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Cloak
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Change the stream header format and reduce overhead

This commit is contained in:
Qian Wang 2019-01-13 21:28:57 +00:00
parent f4a1c21c2c
commit 24cdf274dd
4 changed files with 23 additions and 21 deletions
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2
cmd/ck-client/ck-client.go
View File

@ -23,7 +23,7 @@ import (
var version string
func pipe(dst io.ReadWriteCloser, src io.ReadWriteCloser) {
// The maximum size of TLS message will be 16396+16. 16 because of the stream header
// The maximum size of TLS message will be 16396+12. 12 because of the stream header
// 16408 is the max TLS message size on Firefox
buf := make([]byte, 16396)
for {

2
cmd/ck-server/ck-server.go
View File

@ -24,7 +24,7 @@ import (
var version string
func pipe(dst io.ReadWriteCloser, src io.ReadWriteCloser) {
// The maximum size of TLS message will be 16396+16. 16 because of the stream header
// The maximum size of TLS message will be 16396+12. 12 because of the stream header
// 16408 is the max TLS message size on Firefox
buf := make([]byte, 16396)
for {

2
internal/multiplex/frame.go
View File

@ -5,6 +5,6 @@ import ()
type Frame struct {
StreamID uint32
Seq uint32
Closing uint32
Closing uint8
Payload []byte
}

38
internal/multiplex/obfs.go
View File

@ -13,34 +13,36 @@ type Deobfser func([]byte) (*Frame, error)
var u32 = binary.BigEndian.Uint32
const headerLen = 12
// For each frame, the three parts of the header is xored with three keys.
// The keys are generated from the SID and the payload of the frame.
func genXorKeys(key, nonce []byte) (i uint32, ii uint32, iii uint32) {
func genXorKeys(key, nonce []byte) (i uint32, ii uint32, iii uint8) {
h := sha1.New()
hashed := h.Sum(append(key, nonce...))
return u32(hashed[0:4]), u32(hashed[4:8]), u32(hashed[8:12])
return u32(hashed[0:4]), u32(hashed[4:8]), hashed[8]
}
func MakeObfs(key []byte) Obfser {
obfs := func(f *Frame) ([]byte, error) {
obfsedHeader := make([]byte, 16)
// header: [StreamID 4 bytes][Seq 4 bytes][Closing 4 bytes][Nonce 4 bytes]
io.ReadFull(rand.Reader, obfsedHeader[12:16])
i, ii, iii := genXorKeys(key, obfsedHeader[12:16])
obfsedHeader := make([]byte, headerLen)
// header: [StreamID 4 bytes][Seq 4 bytes][Closing 1 byte][Nonce 3 bytes]
io.ReadFull(rand.Reader, obfsedHeader[9:12])
i, ii, iii := genXorKeys(key, obfsedHeader[9:12])
binary.BigEndian.PutUint32(obfsedHeader[0:4], f.StreamID^i)
binary.BigEndian.PutUint32(obfsedHeader[4:8], f.Seq^ii)
binary.BigEndian.PutUint32(obfsedHeader[8:12], f.Closing^iii)
obfsedHeader[8] = f.Closing ^ iii
// Composing final obfsed message
// We don't use util.AddRecordLayer here to avoid unnecessary malloc
obfsed := make([]byte, 5+16+len(f.Payload))
obfsed := make([]byte, 5+headerLen+len(f.Payload))
obfsed[0] = 0x17
obfsed[1] = 0x03
obfsed[2] = 0x03
binary.BigEndian.PutUint16(obfsed[3:5], uint16(16+len(f.Payload)))
copy(obfsed[5:21], obfsedHeader)
copy(obfsed[21:], f.Payload)
// obfsed: [record layer 5 bytes][cipherheader 16 bytes][payload]
binary.BigEndian.PutUint16(obfsed[3:5], uint16(headerLen+len(f.Payload)))
copy(obfsed[5:5+headerLen], obfsedHeader)
copy(obfsed[5+headerLen:], f.Payload)
// obfsed: [record layer 5 bytes][cipherheader 12 bytes][payload]
return obfsed, nil
}
return obfs
@ -48,16 +50,16 @@ func MakeObfs(key []byte) Obfser {
func MakeDeobfs(key []byte) Deobfser {
deobfs := func(in []byte) (*Frame, error) {
if len(in) < 21 {
return nil, errors.New("Input cannot be shorter than 21 bytes")
if len(in) < 5+headerLen {
return nil, errors.New("Input cannot be shorter than 17 bytes")
}
peeled := in[5:]
i, ii, iii := genXorKeys(key, peeled[12:16])
i, ii, iii := genXorKeys(key, peeled[9:12])
streamID := u32(peeled[0:4]) ^ i
seq := u32(peeled[4:8]) ^ ii
closing := u32(peeled[8:12]) ^ iii
payload := make([]byte, len(peeled)-16)
copy(payload, peeled[16:])
closing := peeled[8] ^ iii
payload := make([]byte, len(peeled)-headerLen)
copy(payload, peeled[headerLen:])
ret := &Frame{
StreamID: streamID,
Seq: seq,