDNS0PADDING }
-func (e *EDNS0_PADDING) pack() ([]byte, error) { return e.Padding, nil }
-func (e *EDNS0_PADDING) unpack(b []byte) error { e.Padding = b; return nil }
+func (e *EDNS0_PADDING) pack() ([]byte, error) { return cloneSlice(e.Padding), nil }
+func (e *EDNS0_PADDING) unpack(b []byte) error { e.Padding = cloneSlice(b); return nil }
 func (e *EDNS0_PADDING) String() string        { return fmt.Sprintf("%0X", e.Padding) }
-func (e *EDNS0_PADDING) copy() EDNS0 {
-	b := make([]byte, len(e.Padding))
-	copy(b, e.Padding)
-	return &EDNS0_PADDING{b}
-}
+func (e *EDNS0_PADDING) copy() EDNS0           { return &EDNS0_PADDING{cloneSlice(e.Padding)} }
 
 // Extended DNS Error Codes (RFC 8914).
 const (
@@ -826,7 +813,7 @@ func (e *EDNS0_EDE) String() string {
 func (e *EDNS0_EDE) pack() ([]byte, error) {
 	b := make([]byte, 2+len(e.ExtraText))
 	binary.BigEndian.PutUint16(b[0:], e.InfoCode)
-	copy(b[2:], []byte(e.ExtraText))
+	copy(b[2:], e.ExtraText)
 	return b, nil
 }
 

go.mod

@@ -1,10 +1,12 @@
 module github.com/miekg/dns
 
-go 1.14
+go 1.19
 
 require (
 	golang.org/x/net v0.2.0
 	golang.org/x/sync v0.1.0
 	golang.org/x/sys v0.2.0
 	golang.org/x/tools v0.3.0
 )
+
+require golang.org/x/mod v0.7.0 // indirect

go.sum

@@ -1,35 +1,10 @@
-github.com/yuin/goldmark v1.4.13/go.mod h1:6yULJ656Px+3vBD8DxQVa3kxgyrAnzto9xy5taEt/CY=
-golang.org/x/crypto v0.0.0-20190308221718-c2843e01d9a2/go.mod h1:djNgcEr1/C05ACkg1iLfiJU5Ep61QUkGW8qpdssI0+w=
-golang.org/x/crypto v0.0.0-20210921155107-089bfa567519/go.mod h1:GvvjBRRGRdwPK5ydBHafDWAxML/pGHZbMvKqRZ5+Abc=
-golang.org/x/mod v0.6.0-dev.0.20220419223038-86c51ed26bb4/go.mod h1:jJ57K6gSWd91VN4djpZkiMVwK6gcyfeH4XE8wZrZaV4=
 golang.org/x/mod v0.7.0 h1:LapD9S96VoQRhi/GrNTqeBJFrUjs5UHCAtTlgwA5oZA=
 golang.org/x/mod v0.7.0/go.mod h1:iBbtSCu2XBx23ZKBPSOrRkjjQPZFPuis4dIYUhu/chs=
-golang.org/x/net v0.0.0-20190620200207-3b0461eec859/go.mod h1:z5CRVTTTmAJ677TzLLGU+0bjPO0LkuOLi4/5GtJWs/s=
-golang.org/x/net v0.0.0-20210226172049-e18ecbb05110/go.mod h1:m0MpNAwzfU5UDzcl9v0D8zg8gWTRqZa9RBIspLL5mdg=
-golang.org/x/net v0.0.0-20220722155237-a158d28d115b/go.mod h1:XRhObCWvk6IyKnWLug+ECip1KBveYUHfp+8e9klMJ9c=
 golang.org/x/net v0.2.0 h1:sZfSu1wtKLGlWI4ZZayP0ck9Y73K1ynO6gqzTdBVdPU=
 golang.org/x/net v0.2.0/go.mod h1:KqCZLdyyvdV855qA2rE3GC2aiw5xGR5TEjj8smXukLY=
-golang.org/x/sync v0.0.0-20190423024810-112230192c58/go.mod h1:RxMgew5VJxzue5/jJTE5uejpjVlOe/izrB70Jof72aM=
-golang.org/x/sync v0.0.0-20220722155255-886fb9371eb4/go.mod h1:RxMgew5VJxzue5/jJTE5uejpjVlOe/izrB70Jof72aM=
 golang.org/x/sync v0.1.0 h1:wsuoTGHzEhffawBOhz5CYhcrV4IdKZbEyZjBMuTp12o=
 golang.org/x/sync v0.1.0/go.mod h1:RxMgew5VJxzue5/jJTE5uejpjVlOe/izrB70Jof72aM=
-golang.org/x/sys v0.0.0-20190215142949-d0b11bdaac8a/go.mod h1:STP8DvDyc/dI5b8T5hshtkjS+E42TnysNCUPdjciGhY=
-golang.org/x/sys v0.0.0-20201119102817-f84b799fce68/go.mod h1:h1NjWce9XRLGQEsW7wpKNCjG9DtNlClVuFLEZdDNbEs=
-golang.org/x/sys v0.0.0-20210615035016-665e8c7367d1/go.mod h1:oPkhp1MJrh7nUepCBck5+mAzfO9JrbApNNgaTdGDITg=
-golang.org/x/sys v0.0.0-20220520151302-bc2c85ada10a/go.mod h1:oPkhp1MJrh7nUepCBck5+mAzfO9JrbApNNgaTdGDITg=
-golang.org/x/sys v0.0.0-20220722155257-8c9f86f7a55f/go.mod h1:oPkhp1MJrh7nUepCBck5+mAzfO9JrbApNNgaTdGDITg=
 golang.org/x/sys v0.2.0 h1:ljd4t30dBnAvMZaQCevtY0xLLD0A+bRZXbgLMLU1F/A=
 golang.org/x/sys v0.2.0/go.mod h1:oPkhp1MJrh7nUepCBck5+mAzfO9JrbApNNgaTdGDITg=
-golang.org/x/term v0.0.0-20201126162022-7de9c90e9dd1/go.mod h1:bj7SfCRtBDWHUb9snDiAeCFNEtKQo2Wmx5Cou7ajbmo=
-golang.org/x/term v0.0.0-20210927222741-03fcf44c2211/go.mod h1:jbD1KX2456YbFQfuXm/mYQcufACuNUgVhRMnK/tPxf8=
-golang.org/x/term v0.2.0/go.mod h1:TVmDHMZPmdnySmBfhjOoOdhjzdE1h4u1VwSiw2l1Nuc=
-golang.org/x/text v0.3.0/go.mod h1:NqM8EUOU14njkJ3fqMW+pc6Ldnwhi/IjpwHt7yyuwOQ=
-golang.org/x/text v0.3.3/go.mod h1:5Zoc/QRtKVWzQhOtBMvqHzDpF6irO9z98xDceosuGiQ=
-golang.org/x/text v0.3.7/go.mod h1:u+2+/6zg+i71rQMx5EYifcz6MCKuco9NR6JIITiCfzQ=
-golang.org/x/text v0.4.0/go.mod h1:mrYo+phRRbMaCq/xk9113O4dZlRixOauAjOtrjsXDZ8=
-golang.org/x/tools v0.0.0-20180917221912-90fa682c2a6e/go.mod h1:n7NCudcB/nEzxVGmLbDWY5pfWTLqBcC2KZ6jyYvM4mQ=
-golang.org/x/tools v0.0.0-20191119224855-298f0cb1881e/go.mod h1:b+2E5dAYhXwXZwtnZ6UAqBI28+e2cm9otk0dWdXHAEo=
-golang.org/x/tools v0.1.12/go.mod h1:hNGJHUnrk76NpqgfD5Aqm5Crs+Hm0VOH/i9J2+nxYbc=
 golang.org/x/tools v0.3.0 h1:SrNbZl6ECOS1qFzgTdQfWXZM9XBkiA6tkFrH9YSTPHM=
 golang.org/x/tools v0.3.0/go.mod h1:/rWhSS2+zyEVwoJf8YAX6L2f0ntZ7Kn/mGgAWcipA5k=
-golang.org/x/xerrors v0.0.0-20190717185122-a985d3407aa7/go.mod h1:I/5z698sn9Ka8TeJc9MKroUUfqBBauWjQqLJ2OPfmY0=

msg.go

@@ -1065,8 +1065,8 @@ func (dns *Msg) CopyTo(r1 *Msg) *Msg {
 	r1.Compress = dns.Compress
 
 	if len(dns.Question) > 0 {
-		r1.Question = make([]Question, len(dns.Question))
-		copy(r1.Question, dns.Question) // TODO(miek): Question is an immutable value, ok to do a shallow-copy
+		// TODO(miek): Question is an immutable value, ok to do a shallow-copy
+		r1.Question = cloneSlice(dns.Question)
 	}
 
 	rrArr := make([]RR, len(dns.Answer)+len(dns.Ns)+len(dns.Extra))

msg_helpers.go

@@ -625,7 +625,7 @@ func unpackDataSVCB(msg []byte, off int) ([]SVCBKeyValue, int, error) {
 }
 
 func packDataSVCB(pairs []SVCBKeyValue, msg []byte, off int) (int, error) {
-	pairs = append([]SVCBKeyValue(nil), pairs...)
+	pairs = cloneSlice(pairs)
 	sort.Slice(pairs, func(i, j int) bool {
 		return pairs[i].Key() < pairs[j].Key()
 	})

svcb.go

@@ -289,7 +289,7 @@ func (s *SVCBMandatory) String() string {
 }
 
 func (s *SVCBMandatory) pack() ([]byte, error) {
-	codes := append([]SVCBKey(nil), s.Code...)
+	codes := cloneSlice(s.Code)
 	sort.Slice(codes, func(i, j int) bool {
 		return codes[i] < codes[j]
 	})
@@ -328,9 +328,7 @@ func (s *SVCBMandatory) len() int {
 }
 
 func (s *SVCBMandatory) copy() SVCBKeyValue {
-	return &SVCBMandatory{
-		append([]SVCBKey(nil), s.Code...),
-	}
+	return &SVCBMandatory{cloneSlice(s.Code)}
 }
 
 // SVCBAlpn pair is used to list supported connection protocols.
@@ -481,9 +479,7 @@ func (s *SVCBAlpn) len() int {
 }
 
 func (s *SVCBAlpn) copy() SVCBKeyValue {
-	return &SVCBAlpn{
-		append([]string(nil), s.Alpn...),
-	}
+	return &SVCBAlpn{cloneSlice(s.Alpn)}
 }
 
 // SVCBNoDefaultAlpn pair signifies no support for default connection protocols.
@@ -595,6 +591,7 @@ func (s *SVCBIPv4Hint) unpack(b []byte) error {
 	if len(b) == 0 || len(b)%4 != 0 {
 		return errors.New("dns: svcbipv4hint: ipv4 address byte array length is not a multiple of 4")
 	}
+	b = cloneSlice(b)
 	x := make([]net.IP, 0, len(b)/4)
 	for i := 0; i < len(b); i += 4 {
 		x = append(x, net.IP(b[i:i+4]))
@@ -635,12 +632,9 @@ func (s *SVCBIPv4Hint) parse(b string) error {
 func (s *SVCBIPv4Hint) copy() SVCBKeyValue {
 	hint := make([]net.IP, len(s.Hint))
 	for i, ip := range s.Hint {
-		hint[i] = copyIP(ip)
-	}
-
-	return &SVCBIPv4Hint{
-		Hint: hint,
+		hint[i] = cloneSlice(ip)
 	}
+	return &SVCBIPv4Hint{Hint: hint}
 }
 
 // SVCBECHConfig pair contains the ECHConfig structure defined in draft-ietf-tls-esni [RFC xxxx].
@@ -660,19 +654,18 @@ func (s *SVCBECHConfig) String() string { return toBase64(s.ECH) }
 func (s *SVCBECHConfig) len() int       { return len(s.ECH) }
 
 func (s *SVCBECHConfig) pack() ([]byte, error) {
-	return append([]byte(nil), s.ECH...), nil
+	return cloneSlice(s.ECH), nil
 }
 
 func (s *SVCBECHConfig) copy() SVCBKeyValue {
-	return &SVCBECHConfig{
-		append([]byte(nil), s.ECH...),
-	}
+	return &SVCBECHConfig{cloneSlice(s.ECH)}
 }
 
 func (s *SVCBECHConfig) unpack(b []byte) error {
-	s.ECH = append([]byte(nil), b...)
+	s.ECH = cloneSlice(b)
 	return nil
 }
+
 func (s *SVCBECHConfig) parse(b string) error {
 	x, err := fromBase64([]byte(b))
 	if err != nil {
@@ -715,6 +708,7 @@ func (s *SVCBIPv6Hint) unpack(b []byte) error {
 	if len(b) == 0 || len(b)%16 != 0 {
 		return errors.New("dns: svcbipv6hint: ipv6 address byte array length not a multiple of 16")
 	}
+	b = cloneSlice(b)
 	x := make([]net.IP, 0, len(b)/16)
 	for i := 0; i < len(b); i += 16 {
 		ip := net.IP(b[i : i+16])
@@ -758,12 +752,9 @@ func (s *SVCBIPv6Hint) parse(b string) error {
 func (s *SVCBIPv6Hint) copy() SVCBKeyValue {
 	hint := make([]net.IP, len(s.Hint))
 	for i, ip := range s.Hint {
-		hint[i] = copyIP(ip)
-	}
-
-	return &SVCBIPv6Hint{
-		Hint: hint,
+		hint[i] = cloneSlice(ip)
 	}
+	return &SVCBIPv6Hint{Hint: hint}
 }
 
 // SVCBDoHPath pair is used to indicate the URI template that the
@@ -831,11 +822,11 @@ type SVCBLocal struct {
 
 func (s *SVCBLocal) Key() SVCBKey          { return s.KeyCode }
 func (s *SVCBLocal) String() string        { return svcbParamToStr(s.Data) }
-func (s *SVCBLocal) pack() ([]byte, error) { return append([]byte(nil), s.Data...), nil }
+func (s *SVCBLocal) pack() ([]byte, error) { return cloneSlice(s.Data), nil }
 func (s *SVCBLocal) len() int              { return len(s.Data) }
 
 func (s *SVCBLocal) unpack(b []byte) error {
-	s.Data = append([]byte(nil), b...)
+	s.Data = cloneSlice(b)
 	return nil
 }
 
@@ -849,9 +840,7 @@ func (s *SVCBLocal) parse(b string) error {
 }
 
 func (s *SVCBLocal) copy() SVCBKeyValue {
-	return &SVCBLocal{s.KeyCode,
-		append([]byte(nil), s.Data...),
-	}
+	return &SVCBLocal{s.KeyCode, cloneSlice(s.Data)}
 }
 
 func (rr *SVCB) String() string {
@@ -867,8 +856,8 @@ func (rr *SVCB) String() string {
 // areSVCBPairArraysEqual checks if SVCBKeyValue arrays are equal after sorting their
 // copies. arrA and arrB have equal lengths, otherwise zduplicate.go wouldn't call this function.
 func areSVCBPairArraysEqual(a []SVCBKeyValue, b []SVCBKeyValue) bool {
-	a = append([]SVCBKeyValue(nil), a...)
-	b = append([]SVCBKeyValue(nil), b...)
+	a = cloneSlice(a)
+	b = cloneSlice(b)
 	sort.Slice(a, func(i, j int) bool { return a[i].Key() < a[j].Key() })
 	sort.Slice(b, func(i, j int) bool { return b[i].Key() < b[j].Key() })
 	for i, e := range a {

types.go

@@ -1599,21 +1599,19 @@ func euiToString(eui uint64, bits int) (hex string) {
 	return
 }
 
-// copyIP returns a copy of ip.
-func copyIP(ip net.IP) net.IP {
-	p := make(net.IP, len(ip))
-	copy(p, ip)
-	return p
+// cloneSlice returns a shallow copy of s.
+func cloneSlice[E any, S ~[]E](s S) S {
+	if s == nil {
+		return nil
+	}
+	return append(S(nil), s...)
 }
 
 // copyNet returns a copy of a subnet.
 func copyNet(n net.IPNet) net.IPNet {
-	m := make(net.IPMask, len(n.Mask))
-	copy(m, n.Mask)
-
 	return net.IPNet{
-		IP:   copyIP(n.IP),
-		Mask: m,
+		IP:   cloneSlice(n.IP),
+		Mask: cloneSlice(n.Mask),
 	}
 }