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cryptography
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hazmat
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backends
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openssl
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Filename :
ec.py
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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)