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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.
import abc
import typing
from cryptography import utils
from cryptography.hazmat.backends import _get_backend
from cryptography.hazmat.primitives import _serialization, hashes
from cryptography.hazmat.primitives.asymmetric import (
AsymmetricSignatureContext,
AsymmetricVerificationContext,
utils as asym_utils,
)
class DSAParameters(metaclass=abc.ABCMeta):
@abc.abstractmethod
def generate_private_key(self) -> "DSAPrivateKey":
"""
Generates and returns a DSAPrivateKey.
"""
@abc.abstractmethod
def parameter_numbers(self) -> "DSAParameterNumbers":
"""
Returns a DSAParameterNumbers.
"""
DSAParametersWithNumbers = DSAParameters
class DSAPrivateKey(metaclass=abc.ABCMeta):
@abc.abstractproperty
def key_size(self) -> int:
"""
The bit length of the prime modulus.
"""
@abc.abstractmethod
def public_key(self) -> "DSAPublicKey":
"""
The DSAPublicKey associated with this private key.
"""
@abc.abstractmethod
def parameters(self) -> DSAParameters:
"""
The DSAParameters object associated with this private key.
"""
@abc.abstractmethod
def signer(
self,
signature_algorithm: hashes.HashAlgorithm,
) -> AsymmetricSignatureContext:
"""
Returns an AsymmetricSignatureContext used for signing data.
"""
@abc.abstractmethod
def sign(
self,
data: bytes,
algorithm: typing.Union[asym_utils.Prehashed, hashes.HashAlgorithm],
) -> bytes:
"""
Signs the data
"""
@abc.abstractmethod
def private_numbers(self) -> "DSAPrivateNumbers":
"""
Returns a DSAPrivateNumbers.
"""
@abc.abstractmethod
def private_bytes(
self,
encoding: _serialization.Encoding,
format: _serialization.PrivateFormat,
encryption_algorithm: _serialization.KeySerializationEncryption,
) -> bytes:
"""
Returns the key serialized as bytes.
"""
DSAPrivateKeyWithSerialization = DSAPrivateKey
class DSAPublicKey(metaclass=abc.ABCMeta):
@abc.abstractproperty
def key_size(self) -> int:
"""
The bit length of the prime modulus.
"""
@abc.abstractmethod
def parameters(self) -> DSAParameters:
"""
The DSAParameters object associated with this public key.
"""
@abc.abstractmethod
def verifier(
self,
signature: bytes,
signature_algorithm: hashes.HashAlgorithm,
) -> AsymmetricVerificationContext:
"""
Returns an AsymmetricVerificationContext used for signing data.
"""
@abc.abstractmethod
def public_numbers(self) -> "DSAPublicNumbers":
"""
Returns a DSAPublicNumbers.
"""
@abc.abstractmethod
def public_bytes(
self,
encoding: _serialization.Encoding,
format: _serialization.PublicFormat,
) -> bytes:
"""
Returns the key serialized as bytes.
"""
@abc.abstractmethod
def verify(
self,
signature: bytes,
data: bytes,
algorithm: typing.Union[asym_utils.Prehashed, hashes.HashAlgorithm],
):
"""
Verifies the signature of the data.
"""
DSAPublicKeyWithSerialization = DSAPublicKey
class DSAParameterNumbers(object):
def __init__(self, p: int, q: int, g: int):
if (
not isinstance(p, int)
or not isinstance(q, int)
or not isinstance(g, int)
):
raise TypeError(
"DSAParameterNumbers p, q, and g arguments must be integers."
)
self._p = p
self._q = q
self._g = g
p = utils.read_only_property("_p")
q = utils.read_only_property("_q")
g = utils.read_only_property("_g")
def parameters(self, backend=None) -> DSAParameters:
backend = _get_backend(backend)
return backend.load_dsa_parameter_numbers(self)
def __eq__(self, other):
if not isinstance(other, DSAParameterNumbers):
return NotImplemented
return self.p == other.p and self.q == other.q and self.g == other.g
def __ne__(self, other):
return not self == other
def __repr__(self):
return (
"<DSAParameterNumbers(p={self.p}, q={self.q}, "
"g={self.g})>".format(self=self)
)
class DSAPublicNumbers(object):
def __init__(self, y: int, parameter_numbers: DSAParameterNumbers):
if not isinstance(y, int):
raise TypeError("DSAPublicNumbers y argument must be an integer.")
if not isinstance(parameter_numbers, DSAParameterNumbers):
raise TypeError(
"parameter_numbers must be a DSAParameterNumbers instance."
)
self._y = y
self._parameter_numbers = parameter_numbers
y = utils.read_only_property("_y")
parameter_numbers = utils.read_only_property("_parameter_numbers")
def public_key(self, backend=None) -> DSAPublicKey:
backend = _get_backend(backend)
return backend.load_dsa_public_numbers(self)
def __eq__(self, other):
if not isinstance(other, DSAPublicNumbers):
return NotImplemented
return (
self.y == other.y
and self.parameter_numbers == other.parameter_numbers
)
def __ne__(self, other):
return not self == other
def __repr__(self):
return (
"<DSAPublicNumbers(y={self.y}, "
"parameter_numbers={self.parameter_numbers})>".format(self=self)
)
class DSAPrivateNumbers(object):
def __init__(self, x: int, public_numbers: DSAPublicNumbers):
if not isinstance(x, int):
raise TypeError("DSAPrivateNumbers x argument must be an integer.")
if not isinstance(public_numbers, DSAPublicNumbers):
raise TypeError(
"public_numbers must be a DSAPublicNumbers instance."
)
self._public_numbers = public_numbers
self._x = x
x = utils.read_only_property("_x")
public_numbers = utils.read_only_property("_public_numbers")
def private_key(self, backend=None) -> DSAPrivateKey:
backend = _get_backend(backend)
return backend.load_dsa_private_numbers(self)
def __eq__(self, other):
if not isinstance(other, DSAPrivateNumbers):
return NotImplemented
return (
self.x == other.x and self.public_numbers == other.public_numbers
)
def __ne__(self, other):
return not self == other
def generate_parameters(key_size: int, backend=None) -> DSAParameters:
backend = _get_backend(backend)
return backend.generate_dsa_parameters(key_size)
def generate_private_key(key_size: int, backend=None) -> DSAPrivateKey:
backend = _get_backend(backend)
return backend.generate_dsa_private_key_and_parameters(key_size)
def _check_dsa_parameters(parameters: DSAParameterNumbers):
if parameters.p.bit_length() not in [1024, 2048, 3072, 4096]:
raise ValueError(
"p must be exactly 1024, 2048, 3072, or 4096 bits long"
)
if parameters.q.bit_length() not in [160, 224, 256]:
raise ValueError("q must be exactly 160, 224, or 256 bits long")
if not (1 < parameters.g < parameters.p):
raise ValueError("g, p don't satisfy 1 < g < p.")
def _check_dsa_private_numbers(numbers: DSAPrivateNumbers):
parameters = numbers.public_numbers.parameter_numbers
_check_dsa_parameters(parameters)
if numbers.x <= 0 or numbers.x >= parameters.q:
raise ValueError("x must be > 0 and < q.")
if numbers.public_numbers.y != pow(parameters.g, numbers.x, parameters.p):
raise ValueError("y must be equal to (g ** x % p).")
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