openssl3.2 - 官方demo学习 - mac - gmac.c

文章目录

• • [openssl3.2 - 官方demo学习 - mac - gmac.c](#openssl3.2 - 官方demo学习 - mac - gmac.c)
  • 概述
  • 笔记
  • END

openssl3.2 - 官方demo学习 - mac - gmac.c

概述

使用GMAC算法, 设置参数(指定加密算法 e.g. AES-128-GCM, 设置iv)

用key执行初始化, 然后对明文生成MAC数据

官方注释给出建议, key, iv最好不要硬编码出现在程序中

笔记

/*!
\file gmac.c
\note openssl3.2 - 官方demo学习 - mac - gmac.c
使用GMAC算法, 设置参数(指定加密算法 e.g. AES-128-GCM, 设置iv)
用key执行初始化, 然后对明文生成MAC数据
*/

/*
 * 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
 */

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

#include "my_openSSL_lib.h"

 /*
  * Taken from NIST's GCM Test Vectors
  * http://csrc.nist.gov/groups/STM/cavp/
  */

  /*
   * Hard coding the key into an application is very bad.
   * It is done here solely for educational purposes.
   */
static unsigned char key[] = {
	0x77, 0xbe, 0x63, 0x70, 0x89, 0x71, 0xc4, 0xe2,
	0x40, 0xd1, 0xcb, 0x79, 0xe8, 0xd7, 0x7f, 0xeb
};

/*
 * The initialisation vector (IV) is better not being hard coded too.
 * Repeating password/IV pairs compromises the integrity of GMAC.
 * The IV is not considered secret information and is safe to store with
 * an encrypted password.
 */
static unsigned char iv[] = {
	0xe0, 0xe0, 0x0f, 0x19, 0xfe, 0xd7, 0xba,
	0x01, 0x36, 0xa7, 0x97, 0xf3
};

static unsigned char data[] = {
	0x7a, 0x43, 0xec, 0x1d, 0x9c, 0x0a, 0x5a, 0x78,
	0xa0, 0xb1, 0x65, 0x33, 0xa6, 0x21, 0x3c, 0xab
};

static const unsigned char expected_output[] = {
	0x20, 0x9f, 0xcc, 0x8d, 0x36, 0x75, 0xed, 0x93,
	0x8e, 0x9c, 0x71, 0x66, 0x70, 0x9d, 0xd9, 0x46
};

/*
 * A property query used for selecting the GMAC implementation and the
 * underlying GCM mode cipher.
 */
static char* propq = NULL;

int main(int argc, char** argv)
{
	int ret = EXIT_FAILURE;
	EVP_MAC* _evp_mac = NULL;
	EVP_MAC_CTX* _evp_mac_ctx = NULL;
	unsigned char out[16];
	OSSL_PARAM _ossl_param_ary[4], * p_ossl_param = _ossl_param_ary;
	OSSL_LIB_CTX* _ossl_lib_ctx = NULL;
	size_t out_len = 0;

	_ossl_lib_ctx = OSSL_LIB_CTX_new();
	if (_ossl_lib_ctx == NULL) {
		fprintf(stderr, "OSSL_LIB_CTX_new() returned NULL\n");
		goto end;
	}

	/* Fetch the GMAC implementation */
	_evp_mac = EVP_MAC_fetch(_ossl_lib_ctx, "GMAC", propq);
	if (_evp_mac == NULL) {
		fprintf(stderr, "EVP_MAC_fetch() returned NULL\n");
		goto end;
	}

	/* Create a context for the GMAC operation */
	_evp_mac_ctx = EVP_MAC_CTX_new(_evp_mac);
	if (_evp_mac_ctx == NULL) {
		fprintf(stderr, "EVP_MAC_CTX_new() returned NULL\n");
		goto end;
	}

	/* GMAC requires a GCM mode cipher to be specified */
	*p_ossl_param++ = OSSL_PARAM_construct_utf8_string(OSSL_MAC_PARAM_CIPHER,
		"AES-128-GCM", 0);

	/*
	 * If a non-default property query is required when fetching the GCM mode
	 * cipher, it needs to be specified too.
	 */
	if (propq != NULL)
		*p_ossl_param++ = OSSL_PARAM_construct_utf8_string(OSSL_MAC_PARAM_PROPERTIES,
			propq, 0);

	/* Set the initialisation vector (IV) */
	*p_ossl_param++ = OSSL_PARAM_construct_octet_string(OSSL_CIPHER_PARAM_IV,
		iv, sizeof(iv));
	*p_ossl_param = OSSL_PARAM_construct_end();

	/* Initialise the GMAC operation */
	if (!EVP_MAC_init(_evp_mac_ctx, key, sizeof(key), _ossl_param_ary)) {
		fprintf(stderr, "EVP_MAC_init() failed\n");
		goto end;
	}

	/* Make one or more calls to process the data to be authenticated */
	if (!EVP_MAC_update(_evp_mac_ctx, data, sizeof(data))) {
		fprintf(stderr, "EVP_MAC_update() failed\n");
		goto end;
	}

	/* Make one call to the final to get the MAC */
	if (!EVP_MAC_final(_evp_mac_ctx, out, &out_len, sizeof(out))) {
		fprintf(stderr, "EVP_MAC_final() failed\n");
		goto end;
	}

	printf("Generated MAC:\n");
	BIO_dump_indent_fp(stdout, out, (int)out_len, 2);
	putchar('\n');

	if (out_len != sizeof(expected_output)) {
		fprintf(stderr, "Generated MAC has an unexpected length\n");
		goto end;
	}

	if (CRYPTO_memcmp(expected_output, out, sizeof(expected_output)) != 0) {
		fprintf(stderr, "Generated MAC does not match expected value\n");
		goto end;
	}

	ret = EXIT_SUCCESS;
end:
	EVP_MAC_CTX_free(_evp_mac_ctx);
	EVP_MAC_free(_evp_mac);
	OSSL_LIB_CTX_free(_ossl_lib_ctx);
	if (ret != EXIT_SUCCESS)
		ERR_print_errors_fp(stderr);
	return ret;
}

END