//------------------------------------------------------------
// Copyright (c) Microsoft Corporation. All rights reserved.
//------------------------------------------------------------
using System;
using System.Diagnostics;
using System.IdentityModel.Selectors;
using System.IO;
using System.Security.Cryptography;
using System.ServiceModel.Security;
using System.Text;
using System.Xml;
namespace System.IdentityModel.Tokens
{
/// <summary>
/// Token handler for an encrypted <see cref="SecurityToken"/> type.
/// </summary>
public class EncryptedSecurityTokenHandler : SecurityTokenHandler
{
static string[] _tokenTypeIdentifiers = new string[] { null };
SecurityTokenSerializer _keyInfoSerializer;
object _syncObject = new object();
/// <summary>
/// Create an instance of <see cref="EncryptedSecurityTokenHandler"/>
/// </summary>
public EncryptedSecurityTokenHandler()
{
}
/// <summary>
/// Indicates if the current XML element is pointing to a KeyIdentifierClause that
/// can be de-serialized by this instance.
/// </summary>
/// <param name="reader">An XML reader positioned at the start element.
/// The reader should not be advanced.</param>
/// <returns>true if the XML reader is positioned at an EncryptedKey xml element
/// as defined in section 3.5.1 of 'http://www.w3.org/TR/2002/REC-xmlenc-core-20021210'.</returns>
/// <exception cref="ArgumentNullException">The <paramref name="reader"/> is null.</exception>
public override bool CanReadKeyIdentifierClause(XmlReader reader)
{
if (reader == null)
{
throw DiagnosticUtility.ExceptionUtility.ThrowHelperArgumentNull("reader");
}
// <EncryptedKey>
return reader.IsStartElement(XmlEncryptionConstants.Elements.EncryptedKey, XmlEncryptionConstants.Namespace);
}
/// <summary>
/// Returns true if the reader is pointing to an EncryptedData element.
/// </summary>
/// <param name="reader">The reader positioned at a security token.</param>
/// <returns>true if the reader is positioned at EncryptedData else false.</returns>
/// <remarks>Does not move the reader when returning false.</remarks>
public override bool CanReadToken(XmlReader reader)
{
return EncryptedDataElement.CanReadFrom(reader);
}
/// <summary>
/// Overrides the base CanWriteToken and returns true always.
/// </summary>
public override bool CanWriteToken
{
get { return true; }
}
/// <summary>
/// Gets or Sets a SecurityTokenSerializers that will be used to serialize and deserializer
/// SecurtyKeyIdentifier of the <xenc:EncryptedData> element.
/// </summary>
/// <exception cref="ArgumentNullException">Input parameter 'value' is null.</exception>
public SecurityTokenSerializer KeyInfoSerializer
{
get
{
if ( _keyInfoSerializer == null )
{
lock ( _syncObject )
{
if ( _keyInfoSerializer == null )
{
SecurityTokenHandlerCollection sthc = ( ContainingCollection != null ) ?
ContainingCollection : SecurityTokenHandlerCollection.CreateDefaultSecurityTokenHandlerCollection();
_keyInfoSerializer = new SecurityTokenSerializerAdapter(sthc);
}
}
}
return _keyInfoSerializer;
}
set
{
if (value == null)
{
throw DiagnosticUtility.ExceptionUtility.ThrowHelperArgumentNull("value");
}
_keyInfoSerializer = value;
}
}
/// <summary>
/// Reads the encrypted security token.
/// </summary>
/// <param name="reader">The reader from which to read the token.</param>
/// <returns>An instance of <see cref="SecurityToken"/>.</returns>
/// <exception cref="ArgumentNullException">Input parameter 'reader' is null.</exception>
/// <exception cref="InvalidOperationException">One of the properties 'Configuration' or 'Configuration.ServiceTokenResolver' is null. This property is required for obtaining keys for decryption.</exception>
/// <exception cref="SecurityTokenException">A <see cref="SecurityKeyIdentifier"/> is not found inside the xml pointed to by the reader.</exception>
/// <exception cref="EncryptedTokenDecryptionFailedException">The <see cref="SecurityKeyIdentifier"/> found inside the xml cannot be resolved by Configuration.ServiceTokenResolver to a <see cref="SecurityKey"/>.</exception>
/// <exception cref="SecurityTokenException">The <see cref="SecurityKeyIdentifier"/> is not a <see cref="SymmetricSecurityKey"/>.</exception>
/// <exception cref="InvalidOperationException">The ContainingCollection (<see cref="SecurityTokenHandlerCollection"/>) is unable to find a <see cref="SecurityTokenHandler"/> that is able to read the decrypted xml and return a <see cref="SecurityToken"/>.</exception>
public override SecurityToken ReadToken(XmlReader reader)
{
if (null == reader)
{
throw DiagnosticUtility.ExceptionUtility.ThrowHelperArgumentNull("reader");
}
if (this.Configuration == null)
{
throw DiagnosticUtility.ThrowHelperInvalidOperation(SR.GetString(SR.ID4274));
}
if (this.Configuration.ServiceTokenResolver == null)
{
throw DiagnosticUtility.ThrowHelperInvalidOperation(SR.GetString(SR.ID4276));
}
//
// Read the encrypted data element
//
EncryptedDataElement encryptedData = new EncryptedDataElement(KeyInfoSerializer);
encryptedData.ReadXml(XmlDictionaryReader.CreateDictionaryReader(reader));
//
// All the clauses in a keyinfo must identify the same key, so we
// can try each clause in turn and stop when one resolves.
//
SecurityKey decryptionKey = null;
foreach (SecurityKeyIdentifierClause clause in encryptedData.KeyIdentifier)
{
this.Configuration.ServiceTokenResolver.TryResolveSecurityKey(clause, out decryptionKey);
if (null != decryptionKey)
{
break;
}
}
//
// Try to use the SKI to create the key instead.
//
if (decryptionKey == null && encryptedData.KeyIdentifier.CanCreateKey)
{
decryptionKey = encryptedData.KeyIdentifier.CreateKey();
}
//
// Fail if none of the clauses resolved or ski itself cannot create key.
//
if (null == decryptionKey)
{
EncryptedKeyIdentifierClause encryptedKeyClause;
if (encryptedData.KeyIdentifier.TryFind<EncryptedKeyIdentifierClause>(out encryptedKeyClause))
{
//
// System.IdentityModel.Tokens.EncryptedKeyIdentifierClause.ToString() does not print out
// very good information except the cipher data in this case. We have worked around that
// by using the token serializer to serialize the key identifier clause again.
//
throw DiagnosticUtility.ExceptionUtility.ThrowHelperError(
new EncryptedTokenDecryptionFailedException(
SR.GetString(SR.ID4036, XmlUtil.SerializeSecurityKeyIdentifier(encryptedData.KeyIdentifier, base.ContainingCollection.KeyInfoSerializer))));
}
else
{
throw DiagnosticUtility.ExceptionUtility.ThrowHelperError(
new EncryptedTokenDecryptionFailedException(SR.GetString(SR.ID4036, encryptedData.KeyIdentifier.ToString())));
}
}
//
// Need a symmetric key
//
SymmetricSecurityKey symmetricKey = decryptionKey as SymmetricSecurityKey;
if (null == symmetricKey)
{
throw DiagnosticUtility.ExceptionUtility.ThrowHelperError(
new SecurityTokenException(SR.GetString(SR.ID4023)));
}
//
// Do the actual decryption
//
byte[] plainText;
using (SymmetricAlgorithm decrypter = symmetricKey.GetSymmetricAlgorithm(encryptedData.Algorithm))
{
plainText = encryptedData.Decrypt(decrypter);
}
DebugEncryptedTokenClearText(plainText, Encoding.UTF8);
//
// Read and return the plaintext token
//
using (XmlReader innerTokenReader = XmlDictionaryReader.CreateTextReader(plainText, XmlDictionaryReaderQuotas.Max))
{
if (this.ContainingCollection != null && this.ContainingCollection.CanReadToken(innerTokenReader))
{
return this.ContainingCollection.ReadToken(innerTokenReader);
}
throw DiagnosticUtility.ThrowHelperInvalidOperation(SR.GetString(SR.ID4014, innerTokenReader.LocalName, innerTokenReader.NamespaceURI));
}
}
/// <summary>
/// Reads an EncryptedKeyIdentifierClause from a XML stream.
/// </summary>
/// <param name="reader">An XML reader positioned at an EncryptedKey element as defined in 'http://www.w3.org/TR/2002/REC-xmlenc-core-20021210' .</param>
/// <returns>SecurityKeyIdentifierClause instance of type EncryptedKeyIdentifierClause.</returns>
/// <exception cref="ArgumentNullException">The <paramref name="reader"/> is null.</exception>
/// <exception cref="InvalidOperationException">If the <paramref name="reader"/> is not positioned at an EncryptedKey element.</exception>
public override SecurityKeyIdentifierClause ReadKeyIdentifierClause(XmlReader reader)
{
if (reader == null)
{
throw DiagnosticUtility.ExceptionUtility.ThrowHelperArgumentNull("reader");
}
// <EncryptedKey>
if (reader.IsStartElement(XmlEncryptionConstants.Elements.EncryptedKey, XmlEncryptionConstants.Namespace))
{
EncryptedKeyElement encryptedKey = new EncryptedKeyElement(KeyInfoSerializer);
encryptedKey.ReadXml(XmlDictionaryReader.CreateDictionaryReader(reader));
return new EncryptedKeyIdentifierClause(encryptedKey.CipherData.CipherValue, encryptedKey.Algorithm, encryptedKey.KeyIdentifier);
}
throw DiagnosticUtility.ExceptionUtility.ThrowHelperError(new InvalidOperationException(SR.GetString(SR.ID3275, reader.Name, reader.NamespaceURI)));
}
[Conditional("DEBUG")]
static void DebugEncryptedTokenClearText(byte[] bytes, Encoding encoding)
{
string text = encoding.GetString(bytes);
Debug.WriteLine(text.Substring(0, 40));
}
/// <summary>
/// Gets the System.Type of the token that this SecurityTokenHandler handles.
/// Returns typeof <see cref="EncryptedSecurityToken"/> by default.
/// </summary>
public override Type TokenType
{
get { return typeof(EncryptedSecurityToken); }
}
/// <summary>
/// By default returns an array with a single null string as there isn't any specific TokenType identifier that is
/// associated with a <see cref="EncryptedSecurityToken"/>.
/// </summary>
public override string[] GetTokenTypeIdentifiers()
{
return _tokenTypeIdentifiers;
}
/// <summary>
/// Writes a <see cref="EncryptedSecurityToken"/> using the xmlWriter.
/// </summary>
/// <param name="writer">The XmlWriter to which the encrypted token is written.</param>
/// <param name="token">The <see cref="SecurityToken"/> which must be an instance of <see cref="EncryptedSecurityToken"/>.</param>
/// <exception cref="ArgumentNullException">The input prameter 'writer' is null.</exception>
/// <exception cref="ArgumentNullException">The input prameter 'token' is null.</exception>
/// <exception cref="ArgumentException">The <see cref="SecurityToken"/> is not an instance of <see cref="EncryptedSecurityToken"/>.</exception>
/// <exception cref="InvalidOperationException">The property 'Configuration' is null. This property is required for obtaining keys for encryption.</exception>
/// <exception cref="InvalidOperationException">The ContaingCollection was unable to find a <see cref="SecurityTokenHandler"/> that is able to write
/// the <see cref="SecurityToken"/> returned by 'EncryptedSecurityToken.Token'.</exception>
/// <exception cref="SecurityTokenException">The property 'EncryptinCredentials.SecurityKey is not a <see cref="SymmetricSecurityKey"/></exception>
public override void WriteToken(XmlWriter writer, SecurityToken token)
{
if (null == writer)
{
throw DiagnosticUtility.ExceptionUtility.ThrowHelperArgumentNull("writer");
}
if (null == token)
{
throw DiagnosticUtility.ExceptionUtility.ThrowHelperArgumentNull("token");
}
EncryptedSecurityToken encryptedToken = token as EncryptedSecurityToken;
if (null == encryptedToken)
{
throw DiagnosticUtility.ExceptionUtility.ThrowHelperArgument("token", SR.GetString(SR.ID4024));
}
if (this.ContainingCollection == null)
{
throw DiagnosticUtility.ThrowHelperInvalidOperation(SR.GetString(SR.ID4279));
}
//
// This implementation simply wraps the token in xenc:EncryptedData
//
EncryptedDataElement encryptedData = new EncryptedDataElement(KeyInfoSerializer);
using (MemoryStream plaintextStream = new MemoryStream())
{
//
// Buffer the plaintext
//
using (XmlDictionaryWriter plaintextWriter = XmlDictionaryWriter.CreateTextWriter(plaintextStream, Encoding.UTF8, false))
{
SecurityTokenHandler securityTokenHandler = this.ContainingCollection[encryptedToken.Token.GetType()];
if (securityTokenHandler != null)
{
securityTokenHandler.WriteToken(plaintextWriter, encryptedToken.Token);
}
else
{
throw DiagnosticUtility.ThrowHelperInvalidOperation(SR.GetString(SR.ID4224, encryptedToken.Token.GetType()));
}
}
//
// Set up the EncryptedData element
//
EncryptingCredentials encryptingCredentials = encryptedToken.EncryptingCredentials;
encryptedData.Type = XmlEncryptionConstants.EncryptedDataTypes.Element;
encryptedData.KeyIdentifier = encryptingCredentials.SecurityKeyIdentifier;
encryptedData.Algorithm = encryptingCredentials.Algorithm;
//
// Get the encryption key, which must be symmetric
//
SymmetricSecurityKey encryptingKey = encryptingCredentials.SecurityKey as SymmetricSecurityKey;
if (encryptingKey == null)
{
throw DiagnosticUtility.ExceptionUtility.ThrowHelperError(new SecurityTokenException(SR.GetString(SR.ID3064)));
}
//
// Do the actual encryption
//
using (SymmetricAlgorithm symmetricAlgorithm = encryptingKey.GetSymmetricAlgorithm(encryptingCredentials.Algorithm))
{
byte[] plainTextBytes = plaintextStream.GetBuffer();
DebugEncryptedTokenClearText(plainTextBytes, Encoding.UTF8);
encryptedData.Encrypt(symmetricAlgorithm, plainTextBytes, 0, (int)plaintextStream.Length);
}
}
//
// Write the EncryptedData element
//
encryptedData.WriteXml(writer, KeyInfoSerializer);
}
}
}