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Cloak
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Refactor obfuscate and deobfuscate functions to reduce a layer of indirection

This commit is contained in:
Andy Wang 2020-12-26 00:49:36 +00:00
parent 2f17841f85
commit 415523f10a
No known key found for this signature in database
GPG Key ID: 181B49F9F38F3374
6 changed files with 163 additions and 154 deletions
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189
internal/multiplex/obfs.go
View File

@ -11,9 +11,6 @@ import (
"golang.org/x/crypto/salsa20"
)
type Obfser func(*Frame, []byte, int) (int, error)
type Deobfser func(*Frame, []byte) error
var u32 = binary.BigEndian.Uint32
var u64 = binary.BigEndian.Uint64
var putU32 = binary.BigEndian.PutUint32
@ -30,21 +27,15 @@ const (
// Obfuscator is responsible for serialisation, obfuscation, and optional encryption of data frames.
type Obfuscator struct {
// Used in Stream.Write. Add multiplexing headers, encrypt and add TLS header
Obfs Obfser
// Remove TLS header, decrypt and unmarshall frames
Deobfs Deobfser
payloadCipher cipher.AEAD
SessionKey [32]byte
maxOverhead int
}
// MakeObfs returns a function of type Obfser. An Obfser takes three arguments:
// a *Frame with all the field set correctly, a []byte as buffer to put encrypted
// message in, and an int called payloadOffsetInBuf to be used when *Frame.payload
// is in the byte slice used as buffer (2nd argument). payloadOffsetInBuf specifies
// the index at which data belonging to *Frame.Payload starts in the buffer.
func MakeObfs(salsaKey [32]byte, payloadCipher cipher.AEAD) Obfser {
// obfuscate adds multiplexing headers, encrypt and add TLS header
func (o *Obfuscator) obfuscate(f *Frame, buf []byte, payloadOffsetInBuf int) (int, error) {
// The method here is to use the first payloadCipher.NonceSize() bytes of the serialised frame header
// as iv/nonce for the AEAD cipher to encrypt the frame payload. Then we use
// the authentication tag produced appended to the end of the ciphertext (of size payloadCipher.Overhead())
@ -76,109 +67,99 @@ func MakeObfs(salsaKey [32]byte, payloadCipher cipher.AEAD) Obfser {
// We can't ensure its uniqueness ourselves, which is why plaintext mode must only be used when the user input
// is already random-like. For Cloak it would normally mean that the user is using a proxy protocol that sends
// encrypted data.
obfs := func(f *Frame, buf []byte, payloadOffsetInBuf int) (int, error) {
payloadLen := len(f.Payload)
if payloadLen == 0 {
return 0, errors.New("payload cannot be empty")
}
var extraLen int
if payloadCipher == nil {
extraLen = salsa20NonceSize - payloadLen
if extraLen < 0 {
// if our payload is already greater than 8 bytes
extraLen = 0
}
} else {
extraLen = payloadCipher.Overhead()
if extraLen < salsa20NonceSize {
return 0, errors.New("AEAD's Overhead cannot be fewer than 8 bytes")
}
}
usefulLen := frameHeaderLength + payloadLen + extraLen
if len(buf) < usefulLen {
return 0, errors.New("obfs buffer too small")
}
// we do as much in-place as possible to save allocation
payload := buf[frameHeaderLength : frameHeaderLength+payloadLen]
if payloadOffsetInBuf != frameHeaderLength {
// if payload is not at the correct location in buffer
copy(payload, f.Payload)
}
header := buf[:frameHeaderLength]
putU32(header[0:4], f.StreamID)
putU64(header[4:12], f.Seq)
header[12] = f.Closing
header[13] = byte(extraLen)
if payloadCipher == nil {
if extraLen != 0 { // read nonce
extra := buf[usefulLen-extraLen : usefulLen]
common.CryptoRandRead(extra)
}
} else {
payloadCipher.Seal(payload[:0], header[:payloadCipher.NonceSize()], payload, nil)
}
nonce := buf[usefulLen-salsa20NonceSize : usefulLen]
salsa20.XORKeyStream(header, header, nonce, &salsaKey)
return usefulLen, nil
payloadLen := len(f.Payload)
if payloadLen == 0 {
return 0, errors.New("payload cannot be empty")
}
return obfs
var extraLen int
if o.payloadCipher == nil {
extraLen = salsa20NonceSize - payloadLen
if extraLen < 0 {
// if our payload is already greater than 8 bytes
extraLen = 0
}
} else {
extraLen = o.payloadCipher.Overhead()
if extraLen < salsa20NonceSize {
return 0, errors.New("AEAD's Overhead cannot be fewer than 8 bytes")
}
}
usefulLen := frameHeaderLength + payloadLen + extraLen
if len(buf) < usefulLen {
return 0, errors.New("obfs buffer too small")
}
// we do as much in-place as possible to save allocation
payload := buf[frameHeaderLength : frameHeaderLength+payloadLen]
if payloadOffsetInBuf != frameHeaderLength {
// if payload is not at the correct location in buffer
copy(payload, f.Payload)
}
header := buf[:frameHeaderLength]
putU32(header[0:4], f.StreamID)
putU64(header[4:12], f.Seq)
header[12] = f.Closing
header[13] = byte(extraLen)
if o.payloadCipher == nil {
if extraLen != 0 { // read nonce
extra := buf[usefulLen-extraLen : usefulLen]
common.CryptoRandRead(extra)
}
} else {
o.payloadCipher.Seal(payload[:0], header[:o.payloadCipher.NonceSize()], payload, nil)
}
nonce := buf[usefulLen-salsa20NonceSize : usefulLen]
salsa20.XORKeyStream(header, header, nonce, &o.SessionKey)
return usefulLen, nil
}
// MakeDeobfs returns a function Deobfser. A Deobfser takes in a single byte slice,
// containing the message to be decrypted, and returns a *Frame containing the frame
// information and plaintext
func MakeDeobfs(salsaKey [32]byte, payloadCipher cipher.AEAD) Deobfser {
// frame header length + minimum data size (i.e. nonce size of salsa20)
const minInputLen = frameHeaderLength + salsa20NonceSize
deobfs := func(f *Frame, in []byte) error {
if len(in) < minInputLen {
return fmt.Errorf("input size %v, but it cannot be shorter than %v bytes", len(in), minInputLen)
}
// deobfuscate removes TLS header, decrypt and unmarshall frames
func (o *Obfuscator) deobfuscate(f *Frame, in []byte) error {
if len(in) < frameHeaderLength+salsa20NonceSize {
return fmt.Errorf("input size %v, but it cannot be shorter than %v bytes", len(in), frameHeaderLength+salsa20NonceSize)
}
header := in[:frameHeaderLength]
pldWithOverHead := in[frameHeaderLength:] // payload + potential overhead
header := in[:frameHeaderLength]
pldWithOverHead := in[frameHeaderLength:] // payload + potential overhead
nonce := in[len(in)-salsa20NonceSize:]
salsa20.XORKeyStream(header, header, nonce, &salsaKey)
nonce := in[len(in)-salsa20NonceSize:]
salsa20.XORKeyStream(header, header, nonce, &o.SessionKey)
streamID := u32(header[0:4])
seq := u64(header[4:12])
closing := header[12]
extraLen := header[13]
streamID := u32(header[0:4])
seq := u64(header[4:12])
closing := header[12]
extraLen := header[13]
usefulPayloadLen := len(pldWithOverHead) - int(extraLen)
if usefulPayloadLen < 0 || usefulPayloadLen > len(pldWithOverHead) {
return errors.New("extra length is negative or extra length is greater than total pldWithOverHead length")
}
usefulPayloadLen := len(pldWithOverHead) - int(extraLen)
if usefulPayloadLen < 0 || usefulPayloadLen > len(pldWithOverHead) {
return errors.New("extra length is negative or extra length is greater than total pldWithOverHead length")
}
var outputPayload []byte
var outputPayload []byte
if payloadCipher == nil {
if extraLen == 0 {
outputPayload = pldWithOverHead
} else {
outputPayload = pldWithOverHead[:usefulPayloadLen]
}
if o.payloadCipher == nil {
if extraLen == 0 {
outputPayload = pldWithOverHead
} else {
_, err := payloadCipher.Open(pldWithOverHead[:0], header[:payloadCipher.NonceSize()], pldWithOverHead, nil)
if err != nil {
return err
}
outputPayload = pldWithOverHead[:usefulPayloadLen]
}
f.StreamID = streamID
f.Seq = seq
f.Closing = closing
f.Payload = outputPayload
return nil
} else {
_, err := o.payloadCipher.Open(pldWithOverHead[:0], header[:o.payloadCipher.NonceSize()], pldWithOverHead, nil)
if err != nil {
return err
}
outputPayload = pldWithOverHead[:usefulPayloadLen]
}
return deobfs
f.StreamID = streamID
f.Seq = seq
f.Closing = closing
f.Payload = outputPayload
return nil
}
func MakeObfuscator(encryptionMethod byte, sessionKey [32]byte) (obfuscator Obfuscator, err error) {
@ -217,7 +198,5 @@ func MakeObfuscator(encryptionMethod byte, sessionKey [32]byte) (obfuscator Obfu
}
}
obfuscator.Obfs = MakeObfs(sessionKey, payloadCipher)
obfuscator.Deobfs = MakeDeobfs(sessionKey, payloadCipher)
return
}

86
internal/multiplex/obfs_test.go
View File

@ -19,14 +19,14 @@ func TestGenerateObfs(t *testing.T) {
obfsBuf := make([]byte, 512)
_testFrame, _ := quick.Value(reflect.TypeOf(&Frame{}), rand.New(rand.NewSource(42)))
testFrame := _testFrame.Interface().(*Frame)
i, err := obfuscator.Obfs(testFrame, obfsBuf, 0)
i, err := obfuscator.obfuscate(testFrame, obfsBuf, 0)
if err != nil {
ct.Error("failed to obfs ", err)
return
}
var resultFrame Frame
err = obfuscator.Deobfs(&resultFrame, obfsBuf[:i])
err = obfuscator.deobfuscate(&resultFrame, obfsBuf[:i])
if err != nil {
ct.Error("failed to deobfs ", err)
return
@ -88,40 +88,57 @@ func BenchmarkObfs(b *testing.B) {
c, _ := aes.NewCipher(key[:])
payloadCipher, _ := cipher.NewGCM(c)
obfs := MakeObfs(key, payloadCipher)
obfuscator := Obfuscator{
payloadCipher: payloadCipher,
SessionKey: key,
maxOverhead: payloadCipher.Overhead(),
}
b.SetBytes(int64(len(testFrame.Payload)))
b.ResetTimer()
for i := 0; i < b.N; i++ {
obfs(testFrame, obfsBuf, 0)
obfuscator.obfuscate(testFrame, obfsBuf, 0)
}
})
b.Run("AES128GCM", func(b *testing.B) {
c, _ := aes.NewCipher(key[:16])
payloadCipher, _ := cipher.NewGCM(c)
obfs := MakeObfs(key, payloadCipher)
obfuscator := Obfuscator{
payloadCipher: payloadCipher,
SessionKey: key,
maxOverhead: payloadCipher.Overhead(),
}
b.SetBytes(int64(len(testFrame.Payload)))
b.ResetTimer()
for i := 0; i < b.N; i++ {
obfs(testFrame, obfsBuf, 0)
obfuscator.obfuscate(testFrame, obfsBuf, 0)
}
})
b.Run("plain", func(b *testing.B) {
obfs := MakeObfs(key, nil)
obfuscator := Obfuscator{
payloadCipher: nil,
SessionKey: key,
maxOverhead: salsa20NonceSize,
}
b.SetBytes(int64(len(testFrame.Payload)))
b.ResetTimer()
for i := 0; i < b.N; i++ {
obfs(testFrame, obfsBuf, 0)
obfuscator.obfuscate(testFrame, obfsBuf, 0)
}
})
b.Run("chacha20Poly1305", func(b *testing.B) {
payloadCipher, _ := chacha20poly1305.New(key[:16])
payloadCipher, _ := chacha20poly1305.New(key[:])
obfs := MakeObfs(key, payloadCipher)
obfuscator := Obfuscator{
payloadCipher: payloadCipher,
SessionKey: key,
maxOverhead: payloadCipher.Overhead(),
}
b.SetBytes(int64(len(testFrame.Payload)))
b.ResetTimer()
for i := 0; i < b.N; i++ {
obfs(testFrame, obfsBuf, 0)
obfuscator.obfuscate(testFrame, obfsBuf, 0)
}
})
}
@ -143,57 +160,70 @@ func BenchmarkDeobfs(b *testing.B) {
b.Run("AES256GCM", func(b *testing.B) {
c, _ := aes.NewCipher(key[:])
payloadCipher, _ := cipher.NewGCM(c)
obfuscator := Obfuscator{
payloadCipher: payloadCipher,
SessionKey: key,
maxOverhead: payloadCipher.Overhead(),
}
obfs := MakeObfs(key, payloadCipher)
n, _ := obfs(testFrame, obfsBuf, 0)
deobfs := MakeDeobfs(key, payloadCipher)
n, _ := obfuscator.obfuscate(testFrame, obfsBuf, 0)
frame := new(Frame)
b.SetBytes(int64(n))
b.ResetTimer()
for i := 0; i < b.N; i++ {
deobfs(frame, obfsBuf[:n])
obfuscator.deobfuscate(frame, obfsBuf[:n])
}
})
b.Run("AES128GCM", func(b *testing.B) {
c, _ := aes.NewCipher(key[:16])
payloadCipher, _ := cipher.NewGCM(c)
obfs := MakeObfs(key, payloadCipher)
n, _ := obfs(testFrame, obfsBuf, 0)
deobfs := MakeDeobfs(key, payloadCipher)
obfuscator := Obfuscator{
payloadCipher: payloadCipher,
SessionKey: key,
maxOverhead: payloadCipher.Overhead(),
}
n, _ := obfuscator.obfuscate(testFrame, obfsBuf, 0)
frame := new(Frame)
b.ResetTimer()
b.SetBytes(int64(n))
for i := 0; i < b.N; i++ {
deobfs(frame, obfsBuf[:n])
obfuscator.deobfuscate(frame, obfsBuf[:n])
}
})
b.Run("plain", func(b *testing.B) {
obfs := MakeObfs(key, nil)
n, _ := obfs(testFrame, obfsBuf, 0)
deobfs := MakeDeobfs(key, nil)
obfuscator := Obfuscator{
payloadCipher: nil,
SessionKey: key,
maxOverhead: salsa20NonceSize,
}
n, _ := obfuscator.obfuscate(testFrame, obfsBuf, 0)
frame := new(Frame)
b.ResetTimer()
b.SetBytes(int64(n))
for i := 0; i < b.N; i++ {
deobfs(frame, obfsBuf[:n])
obfuscator.deobfuscate(frame, obfsBuf[:n])
}
})
b.Run("chacha20Poly1305", func(b *testing.B) {
payloadCipher, _ := chacha20poly1305.New(key[:16])
payloadCipher, _ := chacha20poly1305.New(key[:])
obfs := MakeObfs(key, payloadCipher)
n, _ := obfs(testFrame, obfsBuf, 0)
deobfs := MakeDeobfs(key, payloadCipher)
obfuscator := Obfuscator{
payloadCipher: nil,
SessionKey: key,
maxOverhead: payloadCipher.Overhead(),
}
n, _ := obfuscator.obfuscate(testFrame, obfsBuf, 0)
frame := new(Frame)
b.ResetTimer()
b.SetBytes(int64(n))
for i := 0; i < b.N; i++ {
deobfs(frame, obfsBuf[:n])
obfuscator.deobfuscate(frame, obfsBuf[:n])
}
})
}

4
internal/multiplex/session.go
View File

@ -232,7 +232,7 @@ func (sesh *Session) recvDataFromRemote(data []byte) error {
frame := sesh.recvFramePool.Get().(*Frame)
defer sesh.recvFramePool.Put(frame)
err := sesh.Deobfs(frame, data)
err := sesh.deobfuscate(frame, data)
if err != nil {
return fmt.Errorf("Failed to decrypt a frame for session %v: %v", sesh.id, err)
}
@ -331,7 +331,7 @@ func (sesh *Session) Close() error {
Closing: closingSession,
Payload: payload,
}
i, err := sesh.Obfs(f, *buf, frameHeaderLength)
i, err := sesh.obfuscate(f, *buf, frameHeaderLength)
if err != nil {
return err
}

20
internal/multiplex/session_test.go
View File

@ -56,7 +56,7 @@ func TestRecvDataFromRemote(t *testing.T) {
t.Run(method, func(t *testing.T) {
seshConfig.Obfuscator = obfuscator
sesh := MakeSession(0, seshConfig)
n, err := sesh.Obfs(f, obfsBuf, 0)
n, err := sesh.obfuscate(f, obfsBuf, 0)
if err != nil {
t.Error(err)
return
@ -107,7 +107,7 @@ func TestRecvDataFromRemote_Closing_InOrder(t *testing.T) {
testPayload,
}
// create stream 1
n, _ := sesh.Obfs(f1, obfsBuf, 0)
n, _ := sesh.obfuscate(f1, obfsBuf, 0)
err := sesh.recvDataFromRemote(obfsBuf[:n])
if err != nil {
t.Fatalf("receiving normal frame for stream 1: %v", err)
@ -129,7 +129,7 @@ func TestRecvDataFromRemote_Closing_InOrder(t *testing.T) {
closingNothing,
testPayload,
}
n, _ = sesh.Obfs(f2, obfsBuf, 0)
n, _ = sesh.obfuscate(f2, obfsBuf, 0)
err = sesh.recvDataFromRemote(obfsBuf[:n])
if err != nil {
t.Fatalf("receiving normal frame for stream 2: %v", err)
@ -151,7 +151,7 @@ func TestRecvDataFromRemote_Closing_InOrder(t *testing.T) {
closingStream,
testPayload,
}
n, _ = sesh.Obfs(f1CloseStream, obfsBuf, 0)
n, _ = sesh.obfuscate(f1CloseStream, obfsBuf, 0)
err = sesh.recvDataFromRemote(obfsBuf[:n])
if err != nil {
t.Fatalf("receiving stream closing frame for stream 1: %v", err)
@ -180,7 +180,7 @@ func TestRecvDataFromRemote_Closing_InOrder(t *testing.T) {
}
// close stream 1 again
n, _ = sesh.Obfs(f1CloseStream, obfsBuf, 0)
n, _ = sesh.obfuscate(f1CloseStream, obfsBuf, 0)
err = sesh.recvDataFromRemote(obfsBuf[:n])
if err != nil {
t.Fatalf("receiving stream closing frame for stream 1 %v", err)
@ -203,7 +203,7 @@ func TestRecvDataFromRemote_Closing_InOrder(t *testing.T) {
Closing: closingSession,
Payload: testPayload,
}
n, _ = sesh.Obfs(fCloseSession, obfsBuf, 0)
n, _ = sesh.obfuscate(fCloseSession, obfsBuf, 0)
err = sesh.recvDataFromRemote(obfsBuf[:n])
if err != nil {
t.Fatalf("receiving session closing frame: %v", err)
@ -246,7 +246,7 @@ func TestRecvDataFromRemote_Closing_OutOfOrder(t *testing.T) {
closingStream,
testPayload,
}
n, _ := sesh.Obfs(f1CloseStream, obfsBuf, 0)
n, _ := sesh.obfuscate(f1CloseStream, obfsBuf, 0)
err := sesh.recvDataFromRemote(obfsBuf[:n])
if err != nil {
t.Fatalf("receiving out of order stream closing frame for stream 1: %v", err)
@ -268,7 +268,7 @@ func TestRecvDataFromRemote_Closing_OutOfOrder(t *testing.T) {
closingNothing,
testPayload,
}
n, _ = sesh.Obfs(f1, obfsBuf, 0)
n, _ = sesh.obfuscate(f1, obfsBuf, 0)
err = sesh.recvDataFromRemote(obfsBuf[:n])
if err != nil {
t.Fatalf("receiving normal frame for stream 1: %v", err)
@ -330,7 +330,7 @@ func TestParallelStreams(t *testing.T) {
wg.Add(1)
go func(frame *Frame) {
obfsBuf := make([]byte, obfsBufLen)
n, _ := sesh.Obfs(frame, obfsBuf, 0)
n, _ := sesh.obfuscate(frame, obfsBuf, 0)
obfsBuf = obfsBuf[0:n]
err := sesh.recvDataFromRemote(obfsBuf)
@ -446,7 +446,7 @@ func BenchmarkRecvDataFromRemote_Ordered(b *testing.B) {
binaryFrames := [maxIter][]byte{}
for i := 0; i < maxIter; i++ {
obfsBuf := make([]byte, obfsBufLen)
n, _ := sesh.Obfs(f, obfsBuf, 0)
n, _ := sesh.obfuscate(f, obfsBuf, 0)
binaryFrames[i] = obfsBuf[:n]
f.Seq++
}

2
internal/multiplex/stream.go
View File

@ -113,7 +113,7 @@ func (s *Stream) WriteTo(w io.Writer) (int64, error) {
}
func (s *Stream) obfuscateAndSend(buf []byte, payloadOffsetInBuf int) error {
cipherTextLen, err := s.session.Obfs(&s.writingFrame, buf, payloadOffsetInBuf)
cipherTextLen, err := s.session.obfuscate(&s.writingFrame, buf, payloadOffsetInBuf)
s.writingFrame.Seq++
if err != nil {
return err

16
internal/multiplex/stream_test.go
View File

@ -141,7 +141,7 @@ func TestStream_Close(t *testing.T) {
writingEnd := common.NewTLSConn(rawWritingEnd)
obfsBuf := make([]byte, 512)
i, _ := sesh.Obfs(dataFrame, obfsBuf, 0)
i, _ := sesh.obfuscate(dataFrame, obfsBuf, 0)
_, err := writingEnd.Write(obfsBuf[:i])
if err != nil {
t.Error("failed to write from remote end")
@ -184,7 +184,7 @@ func TestStream_Close(t *testing.T) {
writingEnd := common.NewTLSConn(rawWritingEnd)
obfsBuf := make([]byte, 512)
i, err := sesh.Obfs(dataFrame, obfsBuf, 0)
i, err := sesh.obfuscate(dataFrame, obfsBuf, 0)
if err != nil {
t.Errorf("failed to obfuscate frame %v", err)
}
@ -206,7 +206,7 @@ func TestStream_Close(t *testing.T) {
testPayload,
}
i, err = sesh.Obfs(closingFrame, obfsBuf, 0)
i, err = sesh.obfuscate(closingFrame, obfsBuf, 0)
if err != nil {
t.Errorf("failed to obfuscate frame %v", err)
}
@ -222,7 +222,7 @@ func TestStream_Close(t *testing.T) {
testPayload,
}
i, err = sesh.Obfs(closingFrameDup, obfsBuf, 0)
i, err = sesh.obfuscate(closingFrameDup, obfsBuf, 0)
if err != nil {
t.Errorf("failed to obfuscate frame %v", err)
}
@ -274,7 +274,7 @@ func TestStream_Read(t *testing.T) {
obfsBuf := make([]byte, 512)
t.Run("Plain read", func(t *testing.T) {
f.StreamID = streamID
i, _ := sesh.Obfs(f, obfsBuf, 0)
i, _ := sesh.obfuscate(f, obfsBuf, 0)
streamID++
writingEnd.Write(obfsBuf[:i])
stream, err := sesh.Accept()
@ -299,7 +299,7 @@ func TestStream_Read(t *testing.T) {
})
t.Run("Nil buf", func(t *testing.T) {
f.StreamID = streamID
i, _ := sesh.Obfs(f, obfsBuf, 0)
i, _ := sesh.obfuscate(f, obfsBuf, 0)
streamID++
writingEnd.Write(obfsBuf[:i])
stream, _ := sesh.Accept()
@ -311,7 +311,7 @@ func TestStream_Read(t *testing.T) {
})
t.Run("Read after stream close", func(t *testing.T) {
f.StreamID = streamID
i, _ := sesh.Obfs(f, obfsBuf, 0)
i, _ := sesh.obfuscate(f, obfsBuf, 0)
streamID++
writingEnd.Write(obfsBuf[:i])
stream, _ := sesh.Accept()
@ -336,7 +336,7 @@ func TestStream_Read(t *testing.T) {
})
t.Run("Read after session close", func(t *testing.T) {
f.StreamID = streamID
i, _ := sesh.Obfs(f, obfsBuf, 0)
i, _ := sesh.obfuscate(f, obfsBuf, 0)
streamID++
writingEnd.Write(obfsBuf[:i])
stream, _ := sesh.Accept()