Direct proxy works

_obfuscated2/obfuscated2.go

@@ -0,0 +1,81 @@
+package obfuscated2
+
+import (
+	"crypto/aes"
+	"crypto/cipher"
+	"crypto/sha256"
+
+	"github.com/juju/errors"
+
+	"github.com/9seconds/mtg/mtproto"
+)
+
+// Obfuscated2 contains AES CTR encryption and decryption streams
+// for telegram connection.
+type Obfuscated2 struct {
+	Decryptor cipher.Stream
+	Encryptor cipher.Stream
+}
+
+// ParseObfuscated2ClientFrame parses client frame. Please check this link for
+// details: http://telegra.ph/telegram-blocks-wtf-05-26
+//
+// Beware, link above is in russian.
+func ParseObfuscated2ClientFrame(secret []byte, frame Frame) (*Obfuscated2, *mtproto.ConnectionOpts, error) {
+	decHasher := sha256.New()
+	decHasher.Write(frame.Key()) // nolint: errcheck, gosec
+	decHasher.Write(secret)      // nolint: errcheck, gosec
+	decryptor := makeStreamCipher(decHasher.Sum(nil), frame.IV())
+
+	invertedFrame := frame.Invert()
+	encHasher := sha256.New()
+	encHasher.Write(invertedFrame.Key()) // nolint: errcheck, gosec
+	encHasher.Write(secret)              // nolint: errcheck, gosec
+	encryptor := makeStreamCipher(encHasher.Sum(nil), invertedFrame.IV())
+
+	decryptedFrame := make(Frame, FrameLen)
+	decryptor.XORKeyStream(decryptedFrame, frame)
+	connType, err := decryptedFrame.ConnectionType()
+	if err != nil {
+		return nil, nil, errors.Annotate(err, "Unknown protocol")
+	}
+
+	obfs := &Obfuscated2{
+		Decryptor: decryptor,
+		Encryptor: encryptor,
+	}
+	connOpts := &mtproto.ConnectionOpts{
+		DC:             decryptedFrame.DC(),
+		ConnectionType: connType,
+	}
+
+	return obfs, connOpts, nil
+}
+
+// MakeTelegramObfuscated2Frame creates new handshake frame to send to
+// Telegram.
+// https://blog.susanka.eu/how-telegram-obfuscates-its-mtproto-traffic/
+func MakeTelegramObfuscated2Frame(opts *mtproto.ConnectionOpts) (*Obfuscated2, Frame) {
+	frame := generateFrame(opts.ConnectionType)
+
+	encryptor := makeStreamCipher(frame.Key(), frame.IV())
+	decryptorFrame := frame.Invert()
+	decryptor := makeStreamCipher(decryptorFrame.Key(), decryptorFrame.IV())
+
+	copyFrame := make(Frame, FrameLen)
+	copy(copyFrame[:frameOffsetIV], frame[:frameOffsetIV])
+	encryptor.XORKeyStream(frame, frame)
+	copy(frame[:frameOffsetIV], copyFrame[:frameOffsetIV])
+
+	obfs := &Obfuscated2{
+		Decryptor: decryptor,
+		Encryptor: encryptor,
+	}
+
+	return obfs, frame
+}
+
+func makeStreamCipher(key, iv []byte) cipher.Stream {
+	block, _ := aes.NewCipher(key) // nolint: gosec
+	return cipher.NewCTR(block, iv)
+}