使用openssl libcrypto使用RSA私钥解密数据时使用RSA_NO_PADDING

时间:2017-03-23 04:07:23

标签: c++ encryption openssl rsa libcrypto

我生成了RSA私钥和公钥,如下所示,

openssl genpkey -algorithm RSA -out key.pem -pkeyopt rsa_keygen_bits:2048
openssl rsa -pubout -in pri.key -out pub.key

加密文本文件如下,

openssl pkeyutl -encrypt -pubin -inkey ~/pub.key -in ~/1.txt -out ~/1e.txt

然后我写了下面的程序来解密加密文件。但是,似乎解密没有按预期工作。

#include <openssl/evp.h>
#include <openssl/rsa.h>
#include <openssl/pem.h>
#include <openssl/err.h>
#include <openssl/conf.h>
#include <iostream>

using namespace std;

void
cleanup()
{
    EVP_cleanup();
    CRYPTO_cleanup_all_ex_data();
    ERR_free_strings();
}

int
main(int argc, char** argv)
{
    ERR_load_crypto_strings();
    OpenSSL_add_all_algorithms();
    OPENSSL_config(nullptr);

    cout<<"Initialize crypto library done"<<endl;

    EVP_PKEY * key = EVP_PKEY_new();
    if (key == nullptr) {
        cout<<"Failed to contruct new key"<<endl;
        return 1;
    }
    FILE * fpri = nullptr;
    fpri = fopen("/home/stack/pri.key", "r");
    if (fpri == nullptr) {
        cout<<"Failed to load private key"<<endl;
        return 1;
    }
    key = PEM_read_PrivateKey(fpri, &key, nullptr, nullptr);
    if (key == nullptr) {
        std::cout<<"Read private key failed"<<endl;
        return 1;
    }
    cout<<"load private key successfully"<<endl;
    EVP_PKEY_CTX *ctx = nullptr;
    ctx = EVP_PKEY_CTX_new(key, nullptr);
    EVP_PKEY_decrypt_init(ctx);
    EVP_PKEY_CTX_set_rsa_padding(ctx, RSA_NO_PADDING);

    size_t outlen = 0, inlen = 0;
    unsigned char * out = nullptr, * in = nullptr;

    char buf[1024];
    FILE * fe = nullptr;
    fe = fopen("/home/stack/1e.txt", "r");
    size_t len = fread(buf, 1, sizeof(buf),  fe);
    cout<<"data input length is "<<len<<endl;
    EVP_PKEY_decrypt(ctx, NULL, &outlen, in, inlen);
    cout<<"outlen is "<<outlen<<endl;

    out = (unsigned char*)OPENSSL_malloc(outlen);
    EVP_PKEY_decrypt(ctx, out, &outlen, in, inlen);
    cout<<"decrypted data "<<out<<endl;
    cleanup();

    return 0;

}

执行代码时,结果如下,

[stack@agent ~]$ ./test
Initialize crypto library done
load private key successfully
data input length is 256
outlen is 256
decrypted data

似乎解密的数据长度不正确且无法打印。

当我注释掉指令“EVP_PKEY_CTX_set_rsa_padding(ctx,RSA_NO_PADDING);”时,它运作良好。

我也尝试过RSA_PKCS1_OAEP_PADDING,它也没用。如果未设置RSA PADDING,则可以正常工作。

我的问题如下,

  1. 以下命令使用了哪个填充?

    openssl pkeyutl -encrypt -pubin -inkey ~/pub.key -in ~/1.txt -out ~/1e.txt
    
  2. RSA加密/解密需要填充吗?如果是这样,我怎么能应用填充机制?

1 个答案:

答案 0 :(得分:0)

如果在openssl pkeyutl加密中使用非默认填充,则应使用EVP_PKEY_CTX_set_rsa_padding。有关-rsa_padding_mode

的详细信息,请参阅openssl pkeyutl documentation