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//------------------------------------------------------------
// Copyright (c) Microsoft Corporation. All rights reserved.
//------------------------------------------------------------
namespace System.IdentityModel
{
using System;
using System.IdentityModel.Selectors;
using System.IdentityModel.Tokens;
using System.Security.Cryptography;
using System.Xml;
/// <summary>
/// This class implements a deserialization for: EncryptedData as defined in section 3.4 of http://www.w3.org/TR/2002/REC-xmlenc-core-2002120
/// </summary>
internal class EncryptedDataElement : EncryptedTypeElement
{
public static bool CanReadFrom( XmlReader reader )
{
return reader != null && reader.IsStartElement(
XmlEncryptionConstants.Elements.EncryptedData,
XmlEncryptionConstants.Namespace );
}
public EncryptedDataElement()
: this( null )
{
}
public EncryptedDataElement( SecurityTokenSerializer tokenSerializer )
: base( tokenSerializer )
{
KeyIdentifier = new SecurityKeyIdentifier( new EmptySecurityKeyIdentifierClause() );
}
/// <summary>
/// Decrypts the data
/// </summary>
/// <param name="algorithm"></param>
/// <returns></returns>
/// <exception cref="ArgumentNullException">When algorithm is null</exception>
/// <exception cref="InvalidOperationException">When no cipher data has been read</exception>
public byte[] Decrypt( SymmetricAlgorithm algorithm )
{
if ( algorithm == null )
{
throw DiagnosticUtility.ExceptionUtility.ThrowHelperArgumentNull( "algorithm" );
}
if ( CipherData == null || CipherData.CipherValue == null )
{
throw DiagnosticUtility.ExceptionUtility.ThrowHelperError( new InvalidOperationException( SR.GetString( SR.ID6000 ) ) );
}
byte[] cipherText = CipherData.CipherValue;
return ExtractIVAndDecrypt( algorithm, cipherText, 0, cipherText.Length );
}
public void Encrypt( SymmetricAlgorithm algorithm, byte[] buffer, int offset, int length )
{
byte[] iv;
byte[] cipherText;
GenerateIVAndEncrypt( algorithm, buffer, offset, length, out iv, out cipherText );
CipherData.SetCipherValueFragments( iv, cipherText );
}
static byte[] ExtractIVAndDecrypt( SymmetricAlgorithm algorithm, byte[] cipherText, int offset, int count )
{
byte[] iv = new byte[algorithm.BlockSize / 8];
//
// Make sure cipherText has enough bytes after the offset, for Buffer.BlockCopy to copy.
//
if ( cipherText.Length - offset < iv.Length )
{
throw DiagnosticUtility.ExceptionUtility.ThrowHelperError( new InvalidOperationException( SR.GetString( SR.ID6019, cipherText.Length - offset, iv.Length ) ) );
}
Buffer.BlockCopy( cipherText, offset, iv, 0, iv.Length );
algorithm.Padding = PaddingMode.ISO10126;
algorithm.Mode = CipherMode.CBC;
ICryptoTransform decrTransform = null;
byte[] plainText = null;
try
{
decrTransform = algorithm.CreateDecryptor( algorithm.Key, iv );
plainText = decrTransform.TransformFinalBlock( cipherText, offset + iv.Length, count - iv.Length );
}
finally
{
if ( decrTransform != null )
{
decrTransform.Dispose();
}
}
return plainText;
}
static void GenerateIVAndEncrypt( SymmetricAlgorithm algorithm, byte[] plainText, int offset, int length, out byte[] iv, out byte[] cipherText )
{
RandomNumberGenerator random = CryptoHelper.RandomNumberGenerator;
int ivSize = algorithm.BlockSize / 8;
iv = new byte[ivSize];
random.GetBytes( iv );
algorithm.Padding = PaddingMode.PKCS7;
algorithm.Mode = CipherMode.CBC;
ICryptoTransform encrTransform = algorithm.CreateEncryptor( algorithm.Key, iv );
cipherText = encrTransform.TransformFinalBlock( plainText, offset, length );
encrTransform.Dispose();
}
public override void ReadExtensions( XmlDictionaryReader reader )
{
// nothing to do here
}
/// <summary>
/// Reads an EncryptedData element
/// </summary>
/// <param name="reader"></param>
/// <exception cref="ArgumentNullException">When reader is null</exception>
/// <exception cref="ArgumentNullException">When securityTokenSerializer is null</exception>
public override void ReadXml( XmlDictionaryReader reader )
{
if ( reader == null )
{
throw DiagnosticUtility.ExceptionUtility.ThrowHelperArgumentNull( "reader" );
}
reader.MoveToContent();
if ( !reader.IsStartElement( XmlEncryptionConstants.Elements.EncryptedData, XmlEncryptionConstants.Namespace ) )
{
throw DiagnosticUtility.ThrowHelperXml( reader, SR.GetString( SR.ID4193 ) );
}
// <EncryptedData> extends <EncryptedType>
// base will read the start element and the end element.
base.ReadXml( reader );
}
/// <summary>
/// Writes the EncryptedData element
/// </summary>
/// <param name="writer"></param>
/// <param name="securityTokenSerializer"></param>
/// <exception cref="ArgumentNullException">When securityTokenSerializer is null</exception>
/// <exception cref="InvalidOperationException">When KeyIdentifier is null</exception>
public virtual void WriteXml( XmlWriter writer, SecurityTokenSerializer securityTokenSerializer )
{
if ( writer == null )
{
throw DiagnosticUtility.ExceptionUtility.ThrowHelperArgumentNull( "writer" );
}
if ( securityTokenSerializer == null )
{
throw DiagnosticUtility.ExceptionUtility.ThrowHelperArgumentNull( "securityTokenSerializer" );
}
if ( KeyIdentifier == null )
{
throw DiagnosticUtility.ExceptionUtility.ThrowHelperError( new InvalidOperationException( SR.GetString( SR.ID6001 ) ) );
}
// <EncryptedData>
writer.WriteStartElement( XmlEncryptionConstants.Prefix, XmlEncryptionConstants.Elements.EncryptedData, XmlEncryptionConstants.Namespace );
if ( !string.IsNullOrEmpty( Id ) )
{
writer.WriteAttributeString( XmlEncryptionConstants.Attributes.Id, null, Id );
}
if ( !string.IsNullOrEmpty( Type ) )
{
writer.WriteAttributeString( XmlEncryptionConstants.Attributes.Type, null, Type );
}
if ( EncryptionMethod != null )
{
EncryptionMethod.WriteXml( writer );
}
if ( KeyIdentifier != null )
{
securityTokenSerializer.WriteKeyIdentifier( XmlDictionaryWriter.CreateDictionaryWriter( writer ), KeyIdentifier );
}
CipherData.WriteXml( writer );
// <EncryptedData>
writer.WriteEndElement();
}
}
}
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