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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 typing
from cryptography.exceptions import (
InvalidSignature,
UnsupportedAlgorithm,
_Reasons,
)
from cryptography.hazmat.backends.openssl.utils import (
_calculate_digest_and_algorithm,
_evp_pkey_derive,
)
from cryptography.hazmat.primitives import serialization
from cryptography.hazmat.primitives.asymmetric import ec
if typing.TYPE_CHECKING:
from cryptography.hazmat.backends.openssl.backend import Backend
def _check_signature_algorithm(
signature_algorithm: ec.EllipticCurveSignatureAlgorithm,
) -> None:
if not isinstance(signature_algorithm, ec.ECDSA):
raise UnsupportedAlgorithm(
"Unsupported elliptic curve signature algorithm.",
_Reasons.UNSUPPORTED_PUBLIC_KEY_ALGORITHM,
)
def _ec_key_curve_sn(backend: Backend, ec_key) -> str:
group = backend._lib.EC_KEY_get0_group(ec_key)
backend.openssl_assert(group != backend._ffi.NULL)
nid = backend._lib.EC_GROUP_get_curve_name(group)
# The following check is to find EC keys with unnamed curves and raise
# an error for now.
if nid == backend._lib.NID_undef:
raise ValueError(
"ECDSA keys with explicit parameters are unsupported at this time"
)
# This is like the above check, but it also catches the case where you
# explicitly encoded a curve with the same parameters as a named curve.
# Don't do that.
if (
not backend._lib.CRYPTOGRAPHY_IS_LIBRESSL
and backend._lib.EC_GROUP_get_asn1_flag(group) == 0
):
raise ValueError(
"ECDSA keys with explicit parameters are unsupported at this time"
)
curve_name = backend._lib.OBJ_nid2sn(nid)
backend.openssl_assert(curve_name != backend._ffi.NULL)
sn = backend._ffi.string(curve_name).decode("ascii")
return sn
def _mark_asn1_named_ec_curve(backend: Backend, ec_cdata):
"""
Set the named curve flag on the EC_KEY. This causes OpenSSL to
serialize EC keys along with their curve OID which makes
deserialization easier.
"""
backend._lib.EC_KEY_set_asn1_flag(
ec_cdata, backend._lib.OPENSSL_EC_NAMED_CURVE
)
def _check_key_infinity(backend: Backend, ec_cdata) -> None:
point = backend._lib.EC_KEY_get0_public_key(ec_cdata)
backend.openssl_assert(point != backend._ffi.NULL)
group = backend._lib.EC_KEY_get0_group(ec_cdata)
backend.openssl_assert(group != backend._ffi.NULL)
if backend._lib.EC_POINT_is_at_infinity(group, point):
raise ValueError(
"Cannot load an EC public key where the point is at infinity"
)
def _sn_to_elliptic_curve(backend: Backend, sn: str) -> ec.EllipticCurve:
try:
return ec._CURVE_TYPES[sn]()
except KeyError:
raise UnsupportedAlgorithm(
f"{sn} is not a supported elliptic curve",
_Reasons.UNSUPPORTED_ELLIPTIC_CURVE,
)
def _ecdsa_sig_sign(
backend: Backend, private_key: _EllipticCurvePrivateKey, data: bytes
) -> bytes:
max_size = backend._lib.ECDSA_size(private_key._ec_key)
backend.openssl_assert(max_size > 0)
sigbuf = backend._ffi.new("unsigned char[]", max_size)
siglen_ptr = backend._ffi.new("unsigned int[]", 1)
res = backend._lib.ECDSA_sign(
0, data, len(data), sigbuf, siglen_ptr, private_key._ec_key
)
backend.openssl_assert(res == 1)
return backend._ffi.buffer(sigbuf)[: siglen_ptr[0]]
def _ecdsa_sig_verify(
backend: Backend,
public_key: _EllipticCurvePublicKey,
signature: bytes,
data: bytes,
) -> None:
res = backend._lib.ECDSA_verify(
0, data, len(data), signature, len(signature), public_key._ec_key
)
if res != 1:
backend._consume_errors()
raise InvalidSignature
class _EllipticCurvePrivateKey(ec.EllipticCurvePrivateKey):
def __init__(self, backend: Backend, ec_key_cdata, evp_pkey):
self._backend = backend
self._ec_key = ec_key_cdata
self._evp_pkey = evp_pkey
sn = _ec_key_curve_sn(backend, ec_key_cdata)
self._curve = _sn_to_elliptic_curve(backend, sn)
_mark_asn1_named_ec_curve(backend, ec_key_cdata)
_check_key_infinity(backend, ec_key_cdata)
@property
def curve(self) -> ec.EllipticCurve:
return self._curve
@property
def key_size(self) -> int:
return self.curve.key_size
def exchange(
self, algorithm: ec.ECDH, peer_public_key: ec.EllipticCurvePublicKey
) -> bytes:
if not (
self._backend.elliptic_curve_exchange_algorithm_supported(
algorithm, self.curve
)
):
raise UnsupportedAlgorithm(
"This backend does not support the ECDH algorithm.",
_Reasons.UNSUPPORTED_EXCHANGE_ALGORITHM,
)
if peer_public_key.curve.name != self.curve.name:
raise ValueError(
"peer_public_key and self are not on the same curve"
)
return _evp_pkey_derive(self._backend, self._evp_pkey, peer_public_key)
def public_key(self) -> ec.EllipticCurvePublicKey:
group = self._backend._lib.EC_KEY_get0_group(self._ec_key)
self._backend.openssl_assert(group != self._backend._ffi.NULL)
curve_nid = self._backend._lib.EC_GROUP_get_curve_name(group)
public_ec_key = self._backend._ec_key_new_by_curve_nid(curve_nid)
point = self._backend._lib.EC_KEY_get0_public_key(self._ec_key)
self._backend.openssl_assert(point != self._backend._ffi.NULL)
res = self._backend._lib.EC_KEY_set_public_key(public_ec_key, point)
self._backend.openssl_assert(res == 1)
evp_pkey = self._backend._ec_cdata_to_evp_pkey(public_ec_key)
return _EllipticCurvePublicKey(self._backend, public_ec_key, evp_pkey)
def private_numbers(self) -> ec.EllipticCurvePrivateNumbers:
bn = self._backend._lib.EC_KEY_get0_private_key(self._ec_key)
private_value = self._backend._bn_to_int(bn)
return ec.EllipticCurvePrivateNumbers(
private_value=private_value,
public_numbers=self.public_key().public_numbers(),
)
def private_bytes(
self,
encoding: serialization.Encoding,
format: serialization.PrivateFormat,
encryption_algorithm: serialization.KeySerializationEncryption,
) -> bytes:
return self._backend._private_key_bytes(
encoding,
format,
encryption_algorithm,
self,
self._evp_pkey,
self._ec_key,
)
def sign(
self,
data: bytes,
signature_algorithm: ec.EllipticCurveSignatureAlgorithm,
) -> bytes:
_check_signature_algorithm(signature_algorithm)
data, _ = _calculate_digest_and_algorithm(
data,
signature_algorithm.algorithm,
)
return _ecdsa_sig_sign(self._backend, self, data)
class _EllipticCurvePublicKey(ec.EllipticCurvePublicKey):
def __init__(self, backend: Backend, ec_key_cdata, evp_pkey):
self._backend = backend
self._ec_key = ec_key_cdata
self._evp_pkey = evp_pkey
sn = _ec_key_curve_sn(backend, ec_key_cdata)
self._curve = _sn_to_elliptic_curve(backend, sn)
_mark_asn1_named_ec_curve(backend, ec_key_cdata)
_check_key_infinity(backend, ec_key_cdata)
@property
def curve(self) -> ec.EllipticCurve:
return self._curve
@property
def key_size(self) -> int:
return self.curve.key_size
def __eq__(self, other: object) -> bool:
if not isinstance(other, _EllipticCurvePublicKey):
return NotImplemented
return (
self._backend._lib.EVP_PKEY_cmp(self._evp_pkey, other._evp_pkey)
== 1
)
def public_numbers(self) -> ec.EllipticCurvePublicNumbers:
group = self._backend._lib.EC_KEY_get0_group(self._ec_key)
self._backend.openssl_assert(group != self._backend._ffi.NULL)
point = self._backend._lib.EC_KEY_get0_public_key(self._ec_key)
self._backend.openssl_assert(point != self._backend._ffi.NULL)
with self._backend._tmp_bn_ctx() as bn_ctx:
bn_x = self._backend._lib.BN_CTX_get(bn_ctx)
bn_y = self._backend._lib.BN_CTX_get(bn_ctx)
res = self._backend._lib.EC_POINT_get_affine_coordinates(
group, point, bn_x, bn_y, bn_ctx
)
self._backend.openssl_assert(res == 1)
x = self._backend._bn_to_int(bn_x)
y = self._backend._bn_to_int(bn_y)
return ec.EllipticCurvePublicNumbers(x=x, y=y, curve=self._curve)
def _encode_point(self, format: serialization.PublicFormat) -> bytes:
if format is serialization.PublicFormat.CompressedPoint:
conversion = self._backend._lib.POINT_CONVERSION_COMPRESSED
else:
assert format is serialization.PublicFormat.UncompressedPoint
conversion = self._backend._lib.POINT_CONVERSION_UNCOMPRESSED
group = self._backend._lib.EC_KEY_get0_group(self._ec_key)
self._backend.openssl_assert(group != self._backend._ffi.NULL)
point = self._backend._lib.EC_KEY_get0_public_key(self._ec_key)
self._backend.openssl_assert(point != self._backend._ffi.NULL)
with self._backend._tmp_bn_ctx() as bn_ctx:
buflen = self._backend._lib.EC_POINT_point2oct(
group, point, conversion, self._backend._ffi.NULL, 0, bn_ctx
)
self._backend.openssl_assert(buflen > 0)
buf = self._backend._ffi.new("char[]", buflen)
res = self._backend._lib.EC_POINT_point2oct(
group, point, conversion, buf, buflen, bn_ctx
)
self._backend.openssl_assert(buflen == res)
return self._backend._ffi.buffer(buf)[:]
def public_bytes(
self,
encoding: serialization.Encoding,
format: serialization.PublicFormat,
) -> bytes:
if (
encoding is serialization.Encoding.X962
or format is serialization.PublicFormat.CompressedPoint
or format is serialization.PublicFormat.UncompressedPoint
):
if encoding is not serialization.Encoding.X962 or format not in (
serialization.PublicFormat.CompressedPoint,
serialization.PublicFormat.UncompressedPoint,
):
raise ValueError(
"X962 encoding must be used with CompressedPoint or "
"UncompressedPoint format"
)
return self._encode_point(format)
else:
return self._backend._public_key_bytes(
encoding, format, self, self._evp_pkey, None
)
def verify(
self,
signature: bytes,
data: bytes,
signature_algorithm: ec.EllipticCurveSignatureAlgorithm,
) -> None:
_check_signature_algorithm(signature_algorithm)
data, _ = _calculate_digest_and_algorithm(
data,
signature_algorithm.algorithm,
)
_ecdsa_sig_verify(self._backend, self, signature, data)
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