通过OpenSSL的接口实现Base64编解码

偏执的太偏执、 2023-02-15 12:48 257阅读 0赞

对openssl genrsa产生的rsa私钥pem文件，使用普通的base64解码会有问题，如使用[https://blog.csdn.net/fengbingchun/article/details/85218653][https_blog.csdn.net_fengbingchun_article_details_85218653] 中介绍的方法，一是有可能不能从返回的结果中直接使用strlen来获得最终字符的大小，因为返回的结果中可能会有0x00；二是pem文件中会有换行符，每行的字节长度超过64个字节就会有换行，普通的base64解码中不会对换行符有处理。在OpenSSL中，默认情况下，base64行长度限制为64个字符。

先介绍下使用命令行openssl base64进行编解码：

(1).对” [https://blog.csdn.net/fengbingchun][https_blog.csdn.net_fengbingchun]”进行编解码，执行命令及结果如下：

![2020060515420344.png][]

(2).对长串进行编解码，如” [https://blog.csdn.net/fengbingchun][https_blog.csdn.net_fengbingchun] [https://github.com//fengbingchun][https_github.com_fengbingchun]”，执行命令及结果如下：编码长度超过64个字符长度，会进行换行，若不想换行，可增加使用”-A”选项

![20200605154226331.png][]

(3).对指定文件进行编解码：如文件1.txt，先进行编码生成2.txt，然后再对2.txt进行解码生成3.txt，执行命令及结果如下：

![20200605154307789.png][]

下面是通过调用openssl的相关接口组合成的base64编解码实现：由外部负责申请足够的空间用于存放结果，最后一个参数用于指明编解码中是否换行。

int openssl_base64_encode(const unsigned char* in, int inlen, char* out, int* outlen, bool newline)
    {
    	BIO* b64 = BIO_new(BIO_f_base64());
    	BIO* bmem = BIO_new(BIO_s_mem());
    	if (!b64 || !bmem) {
    		fprintf(stderr, "fail to BIO_new\n");
    		return -1;
    	}
    	b64 = BIO_push(b64, bmem);
    
    	if (!newline)
    		BIO_set_flags(b64, BIO_FLAGS_BASE64_NO_NL); // ignore newlines, write everything in one line
    
    	*outlen = BIO_write(b64, in, inlen);
    	if (*outlen <= 0 || *outlen != inlen) {
    		fprintf(stderr, "fail to BIO_write\n");
    		return -1;
    	}
    	BIO_flush(b64);
    
    	BUF_MEM* buf = nullptr;
    	BIO_get_mem_ptr(b64, &buf);
    	*outlen = buf->length;
    	memcpy(out, buf->data, *outlen);
    
    	BIO_free_all(b64);
    	return 0;
    }
    
    int openssl_base64_decode(const char* in, int inlen, unsigned char* out, int* outlen, bool newline)
    {
    	BIO* b64 = BIO_new(BIO_f_base64());
    	BIO* bmem = BIO_new_mem_buf(in, inlen);
    	if (!b64 || !bmem) {
    		fprintf(stderr, "fail to BIO_new\n");
    		return -1;
    	}
    	b64 = BIO_push(b64, bmem);
    
    	if (!newline)
    		BIO_set_flags(b64, BIO_FLAGS_BASE64_NO_NL); // ignore newlines, write everything in one line
    
    	*outlen = BIO_read(b64, out, inlen);
    	if (*outlen <= 0) {
    		fprintf(stderr, "fail to BIO_read\n");
    		return -1;
    	}
    
    	BIO_free_all(b64);
    	return 0;
    }

下面是通过编解码字符串的测试代码：

int test_openssl_base64_simple()
    {
    	const char* src = "https://blog.csdn.net/fengbingchun https://github.com//fengbingchun";
    	int inlen = strlen(src);
    	int outlen = (inlen + 2) / 3 * 4 + ((inlen + 2) / 3 * 4 + 63) / 64;
    	std::unique_ptr<char[]> out1(new char[outlen]);
    	bool newline = true;
    
    	int ret = openssl_base64_encode((const unsigned char*)src, inlen, out1.get(), &outlen, newline);
    	if (ret != 0) {
    		fprintf(stderr, "fail to openssl_base64_encode\n");
    		return -1;
    	}
    	fprintf(stdout, "encode result:\n");
    	std::for_each(out1.get(), out1.get() + outlen, [](char& c) { fprintf(stdout, "%c", c); });
    	fprintf(stdout, "\n");
    
    	std::unique_ptr<unsigned char[]> dst(new unsigned char[outlen]);
    	int outlen1 = 0;
    	ret = openssl_base64_decode(out1.get(), outlen, dst.get(), &outlen1, newline);
    	if (ret != 0) {
    		fprintf(stderr, "fail to openssl_base64_decode\n");
    		return -1;
    	}
    	fprintf(stdout, "decode result:\n");
    	std::for_each(dst.get(), dst.get() + outlen1, [](unsigned char& c) { fprintf(stdout, "%c", (char)c); });
    	fprintf(stdout, "\n");
    
    	dst[outlen1] = '\0';
    	if (strcmp(src, (const char*)dst.get()) == 0) {
    		fprintf(stdout, "test success\n");
    		return 0;
    	} else {
    		fprintf(stdout, "test fail\n");
    		return -1;
    	}
    }

执行结果如下图所示：

![20200605154638841.png][]

之前在[https://blog.csdn.net/fengbingchun/article/details/106546012][https_blog.csdn.net_fengbingchun_article_details_106546012]中使用OpenSSL的函数PEM\_read\_RSAPrivateKey直接对pem文件进行解析，下面测试代码是通过调用上面的base64解码函数实现的解析：

int test_openssl_base64_complex()
    {
    #ifdef _MSC_VER
    	const char* name = "E:/GitCode/OpenSSL_Test/testdata/rsa_private.pem";
    #else
    	const char* name = "testdata/rsa_private.pem";
    #endif
    	const char* begin = "-----BEGIN RSA PRIVATE KEY-----";
    	const char* end = "-----END RSA PRIVATE KEY-----";
    	
    	FILE *fp = fopen(name, "rb");
    	if (!fp) {
    		fprintf(stderr, "fail to open file: %s\n", name);
    		return -1;
    	}
    	fseek(fp, 0, SEEK_END);
    	long length = ftell(fp);
    	rewind(fp);
    	
    	std::unique_ptr<unsigned char[]> data(new unsigned char[length]);
    	fread(data.get(), 1, length, fp);
    	fclose(fp);
    	
    	const char* p1 = strstr((const char*)data.get(), begin);
    	if (!p1) {
    		fprintf(stderr, "it's not a pem file: %s\n", name);
    		return -1;
    	}
    	
    	const char* p2 = strstr((const char*)data.get(), end);
    	if (!p2) {
    		fprintf(stderr, "it's not a pem file: %s\n", name);
    		return -1;
    	}
    	
    	bool newline = true;
    	long length2 = p2 - p1;
    	std::unique_ptr<unsigned char[]> decoded(new unsigned char[length2]);
    	int outlen = 0;
    	int ret = openssl_base64_decode(p1 + strlen(begin) + 1, length2, decoded.get(), &outlen, newline); // + 一个换行符长度
    	
    	const unsigned char* p = decoded.get();
    	RSA_PRIVATE_KEY* key = d2i_RSA_PRIVATE_KEY(nullptr, &p, outlen);
    	if (!key) {
    		fprintf(stderr, "fail to d2i_RSA_PRIVATE_KEY\n");
    		return -1;
    	}
    	
    	print(key->version, "version");
    	print(key->n, "n");
    	print(key->e, "e");
    	print(key->d, "d");
    	print(key->p, "p");
    	print(key->q, "q");
    	print(key->exp1, "exp1");
    	print(key->exp2, "exp2");
    	print(key->coeff, "coeff");
    	
    	RSA_PRIVATE_KEY_free(key);
    	return 0;
    }

执行结果如下：与直接使用PEM\_read\_RSAPrivateKey得到的结果是一致的

![watermark_type_ZmFuZ3poZW5naGVpdGk_shadow_10_text_aHR0cHM6Ly9ibG9nLmNzZG4ubmV0L2ZlbmdiaW5nY2h1bg_size_16_color_FFFFFF_t_70][]

以上代码段的完整code见：[GitHub/OpenSSL\_Test][GitHub_OpenSSL_Test]

**GitHub**：[https://github.com/fengbingchun/OpenSSL\_Test][https_github.com_fengbingchun_OpenSSL_Test]

[https_blog.csdn.net_fengbingchun_article_details_85218653]: https://blog.csdn.net/fengbingchun/article/details/85218653
[https_blog.csdn.net_fengbingchun]: https://blog.csdn.net/fengbingchun
[2020060515420344.png]: https://img-blog.csdnimg.cn/2020060515420344.png
[https_github.com_fengbingchun]: https://github.com/fengbingchun
[20200605154226331.png]: https://img-blog.csdnimg.cn/20200605154226331.png
[20200605154307789.png]: https://img-blog.csdnimg.cn/20200605154307789.png
[20200605154638841.png]: https://img-blog.csdnimg.cn/20200605154638841.png
[https_blog.csdn.net_fengbingchun_article_details_106546012]: https://blog.csdn.net/fengbingchun/article/details/106546012
[watermark_type_ZmFuZ3poZW5naGVpdGk_shadow_10_text_aHR0cHM6Ly9ibG9nLmNzZG4ubmV0L2ZlbmdiaW5nY2h1bg_size_16_color_FFFFFF_t_70]: https://img-blog.csdnimg.cn/20200605155052214.png?x-oss-process=image/watermark,type_ZmFuZ3poZW5naGVpdGk,shadow_10,text_aHR0cHM6Ly9ibG9nLmNzZG4ubmV0L2ZlbmdiaW5nY2h1bg==,size_16,color_FFFFFF,t_70
[GitHub_OpenSSL_Test]: https://github.com/fengbingchun/OpenSSL_Test/blob/master/demo/OpenSSL_Test/funset_openssl.cpp
[https_github.com_fengbingchun_OpenSSL_Test]: https://github.com/fengbingchun/OpenSSL_Test