mirror of
https://github.com/XTLS/Xray-core.git
synced 2024-07-03 08:29:19 +03:00
124 lines
2.7 KiB
Go
124 lines
2.7 KiB
Go
package dns
|
|
|
|
import (
|
|
"context"
|
|
"encoding/binary"
|
|
"errors"
|
|
|
|
"github.com/xtls/xray-core/common"
|
|
"github.com/xtls/xray-core/common/dice"
|
|
)
|
|
|
|
type DNS struct {
|
|
header []byte
|
|
}
|
|
|
|
func (d DNS) Size() int32 {
|
|
return int32(len(d.header))
|
|
}
|
|
|
|
// Serialize implements PacketHeader.
|
|
func (d DNS) Serialize(b []byte) {
|
|
copy(b, d.header)
|
|
binary.BigEndian.PutUint16(b[0:], dice.RollUint16()) // random transaction ID
|
|
}
|
|
|
|
// NewDNS returns a new DNS instance based on given config.
|
|
func NewDNS(ctx context.Context, config interface{}) (interface{}, error) {
|
|
var header []byte
|
|
|
|
header = binary.BigEndian.AppendUint16(header, 0x0000) // Transaction ID
|
|
header = binary.BigEndian.AppendUint16(header, 0x0100) // Flags: Standard query
|
|
header = binary.BigEndian.AppendUint16(header, 0x0001) // Questions
|
|
header = binary.BigEndian.AppendUint16(header, 0x0000) // Answer RRs
|
|
header = binary.BigEndian.AppendUint16(header, 0x0000) // Authority RRs
|
|
header = binary.BigEndian.AppendUint16(header, 0x0000) // Additional RRs
|
|
|
|
buf := make([]byte, 0x100)
|
|
|
|
off1, err := packDomainName(config.(*Config).Domain+".", buf)
|
|
if err != nil {
|
|
return nil, err
|
|
}
|
|
|
|
header = append(header, buf[:off1]...)
|
|
|
|
header = binary.BigEndian.AppendUint16(header, 0x0001) // Type: A
|
|
header = binary.BigEndian.AppendUint16(header, 0x0001) // Class: IN
|
|
|
|
return DNS{
|
|
header: header,
|
|
}, nil
|
|
}
|
|
|
|
// copied from github.com/miekg/dns
|
|
func packDomainName(s string, msg []byte) (off1 int, err error) {
|
|
off := 0
|
|
ls := len(s)
|
|
// 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.
|
|
|
|
// Emit sequence of counted strings, chopping at dots.
|
|
var (
|
|
begin int
|
|
bs []byte
|
|
)
|
|
for i := 0; i < ls; i++ {
|
|
var c byte
|
|
if bs == nil {
|
|
c = s[i]
|
|
} else {
|
|
c = bs[i]
|
|
}
|
|
|
|
switch c {
|
|
case '\\':
|
|
if off+1 > len(msg) {
|
|
return len(msg), errors.New("buffer size too small")
|
|
}
|
|
|
|
if bs == nil {
|
|
bs = []byte(s)
|
|
}
|
|
|
|
copy(bs[i:ls-1], bs[i+1:])
|
|
ls--
|
|
case '.':
|
|
labelLen := i - begin
|
|
if labelLen >= 1<<6 { // top two bits of length must be clear
|
|
return len(msg), errors.New("bad rdata")
|
|
}
|
|
|
|
// 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+labelLen > len(msg) {
|
|
return len(msg), errors.New("buffer size too small")
|
|
}
|
|
|
|
// The following is covered by the length check above.
|
|
msg[off] = byte(labelLen)
|
|
|
|
if bs == nil {
|
|
copy(msg[off+1:], s[begin:i])
|
|
} else {
|
|
copy(msg[off+1:], bs[begin:i])
|
|
}
|
|
off += 1 + labelLen
|
|
begin = i + 1
|
|
default:
|
|
}
|
|
}
|
|
|
|
if off < len(msg) {
|
|
msg[off] = 0
|
|
}
|
|
|
|
return off + 1, nil
|
|
}
|
|
|
|
func init() {
|
|
common.Must(common.RegisterConfig((*Config)(nil), NewDNS))
|
|
}
|