openssl从内存中读取私钥进行签名

#include <stdio.h>
#include <stdlib.h>
#ifdef WIN32
#include <windows.h>
#endif
#include "openssl/rsa.h"
#include "openssl/pem.h"
#include "Base64.h"
#ifdef WIN32
#pragma comment(lib,"User32.lib")
#pragma comment(lib,"Advapi32.lib")
#pragma comment(lib,"Gdi32.lib")
#pragma comment(lib,"libeay32.lib")
#pragma comment(lib,"ssleay32.lib")
#endif

// 私钥解密 
std::string rsa_pri_decrypt(const std::string &cipherText, const std::string &priKey) 
{ 
std::string strRet; 
RSA *rsa = RSA_new(); 
BIO *keybio; 
keybio = BIO_new_mem_buf((unsigned char *)priKey.c_str(), -1); 

// 此处有三种方法 
// 1, 读取内存里生成的密钥对，再从内存生成rsa 
// 2, 读取磁盘里生成的密钥对文本文件，在从内存生成rsa 
// 3，直接从读取文件指针生成rsa 
rsa = PEM_read_bio_RSAPrivateKey(keybio, &rsa, NULL, NULL); 

int len = RSA_size(rsa); 
char *decryptedText = (char *)malloc(len + 1); 
memset(decryptedText, 0, len + 1); 

// 解密函数 
int ret = RSA_private_decrypt(cipherText.length(), (const unsigned char*)cipherText.c_str(), (unsigned char*)decryptedText, rsa, RSA_PKCS1_PADDING); 
if (ret >= 0) 
strRet = std::string(decryptedText, ret); 

// 释放内存 
free(decryptedText); 
BIO_free_all(keybio); 
RSA_free(rsa); 

return strRet; 
}