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