Working version

obfuscated2/obfuscated2.go

@@ -0,0 +1,79 @@
+package obfuscated2
+
+import (
+	"crypto/aes"
+	"crypto/cipher"
+	"crypto/sha256"
+
+	"github.com/juju/errors"
+)
+
+type Obfuscated2 struct {
+	decryptor cipher.Stream
+	encryptor cipher.Stream
+}
+
+func (o *Obfuscated2) Encrypt(data []byte) []byte {
+	buf := make([]byte, len(data))
+	o.encryptor.XORKeyStream(buf, data)
+	return buf
+}
+
+func (o *Obfuscated2) Decrypt(data []byte) []byte {
+	buf := make([]byte, len(data))
+	o.decryptor.XORKeyStream(buf, data)
+	return buf
+}
+
+func ParseObfuscated2ClientFrame(secret, data []byte) (*Obfuscated2, int16, error) {
+	frame := Frame(data)
+
+	decHasher := sha256.New()
+	decHasher.Write(frame.Key())
+	decHasher.Write(secret)
+	decryptor := makeStreamCipher(decHasher.Sum(nil), frame.IV())
+
+	invertedFrame := frame.Invert()
+	encHasher := sha256.New()
+	encHasher.Write(invertedFrame.Key())
+	encHasher.Write(secret)
+	encryptor := makeStreamCipher(encHasher.Sum(nil), invertedFrame.IV())
+
+	decryptedFrame := make(Frame, FrameLen)
+	decryptor.XORKeyStream(decryptedFrame, frame)
+	if !decryptedFrame.Valid() {
+		return nil, 0, errors.New("Unknown protocol")
+	}
+
+	obfs := &Obfuscated2{
+		decryptor: decryptor,
+		encryptor: encryptor,
+	}
+
+	return obfs, decryptedFrame.DC(), nil
+}
+
+func MakeTelegramObfuscated2Frame() (*Obfuscated2, Frame) {
+	frame := generateFrame()
+
+	encryptor := makeStreamCipher(frame.Key(), frame.IV())
+	decryptorFrame := frame.Invert()
+	decryptor := makeStreamCipher(decryptorFrame.Key(), decryptorFrame.IV())
+
+	copyFrame := make(Frame, frameOffsetIV)
+	copy(copyFrame, frame)
+	encryptor.XORKeyStream(frame, frame)
+	copy(frame, copyFrame)
+
+	obfs := &Obfuscated2{
+		decryptor: decryptor,
+		encryptor: encryptor,
+	}
+
+	return obfs, frame
+}
+
+func makeStreamCipher(key, iv []byte) cipher.Stream {
+	block, _ := aes.NewCipher(key)
+	return cipher.NewCTR(block, iv)
+}