基于OpenSSL,实现C语言RSA的PKCS8的公私钥编码

该博客探讨如何利用OpenSSL在C语言环境中实现RSA公私钥的PKCS8编码。内容涵盖PKCS1与PKCS8的区别,以及在工程中使用公私钥的场景。文章提供了主要函数及其调用方式,并指出需使用支持国密算法的OpenSSL库来避免编译错误。

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基于OpenSSL, 实现算法的 Engine专栏

基于OpenSSL, 实现数据编码转换专栏

本专栏订阅后可查看以下文章 

基于OpenSSL,实现C语言RSA的PKCS10的证书请求

基于OpenSSL,实现C语言SM2的PKCS10的证书请求 

基于OpenSSL,实现C语言SM2的PKCS8的公私钥编码

在日常工作中使用密码,就一定会接触到OpenSSL,这个算法库带给我们的东西太多太多,不管是密码算法层面,还有代码框架和使用技巧上更是值得我们去学习和专研。

在接触密码学中,在产品工程中会涉及到很多地方使用公私钥,RSA的公私钥有PKCS1和PKCS8两种格式,通常使用PKCS1格式,也是OpenSSL中经常使用的。

在经过历史的变革,PKCS1已经不能满足现在密钥类型的使用了(PKCS1公私钥编码只针对RSA),PKCS8除公私钥外,还包含有其他的附加信息。

主要函数如下:

// rsa私钥转pkcs8编码
int lbxx_pkcs8_i2d_rsa_memory_prikey(unsigned char *pucPrikey, unsigned int uiKeylen, unsigned char **ppucDer, unsigned int *puiLen);
// rsa公钥转pkcs8编码
int lbxx_pkcs8_i2d_rsa_memory_pubkey(unsigned char *pucPubkey, unsigned int uiKeylen, unsigned char **ppucDer, unsigned int *puiLen);
// pkcs8编码转rsa私钥
int lbxx_pkcs8_d2i_rsa_prikey(unsigned char *pucDer, unsigned int puiLen, unsigned char *pucPrikey, unsigned int *uiKeylen);
// pkcs8编码转rsa公钥
int lbxx_pkcs8_d2i_rsa_pubkey(unsigned char *pucDer, unsigned int puiLen, unsigned char *pucPubkey, unsigned int *uiKeylen);

int lbxx_pkcs8_i2d_rsa_generate_prikey(unsigned char **ppucDer, unsigned int *puiLen);
int lbxx_pkcs8_i2d_rsa_generate_pubkey(unsigned char **ppucDer, unsigned int *puiLen);

 具体调用方式如下,我添加了一些注释,便于理解,这里需要使用带有国密算法SM2/3/4的OpenSSL库编译,否则会报错误。

/****************************************************************
 * FileName:    pkcs8_rsa.c
 * Author:      labixiaoxin1849
 * Date:        2023-04-26
 * Description: RSA key for pkcs8 algorithm call of OpenSSL
 ****************************************************************/
 
#include <string.h>
#include <openssl/rsa.h>
#include <openssl/evp.h>
#include <openssl/x509.h>

static unsigned char kPrikey[] = {
	0x30, 0x82, 0x02, 0x5e, 0x02, 0x01, 0x00, 0x02, 0x81, 0x81, 0x00, 0xc9, 0x6d, 0x0e, 0xe5, 0xab,
	0x0e, 0x12, 0xf3, 0xe7, 0x41, 0xa3, 0x80, 0x43, 0xb2, 0xf6, 0x56, 0x04, 0x7d, 0x1d, 0x8d, 0x5e,
	0xb6, 0x3a, 0x22, 0x9b, 0x3e, 0x47, 0x93, 0x43, 0x65, 0x2d, 0x99, 0x7b, 0x92, 0x34, 0xbb, 0x22,
	0xa8, 0xdd, 0x79, 0x9d, 0x04, 0x31, 0x08, 0xaf, 0x9f, 0x59, 0x7c, 0x34, 0x04, 0x7a, 0x99, 0xf0,
	0xde, 0xa5, 0xcc, 0x8d, 0x9d, 0x15, 0x21, 0xe9, 0x92, 0x16, 0xe3, 0xfb, 0x77, 0xea, 0x64, 0x61,
	0x9b, 0x39, 0x9d, 0x73, 0x22, 0x28, 0xac, 0x88, 0xec, 0xee, 0xce, 0x6a, 0xc3, 0x6d, 0x25, 0x92,
	0xa2, 0xb5, 0x46, 0x9a, 0x75, 0x49, 0x35, 0x58, 0x84, 0x5e, 0xe4, 0x7b, 0x27, 0xe6, 0xa2, 0x2e,
	0xef, 0x5a, 0x2f, 0xef, 0x4f, 0xf4, 0x6d, 0x38, 0x54, 0x7d, 0x1e, 0xe7, 0x4f, 0xbd, 0x43, 0xa9,
	0x51, 0xc4, 0x3e, 0x6e, 0xe3, 0x09, 0x92, 0x0f, 0x71, 0x39, 0x7b, 0x02, 0x03, 0x01, 0x00, 0x01,
	0x02, 0x81, 0x80, 0x33, 0x9d, 0xa8, 0xc5, 0x9d, 0xd1, 0xdb, 0x75, 0x78, 0xfb, 0x4f, 0x04, 0x9d,
	0x54, 0x8c, 0xdf, 0x7a, 0x02, 0xfd, 0xc1, 0xae, 0x55, 0x90, 0x0c, 0x32, 0x30, 0x01, 0x73, 0x71,
	0x3f, 0xca, 0x31, 0x9c, 0x82, 0xd8, 0xd4, 0x63, 0x8b, 0x56, 0x45, 0xc5, 0xc0, 0xbf, 0x37, 0xf4,
	0x99, 0x26, 0xfb, 0x36, 0xf1, 0x36, 0xe1, 0x9f, 0xe1, 0xce, 0x26, 0xde, 0xdb, 0x34, 0x01, 0x1e,
	0xb3, 0x7a, 0xfd, 0xb8, 0x6e, 0x19, 0x6e, 0x0a, 0xe7, 0x06, 0x57, 0x42, 0xaa, 0x20, 0xa1, 0x53,
	0xde, 0x2e, 0x13, 0x09, 0x13, 0x41, 0x43, 0x4a, 0x19, 0x67, 0x95, 0x64, 0xa6, 0x89, 0x3d, 0x9a,
	0x26, 0xa5, 0x98, 0x6e, 0x09, 0x80, 0xe7, 0xe1, 0xe1, 0x27, 0x25, 0xee, 0x7a, 0x02, 0xc7, 0xf6,
	0x1b, 0x16, 0x9c, 0x87, 0x2e, 0x1c, 0x0a, 0xa1, 0x32, 0xcd, 0x18, 0x71, 0x50, 0x47, 0x0a, 0x80,
	0x6b, 0x23, 0x01, 0x02, 0x41, 0x00, 0xf0, 0x88, 0xc3, 0x0f, 0x6b, 0x2d, 0xf2, 0x9c, 0x54, 0xb2,
	0xd5, 0x4b, 0x6d, 0x67, 0xd2, 0x87, 0x13, 0x3a, 0x6a, 0x6c, 0xad, 0x9c, 0x69, 0x29, 0x96, 0x24,
	0x2e, 0xa9, 0xd5, 0x42, 0x3c, 0xc5, 0xa5, 0xee, 0x7b, 0xc9, 0x3b, 0x20, 0x7e, 0xfd, 0xec, 0xe9,
	0x51, 0x71, 0x9c, 0x97, 0x38, 0xf5, 0x68, 0x0f, 0x41, 0x9b, 0x9e, 0x35, 0x9d, 0xea, 0x2e, 0x5f,
	0x33, 0x68, 0x69, 0x59, 0xee, 0xc1, 0x02, 0x41, 0x00, 0xd6, 0x60, 0x91, 0x55, 0x52, 0xc9, 0x54,
	0x52, 0xa8, 0x10, 0x18, 0x45, 0xef, 0x98, 0x78, 0x7b, 0xca, 0xec, 0xa3, 0x23, 0x0f, 0x73, 0xb8,
	0x64, 0x2b, 0x8e, 0x04, 0xbe, 0x9e, 0x4b, 0xec, 0x6a, 0x91, 0x83, 0x74, 0xc3, 0xdf, 0xb3, 0x86,
	0x2e, 0x4b, 0xb1, 0x57, 0x60, 0x14, 0x8b, 0x2a, 0x41, 0x01, 0x7b, 0xa3, 0xcb, 0xf0, 0x32, 0xd3,
	0xdf, 0x82, 0xc0, 0x9f, 0x55, 0xc5, 0x96, 0xf3, 0x3b, 0x02, 0x41, 0x00, 0xe3, 0xcd, 0x62, 0x8f,
	0x93, 0xbe, 0x6c, 0x6b, 0x4a, 0x7c, 0x24, 0x2d, 0xcf, 0x6b, 0xe8, 0xa3, 0x2c, 0xbe, 0xc2, 0x54,
	0x33, 0x08, 0x53, 0x40, 0xa3, 0x85, 0x98, 0xfc, 0x17, 0x91, 0x27, 0xe5, 0x38, 0x85, 0x68, 0x8e,
	0xe8, 0x84, 0x9a, 0x40, 0xfa, 0xc2, 0xed, 0xf3, 0x5f, 0x8e, 0x88, 0xcf, 0x42, 0xc2, 0x50, 0x2c,
	0x85, 0xe5, 0xd9, 0xad, 0x14, 0x45, 0xed, 0x76, 0x11, 0x70, 0xaf, 0x01, 0x02, 0x41, 0x00, 0x8c,
	0x5b, 0xeb, 0xab, 0xde, 0xa9, 0x3c, 0xd1, 0x65, 0x82, 0x2c, 0x32, 0x55, 0xfe, 0x11, 0x1c, 0x94,
	0x2f, 0x3d, 0x5c, 0xae, 0x38, 0x49, 0x09, 0x24, 0xcf, 0x36, 0x62, 0x0b, 0xc8, 0x90, 0x00, 0xf2,
	0x47, 0x0c, 0x83, 0x56, 0x8a, 0xf7, 0x16, 0x86, 0xae, 0x95, 0x13, 0xae, 0x3f, 0xb3, 0xa9, 0x9e,
	0x2b, 0xf2, 0x81, 0x8b, 0x41, 0xec, 0x20, 0xd2, 0x3e, 0x05, 0xd4, 0xa5, 0xab, 0x00, 0x93, 0x02,
	0x41, 0x00, 0xe3, 0x57, 0xf0, 0x3e, 0xb7, 0xef, 0x99, 0xef, 0x82, 0x32, 0x63, 0x68, 0x38, 0x15,
	0x41, 0x46, 0x35, 0x71, 0x7f, 0xb5, 0x4f, 0x1a, 0x44, 0x61, 0x3a, 0xda, 0x83, 0xf0, 0xae, 0x1a,
	0x25, 0xe1, 0xd9, 0x73, 0xab, 0xbc, 0x8f, 0xbb, 0xb9, 0xcd, 0x56, 0xf8, 0x74, 0xc6, 0x78, 0x94,
	0xc9, 0x5f, 0xb6, 0x8d, 0x01, 0x07, 0x4d, 0x19, 0x90, 0x68, 0x37, 0x08, 0xc5, 0x71, 0xe5, 0x19,
	0x13, 0xcf
};

static unsigned char kPubkey[] = {
	0x30, 0x81, 0x89, 0x02, 0x81, 0x81, 0x00, 0xb0, 0x90, 0x8f, 0xe0, 0x58, 0x8b, 0xfd, 0x12, 0xf0,
	0xcb, 0x32, 0x1e, 0xce, 0x92, 0xc7, 0x78, 0xe1, 0x85, 0xfe, 0xf1, 0x4d, 0x2f, 0xe1, 0x1d, 0x4a,
	0xe4, 0x69, 0xde, 0x67, 0x16, 0x9c, 0x99, 0x24, 0x9b, 0x11, 0xe5, 0x47, 0x4b, 0x13, 0xa0, 0x2c,
	0x5d, 0xdb, 0x6d, 0xca, 0x00, 0x6b, 0xfc, 0x9f, 0x81, 0x9c, 0xb1, 0x5c, 0x44, 0x32, 0xee, 0xa4,
	0xa7, 0x51, 0x17, 0xed, 0x2e, 0x86, 0xe3, 0x32, 0xce, 0xc6, 0xfb, 0xb0, 0xee, 0xc3, 0xfb, 0x6c,
	0x91, 0x32, 0xed, 0x9a, 0x9d, 0x2f, 0xbf, 0x84, 0xea, 0xb3, 0x78, 0x42, 0x94, 0xff, 0xcd, 0x76,
	0x1d, 0x28, 0x2a, 0x4e, 0xaa, 0x12, 0xbe, 0x0b, 0xb6, 0x1a, 0x8e, 0x55, 0xe8, 0xd3, 0x2c, 0xff,
	0x16, 0xb8, 0xa0, 0x26, 0x03, 0xb5, 0xd6, 0x5e, 0x00, 0xba, 0xe7, 0xae, 0xa6, 0x0a, 0x43, 0x74,
	0xef, 0xe3, 0x9a, 0x1b, 0x44, 0xcc, 0x1b, 0x02, 0x03, 0x01, 0x00, 0x01
};

// 获得内存中公钥的PKCS8编码字符串
// 调用者需要释放ppucDer变量的内存
int lbxx_pkcs8_i2d_rsa_memory_prikey(unsigned char *pucPrikey, unsigned int uiKeylen, unsigned char **ppucDer, unsigned int *puiLen)
{
	int ret = -1;
	RSA *pRSA = NULL;
	EVP_PKEY *pKey = NULL;
	PKCS8_PRIV_KEY_INFO *p8 = NULL;
	const unsigned char *kptr = NULL;
	
	do{
		/* 初始化EVP */
		pKey = EVP_PKEY_new();
		if (!pKey) {
			break;
		}
		/* 设置EVP算法类型 */
		EVP_PKEY_set_type(pKey, EVP_PKEY_RSA);

		
		/* 从内存中设置密钥对 */
		kptr = kPrikey;
		pRSA = d2i_RSAPrivateKey(NULL, &kptr, sizeof(kPrikey));
		if (pRSA == NULL) {
			break;
		}
		if (!EVP_PKEY_set1_RSA(pKey, pRSA)) {
			break;
		}
		
		
		/* EVP_PKEY转为PKCS8 */
		p8 = EVP_PKEY2PKCS8(pKey);
		if (!p8) {
			break;
		}
		*puiLen = i2d_PKCS8_PRIV_KEY_INFO(p8, ppucDer);
		
		ret = 0;
		
	}while(0);
	
	RSA_free(pRSA);
	EVP_PKEY_free(pKey);
	PKCS8_PRIV_KEY_INFO_free(p8);
	
	return ret;
}

// 获得内存中公钥的PKCS8编码字符串
// 调用者需要释放ppucDer变量的内存
int lbxx_pkcs8_i2d_rsa_memory_pubkey(unsigned char *pucPubkey, unsigned int uiKeylen, unsigned char **ppucDer, unsigned int *puiLen)
{
	int ret = -1;
	RSA *pRSA = NULL;
	EVP_PKEY *pKey = NULL;
	PKCS8_PRIV_KEY_INFO *p8 = NULL;
	
	do{
		/* 初始化EVP */
		pKey = EVP_PKEY_new();
		if (!pKey) {
			return -1;
		}
		/* 设置EVP算法类型 */
		EVP_PKEY_set_type(pKey, EVP_PKEY_RSA);
		
		const unsigned char *pp = pucPubkey;
		pRSA = d2i_RSAPublicKey(NULL, &pp, uiKeylen);
		if(!pRSA) {
			break;
		}
		if (!EVP_PKEY_set1_RSA(pKey, pRSA)) {
			break;
		}
		/* EVP_PKEY转为PKCS8 */
		*puiLen = i2d_PUBKEY(pKey, ppucDer);
		
		ret = 0;
		
	}while(0);
	
	RSA_free(pRSA);
	EVP_PKEY_free(pKey);
	PKCS8_PRIV_KEY_INFO_free(p8);
	
	return ret;
}

// 从PKCS8编码中获得私钥
int lbxx_pkcs8_d2i_rsa_prikey(unsigned char *pucDer, unsigned int puiLen, unsigned char *pucPrikey, unsigned int *uiKeylen)
{
	EVP_PKEY *pKey = NULL;
	unsigned char *buf = NULL;
	unsigned int len = 0;
	
	pKey = d2i_AutoPrivateKey(NULL, (const unsigned char **)&pucDer, puiLen);
	if(!pKey) {
		return 1;
	}
	if (EVP_PKEY_id(pKey) != EVP_PKEY_RSA){
		return 1;
	}
	
	len = i2d_RSAPrivateKey(EVP_PKEY_get0(pKey), &buf);
	
	if(*uiKeylen < len) {
		return 1;
	}
	memcpy(pucPrikey, buf, len);
	*uiKeylen = len;
	
	return 0;
}

// 从PKCS8编码中获得公钥
int lbxx_pkcs8_d2i_rsa_pubkey(unsigned char *pucDer, unsigned int puiLen, unsigned char *pucPubkey, unsigned int *uiKeylen)
{
	int len = 0;
	unsigned char *buf = NULL;
	EVP_PKEY *pKey = NULL;
	
	pKey = d2i_PUBKEY(NULL, (const unsigned char **)&pucDer, puiLen);
	if(!pKey) {
		return 1;
	}
	len = i2d_RSAPublicKey(EVP_PKEY_get0(pKey), &buf);
	if(*uiKeylen < len) {
		return 1;
	}
	memcpy(pucPubkey, buf, len);
	*uiKeylen = len;
	
	return 0;
}

// 获得新密钥私钥的PKCS8编码字符串
// 调用者需要释放ppucDer变量的内存
int lbxx_pkcs8_i2d_rsa_generate_prikey(unsigned char **ppucDer, unsigned int *puiLen)
{
	int ret = -1;
	EVP_PKEY *pKey = NULL;
	EVP_PKEY_CTX *pkey_ctx = NULL;
	PKCS8_PRIV_KEY_INFO *p8 = NULL;

	do{
		/* 初始化EVP */
		pKey = EVP_PKEY_new();
		if (!pKey) {
			return -1;
		}
		/* 设置EVP算法类型 */
		EVP_PKEY_set_type(pKey, EVP_PKEY_RSA);

		/* 初始化EVP_CTX,内部包含EVP内容 */
		pkey_ctx = EVP_PKEY_CTX_new(pKey, NULL);
		if (!pkey_ctx) {
			break;
		}
		
		/* EVP调用时,必须执行init函数,为了设置操作类型 */
		if (EVP_PKEY_keygen_init(pkey_ctx) <= 0){
			EVP_PKEY_free(pKey);
			EVP_PKEY_CTX_free(pkey_ctx);
			return -1;
		}
		/* 设置密钥模长 */
		EVP_PKEY_CTX_set_rsa_keygen_bits(pkey_ctx, 1024);

		if (EVP_PKEY_keygen(pkey_ctx, &pKey) <= 0) {
			EVP_PKEY_free(pKey);
			EVP_PKEY_CTX_free(pkey_ctx);
			return -1;
		}

		/* 检查密钥对是否合法 */
		if (EVP_PKEY_check(pkey_ctx) <= 0){
			EVP_PKEY_free(pKey);
			EVP_PKEY_CTX_free(pkey_ctx);
		}

		/* EVP_PKEY转为PKCS8 */
		p8 = EVP_PKEY2PKCS8(pKey);
		if (!p8) {
			break;
		}
		*puiLen = i2d_PKCS8_PRIV_KEY_INFO(p8, ppucDer);
		
		ret = 0;
		
	}while(0);
	
	EVP_PKEY_free(pKey);
	EVP_PKEY_CTX_free(pkey_ctx);
	PKCS8_PRIV_KEY_INFO_free(p8);

	return ret;
}

// 获得新密钥公钥的PKCS8编码字符串
// 调用者需要释放ppucDer变量的内存
int lbxx_pkcs8_i2d_rsa_generate_pubkey(unsigned char **ppucDer, unsigned int *puiLen)
{
	int ret = -1;
	RSA *pRSA = NULL;
	EVP_PKEY *pKey = NULL;
	EVP_PKEY_CTX *pkey_ctx = NULL;
	const unsigned char *kptr = NULL;

	do{
		/* 初始化EVP */
		pKey = EVP_PKEY_new();
		if (!pKey) {
			break;
		}
		/* 设置EVP算法类型 */
		EVP_PKEY_set_type(pKey, EVP_PKEY_RSA);

		/* 初始化EVP_CTX,内部包含EVP内容 */
		pkey_ctx = EVP_PKEY_CTX_new(pKey, NULL);
		if (!pkey_ctx) {
			break;
		}
		
		/* 从内存中设置密钥对 */
		kptr = kPrikey;
		pRSA = d2i_RSAPrivateKey(NULL, &kptr, sizeof(kPrikey));
		if (pRSA == NULL) {
			break;
		}
		if (!EVP_PKEY_set1_RSA(pKey, pRSA)) {
			break;
		}
		
		/* 检查密钥对是否合法 */
		if (EVP_PKEY_check(pkey_ctx) <= 0){
			break;
		}

		/* EVP_PKEY转为PKCS8 */
		*puiLen = i2d_PUBKEY(pKey, ppucDer);
		
		ret = 0;
		
	}while(0);
	
	EVP_PKEY_free(pKey);
	EVP_PKEY_CTX_free(pkey_ctx);

	return ret;
}

int main(int argc, char *argv[])
{
	int ret = 0;
	// 必须为NULL
	unsigned char *pucDer = NULL;
	unsigned int uiDerlen = 0;
	unsigned char buf[2048] = { 0 };
	unsigned int len = sizeof(buf);
	
	ret = lbxx_pkcs8_i2d_rsa_generate_prikey(&pucDer, &uiDerlen);
	if(ret != 0) {
		printf("call lbxx_pkcs8_i2d_rsa_generate_prikey() error\n");
		return 1;
	}
	OPENSSL_free(pucDer);
	pucDer = NULL;
	
	ret = lbxx_pkcs8_i2d_rsa_generate_pubkey(&pucDer, &uiDerlen);
	if(ret != 0) {
		printf("call lbxx_pkcs8_i2d_rsa_generate_pubkey() error\n");
		return 1;
	}
	OPENSSL_free(pucDer);
	pucDer = NULL;
	
	ret = lbxx_pkcs8_i2d_rsa_memory_prikey(kPrikey, sizeof(kPrikey), &pucDer, &uiDerlen);
	if(ret != 0) {
		printf("call lbxx_pkcs8_i2d_rsa_memory_prikey() error\n");
		return 1;
	}
	ret = lbxx_pkcs8_d2i_rsa_prikey(pucDer, uiDerlen, buf, &len);
	if(ret != 0) {
		printf("call lbxx_pkcs8_d2i_rsa_prikey() error\n");
		return 1;
	}
	if(sizeof(kPrikey) != len || memcmp(kPrikey, buf, len) != 0) {
		printf("rsa pkcs8 private key encode or decode error!!!!\n");
		return 1;
	}
	OPENSSL_free(pucDer);
	pucDer = NULL;
	
	memset(buf, 0x00, sizeof(buf));
	len = sizeof(buf);
	ret = lbxx_pkcs8_i2d_rsa_memory_pubkey(kPubkey, sizeof(kPubkey), &pucDer, &uiDerlen);
	if(ret != 0) {
		printf("call lbxx_pkcs8_i2d_rsa_memory_pubkey() error\n");
		return 1;
	}
	ret = lbxx_pkcs8_d2i_rsa_pubkey(pucDer, uiDerlen, buf, &len);
	if(ret != 0) {
		printf("call lbxx_pkcs8_d2i_rsa_pubkey() error\n");
		return 1;
	}
	if(sizeof(kPubkey) != len || memcmp(kPubkey, buf, len) != 0) {
		printf("rsa pkcs8 public key encode or decode error!!!!\n");
		return 1;
	}
	OPENSSL_free(pucDer);
	pucDer = NULL;
	
	printf("rsa pkcs8 test success!!!\n");
	return 0;
}

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