libopenssl 实现私钥加密公钥解密

在需要验证可信来源时，需要用到签名验签。因此，需要使用私钥加密，公钥解密，取得被加密的信息。这就会使用到私钥加密，公钥解密的场景了。

参考：
https://github.com/openssl/openssl/issues/20493
https://blog.csdn.net/wq897387/article/details/114129820

使用 openssl-1.1.1 版本，3.x版本API不一样。

#include <stdio.h>
#include <string.h>
#include <stdint.h>
#include "openssl/ssl.h"
#include "openssl/pem.h"
#include "openssl/rsa.h"
#include "openssl/bio.h"#define ENC_PADDING_TYPE  RSA_PKCS1_PADDINGint encrypt(uint8_t *data, int len, uint8_t *out)
{int ret = 0;uint8_t buff[8192] = {0};RSA *rsa = NULL;BIO *bio = NULL;int len1 = 0;FILE *f = fopen("private.pem", "r");if (!f) {printf("Open private.pem error\n");return -1;}len1 = fread(buff, 1, sizeof(buff), f);fclose(f);bio = BIO_new_mem_buf(buff, len1);if (!bio) {printf("BIO_new_mem_buf error\n");return -1;}rsa = PEM_read_bio_RSAPrivateKey(bio, &rsa, NULL, NULL);if (!rsa) {printf("PEM_read_bio_PrivateKey error\n");return -1;}ret = RSA_private_encrypt(len, data, out, rsa, ENC_PADDING_TYPE);if (!ret) {printf("RSA_private_encrypt error\n");RSA_free(rsa);BIO_free_all(bio);return -1;}RSA_free(rsa);BIO_free_all(bio);return 0;
}int decrypt(uint8_t *data, uint8_t *out)
{int ret = 0;uint8_t buff[8192] = {0};RSA *rsa = NULL;BIO *bio = NULL;FILE *f = fopen("public.pem", "r");if (!f) {printf("Open public.pem error\n");return -1;}fread(buff, 1, sizeof(buff), f);fclose(f);bio = BIO_new_mem_buf(buff, -1);if (!bio) {printf("BIO_new_mem_buf error\n");return -1;}rsa = PEM_read_bio_RSA_PUBKEY(bio, &rsa, NULL, NULL);if (!rsa) {printf("PEM_read_bio_RSA_PUBKEY error\n");return -1;}ret = RSA_public_decrypt(256, data, out, rsa, ENC_PADDING_TYPE);if (!ret) {printf("RSA_public_decrypt error\n");RSA_free(rsa);BIO_free_all(bio);return -1;}RSA_free(rsa);BIO_free_all(bio);return 0;
}int main(int argc, char **argv)
{const char text[8192] = "Hello world11111111111111111";uint8_t enc[8192] = {0};uint8_t dec[8192] = {0};printf("Text: %s\n", text);encrypt(text, strlen(text), enc);decrypt(enc, dec);printf("Decrypt: %s\n", dec);return 0;
}

经测试，私钥加密，公钥解密，支持的 padding 方式只有 RSA_PKCS1_PADDING 和 RSA_X931_PADDING 。公钥加密，私钥解密，各 padding 方式都是支持的。

运行结果：