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SHA256 例程

一般文件的完整性要使用md5或者sha进行完整性校验，这里提供两个函数，

intact_update_sha 是计算指定文件SHA值并保存到SHA文件

intact_check_sha 计算文件SHA值并和SHA文件进行对比

编译方法：

gcc demo.c -lssl -lcrypto

#include <stdio.h>
#include <openssl/sha.h>
#include <string.h>
#include <unistd.h>
#include <sys/stat.h>
#include <sys/types.h>
#include <openssl/md5.h>
#include <stdlib.h>enum {ERR_OK,ERR_FAIL,ERR_OPEN,ERR_OPEN_SHA,ERR_PATH,ERR_PARAM,ERR_NOEXIST,ERR_NOEXIST_SHA,ERR_KEY,ERR_MALLOC,};#define MAX_BUFFER_SIZE      1024
#define SHA_FILE_PATH        "/home/hfs/sha/%s.sha"
#define SHA_FILE_DIR         "/home/hfs/sha"static int intact_get_sha_file_path(char *path)
{int offset = 0;for (int i = 0; i < strlen(path); i++) {if (*(path + i) == '/')offset = i;}return offset;
}
int intact_check_sha(char *path)
{SHA256_CTX ctx;char buffer[MAX_BUFFER_SIZE];char sha_str[MAX_BUFFER_SIZE];int len = 0;FILE *fp = NULL;FILE *fp_sha = NULL;unsigned char sha[SHA256_DIGEST_LENGTH];char tmp[MAX_BUFFER_SIZE] = {0};char sha_file[MAX_BUFFER_SIZE] = {0};int offset;if (path == NULL) {return ERR_PARAM;}if (access(path, F_OK)) {return ERR_NOEXIST;}strcpy(tmp, path);if (tmp[strlen(tmp) - 1] == '/') {tmp[strlen(tmp) - 1] = '\0';}offset = intact_get_sha_file_path(tmp);if (offset == 0) {return ERR_PATH;}sprintf(sha_file, SHA_FILE_PATH, tmp + offset + 1);if (access(sha_file, F_OK)) {return ERR_NOEXIST_SHA;}fp = fopen(path, "r");if (fp == NULL) {  return ERR_OPEN;  }fp_sha = fopen(sha_file, "r");if (fp == NULL) {  fclose(fp);fp = NULL;return ERR_OPEN_SHA;  } SHA256_Init(&ctx);while ((len = fread(buffer, 1, MAX_BUFFER_SIZE, fp)) > 0) {SHA256_Update(&ctx, buffer, len);  memset(buffer, 0, sizeof(buffer));  } SHA256_Final(&(sha[0]), &ctx);sprintf(sha_str, "%02x%02x%02x%02x%02x%02x%02x%02x%02x%02x%02x%02x%02x%02x%02x%02x",sha[0], sha[1], sha[2], sha[3], sha[4], sha[5], sha[6], sha[7],sha[8], sha[9], sha[10], sha[11], sha[12], sha[13], sha[14], sha[15]);fread(buffer, 1, MAX_BUFFER_SIZE, fp_sha);if (strncmp(sha_str, buffer, 32) == 0) {fclose(fp);fp = NULL;fclose(fp_sha);fp_sha = NULL;return ERR_OK;}fclose(fp);fp = NULL;fclose(fp_sha);fp_sha = NULL;return ERR_FAIL;
}
int intact_update_sha(char *path)
{SHA256_CTX ctx;char buffer[MAX_BUFFER_SIZE];char sha_str[MAX_BUFFER_SIZE] = {0};int len = 0;FILE *fp = NULL;FILE *fp_sha = NULL;unsigned char sha[SHA256_DIGEST_LENGTH];char tmp[MAX_BUFFER_SIZE] = {0};char sha_file[MAX_BUFFER_SIZE] = {0};int offset;if (path == NULL) {return ERR_PARAM;}if (access(path, F_OK)) {return ERR_NOEXIST;}strcpy(tmp, path);if (tmp[strlen(tmp) - 1] == '/') {tmp[strlen(tmp) - 1] = '\0';}offset = intact_get_sha_file_path(tmp);if (offset == 0) {return ERR_PATH;}sprintf(sha_file, SHA_FILE_PATH, tmp + offset + 1);if (access(SHA_FILE_DIR, F_OK)) {mkdir(SHA_FILE_DIR, S_IRUSR | S_IWUSR | S_IXUSR);}fp = fopen(path, "r");if (fp == NULL) {  return ERR_OPEN;  }fp_sha = fopen(sha_file, "w+");if (fp == NULL) {  fclose(fp);fp = NULL;return ERR_OPEN_SHA;  } SHA256_Init(&ctx);while ((len = fread(buffer, 1, MAX_BUFFER_SIZE, fp)) > 0) {SHA256_Update(&ctx, buffer, len);  memset(buffer, 0, sizeof(buffer));  } SHA256_Final(&(sha[0]), &ctx);sprintf(sha_str, "%02x%02x%02x%02x%02x%02x%02x%02x%02x%02x%02x%02x%02x%02x%02x%02x",sha[0], sha[1], sha[2], sha[3], sha[4], sha[5], sha[6], sha[7],sha[8], sha[9], sha[10], sha[11], sha[12], sha[13], sha[14], sha[15]);fwrite(sha_str, 1, MAX_BUFFER_SIZE, fp_sha);fclose(fp);fp = NULL;fclose(fp_sha);fp_sha = NULL;return ERR_OK;
}