def __init__(self, io: IO, encrypt_password: bytes, total_origin_len: int):
self._io = io
# The length of unencrypted content of `self._io`
self._io_len = total_len(self._io)
# The offset of encrypted content of `self._io`
self._offset = 0
# The total length of all original (decrypted) content
#
# Only define it at __init__
self._total_origin_len = total_origin_len
self._encrypt_password = encrypt_password
self._salt_for_head = generate_salt()
self._encrypt_key_for_head, self._iv_for_head = generate_key_iv(
encrypt_password, self._salt_for_head, 32, 16)
# `self._encrypt_key`,`self._nonce_or_iv` is for cryptography
self._salt = generate_salt()
self._encrypt_key, self._nonce_or_iv = generate_key_iv(
encrypt_password, self._salt, 32, 16)
# Cryptography
#
# Instantiated at each subclass, here is for mypy
self._crypto: Optional[Cryptography] = None
self._total_head = None
self._total_head_len = len(self.total_head)
def test_generate_key_iv():
pwd = b"test"
salt = b"\xf6\x81\x8c\xae\x13\x18r\xbd"
key, iv = generate_key_iv(pwd, salt, 32, 16)
assert (
key ==
b"l\x04\xcb\xae\xc4\xd7\xa05^\x04\x93\xa2M\xe5\x0ee\\?\xc1C;\xca\xab|Z\xda\x98\xe8\xdb\x01\xdb\xa0"
)
assert iv == b"\x8b\xe2\x02\x8e\xee6j\x1cLv\xa2&\xa2\x8a\x1d\xfd"
def _decryptio_version3(total_head: bytes, io: IO,
encrypt_password: bytes) -> Optional[DecryptIO]:
if len(total_head) < PADDED_ENCRYPT_HEAD_WITH_SALT_LEN:
return
enc_head, salt_for_head = (
total_head[:PADDED_ENCRYPT_HEAD_LEN],
total_head[PADDED_ENCRYPT_HEAD_LEN:],
)
encrypt_key_for_head, iv_for_head = generate_key_iv(
encrypt_password, salt_for_head, 32, 16)
head = aes256cbc_decrypt(enc_head, encrypt_key_for_head, iv_for_head)
b_mc, magic_code, padding_salt, total_origin_len = parse_head(head)
total_origin_len = u8x8_to_u64(total_origin_len)
salt = padding_salt[:8]
encrypt_key, nonce_or_iv = generate_key_iv(encrypt_password, salt, 32, 16)
if b_mc != BAIDUPCS_PY_CRYPTO_MAGIC_CODE:
return
eio = None
if magic_code == SimpleEncryptIO.MAGIC_CODE:
eio = SimpleDecryptIO(io, encrypt_key, nonce_or_iv, total_origin_len)
elif magic_code == ChaCha20EncryptIO.MAGIC_CODE:
eio = ChaCha20DecryptIO(io, encrypt_key, nonce_or_iv, total_origin_len)
elif magic_code == AES256CBCEncryptIO.MAGIC_CODE:
eio = AES256CBCDecryptIO(io, encrypt_key, nonce_or_iv,
total_origin_len)
else:
logging.warning(f"Unknown magic_code: {magic_code}")
return
eio._total_head_len = PADDED_ENCRYPT_HEAD_WITH_SALT_LEN
return eio