使用 SignedXml 类添加基于 Id 属性的引用时出现“格式错误的引用元素"

问题描述

当存在命名空间前缀时，无法通过 Id 属性对元素进行签名:

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() 会在此处失败并显示格式错误的参考元素"，这应该怎么做?

ComputeSignature() will fail here with 'Malformed Reference Element' how should this be done?

推荐答案

我们使用的方法是子类化 System.Security.Cryptography.Xml.SignedXml 类...

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;
    }
}

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