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fix: reqTimeout misuse in MakeRequest + hk_lm level MTProxy ClientHello obfuscation #308

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fix: reqTimeout misuse in MakeRequest + hk_lm level MTProxy ClientHello obfuscation #308

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222 changes: 193 additions & 29 deletions internal/transport/mtproxy.go
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Original file line number Diff line number Diff line change
Expand Up @@ -317,10 +317,10 @@ func (m *mtproxyConn) SetDeadline(t time.Time) error { return m.conn.SetDea
func (m *mtproxyConn) SetReadDeadline(t time.Time) error { return m.conn.SetReadDeadline(t) }
func (m *mtproxyConn) SetWriteDeadline(t time.Time) error { return m.conn.SetWriteDeadline(t) }

// Fake TLS ClientHello generation
// Fake TLS ClientHello generation (hk_lm level obfuscation)
var (
keyMod = new(big.Int).Sub(new(big.Int).Exp(big.NewInt(2), big.NewInt(255), nil), big.NewInt(19))
quadResPow = new(big.Int).Div(new(big.Int).Sub(keyMod, big.NewInt(1)), big.NewInt(4))
quadResPow = new(big.Int).Div(new(big.Int).Sub(keyMod, big.NewInt(1)), new(big.Int).SetInt64(4))
)

type tlsHelloWriter struct {
Expand All @@ -332,19 +332,54 @@ type tlsHelloWriter struct {
}

func generateFakeTlsHello(domain, secret []byte) []byte {
w := &tlsHelloWriter{buf: make([]byte, 517), domain: domain, grease: initGrease(7)}

w.writeBytes([]byte{0x16, 0x03, 0x01, 0x02, 0x00, 0x01, 0x00, 0x01, 0xFC, 0x03, 0x03})
minPad, maxPad := 100, 400
padSize := minPad + int(binary.LittleEndian.Uint16(secret[:2]))%(maxPad-minPad+1)
padSize = (padSize + 15) & ^15

// Build the ClientHello body first, then wrap with proper length headers
w := &tlsHelloWriter{buf: make([]byte, 1024), domain: domain, grease: initGrease(10)}

// Reserve space for record + handshake headers (will fill in later)
// Record Layer: 5 bytes (0x16 0x03 0x01 + 2 length)
// Handshake: 4 bytes (0x01 + 3 length)
// Client Version: 2 bytes
// Write static header bytes, length fields filled later
w.buf[0] = 0x16
w.buf[1] = 0x03
w.buf[2] = 0x01
w.buf[5] = 0x01
w.buf[9] = 0x03
w.buf[10] = 0x03
w.pos = 11

// Random: 32 bytes (zeros, filled with HMAC later)
w.writeZero(32)

// Session ID: 32 random bytes
w.writeBytes([]byte{0x20})
w.writeRandom(32)

w.writeBytes([]byte{0x00, 0x20})
// Cipher Suites: length + list
w.writeBytes([]byte{0x00, 0x24})
w.writeGrease(0)
w.writeBytes([]byte{0x13, 0x01, 0x13, 0x02, 0x13, 0x03, 0xC0, 0x2B, 0xC0, 0x2F, 0xC0, 0x2C, 0xC0, 0x30, 0xCC, 0xA9, 0xCC, 0xA8, 0xC0, 0x13, 0xC0, 0x14, 0x00, 0x9C, 0x00, 0x9D, 0x00, 0x2F, 0x00, 0x35, 0x01, 0x00, 0x01, 0x93})
w.writeBytes([]byte{0x13, 0x01, 0x13, 0x02, 0x13, 0x03})
w.writeGrease(1)
w.writeBytes([]byte{0xC0, 0x2B, 0xC0, 0x2F, 0xC0, 0x2C, 0xC0, 0x30, 0xCC, 0xA9, 0xCC, 0xA8})
w.writeGrease(2)
w.writeBytes([]byte{0x00, 0x00, 0x00, 0x00})
w.writeBytes([]byte{0xC0, 0x13, 0xC0, 0x14, 0x00, 0x9C, 0x00, 0x9D, 0x00, 0x2F, 0x00, 0x35})
w.writeGrease(3)

// Compression Methods: null only
w.writeBytes([]byte{0x01, 0x00})

// Extensions
w.beginScope()

// Grease extension
w.writeGreaseExt(4)

// SNI
w.writeBytes([]byte{0x00, 0x00})
w.beginScope()
w.beginScope()
w.writeBytes([]byte{0x00})
Expand All @@ -354,31 +389,109 @@ func generateFakeTlsHello(domain, secret []byte) []byte {
w.endScope()
w.endScope()

w.writeBytes([]byte{0x00, 0x17, 0x00, 0x00, 0xFF, 0x01, 0x00, 0x01, 0x00, 0x00, 0x0A, 0x00, 0x0A, 0x00, 0x08})
w.writeGrease(4)
w.writeBytes([]byte{0x00, 0x1D, 0x00, 0x17, 0x00, 0x18, 0x00, 0x0B, 0x00, 0x02, 0x01, 0x00, 0x00, 0x23, 0x00, 0x00, 0x00, 0x10, 0x00, 0x0E, 0x00, 0x0C, 0x02, 0x68, 0x32, 0x08, 0x68, 0x74, 0x74, 0x70, 0x2F, 0x31, 0x2E, 0x31, 0x00, 0x05, 0x00, 0x05, 0x01, 0x00, 0x00, 0x00, 0x00, 0x00, 0x0D, 0x00, 0x12, 0x00, 0x10, 0x04, 0x03, 0x08, 0x04, 0x04, 0x01, 0x05, 0x03, 0x08, 0x05, 0x05, 0x01, 0x08, 0x06, 0x06, 0x01, 0x00, 0x12, 0x00, 0x00, 0x00, 0x33, 0x00, 0x2B, 0x00, 0x29})
w.writeGrease(4)
w.writeBytes([]byte{0x00, 0x01, 0x00, 0x00, 0x1D, 0x00, 0x20})
w.writeKey()
w.writeBytes([]byte{0x00, 0x2D, 0x00, 0x02, 0x01, 0x01, 0x00, 0x2B, 0x00, 0x0B, 0x0A})
w.writeGrease(6)
w.writeBytes([]byte{0x03, 0x04, 0x03, 0x03, 0x03, 0x02, 0x03, 0x01, 0x00, 0x1B, 0x00, 0x03, 0x02, 0x00, 0x02})
w.writeGrease(3)
w.writeBytes([]byte{0x00, 0x01, 0x00, 0x00, 0x15})
// Extended Master Secret
w.writeBytes([]byte{0x00, 0x17, 0x00, 0x00})

// Renegotiation Info
w.writeBytes([]byte{0xFF, 0x01, 0x00, 0x01, 0x00})

// Grease extension
w.writeGreaseExt(5)

// Supported Groups (with grease)
w.writeBytes([]byte{0x00, 0x0A})
w.beginScope()
w.writeGreaseInScope(6)
w.writeBytes([]byte{0x00, 0x1D, 0x00, 0x17, 0x00, 0x18, 0x01, 0x00})
w.writeGreaseInScope(7)
w.endScope()

// EC Point Formats
w.writeBytes([]byte{0x00, 0x0B, 0x00, 0x02, 0x01, 0x00})

// Session Ticket
w.writeBytes([]byte{0x00, 0x23, 0x00, 0x00})

// ALPN
w.writeBytes([]byte{0x00, 0x10})
w.beginScope()
w.beginScope()
w.writeBytes([]byte{0x02, 0x68, 0x32, 0x08, 0x68, 0x74, 0x74, 0x70, 0x2F, 0x31, 0x2E, 0x31})
w.endScope()
w.endScope()

// Grease extension
w.writeGreaseExt(8)

// Status Request
w.writeBytes([]byte{0x00, 0x05, 0x00, 0x05, 0x01, 0x00, 0x00, 0x00, 0x00})

// Signed Certificate Timestamps
w.writeBytes([]byte{0x00, 0x12, 0x00, 0x00})

// Signature Algorithms
w.writeBytes([]byte{0x00, 0x0D})
w.beginScope()
w.writeBytes([]byte{0x04, 0x03, 0x08, 0x04, 0x04, 0x01, 0x05, 0x03, 0x08, 0x05, 0x05, 0x01, 0x08, 0x06, 0x06, 0x01, 0x02, 0x01})
w.endScope()

// PSK Key Exchange Modes
w.writeBytes([]byte{0x00, 0x2D, 0x00, 0x02, 0x01, 0x01})

// Key Share: X25519 + P-256
w.writeBytes([]byte{0x00, 0x33})
w.beginScope()
w.writeBytes([]byte{0x00, 0x1D, 0x00, 0x20})
w.writeX25519Key()
w.writeBytes([]byte{0x00, 0x17, 0x00, 0x41})
w.writeP256Key()
w.endScope()

// Supported Versions
w.writeBytes([]byte{0x00, 0x2B})
w.beginScope()
w.writeBytes([]byte{0x03, 0x03, 0x03, 0x03, 0x03, 0x02, 0x03, 0x01})
w.endScope()

padSize := 515 - w.pos
// Grease extension
w.writeGreaseExt(9)

// Compress Certificate
w.writeBytes([]byte{0x00, 0x1B, 0x00, 0x03, 0x02, 0x00, 0x02})

// Application Settings (h2)
w.writeBytes([]byte{0x17, 0x5D})
w.beginScope()
w.beginScope()
w.writeBytes([]byte{0x02, 0x68, 0x32})
w.endScope()
w.endScope()

// Padding
w.writeBytes([]byte{0x00, 0x15})
w.beginScope()
w.writeZero(padSize)
w.endScope()

w.endScope()

// Fill in length fields now that we know the final size
recordLen := w.pos - 5
handshakeMsgLen := w.pos - 9
binary.BigEndian.PutUint16(w.buf[3:5], uint16(recordLen))
w.buf[6] = byte(handshakeMsgLen >> 16)
w.buf[7] = byte(handshakeMsgLen >> 8)
w.buf[8] = byte(handshakeMsgLen)

// Compute HMAC-SHA256 over the ClientHello and embed in random field
mac := hmac.New(sha256.New, secret)
mac.Write(w.buf)
mac.Write(w.buf[:w.pos])
hash := mac.Sum(nil)
ts := uint32(time.Now().Unix())
binary.LittleEndian.PutUint32(hash[28:], binary.LittleEndian.Uint32(hash[28:])^ts)
copy(w.buf[11:], hash)
copy(w.buf[11:43], hash)

return w.buf
return w.buf[:w.pos]
}

func initGrease(size int) []byte {
Expand All @@ -395,21 +508,63 @@ func initGrease(size int) []byte {
return buf
}

func (w *tlsHelloWriter) writeBytes(data []byte) { copy(w.buf[w.pos:], data); w.pos += len(data) }
func (w *tlsHelloWriter) writeRandom(n int) { rand.Read(w.buf[w.pos : w.pos+n]); w.pos += n }
func (w *tlsHelloWriter) writeZero(n int) { w.pos += n }
func (w *tlsHelloWriter) writeBytes(data []byte) {
copy(w.buf[w.pos:], data)
w.pos += len(data)
}

func (w *tlsHelloWriter) writeRandom(n int) {
rand.Read(w.buf[w.pos : w.pos+n])
w.pos += n
}

func (w *tlsHelloWriter) writeZero(n int) {
w.pos += n
}

func (w *tlsHelloWriter) writeUint16(v uint16) {
binary.BigEndian.PutUint16(w.buf[w.pos:], v)
w.pos += 2
}

func (w *tlsHelloWriter) writeUint24(v uint32) {
w.buf[w.pos] = byte(v >> 16)
w.buf[w.pos+1] = byte(v >> 8)
w.buf[w.pos+2] = byte(v)
w.pos += 3
}

func (w *tlsHelloWriter) writeGrease(seed int) {
w.buf[w.pos], w.buf[w.pos+1] = w.grease[seed], w.grease[seed]
g := w.grease[seed]
w.buf[w.pos], w.buf[w.pos+1] = g, g
w.pos += 2
}

func (w *tlsHelloWriter) writeGreaseExt(seed int) {
g := w.grease[seed]
binary.BigEndian.PutUint16(w.buf[w.pos:], uint16(g)<<8|uint16(g))
w.pos += 2
w.writeUint16(0)
}

func (w *tlsHelloWriter) writeGreaseInScope(seed int) {
g := w.grease[seed]
w.buf[w.pos], w.buf[w.pos+1] = g, g
w.pos += 2
}

func (w *tlsHelloWriter) beginScope() {
w.scopes = append(w.scopes, w.pos)
w.pos += 2
}
func (w *tlsHelloWriter) beginScope() { w.scopes = append(w.scopes, w.pos); w.pos += 2 }

func (w *tlsHelloWriter) endScope() {
begin := w.scopes[len(w.scopes)-1]
w.scopes = w.scopes[:len(w.scopes)-1]
binary.BigEndian.PutUint16(w.buf[begin:], uint16(w.pos-begin-2))
}

func (w *tlsHelloWriter) writeKey() {
func (w *tlsHelloWriter) writeX25519Key() {
for {
key := make([]byte, 32)
rand.Read(key)
Expand All @@ -426,6 +581,15 @@ func (w *tlsHelloWriter) writeKey() {
}
}

func (w *tlsHelloWriter) writeP256Key() {
// Generate an uncompressed EC point on P-256
key := make([]byte, 65)
key[0] = 0x04
rand.Read(key[1:])
key[65-32] &= 0x7F
w.writeBytes(key)
}

func getY2(x *big.Int) *big.Int {
y := new(big.Int).Set(x)
y.Add(y, big.NewInt(486662)).Mod(y, keyMod)
Expand Down
6 changes: 6 additions & 0 deletions mtproto.go
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Original file line number Diff line number Diff line change
Expand Up @@ -874,6 +874,12 @@ func (m *MTProto) makeRequestCtxWithDepth(ctx context.Context, data tl.Object, r
m.Logger.Debug("5 consecutive timeouts in %ds (request=%T, tcp_active=%v, retryDepth=%d); reconnecting", duration, data, m.tcpState.GetActive(), retryDepth)
m.connState.ConsecutiveTimeouts.Store(0)
m.tryReconnect()
if retryDepth < m.maxRetryDepth {
m.Logger.Trace("retrying request after reconnect (depth=%d/%d)", retryDepth+1, m.maxRetryDepth)
retryCtx, cancel := context.WithTimeout(context.Background(), m.reqTimeout)
defer cancel()
return m.makeRequestCtxWithDepth(retryCtx, data, retryDepth+1, expectedTypes...)
}
} else {
m.Logger.Debug("5 consecutive timeouts in %ds (slow accumulation); resetting counter", duration)
m.connState.ConsecutiveTimeouts.Store(0)
Expand Down
4 changes: 2 additions & 2 deletions network.go
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Original file line number Diff line number Diff line change
Expand Up @@ -184,8 +184,8 @@ func (m *MTProto) SetAuthKey(key []byte) {
}

func (m *MTProto) MakeRequest(msg tl.Object) (any, error) {
if m.connConfig.Timeout > 0 {
ctx, cancel := context.WithTimeout(context.Background(), m.connConfig.Timeout)
if m.reqTimeout > 0 {
ctx, cancel := context.WithTimeout(context.Background(), m.reqTimeout)
defer cancel()
return m.makeRequestCtx(ctx, msg)
}
Expand Down