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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 annotations
import abc
from cryptography.hazmat.primitives import hashes
from cryptography.hazmat.primitives._asymmetric import (
AsymmetricPadding as AsymmetricPadding,
)
from cryptography.hazmat.primitives.asymmetric import rsa
class PKCS1v15(AsymmetricPadding):
name = "EMSA-PKCS1-v1_5"
class _MaxLength:
"Sentinel value for `MAX_LENGTH`."
class _Auto:
"Sentinel value for `AUTO`."
class _DigestLength:
"Sentinel value for `DIGEST_LENGTH`."
class PSS(AsymmetricPadding):
MAX_LENGTH = _MaxLength()
AUTO = _Auto()
DIGEST_LENGTH = _DigestLength()
name = "EMSA-PSS"
_salt_length: int | _MaxLength | _Auto | _DigestLength
def __init__(
self,
mgf: MGF,
salt_length: int | _MaxLength | _Auto | _DigestLength,
) -> None:
self._mgf = mgf
if not isinstance(
salt_length, (int, _MaxLength, _Auto, _DigestLength)
):
raise TypeError(
"salt_length must be an integer, MAX_LENGTH, "
"DIGEST_LENGTH, or AUTO"
)
if isinstance(salt_length, int) and salt_length < 0:
raise ValueError("salt_length must be zero or greater.")
self._salt_length = salt_length
@property
def mgf(self) -> MGF:
return self._mgf
class OAEP(AsymmetricPadding):
name = "EME-OAEP"
def __init__(
self,
mgf: MGF,
algorithm: hashes.HashAlgorithm,
label: bytes | None,
):
if not isinstance(algorithm, hashes.HashAlgorithm):
raise TypeError("Expected instance of hashes.HashAlgorithm.")
self._mgf = mgf
self._algorithm = algorithm
self._label = label
@property
def algorithm(self) -> hashes.HashAlgorithm:
return self._algorithm
@property
def mgf(self) -> MGF:
return self._mgf
class MGF(metaclass=abc.ABCMeta):
_algorithm: hashes.HashAlgorithm
class MGF1(MGF):
MAX_LENGTH = _MaxLength()
def __init__(self, algorithm: hashes.HashAlgorithm):
if not isinstance(algorithm, hashes.HashAlgorithm):
raise TypeError("Expected instance of hashes.HashAlgorithm.")
self._algorithm = algorithm
def calculate_max_pss_salt_length(
key: rsa.RSAPrivateKey | rsa.RSAPublicKey,
hash_algorithm: hashes.HashAlgorithm,
) -> int:
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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