[aes] Add support for CFB mode

devscripts/generate_aes_testdata.py

@@ -30,6 +30,10 @@ r = openssl_encode('aes-128-cbc', key, iv)
 print('aes_cbc_decrypt')
 print(repr(r))
 
+r = openssl_encode('aes-128-cfb', key, iv)
+print('aes_cfb_decrypt')
+print(repr(r))
+
 password = key
 new_key = aes_encrypt(password, key_expansion(password))
 r = openssl_encode('aes-128-ctr', new_key, iv)

test/test_aes.py

@@ -8,7 +8,7 @@ import sys
 import unittest
 sys.path.insert(0, os.path.dirname(os.path.dirname(os.path.abspath(__file__))))
 
-from youtube_dl.aes import aes_decrypt, aes_encrypt, aes_cbc_decrypt, aes_cbc_encrypt, aes_decrypt_text
+from youtube_dl.aes import aes_decrypt, aes_encrypt, aes_cbc_decrypt, aes_cbc_encrypt, aes_cfb_decrypt, aes_decrypt_text
 from youtube_dl.utils import bytes_to_intlist, intlist_to_bytes
 import base64
 
@@ -41,6 +41,13 @@ class TestAES(unittest.TestCase):
             encrypted,
             b"\x97\x92+\xe5\x0b\xc3\x18\x91ky9m&\xb3\xb5@\xe6'\xc2\x96.\xc8u\x88\xab9-[\x9e|\xf1\xcd")
 
+    def test_cfb_decrypt(self):
+        data = bytes_to_intlist(
+            b"\x03\xc7\xdd\xd4\x8e\xb3\xbc\x1a*O\xdc1\x12+8A\xbe\xa2hC\x90\xc4[t"
+        )
+        decrypted = intlist_to_bytes(aes_cfb_decrypt(data, self.key, self.iv))
+        self.assertEqual(decrypted, self.secret_msg)
+
     def test_decrypt_text(self):
         password = intlist_to_bytes(self.key).decode('utf-8')
         encrypted = base64.b64encode(

youtube_dl/aes.py

@@ -88,6 +88,32 @@ def aes_cbc_encrypt(data, key, iv):
     return encrypted_data
 
 
+def aes_cfb_decrypt(data, key, iv):
+    """
+    Decrypt with aes in ciphed feedback mode
+
+    @param {int[]} data        cipher
+    @param {int[]} key         16/24/32-Byte cipher key
+    @param {int[]} iv          16-Byte IV
+    @returns {int[]}           decrypted data
+    """
+    expanded_key = key_expansion(key)
+    block_count = int(ceil(float(len(data)) / BLOCK_SIZE_BYTES))
+
+    decrypted_data = []
+    previous_cipher_block = iv
+    for i in range(block_count):
+        block = data[i * BLOCK_SIZE_BYTES: (i + 1) * BLOCK_SIZE_BYTES]
+        block += [0] * (BLOCK_SIZE_BYTES - len(block))
+
+        encrypted_vector = aes_encrypt(previous_cipher_block, expanded_key)
+        decrypted_data += xor(block, encrypted_vector)
+        previous_cipher_block = block
+    decrypted_data = decrypted_data[:len(data)]
+
+    return decrypted_data
+
+
 def key_expansion(data):
     """
     Generate key schedule