openssl编程之rsa加解密

测试代码:

#include <openssl/rsa.h>
#include <openssl/pem.h>
#include <openssl/err.h>
#include <string.h>

void handle_openssl_errors() {
	ERR_print_errors_fp(stderr);
	abort();
}


RSA* load_public_key_from_file(const char* filename) {
	BIO* bio = BIO_new_file(filename, "r");
	if (!bio) return NULL;

	RSA* rsa = PEM_read_bio_RSA_PUBKEY(bio, NULL, NULL, NULL);
	BIO_free(bio);
	return rsa;
}

RSA* load_private_key_from_file(const char* filename) {
	BIO* bio = BIO_new_file(filename, "r");
	if (!bio) return NULL;

	RSA* rsa = PEM_read_bio_RSAPrivateKey(bio, NULL, NULL, NULL);
	BIO_free(bio);
	return rsa;
}


int openssl_rsa() {
	// 初始化 OpenSSL
	OpenSSL_add_all_algorithms();
	ERR_load_crypto_strings();

	RSA* rsa_key = NULL;
	FILE* fp = NULL;
	const char* plaintext = "this is xiaohai";
	int plaintext_len = strlen(plaintext);

	// 用于存储加密后的数据和解密后的数据
	unsigned char encrypted[4098] = {};
	unsigned char decrypted[4098] = {};

	int encrypted_len, decrypted_len;

#if 0
	// 1. 使用公钥加密
	printf("1. Encrypting with public key...\n");
	fp = fopen("pub.pem", "r");
	if (!fp) {
		perror("Error opening public key file");
		handle_openssl_errors();
	}

	// 从文件加载公钥
	rsa_key = PEM_read_RSA_PUBKEY(fp, &rsa_key, NULL, NULL);
	fclose(fp);
	if (!rsa_key) {
		fprintf(stderr, "Error reading public key\n");
		handle_openssl_errors();
	}
#endif
	rsa_key=load_public_key_from_file("pub.pem");

	// 执行加密
	// RSA_PKCS1_OAEP_PADDING 是推荐的现代填充方式，比 RSA_PKCS1_PADDING 更安全
	encrypted_len = RSA_public_encrypt(plaintext_len,
		(unsigned char*)plaintext,
		encrypted,
		rsa_key,
		RSA_PKCS1_OAEP_PADDING);
	if (encrypted_len == -1) {
		fprintf(stderr, "Error encrypting message\n");
		handle_openssl_errors();
	}
	printf("Encryption successful. Encrypted length: %d\n", encrypted_len);

	// 释放公钥结构体
	RSA_free(rsa_key);
	rsa_key = NULL;

#if 0
	// 2. 使用私钥解密
	printf("\n2. Decrypting with private key...\n");
	fp = fopen("pri.pem", "r");
	if (!fp) {
		perror("Error opening private key file");
		handle_openssl_errors();
	}

	// 从文件加载私钥
	rsa_key = PEM_read_RSAPrivateKey(fp, &rsa_key, NULL, NULL);
	fclose(fp);
	if (!rsa_key) {
		fprintf(stderr, "Error reading private key\n");
		handle_openssl_errors();
	}
#endif

	rsa_key = load_private_key_from_file("pri.pem");

	// 执行解密
	decrypted_len = RSA_private_decrypt(encrypted_len,
		encrypted,
		decrypted,
		rsa_key,
		RSA_PKCS1_OAEP_PADDING);
	if (decrypted_len == -1) {
		fprintf(stderr, "Error decrypting message\n");
		handle_openssl_errors();
	}

	// 添加字符串终止符并打印结果
	decrypted[decrypted_len] = '\0';
	printf("Decryption successful. Decrypted text: '%s'\n", decrypted);

	// 清理
	RSA_free(rsa_key);
	EVP_cleanup();
	CRYPTO_cleanup_all_ex_data();
	ERR_free_strings();

	return 0;
}