From 7a7eeb10053f2765803bb088ab968072dd09254c Mon Sep 17 00:00:00 2001 From: Elyse Date: Sun, 10 Jul 2022 14:52:30 -0500 Subject: [PATCH] [aes] Add multiple padding modes in CBC Authored by: elyse0 --- test/test_aes.py | 37 +++++++++++++++++++++++++++++++++++++ yt_dlp/aes.py | 37 +++++++++++++++++++++++++++++++++---- 2 files changed, 70 insertions(+), 4 deletions(-) diff --git a/test/test_aes.py b/test/test_aes.py index 037246588..b26af5605 100644 --- a/test/test_aes.py +++ b/test/test_aes.py @@ -24,6 +24,8 @@ from yt_dlp.aes import ( 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 @@ class TestAES(unittest.TestCase): 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() diff --git a/yt_dlp/aes.py b/yt_dlp/aes.py index b3f504977..f9920c5b8 100644 --- a/yt_dlp/aes.py +++ b/yt_dlp/aes.py @@ -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 @@ __all__ = [ 'aes_gcm_decrypt_and_verify', 'aes_gcm_decrypt_and_verify_bytes', 'key_expansion', + 'pad_block', 'unpad_pkcs7', ]