File Content: padding.py # This file is dual licensed under the terms of the Apache License, Version # 2.0, and the BSD License. See the LICENSE file in the root of this repository # for complete details. from __future__ import absolute_import, division, print_function import abc import math import six from cryptography import utils from cryptography.hazmat.primitives import hashes from cryptography.hazmat.primitives.asymmetric import rsa @six.add_metaclass(abc.ABCMeta) class AsymmetricPadding(object): @abc.abstractproperty def name(self): """ A string naming this padding (e.g. "PSS", "PKCS1"). """ @utils.register_interface(AsymmetricPadding) class PKCS1v15(object): name = "EMSA-PKCS1-v1_5" @utils.register_interface(AsymmetricPadding) class PSS(object): MAX_LENGTH = object() name = "EMSA-PSS" def __init__(self, mgf, salt_length): self._mgf = mgf if (not isinstance(salt_length, six.integer_types) and salt_length is not self.MAX_LENGTH): raise TypeError("salt_length must be an integer.") if salt_length is not self.MAX_LENGTH and salt_length < 0: raise ValueError("salt_length must be zero or greater.") self._salt_length = salt_length @utils.register_interface(AsymmetricPadding) class OAEP(object): name = "EME-OAEP" def __init__(self, mgf, algorithm, label): if not isinstance(algorithm, hashes.HashAlgorithm): raise TypeError("Expected instance of hashes.HashAlgorithm.") self._mgf = mgf self._algorithm = algorithm self._label = label class MGF1(object): MAX_LENGTH = object() def __init__(self, algorithm): if not isinstance(algorithm, hashes.HashAlgorithm): raise TypeError("Expected instance of hashes.HashAlgorithm.") self._algorithm = algorithm def calculate_max_pss_salt_length(key, hash_algorithm): if not isinstance(key, (rsa.RSAPrivateKey, rsa.RSAPublicKey)): raise TypeError("key must be an RSA public or private key") # bit length - 1 per RFC 3447 emlen = int(math.ceil((key.key_size - 1) / 8.0)) salt_length = emlen - hash_algorithm.digest_size - 2 assert salt_length >= 0 return salt_length Submit