sing-box/transport/shadowtls/server_v3.go

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2023-02-18 06:55:47 +00:00
package shadowtls
import (
"bytes"
"crypto/hmac"
"crypto/sha1"
"encoding/binary"
"hash"
"io"
"net"
"github.com/sagernet/sing/common"
"github.com/sagernet/sing/common/buf"
"github.com/sagernet/sing/common/bufio"
E "github.com/sagernet/sing/common/exceptions"
"github.com/sagernet/sing/common/rw"
)
func ExtractFrame(conn net.Conn) (*buf.Buffer, error) {
var tlsHeader [tlsHeaderSize]byte
_, err := io.ReadFull(conn, tlsHeader[:])
if err != nil {
return nil, err
}
length := int(binary.BigEndian.Uint16(tlsHeader[3:]))
buffer := buf.NewSize(tlsHeaderSize + length)
common.Must1(buffer.Write(tlsHeader[:]))
_, err = buffer.ReadFullFrom(conn, length)
if err != nil {
buffer.Release()
}
return buffer, err
}
func VerifyClientHello(frame []byte, password string) error {
const minLen = tlsHeaderSize + 1 + 3 + 2 + tlsRandomSize + 1 + tlsSessionIDSize
const hmacIndex = sessionIDLengthIndex + 1 + tlsSessionIDSize - hmacSize
if len(frame) < minLen {
return io.ErrUnexpectedEOF
} else if frame[0] != handshake {
return E.New("unexpected record type")
} else if frame[5] != clientHello {
return E.New("unexpected handshake type")
} else if frame[sessionIDLengthIndex] != tlsSessionIDSize {
return E.New("unexpected session id length")
}
hmacSHA1Hash := hmac.New(sha1.New, []byte(password))
hmacSHA1Hash.Write(frame[tlsHeaderSize:hmacIndex])
hmacSHA1Hash.Write(rw.ZeroBytes[:4])
hmacSHA1Hash.Write(frame[hmacIndex+hmacSize:])
if !hmac.Equal(frame[hmacIndex:hmacIndex+hmacSize], hmacSHA1Hash.Sum(nil)[:hmacSize]) {
return E.New("hmac mismatch")
}
return nil
}
func ExtractServerRandom(frame []byte) []byte {
const minLen = tlsHeaderSize + 1 + 3 + 2 + tlsRandomSize
if len(frame) < minLen || frame[0] != handshake || frame[5] != serverHello {
return nil
}
serverRandom := make([]byte, tlsRandomSize)
copy(serverRandom, frame[serverRandomIndex:serverRandomIndex+tlsRandomSize])
return serverRandom
}
func IsServerHelloSupportTLS13(frame []byte) bool {
if len(frame) < sessionIDLengthIndex {
return false
}
reader := bytes.NewReader(frame[sessionIDLengthIndex:])
var sessionIdLength uint8
err := binary.Read(reader, binary.BigEndian, &sessionIdLength)
if err != nil {
return false
}
_, err = io.CopyN(io.Discard, reader, int64(sessionIdLength))
if err != nil {
return false
}
_, err = io.CopyN(io.Discard, reader, 3)
if err != nil {
return false
}
var extensionListLength uint16
err = binary.Read(reader, binary.BigEndian, &extensionListLength)
if err != nil {
return false
}
for i := uint16(0); i < extensionListLength; i++ {
var extensionType uint16
err = binary.Read(reader, binary.BigEndian, &extensionType)
if err != nil {
return false
}
var extensionLength uint16
err = binary.Read(reader, binary.BigEndian, &extensionLength)
if err != nil {
return false
}
if extensionType != 43 {
_, err = io.CopyN(io.Discard, reader, int64(extensionLength))
if err != nil {
return false
}
continue
}
if extensionLength != 2 {
return false
}
var extensionValue uint16
err = binary.Read(reader, binary.BigEndian, &extensionValue)
if err != nil {
return false
}
return extensionValue == 0x0304
}
return false
}
func CopyByFrameUntilHMACMatches(conn net.Conn, handshakeConn net.Conn, hmacVerify hash.Hash, hmacReset func()) (*buf.Buffer, error) {
for {
frameBuffer, err := ExtractFrame(conn)
if err != nil {
return nil, E.Cause(err, "read client record")
}
frame := frameBuffer.Bytes()
if len(frame) > tlsHmacHeaderSize && frame[0] == applicationData {
hmacReset()
hmacVerify.Write(frame[tlsHmacHeaderSize:])
hmacHash := hmacVerify.Sum(nil)[:4]
if bytes.Equal(hmacHash, frame[tlsHeaderSize:tlsHmacHeaderSize]) {
hmacReset()
hmacVerify.Write(frame[tlsHmacHeaderSize:])
hmacVerify.Write(frame[tlsHeaderSize:tlsHmacHeaderSize])
frameBuffer.Advance(tlsHmacHeaderSize)
return frameBuffer, nil
}
}
_, err = handshakeConn.Write(frame)
frameBuffer.Release()
if err != nil {
return nil, E.Cause(err, "write clint frame")
}
}
}
func CopyByFrameWithModification(conn net.Conn, handshakeConn net.Conn, password string, serverRandom []byte, hmacWrite hash.Hash) error {
writeKey := kdf(password, serverRandom)
writer := bufio.NewVectorisedWriter(handshakeConn)
for {
frameBuffer, err := ExtractFrame(conn)
if err != nil {
return E.Cause(err, "read server record")
}
frame := frameBuffer.Bytes()
if frame[0] == applicationData {
xorSlice(frame[tlsHeaderSize:], writeKey)
hmacWrite.Write(frame[tlsHeaderSize:])
binary.BigEndian.PutUint16(frame[3:], uint16(len(frame)-tlsHeaderSize+hmacSize))
hmacHash := hmacWrite.Sum(nil)[:4]
_, err = bufio.WriteVectorised(writer, [][]byte{frame[:tlsHeaderSize], hmacHash, frame[tlsHeaderSize:]})
frameBuffer.Release()
if err != nil {
return E.Cause(err, "write modified server frame")
}
} else {
_, err = handshakeConn.Write(frame)
frameBuffer.Release()
if err != nil {
return E.Cause(err, "write server frame")
}
}
}
}