调用OpenSSL实现数字签名功能例程（一）

最新推荐文章于 2025-06-16 09:13:29 发布

转载最新推荐文章于 2025-06-16 09:13:29 发布 · 1.7k 阅读

本文提供了一个使用OpenSSL实现数字签名功能的C++代码示例，详细介绍了初始化OpenSSL、获取签名、验证签名的过程，并通过一个简单的主函数展示了整个流程的应用。

// sign.cpp : Defines the entry point for the console application.
//

#include "stdafx.h"

#include <stdio.h>
#include <openssl/rsa.h>
#include <openssl/evp.h>
#include <openssl/objects.h>
#include <openssl/x509.h>
#include <openssl/err.h>
#include <openssl/pem.h>
#include <openssl/ssl.h>

#pragma comment(lib, "libeay32.lib")
#pragma comment(lib, "ssleay32.lib")

/*
PKCS7Sign.cpp
Auth：Kagula
功能：调用OpenSSL实现数字签名功能例程（一）
环境：VS2008+SP1,OpenSSL1.0.1
*/

void InitOpenSSL()
{
ERR_load_crypto_strings();
}

unsigned char * GetSign(char* keyFile,char* plainText,unsigned char* cipherText,unsigned int *cipherTextLen)
{
FILE* fp = fopen (keyFile, "r");
if (fp == NULL)
return NULL;

/* Read private key */
EVP_PKEY* pkey = PEM_read_PrivateKey(fp, NULL, NULL, NULL);
fclose (fp);

if (pkey == NULL) {
ERR_print_errors_fp (stderr);
return NULL;
}

/* Do the signature */
EVP_MD_CTX md_ctx;
EVP_SignInit (&md_ctx, EVP_sha1());
EVP_SignUpdate (&md_ctx, plainText, strlen(plainText));
int err = EVP_SignFinal (&md_ctx, cipherText, cipherTextLen, pkey);

if (err != 1) {
ERR_print_errors_fp(stderr);
return NULL;
}

EVP_PKEY_free(pkey);

return cipherText;
}

bool VerifySign(char* certFile,unsigned char* cipherText,unsigned int cipherTextLen,char* plainText)
{
/* Get X509 */
FILE* fp = fopen (certFile, "r");
if (fp == NULL)
return false;
X509* x509 = PEM_read_X509(fp, NULL, NULL, NULL);
fclose (fp);

if (x509 == NULL) {
ERR_print_errors_fp (stderr);
return false;
}

/* Get public key - eay */
EVP_PKEY *pkey=X509_get_pubkey(x509);
if (pkey == NULL) {
ERR_print_errors_fp (stderr);
return false;
}

/* Verify the signature */
EVP_MD_CTX md_ctx;
EVP_VerifyInit (&md_ctx, EVP_sha1());
EVP_VerifyUpdate (&md_ctx, plainText, strlen((char*)plainText));
int err = EVP_VerifyFinal (&md_ctx, cipherText, cipherTextLen, pkey);
EVP_PKEY_free (pkey);

if (err != 1) {
ERR_print_errors_fp (stderr);
return false;
}
return true;
}

int _tmain(int argc, _TCHAR* argv[])
{
char certFile[] = "cert.pem";//含共匙
char keyFile[] = "key.pem";//含私匙

char plainText[] = "I owe you...";//待签名的明文
unsigned char cipherText[1024*4];
unsigned int cipherTextLen;

InitOpenSSL();

memset(cipherText,0,sizeof(cipherText));
if(NULL==GetSign(keyFile,plainText,cipherText,&cipherTextLen))
{
printf("签名失败！\n");
return -1;
}

if(false==VerifySign(certFile,cipherText,cipherTextLen,plainText))
{
printf("验证签名失败！\n");
return -2;
}

printf ("Signature Verified Ok.\n");
return 0;
}