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tls.go
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tls.go
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package obfs
import (
"bytes"
"encoding/binary"
"io"
"math/rand"
"net"
"time"
"github.com/Dreamacro/clash/common/pool"
)
func init() {
rand.Seed(time.Now().Unix())
}
const (
chunkSize = 1 << 14 // 2 ** 14 == 16 * 1024
)
// TLSObfs is shadowsocks tls simple-obfs implementation
type TLSObfs struct {
net.Conn
server string
remain int
firstRequest bool
firstResponse bool
}
func (to *TLSObfs) read(b []byte, discardN int) (int, error) {
buf := pool.Get(discardN)
_, err := io.ReadFull(to.Conn, buf)
if err != nil {
return 0, err
}
pool.Put(buf)
sizeBuf := make([]byte, 2)
_, err = io.ReadFull(to.Conn, sizeBuf)
if err != nil {
return 0, nil
}
length := int(binary.BigEndian.Uint16(sizeBuf))
if length > len(b) {
n, err := to.Conn.Read(b)
if err != nil {
return n, err
}
to.remain = length - n
return n, nil
}
return io.ReadFull(to.Conn, b[:length])
}
func (to *TLSObfs) Read(b []byte) (int, error) {
if to.remain > 0 {
length := to.remain
if length > len(b) {
length = len(b)
}
n, err := io.ReadFull(to.Conn, b[:length])
to.remain -= n
return n, err
}
if to.firstResponse {
// type + ver + lensize + 91 = 96
// type + ver + lensize + 1 = 6
// type + ver = 3
to.firstResponse = false
return to.read(b, 105)
}
// type + ver = 3
return to.read(b, 3)
}
func (to *TLSObfs) Write(b []byte) (int, error) {
length := len(b)
for i := 0; i < length; i += chunkSize {
end := i + chunkSize
if end > length {
end = length
}
n, err := to.write(b[i:end])
if err != nil {
return n, err
}
}
return length, nil
}
func (to *TLSObfs) write(b []byte) (int, error) {
if to.firstRequest {
helloMsg := makeClientHelloMsg(b, to.server)
_, err := to.Conn.Write(helloMsg)
to.firstRequest = false
return len(b), err
}
buf := pool.GetBuffer()
defer pool.PutBuffer(buf)
buf.Write([]byte{0x17, 0x03, 0x03})
binary.Write(buf, binary.BigEndian, uint16(len(b)))
buf.Write(b)
_, err := to.Conn.Write(buf.Bytes())
return len(b), err
}
// NewTLSObfs return a SimpleObfs
func NewTLSObfs(conn net.Conn, server string) net.Conn {
return &TLSObfs{
Conn: conn,
server: server,
firstRequest: true,
firstResponse: true,
}
}
func makeClientHelloMsg(data []byte, server string) []byte {
random := make([]byte, 28)
sessionID := make([]byte, 32)
rand.Read(random)
rand.Read(sessionID)
buf := &bytes.Buffer{}
// handshake, TLS 1.0 version, length
buf.WriteByte(22)
buf.Write([]byte{0x03, 0x01})
length := uint16(212 + len(data) + len(server))
buf.WriteByte(byte(length >> 8))
buf.WriteByte(byte(length & 0xff))
// clientHello, length, TLS 1.2 version
buf.WriteByte(1)
buf.WriteByte(0)
binary.Write(buf, binary.BigEndian, uint16(208+len(data)+len(server)))
buf.Write([]byte{0x03, 0x03})
// random with timestamp, sid len, sid
binary.Write(buf, binary.BigEndian, uint32(time.Now().Unix()))
buf.Write(random)
buf.WriteByte(32)
buf.Write(sessionID)
// cipher suites
buf.Write([]byte{0x00, 0x38})
buf.Write([]byte{
0xc0, 0x2c, 0xc0, 0x30, 0x00, 0x9f, 0xcc, 0xa9, 0xcc, 0xa8, 0xcc, 0xaa, 0xc0, 0x2b, 0xc0, 0x2f,
0x00, 0x9e, 0xc0, 0x24, 0xc0, 0x28, 0x00, 0x6b, 0xc0, 0x23, 0xc0, 0x27, 0x00, 0x67, 0xc0, 0x0a,
0xc0, 0x14, 0x00, 0x39, 0xc0, 0x09, 0xc0, 0x13, 0x00, 0x33, 0x00, 0x9d, 0x00, 0x9c, 0x00, 0x3d,
0x00, 0x3c, 0x00, 0x35, 0x00, 0x2f, 0x00, 0xff,
})
// compression
buf.Write([]byte{0x01, 0x00})
// extension length
binary.Write(buf, binary.BigEndian, uint16(79+len(data)+len(server)))
// session ticket
buf.Write([]byte{0x00, 0x23})
binary.Write(buf, binary.BigEndian, uint16(len(data)))
buf.Write(data)
// server name
buf.Write([]byte{0x00, 0x00})
binary.Write(buf, binary.BigEndian, uint16(len(server)+5))
binary.Write(buf, binary.BigEndian, uint16(len(server)+3))
buf.WriteByte(0)
binary.Write(buf, binary.BigEndian, uint16(len(server)))
buf.Write([]byte(server))
// ec_point
buf.Write([]byte{0x00, 0x0b, 0x00, 0x04, 0x03, 0x01, 0x00, 0x02})
// groups
buf.Write([]byte{0x00, 0x0a, 0x00, 0x0a, 0x00, 0x08, 0x00, 0x1d, 0x00, 0x17, 0x00, 0x19, 0x00, 0x18})
// signature
buf.Write([]byte{
0x00, 0x0d, 0x00, 0x20, 0x00, 0x1e, 0x06, 0x01, 0x06, 0x02, 0x06, 0x03, 0x05,
0x01, 0x05, 0x02, 0x05, 0x03, 0x04, 0x01, 0x04, 0x02, 0x04, 0x03, 0x03, 0x01,
0x03, 0x02, 0x03, 0x03, 0x02, 0x01, 0x02, 0x02, 0x02, 0x03,
})
// encrypt then mac
buf.Write([]byte{0x00, 0x16, 0x00, 0x00})
// extended master secret
buf.Write([]byte{0x00, 0x17, 0x00, 0x00})
return buf.Bytes()
}