/// <summary>
/// Deserialize from the XML representation.
/// </summary>
/// <remarks>
/// Based upon https://www.w3.org/TR/xmldsig-core/#sec-DSAKeyValue.
/// </remarks>
/// <param name="value">
/// An <see cref="XmlElement"/> containing the XML representation. This cannot be null.
/// </param>
/// <exception cref="ArgumentNullException">
/// <paramref name="value"/> cannot be null.
/// </exception>
/// <exception cref="CryptographicException">
/// The XML has the incorrect schema or the DSA parameters are invalid.
/// </exception>
public override void LoadXml(XmlElement value)
{
if (value == null)
{
throw new ArgumentNullException(nameof(value));
}
if (value.Name != KeyValueElementName ||
value.NamespaceURI != SignedXml.XmlDsigNamespaceUrl)
{
throw new CryptographicException(SR.Format(SR.WrongRootElement, KeyValueElementName, SignedXml.XmlDsigNamespaceUrl));
}
const string xmlDsigNamespacePrefix = "dsig";
XmlNamespaceManager xmlNamespaceManager = new XmlNamespaceManager(value.OwnerDocument.NameTable);
xmlNamespaceManager.AddNamespace(xmlDsigNamespacePrefix, SignedXml.XmlDsigNamespaceUrl);
XmlNode dsaKeyValueElement = value.SelectSingleNode($"{xmlDsigNamespacePrefix}:{DSAKeyValueElementName}", xmlNamespaceManager);
if (dsaKeyValueElement == null)
{
throw new CryptographicException(SR.Format(SR.MustContainChildElement, KeyValueElementName, DSAKeyValueElementName));
}
XmlNode yNode = dsaKeyValueElement.SelectSingleNode($"{xmlDsigNamespacePrefix}:{YElementName}", xmlNamespaceManager);
if (yNode == null)
{
throw new CryptographicException(SR.Format(SR.ElementMissing, YElementName));
}
XmlNode pNode = dsaKeyValueElement.SelectSingleNode($"{xmlDsigNamespacePrefix}:{PElementName}", xmlNamespaceManager);
XmlNode qNode = dsaKeyValueElement.SelectSingleNode($"{xmlDsigNamespacePrefix}:{QElementName}", xmlNamespaceManager);
if ((pNode == null && qNode != null) || (pNode != null && qNode == null))
{
throw new CryptographicException(SR.Format(SR.ElementCombinationMissing, PElementName, QElementName));
}
XmlNode gNode = dsaKeyValueElement.SelectSingleNode($"{xmlDsigNamespacePrefix}:{GElementName}", xmlNamespaceManager);
XmlNode jNode = dsaKeyValueElement.SelectSingleNode($"{xmlDsigNamespacePrefix}:{JElementName}", xmlNamespaceManager);
XmlNode seedNode = dsaKeyValueElement.SelectSingleNode($"{xmlDsigNamespacePrefix}:{SeedElementName}", xmlNamespaceManager);
XmlNode pgenCounterNode = dsaKeyValueElement.SelectSingleNode($"{xmlDsigNamespacePrefix}:{PgenCounterElementName}", xmlNamespaceManager);
if ((seedNode == null && pgenCounterNode != null) || (seedNode != null && pgenCounterNode == null))
{
throw new CryptographicException(SR.Format(SR.ElementCombinationMissing, SeedElementName, PgenCounterElementName));
}
try
{
Key.ImportParameters(new DSAParameters
{
P = (pNode != null) ? Convert.FromBase64String(pNode.InnerText) : null,
Q = (qNode != null) ? Convert.FromBase64String(qNode.InnerText) : null,
G = (gNode != null) ? Convert.FromBase64String(gNode.InnerText) : null,
Y = Convert.FromBase64String(yNode.InnerText),
J = (jNode != null) ? Convert.FromBase64String(jNode.InnerText) : null,
Seed = (seedNode != null) ? Convert.FromBase64String(seedNode.InnerText) : null,
Counter = (pgenCounterNode != null) ? Utils.ConvertByteArrayToInt(Convert.FromBase64String(pgenCounterNode.InnerText)) : 0
});
}
catch (Exception ex)
{
throw new CryptographicException($"An error occurred parsing the key components", ex);
}
}