Redo the header obfuscation. Fix hiccups caused by short packets

cmd/ck-client/ck-client.go

@@ -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+12. 12 because of the stream header
+	// The maximum size of TLS message will be 16396+16. 16 because of the stream header
 	// 16408 is the max TLS message size on Firefox
 	buf := make([]byte, 16396)
 	for {

cmd/ck-server/ck-server.go

@@ -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+12. 12 because of the stream header
+	// The maximum size of TLS message will be 16396+16. 16 because of the stream header
 	// 16408 is the max TLS message size on Firefox
 	buf := make([]byte, 16396)
 	for {

internal/multiplex/obfs.go

@@ -1,52 +1,46 @@
 package multiplex
 
 import (
+	"crypto/rand"
+	"crypto/sha1"
 	"encoding/binary"
 	"errors"
-
+	"io"
-	xxhash "github.com/OneOfOne/xxhash"
 )
 
 type Obfser func(*Frame) ([]byte, error)
 type Deobfser func([]byte) (*Frame, error)
 
+var u32 = binary.BigEndian.Uint32
+
 // 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(secret []byte, data []byte) (i uint32, ii uint32, iii uint32) {
+func genXorKeys(key, nonce []byte) (i uint32, ii uint32, iii uint32) {
-	h := xxhash.New32()
+	h := sha1.New()
-	ret := make([]uint32, 3)
+	hashed := h.Sum(append(key, nonce...))
-	preHash := make([]byte, 16)
+	return u32(hashed[0:4]), u32(hashed[4:8]), u32(hashed[8:12])
-	for j := 0; j < 3; j++ {
-		copy(preHash[0:10], secret[j*10:j*10+10])
-		copy(preHash[10:16], data[j*6:j*6+6])
-		h.Write(preHash)
-		ret[j] = h.Sum32()
-	}
-	return ret[0], ret[1], ret[2]
 }
 
 func MakeObfs(key []byte) Obfser {
 	obfs := func(f *Frame) ([]byte, error) {
-		if len(f.Payload) < 18 {
+		obfsedHeader := make([]byte, 16)
-			return nil, errors.New("Payload cannot be shorter than 18 bytes")
+		// header: [StreamID 4 bytes][Seq 4 bytes][Closing 4 bytes][Nonce 4 bytes]
-		}
+		io.ReadFull(rand.Reader, obfsedHeader[12:16])
-		obfsedHeader := make([]byte, 12)
+		i, ii, iii := genXorKeys(key, obfsedHeader[12:16])
-		// header: [StreamID 4 bytes][Seq 4 bytes][Closing 4 bytes]
-		i, ii, iii := genXorKeys(key, f.Payload[0:18])
 		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)
 
 		// Composing final obfsed message
 		// We don't use util.AddRecordLayer here to avoid unnecessary malloc
-		obfsed := make([]byte, 5+12+len(f.Payload))
+		obfsed := make([]byte, 5+16+len(f.Payload))
 		obfsed[0] = 0x17
 		obfsed[1] = 0x03
 		obfsed[2] = 0x03
-		binary.BigEndian.PutUint16(obfsed[3:5], uint16(12+len(f.Payload)))
+		binary.BigEndian.PutUint16(obfsed[3:5], uint16(16+len(f.Payload)))
-		copy(obfsed[5:17], obfsedHeader)
+		copy(obfsed[5:21], obfsedHeader)
-		copy(obfsed[17:], f.Payload)
+		copy(obfsed[21:], f.Payload)
-		// obfsed: [record layer 5 bytes][cipherheader 12 bytes][payload]
+		// obfsed: [record layer 5 bytes][cipherheader 16 bytes][payload]
 		return obfsed, nil
 	}
 	return obfs
@@ -54,16 +48,16 @@ func MakeObfs(key []byte) Obfser {
 
 func MakeDeobfs(key []byte) Deobfser {
 	deobfs := func(in []byte) (*Frame, error) {
-		if len(in) < 30 {
+		if len(in) < 21 {
-			return nil, errors.New("Input cannot be shorter than 30 bytes")
+			return nil, errors.New("Input cannot be shorter than 21 bytes")
 		}
 		peeled := in[5:]
-		i, ii, iii := genXorKeys(key, peeled[12:30])
+		i, ii, iii := genXorKeys(key, peeled[12:16])
-		streamID := binary.BigEndian.Uint32(peeled[0:4]) ^ i
+		streamID := u32(peeled[0:4]) ^ i
-		seq := binary.BigEndian.Uint32(peeled[4:8]) ^ ii
+		seq := u32(peeled[4:8]) ^ ii
-		closing := binary.BigEndian.Uint32(peeled[8:12]) ^ iii
+		closing := u32(peeled[8:12]) ^ iii
-		payload := make([]byte, len(peeled)-12)
+		payload := make([]byte, len(peeled)-16)
-		copy(payload, peeled[12:])
+		copy(payload, peeled[16:])
 		ret := &Frame{
 			StreamID: streamID,
 			Seq:      seq,

internal/multiplex/stream.go

@@ -9,7 +9,7 @@ import (
 	"sync/atomic"
 )
 
-var errBrokenStream = errors.New("broken stream")
+var ErrBrokenStream = errors.New("broken stream")
 
 type Stream struct {
 	id uint32
@@ -18,9 +18,9 @@ type Stream struct {
 
 	// Explanations of the following 4 fields can be found in frameSorter.go
 	nextRecvSeq uint32
-	rev         int
+	//rev         int
-	sh          sorterHeap
+	sh sorterHeap
-	wrapMode    bool
+	//wrapMode    bool
 
 	// New frames are received through newFrameCh by frameSorter
 	newFrameCh chan *Frame
@@ -54,18 +54,18 @@ func (stream *Stream) Read(buf []byte) (n int, err error) {
 	if len(buf) == 0 {
 		select {
 		case <-stream.die:
-			return 0, errBrokenStream
+			return 0, ErrBrokenStream
 		default:
 			return 0, nil
 		}
 	}
 	select {
 	case <-stream.die:
-		return 0, errBrokenStream
+		return 0, ErrBrokenStream
 	case data := <-stream.sortedBufCh:
 		if len(data) == 0 {
 			stream.passiveClose()
-			return 0, errBrokenStream
+			return 0, ErrBrokenStream
 		}
 		if len(buf) < len(data) {
 			log.Println(len(data))
@@ -87,7 +87,7 @@ func (stream *Stream) Write(in []byte) (n int, err error) {
 	select {
 	case <-stream.die:
 		stream.writingM.RUnlock()
-		return 0, errBrokenStream
+		return 0, ErrBrokenStream
 	default:
 	}
 

internal/multiplex/switchboard.go

@@ -18,12 +18,6 @@ type switchboard struct {
 	optimum atomic.Value // *connEnclave
 	cesM    sync.RWMutex
 	ces     []*connEnclave
-
-	/*
-		//debug
-		hM   sync.Mutex
-		used map[uint32]bool
-	*/
 }
 
 func (sb *switchboard) getOptimum() *connEnclave {
@@ -34,10 +28,6 @@ func (sb *switchboard) getOptimum() *connEnclave {
 	}
 }
 
-func (sb *switchboard) setOptimum(ce *connEnclave) {
-	sb.optimum.Store(ce)
-}
-
 // Some data comes from a Stream to be sent through one of the many
 // remoteConn, but which remoteConn should we use to send the data?
 //
@@ -54,8 +44,6 @@ func makeSwitchboard(sesh *Session, valve *Valve) *switchboard {
 		session: sesh,
 		Valve:   valve,
 		ces:     []*connEnclave{},
-		//debug
-		// used: make(map[uint32]bool),
 	}
 	return sb
 }
@@ -99,18 +87,19 @@ func (sb *switchboard) updateOptimum() {
 		}
 	}
 	sb.cesM.RUnlock()
-	sb.setOptimum(currentOpti)
+	sb.optimum.Store(currentOpti)
 }
 
 func (sb *switchboard) addConn(conn net.Conn) {
+	var sendQueue uint32
 	newCe := &connEnclave{
 		remoteConn: conn,
-		sendQueue:  0,
+		sendQueue:  sendQueue,
 	}
 	sb.cesM.Lock()
 	sb.ces = append(sb.ces, newCe)
 	sb.cesM.Unlock()
-	sb.setOptimum(newCe)
+	sb.optimum.Store(newCe)
 	go sb.deplex(newCe)
 }
 
@@ -177,14 +166,5 @@ func (sb *switchboard) deplex(ce *connEnclave) {
 		if stream != nil {
 			stream.writeNewFrame(frame)
 		}
-		//debug
-		/*
-			sb.hM.Lock()
-			if sb.used[frame.StreamID] {
-				log.Printf("%v lost!\n", frame.StreamID)
-			}
-			sb.used[frame.StreamID] = true
-			sb.hM.Unlock()
-		*/
 	}
 }