Make the Connection a proper ABC (#509)

telethon/network/connection/tcpobfuscated.py

@@ -0,0 +1,50 @@
+import os
+from datetime import timedelta
+
+from .tcpfull import ConnectionTcpFull
+from .tcpabridged import ConnectionTcpAbridged
+from ...crypto import AESModeCTR
+
+
+class ConnectionTcpObfuscated(ConnectionTcpAbridged):
+    """
+    Encodes the packet just like `ConnectionTcpAbridged`, but encrypts
+    every message with a randomly generated key using the
+    AES-CTR mode so the packets are harder to discern.
+    """
+    def __init__(self, proxy=None, timeout=timedelta(seconds=5)):
+        super().__init__(proxy, timeout)
+        self._aes_encrypt, self._aes_decrypt = None, None
+        self.read = lambda s: self._aes_decrypt.encrypt(self.conn.read(s))
+        self.write = lambda d: self.conn.write(self._aes_encrypt.encrypt(d))
+
+    def connect(self, ip, port):
+        result = ConnectionTcpFull.connect(self, ip, port)
+        # Obfuscated messages secrets cannot start with any of these
+        keywords = (b'PVrG', b'GET ', b'POST', b'\xee' * 4)
+        while True:
+            random = os.urandom(64)
+            if (random[0] != b'\xef' and
+                    random[:4] not in keywords and
+                    random[4:4] != b'\0\0\0\0'):
+                break
+
+        random = list(random)
+        random[56] = random[57] = random[58] = random[59] = 0xef
+        random_reversed = random[55:7:-1]  # Reversed (8, len=48)
+
+        # encryption has "continuous buffer" enabled
+        encrypt_key = bytes(random[8:40])
+        encrypt_iv = bytes(random[40:56])
+        decrypt_key = bytes(random_reversed[:32])
+        decrypt_iv = bytes(random_reversed[32:48])
+
+        self._aes_encrypt = AESModeCTR(encrypt_key, encrypt_iv)
+        self._aes_decrypt = AESModeCTR(decrypt_key, decrypt_iv)
+
+        random[56:64] = self._aes_encrypt.encrypt(bytes(random))[56:64]
+        self.conn.write(bytes(random))
+        return result
+
+    def clone(self):
+        return ConnectionTcpObfuscated(self._proxy, self._timeout)