from cryptography.hazmat.backends import default_backend
from cryptography.hazmat.primitives import hashes, hmac
from cryptography.hazmat.primitives.ciphers import Cipher, algorithms, modes
from cryptography.hazmat.primitives.kdf.scrypt import Scrypt
from multiversx_sdk.wallet.crypto.constants import (
CIPHER_ALGORITHM_AES_128_CTR,
KEY_DERIVATION_FUNCTION_SCRYPT,
)
from multiversx_sdk.wallet.crypto.encrypted_data import EncryptedData
from multiversx_sdk.wallet.errors import (
InvalidKeystoreFilePasswordError,
UnknownCipherError,
UnknownDerivationFunctionError,
)
[docs]
def decrypt(encrypted_data: EncryptedData, password: str) -> bytes:
"""
Also see: https://github.com/multiversx/mx-sdk-js-wallet/blob/main/src/crypto/decryptor.ts
"""
backend = default_backend()
if encrypted_data.kdf != KEY_DERIVATION_FUNCTION_SCRYPT:
raise UnknownDerivationFunctionError()
if encrypted_data.cipher != CIPHER_ALGORITHM_AES_128_CTR:
raise UnknownCipherError(name=encrypted_data.cipher)
salt = bytes.fromhex(encrypted_data.salt)
iv = bytes.fromhex(encrypted_data.iv)
ciphertext = bytes.fromhex(encrypted_data.ciphertext)
kdf = Scrypt(
salt=salt,
length=encrypted_data.kdfparams.dklen,
n=encrypted_data.kdfparams.n,
r=encrypted_data.kdfparams.r,
p=encrypted_data.kdfparams.p,
backend=backend,
)
derived_key = kdf.derive(bytes(password.encode()))
derived_key_first_half = derived_key[0:16]
derived_key_second_half = derived_key[16:32]
h = hmac.HMAC(derived_key_second_half, hashes.SHA256(), backend=backend)
h.update(ciphertext)
computed_mac = h.finalize()
actual_mac = bytes.fromhex(encrypted_data.mac)
if computed_mac != actual_mac:
raise InvalidKeystoreFilePasswordError()
cipher = Cipher(algorithms.AES(derived_key_first_half), modes.CTR(iv), backend=backend)
decryptor = cipher.decryptor()
data = decryptor.update(ciphertext) + decryptor.finalize()
return data