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DpapiProtectedConfigurationProvider.cs
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DpapiProtectedConfigurationProvider.cs
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// Licensed to the .NET Foundation under one or more agreements.
// The .NET Foundation licenses this file to you under the MIT license.
using System.Collections.Specialized;
using System.Runtime.Versioning;
using System.Security.Cryptography;
using System.Text;
using System.Xml;
namespace System.Configuration
{
[SupportedOSPlatform("windows")]
public sealed class DpapiProtectedConfigurationProvider : ProtectedConfigurationProvider
{
private bool _useMachineProtection = true;
private string _keyEntropy;
public override XmlNode Decrypt(XmlNode encryptedNode)
{
if (encryptedNode.NodeType != XmlNodeType.Element ||
encryptedNode.Name != "EncryptedData")
{
throw new ConfigurationErrorsException(SR.DPAPI_bad_data);
}
XmlNode cipherNode = TraverseToChild(encryptedNode, "CipherData", false);
if (cipherNode == null)
throw new ConfigurationErrorsException(SR.DPAPI_bad_data);
XmlNode cipherValue = TraverseToChild(cipherNode, "CipherValue", true);
if (cipherValue == null)
throw new ConfigurationErrorsException(SR.DPAPI_bad_data);
string encText = cipherValue.InnerText;
if (encText == null)
throw new ConfigurationErrorsException(SR.DPAPI_bad_data);
string decText = DecryptText(encText);
XmlDocument xmlDocument = new XmlDocument();
xmlDocument.PreserveWhitespace = true;
xmlDocument.LoadXml(decText);
return xmlDocument.DocumentElement;
}
public override XmlNode Encrypt(XmlNode node)
{
string text = node.OuterXml;
string encText = EncryptText(text);
string pre = @"<EncryptedData><CipherData><CipherValue>";
string post = @"</CipherValue></CipherData></EncryptedData>";
string xmlText = pre + encText + post;
XmlDocument xmlDocument = new XmlDocument();
xmlDocument.PreserveWhitespace = true;
xmlDocument.LoadXml(xmlText);
return xmlDocument.DocumentElement;
}
private string EncryptText(string clearText)
{
if (clearText == null || clearText.Length < 1)
return clearText;
byte[] inputData = PrepareDataBlob(clearText);
byte[] entropyData = PrepareDataBlob(_keyEntropy);
byte[] encryptedData = ProtectedData.Protect(
userData: inputData,
optionalEntropy: entropyData,
scope: UseMachineProtection ? DataProtectionScope.LocalMachine : DataProtectionScope.CurrentUser);
return Convert.ToBase64String(encryptedData);
}
private string DecryptText(string encText)
{
if (encText == null || encText.Length < 1)
return encText;
byte[] inputData = Convert.FromBase64String(encText);
byte[] entropyData = PrepareDataBlob(_keyEntropy);
byte[] decryptedData = ProtectedData.Unprotect(
encryptedData: inputData,
optionalEntropy: entropyData,
scope: UseMachineProtection ? DataProtectionScope.LocalMachine : DataProtectionScope.CurrentUser);
return Encoding.Unicode.GetString(decryptedData);
}
public bool UseMachineProtection { get { return _useMachineProtection; } }
public override void Initialize(string name, NameValueCollection configurationValues)
{
base.Initialize(name, configurationValues);
_useMachineProtection = GetBooleanValue(configurationValues, "useMachineProtection", true);
_keyEntropy = configurationValues["keyEntropy"];
configurationValues.Remove("keyEntropy");
if (configurationValues.Count > 0)
throw new ConfigurationErrorsException(SR.Format(SR.Unrecognized_initialization_value, configurationValues.GetKey(0)));
}
private static XmlNode TraverseToChild(XmlNode node, string name, bool onlyChild)
{
foreach (XmlNode child in node.ChildNodes)
{
if (child.NodeType != XmlNodeType.Element)
continue;
if (child.Name == name)
return child; // found it!
if (onlyChild)
return null;
}
return null;
}
private static byte[] PrepareDataBlob(string s)
{
return (s != null) ? Encoding.Unicode.GetBytes(s) : Array.Empty<byte>();
}
private static bool GetBooleanValue(NameValueCollection configurationValues, string valueName, bool defaultValue)
{
string s = configurationValues[valueName];
if (s == null)
return defaultValue;
configurationValues.Remove(valueName);
if (s == "true")
return true;
if (s == "false")
return false;
throw new ConfigurationErrorsException(SR.Format(SR.Config_invalid_boolean_attribute, valueName));
}
}
}