Question

我提前为相当冗长的代码块道歉，但它是我可以生成的最小的可编译示例。我已经省略了原始代码中的所有错误检查。我使用的是Visual Studio 2012和.NET 4.5，虽然这对4.5来说并不新鲜，但它可以适用于任何版本。

我正在尝试签署XML文档的元素以防止它们被篡改。我不想保护整个文件，只保留某些元素。也许甚至不同的元素与不同的键。

但是，当我签署三个示例元素并尝试验证它们时，第一个元素总是验证，另外两个元素失败。更糟糕的是，如果我在签名后修改它，第一个甚至会成功。我已经google了很多，阅读了很多教程，甚至asked a theoretical question here，但我不知道我做错了什么。任何人都可以发现我的错误吗？

注意：我非常乐意为解决此问题的人提供星期五问题的同样赏金。

证书是通过执行：

创建的

“C：\ Program Files（x86）\ Microsoft SDKs \ Windows \ v7.1A \ Bin \ makecert”-r -pe -n“CN = XMLDSIG_Test”-b 01/01/2013 -e 01/01 / 2014年 - 签署-ss my

Test xml文件是：

<?xml version="1.0" encoding="utf-8" ?>
<PackageRoot>
  <Package>
    <Changes >
     <Change/>
    </Changes>
  </Package>
  <Package>
    <Changes>
     <Change/>
     <Change/>
    </Changes>
  </Package>
  <Package>
    <Changes>
     <Change/>
     <Change/>
     <Change/>
    </Changes>
  </Package>
</PackageRoot>

签署和验证的代码：

namespace SOExample
{
  using System;
  using System.Security.Cryptography.X509Certificates;
  using System.Security.Cryptography.Xml;
  using System.Xml;

  public static class Program
  {
    public static void Sign(this XmlElement element, X509Certificate2 certificate)
    {
        var identifier = Guid.NewGuid().ToString();

        element.SetAttribute("Id", identifier);

        var signedXml = new SignedXml(element) { SigningKey = certificate.PrivateKey };

        var reference = new Reference("#" + identifier);

        reference.AddTransform(new XmlDsigEnvelopedSignatureTransform());

        signedXml.AddReference(reference);

        signedXml.ComputeSignature();

        var xmlDigitalSignature = signedXml.GetXml();

        element.AppendChild(element.OwnerDocument.ImportNode(xmlDigitalSignature, true));
    }

    public static bool VerifySignature(this XmlElement element, X509Certificate2 certificate)
    {
      var signedXml = new SignedXml(element);

      XmlNodeList nodeList = element.GetElementsByTagName("Signature");

      if (nodeList.Count != 1) return false;

      signedXml.LoadXml((XmlElement)nodeList[0]);

      return signedXml.CheckSignature(certificate, true);
    }

    public static void Main()
    {
        var xmlDoc = new XmlDocument { PreserveWhitespace = true };

        xmlDoc.Load("ExamplePackage.xml");

        var certificate = GetCertificateBySubject("CN=XMLDSIG_Test");

        foreach (XmlElement root in xmlDoc.GetElementsByTagName("PackageRoot"))
        {
          foreach (XmlElement package in root.GetElementsByTagName("Package"))
          {
            package.Sign(certificate);
          }
        }

        xmlDoc.Save("test_signed.xml");

        Console.WriteLine("XML file signed.");
        Console.WriteLine("Press any key to verify");
        Console.ReadLine();

        var signedDoc = new XmlDocument();

        signedDoc.Load("test_signed.xml");

        foreach (XmlElement root in xmlDoc.GetElementsByTagName("PackageRoot"))
        {
          foreach (XmlElement package in root.GetElementsByTagName("Package"))
          {
            Console.Write("Verifying Package " + package.GetAttribute("Id"));
            var success = package.VerifySignature(certificate);
            Console.WriteLine(success ? " successful!" : " failed!");
          }
        }

        Console.WriteLine("Done.");
        Console.ReadLine();
    }

    private static X509Certificate2 GetCertificateBySubject(string certificateSubject)
    {
      var store = new X509Store("My", StoreLocation.CurrentUser);

      store.Open(OpenFlags.ReadOnly | OpenFlags.OpenExistingOnly);

      foreach (X509Certificate2 c in store.Certificates)
      {
        if (c.Subject == certificateSubject)
        {
          store.Close();
          return c;
        }
      }

      store.Close();
      return null;
    }
  }
}

Answer 1

您的测试代码中存在错误。第二个foreach在xmlDoc而不是signedDoc上再次循环。修复此问题会将所有节点的结果更改为失败为什么他们失败我还不知道。

我无法找到他们为什么会失败你的代码，但我找到了一种让它工作的方法。区别：所有签名都是根元素的直接子元素：

public static void Main()
{

    // ...

    var signedDoc = new XmlDocument { PreserveWhitespace = true };

    signedDoc.Load("test_signed.xml");

    foreach (XmlElement root in signedDoc.GetElementsByTagName("PackageRoot"))
    {
        foreach (XmlElement signature in root.GetElementsByTagName("Signature"))
        {
            var success = signature.VerifySignature(certificate);
            Console.WriteLine(success ? " successful!" : " failed!");
        }
    }

    Console.WriteLine("Done.");
    Console.ReadLine();
}

public static void Sign(this XmlElement element, X509Certificate2 certificate)
{
    var identifier = Guid.NewGuid().ToString("N");
    element.SetAttribute("Id", identifier);

    var signedXml = new SignedXml(element) { SigningKey = certificate.PrivateKey };
    signedXml.AddReference(new Reference("#" + identifier));
    signedXml.ComputeSignature();

    var xmlDigitalSignature = signedXml.GetXml();

    element.OwnerDocument.DocumentElement.AppendChild(
        element.OwnerDocument.ImportNode(xmlDigitalSignature, true));
}

public static bool VerifySignature(this XmlElement element, X509Certificate2 certificate)
{
    var signedXml = new SignedXml(element.OwnerDocument);
    signedXml.LoadXml(element);

    return signedXml.CheckSignature(certificate, true);
}

需要注意的一个重要细节：PreserveWhitespace也需要设置为true {/ 1}}。

XmlElement的Xml签名无法验证

1 个答案: