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[aes] Add multiple padding modes in CBC

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Authored by: elyse0
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Elyse 2022-07-10 14:52:30 -05:00 committed by pukkandan
parent 4e7f375c94
commit 7a7eeb1005
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2 changed files with 70 additions and 4 deletions
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37
test/test_aes.py
View file

@ -24,6 +24,8 @@
aes_encrypt,
aes_gcm_decrypt_and_verify,
aes_gcm_decrypt_and_verify_bytes,
key_expansion,
pad_block,
)
from yt_dlp.dependencies import Cryptodome_AES
from yt_dlp.utils import bytes_to_intlist, intlist_to_bytes
@ -112,6 +114,41 @@ def test_ecb_decrypt(self):
decrypted = intlist_to_bytes(aes_ecb_decrypt(data, self.key, self.iv))
self.assertEqual(decrypted.rstrip(b'\x08'), self.secret_msg)
def test_key_expansion(self):
key = '4f6bdaa39e2f8cb07f5e722d9edef314'
self.assertEqual(key_expansion(bytes_to_intlist(bytearray.fromhex(key))), [
0x4F, 0x6B, 0xDA, 0xA3, 0x9E, 0x2F, 0x8C, 0xB0, 0x7F, 0x5E, 0x72, 0x2D, 0x9E, 0xDE, 0xF3, 0x14,
0x53, 0x66, 0x20, 0xA8, 0xCD, 0x49, 0xAC, 0x18, 0xB2, 0x17, 0xDE, 0x35, 0x2C, 0xC9, 0x2D, 0x21,
0x8C, 0xBE, 0xDD, 0xD9, 0x41, 0xF7, 0x71, 0xC1, 0xF3, 0xE0, 0xAF, 0xF4, 0xDF, 0x29, 0x82, 0xD5,
0x2D, 0xAD, 0xDE, 0x47, 0x6C, 0x5A, 0xAF, 0x86, 0x9F, 0xBA, 0x00, 0x72, 0x40, 0x93, 0x82, 0xA7,
0xF9, 0xBE, 0x82, 0x4E, 0x95, 0xE4, 0x2D, 0xC8, 0x0A, 0x5E, 0x2D, 0xBA, 0x4A, 0xCD, 0xAF, 0x1D,
0x54, 0xC7, 0x26, 0x98, 0xC1, 0x23, 0x0B, 0x50, 0xCB, 0x7D, 0x26, 0xEA, 0x81, 0xB0, 0x89, 0xF7,
0x93, 0x60, 0x4E, 0x94, 0x52, 0x43, 0x45, 0xC4, 0x99, 0x3E, 0x63, 0x2E, 0x18, 0x8E, 0xEA, 0xD9,
0xCA, 0xE7, 0x7B, 0x39, 0x98, 0xA4, 0x3E, 0xFD, 0x01, 0x9A, 0x5D, 0xD3, 0x19, 0x14, 0xB7, 0x0A,
0xB0, 0x4E, 0x1C, 0xED, 0x28, 0xEA, 0x22, 0x10, 0x29, 0x70, 0x7F, 0xC3, 0x30, 0x64, 0xC8, 0xC9,
0xE8, 0xA6, 0xC1, 0xE9, 0xC0, 0x4C, 0xE3, 0xF9, 0xE9, 0x3C, 0x9C, 0x3A, 0xD9, 0x58, 0x54, 0xF3,
0xB4, 0x86, 0xCC, 0xDC, 0x74, 0xCA, 0x2F, 0x25, 0x9D, 0xF6, 0xB3, 0x1F, 0x44, 0xAE, 0xE7, 0xEC])
def test_pad_block(self):
block = [0x21, 0xA0, 0x43, 0xFF]
self.assertEqual(pad_block(block, 'pkcs7'),
block + [0x0C, 0x0C, 0x0C, 0x0C, 0x0C, 0x0C, 0x0C, 0x0C, 0x0C, 0x0C, 0x0C, 0x0C])
self.assertEqual(pad_block(block, 'iso7816'),
block + [0x80, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00])
self.assertEqual(pad_block(block, 'whitespace'),
block + [0x20, 0x20, 0x20, 0x20, 0x20, 0x20, 0x20, 0x20, 0x20, 0x20, 0x20, 0x20])
self.assertEqual(pad_block(block, 'zero'),
block + [0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00])
block = list(range(16))
for mode in ('pkcs7', 'iso7816', 'whitespace', 'zero'):
self.assertEqual(pad_block(block, mode), block, mode)
if __name__ == '__main__':
unittest.main()

37
yt_dlp/aes.py
View file

@ -31,6 +31,33 @@ def unpad_pkcs7(data):
BLOCK_SIZE_BYTES = 16
def pad_block(block, padding_mode):
"""
Pad a block with the given padding mode
@param {int[]} block block to pad
@param padding_mode padding mode
"""
padding_size = BLOCK_SIZE_BYTES - len(block)
PADDING_BYTE = {
'pkcs7': padding_size,
'iso7816': 0x0,
'whitespace': 0x20,
'zero': 0x0,
}
if padding_size < 0:
raise ValueError('Block size exceeded')
elif padding_mode not in PADDING_BYTE:
raise NotImplementedError(f'Padding mode {padding_mode} is not implemented')
if padding_mode == 'iso7816' and padding_size:
block = block + [0x80] # NB: += mutates list
padding_size -= 1
return block + [PADDING_BYTE[padding_mode]] * padding_size
def aes_ecb_encrypt(data, key, iv=None):
"""
Encrypt with aes in ECB mode
@ -137,13 +164,14 @@ def aes_cbc_decrypt(data, key, iv):
return decrypted_data
def aes_cbc_encrypt(data, key, iv):
def aes_cbc_encrypt(data, key, iv, padding_mode='pkcs7'):
"""
Encrypt with aes in CBC mode. Using PKCS#7 padding
Encrypt with aes in CBC mode
@param {int[]} data cleartext
@param {int[]} key 16/24/32-Byte cipher key
@param {int[]} iv 16-Byte IV
@param padding_mode Padding mode to use
@returns {int[]} encrypted data
"""
expanded_key = key_expansion(key)
@ -153,8 +181,8 @@ def aes_cbc_encrypt(data, key, iv):
previous_cipher_block = iv
for i in range(block_count):
block = data[i * BLOCK_SIZE_BYTES: (i + 1) * BLOCK_SIZE_BYTES]
remaining_length = BLOCK_SIZE_BYTES - len(block)
block += [remaining_length] * remaining_length
block = pad_block(block, padding_mode)
mixed_block = xor(block, previous_cipher_block)
encrypted_block = aes_encrypt(mixed_block, expanded_key)
@ -510,5 +538,6 @@ def ghash(subkey, data):
'aes_gcm_decrypt_and_verify',
'aes_gcm_decrypt_and_verify_bytes',
'key_expansion',
'pad_block',
'unpad_pkcs7',
]