网上找到的大部分都是旧API，新版OpenSSL推荐使用EVP系列接口，在此记录下EVP方式的MD5哈希实现代码：
#include "openssl/conf.h"
#include "openssl/evp.h"
#include "openssl/err.h"
#include "openssl/engine.h"
void handle_errors()
{
ERR_print_errors_fp(stderr);
abort();
}
std::string md5_str(const std::string & str)
{
const auto * md = EVP_get_digestbyname("MD5");
if (nullptr == md)
{
std::cerr << "Failed to EVP_get_digestbyname MD5!" << std::endl;
return "";
}
unsigned char buf[EVP_MAX_MD_SIZE] = {};
unsigned int olen = EVP_MAX_MD_SIZE;
EVP_MD_CTX * ctx = EVP_MD_CTX_new();
if (nullptr == ctx)
{
std::cerr << "Failed to EVP_MD_CTX_new!" << std::endl;
return "";
}
if (1 != EVP_DigestInit(ctx, md))
{
handle_errors();
return "";
}
if (1 != EVP_DigestUpdate(ctx, str.data(), str.length()))
{
handle_errors();
return "";
}
if (1 != EVP_DigestFinal(ctx, buf, &olen))
{
handle_errors();
return "";
}
EVP_MD_CTX_free(ctx);
return { reinterpret_cast<char*>(buf), olen };
}
int main()
{
OpenSSL_add_all_digests();
const std::string plain = "test1234";
const std::string hash = md5_str(plain);
std::cout << "plain: " << plain << " md5 hash: " << hash << std::endl;
return EXIT_SUCCESS;
}
后面有时间再增加AES等的EVP实现代码
