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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 (
_calculate_digest_and_algorithm, _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+, leaving us with three releases (1.0.0, 1.0.0a, and 1.0.0b) where
this is a problem.
"""
q = backend._ffi.new("BIGNUM **")
backend._lib.DSA_get0_pqg(
dsa_cdata, backend._ffi.NULL, q, backend._ffi.NULL
)
backend.openssl_assert(q[0] != backend._ffi.NULL)
order_bits = backend._lib.BN_num_bits(q[0])
return _truncate_digest(digest, order_bits)
def _dsa_sig_sign(backend, private_key, data):
sig_buf_len = backend._lib.DSA_size(private_key._dsa_cdata)
sig_buf = backend._ffi.new("unsigned char[]", sig_buf_len)
buflen = backend._ffi.new("unsigned int *")
# The first parameter passed to DSA_sign is unused by OpenSSL but
# must be an integer.
res = backend._lib.DSA_sign(
0, data, len(data), sig_buf, buflen, private_key._dsa_cdata
)
backend.openssl_assert(res == 1)
backend.openssl_assert(buflen[0])
return backend._ffi.buffer(sig_buf)[:buflen[0]]
def _dsa_sig_verify(backend, public_key, signature, data):
# The first parameter passed to DSA_verify is unused by OpenSSL but
# must be an integer.
res = backend._lib.DSA_verify(
0, data, len(data), signature, len(signature), public_key._dsa_cdata
)
if res != 1:
backend._consume_errors()
raise InvalidSignature
@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
)
_dsa_sig_verify(
self._backend, self._public_key, self._signature, data_to_verify
)
@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
)
return _dsa_sig_sign(self._backend, self._private_key, data_to_sign)
@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):
p = self._backend._ffi.new("BIGNUM **")
q = self._backend._ffi.new("BIGNUM **")
g = self._backend._ffi.new("BIGNUM **")
self._backend._lib.DSA_get0_pqg(self._dsa_cdata, p, q, g)
self._backend.openssl_assert(p[0] != self._backend._ffi.NULL)
self._backend.openssl_assert(q[0] != self._backend._ffi.NULL)
self._backend.openssl_assert(g[0] != self._backend._ffi.NULL)
return dsa.DSAParameterNumbers(
p=self._backend._bn_to_int(p[0]),
q=self._backend._bn_to_int(q[0]),
g=self._backend._bn_to_int(g[0])
)
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
p = self._backend._ffi.new("BIGNUM **")
self._backend._lib.DSA_get0_pqg(
dsa_cdata, p, self._backend._ffi.NULL, self._backend._ffi.NULL
)
self._backend.openssl_assert(p[0] != backend._ffi.NULL)
self._key_size = self._backend._lib.BN_num_bits(p[0])
key_size = utils.read_only_property("_key_size")
def signer(self, signature_algorithm):
return _DSASignatureContext(self._backend, self, signature_algorithm)
def private_numbers(self):
p = self._backend._ffi.new("BIGNUM **")
q = self._backend._ffi.new("BIGNUM **")
g = self._backend._ffi.new("BIGNUM **")
pub_key = self._backend._ffi.new("BIGNUM **")
priv_key = self._backend._ffi.new("BIGNUM **")
self._backend._lib.DSA_get0_pqg(self._dsa_cdata, p, q, g)
self._backend.openssl_assert(p[0] != self._backend._ffi.NULL)
self._backend.openssl_assert(q[0] != self._backend._ffi.NULL)
self._backend.openssl_assert(g[0] != self._backend._ffi.NULL)
self._backend._lib.DSA_get0_key(self._dsa_cdata, pub_key, priv_key)
self._backend.openssl_assert(pub_key[0] != self._backend._ffi.NULL)
self._backend.openssl_assert(priv_key[0] != self._backend._ffi.NULL)
return dsa.DSAPrivateNumbers(
public_numbers=dsa.DSAPublicNumbers(
parameter_numbers=dsa.DSAParameterNumbers(
p=self._backend._bn_to_int(p[0]),
q=self._backend._bn_to_int(q[0]),
g=self._backend._bn_to_int(g[0])
),
y=self._backend._bn_to_int(pub_key[0])
),
x=self._backend._bn_to_int(priv_key[0])
)
def public_key(self):
dsa_cdata = self._backend._lib.DSAparams_dup(self._dsa_cdata)
self._backend.openssl_assert(dsa_cdata != self._backend._ffi.NULL)
dsa_cdata = self._backend._ffi.gc(
dsa_cdata, self._backend._lib.DSA_free
)
pub_key = self._backend._ffi.new("BIGNUM **")
self._backend._lib.DSA_get0_key(
self._dsa_cdata, pub_key, self._backend._ffi.NULL
)
self._backend.openssl_assert(pub_key[0] != self._backend._ffi.NULL)
pub_key_dup = self._backend._lib.BN_dup(pub_key[0])
res = self._backend._lib.DSA_set0_key(
dsa_cdata, pub_key_dup, self._backend._ffi.NULL
)
self._backend.openssl_assert(res == 1)
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.DSAparams_dup(self._dsa_cdata)
self._backend.openssl_assert(dsa_cdata != self._backend._ffi.NULL)
dsa_cdata = self._backend._ffi.gc(
dsa_cdata, self._backend._lib.DSA_free
)
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
)
def sign(self, data, algorithm):
data, algorithm = _calculate_digest_and_algorithm(
self._backend, data, algorithm
)
data = _truncate_digest_for_dsa(self._dsa_cdata, data, self._backend)
return _dsa_sig_sign(self._backend, self, data)
@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
p = self._backend._ffi.new("BIGNUM **")
self._backend._lib.DSA_get0_pqg(
dsa_cdata, p, self._backend._ffi.NULL, self._backend._ffi.NULL
)
self._backend.openssl_assert(p[0] != backend._ffi.NULL)
self._key_size = self._backend._lib.BN_num_bits(p[0])
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):
p = self._backend._ffi.new("BIGNUM **")
q = self._backend._ffi.new("BIGNUM **")
g = self._backend._ffi.new("BIGNUM **")
pub_key = self._backend._ffi.new("BIGNUM **")
self._backend._lib.DSA_get0_pqg(self._dsa_cdata, p, q, g)
self._backend.openssl_assert(p[0] != self._backend._ffi.NULL)
self._backend.openssl_assert(q[0] != self._backend._ffi.NULL)
self._backend.openssl_assert(g[0] != self._backend._ffi.NULL)
self._backend._lib.DSA_get0_key(
self._dsa_cdata, pub_key, self._backend._ffi.NULL
)
self._backend.openssl_assert(pub_key[0] != self._backend._ffi.NULL)
return dsa.DSAPublicNumbers(
parameter_numbers=dsa.DSAParameterNumbers(
p=self._backend._bn_to_int(p[0]),
q=self._backend._bn_to_int(q[0]),
g=self._backend._bn_to_int(g[0])
),
y=self._backend._bn_to_int(pub_key[0])
)
def parameters(self):
dsa_cdata = self._backend._lib.DSAparams_dup(self._dsa_cdata)
dsa_cdata = self._backend._ffi.gc(
dsa_cdata, self._backend._lib.DSA_free
)
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,
self._evp_pkey,
None
)
def verify(self, signature, data, algorithm):
data, algorithm = _calculate_digest_and_algorithm(
self._backend, data, algorithm
)
data = _truncate_digest_for_dsa(self._dsa_cdata, data, self._backend)
return _dsa_sig_verify(self._backend, self, signature, data)
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