SSO SAML 的签名 XML 签名验证（使用 sha256）

Question

在 Windows 2003 服务器上使用 VS 2008 和 .Net Framework 3.5。

为了安全起见，我们使用 SAML 实施了 SSO。我们在服务提供商端工作，我们验证从客户端系统生成的签名 XML SAML Assertuib 令牌。 到目前为止，我们遇到的任何签名文档都使用签名算法“rsa-sha1”，但现在我们有新客户发送签名算法为“rsa-sha256”的文件，问题就在这里。

public static string VerifySignature()
{
    if (m_xmlDoc == null)
        return "Could not load XMLDocument ";

    try
    {
        XmlNamespaceManager nsm = new XmlNamespaceManager(new NameTable());
        nsm.AddNamespace("dsig", SignedXml.XmlDsigNamespaceUrl);
        XmlElement sigElt = (XmlElement)m_xmlDoc.SelectSingleNode(
            "//dsig:Signature", nsm);

        // Load the signature for verification
        SignedXml sig = new SignedXml(m_xmlDoc);
        sig.LoadXml(sigElt);

        if (!sig.CheckSignature())
            return "Invalid Signature";
    }
    catch (Exception ex)
    {
        return ex.Message;
    }
    return string.Empty;
}

现在，当我为这个新客户尝试相同的代码（使用签名算法 rsa-sha256h）时 - 这不起作用，我收到错误“无法为提供的签名算法创建签名描述。”

最近2-3天浏览了很多博客和文章，我才知道SignedXml不支持sha256。美好的。但是接下来呢。在某处提到使用 WIF，我也检查并尝试了this。

我也在尝试使用 RSAPKCS1SignatureDeformatter 的 VerifySignature 方法。但不太确定要传递的两个参数是什么。

Answer 1

Dotnet 4.6.2+ 内置了较新的 sha 哈希。对于 dotnet 4+，要访问 rsa-sha512、rsa-sha384 和 rsa-sha256，您应该在某处包含此代码。

/// <summary>Declare the signature type for rsa-sha512</summary>
public class RsaPkCs1Sha512SignatureDescription : SignatureDescription
{
    public RsaPkCs1Sha512SignatureDescription()
    {
        KeyAlgorithm = typeof(RSACryptoServiceProvider).FullName;
        DigestAlgorithm = typeof(SHA512CryptoServiceProvider).FullName;
        FormatterAlgorithm = typeof(RSAPKCS1SignatureFormatter).FullName;
        DeformatterAlgorithm = typeof(RSAPKCS1SignatureDeformatter).FullName;
    }

    public override AsymmetricSignatureDeformatter CreateDeformatter(AsymmetricAlgorithm key)
    {
        var sigProcessor = (AsymmetricSignatureDeformatter)CryptoConfig.CreateFromName(DeformatterAlgorithm);
        sigProcessor.SetKey(key);
        sigProcessor.SetHashAlgorithm("SHA512");
        return sigProcessor;
    }

    public override AsymmetricSignatureFormatter CreateFormatter(AsymmetricAlgorithm key)
    {
        var sigProcessor =
            (AsymmetricSignatureFormatter)CryptoConfig.CreateFromName(FormatterAlgorithm);
        sigProcessor.SetKey(key);
        sigProcessor.SetHashAlgorithm("SHA512");
        return sigProcessor;
    }
}

/// <summary>Declare the signature type for rsa-sha384</summary>
public class RsaPkCs1Sha384SignatureDescription : SignatureDescription {
    public RsaPkCs1Sha384SignatureDescription()
    {
        KeyAlgorithm = typeof(RSACryptoServiceProvider).FullName;
        DigestAlgorithm = typeof(SHA384CryptoServiceProvider).FullName;
        FormatterAlgorithm = typeof(RSAPKCS1SignatureFormatter).FullName;
        DeformatterAlgorithm = typeof(RSAPKCS1SignatureDeformatter).FullName;
    }

    public override AsymmetricSignatureDeformatter CreateDeformatter(AsymmetricAlgorithm key)
    {
        var sigProcessor = (AsymmetricSignatureDeformatter) CryptoConfig.CreateFromName(DeformatterAlgorithm);
        sigProcessor.SetKey(key);
        sigProcessor.SetHashAlgorithm("SHA384");
        return sigProcessor;
    }

    public override AsymmetricSignatureFormatter CreateFormatter(AsymmetricAlgorithm key)
    {
        var sigProcessor =
            (AsymmetricSignatureFormatter)CryptoConfig.CreateFromName(FormatterAlgorithm);
        sigProcessor.SetKey(key);
        sigProcessor.SetHashAlgorithm("SHA384");
        return sigProcessor;
    }
}

/// <summary>Declare the signature type for rsa-sha256</summary>
public class RsaPkCs1Sha256SignatureDescription : SignatureDescription
{
    public RsaPkCs1Sha256SignatureDescription()
    {
        KeyAlgorithm = typeof(RSACryptoServiceProvider).FullName;
        DigestAlgorithm = typeof(SHA256CryptoServiceProvider).FullName;
        FormatterAlgorithm = typeof(RSAPKCS1SignatureFormatter).FullName;
        DeformatterAlgorithm = typeof(RSAPKCS1SignatureDeformatter).FullName;
    }

    public override AsymmetricSignatureDeformatter CreateDeformatter(AsymmetricAlgorithm key)
    {
        var sigProcessor =
            (AsymmetricSignatureDeformatter) CryptoConfig.CreateFromName(DeformatterAlgorithm);
        sigProcessor.SetKey(key);
        sigProcessor.SetHashAlgorithm("SHA256");
        return sigProcessor;
    }

    public override AsymmetricSignatureFormatter CreateFormatter(AsymmetricAlgorithm key)
    {
        var sigProcessor =
            (AsymmetricSignatureFormatter)CryptoConfig.CreateFromName(FormatterAlgorithm);
        sigProcessor.SetKey(key);
        sigProcessor.SetHashAlgorithm("SHA256");
        return sigProcessor;
    }
}

然后，您应该通过调用这样的代码来激活这些 sig 描述。您只需调用一次，因此您可以根据需要从静态构造函数中调用它。

    CryptoConfig.AddAlgorithm(typeof(RsaPkCs1Sha512SignatureDescription),
        "http://www.w3.org/2001/04/xmldsig-more#rsa-sha512");
    CryptoConfig.AddAlgorithm(typeof(RsaPkCs1Sha384SignatureDescription),
        "http://www.w3.org/2001/04/xmldsig-more#rsa-sha384");
    CryptoConfig.AddAlgorithm(typeof(RsaPkCs1Sha256SignatureDescription),
        "http://www.w3.org/2001/04/xmldsig-more#rsa-sha256");

在 SO 上向 Microsoft's Carlos Lopez 和 BitSchupster 和 Andrew 致敬。

Answer 2

对于 .net 4 及更早版本， 我发现从http://clrsecurity.codeplex.com/ 添加 Security.Cryptography 后，以下工作有效

（注意X509CertificateFinder是我自己的，通过指纹在证书存储中查找签名证书）

        /// <summary>
        /// Validate an XmlDocuments signature
        /// </summary>
        /// <param name="xnlDoc"> The saml response with the signature elemenet to validate </param>
        /// <returns> True if signature can be validated with certificate </returns>
        public bool ValidateX509CertificateSignature(XmlDocument xnlDoc)
        {
            XmlNodeList XMLSignatures = xnlDoc.GetElementsByTagName("Signature", "http://www.w3.org/2000/09/xmldsig#");

            // Checking If the Response or the Assertion has been signed once and only once.
            if (XMLSignatures.Count != 1) return false;

            var signedXmlDoc = new SignedXml(xnlDoc);
            signedXmlDoc.LoadXml((XmlElement)XMLSignatures[0]);

            var certFinder = new X509CertificateFinder();
            var foundCert = certFinder.GetSignatureCertificate();

            CryptoConfig.AddAlgorithm(typeof(RSAPKCS1SHA256SignatureDescription), "http://www.w3.org/2001/04/xmldsig-more#rsa-sha256");
            return signedXmlDoc.CheckSignature(foundCert,false);
        }

Answer 3

这符合“简单”的条件，但可能不是“解决方案”:) 对于我们遇到的少数客户，我们已要求他们更改其 IdP 以使用 SHA-1 进行签名。他们能够改变它，当他们这样做时，它就会起作用。

不是技术解决方案，但它已经在“现场”工作，所以我想我会提到它。

Answer 4

只需将其更新至 .NET Framework 4.6.01590 或更高版本，即可支持最高 SHA-512，无需任何代码更改。