Unable to sign element by Id attribute when there's a namespace prefix:
void Main()
{
var doc = new XmlDocument();
doc.LoadXml("<root xmlns:u=\"myuri\"><test u:Id=\"_0\">Zebra</test></root>");
SignedXml signedXml = new SignedXml(doc);
signedXml.SigningKey = new RSACryptoServiceProvider();
Reference reference = new Reference("#_0");
signedXml.AddReference(reference);
signedXml.ComputeSignature();
}
ComputeSignature()
will fail here with 'Malformed Reference Element' how should this be done?
The approach we used was to subclass System.Security.Cryptography.Xml.SignedXml
class...
public class SignedXmlWithId : SignedXml
{
public SignedXmlWithId(XmlDocument xml) : base(xml)
{
}
public SignedXmlWithId(XmlElement xmlElement)
: base(xmlElement)
{
}
public override XmlElement GetIdElement(XmlDocument doc, string id)
{
// check to see if it's a standard ID reference
XmlElement idElem = base.GetIdElement(doc, id);
if (idElem == null)
{
XmlNamespaceManager nsManager = new XmlNamespaceManager(doc.NameTable);
nsManager.AddNamespace("wsu", "http://docs.oasis-open.org/wss/2004/01/oasis-200401-wss-wssecurity-utility-1.0.xsd");
idElem = doc.SelectSingleNode("//*[@wsu:Id=\"" + id + "\"]", nsManager) as XmlElement;
}
return idElem;
}
}