From 274e16ac660cf1875a5f38448f2475d3de0bfa5c Mon Sep 17 00:00:00 2001
From: Lonami Exo <totufals@hotmail.com>
Date: Sun, 20 Aug 2017 01:23:57 +0200
Subject: [PATCH] Avoid defining Python's AES class if libssl's is available

---
 telethon/crypto/aes.py | 142 +++++++++++++++++++++--------------------
 1 file changed, 72 insertions(+), 70 deletions(-)

diff --git a/telethon/crypto/aes.py b/telethon/crypto/aes.py
index cf0994dc..9bc1ba95 100644
--- a/telethon/crypto/aes.py
+++ b/telethon/crypto/aes.py
@@ -2,76 +2,78 @@ import os
 import pyaes
 from . import libssl
 
-class AES:
-    @staticmethod
-    def decrypt_ige(cipher_text, key, iv):
-        """Decrypts the given text in 16-bytes blocks by using the
-           given key and 32-bytes initialization vector
-        """
-        iv1 = iv[:len(iv) // 2]
-        iv2 = iv[len(iv) // 2:]
 
-        aes = pyaes.AES(key)
-
-        plain_text = []
-        blocks_count = len(cipher_text) // 16
-
-        cipher_text_block = [0] * 16
-        for block_index in range(blocks_count):
-            for i in range(16):
-                cipher_text_block[i] = \
-                    cipher_text[block_index * 16 + i] ^ iv2[i]
-
-            plain_text_block = aes.decrypt(cipher_text_block)
-
-            for i in range(16):
-                plain_text_block[i] ^= iv1[i]
-
-            iv1 = cipher_text[block_index * 16:block_index * 16 + 16]
-            iv2 = plain_text_block
-
-            plain_text.extend(plain_text_block)
-
-        return bytes(plain_text)
-
-    @staticmethod
-    def encrypt_ige(plain_text, key, iv):
-        """Encrypts the given text in 16-bytes blocks by using the
-           given key and 32-bytes initialization vector
-        """
-
-        # Add random padding iff it's not evenly divisible by 16 already
-        if len(plain_text) % 16 != 0:
-            padding_count = 16 - len(plain_text) % 16
-            plain_text += os.urandom(padding_count)
-
-        iv1 = iv[:len(iv) // 2]
-        iv2 = iv[len(iv) // 2:]
-
-        aes = pyaes.AES(key)
-
-        cipher_text = []
-        blocks_count = len(plain_text) // 16
-
-        for block_index in range(blocks_count):
-            plain_text_block = list(
-                plain_text[block_index * 16:block_index * 16 + 16]
-            )
-            for i in range(16):
-                plain_text_block[i] ^= iv1[i]
-
-            cipher_text_block = aes.encrypt(plain_text_block)
-
-            for i in range(16):
-                cipher_text_block[i] ^= iv2[i]
-
-            iv1 = cipher_text_block
-            iv2 = plain_text[block_index * 16:block_index * 16 + 16]
-
-            cipher_text.extend(cipher_text_block)
-
-        return bytes(cipher_text)
-
-# use libssl if available
 if libssl.libssl:
+    # Use libssl if available, since it will be faster
     AES = libssl.AES
+else:
+    # Fallback to a pure Python implementation
+    class AES:
+        @staticmethod
+        def decrypt_ige(cipher_text, key, iv):
+            """Decrypts the given text in 16-bytes blocks by using the
+               given key and 32-bytes initialization vector
+            """
+            iv1 = iv[:len(iv) // 2]
+            iv2 = iv[len(iv) // 2:]
+
+            aes = pyaes.AES(key)
+
+            plain_text = []
+            blocks_count = len(cipher_text) // 16
+
+            cipher_text_block = [0] * 16
+            for block_index in range(blocks_count):
+                for i in range(16):
+                    cipher_text_block[i] = \
+                        cipher_text[block_index * 16 + i] ^ iv2[i]
+
+                plain_text_block = aes.decrypt(cipher_text_block)
+
+                for i in range(16):
+                    plain_text_block[i] ^= iv1[i]
+
+                iv1 = cipher_text[block_index * 16:block_index * 16 + 16]
+                iv2 = plain_text_block
+
+                plain_text.extend(plain_text_block)
+
+            return bytes(plain_text)
+
+        @staticmethod
+        def encrypt_ige(plain_text, key, iv):
+            """Encrypts the given text in 16-bytes blocks by using the
+               given key and 32-bytes initialization vector
+            """
+
+            # Add random padding iff it's not evenly divisible by 16 already
+            if len(plain_text) % 16 != 0:
+                padding_count = 16 - len(plain_text) % 16
+                plain_text += os.urandom(padding_count)
+
+            iv1 = iv[:len(iv) // 2]
+            iv2 = iv[len(iv) // 2:]
+
+            aes = pyaes.AES(key)
+
+            cipher_text = []
+            blocks_count = len(plain_text) // 16
+
+            for block_index in range(blocks_count):
+                plain_text_block = list(
+                    plain_text[block_index * 16:block_index * 16 + 16]
+                )
+                for i in range(16):
+                    plain_text_block[i] ^= iv1[i]
+
+                cipher_text_block = aes.encrypt(plain_text_block)
+
+                for i in range(16):
+                    cipher_text_block[i] ^= iv2[i]
+
+                iv1 = cipher_text_block
+                iv2 = plain_text[block_index * 16:block_index * 16 + 16]
+
+                cipher_text.extend(cipher_text_block)
+
+            return bytes(cipher_text)