【实用小技巧】RSA非对称加解密及XML&PEM格式互换方案
最近因考虑接口安全问题，有实现给WEB API实现统一的参数鉴权功能，以防止请求参数被篡改或重复执行，参数鉴权方法基本与常见的鉴权思路相同，采用（timestamp+sign），而我为了防止timestamp被更改，sign算法（timestamp+相关参数排序、格式化后拼接再MD5）也因为在前端是不安全的，故对timestamp采取使用非对称加解密，以尽可能的保证生成的sign不易被破解或替换；
RSA加解密（即：非对称加解密）
生成公钥、私钥对方法（C#），生成出来后默认都是XML格式：
public static Tuple<string, string> GeneratePublicAndPrivateKeyPair()
{
using (RSACryptoServiceProvider rsa = new RSACryptoServiceProvider())
{
string publicKey = rsa.ToXmlString(false); // 公钥
string privateKey = rsa.ToXmlString(true); // 私钥
return Tuple.Create(publicKey, privateKey);
}
}
使用公钥加密：（支持分段加密，普通单次加密可能会因为内容过长而报错）
public static string RSAEncrypt(string publicKey, string rawInput)
{
if (string.IsNullOrEmpty(rawInput))
{
return string.Empty;
}
if (string.IsNullOrWhiteSpace(publicKey))
{
throw new ArgumentException("Invalid Public Key");
}
using (var rsaProvider = new RSACryptoServiceProvider())
{
var inputBytes = Encoding.UTF8.GetBytes(rawInput);//有含义的字符串转化为字节流
rsaProvider.FromXmlString(publicKey);//载入公钥
int bufferSize = (rsaProvider.KeySize / 8) - 11;//单块最大长度
var buffer = new byte[bufferSize];
using (MemoryStream inputStream = new MemoryStream(inputBytes),
outputStream = new MemoryStream())
{
while (true)
{ //分段加密
int readSize = inputStream.Read(buffer, 0, bufferSize);
if (readSize <= 0)
{
break;
}
var temp = new byte[readSize];
Array.Copy(buffer, 0, temp, 0, readSize);
var encryptedBytes = rsaProvider.Encrypt(temp, false);
outputStream.Write(encryptedBytes, 0, encryptedBytes.Length);
}
return Convert.ToBase64String(outputStream.ToArray());//转化为字节流方便传输
}
}
}
使用私钥解密：（支持分段解密，普通单次解密可能会因为密文过长而报错）
public static string RSADecrypt(string privateKey,string encryptedInput)
{
if (string.IsNullOrEmpty(encryptedInput))
{
return string.Empty;
}
if (string.IsNullOrWhiteSpace(privateKey))
{
throw new ArgumentException("Invalid Private Key");
}
using (var rsaProvider = new RSACryptoServiceProvider())
{
var inputBytes = Convert.FromBase64String(encryptedInput);
rsaProvider.FromXmlString(privateKey);
int bufferSize = rsaProvider.KeySize / 8;
var buffer = new byte[bufferSize];
using (MemoryStream inputStream = new MemoryStream(inputBytes),
outputStream = new MemoryStream())
{
while (true)
{
int readSize = inputStream.Read(buffer, 0, bufferSize);
if (readSize <= 0)
{
break;
}
var temp = new byte[readSize];
Array.Copy(buffer, 0, temp, 0, readSize);
var rawBytes = rsaProvider.Decrypt(temp, false);
outputStream.Write(rawBytes, 0, rawBytes.Length);
}
return Encoding.UTF8.GetString(outputStream.ToArray());
}
}
}
如果都是C#项目可能如上两个方法就可以了，但如果需要与WEB前端、JAVA等其它编程语言协同交互处理时（比如：WEB前端用公钥加密，后端C#私钥解密），则可能因为公钥与私钥的格式不相同而导致无法正常的进行对接【前端、JAVA 等语言使用的是PEM格式的，而C#使用的是XML格式】，网上查XML转PEM格式方案时，都是复制自：https://www.cnblogs.com/micenote/p/7862989.html 这篇文章，但其实这篇文章也只是写了私钥XML转PEM格式，并没有说明公钥XML如何转PEM格式，而且只写了支持从文件中获取内容再转换，方案不全，但是给了我（梦在旅途，http://www.zuowenjun.cn or zuowj.cnblogs.com.cn）思路，我经过各种验证，最终实现了比较友好的PEM与XML格式的相互转换方式,且经过单元测试验证通过，在此分享给大家。
如下是完整的XML与PEM格式转换器类代码；（注意需引入BouncyCastle nuget包）
using Org.BouncyCastle.Crypto;
using Org.BouncyCastle.Crypto.Parameters;
using Org.BouncyCastle.Math;
using System;
using System.Collections.Generic;
using System.IO;
using System.Linq;
using System.Security.Cryptography;
using System.Text;
using System.Threading.Tasks;
namespace Zuowj.Common
{
/// <summary>
/// RSA公钥、私钥对格式（XML与PEM）转换器
/// author:zuowenjun
/// date:2020-12-29
/// </summary>
public static class RsaKeysFormatConverter
{
/// <summary>
/// XML公钥转成Pem公钥
/// </summary>
/// <param name="xmlPublicKey"></param>
/// <returns></returns>
public static string XmlPublicKeyToPem(string xmlPublicKey)
{
RSAParameters rsaParam;
using (RSACryptoServiceProvider rsa = new RSACryptoServiceProvider())
{
rsa.FromXmlString(xmlPublicKey);
rsaParam = rsa.ExportParameters(false);
}
RsaKeyParameters param = new RsaKeyParameters(false, new BigInteger(1, rsaParam.Modulus), new BigInteger(1, rsaParam.Exponent));
string pemPublicKeyStr = null;
using (var ms = new MemoryStream())
{
using (var sw = new StreamWriter(ms))
{
var pemWriter = new Org.BouncyCastle.OpenSsl.PemWriter(sw);
pemWriter.WriteObject(param);
sw.Flush();
byte[] buffer = new byte[ms.Length];
ms.Position = 0;
ms.Read(buffer, 0, (int)ms.Length);
pemPublicKeyStr = Encoding.UTF8.GetString(buffer);
}
}
return pemPublicKeyStr;
}
/// <summary>
/// Pem公钥转成XML公钥
/// </summary>
/// <param name="pemPublicKeyStr"></param>
/// <returns></returns>
public static string PemPublicKeyToXml(string pemPublicKeyStr)
{
RsaKeyParameters pemPublicKey;
using (var ms = new MemoryStream(Encoding.UTF8.GetBytes(pemPublicKeyStr)))
{
using (var sr = new StreamReader(ms))
{
var pemReader = new Org.BouncyCastle.OpenSsl.PemReader(sr);
pemPublicKey = (RsaKeyParameters)pemReader.ReadObject();
}
}
var p = new RSAParameters
{
Modulus = pemPublicKey.Modulus.ToByteArrayUnsigned(),
Exponent = pemPublicKey.Exponent.ToByteArrayUnsigned()
};
string xmlPublicKeyStr;
using (var rsa = new RSACryptoServiceProvider())
{
rsa.ImportParameters(p);
xmlPublicKeyStr = rsa.ToXmlString(false);
}
return xmlPublicKeyStr;
}
/// <summary>
/// XML私钥转成PEM私钥
/// </summary>
/// <param name="xmlPrivateKey"></param>
/// <returns></returns>
public static string XmlPrivateKeyToPem(string xmlPrivateKey)
{
RSAParameters rsaParam;
using (RSACryptoServiceProvider rsa = new RSACryptoServiceProvider())
{
rsa.FromXmlString(xmlPrivateKey);
rsaParam = rsa.ExportParameters(true);
}
var param = new RsaPrivateCrtKeyParameters(
new BigInteger(1, rsaParam.Modulus), new BigInteger(1, rsaParam.Exponent), new BigInteger(1, rsaParam.D),
new BigInteger(1, rsaParam.P), new BigInteger(1, rsaParam.Q), new BigInteger(1, rsaParam.DP), new BigInteger(1, rsaParam.DQ),
new BigInteger(1, rsaParam.InverseQ));
string pemPrivateKeyStr = null;
using (var ms = new MemoryStream())
{
using (var sw = new StreamWriter(ms))
{
var pemWriter = new Org.BouncyCastle.OpenSsl.PemWriter(sw);
pemWriter.WriteObject(param);
sw.Flush();
byte[] buffer = new byte[ms.Length];
ms.Position = 0;
ms.Read(buffer, 0, (int)ms.Length);
pemPrivateKeyStr = Encoding.UTF8.GetString(buffer);
}
}
return pemPrivateKeyStr;
}
/// <summary>
/// Pem私钥转成XML私钥
/// </summary>
/// <param name="pemPrivateKeyStr"></param>
/// <returns></returns>
public static string PemPrivateKeyToXml(string pemPrivateKeyStr)
{
RsaPrivateCrtKeyParameters pemPrivateKey;
using (var ms = new MemoryStream(Encoding.UTF8.GetBytes(pemPrivateKeyStr)))
{
using (var sr = new StreamReader(ms))
{
var pemReader = new Org.BouncyCastle.OpenSsl.PemReader(sr);
var keyPair = (AsymmetricCipherKeyPair)pemReader.ReadObject();
pemPrivateKey = (RsaPrivateCrtKeyParameters)keyPair.Private;
}
}
var p = new RSAParameters
{
Modulus = pemPrivateKey.Modulus.ToByteArrayUnsigned(),
Exponent = pemPrivateKey.PublicExponent.ToByteArrayUnsigned(),
D = pemPrivateKey.Exponent.ToByteArrayUnsigned(),
P = pemPrivateKey.P.ToByteArrayUnsigned(),
Q = pemPrivateKey.Q.ToByteArrayUnsigned(),
DP = pemPrivateKey.DP.ToByteArrayUnsigned(),
DQ = pemPrivateKey.DQ.ToByteArrayUnsigned(),
InverseQ = pemPrivateKey.QInv.ToByteArrayUnsigned(),
};
string xmlPrivateKeyStr;
using (var rsa = new RSACryptoServiceProvider())
{
rsa.ImportParameters(p);
xmlPrivateKeyStr = rsa.ToXmlString(true);
}
return xmlPrivateKeyStr;
}
}
}
如下是单元测试代码：
//公钥（XML、PEM格式互）测试
string srcPublicKey = “具体的XML Public Key”;
string pemPublicKeyStr= RsaKeysFormatConverter.XmlPublicKeyToPem(publicKey);
string xmlPublicKeyStr= RsaKeysFormatConverter.PemPublicKeyToXml(pemPublicKeyStr);
Assert.AreEqual(srcPublicKey, xmlPublicKeyStr);
//私钥（XML、PEM格式互）测试
string srcPrivateKey = “具体的XML Private Key”;
string pemPrivateKeyStr = RsaKeysFormatConverter.XmlPrivateKeyToPem(srcPrivateKey);
string xmlPrivateKeyStr = RsaKeysFormatConverter.PemPrivateKeyToXml(pemPrivateKeyStr);
Assert.AreEqual(privateKey,xmlPrivateKeyStr)
当然也可以不用这么费劲自己实现格式转换，可以使用在线网站直接转换：https://the-x.cn/certificate/XmlToPem.aspx ，另外也有一篇文章实现了类似的功能，但生成的PEM格式并非完整的格式，缺少注释头尾：https://www.cnblogs.com/datous/p/RSAKeyConvert.html
