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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
from cryptography import utils
from cryptography.exceptions import InvalidSignature
from cryptography.hazmat.backends.openssl.utils import _truncate_digest
from cryptography.hazmat.primitives import hashes, serialization
from cryptography.hazmat.primitives.asymmetric import (
AsymmetricSignatureContext, AsymmetricVerificationContext, dsa
)
def _truncate_digest_for_dsa(dsa_cdata, digest, backend):
"""
This function truncates digests that are longer than a given DS
key's length so they can be signed. OpenSSL does this for us in
1.0.0c+ and it isn't needed in 0.9.8, but that leaves us with three
releases (1.0.0, 1.0.0a, and 1.0.0b) where this is a problem. This
truncation is not required in 0.9.8 because DSA is limited to SHA-1.
"""
order_bits = backend._lib.BN_num_bits(dsa_cdata.q)
return _truncate_digest(digest, order_bits)
@utils.register_interface(AsymmetricVerificationContext)
class _DSAVerificationContext(object):
def __init__(self, backend, public_key, signature, algorithm):
self._backend = backend
self._public_key = public_key
self._signature = signature
self._algorithm = algorithm
self._hash_ctx = hashes.Hash(self._algorithm, self._backend)
def update(self, data):
self._hash_ctx.update(data)
def verify(self):
data_to_verify = self._hash_ctx.finalize()
data_to_verify = _truncate_digest_for_dsa(
self._public_key._dsa_cdata, data_to_verify, self._backend
)
# The first parameter passed to DSA_verify is unused by OpenSSL but
# must be an integer.
res = self._backend._lib.DSA_verify(
0, data_to_verify, len(data_to_verify), self._signature,
len(self._signature), self._public_key._dsa_cdata)
if res != 1:
self._backend._consume_errors()
raise InvalidSignature
@utils.register_interface(AsymmetricSignatureContext)
class _DSASignatureContext(object):
def __init__(self, backend, private_key, algorithm):
self._backend = backend
self._private_key = private_key
self._algorithm = algorithm
self._hash_ctx = hashes.Hash(self._algorithm, self._backend)
def update(self, data):
self._hash_ctx.update(data)
def finalize(self):
data_to_sign = self._hash_ctx.finalize()
data_to_sign = _truncate_digest_for_dsa(
self._private_key._dsa_cdata, data_to_sign, self._backend
)
sig_buf_len = self._backend._lib.DSA_size(self._private_key._dsa_cdata)
sig_buf = self._backend._ffi.new("unsigned char[]", sig_buf_len)
buflen = self._backend._ffi.new("unsigned int *")
# The first parameter passed to DSA_sign is unused by OpenSSL but
# must be an integer.
res = self._backend._lib.DSA_sign(
0, data_to_sign, len(data_to_sign), sig_buf,
buflen, self._private_key._dsa_cdata)
self._backend.openssl_assert(res == 1)
self._backend.openssl_assert(buflen[0])
return self._backend._ffi.buffer(sig_buf)[:buflen[0]]
@utils.register_interface(dsa.DSAParametersWithNumbers)
class _DSAParameters(object):
def __init__(self, backend, dsa_cdata):
self._backend = backend
self._dsa_cdata = dsa_cdata
def parameter_numbers(self):
return dsa.DSAParameterNumbers(
p=self._backend._bn_to_int(self._dsa_cdata.p),
q=self._backend._bn_to_int(self._dsa_cdata.q),
g=self._backend._bn_to_int(self._dsa_cdata.g)
)
def generate_private_key(self):
return self._backend.generate_dsa_private_key(self)
@utils.register_interface(dsa.DSAPrivateKeyWithSerialization)
class _DSAPrivateKey(object):
def __init__(self, backend, dsa_cdata, evp_pkey):
self._backend = backend
self._dsa_cdata = dsa_cdata
self._evp_pkey = evp_pkey
self._key_size = self._backend._lib.BN_num_bits(self._dsa_cdata.p)
key_size = utils.read_only_property("_key_size")
def signer(self, signature_algorithm):
return _DSASignatureContext(self._backend, self, signature_algorithm)
def private_numbers(self):
return dsa.DSAPrivateNumbers(
public_numbers=dsa.DSAPublicNumbers(
parameter_numbers=dsa.DSAParameterNumbers(
p=self._backend._bn_to_int(self._dsa_cdata.p),
q=self._backend._bn_to_int(self._dsa_cdata.q),
g=self._backend._bn_to_int(self._dsa_cdata.g)
),
y=self._backend._bn_to_int(self._dsa_cdata.pub_key)
),
x=self._backend._bn_to_int(self._dsa_cdata.priv_key)
)
def public_key(self):
dsa_cdata = self._backend._lib.DSA_new()
self._backend.openssl_assert(dsa_cdata != self._backend._ffi.NULL)
dsa_cdata = self._backend._ffi.gc(
dsa_cdata, self._backend._lib.DSA_free
)
dsa_cdata.p = self._backend._lib.BN_dup(self._dsa_cdata.p)
dsa_cdata.q = self._backend._lib.BN_dup(self._dsa_cdata.q)
dsa_cdata.g = self._backend._lib.BN_dup(self._dsa_cdata.g)
dsa_cdata.pub_key = self._backend._lib.BN_dup(self._dsa_cdata.pub_key)
evp_pkey = self._backend._dsa_cdata_to_evp_pkey(dsa_cdata)
return _DSAPublicKey(self._backend, dsa_cdata, evp_pkey)
def parameters(self):
dsa_cdata = self._backend._lib.DSA_new()
self._backend.openssl_assert(dsa_cdata != self._backend._ffi.NULL)
dsa_cdata = self._backend._ffi.gc(
dsa_cdata, self._backend._lib.DSA_free
)
dsa_cdata.p = self._backend._lib.BN_dup(self._dsa_cdata.p)
dsa_cdata.q = self._backend._lib.BN_dup(self._dsa_cdata.q)
dsa_cdata.g = self._backend._lib.BN_dup(self._dsa_cdata.g)
return _DSAParameters(self._backend, dsa_cdata)
def private_bytes(self, encoding, format, encryption_algorithm):
return self._backend._private_key_bytes(
encoding,
format,
encryption_algorithm,
self._evp_pkey,
self._dsa_cdata
)
@utils.register_interface(dsa.DSAPublicKeyWithSerialization)
class _DSAPublicKey(object):
def __init__(self, backend, dsa_cdata, evp_pkey):
self._backend = backend
self._dsa_cdata = dsa_cdata
self._evp_pkey = evp_pkey
self._key_size = self._backend._lib.BN_num_bits(self._dsa_cdata.p)
key_size = utils.read_only_property("_key_size")
def verifier(self, signature, signature_algorithm):
if not isinstance(signature, bytes):
raise TypeError("signature must be bytes.")
return _DSAVerificationContext(
self._backend, self, signature, signature_algorithm
)
def public_numbers(self):
return dsa.DSAPublicNumbers(
parameter_numbers=dsa.DSAParameterNumbers(
p=self._backend._bn_to_int(self._dsa_cdata.p),
q=self._backend._bn_to_int(self._dsa_cdata.q),
g=self._backend._bn_to_int(self._dsa_cdata.g)
),
y=self._backend._bn_to_int(self._dsa_cdata.pub_key)
)
def parameters(self):
dsa_cdata = self._backend._lib.DSA_new()
self._backend.openssl_assert(dsa_cdata != self._backend._ffi.NULL)
dsa_cdata = self._backend._ffi.gc(
dsa_cdata, self._backend._lib.DSA_free
)
dsa_cdata.p = self._backend._lib.BN_dup(self._dsa_cdata.p)
dsa_cdata.q = self._backend._lib.BN_dup(self._dsa_cdata.q)
dsa_cdata.g = self._backend._lib.BN_dup(self._dsa_cdata.g)
return _DSAParameters(self._backend, dsa_cdata)
def public_bytes(self, encoding, format):
if format is serialization.PublicFormat.PKCS1:
raise ValueError(
"DSA public keys do not support PKCS1 serialization"
)
return self._backend._public_key_bytes(
encoding,
format,
self._evp_pkey,
None
)
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