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# 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 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 = (key.key_size + 6) // 8
salt_length = emlen - hash_algorithm.digest_size - 2
assert salt_length >= 0
return salt_length
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