Web應用中往往涉及到敏感的資料，由于HTTP協定以明文的形式與伺服器進行互動，是以可以通過截獲請求的資料包進行分析來盜取有用的資訊。雖然https可以對傳輸的資料進行加密，但是必須要申請證書（一般都是收費的），成本較高。那麼問題來了，如果對web送出的敏感資料進行加密呢？web應用中，前端的資料處理和互動基本上都是靠javascript來完成，背景的邏輯處理可以C#(java)等進行處理。
微軟的C#中雖然有RSA算法，但是格式和OpenSSL生成的公鑰/私鑰檔案格式并不相容。這個也給貫通前背景的RSA加密解密帶來了難度。為了相容OpenSSL生成的公鑰/私鑰檔案格式，貫通javascript和C#的RSA加密解密算法，必須對C#内置的方法進行再度封裝。
下面以登入為例，使用者在密碼框輸入密碼後，javascript發送ajax請求時，對密碼先進行rsa加密後再發送，伺服器接收到加密後的密碼後，先對其進行解密， 然後再驗證登入是否成功。
1 為了進行RSA加密解密，首先需要用openssl生成一對公鑰和私鑰（沒有的先下載下傳openssl)：
1） 打開openssl.exe檔案，輸入
genrsa -out openssl_rsa_priv.pem 1024
此指令在openssl.exe同目錄下生成openssl_rsa_private_key.pem檔案。
2） 生成公鑰
rsa -in openssl_rsa__private.pem -pubout -out openssl_rsa__public.pem
-----BEGIN PUBLIC KEY-----
MIGfMA0GCSqGSIb3DQEBAQUAA4GNADCBiQKBgQC0w036ClSD0LvxPROMun0u022R
OJlZE6P3m+gjq3gpi4n7lo8jhTqMqgccDbVJqnIfMzWS9O3lnlQXWTxJ3B4XJ52F
AcriY5brOXUVgBLx5QMHLLd1gtJnmG4i7r4ytgX7XVKRnojR6zca1YnS0lbGGDF1
CGllB1riNrdksSQP+wIDAQAB
-----END PUBLIC KEY----- -----BEGIN RSA PRIVATE KEY-----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-----END RSA PRIVATE KEY----- 2 用jsencrypt對密碼進行加密：
首先需要導入js封包件:
<script src="dist/js/jsencrypt.js"></script> 然後編寫JS加密算法，示例如下:
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(' 請求伺服器失敗！');
$(that).text('登 錄');
$(that).attr('disabled', false);
},
success: function (json) {
if (uid == "admin" && json.data=="000") {
window.location.href = "index.html";
}
else {
$("#txtInfo").text(' 使用者名或者密碼錯誤！');
$(that).text('登 錄');
$(that).attr('disabled', false);
}
}
}); 3 背景用C#進行解密
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;//加密塊最大長度限制
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; //解密塊最大長度限制
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;
}
}
} 雖然将公鑰暴露在js檔案中，但是如果需要解密得到明文，必須需要私鑰（這個存儲在背景，不容易擷取）。調試運作，可以看到擷取的密碼是加密後的資料，然後在背景可以進行解密擷取到明文。