背景

在程序或服务开发过程中，我们通常会把一些程序需要用到的常量数据配置在web.config或app.config文件中，通常配置到这些文件中的Key与Value都是明文的，但有时候我们并不希望这些配置让他人知道。
在这种情况下，我们可以使用ASP.NET Encrypt和Decrypt来对配置文件进行加密，不影响程序使用，但又不被他人知道配置的具体内容。

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环境

1. Windonw 7 / Windows Server 2008
2. .Net Framework 4.0
3. IIS

以上环境准备好后，在搭建好的IIS上创建三个站点 WebSite1, WebSite2, WebSite3

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工具

1. asp.net_regiis.exe
2. vs 2010 tool
3. sn.exe
4. gacutil.exe

asp.net_regiis.exe位于路径C:\Windows\Microsoft.NET\Framework64\v4.0.30319
使用管理员身份运行cmd.exe
Start --> All Programs --> Microsoft Visual Studio 2010 --> Visual Studio Tools --> Visual Studio x64 Win64 Command Prompt (2010)(run as administrator)
sn, gacutil 在VS 2010 tool中可直接使用

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Providers in .NET Framework

• DpapiProtectedConfigurationProvider
  uses the Windows Data Protected API(DPAPI) to encrypt and Decrypt data.

• RsaProtectedConfigurationProvider
  useed the RSA encryption algorithm to encrypt and Decrypt data.

Providers means Protected configuration Providers

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Machine-Level and User-Level

Machine-Level

available to all users
Machine-level 的Key对所有管理员用户有效果，但也受ACLs的约束

User-Level

available only to the user that created the key container.
stored with the Windonw user profile for a particular user
userd to encrypt and decrypt information for applications that run under that specific user identity.
user-level 的Key是与用户账号绑定的，用户被删除时，key也被删除

这里所讲的avalliable是指能够加密和解密

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Tool and Parameters

Tool

asp.net_regiis.exe

encrypt parameters

-pe the name of the configuraiton element to be encrypt
-app identity the application for which the web.config file will be encrypted
-site identity which web site the application is a part of
-prov identity the name of the ProtectedConfigurationProvider that will preform the encryption and decryption.
pe, app 是必须要指定的值
site默认值为1, prov默认使用defaultProvider

decrypt parameters

-pd the name of the configuration element to be decrypted.
-app identify the application for which the web.config file will be encrypted
-site identify which Web site the application is a part of
-prov not need to specify
在解密时不需要使用prov来指定ProtectedConfigurationProvider，because that information is read from the configProtectionProvider attribute of the protected configuration section.

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Encrypting Website’s Web.config

在VS Tool中输入以下命令

aspnet_regiis -pef "connectionStrings" E:\webSite1

或

aspnet_regiis -pe "connectionStrings" -app "/WebSite1" -site "WebSite1"

需要为WebSite1添加虚拟目录
或

aspnet_regiss -pe "connectionStrings" -app "/WebSite1" -site "WebSite1" -prov DataProtectionConfigurationProvider

需要为WebSite1添加虚拟目录，指定Provider

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解密

aspnet_regiis -pd "connectionStrings" -app "/WebSite1" -site "WebSite1"

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Create a RSA Key Container

Tool

aspnet_regiis

Parameters

-pc : the name of the key container used by the RsaProtectedConfigurationProvider specified in the configProtectedData section of web.config file
-exp : ensure that RSA key container can be exported

Web.config的配置

<configProtectedData>
    <providers>
        <add name="CustomerProvider" keyContainerName="SampleKeys" useMachineContainer="true" description="Users RsaCryptoSErviceProvider to encrypt and decrypt" type="System.Configuration.RsaProtectedConfigurationProvider, System.Configuration, Version=4.0.0.0, Cultuer=neutral, PublicKeyToken=b03f5f7f11d50a3a">
    </providers>
</configProtectedData>

以上配置中的KeyContainerName="true",表示使用Machine-level, false表示使用user-level
加密时使用以下命令

aspnet_regiis -pe "connectionStrings" -app "/WebSite2" -site "WebSite2" -prov "CustomeProvider"

Exporting a RSA Key Container

使用命令

aspnet_regiis -px "SampleKeys" E:\MachineSmapleKey.xml -pri

Importing a RSA Key Container

aspnet_regiis -pi "MyKeys" keys.xml -pku

Deleting a RSA Key Container

aspnet_regiis -pz "MyKeys"

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Custome Provider Type

Implementing a Protected Configuration Provider

• Algorithm
  an algorithm other than those available with the RSA or DPAPI providers
• Required Classes
  ProtectedConfigurationProvider class from the System.Configuration namespace
  ProviderBase class from the System.Configuration.Provider namespace
• Required Members
  Initialize method (from ProviderBase)
  Encrypt method (from ProtectedConfigurationProvider)
  Decrypt method (from ProtectedConfigurationProvider)

Build Protected Configuration Provider

• Generate a strong-name key pair

sn -k keys.snk

• Create a program file named TripleDESProtectedConfigurationProvider

using System.Xml;
using System.Security.Cryptography;
using System.IO;
using System.Text;
using System.Configuration.Provider;
using System.Collections.Specialized;
using System.Configuration;


namespace AA.BB.ProtectedConfiguration
{

  public class TripleDESProtectedConfigurationProvider : ProtectedConfigurationProvider
  {

    private TripleDESCryptoServiceProvider des = new TripleDESCryptoServiceProvider();

    private string pKeyFilePath;
    private string pName;

    public string KeyFilePath
    {
      get { return pKeyFilePath; }
    }


    //
    // ProviderBase.Name
    //

    public override string Name
    {
      get { return pName; }
    }


    //
    // ProviderBase.Initialize
    //

    public override void Initialize(string name, NameValueCollection config)
    {
      pName = name;
      pKeyFilePath = config["keyFilePath"];
      ReadKey(KeyFilePath);
    }


    //
    // ProtectedConfigurationProvider.Encrypt
    //

    public override XmlNode Encrypt(XmlNode node)
    {
      string encryptedData = EncryptString(node.OuterXml);

      XmlDocument xmlDoc = new XmlDocument();
      xmlDoc.PreserveWhitespace = true;
      xmlDoc.LoadXml("<EncryptedData>" + encryptedData + "</EncryptedData>");

      return xmlDoc.DocumentElement;
    }


    //
    // ProtectedConfigurationProvider.Decrypt
    //

    public override XmlNode Decrypt(XmlNode encryptedNode)
    {
      string decryptedData = DecryptString(encryptedNode.InnerText);

      XmlDocument xmlDoc = new XmlDocument();
      xmlDoc.PreserveWhitespace = true;
      xmlDoc.LoadXml(decryptedData);  

      return xmlDoc.DocumentElement;
    }


    //
    // EncryptString
    //    Encrypts a configuration section and returns the encrypted
    // XML as a string.
    //

    private string EncryptString(string encryptValue)
    {
      byte[] valBytes = Encoding.Unicode.GetBytes(encryptValue);

      ICryptoTransform transform = des.CreateEncryptor();

      MemoryStream ms = new MemoryStream();
      CryptoStream cs = new CryptoStream(ms, transform, CryptoStreamMode.Write);
      cs.Write(valBytes, 0, valBytes.Length);
      cs.FlushFinalBlock();
      byte[] returnBytes = ms.ToArray();
      cs.Close();

      return Convert.ToBase64String(returnBytes);
    }


    //
    // DecryptString
    //    Decrypts an encrypted configuration section and returns the
    // unencrypted XML as a string.
    //

    private string DecryptString(string encryptedValue)
    {
      byte[] valBytes = Convert.FromBase64String(encryptedValue);

      ICryptoTransform transform = des.CreateDecryptor();

      MemoryStream ms = new MemoryStream();
      CryptoStream cs = new CryptoStream(ms, transform, CryptoStreamMode.Write);
      cs.Write(valBytes, 0, valBytes.Length);
      cs.FlushFinalBlock();
      byte[] returnBytes = ms.ToArray();
      cs.Close();

      return Encoding.Unicode.GetString(returnBytes);
    }

    //
    // CreateKey
    //    Generates a new TripleDES key and vector and writes them
    // to the supplied file path.
    //

    public void CreateKey(string filePath)
    {
      des.GenerateKey();
      des.GenerateIV();

      StreamWriter sw = new StreamWriter(filePath, false);
      sw.WriteLine(ByteToHex(des.Key));
      sw.WriteLine(ByteToHex(des.IV));
      sw.Close();
    }


    //
    // ReadKey
    //    Reads in the TripleDES key and vector from the supplied
    // file path and sets the Key and IV properties of the 
    // TripleDESCryptoServiceProvider.
    //

    private void ReadKey(string filePath)
    {
      StreamReader sr = new StreamReader(filePath);
      string keyValue = sr.ReadLine();
      string ivValue = sr.ReadLine();
      des.Key = HexToByte(keyValue);
      des.IV = HexToByte(ivValue);
    }


    //
    // ByteToHex
    //    Converts a byte array to a hexadecimal string.
    //

    private string ByteToHex(byte[] byteArray)
    {
      string outString = "";

      foreach (Byte b in byteArray)
        outString += b.ToString("X2");

      return outString;
    }

    //
    // HexToByte
    //    Converts a hexadecimal string to a byte array.
    //

    private byte[] HexToByte(string hexString)
    {
      byte[] returnBytes = new byte[hexString.Length / 2];
      for (int i = 0; i < returnBytes.Length; i++)
        returnBytes[i] = Convert.ToByte(hexString.Substring(i*2, 2), 16);
      return returnBytes;
    }

  }
}

• Compile the code and assign the resulting assembly with the strong-name key

csc /out:TripleDESProtectedConfigurationProvider.dll /t:library TripleDESProtectedConfigurationProvider.cs /r:System.Configuration.dll /keyfile:keys.snk

• Install the assembly in the GAC(global assembly cach)

  gacutil -i TripleDESProtectedConfigurationProvider.dll

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Use a Custom Provider type

• Generate Key File

  CreateKey.exe E:\ASP\Keys.txt

• Modify the configProtectedData Section of the Web.config

<configProtectedData>
    <providers>
        <add name="SampleProvider"  useMachineContainer="true" type="AA.BB.TripleDESProtectedConfigurationProvider TripleDESProtectedConfigurationProvider  Version=0.0.0.0, Cultuer=neutral  PublicKeyToken=b06675f7f11d50a3a",description="Users RsaCryptoSErviceProvider to encrypt and decrypt" keyFilePath="E:\ASP\Key" >    
    </providers>
</configProtectedData>