Protected Configuration Provider Implementation Example

The following code example shows how to implement a protected configuration provider. For details about how to build this provider and use it in an ASP.NET application, see How to: Build and Run the Protected Configuration Provider Example.

Example

Imports System
Imports System.Xml
Imports System.Security.Cryptography
Imports System.IO
Imports System.Text
Imports System.Configuration.Provider
Imports System.Collections.Specialized
Imports System.Configuration


Namespace Samples.AspNet.ProtectedConfiguration

  Public Class TripleDESProtectedConfigurationProvider
    Inherits ProtectedConfigurationProvider

    Private des As TripleDESCryptoServiceProvider = New TripleDESCryptoServiceProvider()
  
    Private pKeyFilePath As String
    Private pName As String

    Public ReadOnly Property KeyFilePath As String
      Get
        Return pKeyFilePath
      End Get
    End Property

    '
    ' ProviderBase.Name
    '

    Public Overrides ReadOnly Property Name As String    
      Get
        Return pName
      End Get
    End Property


    '
    ' ProviderBase.Initialize
    '

    Public Overrides Sub Initialize(name As String, config As NameValueCollection)
      pName = name
      pKeyFilePath = config("keyFilePath")
      ReadKey(KeyFilePath)
    End Sub


    '
    ' ProtectedConfigurationProvider.Encrypt
    '

    Public Overrides Function Encrypt(node As XmlNode ) As XmlNode 
      Dim encryptedData As String = EncryptString(node.OuterXml)

      Dim xmlDoc As XmlDocument = New XmlDocument()
      xmlDoc.PreserveWhitespace = True
      xmlDoc.LoadXml("<EncryptedData>" & encryptedData & "</EncryptedData>")
                  
      Return xmlDoc.DocumentElement
    End Function


    '
    ' ProtectedConfigurationProvider.Decrypt
    '

    Public Overrides Function Decrypt(encryptedNode As XmlNode) As XmlNode
      Dim decryptedData As String = DecryptString(encryptedNode.InnerText)

      Dim xmlDoc As XmlDocument = New XmlDocument()
      xmlDoc.PreserveWhitespace = True
      xmlDoc.LoadXml(decryptedData)  

      Return xmlDoc.DocumentElement
    End Function


    '
    ' EncryptString
    '    Encrypts a configuration section and returns the encrypted
    ' XML as a string.
    '
    
    Private Function EncryptString(encryptValue As String) As String
    
      Dim valBytes() As Byte = Encoding.Unicode.GetBytes(encryptValue)

      Dim transform As ICryptoTransform = des.CreateEncryptor()

      Dim ms As MemoryStream = New MemoryStream()
      Dim cs As CryptoStream = New CryptoStream(ms, transform, CryptoStreamMode.Write)
      cs.Write(valBytes, 0, valBytes.Length)
      cs.FlushFinalBlock()
      Dim returnBytes() As Byte = ms.ToArray()
      cs.Close()

      Return Convert.ToBase64String(returnBytes)
    End Function


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

    Private Function DecryptString(encryptedValue As String) As String
      Dim valBytes() As Byte = Convert.FromBase64String(encryptedValue)

      Dim transform As ICryptoTransform = des.CreateDecryptor()

      Dim ms As MemoryStream = New MemoryStream()
      Dim cs As CryptoStream = New CryptoStream(ms, transform, CryptoStreamMode.Write)
      cs.Write(valBytes, 0, valBytes.Length)
      cs.FlushFinalBlock()
      Dim returnBytes() As Byte = ms.ToArray()
      cs.Close()

      Return Encoding.Unicode.GetString(returnBytes)
    End Function


    '
    ' CreateKey
    '    Generates a New TripleDES key and vector and writes them
    ' to the supplied file path.
    '

    Public Sub CreateKey(filePath As String)
      des.GenerateKey()
      des.GenerateIV()

      Dim sw As StreamWriter = New StreamWriter(filePath, false)
      sw.WriteLine(ByteToHex(des.Key))
      sw.WriteLine(ByteToHex(des.IV))
      sw.Close()
    End Sub


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

    Private Sub ReadKey(filePath As String)
      Dim sr As StreamReader = New StreamReader(filePath)
      Dim keyValue As String = sr.ReadLine()
      Dim ivValue As String = sr.ReadLine()

      des.Key = HexToByte(keyValue)
      des.IV = HexToByte(ivValue)
    End Sub


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

    Private Function ByteToHex(byteArray As Byte()) As String
      Dim outString As String = ""

      For Each b As Byte In byteArray
        outString &= b.ToString("X2")
      Next

      Return outString
    End Function


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

    Private Function HexToByte(hexString As String) As Byte()
      Dim returnBytes() As Byte = New Byte(CInt((hexString.Length / 2) - 1)) {}

      For i As Integer= 0 To returnBytes.Length - 1
        returnBytes(i) = Convert.ToByte(hexString.Substring(i*2, 2), 16)
      Next

      Return returnBytes
    End Function

  End Class
End Namespace

using System;
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 Samples.AspNet.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;
    }

  }
}

See Also

Tasks

How to: Build and Run the Protected Configuration Provider Example

Concepts

Implementing a Protected Configuration Provider

Other Resources

Encrypting Configuration Information Using Protected Configuration