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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 UnsupportedAlgorithm, _Reasons
from cryptography.hazmat.primitives import serialization
from cryptography.hazmat.primitives.asymmetric import dh
def _dh_params_dup(dh_cdata, backend):
lib = backend._lib
ffi = backend._ffi
param_cdata = lib.DHparams_dup(dh_cdata)
backend.openssl_assert(param_cdata != ffi.NULL)
param_cdata = ffi.gc(param_cdata, lib.DH_free)
if lib.OPENSSL_VERSION_NUMBER < 0x10002000 or lib.CRYPTOGRAPHY_IS_LIBRESSL:
# In OpenSSL versions < 1.0.2 or libressl DHparams_dup don't copy q
q = ffi.new("BIGNUM **")
lib.DH_get0_pqg(dh_cdata, ffi.NULL, q, ffi.NULL)
q_dup = lib.BN_dup(q[0])
res = lib.DH_set0_pqg(param_cdata, ffi.NULL, q_dup, ffi.NULL)
backend.openssl_assert(res == 1)
return param_cdata
def _dh_cdata_to_parameters(dh_cdata, backend):
param_cdata = _dh_params_dup(dh_cdata, backend)
return _DHParameters(backend, param_cdata)
@utils.register_interface(dh.DHParametersWithSerialization)
class _DHParameters(object):
def __init__(self, backend, dh_cdata):
self._backend = backend
self._dh_cdata = dh_cdata
def parameter_numbers(self):
p = self._backend._ffi.new("BIGNUM **")
g = self._backend._ffi.new("BIGNUM **")
q = self._backend._ffi.new("BIGNUM **")
self._backend._lib.DH_get0_pqg(self._dh_cdata, p, q, g)
self._backend.openssl_assert(p[0] != self._backend._ffi.NULL)
self._backend.openssl_assert(g[0] != self._backend._ffi.NULL)
if q[0] == self._backend._ffi.NULL:
q_val = None
else:
q_val = self._backend._bn_to_int(q[0])
return dh.DHParameterNumbers(
p=self._backend._bn_to_int(p[0]),
g=self._backend._bn_to_int(g[0]),
q=q_val
)
def generate_private_key(self):
return self._backend.generate_dh_private_key(self)
def _handle_dh_compute_key_error(errors, backend):
lib = backend._lib
backend.openssl_assert(errors[0][1:] == (
lib.ERR_LIB_DH,
lib.DH_F_COMPUTE_KEY,
lib.DH_R_INVALID_PUBKEY
))
raise ValueError("Public key value is invalid for this exchange.")
def _get_dh_num_bits(backend, dh_cdata):
p = backend._ffi.new("BIGNUM **")
backend._lib.DH_get0_pqg(dh_cdata, p,
backend._ffi.NULL,
backend._ffi.NULL)
backend.openssl_assert(p[0] != backend._ffi.NULL)
return backend._lib.BN_num_bits(p[0])
@utils.register_interface(dh.DHPrivateKeyWithSerialization)
class _DHPrivateKey(object):
def __init__(self, backend, dh_cdata, evp_pkey):
self._backend = backend
self._dh_cdata = dh_cdata
self._evp_pkey = evp_pkey
self._key_size_bytes = self._backend._lib.DH_size(dh_cdata)
@property
def key_size(self):
return _get_dh_num_bits(self._backend, self._dh_cdata)
def private_numbers(self):
p = self._backend._ffi.new("BIGNUM **")
g = self._backend._ffi.new("BIGNUM **")
q = self._backend._ffi.new("BIGNUM **")
self._backend._lib.DH_get0_pqg(self._dh_cdata, p, q, g)
self._backend.openssl_assert(p[0] != self._backend._ffi.NULL)
self._backend.openssl_assert(g[0] != self._backend._ffi.NULL)
if q[0] == self._backend._ffi.NULL:
q_val = None
else:
q_val = self._backend._bn_to_int(q[0])
pub_key = self._backend._ffi.new("BIGNUM **")
priv_key = self._backend._ffi.new("BIGNUM **")
self._backend._lib.DH_get0_key(self._dh_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 dh.DHPrivateNumbers(
public_numbers=dh.DHPublicNumbers(
parameter_numbers=dh.DHParameterNumbers(
p=self._backend._bn_to_int(p[0]),
g=self._backend._bn_to_int(g[0]),
q=q_val
),
y=self._backend._bn_to_int(pub_key[0])
),
x=self._backend._bn_to_int(priv_key[0])
)
def exchange(self, peer_public_key):
buf = self._backend._ffi.new("unsigned char[]", self._key_size_bytes)
pub_key = self._backend._ffi.new("BIGNUM **")
self._backend._lib.DH_get0_key(peer_public_key._dh_cdata, pub_key,
self._backend._ffi.NULL)
self._backend.openssl_assert(pub_key[0] != self._backend._ffi.NULL)
res = self._backend._lib.DH_compute_key(
buf,
pub_key[0],
self._dh_cdata
)
if res == -1:
errors = self._backend._consume_errors()
return _handle_dh_compute_key_error(errors, self._backend)
else:
self._backend.openssl_assert(res >= 1)
key = self._backend._ffi.buffer(buf)[:res]
pad = self._key_size_bytes - len(key)
if pad > 0:
key = (b"\x00" * pad) + key
return key
def public_key(self):
dh_cdata = _dh_params_dup(self._dh_cdata, self._backend)
pub_key = self._backend._ffi.new("BIGNUM **")
self._backend._lib.DH_get0_key(self._dh_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])
self._backend.openssl_assert(pub_key_dup != self._backend._ffi.NULL)
res = self._backend._lib.DH_set0_key(dh_cdata,
pub_key_dup,
self._backend._ffi.NULL)
self._backend.openssl_assert(res == 1)
evp_pkey = self._backend._dh_cdata_to_evp_pkey(dh_cdata)
return _DHPublicKey(self._backend, dh_cdata, evp_pkey)
def parameters(self):
return _dh_cdata_to_parameters(self._dh_cdata, self._backend)
def private_bytes(self, encoding, format, encryption_algorithm):
if format is not serialization.PrivateFormat.PKCS8:
raise ValueError(
"DH private keys support only PKCS8 serialization"
)
if not self._backend._lib.Cryptography_HAS_EVP_PKEY_DHX:
q = self._backend._ffi.new("BIGNUM **")
self._backend._lib.DH_get0_pqg(self._dh_cdata,
self._backend._ffi.NULL,
q,
self._backend._ffi.NULL)
if q[0] != self._backend._ffi.NULL:
raise UnsupportedAlgorithm(
"DH X9.42 serialization is not supported",
_Reasons.UNSUPPORTED_SERIALIZATION)
return self._backend._private_key_bytes(
encoding,
format,
encryption_algorithm,
self._evp_pkey,
self._dh_cdata
)
@utils.register_interface(dh.DHPublicKeyWithSerialization)
class _DHPublicKey(object):
def __init__(self, backend, dh_cdata, evp_pkey):
self._backend = backend
self._dh_cdata = dh_cdata
self._evp_pkey = evp_pkey
self._key_size_bits = _get_dh_num_bits(self._backend, self._dh_cdata)
@property
def key_size(self):
return self._key_size_bits
def public_numbers(self):
p = self._backend._ffi.new("BIGNUM **")
g = self._backend._ffi.new("BIGNUM **")
q = self._backend._ffi.new("BIGNUM **")
self._backend._lib.DH_get0_pqg(self._dh_cdata, p, q, g)
self._backend.openssl_assert(p[0] != self._backend._ffi.NULL)
self._backend.openssl_assert(g[0] != self._backend._ffi.NULL)
if q[0] == self._backend._ffi.NULL:
q_val = None
else:
q_val = self._backend._bn_to_int(q[0])
pub_key = self._backend._ffi.new("BIGNUM **")
self._backend._lib.DH_get0_key(self._dh_cdata,
pub_key, self._backend._ffi.NULL)
self._backend.openssl_assert(pub_key[0] != self._backend._ffi.NULL)
return dh.DHPublicNumbers(
parameter_numbers=dh.DHParameterNumbers(
p=self._backend._bn_to_int(p[0]),
g=self._backend._bn_to_int(g[0]),
q=q_val
),
y=self._backend._bn_to_int(pub_key[0])
)
def parameters(self):
return _dh_cdata_to_parameters(self._dh_cdata, self._backend)
def public_bytes(self, encoding, format):
if format is not serialization.PublicFormat.SubjectPublicKeyInfo:
raise ValueError(
"DH public keys support only "
"SubjectPublicKeyInfo serialization"
)
if not self._backend._lib.Cryptography_HAS_EVP_PKEY_DHX:
q = self._backend._ffi.new("BIGNUM **")
self._backend._lib.DH_get0_pqg(self._dh_cdata,
self._backend._ffi.NULL,
q,
self._backend._ffi.NULL)
if q[0] != self._backend._ffi.NULL:
raise UnsupportedAlgorithm(
"DH X9.42 serialization is not supported",
_Reasons.UNSUPPORTED_SERIALIZATION)
return self._backend._public_key_bytes(
encoding,
format,
self,
self._evp_pkey,
None
)
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