openssl3.2 - 官方demo学习 - digest - EVP_MD_xof.c

概述

使用支持XOF方式的摘要算法(e.g. SHAKE256), 对buffer进行摘要, 并和预留的摘要值进行比对

笔记

/*!
\file EVP_MD_xof.c
\note openssl3.2 - 官方demo学习 - digest - EVP_MD_xof.c
使用支持XOF方式的摘要算法(e.g. SHAKE256), 对buffer进行摘要, 并和预留的摘要值进行比对
*//*-* Copyright 2022-2023 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 <string.h>
#include <openssl/err.h>
#include <openssl/evp.h>
#include <openssl/core_names.h>#include "my_openSSL_lib.h"/** Example of using an extendable-output hash function (XOF). A XOF is a hash* function with configurable output length and which can generate an* arbitrarily large output.** This example uses SHAKE256, an extendable output variant of SHA3 (Keccak).** To generate different output lengths, you can pass a single integer argument* on the command line, which is the output size in bytes. By default, a 20-byte* output is generated and (for this length only) a known answer test is* performed.*//* Our input to the XOF hash function. */
const char message[] = "This is a test message.";/* Expected output when an output length of 20 bytes is used. */
static const char known_answer[] = {0x52, 0x97, 0x93, 0x78, 0x27, 0x58, 0x7d, 0x62,0x8b, 0x00, 0x25, 0xb5, 0xec, 0x39, 0x5e, 0x2d,0x7f, 0x3e, 0xd4, 0x19
};/** A property query used for selecting the SHAKE256 implementation.*/
static const char *propq = NULL;int main(int argc, char **argv)
{int ret = EXIT_FAILURE;OSSL_LIB_CTX *_ossl_lib_ctx = NULL;EVP_MD *_evp_md = NULL;EVP_MD_CTX *_evp_md_ctx = NULL;unsigned int digest_len = 20;int digest_len_i;unsigned char *_psz_digest = NULL;/* Allow digest length to be changed for demonstration purposes. */if (argc > 1) {digest_len_i = atoi(argv[1]);if (digest_len_i <= 0) {fprintf(stderr, "Specify a non-negative digest length\n");goto end;}digest_len = (unsigned int)digest_len_i;}/** Retrieve desired algorithm. This must be a hash algorithm which supports* XOF.*/_evp_md = EVP_MD_fetch(_ossl_lib_ctx, "SHAKE256", propq);if (_evp_md == NULL) {fprintf(stderr, "Failed to retrieve SHAKE256 algorithm\n");goto end;}/* Create context. */_evp_md_ctx = EVP_MD_CTX_new();if (_evp_md_ctx == NULL) {fprintf(stderr, "Failed to create digest context\n");goto end;}/* Initialize digest context. */if (EVP_DigestInit(_evp_md_ctx, _evp_md) == 0) {fprintf(stderr, "Failed to initialize digest\n");goto end;}/** Feed our message into the digest function.* This may be called multiple times.*/if (EVP_DigestUpdate(_evp_md_ctx, message, sizeof(message)) == 0) {fprintf(stderr, "Failed to hash input message\n");goto end;}/* Allocate enough memory for our digest length. */_psz_digest = OPENSSL_malloc(digest_len);if (_psz_digest == NULL) {fprintf(stderr, "Failed to allocate memory for digest\n");goto end;}/* Get computed digest. The digest will be of whatever length we specify. */if (EVP_DigestFinalXOF(_evp_md_ctx, _psz_digest, digest_len) == 0) {fprintf(stderr, "Failed to finalize hash\n");goto end;}printf("Output digest:\n");BIO_dump_indent_fp(stdout, _psz_digest, digest_len, 2); /*!< 参数4是dump的宽度, 默认是16, 不用填写, 或者给0都行 *//* If digest length is 20 bytes, check it matches our known answer. */if (digest_len == 20) {/** Always use a constant-time function such as CRYPTO_memcmp* when comparing cryptographic values. Do not use memcmp(3).*/if (CRYPTO_memcmp(_psz_digest, known_answer, sizeof(known_answer)) != 0) {fprintf(stderr, "Output does not match expected result\n");goto end;}}ret = EXIT_SUCCESS;
end:OPENSSL_free(_psz_digest);EVP_MD_CTX_free(_evp_md_ctx);EVP_MD_free(_evp_md);OSSL_LIB_CTX_free(_ossl_lib_ctx);return ret;
}

END