public override void LoadXml(XmlElement value)
{
_encryptedKey = new EncryptedKey();
_encryptedKey.LoadXml(value);
}
// default behaviour is to look for keys defined by an EncryptedKey clause
// either directly or through a KeyInfoRetrievalMethod, and key names in the key mapping
public virtual SymmetricAlgorithm GetDecryptionKey(EncryptedData encryptedData, string symmetricAlgorithmUri)
{
if (encryptedData == null)
{
throw new ArgumentNullException(nameof(encryptedData));
}
if (encryptedData.KeyInfo == null)
{
return(null);
}
IEnumerator keyInfoEnum = encryptedData.KeyInfo.GetEnumerator();
KeyInfoRetrievalMethod kiRetrievalMethod;
KeyInfoName kiName;
KeyInfoEncryptedKey kiEncKey;
EncryptedKey ek = null;
while (keyInfoEnum.MoveNext())
{
kiName = keyInfoEnum.Current as KeyInfoName;
if (kiName != null)
{
// Get the decryption key from the key mapping
string keyName = kiName.Value;
if ((SymmetricAlgorithm)_keyNameMapping[keyName] != null)
{
return((SymmetricAlgorithm)_keyNameMapping[keyName]);
}
// try to get it from a CarriedKeyName
XmlNamespaceManager nsm = new XmlNamespaceManager(_document.NameTable);
nsm.AddNamespace("enc", EncryptedXml.XmlEncNamespaceUrl);
XmlNodeList encryptedKeyList = _document.SelectNodes("//enc:EncryptedKey", nsm);
if (encryptedKeyList != null)
{
foreach (XmlNode encryptedKeyNode in encryptedKeyList)
{
XmlElement encryptedKeyElement = encryptedKeyNode as XmlElement;
EncryptedKey ek1 = new EncryptedKey();
ek1.LoadXml(encryptedKeyElement);
if (ek1.CarriedKeyName == keyName && ek1.Recipient == Recipient)
{
ek = ek1;
break;
}
}
}
break;
}
kiRetrievalMethod = keyInfoEnum.Current as KeyInfoRetrievalMethod;
if (kiRetrievalMethod != null)
{
string idref = Utils.ExtractIdFromLocalUri(kiRetrievalMethod.Uri);
ek = new EncryptedKey();
ek.LoadXml(GetIdElement(_document, idref));
break;
}
kiEncKey = keyInfoEnum.Current as KeyInfoEncryptedKey;
if (kiEncKey != null)
{
ek = kiEncKey.EncryptedKey;
break;
}
}
// if we have an EncryptedKey, decrypt to get the symmetric key
if (ek != null)
{
// now process the EncryptedKey, loop recursively
// If the Uri is not provided by the application, try to get it from the EncryptionMethod
if (symmetricAlgorithmUri == null)
{
if (encryptedData.EncryptionMethod == null)
{
throw new CryptographicException(SR.Cryptography_Xml_MissingAlgorithm);
}
symmetricAlgorithmUri = encryptedData.EncryptionMethod.KeyAlgorithm;
}
byte[] key = DecryptEncryptedKey(ek);
if (key == null)
{
throw new CryptographicException(SR.Cryptography_Xml_MissingDecryptionKey);
}
SymmetricAlgorithm symAlg = CryptoHelpers.CreateFromName <SymmetricAlgorithm>(symmetricAlgorithmUri);
if (symAlg == null)
{
throw new CryptographicException(SR.Cryptography_Xml_MissingAlgorithm);
}
symAlg.Key = key;
return(symAlg);
}
return(null);
}
public KeyInfoEncryptedKey(EncryptedKey encryptedKey)
{
_encryptedKey = encryptedKey;
}
