同时兼容JS和C#的RSA加密解密算法详解（对web提交的数据加密传输）

前言

我们在Web应用中往往涉及到敏感的数据，由于HTTP协议以明文的形式与服务器进行交互，因此可以通过截获请求的数据包进行分析来盗取有用的信息。虽然https可以对传输的数据进行加密，但是必须要申请证书（一般都是收费的），成本较高。那么问题来了，如果对web提交的敏感数据进行加密呢？web应用中，前端的数据处理和交互基本上都是靠javascript来完成，后台的逻辑处理可以C#(java)等进行处理。

微软的C#中虽然有RSA算法，但是格式和OpenSSL生成的公钥/私钥文件格式并不兼容。这个也给贯通前后台的RSA加密解密带来了难度。为了兼容OpenSSL生成的公钥/私钥文件格式，贯通javascript和C#的RSA加密解密算法，必须对C#内置的方法进行再度封装。

下面以登录为例，用户在密码框输入密码后，javascript发送ajax请求时，对密码先进行rsa加密后再发送，服务器接收到加密后的密码后，先对其进行解密， 然后再验证登录是否成功。

1、为了进行RSA加密解密，首先需要用openssl生成一对公钥和私钥（没有的先下载openssl)：

1） 打开openssl.exe文件，输入 genrsa -out openssl_rsa_priv.pem 1024

此命令在openssl.exe同目录下生成openssl_rsa_private_key.pem文件。

2） 生成公钥 rsa  -in openssl_rsa__private.pem -pubout -out openssl_rsa__public.pem

以上命令会创建如下的文件：

这个文件可以用文本编辑器进行打开，查看内容。

-----BEGIN PUBLIC KEY-----
MIGfMA0GCSqGSIb3DQEBAQUAA4GNADCBiQKBgQC0w036ClSD0LvxPROMun0u022R
OJlZE6P3m+gjq3gpi4n7lo8jhTqMqgccDbVJqnIfMzWS9O3lnlQXWTxJ3B4XJ52F
AcriY5brOXUVgBLx5QMHLLd1gtJnmG4i7r4ytgX7XVKRnojR6zca1YnS0lbGGDF1
CGllB1riNrdksSQP+wIDAQAB
-----END PUBLIC KEY-----

-----BEGIN RSA PRIVATE KEY-----
MIICXQIBAAKBgQC0w036ClSD0LvxPROMun0u022ROJlZE6P3m+gjq3gpi4n7lo8j
hTqMqgccDbVJqnIfMzWS9O3lnlQXWTxJ3B4XJ52FAcriY5brOXUVgBLx5QMHLLd1
gtJnmG4i7r4ytgX7XVKRnojR6zca1YnS0lbGGDF1CGllB1riNrdksSQP+wIDAQAB
AoGAIOyl6lIxXKULZoBKbEqXfIz0GwxlGg1ywyn5mW2lAGQzKMken0ioBnD9xIVW
rOlHyhkIvBCyuC0jgfE2Avn93MlB3j0WRuXMFlJpCBlEklMilO9Zgmwl+vTB3VZb
8VzdrEEEUBio7LWP/KvSo+IFlNjDTKgAczbLTwAmj4w6g0ECQQDm4yxPdxcU2ywZ
7PyjIMM9qnSah9KcrjU8gjEyHsUpgTjhw1cx7Peo+vRiHqxDy1yaSu1BlwRR52pC
jKNnl0QhAkEAyGx3NxEIiLk2oXGGbIMZ4P6geC8gYu01BiRNWVf0Yi7+sCH68eUP
oI+G5bJ8bvzXpvHjQi0s2OlRfct/qtPQmwJBALa+2DONbxdy4lUi3lO/esk0QVaO
aoTY3gomggnJkQRo4zzOABXkGaIF/6gp3u9J5uG4rFFd1m19XP2Pk0ZK1AECQBYi
lJAKW4zuF7CA3z3AxOzqckKTwdnrJL4G6FwDsMPfONWvCw4IJE+xSk64BbIkTpTr
hhPa9WcHba6c+P6e4h0CQQDWeGMMpkqPG/w4afNCGmvRnM8vNkGUAmDGvCsfkTID
ijpKl5SD55hPHsWE5rsv1TLUpkWtrFBcg61bHwMUP3cv
-----END RSA PRIVATE KEY-----

2、用jsencrypt对密码进行加密：

首先需要导入js包文件

<script src="dist/js/jsencrypt.js"></script>

var encrypt = new JSEncrypt();
var pubkey = "-----BEGIN PUBLIC KEY----- \
 MIGfMA0GCSqGSIb3DQEBAQUAA4GNADCBiQKBgQDAj0dPnBMf3Z4VT1B8Ee6bjKNs \
 hlYj7xvGijAa8RCdmGR7mrtrExnk8mdUlwdcS05gc4SSFOyWJcYtKUHpWn8/pkS0 \
 vgGOl9Bzn0Xt9hiqTb3pZAfykNrMDGZMgJgfD6KTnfzVUAOupvxjcGkcoj6/vV5I \
 eMcx8mT/z3elfsDSjQIDAQAB \
 -----END PUBLIC KEY-----";
encrypt.setPublicKey(pubkey);
var encrypted = encrypt.encrypt($('#txtpwd').val());
//console.log(encrypted);
$.ajax({
 type: "POST",
 url: "http://localhost:24830/services/rsa_pem.ashx",
 data: { "pwd": encrypted },
 dataType: "Json",
 error: function (xhr, status, error) {
  // alert(error);
  $("#txtInfo").text(' 请求服务器失败！');
  $(that).text('登 录');
  $(that).attr('disabled', false);
 },
 success: function (json) {

 if (uid == "admin" && json.data=="000") {
  window.location.href = "index.html";
 }
 else {
  $("#txtInfo").text(' 用户名或者密码错误！');
  $(that).text('登 录');
  $(that).attr('disabled', false);
 }
 }
});

3、后台用C#进行解密

using System;
using System.Collections.Generic;
using System.IO;
using System.Linq;
using System.Security.Cryptography;
using System.Text;
using System.Threading.Tasks;

namespace CMCloud.SaaS
{
 public class RSACryptoService
 {
 private RSACryptoServiceProvider _privateKeyRsaProvider;
 private RSACryptoServiceProvider _publicKeyRsaProvider;

 /// <summary>
 /// RSA解密
 /// </summary>
 /// <param name="cipherText"></param>
 /// <returns></returns>
 public string Decrypt(string cipherText)
 {
  if (_privateKeyRsaProvider == null)
  {
  throw new Exception("_privateKeyRsaProvider is null");
  }
  return Decrypt2(cipherText);
 }
 /// <summary>
 /// RSA加密
 /// </summary>
 /// <param name="text"></param>
 /// <returns></returns>
 public string Encrypt(string text)
 {
  if (_publicKeyRsaProvider == null)
  {
  throw new Exception("_publicKeyRsaProvider is null");
  }
  return Encrypt2(text);
  //return Convert.ToBase64String(_publicKeyRsaProvider.Encrypt(Encoding.UTF8.GetBytes(text), false));

 }
 private string Encrypt2(string text)
 {

  Byte[] PlaintextData = Encoding.UTF8.GetBytes(text);
  int MaxBlockSize = _publicKeyRsaProvider.KeySize / 8 - 11;//加密块最大长度限制

  if (PlaintextData.Length <= MaxBlockSize)
  {
  return Convert.ToBase64String(_publicKeyRsaProvider.Encrypt(PlaintextData, false));
  }
  else
  {
  using (MemoryStream PlaiStream = new MemoryStream(PlaintextData))
  using (MemoryStream CrypStream = new MemoryStream())
  {
   Byte[] Buffer = new Byte[MaxBlockSize];
   int BlockSize = PlaiStream.Read(Buffer, 0, MaxBlockSize);

   while (BlockSize > 0)
   {
   Byte[] ToEncrypt = new Byte[BlockSize];
   Array.Copy(Buffer, 0, ToEncrypt, 0, BlockSize);

   Byte[] Cryptograph = _publicKeyRsaProvider.Encrypt(ToEncrypt, false);
   CrypStream.Write(Cryptograph, 0, Cryptograph.Length);

   BlockSize = PlaiStream.Read(Buffer, 0, MaxBlockSize);
   }

   return Convert.ToBase64String(CrypStream.ToArray(), Base64FormattingOptions.None);
  }
  }

 }

 private string Decrypt2(string ciphertext)
 {

  Byte[] CiphertextData = Convert.FromBase64String(ciphertext);
  int MaxBlockSize = _privateKeyRsaProvider.KeySize / 8; //解密块最大长度限制

  if (CiphertextData.Length <= MaxBlockSize)
  return System.Text.Encoding.UTF8.GetString(_privateKeyRsaProvider.Decrypt(CiphertextData, false));

  using (MemoryStream CrypStream = new MemoryStream(CiphertextData))
  using (MemoryStream PlaiStream = new MemoryStream())
  {
  Byte[] Buffer = new Byte[MaxBlockSize];
  int BlockSize = CrypStream.Read(Buffer, 0, MaxBlockSize);

  while (BlockSize > 0)
  {
   Byte[] ToDecrypt = new Byte[BlockSize];
   Array.Copy(Buffer, 0, ToDecrypt, 0, BlockSize);

   Byte[] Plaintext = _privateKeyRsaProvider.Decrypt(ToDecrypt, false);
   PlaiStream.Write(Plaintext, 0, Plaintext.Length);

   BlockSize = CrypStream.Read(Buffer, 0, MaxBlockSize);
  }

  return System.Text.Encoding.UTF8.GetString(PlaiStream.ToArray());
  }
 }
 public RSACryptoService(string privateKey, string publicKey = null)
 {
  if (!string.IsNullOrEmpty(privateKey))
  {
  _privateKeyRsaProvider = CreateRsaProviderFromPrivateKey(privateKey);
  }

  if (!string.IsNullOrEmpty(publicKey))
  {
  _publicKeyRsaProvider = CreateRsaProviderFromPublicKey(publicKey);
  }
 }

 private RSACryptoServiceProvider CreateRsaProviderFromPrivateKey(string privateKey)
 {
  var privateKeyBits = System.Convert.FromBase64String(privateKey);

  var RSA = new RSACryptoServiceProvider();
  var RSAparams = new RSAParameters();

  using (BinaryReader binr = new BinaryReader(new MemoryStream(privateKeyBits)))
  {
  byte bt = 0;
  ushort twobytes = 0;
  twobytes = binr.ReadUInt16();
  if (twobytes == 0x8130)
   binr.ReadByte();
  else if (twobytes == 0x8230)
   binr.ReadInt16();
  else
   throw new Exception("Unexpected value read binr.ReadUInt16()");

  twobytes = binr.ReadUInt16();
  if (twobytes != 0x0102)
   throw new Exception("Unexpected version");

  bt = binr.ReadByte();
  if (bt != 0x00)
   throw new Exception("Unexpected value read binr.ReadByte()");

  RSAparams.Modulus = binr.ReadBytes(GetIntegerSize(binr));
  RSAparams.Exponent = binr.ReadBytes(GetIntegerSize(binr));
  RSAparams.D = binr.ReadBytes(GetIntegerSize(binr));
  RSAparams.P = binr.ReadBytes(GetIntegerSize(binr));
  RSAparams.Q = binr.ReadBytes(GetIntegerSize(binr));
  RSAparams.DP = binr.ReadBytes(GetIntegerSize(binr));
  RSAparams.DQ = binr.ReadBytes(GetIntegerSize(binr));
  RSAparams.InverseQ = binr.ReadBytes(GetIntegerSize(binr));
  }

  RSA.ImportParameters(RSAparams);
  return RSA;
 }

 private int GetIntegerSize(BinaryReader binr)
 {
  byte bt = 0;
  byte lowbyte = 0x00;
  byte highbyte = 0x00;
  int count = 0;
  bt = binr.ReadByte();
  if (bt != 0x02)
  return 0;
  bt = binr.ReadByte();

  if (bt == 0x81)
  count = binr.ReadByte();
  else
  if (bt == 0x82)
  {
  highbyte = binr.ReadByte();
  lowbyte = binr.ReadByte();
  byte[] modint = { lowbyte, highbyte, 0x00, 0x00 };
  count = BitConverter.ToInt32(modint, 0);
  }
  else
  {
  count = bt;
  }

  while (binr.ReadByte() == 0x00)
  {
  count -= 1;
  }
  binr.BaseStream.Seek(-1, SeekOrigin.Current);
  return count;
 }

 private RSACryptoServiceProvider CreateRsaProviderFromPublicKey(string publicKeyString)
 {
  // encoded OID sequence for PKCS #1 rsaEncryption szOID_RSA_RSA = "1.2.840.113549.1.1.1"
  byte[] SeqOID = { 0x30, 0x0D, 0x06, 0x09, 0x2A, 0x86, 0x48, 0x86, 0xF7, 0x0D, 0x01, 0x01, 0x01, 0x05, 0x00 };
  byte[] x509key;
  byte[] seq = new byte[15];
  int x509size;

  x509key = Convert.FromBase64String(publicKeyString);
  x509size = x509key.Length;

  // --------- Set up stream to read the asn.1 encoded SubjectPublicKeyInfo blob ------
  using (MemoryStream mem = new MemoryStream(x509key))
  {
  using (BinaryReader binr = new BinaryReader(mem)) //wrap Memory Stream with BinaryReader for easy reading
  {
   byte bt = 0;
   ushort twobytes = 0;

   twobytes = binr.ReadUInt16();
   if (twobytes == 0x8130) //data read as little endian order (actual data order for Sequence is 30 81)
   binr.ReadByte(); //advance 1 byte
   else if (twobytes == 0x8230)
   binr.ReadInt16(); //advance 2 bytes
   else
   return null;

   seq = binr.ReadBytes(15); //read the Sequence OID
   if (!CompareBytearrays(seq, SeqOID)) //make sure Sequence for OID is correct
   return null;

   twobytes = binr.ReadUInt16();
   if (twobytes == 0x8103) //data read as little endian order (actual data order for Bit String is 03 81)
   binr.ReadByte(); //advance 1 byte
   else if (twobytes == 0x8203)
   binr.ReadInt16(); //advance 2 bytes
   else
   return null;

   bt = binr.ReadByte();
   if (bt != 0x00) //expect null byte next
   return null;

   twobytes = binr.ReadUInt16();
   if (twobytes == 0x8130) //data read as little endian order (actual data order for Sequence is 30 81)
   binr.ReadByte(); //advance 1 byte
   else if (twobytes == 0x8230)
   binr.ReadInt16(); //advance 2 bytes
   else
   return null;

   twobytes = binr.ReadUInt16();
   byte lowbyte = 0x00;
   byte highbyte = 0x00;

   if (twobytes == 0x8102) //data read as little endian order (actual data order for Integer is 02 81)
   lowbyte = binr.ReadByte(); // read next bytes which is bytes in modulus
   else if (twobytes == 0x8202)
   {
   highbyte = binr.ReadByte(); //advance 2 bytes
   lowbyte = binr.ReadByte();
   }
   else
   return null;
   byte[] modint = { lowbyte, highbyte, 0x00, 0x00 }; //reverse byte order since asn.1 key uses big endian order
   int modsize = BitConverter.ToInt32(modint, 0);

   int firstbyte = binr.PeekChar();
   if (firstbyte == 0x00)
   { //if first byte (highest order) of modulus is zero, don't include it
   binr.ReadByte(); //skip this null byte
   modsize -= 1; //reduce modulus buffer size by 1
   }

   byte[] modulus = binr.ReadBytes(modsize); //read the modulus bytes

   if (binr.ReadByte() != 0x02)  //expect an Integer for the exponent data
   return null;
   int expbytes = (int)binr.ReadByte(); // should only need one byte for actual exponent data (for all useful values)
   byte[] exponent = binr.ReadBytes(expbytes);

   // ------- create RSACryptoServiceProvider instance and initialize with public key -----
   RSACryptoServiceProvider RSA = new RSACryptoServiceProvider();
   RSAParameters RSAKeyInfo = new RSAParameters();
   RSAKeyInfo.Modulus = modulus;
   RSAKeyInfo.Exponent = exponent;
   RSA.ImportParameters(RSAKeyInfo);

   return RSA;
  }

  }
 }

 private bool CompareBytearrays(byte[] a, byte[] b)
 {
  if (a.Length != b.Length)
  return false;
  int i = 0;
  foreach (byte c in a)
  {
  if (c != b[i])
   return false;
  i++;
  }
  return true;
 }
 }
}

虽然将公钥暴露在js文件中，但是如果需要解密得到明文，必须需要私钥（这个存储在后台，不容易获取）。

调试运行，可以看到获取的密码是加密后的数据，然后在后台可以进行解密获取到明文。

总结

好了，大概就这样，以上就是这篇文章的全部内容了，希望本文的内容对大家的学习或者工作能带来一定的帮助，如果有疑问大家可以留言交流，谢谢大家对我们的支持