2

对于相当长的代码块,我提前道歉,但这是我可以生成的最小的可编译示例。我已经从原始代码中省略了所有错误检查。我正在使用 Visual Studio 2012 和 .NET 4.5,虽然这对 4.5 来说并不是什么新鲜事,但它应该适用于任何版本。

我正在尝试签署 XML 文档的元素以保护它们不被篡改。我不想保护整个文档,而只想保护某些元素。甚至可能具有不同键的不同元素。

但是,当我签署三个示例元素并尝试验证它们时,第一个总是验证,另外两个失败。更糟糕的是,如果我在签名后修改它,第一个甚至会成功。我搜索了很多,阅读了很多教程,甚至在这里问了一个理论问题,但我不知道我做错了什么。有人能看出我的错误吗?

注意:我很乐意为解决此问题的任何人提供与周五问题相同的赏金。

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 -sky签名 -ss 我的

测试 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>

签名和验证的代码:

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;
    }
  }
}
4

1 回答 1

3

您的测试代码中有错误。第二个 foreach 再次循环xmlDoc而不是signedDoc. 修复此问题会将所有节点的结果更改为失败。
他们为什么失败我还不知道。


我不知道为什么他们的代码会失败,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truefor signedDoc

于 2013-05-13T10:14:58.230 回答