1461 lines
40 KiB
Go
1461 lines
40 KiB
Go
// Copyright 2009 The Go Authors. All rights reserved.
|
|
// Use of this source code is governed by a BSD-style
|
|
// license that can be found in the LICENSE file.
|
|
// Extensions of the original work are copyright (c) 2011 Miek Gieben
|
|
|
|
// DNS packet assembly, see RFC 1035. Converting from - Unpack() -
|
|
// and to - Pack() - wire format.
|
|
// All the packers and unpackers take a (msg []byte, off int)
|
|
// and return (off1 int, ok bool). If they return ok==false, they
|
|
// also return off1==len(msg), so that the next unpacker will
|
|
// also fail. This lets us avoid checks of ok until the end of a
|
|
// packing sequence.
|
|
|
|
package dns
|
|
|
|
import (
|
|
"encoding/base32"
|
|
"encoding/base64"
|
|
"encoding/hex"
|
|
"fmt"
|
|
"math/rand"
|
|
"net"
|
|
"reflect"
|
|
"strconv"
|
|
"time"
|
|
)
|
|
|
|
const maxCompressionOffset = 2 << 13 // We have 14 bits for the compression pointer
|
|
|
|
var (
|
|
ErrFqdn error = &Error{err: "domain must be fully qualified"}
|
|
ErrId error = &Error{err: "id mismatch"}
|
|
ErrRdata error = &Error{err: "bad rdata"}
|
|
ErrBuf error = &Error{err: "buffer size too small"}
|
|
ErrShortRead error = &Error{err: "short read"}
|
|
ErrConn error = &Error{err: "conn holds both UDP and TCP connection"}
|
|
ErrConnEmpty error = &Error{err: "conn has no connection"}
|
|
ErrServ error = &Error{err: "no servers could be reached"}
|
|
ErrKey error = &Error{err: "bad key"}
|
|
ErrPrivKey error = &Error{err: "bad private key"}
|
|
ErrKeySize error = &Error{err: "bad key size"}
|
|
ErrKeyAlg error = &Error{err: "bad key algorithm"}
|
|
ErrAlg error = &Error{err: "bad algorithm"}
|
|
ErrTime error = &Error{err: "bad time"}
|
|
ErrNoSig error = &Error{err: "no signature found"}
|
|
ErrSig error = &Error{err: "bad signature"}
|
|
ErrSecret error = &Error{err: "no secrets defined"}
|
|
ErrSigGen error = &Error{err: "bad signature generation"}
|
|
ErrAuth error = &Error{err: "bad authentication"}
|
|
ErrSoa error = &Error{err: "no SOA"}
|
|
ErrRRset error = &Error{err: "bad rrset"}
|
|
)
|
|
|
|
// A manually-unpacked version of (id, bits).
|
|
// This is in its own struct for easy printing.
|
|
type MsgHdr struct {
|
|
Id uint16
|
|
Response bool
|
|
Opcode int
|
|
Authoritative bool
|
|
Truncated bool
|
|
RecursionDesired bool
|
|
RecursionAvailable bool
|
|
Zero bool
|
|
AuthenticatedData bool
|
|
CheckingDisabled bool
|
|
Rcode int
|
|
}
|
|
|
|
// The layout of a DNS message.
|
|
type Msg struct {
|
|
MsgHdr
|
|
Compress bool `json:"-"` // If true, the message will be compressed when converted to wire format.
|
|
Question []Question // Holds the RR(s) of the question section.
|
|
Answer []RR // Holds the RR(s) of the answer section.
|
|
Ns []RR // Holds the RR(s) of the authority section.
|
|
Extra []RR // Holds the RR(s) of the additional section.
|
|
}
|
|
|
|
// Map of strings for each RR wire type.
|
|
var TypeToString = map[uint16]string{
|
|
TypeCNAME: "CNAME",
|
|
TypeHINFO: "HINFO",
|
|
TypeTLSA: "TLSA",
|
|
TypeMB: "MB",
|
|
TypeMG: "MG",
|
|
TypeRP: "RP",
|
|
TypeMD: "MD",
|
|
TypeMF: "MF",
|
|
TypeMINFO: "MINFO",
|
|
TypeMR: "MR",
|
|
TypeMX: "MX",
|
|
TypeWKS: "WKS",
|
|
TypeNS: "NS",
|
|
TypeNULL: "NULL",
|
|
TypeAFSDB: "AFSDB",
|
|
TypeX25: "X25",
|
|
TypeISDN: "ISDN",
|
|
TypePTR: "PTR",
|
|
TypeRT: "RT",
|
|
TypeSOA: "SOA",
|
|
TypeTXT: "TXT",
|
|
TypeSRV: "SRV",
|
|
TypeATMA: "ATMA",
|
|
TypeNAPTR: "NAPTR",
|
|
TypeKX: "KX",
|
|
TypeCERT: "CERT",
|
|
TypeDNAME: "DNAME",
|
|
TypeA: "A",
|
|
TypeAAAA: "AAAA",
|
|
TypeLOC: "LOC",
|
|
TypeOPT: "OPT",
|
|
TypeDS: "DS",
|
|
TypeDHCID: "DHCID",
|
|
TypeHIP: "HIP",
|
|
TypeNINFO: "NINFO",
|
|
TypeRKEY: "RKEY",
|
|
TypeCDS: "CDS",
|
|
TypeCAA: "CAA",
|
|
TypeIPSECKEY: "IPSECKEY",
|
|
TypeSSHFP: "SSHFP",
|
|
TypeRRSIG: "RRSIG",
|
|
TypeNSEC: "NSEC",
|
|
TypeDNSKEY: "DNSKEY",
|
|
TypeNSEC3: "NSEC3",
|
|
TypeNSEC3PARAM: "NSEC3PARAM",
|
|
TypeTALINK: "TALINK",
|
|
TypeSPF: "SPF",
|
|
TypeNID: "NID",
|
|
TypeL32: "L32",
|
|
TypeL64: "L64",
|
|
TypeLP: "LP",
|
|
TypeUINFO: "UINFO",
|
|
TypeUID: "UID",
|
|
TypeGID: "GID",
|
|
TypeUNSPEC: "UNSPEC",
|
|
TypeEUI48: "EUI48",
|
|
TypeEUI64: "EUI64",
|
|
TypeTKEY: "TKEY", // Meta RR
|
|
TypeTSIG: "TSIG", // Meta RR
|
|
TypeAXFR: "AXFR", // Meta RR
|
|
TypeIXFR: "IXFR", // Meta RR
|
|
TypeANY: "ANY", // Meta RR
|
|
TypeURI: "URI",
|
|
TypeTA: "TA",
|
|
TypeDLV: "DLV",
|
|
}
|
|
|
|
// Reverse, needed for string parsing.
|
|
var StringToType = reverseInt16(TypeToString)
|
|
var StringToClass = reverseInt16(ClassToString)
|
|
|
|
// Map of opcodes strings.
|
|
var StringToOpcode = reverseInt(OpcodeToString)
|
|
|
|
// Map of rcodes strings.
|
|
var StringToRcode = reverseInt(RcodeToString)
|
|
|
|
// Map of strings for each CLASS wire type.
|
|
var ClassToString = map[uint16]string{
|
|
ClassINET: "IN",
|
|
ClassCSNET: "CS",
|
|
ClassCHAOS: "CH",
|
|
ClassHESIOD: "HS",
|
|
ClassNONE: "NONE",
|
|
ClassANY: "ANY",
|
|
}
|
|
|
|
// Map of strings for opcodes.
|
|
var OpcodeToString = map[int]string{
|
|
OpcodeQuery: "QUERY",
|
|
OpcodeIQuery: "IQUERY",
|
|
OpcodeStatus: "STATUS",
|
|
OpcodeNotify: "NOTIFY",
|
|
OpcodeUpdate: "UPDATE",
|
|
}
|
|
|
|
// Map of strings for rcodes.
|
|
var RcodeToString = map[int]string{
|
|
RcodeSuccess: "NOERROR",
|
|
RcodeFormatError: "FORMERR",
|
|
RcodeServerFailure: "SERVFAIL",
|
|
RcodeNameError: "NXDOMAIN",
|
|
RcodeNotImplemented: "NOTIMPL",
|
|
RcodeRefused: "REFUSED",
|
|
RcodeYXDomain: "YXDOMAIN", // From RFC 2136
|
|
RcodeYXRrset: "YXRRSET",
|
|
RcodeNXRrset: "NXRRSET",
|
|
RcodeNotAuth: "NOTAUTH",
|
|
RcodeNotZone: "NOTZONE",
|
|
RcodeBadSig: "BADSIG", // Also known as RcodeBadVers, see RFC 6891
|
|
// RcodeBadVers: "BADVERS",
|
|
RcodeBadKey: "BADKEY",
|
|
RcodeBadTime: "BADTIME",
|
|
RcodeBadMode: "BADMODE",
|
|
RcodeBadName: "BADNAME",
|
|
RcodeBadAlg: "BADALG",
|
|
RcodeBadTrunc: "BADTRUNC",
|
|
}
|
|
|
|
// Rather than write the usual handful of routines to pack and
|
|
// unpack every message that can appear on the wire, we use
|
|
// reflection to write a generic pack/unpack for structs and then
|
|
// use it. Thus, if in the future we need to define new message
|
|
// structs, no new pack/unpack/printing code needs to be written.
|
|
|
|
// Domain names are a sequence of counted strings
|
|
// split at the dots. They end with a zero-length string.
|
|
|
|
// PackDomainName packs a domain name s into msg[off:].
|
|
// If compression is wanted compress must be true and the compression
|
|
// map needs to hold a mapping between domain names and offsets
|
|
// pointing into msg[].
|
|
func PackDomainName(s string, msg []byte, off int, compression map[string]int, compress bool) (off1 int, err error) {
|
|
lenmsg := len(msg)
|
|
ls := len(s)
|
|
// If not fully qualified, error out
|
|
if ls == 0 || s[ls-1] != '.' {
|
|
return lenmsg, ErrFqdn
|
|
}
|
|
// Each dot ends a segment of the name.
|
|
// We trade each dot byte for a length byte.
|
|
// Except for escaped dots (\.), which are normal dots.
|
|
// There is also a trailing zero.
|
|
|
|
// Compression
|
|
nameoffset := -1
|
|
pointer := -1
|
|
// Emit sequence of counted strings, chopping at dots.
|
|
begin := 0
|
|
bs := []byte(s)
|
|
for i := 0; i < ls; i++ {
|
|
if bs[i] == '\\' {
|
|
for j := i; j < ls-1; j++ {
|
|
bs[j] = bs[j+1]
|
|
}
|
|
ls--
|
|
if off+1 > lenmsg {
|
|
return lenmsg, ErrBuf
|
|
}
|
|
// check for \DDD
|
|
if i+2 < ls && bs[i] >= '0' && bs[i] <= '9' &&
|
|
bs[i+1] >= '0' && bs[i+1] <= '9' &&
|
|
bs[i+2] >= '0' && bs[i+2] <= '9' {
|
|
bs[i] = byte((bs[i]-'0')*100 + (bs[i+1]-'0')*10 + (bs[i+2] - '0'))
|
|
for j := i + 1; j < ls-2; j++ {
|
|
bs[j] = bs[j+2]
|
|
}
|
|
ls -= 2
|
|
}
|
|
continue
|
|
}
|
|
|
|
if bs[i] == '.' {
|
|
if i-begin >= 1<<6 { // top two bits of length must be clear
|
|
return lenmsg, ErrRdata
|
|
}
|
|
// off can already (we're in a loop) be bigger than len(msg)
|
|
// this happens when a name isn't fully qualified
|
|
if off+1 > lenmsg {
|
|
return lenmsg, ErrBuf
|
|
}
|
|
msg[off] = byte(i - begin)
|
|
offset := off
|
|
off++
|
|
for j := begin; j < i; j++ {
|
|
if off+1 > lenmsg {
|
|
return lenmsg, ErrBuf
|
|
}
|
|
msg[off] = bs[j]
|
|
off++
|
|
}
|
|
// Dont try to compress '.'
|
|
if compression != nil && string(bs[begin:]) != "." {
|
|
if p, ok := compression[string(bs[begin:])]; !ok {
|
|
// Only offsets smaller than this can be used.
|
|
if offset < maxCompressionOffset {
|
|
compression[string(bs[begin:])] = offset
|
|
}
|
|
} else {
|
|
// The first hit is the longest matching dname
|
|
// keep the pointer offset we get back and store
|
|
// the offset of the current name, because that's
|
|
// where we need to insert the pointer later
|
|
|
|
// If compress is true, we're allowed to compress this dname
|
|
if pointer == -1 && compress {
|
|
pointer = p // Where to point to
|
|
nameoffset = offset // Where to point from
|
|
break
|
|
}
|
|
}
|
|
}
|
|
begin = i + 1
|
|
}
|
|
}
|
|
// Root label is special
|
|
if len(bs) == 1 && bs[0] == '.' {
|
|
return off, nil
|
|
}
|
|
// If we did compression and we find something at the pointer here
|
|
if pointer != -1 {
|
|
// We have two bytes (14 bits) to put the pointer in
|
|
msg[nameoffset], msg[nameoffset+1] = packUint16(uint16(pointer ^ 0xC000))
|
|
off = nameoffset + 1
|
|
goto End
|
|
}
|
|
msg[off] = 0
|
|
End:
|
|
off++
|
|
return off, nil
|
|
}
|
|
|
|
// Unpack a domain name.
|
|
// In addition to the simple sequences of counted strings above,
|
|
// domain names are allowed to refer to strings elsewhere in the
|
|
// packet, to avoid repeating common suffixes when returning
|
|
// many entries in a single domain. The pointers are marked
|
|
// by a length byte with the top two bits set. Ignoring those
|
|
// two bits, that byte and the next give a 14 bit offset from msg[0]
|
|
// where we should pick up the trail.
|
|
// Note that if we jump elsewhere in the packet,
|
|
// we return off1 == the offset after the first pointer we found,
|
|
// which is where the next record will start.
|
|
// In theory, the pointers are only allowed to jump backward.
|
|
// We let them jump anywhere and stop jumping after a while.
|
|
|
|
// UnpackDomainName unpacks a domain name into a string.
|
|
func UnpackDomainName(msg []byte, off int) (s string, off1 int, err error) {
|
|
s = ""
|
|
lenmsg := len(msg)
|
|
ptr := 0 // number of pointers followed
|
|
Loop:
|
|
for {
|
|
if off >= lenmsg {
|
|
return "", lenmsg, ErrBuf
|
|
}
|
|
c := int(msg[off])
|
|
off++
|
|
switch c & 0xC0 {
|
|
case 0x00:
|
|
if c == 0x00 {
|
|
// end of name
|
|
if s == "" {
|
|
return ".", off, nil
|
|
}
|
|
break Loop
|
|
}
|
|
// literal string
|
|
if off+c > lenmsg {
|
|
return "", lenmsg, ErrBuf
|
|
}
|
|
for j := off; j < off+c; j++ {
|
|
switch {
|
|
case msg[j] == '.': // literal dots
|
|
s += "\\."
|
|
case msg[j] < 32: // unprintable use \DDD
|
|
fallthrough
|
|
case msg[j] >= 127:
|
|
s += fmt.Sprintf("\\%03d", msg[j])
|
|
default:
|
|
s += string(msg[j])
|
|
}
|
|
}
|
|
s += "."
|
|
off += c
|
|
case 0xC0:
|
|
// pointer to somewhere else in msg.
|
|
// remember location after first ptr,
|
|
// since that's how many bytes we consumed.
|
|
// also, don't follow too many pointers --
|
|
// maybe there's a loop.
|
|
if off >= lenmsg {
|
|
return "", lenmsg, ErrBuf
|
|
}
|
|
c1 := msg[off]
|
|
off++
|
|
if ptr == 0 {
|
|
off1 = off
|
|
}
|
|
if ptr++; ptr > 10 {
|
|
return "", lenmsg, &Error{err: "too many compression pointers"}
|
|
}
|
|
off = (c^0xC0)<<8 | int(c1)
|
|
default:
|
|
// 0x80 and 0x40 are reserved
|
|
return "", lenmsg, ErrRdata
|
|
}
|
|
}
|
|
if ptr == 0 {
|
|
off1 = off
|
|
}
|
|
return s, off1, nil
|
|
}
|
|
|
|
// Pack a reflect.StructValue into msg. Struct members can only be uint8, uint16, uint32, string,
|
|
// slices and other (often anonymous) structs.
|
|
func packStructValue(val reflect.Value, msg []byte, off int, compression map[string]int, compress bool) (off1 int, err error) {
|
|
lenmsg := len(msg)
|
|
for i := 0; i < val.NumField(); i++ {
|
|
switch fv := val.Field(i); fv.Kind() {
|
|
default:
|
|
return lenmsg, &Error{err: "bad kind packing"}
|
|
case reflect.Slice:
|
|
switch val.Type().Field(i).Tag {
|
|
default:
|
|
return lenmsg, &Error{"bad tag packing slice: " + val.Type().Field(i).Tag.Get("dns")}
|
|
case `dns:"domain-name"`:
|
|
for j := 0; j < val.Field(i).Len(); j++ {
|
|
element := val.Field(i).Index(j).String()
|
|
off, err = PackDomainName(element, msg, off, compression, false && compress)
|
|
if err != nil {
|
|
return lenmsg, err
|
|
}
|
|
}
|
|
case `dns:"txt"`:
|
|
for j := 0; j < val.Field(i).Len(); j++ {
|
|
element := val.Field(i).Index(j).String()
|
|
// Counted string: 1 byte length.
|
|
if len(element) > 255 || off+1+len(element) > lenmsg {
|
|
return lenmsg, &Error{err: "overflow packing txt"}
|
|
}
|
|
msg[off] = byte(len(element))
|
|
off++
|
|
for i := 0; i < len(element); i++ {
|
|
msg[off+i] = element[i]
|
|
}
|
|
off += len(element)
|
|
}
|
|
case `dns:"opt"`: // edns
|
|
for j := 0; j < val.Field(i).Len(); j++ {
|
|
element := val.Field(i).Index(j).Interface()
|
|
b, e := element.(EDNS0).pack()
|
|
if e != nil {
|
|
return lenmsg, &Error{err: "overflow packing opt"}
|
|
}
|
|
// Option code
|
|
msg[off], msg[off+1] = packUint16(element.(EDNS0).Option())
|
|
// Length
|
|
msg[off+2], msg[off+3] = packUint16(uint16(len(b)))
|
|
off += 4
|
|
// Actual data
|
|
copy(msg[off:off+len(b)], b)
|
|
off += len(b)
|
|
}
|
|
case `dns:"a"`:
|
|
// It must be a slice of 4, even if it is 16, we encode
|
|
// only the first 4
|
|
if off+net.IPv4len > lenmsg {
|
|
return lenmsg, &Error{err: "overflow packing a"}
|
|
}
|
|
switch fv.Len() {
|
|
case net.IPv6len:
|
|
msg[off] = byte(fv.Index(12).Uint())
|
|
msg[off+1] = byte(fv.Index(13).Uint())
|
|
msg[off+2] = byte(fv.Index(14).Uint())
|
|
msg[off+3] = byte(fv.Index(15).Uint())
|
|
off += net.IPv4len
|
|
case net.IPv4len:
|
|
msg[off] = byte(fv.Index(0).Uint())
|
|
msg[off+1] = byte(fv.Index(1).Uint())
|
|
msg[off+2] = byte(fv.Index(2).Uint())
|
|
msg[off+3] = byte(fv.Index(3).Uint())
|
|
off += net.IPv4len
|
|
case 0:
|
|
// Allowed, for dynamic updates
|
|
default:
|
|
return lenmsg, &Error{err: "overflow packing a"}
|
|
}
|
|
case `dns:"aaaa"`:
|
|
// fv.Len TODO(mg) dynamisc updates?
|
|
if fv.Len() > net.IPv6len || off+fv.Len() > lenmsg {
|
|
return lenmsg, &Error{err: "overflow packing aaaa"}
|
|
}
|
|
for j := 0; j < net.IPv6len; j++ {
|
|
msg[off] = byte(fv.Index(j).Uint())
|
|
off++
|
|
}
|
|
case `dns:"wks"`:
|
|
if val.Field(i).Len() == 0 {
|
|
break
|
|
}
|
|
var bitmapbyte uint16
|
|
for j := 0; j < val.Field(i).Len(); j++ {
|
|
serv := uint16((fv.Index(j).Uint()))
|
|
bitmapbyte = uint16(serv / 8)
|
|
if int(bitmapbyte) > lenmsg {
|
|
return lenmsg, &Error{err: "overflow packing wks"}
|
|
}
|
|
bit := uint16(serv) - bitmapbyte*8
|
|
msg[bitmapbyte] = byte(1 << (7 - bit))
|
|
}
|
|
off += int(bitmapbyte)
|
|
case `dns:"nsec"`: // NSEC/NSEC3
|
|
// This is the uint16 type bitmap
|
|
if val.Field(i).Len() == 0 {
|
|
// Do absolutely nothing
|
|
break
|
|
}
|
|
|
|
lastwindow := uint16(0)
|
|
length := uint16(0)
|
|
if off+2 > lenmsg {
|
|
return lenmsg, &Error{err: "overflow packing nsecx"}
|
|
}
|
|
for j := 0; j < val.Field(i).Len(); j++ {
|
|
t := uint16((fv.Index(j).Uint()))
|
|
window := uint16(t / 256)
|
|
if lastwindow != window {
|
|
// New window, jump to the new offset
|
|
off += int(length) + 3
|
|
if off > lenmsg {
|
|
return lenmsg, &Error{err: "overflow packing nsecx bitmap"}
|
|
}
|
|
}
|
|
length = (t - window*256) / 8
|
|
bit := t - (window * 256) - (length * 8)
|
|
if off+2+int(length) > lenmsg {
|
|
return lenmsg, &Error{err: "overflow packing nsecx bitmap"}
|
|
}
|
|
|
|
// Setting the window #
|
|
msg[off] = byte(window)
|
|
// Setting the octets length
|
|
msg[off+1] = byte(length + 1)
|
|
// Setting the bit value for the type in the right octet
|
|
msg[off+2+int(length)] |= byte(1 << (7 - bit))
|
|
lastwindow = window
|
|
}
|
|
off += 2 + int(length)
|
|
off++
|
|
if off > lenmsg {
|
|
return lenmsg, &Error{err: "overflow packing nsecx bitmap"}
|
|
}
|
|
}
|
|
case reflect.Struct:
|
|
off, err = packStructValue(fv, msg, off, compression, compress)
|
|
if err != nil {
|
|
return lenmsg, err
|
|
}
|
|
case reflect.Uint8:
|
|
if off+1 > lenmsg {
|
|
return lenmsg, &Error{err: "overflow packing uint8"}
|
|
}
|
|
msg[off] = byte(fv.Uint())
|
|
off++
|
|
case reflect.Uint16:
|
|
if off+2 > lenmsg {
|
|
return lenmsg, &Error{err: "overflow packing uint16"}
|
|
}
|
|
i := fv.Uint()
|
|
msg[off] = byte(i >> 8)
|
|
msg[off+1] = byte(i)
|
|
off += 2
|
|
case reflect.Uint32:
|
|
if off+4 > lenmsg {
|
|
return lenmsg, &Error{err: "overflow packing uint32"}
|
|
}
|
|
i := fv.Uint()
|
|
msg[off] = byte(i >> 24)
|
|
msg[off+1] = byte(i >> 16)
|
|
msg[off+2] = byte(i >> 8)
|
|
msg[off+3] = byte(i)
|
|
off += 4
|
|
case reflect.Uint64:
|
|
switch val.Type().Field(i).Tag {
|
|
default:
|
|
if off+8 > lenmsg {
|
|
return lenmsg, &Error{err: "overflow packing uint64"}
|
|
}
|
|
i := fv.Uint()
|
|
msg[off] = byte(i >> 56)
|
|
msg[off+1] = byte(i >> 48)
|
|
msg[off+2] = byte(i >> 40)
|
|
msg[off+3] = byte(i >> 32)
|
|
msg[off+4] = byte(i >> 24)
|
|
msg[off+5] = byte(i >> 16)
|
|
msg[off+6] = byte(i >> 8)
|
|
msg[off+7] = byte(i)
|
|
off += 8
|
|
case `dns:"uint48"`:
|
|
// Used in TSIG, where it stops at 48 bits, so we discard the upper 16
|
|
if off+6 > lenmsg {
|
|
return lenmsg, &Error{err: "overflow packing uint64 as uint48"}
|
|
}
|
|
i := fv.Uint()
|
|
msg[off] = byte(i >> 40)
|
|
msg[off+1] = byte(i >> 32)
|
|
msg[off+2] = byte(i >> 24)
|
|
msg[off+3] = byte(i >> 16)
|
|
msg[off+4] = byte(i >> 8)
|
|
msg[off+5] = byte(i)
|
|
off += 6
|
|
}
|
|
case reflect.String:
|
|
// There are multiple string encodings.
|
|
// The tag distinguishes ordinary strings from domain names.
|
|
s := fv.String()
|
|
switch val.Type().Field(i).Tag {
|
|
default:
|
|
return lenmsg, &Error{"bad tag packing string: " + val.Type().Field(i).Tag.Get("dns")}
|
|
case `dns:"base64"`:
|
|
b64, err := packBase64([]byte(s))
|
|
if err != nil {
|
|
return lenmsg, &Error{err: "overflow packing base64"}
|
|
}
|
|
copy(msg[off:off+len(b64)], b64)
|
|
off += len(b64)
|
|
case `dns:"domain-name"`:
|
|
if off, err = PackDomainName(s, msg, off, compression, false && compress); err != nil {
|
|
return lenmsg, err
|
|
}
|
|
case `dns:"cdomain-name"`:
|
|
if off, err = PackDomainName(s, msg, off, compression, true && compress); err != nil {
|
|
return lenmsg, err
|
|
}
|
|
case `dns:"size-base32"`:
|
|
// This is purely for NSEC3 atm, the previous byte must
|
|
// holds the length of the encoded string. As NSEC3
|
|
// is only defined to SHA1, the hashlength is 20 (160 bits)
|
|
msg[off-1] = 20
|
|
fallthrough
|
|
case `dns:"base32"`:
|
|
b32, err := packBase32([]byte(s))
|
|
if err != nil {
|
|
return lenmsg, &Error{err: "overflow packing base32"}
|
|
}
|
|
copy(msg[off:off+len(b32)], b32)
|
|
off += len(b32)
|
|
case `dns:"size-hex"`:
|
|
fallthrough
|
|
case `dns:"hex"`:
|
|
// There is no length encoded here
|
|
h, e := hex.DecodeString(s)
|
|
if e != nil {
|
|
return lenmsg, &Error{err: "overflow packing hex"}
|
|
}
|
|
if off+hex.DecodedLen(len(s)) > lenmsg {
|
|
return lenmsg, &Error{err: "overflow packing hex"}
|
|
}
|
|
copy(msg[off:off+hex.DecodedLen(len(s))], h)
|
|
off += hex.DecodedLen(len(s))
|
|
case `dns:"size"`:
|
|
// the size is already encoded in the RR, we can safely use the
|
|
// length of string. String is RAW (not encoded in hex, nor base64)
|
|
copy(msg[off:off+len(s)], s)
|
|
off += len(s)
|
|
case `dns:"txt"`:
|
|
fallthrough
|
|
case "":
|
|
// Counted string: 1 byte length.
|
|
if len(s) > 255 || off+1+len(s) > lenmsg {
|
|
return lenmsg, &Error{err: "overflow packing string"}
|
|
}
|
|
msg[off] = byte(len(s))
|
|
off++
|
|
for i := 0; i < len(s); i++ {
|
|
msg[off+i] = s[i]
|
|
}
|
|
off += len(s)
|
|
}
|
|
}
|
|
}
|
|
return off, nil
|
|
}
|
|
|
|
func structValue(any interface{}) reflect.Value {
|
|
return reflect.ValueOf(any).Elem()
|
|
}
|
|
|
|
// PackStruct packs any structure to wire format.
|
|
func PackStruct(any interface{}, msg []byte, off int) (off1 int, err error) {
|
|
off, err = packStructValue(structValue(any), msg, off, nil, false)
|
|
return off, err
|
|
}
|
|
|
|
func packStructCompress(any interface{}, msg []byte, off int, compression map[string]int, compress bool) (off1 int, err error) {
|
|
off, err = packStructValue(structValue(any), msg, off, compression, compress)
|
|
return off, err
|
|
}
|
|
|
|
// Unpack a reflect.StructValue from msg.
|
|
// Same restrictions as packStructValue.
|
|
func unpackStructValue(val reflect.Value, msg []byte, off int) (off1 int, err error) {
|
|
var rdstart int
|
|
lenmsg := len(msg)
|
|
for i := 0; i < val.NumField(); i++ {
|
|
switch fv := val.Field(i); fv.Kind() {
|
|
default:
|
|
return lenmsg, &Error{err: "bad kind unpacking"}
|
|
case reflect.Slice:
|
|
switch val.Type().Field(i).Tag {
|
|
default:
|
|
return lenmsg, &Error{"bad tag unpacking slice: " + val.Type().Field(i).Tag.Get("dns")}
|
|
case `dns:"domain-name"`:
|
|
// HIP record slice of name (or none)
|
|
servers := make([]string, 0)
|
|
var s string
|
|
for off < lenmsg {
|
|
s, off, err = UnpackDomainName(msg, off)
|
|
if err != nil {
|
|
return lenmsg, err
|
|
}
|
|
servers = append(servers, s)
|
|
}
|
|
fv.Set(reflect.ValueOf(servers))
|
|
case `dns:"txt"`:
|
|
txt := make([]string, 0)
|
|
rdlength := off + int(val.FieldByName("Hdr").FieldByName("Rdlength").Uint())
|
|
Txts:
|
|
l := int(msg[off])
|
|
if off+l+1 > lenmsg {
|
|
return lenmsg, &Error{err: "overflow unpacking txt"}
|
|
}
|
|
txt = append(txt, string(msg[off+1:off+l+1]))
|
|
off += l + 1
|
|
if off < rdlength {
|
|
// More
|
|
goto Txts
|
|
}
|
|
fv.Set(reflect.ValueOf(txt))
|
|
case `dns:"opt"`: // edns0
|
|
rdlength := int(val.FieldByName("Hdr").FieldByName("Rdlength").Uint())
|
|
endrr := off + rdlength
|
|
if rdlength == 0 {
|
|
// This is an EDNS0 (OPT Record) with no rdata
|
|
// We can safely return here.
|
|
break
|
|
}
|
|
edns := make([]EDNS0, 0)
|
|
Option:
|
|
code := uint16(0)
|
|
if off+2 > lenmsg {
|
|
return lenmsg, &Error{err: "overflow unpacking opt"}
|
|
}
|
|
code, off = unpackUint16(msg, off)
|
|
optlen, off1 := unpackUint16(msg, off)
|
|
if off1+int(optlen) > off+rdlength {
|
|
return lenmsg, &Error{err: "overflow unpacking opt"}
|
|
}
|
|
switch code {
|
|
case EDNS0NSID:
|
|
e := new(EDNS0_NSID)
|
|
e.unpack(msg[off1 : off1+int(optlen)])
|
|
edns = append(edns, e)
|
|
off = off1 + int(optlen)
|
|
case EDNS0SUBNET:
|
|
e := new(EDNS0_SUBNET)
|
|
e.unpack(msg[off1 : off1+int(optlen)])
|
|
edns = append(edns, e)
|
|
off = off1 + int(optlen)
|
|
case EDNS0UL:
|
|
e := new(EDNS0_UL)
|
|
e.unpack(msg[off1 : off1+int(optlen)])
|
|
edns = append(edns, e)
|
|
off = off1 + int(optlen)
|
|
case EDNS0LLQ:
|
|
e := new(EDNS0_LLQ)
|
|
e.unpack(msg[off1 : off1+int(optlen)])
|
|
edns = append(edns, e)
|
|
off = off1 + int(optlen)
|
|
case EDNS0DAU:
|
|
e := new(EDNS0_DAU)
|
|
e.unpack(msg[off1 : off1+int(optlen)])
|
|
edns = append(edns, e)
|
|
off = off1 + int(optlen)
|
|
case EDNS0DHU:
|
|
e := new(EDNS0_DHU)
|
|
e.unpack(msg[off1 : off1+int(optlen)])
|
|
edns = append(edns, e)
|
|
off = off1 + int(optlen)
|
|
case EDNS0N3U:
|
|
e := new(EDNS0_N3U)
|
|
e.unpack(msg[off1 : off1+int(optlen)])
|
|
edns = append(edns, e)
|
|
off = off1 + int(optlen)
|
|
default:
|
|
// do nothing?
|
|
off = off1 + int(optlen)
|
|
}
|
|
if off < endrr {
|
|
goto Option
|
|
}
|
|
fv.Set(reflect.ValueOf(edns))
|
|
case `dns:"a"`:
|
|
if off+net.IPv4len > lenmsg {
|
|
return lenmsg, &Error{err: "overflow unpacking a"}
|
|
}
|
|
fv.Set(reflect.ValueOf(net.IPv4(msg[off], msg[off+1], msg[off+2], msg[off+3])))
|
|
off += net.IPv4len
|
|
case `dns:"aaaa"`:
|
|
if off+net.IPv6len > lenmsg {
|
|
return lenmsg, &Error{err: "overflow unpacking aaaa"}
|
|
}
|
|
fv.Set(reflect.ValueOf(net.IP{msg[off], msg[off+1], msg[off+2], msg[off+3], msg[off+4],
|
|
msg[off+5], msg[off+6], msg[off+7], msg[off+8], msg[off+9], msg[off+10],
|
|
msg[off+11], msg[off+12], msg[off+13], msg[off+14], msg[off+15]}))
|
|
off += net.IPv6len
|
|
case `dns:"wks"`:
|
|
// Rest of the record is the bitmap
|
|
rdlength := int(val.FieldByName("Hdr").FieldByName("Rdlength").Uint())
|
|
endrr := rdstart + rdlength
|
|
serv := make([]uint16, 0)
|
|
j := 0
|
|
for off < endrr {
|
|
b := msg[off]
|
|
// Check the bits one by one, and set the type
|
|
if b&0x80 == 0x80 {
|
|
serv = append(serv, uint16(j*8+0))
|
|
}
|
|
if b&0x40 == 0x40 {
|
|
serv = append(serv, uint16(j*8+1))
|
|
}
|
|
if b&0x20 == 0x20 {
|
|
serv = append(serv, uint16(j*8+2))
|
|
}
|
|
if b&0x10 == 0x10 {
|
|
serv = append(serv, uint16(j*8+3))
|
|
}
|
|
if b&0x8 == 0x8 {
|
|
serv = append(serv, uint16(j*8+4))
|
|
}
|
|
if b&0x4 == 0x4 {
|
|
serv = append(serv, uint16(j*8+5))
|
|
}
|
|
if b&0x2 == 0x2 {
|
|
serv = append(serv, uint16(j*8+6))
|
|
}
|
|
if b&0x1 == 0x1 {
|
|
serv = append(serv, uint16(j*8+7))
|
|
}
|
|
j++
|
|
off++
|
|
}
|
|
fv.Set(reflect.ValueOf(serv))
|
|
case `dns:"nsec"`: // NSEC/NSEC3
|
|
// Rest of the record is the type bitmap
|
|
rdlength := int(val.FieldByName("Hdr").FieldByName("Rdlength").Uint())
|
|
endrr := rdstart + rdlength
|
|
|
|
if off+2 > lenmsg {
|
|
return lenmsg, &Error{err: "overflow unpacking nsecx"}
|
|
}
|
|
nsec := make([]uint16, 0)
|
|
length := 0
|
|
window := 0
|
|
for off+2 < endrr {
|
|
window = int(msg[off])
|
|
length = int(msg[off+1])
|
|
//println("off, windows, length, end", off, window, length, endrr)
|
|
if length == 0 {
|
|
// A length window of zero is strange. If there
|
|
// the window should not have been specified. Bail out
|
|
// println("dns: length == 0 when unpacking NSEC")
|
|
return lenmsg, ErrRdata
|
|
}
|
|
if length > 32 {
|
|
return lenmsg, ErrRdata
|
|
}
|
|
|
|
// Walk the bytes in the window - and check the bit settings...
|
|
off += 2
|
|
for j := 0; j < length; j++ {
|
|
b := msg[off+j]
|
|
// Check the bits one by one, and set the type
|
|
if b&0x80 == 0x80 {
|
|
nsec = append(nsec, uint16(window*256+j*8+0))
|
|
}
|
|
if b&0x40 == 0x40 {
|
|
nsec = append(nsec, uint16(window*256+j*8+1))
|
|
}
|
|
if b&0x20 == 0x20 {
|
|
nsec = append(nsec, uint16(window*256+j*8+2))
|
|
}
|
|
if b&0x10 == 0x10 {
|
|
nsec = append(nsec, uint16(window*256+j*8+3))
|
|
}
|
|
if b&0x8 == 0x8 {
|
|
nsec = append(nsec, uint16(window*256+j*8+4))
|
|
}
|
|
if b&0x4 == 0x4 {
|
|
nsec = append(nsec, uint16(window*256+j*8+5))
|
|
}
|
|
if b&0x2 == 0x2 {
|
|
nsec = append(nsec, uint16(window*256+j*8+6))
|
|
}
|
|
if b&0x1 == 0x1 {
|
|
nsec = append(nsec, uint16(window*256+j*8+7))
|
|
}
|
|
}
|
|
off += length
|
|
}
|
|
fv.Set(reflect.ValueOf(nsec))
|
|
}
|
|
case reflect.Struct:
|
|
off, err = unpackStructValue(fv, msg, off)
|
|
if err != nil {
|
|
return lenmsg, err
|
|
}
|
|
if val.Type().Field(i).Name == "Hdr" {
|
|
rdstart = off
|
|
}
|
|
case reflect.Uint8:
|
|
if off+1 > lenmsg {
|
|
return lenmsg, &Error{err: "overflow unpacking uint8"}
|
|
}
|
|
fv.SetUint(uint64(uint8(msg[off])))
|
|
off++
|
|
case reflect.Uint16:
|
|
var i uint16
|
|
if off+2 > lenmsg {
|
|
return lenmsg, &Error{err: "overflow unpacking uint16"}
|
|
}
|
|
i, off = unpackUint16(msg, off)
|
|
fv.SetUint(uint64(i))
|
|
case reflect.Uint32:
|
|
if off+4 > lenmsg {
|
|
return lenmsg, &Error{err: "overflow unpacking uint32"}
|
|
}
|
|
fv.SetUint(uint64(uint32(msg[off])<<24 | uint32(msg[off+1])<<16 | uint32(msg[off+2])<<8 | uint32(msg[off+3])))
|
|
off += 4
|
|
case reflect.Uint64:
|
|
switch val.Type().Field(i).Tag {
|
|
default:
|
|
if off+8 > lenmsg {
|
|
return lenmsg, &Error{err: "overflow unpacking uint64"}
|
|
}
|
|
fv.SetUint(uint64(uint64(msg[off])<<56 | uint64(msg[off+1])<<48 | uint64(msg[off+2])<<40 |
|
|
uint64(msg[off+3])<<32 | uint64(msg[off+4])<<24 | uint64(msg[off+5])<<16 | uint64(msg[off+6])<<8 | uint64(msg[off+7])))
|
|
off += 8
|
|
case `dns:"uint48"`:
|
|
// Used in TSIG where the last 48 bits are occupied, so for now, assume a uint48 (6 bytes)
|
|
if off+6 > lenmsg {
|
|
return lenmsg, &Error{err: "overflow unpacking uint64 as uint48"}
|
|
}
|
|
fv.SetUint(uint64(uint64(msg[off])<<40 | uint64(msg[off+1])<<32 | uint64(msg[off+2])<<24 | uint64(msg[off+3])<<16 |
|
|
uint64(msg[off+4])<<8 | uint64(msg[off+5])))
|
|
off += 6
|
|
}
|
|
case reflect.String:
|
|
var s string
|
|
switch val.Type().Field(i).Tag {
|
|
default:
|
|
return lenmsg, &Error{"bad tag unpacking string: " + val.Type().Field(i).Tag.Get("dns")}
|
|
case `dns:"hex"`:
|
|
// Rest of the RR is hex encoded, network order an issue here?
|
|
rdlength := int(val.FieldByName("Hdr").FieldByName("Rdlength").Uint())
|
|
endrr := rdstart + rdlength
|
|
if endrr > lenmsg {
|
|
return lenmsg, &Error{err: "overflow unpacking hex"}
|
|
}
|
|
s = hex.EncodeToString(msg[off:endrr])
|
|
off = endrr
|
|
case `dns:"base64"`:
|
|
// Rest of the RR is base64 encoded value
|
|
rdlength := int(val.FieldByName("Hdr").FieldByName("Rdlength").Uint())
|
|
endrr := rdstart + rdlength
|
|
if endrr > lenmsg {
|
|
return lenmsg, &Error{err: "overflow unpacking base64"}
|
|
}
|
|
s = unpackBase64(msg[off:endrr])
|
|
off = endrr
|
|
case `dns:"cdomain-name"`:
|
|
fallthrough
|
|
case `dns:"domain-name"`:
|
|
s, off, err = UnpackDomainName(msg, off)
|
|
if err != nil {
|
|
return lenmsg, err
|
|
}
|
|
case `dns:"size-base32"`:
|
|
var size int
|
|
switch val.Type().Name() {
|
|
case "NSEC3":
|
|
switch val.Type().Field(i).Name {
|
|
case "NextDomain":
|
|
name := val.FieldByName("HashLength")
|
|
size = int(name.Uint())
|
|
}
|
|
}
|
|
if off+size > lenmsg {
|
|
return lenmsg, &Error{err: "overflow unpacking base32"}
|
|
}
|
|
s = unpackBase32(msg[off : off+size])
|
|
off += size
|
|
case `dns:"size-hex"`:
|
|
// a "size" string, but it must be encoded in hex in the string
|
|
var size int
|
|
switch val.Type().Name() {
|
|
case "NSEC3":
|
|
switch val.Type().Field(i).Name {
|
|
case "Salt":
|
|
name := val.FieldByName("SaltLength")
|
|
size = int(name.Uint())
|
|
case "NextDomain":
|
|
name := val.FieldByName("HashLength")
|
|
size = int(name.Uint())
|
|
}
|
|
case "TSIG":
|
|
switch val.Type().Field(i).Name {
|
|
case "MAC":
|
|
name := val.FieldByName("MACSize")
|
|
size = int(name.Uint())
|
|
case "OtherData":
|
|
name := val.FieldByName("OtherLen")
|
|
size = int(name.Uint())
|
|
}
|
|
}
|
|
if off+size > lenmsg {
|
|
return lenmsg, &Error{err: "overflow unpacking hex"}
|
|
}
|
|
s = hex.EncodeToString(msg[off : off+size])
|
|
off += size
|
|
case `dns:"txt"`:
|
|
// 1 txt piece
|
|
rdlength := int(val.FieldByName("Hdr").FieldByName("Rdlength").Uint())
|
|
Txt:
|
|
if off >= lenmsg || off+1+int(msg[off]) > lenmsg {
|
|
return lenmsg, &Error{err: "overflow unpacking txt"}
|
|
}
|
|
n := int(msg[off])
|
|
off++
|
|
for i := 0; i < n; i++ {
|
|
s += string(msg[off+i])
|
|
}
|
|
off += n
|
|
if off < rdlength {
|
|
// More to
|
|
goto Txt
|
|
}
|
|
case "":
|
|
if off >= lenmsg || off+1+int(msg[off]) > lenmsg {
|
|
return lenmsg, &Error{err: "overflow unpacking string"}
|
|
}
|
|
n := int(msg[off])
|
|
off++
|
|
for i := 0; i < n; i++ {
|
|
s += string(msg[off+i])
|
|
}
|
|
off += n
|
|
}
|
|
fv.SetString(s)
|
|
}
|
|
}
|
|
return off, nil
|
|
}
|
|
|
|
// Helper function for unpacking
|
|
func unpackUint16(msg []byte, off int) (v uint16, off1 int) {
|
|
v = uint16(msg[off])<<8 | uint16(msg[off+1])
|
|
off1 = off + 2
|
|
return
|
|
}
|
|
|
|
// UnpackStruct unpacks a binary message from offset off to the interface
|
|
// value given.
|
|
func UnpackStruct(any interface{}, msg []byte, off int) (off1 int, err error) {
|
|
off, err = unpackStructValue(structValue(any), msg, off)
|
|
return off, err
|
|
}
|
|
|
|
func unpackBase32(b []byte) string {
|
|
b32 := make([]byte, base32.HexEncoding.EncodedLen(len(b)))
|
|
base32.HexEncoding.Encode(b32, b)
|
|
return string(b32)
|
|
}
|
|
|
|
func unpackBase64(b []byte) string {
|
|
b64 := make([]byte, base64.StdEncoding.EncodedLen(len(b)))
|
|
base64.StdEncoding.Encode(b64, b)
|
|
return string(b64)
|
|
}
|
|
|
|
// Helper function for packing
|
|
func packUint16(i uint16) (byte, byte) {
|
|
return byte(i >> 8), byte(i)
|
|
}
|
|
|
|
func packBase64(s []byte) ([]byte, error) {
|
|
b64len := base64.StdEncoding.DecodedLen(len(s))
|
|
buf := make([]byte, b64len)
|
|
n, err := base64.StdEncoding.Decode(buf, []byte(s))
|
|
if err != nil {
|
|
return nil, err
|
|
}
|
|
buf = buf[:n]
|
|
return buf, nil
|
|
}
|
|
|
|
// Helper function for packing, mostly used in dnssec.go
|
|
func packBase32(s []byte) ([]byte, error) {
|
|
b32len := base32.HexEncoding.DecodedLen(len(s))
|
|
buf := make([]byte, b32len)
|
|
n, err := base32.HexEncoding.Decode(buf, []byte(s))
|
|
if err != nil {
|
|
return nil, err
|
|
}
|
|
buf = buf[:n]
|
|
return buf, nil
|
|
}
|
|
|
|
// Resource record packer, pack rr into msg[off:]. See PackDomainName for documentation
|
|
// about the compression.
|
|
func PackRR(rr RR, msg []byte, off int, compression map[string]int, compress bool) (off1 int, err error) {
|
|
if rr == nil {
|
|
return len(msg), &Error{err: "nil rr"}
|
|
}
|
|
|
|
off1, err = packStructCompress(rr, msg, off, compression, compress)
|
|
if err != nil {
|
|
return len(msg), err
|
|
}
|
|
rawSetRdlength(msg, off, off1)
|
|
return off1, nil
|
|
}
|
|
|
|
// Resource record unpacker, unpack msg[off:] into an RR.
|
|
func UnpackRR(msg []byte, off int) (rr RR, off1 int, err error) {
|
|
// unpack just the header, to find the rr type and length
|
|
var h RR_Header
|
|
off0 := off
|
|
if off, err = UnpackStruct(&h, msg, off); err != nil {
|
|
return nil, len(msg), err
|
|
}
|
|
end := off + int(h.Rdlength)
|
|
// make an rr of that type and re-unpack.
|
|
mk, known := rr_mk[h.Rrtype]
|
|
if !known {
|
|
rr = new(RFC3597)
|
|
} else {
|
|
rr = mk()
|
|
}
|
|
off, err = UnpackStruct(rr, msg, off0)
|
|
if off != end {
|
|
return &h, end, &Error{err: "bad rdlength"}
|
|
}
|
|
return rr, off, err
|
|
}
|
|
|
|
// Reverse a map
|
|
func reverseInt8(m map[uint8]string) map[string]uint8 {
|
|
n := make(map[string]uint8)
|
|
for u, s := range m {
|
|
n[s] = u
|
|
}
|
|
return n
|
|
}
|
|
|
|
func reverseInt16(m map[uint16]string) map[string]uint16 {
|
|
n := make(map[string]uint16)
|
|
for u, s := range m {
|
|
n[s] = u
|
|
}
|
|
return n
|
|
}
|
|
|
|
func reverseInt(m map[int]string) map[string]int {
|
|
n := make(map[string]int)
|
|
for u, s := range m {
|
|
n[s] = u
|
|
}
|
|
return n
|
|
}
|
|
|
|
// Convert a MsgHdr to a string, with dig-like headers:
|
|
//
|
|
//;; opcode: QUERY, status: NOERROR, id: 48404
|
|
//
|
|
//;; flags: qr aa rd ra;
|
|
func (h *MsgHdr) String() string {
|
|
if h == nil {
|
|
return "<nil> MsgHdr"
|
|
}
|
|
|
|
s := ";; opcode: " + OpcodeToString[h.Opcode]
|
|
s += ", status: " + RcodeToString[h.Rcode]
|
|
s += ", id: " + strconv.Itoa(int(h.Id)) + "\n"
|
|
|
|
s += ";; flags:"
|
|
if h.Response {
|
|
s += " qr"
|
|
}
|
|
if h.Authoritative {
|
|
s += " aa"
|
|
}
|
|
if h.Truncated {
|
|
s += " tc"
|
|
}
|
|
if h.RecursionDesired {
|
|
s += " rd"
|
|
}
|
|
if h.RecursionAvailable {
|
|
s += " ra"
|
|
}
|
|
if h.Zero { // Hmm
|
|
s += " z"
|
|
}
|
|
if h.AuthenticatedData {
|
|
s += " ad"
|
|
}
|
|
if h.CheckingDisabled {
|
|
s += " cd"
|
|
}
|
|
|
|
s += ";"
|
|
return s
|
|
}
|
|
|
|
// Pack packs a Msg: it is converted to to wire format.
|
|
// If the dns.Compress is true the message will be in compressed wire format.
|
|
func (dns *Msg) Pack() (msg []byte, err error) {
|
|
var dh Header
|
|
var compression map[string]int
|
|
if dns.Compress {
|
|
compression = make(map[string]int) // Compression pointer mappings
|
|
} else {
|
|
compression = nil
|
|
}
|
|
|
|
// Convert convenient Msg into wire-like Header.
|
|
dh.Id = dns.Id
|
|
dh.Bits = uint16(dns.Opcode)<<11 | uint16(dns.Rcode)
|
|
if dns.Response {
|
|
dh.Bits |= _QR
|
|
}
|
|
if dns.Authoritative {
|
|
dh.Bits |= _AA
|
|
}
|
|
if dns.Truncated {
|
|
dh.Bits |= _TC
|
|
}
|
|
if dns.RecursionDesired {
|
|
dh.Bits |= _RD
|
|
}
|
|
if dns.RecursionAvailable {
|
|
dh.Bits |= _RA
|
|
}
|
|
if dns.Zero {
|
|
dh.Bits |= _Z
|
|
}
|
|
if dns.AuthenticatedData {
|
|
dh.Bits |= _AD
|
|
}
|
|
if dns.CheckingDisabled {
|
|
dh.Bits |= _CD
|
|
}
|
|
|
|
// Prepare variable sized arrays.
|
|
question := dns.Question
|
|
answer := dns.Answer
|
|
ns := dns.Ns
|
|
extra := dns.Extra
|
|
|
|
dh.Qdcount = uint16(len(question))
|
|
dh.Ancount = uint16(len(answer))
|
|
dh.Nscount = uint16(len(ns))
|
|
dh.Arcount = uint16(len(extra))
|
|
|
|
// TODO(mg): still a little too much, but better than 64K...
|
|
msg = make([]byte, dns.Len()+10)
|
|
|
|
// Pack it in: header and then the pieces.
|
|
off := 0
|
|
off, err = packStructCompress(&dh, msg, off, compression, dns.Compress)
|
|
if err != nil {
|
|
return nil, err
|
|
}
|
|
for i := 0; i < len(question); i++ {
|
|
off, err = packStructCompress(&question[i], msg, off, compression, dns.Compress)
|
|
if err != nil {
|
|
return nil, err
|
|
}
|
|
}
|
|
for i := 0; i < len(answer); i++ {
|
|
off, err = PackRR(answer[i], msg, off, compression, dns.Compress)
|
|
if err != nil {
|
|
return nil, err
|
|
}
|
|
}
|
|
for i := 0; i < len(ns); i++ {
|
|
off, err = PackRR(ns[i], msg, off, compression, dns.Compress)
|
|
if err != nil {
|
|
return nil, err
|
|
}
|
|
}
|
|
for i := 0; i < len(extra); i++ {
|
|
off, err = PackRR(extra[i], msg, off, compression, dns.Compress)
|
|
if err != nil {
|
|
return nil, err
|
|
}
|
|
}
|
|
return msg[:off], nil
|
|
}
|
|
|
|
// Unpack unpacks a binary message to a Msg structure.
|
|
func (dns *Msg) Unpack(msg []byte) (err error) {
|
|
// Header.
|
|
var dh Header
|
|
off := 0
|
|
if off, err = UnpackStruct(&dh, msg, off); err != nil {
|
|
return err
|
|
}
|
|
dns.Id = dh.Id
|
|
dns.Response = (dh.Bits & _QR) != 0
|
|
dns.Opcode = int(dh.Bits>>11) & 0xF
|
|
dns.Authoritative = (dh.Bits & _AA) != 0
|
|
dns.Truncated = (dh.Bits & _TC) != 0
|
|
dns.RecursionDesired = (dh.Bits & _RD) != 0
|
|
dns.RecursionAvailable = (dh.Bits & _RA) != 0
|
|
dns.Zero = (dh.Bits & _Z) != 0
|
|
dns.AuthenticatedData = (dh.Bits & _AD) != 0
|
|
dns.CheckingDisabled = (dh.Bits & _CD) != 0
|
|
dns.Rcode = int(dh.Bits & 0xF)
|
|
|
|
// Arrays.
|
|
dns.Question = make([]Question, dh.Qdcount)
|
|
dns.Answer = make([]RR, dh.Ancount)
|
|
dns.Ns = make([]RR, dh.Nscount)
|
|
dns.Extra = make([]RR, dh.Arcount)
|
|
|
|
for i := 0; i < len(dns.Question); i++ {
|
|
off, err = UnpackStruct(&dns.Question[i], msg, off)
|
|
if err != nil {
|
|
return err
|
|
}
|
|
}
|
|
for i := 0; i < len(dns.Answer); i++ {
|
|
dns.Answer[i], off, err = UnpackRR(msg, off)
|
|
if err != nil {
|
|
return err
|
|
}
|
|
}
|
|
for i := 0; i < len(dns.Ns); i++ {
|
|
dns.Ns[i], off, err = UnpackRR(msg, off)
|
|
if err != nil {
|
|
return err
|
|
}
|
|
}
|
|
for i := 0; i < len(dns.Extra); i++ {
|
|
dns.Extra[i], off, err = UnpackRR(msg, off)
|
|
if err != nil {
|
|
return err
|
|
}
|
|
}
|
|
if off != len(msg) {
|
|
// TODO(miek) make this an error?
|
|
// use PackOpt to let people tell how detailed the error reporting
|
|
// should be?
|
|
// println("dns: extra bytes in dns packet", off, "<", len(msg))
|
|
}
|
|
return nil
|
|
}
|
|
|
|
// Convert a complete message to a string with dig-like output.
|
|
func (dns *Msg) String() string {
|
|
if dns == nil {
|
|
return "<nil> MsgHdr"
|
|
}
|
|
s := dns.MsgHdr.String() + " "
|
|
s += "QUERY: " + strconv.Itoa(len(dns.Question)) + ", "
|
|
s += "ANSWER: " + strconv.Itoa(len(dns.Answer)) + ", "
|
|
s += "AUTHORITY: " + strconv.Itoa(len(dns.Ns)) + ", "
|
|
s += "ADDITIONAL: " + strconv.Itoa(len(dns.Extra)) + "\n"
|
|
if len(dns.Question) > 0 {
|
|
s += "\n;; QUESTION SECTION:\n"
|
|
for i := 0; i < len(dns.Question); i++ {
|
|
s += dns.Question[i].String() + "\n"
|
|
}
|
|
}
|
|
if len(dns.Answer) > 0 {
|
|
s += "\n;; ANSWER SECTION:\n"
|
|
for i := 0; i < len(dns.Answer); i++ {
|
|
if dns.Answer[i] != nil {
|
|
s += dns.Answer[i].String() + "\n"
|
|
}
|
|
}
|
|
}
|
|
if len(dns.Ns) > 0 {
|
|
s += "\n;; AUTHORITY SECTION:\n"
|
|
for i := 0; i < len(dns.Ns); i++ {
|
|
if dns.Ns[i] != nil {
|
|
s += dns.Ns[i].String() + "\n"
|
|
}
|
|
}
|
|
}
|
|
if len(dns.Extra) > 0 {
|
|
s += "\n;; ADDITIONAL SECTION:\n"
|
|
for i := 0; i < len(dns.Extra); i++ {
|
|
if dns.Extra[i] != nil {
|
|
s += dns.Extra[i].String() + "\n"
|
|
}
|
|
}
|
|
}
|
|
return s
|
|
}
|
|
|
|
// Len return the message length when in (un)compressed wire format.
|
|
// If dns.Compress is true compression it is taken into account, currently
|
|
// this only counts owner name compression. There is no check for
|
|
// nil valued sections (allocated, but contain no RRs).
|
|
func (dns *Msg) Len() int {
|
|
// Message header is always 12 bytes
|
|
l := 12
|
|
var compression map[string]int
|
|
if dns.Compress {
|
|
compression = make(map[string]int)
|
|
}
|
|
|
|
for i := 0; i < len(dns.Question); i++ {
|
|
l += dns.Question[i].len()
|
|
if dns.Compress {
|
|
compressionHelper(compression, dns.Question[i].Name)
|
|
}
|
|
}
|
|
for i := 0; i < len(dns.Answer); i++ {
|
|
if dns.Compress {
|
|
if v, ok := compression[dns.Answer[i].Header().Name]; ok {
|
|
l += dns.Answer[i].len() - v
|
|
continue
|
|
}
|
|
compressionHelper(compression, dns.Answer[i].Header().Name)
|
|
}
|
|
l += dns.Answer[i].len()
|
|
}
|
|
for i := 0; i < len(dns.Ns); i++ {
|
|
if dns.Compress {
|
|
if v, ok := compression[dns.Ns[i].Header().Name]; ok {
|
|
l += dns.Ns[i].len() - v
|
|
continue
|
|
}
|
|
compressionHelper(compression, dns.Ns[i].Header().Name)
|
|
}
|
|
l += dns.Ns[i].len()
|
|
}
|
|
for i := 0; i < len(dns.Extra); i++ {
|
|
if dns.Compress {
|
|
if v, ok := compression[dns.Extra[i].Header().Name]; ok {
|
|
l += dns.Extra[i].len() - v
|
|
continue
|
|
}
|
|
compressionHelper(compression, dns.Extra[i].Header().Name)
|
|
}
|
|
l += dns.Extra[i].len()
|
|
}
|
|
return l
|
|
}
|
|
|
|
func compressionHelper(c map[string]int, s string) {
|
|
pref := ""
|
|
lbs := SplitLabels(s)
|
|
for j := len(lbs) - 1; j >= 0; j-- {
|
|
c[lbs[j]+"."+pref] = 1 + len(pref) + len(lbs[j])
|
|
pref = lbs[j] + "." + pref
|
|
}
|
|
}
|
|
|
|
// Id return a 16 bits random number to be used as a
|
|
// message id. The random provided should be good enough.
|
|
func Id() uint16 {
|
|
return uint16(rand.Int()) ^ uint16(time.Now().Nanosecond())
|
|
}
|