dns/edns.go

497 lines
13 KiB
Go

// EDNS0
//
// EDNS0 is an extension mechanism for the DNS defined in RFC 2671 and updated
// by RFC 6891. It defines an new RR type, the OPT RR, which is then completely
// abused.
// Basic use pattern for creating an (empty) OPT RR:
//
// o := new(dns.OPT)
// o.Hdr.Name = "." // MUST be the root zone, per definition.
// o.Hdr.Rrtype = dns.TypeOPT
//
// The rdata of an OPT RR consists out of a slice of EDNS0 (RFC 6891)
// interfaces. Currently only a few have been standardized: EDNS0_NSID
// (RFC 5001) and EDNS0_SUBNET (draft-vandergaast-edns-client-subnet-02). Note
// that these options may be combined in an OPT RR.
// Basic use pattern for a server to check if (and which) options are set:
//
// // o is a dns.OPT
// for _, s := range o.Option {
// switch e := s.(type) {
// case *dns.EDNS0_NSID:
// // do stuff with e.Nsid
// case *dns.EDNS0_SUBNET:
// // access e.Family, e.Address, etc.
// }
// }
package dns
import (
"encoding/hex"
"errors"
"net"
"strconv"
)
// EDNS0 Option codes.
const (
EDNS0LLQ = 0x1 // long lived queries: http://tools.ietf.org/html/draft-sekar-dns-llq-01
EDNS0UL = 0x2 // update lease draft: http://files.dns-sd.org/draft-sekar-dns-ul.txt
EDNS0NSID = 0x3 // nsid (RFC5001)
EDNS0DAU = 0x5 // DNSSEC Algorithm Understood
EDNS0DHU = 0x6 // DS Hash Understood
EDNS0N3U = 0x7 // NSEC3 Hash Understood
EDNS0SUBNET = 0x8 // client-subnet (RFC6891)
EDNS0EXPIRE = 0x9 // EDNS0 expire
EDNS0SUBNETDRAFT = 0x50fa // Don't use! Use EDNS0SUBNET
_DO = 1 << 7 // dnssec ok
)
type OPT struct {
Hdr RR_Header
Option []EDNS0 `dns:"opt"`
}
func (rr *OPT) Header() *RR_Header {
return &rr.Hdr
}
func (rr *OPT) String() string {
s := "\n;; OPT PSEUDOSECTION:\n; EDNS: version " + strconv.Itoa(int(rr.Version())) + "; "
if rr.Do() {
s += "flags: do; "
} else {
s += "flags: ; "
}
s += "udp: " + strconv.Itoa(int(rr.UDPSize()))
for _, o := range rr.Option {
switch o.(type) {
case *EDNS0_NSID:
s += "\n; NSID: " + o.String()
h, e := o.pack()
var r string
if e == nil {
for _, c := range h {
r += "(" + string(c) + ")"
}
s += " " + r
}
case *EDNS0_SUBNET:
s += "\n; SUBNET: " + o.String()
if o.(*EDNS0_SUBNET).DraftOption {
s += " (draft)"
}
case *EDNS0_UL:
s += "\n; UPDATE LEASE: " + o.String()
case *EDNS0_LLQ:
s += "\n; LONG LIVED QUERIES: " + o.String()
case *EDNS0_DAU:
s += "\n; DNSSEC ALGORITHM UNDERSTOOD: " + o.String()
case *EDNS0_DHU:
s += "\n; DS HASH UNDERSTOOD: " + o.String()
case *EDNS0_N3U:
s += "\n; NSEC3 HASH UNDERSTOOD: " + o.String()
}
}
return s
}
func (rr *OPT) len() int {
l := rr.Hdr.len()
for i := 0; i < len(rr.Option); i++ {
lo, _ := rr.Option[i].pack()
l += 2 + len(lo)
}
return l
}
func (rr *OPT) copy() RR {
return &OPT{*rr.Hdr.copyHeader(), rr.Option}
}
// return the old value -> delete SetVersion
// Version returns the EDNS version used. Only zero is defined.
func (rr *OPT) Version() uint8 {
return uint8(rr.Hdr.Ttl & 0x00FF00FFFF)
}
// SetVersion sets the version of EDNS. This is usually zero.
func (rr *OPT) SetVersion(v uint8) {
rr.Hdr.Ttl = rr.Hdr.Ttl&0xFF00FFFF | uint32(v)
}
// UDPSize returns the UDP buffer size.
func (rr *OPT) UDPSize() uint16 {
return rr.Hdr.Class
}
// SetUDPSize sets the UDP buffer size.
func (rr *OPT) SetUDPSize(size uint16) {
rr.Hdr.Class = size
}
// Do returns the value of the DO (DNSSEC OK) bit.
func (rr *OPT) Do() bool {
return byte(rr.Hdr.Ttl>>8)&_DO == _DO
}
// SetDo sets the DO (DNSSEC OK) bit.
func (rr *OPT) SetDo() {
b1 := byte(rr.Hdr.Ttl >> 24)
b2 := byte(rr.Hdr.Ttl >> 16)
b3 := byte(rr.Hdr.Ttl >> 8)
b4 := byte(rr.Hdr.Ttl)
b3 |= _DO // Set it
rr.Hdr.Ttl = uint32(b1)<<24 | uint32(b2)<<16 | uint32(b3)<<8 | uint32(b4)
}
// EDNS0 defines an EDNS0 Option. An OPT RR can have multiple options appended to
// it.
type EDNS0 interface {
// Option returns the option code for the option.
Option() uint16
// pack returns the bytes of the option data.
pack() ([]byte, error)
// unpack sets the data as found in the buffer. Is also sets
// the length of the slice as the length of the option data.
unpack([]byte) error
// String returns the string representation of the option.
String() string
}
// The nsid EDNS0 option is used to retrieve a nameserver
// identifier. When sending a request Nsid must be set to the empty string
// The identifier is an opaque string encoded as hex.
// Basic use pattern for creating an nsid option:
//
// o := new(dns.OPT)
// o.Hdr.Name = "."
// o.Hdr.Rrtype = dns.TypeOPT
// e := new(dns.EDNS0_NSID)
// e.Code = dns.EDNS0NSID
// e.Nsid = "AA"
// o.Option = append(o.Option, e)
type EDNS0_NSID struct {
Code uint16 // Always EDNS0NSID
Nsid string // This string needs to be hex encoded
}
func (e *EDNS0_NSID) pack() ([]byte, error) {
h, err := hex.DecodeString(e.Nsid)
if err != nil {
return nil, err
}
return h, nil
}
func (e *EDNS0_NSID) Option() uint16 { return EDNS0NSID }
func (e *EDNS0_NSID) unpack(b []byte) error { e.Nsid = hex.EncodeToString(b); return nil }
func (e *EDNS0_NSID) String() string { return string(e.Nsid) }
// The subnet EDNS0 option is used to give the remote nameserver
// an idea of where the client lives. It can then give back a different
// answer depending on the location or network topology.
// Basic use pattern for creating an subnet option:
//
// o := new(dns.OPT)
// o.Hdr.Name = "."
// o.Hdr.Rrtype = dns.TypeOPT
// e := new(dns.EDNS0_SUBNET)
// e.Code = dns.EDNS0SUBNET
// e.Family = 1 // 1 for IPv4 source address, 2 for IPv6
// e.NetMask = 32 // 32 for IPV4, 128 for IPv6
// e.SourceScope = 0
// e.Address = net.ParseIP("127.0.0.1").To4() // for IPv4
// // e.Address = net.ParseIP("2001:7b8:32a::2") // for IPV6
// o.Option = append(o.Option, e)
type EDNS0_SUBNET struct {
Code uint16 // Always EDNS0SUBNET
Family uint16 // 1 for IP, 2 for IP6
SourceNetmask uint8
SourceScope uint8
Address net.IP
DraftOption bool // Set to true if using the old (0x50fa) option code
}
func (e *EDNS0_SUBNET) Option() uint16 {
if e.DraftOption {
return EDNS0SUBNETDRAFT
}
return EDNS0SUBNET
}
func (e *EDNS0_SUBNET) pack() ([]byte, error) {
b := make([]byte, 4)
b[0], b[1] = packUint16(e.Family)
b[2] = e.SourceNetmask
b[3] = e.SourceScope
switch e.Family {
case 1:
if e.SourceNetmask > net.IPv4len*8 {
return nil, errors.New("dns: bad netmask")
}
ip := make([]byte, net.IPv4len)
a := e.Address.To4().Mask(net.CIDRMask(int(e.SourceNetmask), net.IPv4len*8))
for i := 0; i < net.IPv4len; i++ {
if i+1 > len(e.Address) {
break
}
ip[i] = a[i]
}
needLength := e.SourceNetmask / 8
if e.SourceNetmask%8 > 0 {
needLength++
}
ip = ip[:needLength]
b = append(b, ip...)
case 2:
if e.SourceNetmask > net.IPv6len*8 {
return nil, errors.New("dns: bad netmask")
}
ip := make([]byte, net.IPv6len)
a := e.Address.Mask(net.CIDRMask(int(e.SourceNetmask), net.IPv6len*8))
for i := 0; i < net.IPv6len; i++ {
if i+1 > len(e.Address) {
break
}
ip[i] = a[i]
}
needLength := e.SourceNetmask / 8
if e.SourceNetmask%8 > 0 {
needLength++
}
ip = ip[:needLength]
b = append(b, ip...)
default:
return nil, errors.New("dns: bad address family")
}
return b, nil
}
func (e *EDNS0_SUBNET) unpack(b []byte) error {
lb := len(b)
if lb < 4 {
return ErrBuf
}
e.Family, _ = unpackUint16(b, 0)
e.SourceNetmask = b[2]
e.SourceScope = b[3]
switch e.Family {
case 1:
addr := make([]byte, 4)
for i := 0; i < int(e.SourceNetmask/8); i++ {
if 4+i > len(b) {
return ErrBuf
}
addr[i] = b[4+i]
}
e.Address = net.IPv4(addr[0], addr[1], addr[2], addr[3])
case 2:
addr := make([]byte, 16)
for i := 0; i < int(e.SourceNetmask/8); i++ {
if 4+i > len(b) {
return ErrBuf
}
addr[i] = b[4+i]
}
e.Address = net.IP{addr[0], addr[1], addr[2], addr[3], addr[4],
addr[5], addr[6], addr[7], addr[8], addr[9], addr[10],
addr[11], addr[12], addr[13], addr[14], addr[15]}
}
return nil
}
func (e *EDNS0_SUBNET) String() (s string) {
if e.Address == nil {
s = "<nil>"
} else if e.Address.To4() != nil {
s = e.Address.String()
} else {
s = "[" + e.Address.String() + "]"
}
s += "/" + strconv.Itoa(int(e.SourceNetmask)) + "/" + strconv.Itoa(int(e.SourceScope))
return
}
// The UL (Update Lease) EDNS0 (draft RFC) option is used to tell the server to set
// an expiration on an update RR. This is helpful for clients that cannot clean
// up after themselves. This is a draft RFC and more information can be found at
// http://files.dns-sd.org/draft-sekar-dns-ul.txt
//
// o := new(dns.OPT)
// o.Hdr.Name = "."
// o.Hdr.Rrtype = dns.TypeOPT
// e := new(dns.EDNS0_UL)
// e.Code = dns.EDNS0UL
// e.Lease = 120 // in seconds
// o.Option = append(o.Option, e)
type EDNS0_UL struct {
Code uint16 // Always EDNS0UL
Lease uint32
}
func (e *EDNS0_UL) Option() uint16 { return EDNS0UL }
func (e *EDNS0_UL) String() string { return strconv.FormatUint(uint64(e.Lease), 10) }
// Copied: http://golang.org/src/pkg/net/dnsmsg.go
func (e *EDNS0_UL) pack() ([]byte, error) {
b := make([]byte, 4)
b[0] = byte(e.Lease >> 24)
b[1] = byte(e.Lease >> 16)
b[2] = byte(e.Lease >> 8)
b[3] = byte(e.Lease)
return b, nil
}
func (e *EDNS0_UL) unpack(b []byte) error {
if len(b) < 4 {
return ErrBuf
}
e.Lease = uint32(b[0])<<24 | uint32(b[1])<<16 | uint32(b[2])<<8 | uint32(b[3])
return nil
}
// Long Lived Queries: http://tools.ietf.org/html/draft-sekar-dns-llq-01
// Implemented for completeness, as the EDNS0 type code is assigned.
type EDNS0_LLQ struct {
Code uint16 // Always EDNS0LLQ
Version uint16
Opcode uint16
Error uint16
Id uint64
LeaseLife uint32
}
func (e *EDNS0_LLQ) Option() uint16 { return EDNS0LLQ }
func (e *EDNS0_LLQ) pack() ([]byte, error) {
b := make([]byte, 18)
b[0], b[1] = packUint16(e.Version)
b[2], b[3] = packUint16(e.Opcode)
b[4], b[5] = packUint16(e.Error)
b[6] = byte(e.Id >> 56)
b[7] = byte(e.Id >> 48)
b[8] = byte(e.Id >> 40)
b[9] = byte(e.Id >> 32)
b[10] = byte(e.Id >> 24)
b[11] = byte(e.Id >> 16)
b[12] = byte(e.Id >> 8)
b[13] = byte(e.Id)
b[14] = byte(e.LeaseLife >> 24)
b[15] = byte(e.LeaseLife >> 16)
b[16] = byte(e.LeaseLife >> 8)
b[17] = byte(e.LeaseLife)
return b, nil
}
func (e *EDNS0_LLQ) unpack(b []byte) error {
if len(b) < 18 {
return ErrBuf
}
e.Version, _ = unpackUint16(b, 0)
e.Opcode, _ = unpackUint16(b, 2)
e.Error, _ = unpackUint16(b, 4)
e.Id = uint64(b[6])<<56 | uint64(b[6+1])<<48 | uint64(b[6+2])<<40 |
uint64(b[6+3])<<32 | uint64(b[6+4])<<24 | uint64(b[6+5])<<16 | uint64(b[6+6])<<8 | uint64(b[6+7])
e.LeaseLife = uint32(b[14])<<24 | uint32(b[14+1])<<16 | uint32(b[14+2])<<8 | uint32(b[14+3])
return nil
}
func (e *EDNS0_LLQ) String() string {
s := strconv.FormatUint(uint64(e.Version), 10) + " " + strconv.FormatUint(uint64(e.Opcode), 10) +
" " + strconv.FormatUint(uint64(e.Error), 10) + " " + strconv.FormatUint(uint64(e.Id), 10) +
" " + strconv.FormatUint(uint64(e.LeaseLife), 10)
return s
}
type EDNS0_DAU struct {
Code uint16 // Always EDNS0DAU
AlgCode []uint8
}
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) String() string {
s := ""
for i := 0; i < len(e.AlgCode); i++ {
if a, ok := AlgorithmToString[e.AlgCode[i]]; ok {
s += " " + a
} else {
s += " " + strconv.Itoa(int(e.AlgCode[i]))
}
}
return s
}
type EDNS0_DHU struct {
Code uint16 // Always EDNS0DHU
AlgCode []uint8
}
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) String() string {
s := ""
for i := 0; i < len(e.AlgCode); i++ {
if a, ok := HashToString[e.AlgCode[i]]; ok {
s += " " + a
} else {
s += " " + strconv.Itoa(int(e.AlgCode[i]))
}
}
return s
}
type EDNS0_N3U struct {
Code uint16 // Always EDNS0N3U
AlgCode []uint8
}
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) String() string {
// Re-use the hash map
s := ""
for i := 0; i < len(e.AlgCode); i++ {
if a, ok := HashToString[e.AlgCode[i]]; ok {
s += " " + a
} else {
s += " " + strconv.Itoa(int(e.AlgCode[i]))
}
}
return s
}
type EDNS0_EXPIRE struct {
Code uint16 // Always EDNS0EXPIRE
Expire uint32
}
func (e *EDNS0_EXPIRE) Option() uint16 { return EDNS0EXPIRE }
func (e *EDNS0_EXPIRE) String() string { return strconv.FormatUint(uint64(e.Expire), 10) }
func (e *EDNS0_EXPIRE) pack() ([]byte, error) {
b := make([]byte, 4)
b[0] = byte(e.Expire >> 24)
b[1] = byte(e.Expire >> 16)
b[2] = byte(e.Expire >> 8)
b[3] = byte(e.Expire)
return b, nil
}
func (e *EDNS0_EXPIRE) unpack(b []byte) error {
if len(b) < 4 {
return ErrBuf
}
e.Expire = uint32(b[0])<<24 | uint32(b[1])<<16 | uint32(b[2])<<8 | uint32(b[3])
return nil
}