openssl3.2 - 官方demo学习 - pkey - EVP_PKEY_EC_keygen.c

openssl3.2 - 官方demo学习 - pkey - EVP_PKEY_EC_keygen.c

概述

给定椭圆曲线名字, 产生上下文_evp_pkey_ctx
设置_evp_pkey_ctx的椭圆曲线参数(有默认参数, 不用特意设置, 给熟悉的人用), 不熟悉密码学的人, 只选椭圆曲线的名字就行
从_evp_pkey_ctx产生ec key;
打印 ec EVP_PKEY 的值(可以取出椭圆曲线的名字, 公钥, 私钥).

笔记

/*!
\file EVP_PKEY_EC_keygen.c
\note 
openssl3.2 - 官方demo学习 - pkey - EVP_PKEY_EC_keygen.c

给定椭圆曲线名字, 产生上下文_evp_pkey_ctx
设置_evp_pkey_ctx的椭圆曲线参数(有默认参数, 不用特意设置, 给熟悉的人用), 不熟悉密码学的人, 只选椭圆曲线的名字就行
从_evp_pkey_ctx产生ec key;
打印 ec EVP_PKEY 的值(可以取出椭圆曲线的名字, 公钥, 私钥).
*/

/*-
 * Copyright 2021-2023 The OpenSSL Project Authors. All Rights Reserved.
 *
 * Licensed under the Apache License 2.0 (the "License").  You may not use
 * this file except in compliance with the License.  You can obtain a copy
 * in the file LICENSE in the source distribution or at
 * https://www.openssl.org/source/license.html
 */

 /*
  * Example showing how to generate an EC key and extract values from the
  * generated key.
  */

#include <string.h>
#include <stdio.h>
#include <openssl/err.h>
#include <openssl/evp.h>
#include <openssl/core_names.h>

#include "my_openSSL_lib.h"

static int get_key_values(EVP_PKEY* pkey);

/*
 * The following code shows how to generate an EC key from a curve name
 * with additional parameters. If only the curve name is required then the
 * simple helper can be used instead i.e. Either
 * pkey = EVP_EC_gen(curvename); OR
 * pkey = EVP_PKEY_Q_keygen(libctx, propq, "EC", curvename);
 */
static EVP_PKEY* do_ec_keygen(void)
{
	/*
	 * The libctx and propq can be set if required, they are included here
	 * to show how they are passed to EVP_PKEY_CTX_new_from_name().
	 */
	OSSL_LIB_CTX* _ossl_lib_ctx = NULL;
	const char* propq = NULL;
	EVP_PKEY* key = NULL;
	OSSL_PARAM _ossl_param[3];
	EVP_PKEY_CTX* _evp_pkey_ctx = NULL;
	const char* curvename = "P-256"; /*! 椭圆曲线的名字 */
	int use_cofactordh = 1;

	_evp_pkey_ctx = EVP_PKEY_CTX_new_from_name(_ossl_lib_ctx, "EC", propq);
	if (_evp_pkey_ctx == NULL) {
		fprintf(stderr, "EVP_PKEY_CTX_new_from_name() failed\n");
		goto cleanup;
	}

	if (EVP_PKEY_keygen_init(_evp_pkey_ctx) <= 0) {
		fprintf(stderr, "EVP_PKEY_keygen_init() failed\n");
		goto cleanup;
	}

	_ossl_param[0] = OSSL_PARAM_construct_utf8_string(OSSL_PKEY_PARAM_GROUP_NAME,
		(char*)curvename, 0);
	/*
	 * This is an optional parameter.
	 * For many curves where the cofactor is 1, setting this has no effect.
	 */
	_ossl_param[1] = OSSL_PARAM_construct_int(OSSL_PKEY_PARAM_USE_COFACTOR_ECDH,
		&use_cofactordh);
	_ossl_param[2] = OSSL_PARAM_construct_end();
	if (!EVP_PKEY_CTX_set_params(_evp_pkey_ctx, _ossl_param)) {
		fprintf(stderr, "EVP_PKEY_CTX_set_params() failed\n");
		goto cleanup;
	}

	fprintf(stdout, "Generating EC key\n\n");
	if (EVP_PKEY_generate(_evp_pkey_ctx, &key) <= 0) {
		fprintf(stderr, "EVP_PKEY_generate() failed\n");
		goto cleanup;
	}
cleanup:
	EVP_PKEY_CTX_free(_evp_pkey_ctx);
	return key;
}

/*
 * The following code shows how retrieve key data from the generated
 * EC key. See doc/man7/EVP_PKEY-EC.pod for more information.
 *
 * EVP_PKEY_print_private() could also be used to display the values.
 */
static int get_key_values(EVP_PKEY* pkey)
{
	int ret = 0;
	char out_curvename[80];
	unsigned char out_pubkey[80];
	unsigned char out_privkey[80];
	BIGNUM* out_priv = NULL;
	size_t out_pubkey_len, out_privkey_len = 0;

	if (!EVP_PKEY_get_utf8_string_param(pkey, OSSL_PKEY_PARAM_GROUP_NAME,
		out_curvename, sizeof(out_curvename),
		NULL)) {
		fprintf(stderr, "Failed to get curve name\n");
		goto cleanup;
	}

	if (!EVP_PKEY_get_octet_string_param(pkey, OSSL_PKEY_PARAM_PUB_KEY,
		out_pubkey, sizeof(out_pubkey),
		&out_pubkey_len)) {
		fprintf(stderr, "Failed to get public key\n");
		goto cleanup;
	}

	if (!EVP_PKEY_get_bn_param(pkey, OSSL_PKEY_PARAM_PRIV_KEY, &out_priv)) {
		fprintf(stderr, "Failed to get private key\n");
		goto cleanup;
	}

	out_privkey_len = BN_bn2bin(out_priv, out_privkey);
	if (out_privkey_len <= 0 || out_privkey_len > sizeof(out_privkey)) {
		fprintf(stderr, "BN_bn2bin failed\n");
		goto cleanup;
	}

	fprintf(stdout, "Curve name: %s\n", out_curvename);
	fprintf(stdout, "Public key:\n");
	BIO_dump_indent_fp(stdout, out_pubkey, (int)out_pubkey_len, 2);
	fprintf(stdout, "Private Key:\n");
	BIO_dump_indent_fp(stdout, out_privkey, (int)out_privkey_len, 2);

	ret = 1;
cleanup:
	/* Zeroize the private key data when we free it */
	BN_clear_free(out_priv);
	return ret;
}

int main(void)
{
	int ret = EXIT_FAILURE;
	EVP_PKEY* _evp_pkey_ec;

	_evp_pkey_ec = do_ec_keygen();
	if (_evp_pkey_ec == NULL)
		goto cleanup;

	if (!get_key_values(_evp_pkey_ec))
		goto cleanup;

	/*
	 * At this point we can write out the generated key using
	 * i2d_PrivateKey() and i2d_PublicKey() if required.
	 */
	ret = EXIT_SUCCESS;
cleanup:
	if (ret != EXIT_SUCCESS)
		ERR_print_errors_fp(stderr);

	EVP_PKEY_free(_evp_pkey_ec);
	return ret;
}

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