c# - SignedXml 使用 SHA256 计算签名

Question

我正在尝试使用 SHA256 对 XML 文档进行数字签名。

我正在尝试使用 Security.Cryptography.dll为此。

这是我的代码-

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

X509Certificate2 cert = new X509Certificate2(@"location of pks file", "password");
XmlDocument doc = new XmlDocument();
doc.PreserveWhitespace = true;
doc.Load(@"input.xml");

SignedXml signedXml = new SignedXml(doc);
signedXml.SigningKey = cert.PrivateKey;
signedXml.SignedInfo.SignatureMethod = "http://www.w3.org/2001/04/xmldsig-more#rsa-sha256";

// 
// Add a signing reference, the uri is empty and so the whole document 
// is signed. 
Reference reference = new Reference();
reference.AddTransform(new XmlDsigEnvelopedSignatureTransform());
reference.AddTransform(new XmlDsigExcC14NTransform());
reference.Uri = "";
signedXml.AddReference(reference);

// 
// Add the certificate as key info, because of this the certificate 
// with the public key will be added in the signature part. 
KeyInfo keyInfo = new KeyInfo();
keyInfo.AddClause(new KeyInfoX509Data(cert));
signedXml.KeyInfo = keyInfo;
// Generate the signature. 
signedXml.ComputeSignature();

但我收到“指定的算法无效”。 signedXml.ComputeSignature(); 处出错。谁能告诉我我做错了什么？

Answer 1

X509Certificate2 将私钥从 pfx 文件加载到 Microsoft Enhanced Cryptographic Provider v1.0(提供程序类型 1 又名 PROV_RSA_FULL) 不支持 SHA-256。

基于 CNG 的加密提供程序(在 Vista 和 Server 2008 中引入)比基于 CryptoAPI 的提供程序支持更多的算法，但是 .NET 代码似乎仍然可以使用基于 CryptoAPI 的类，例如 RSACryptoServiceProvider 而不是 RSACng，所以我们必须解决这些限制。

但是，另一个 CryptoAPI 提供程序 Microsoft Enhanced RSA and AES Cryptographic Provider(提供程序类型 24 a.k.a. PROV_RSA_AES)确实支持 SHA-256。因此，如果我们将私钥输入该提供程序，我们就可以使用它进行签名。

首先，您必须调整您的 X509Certificate2 构造函数，使 key 能够从 X509Certificate2 通过添加 X509KeyStorageFlags.Exportable 标志:

X509Certificate2 cert = new X509Certificate2(
    @"location of pks file", "password",
    X509KeyStorageFlags.Exportable);

并导出私钥:

var exportedKeyMaterial = cert.PrivateKey.ToXmlString(
    /* includePrivateParameters = */ true);

然后为支持 SHA-256 的提供商创建一个新的 RSACryptoServiceProvider 实例:

var key = new RSACryptoServiceProvider(
    new CspParameters(24 /* PROV_RSA_AES */));
key.PersistKeyInCsp = false;

并将私钥导入其中:

key.FromXmlString(exportedKeyMaterial);

创建SignedXml 实例后，告诉它使用key 而不是cert.PrivateKey:

signedXml.SigningKey = key;

它现在可以工作了。

这是 list of provider types and their codes在 MSDN 上。

这是您的示例的完整调整代码:

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

X509Certificate2 cert = new X509Certificate2(@"location of pks file", "password", X509KeyStorageFlags.Exportable);

// Export private key from cert.PrivateKey and import into a PROV_RSA_AES provider:
var exportedKeyMaterial = cert.PrivateKey.ToXmlString( /* includePrivateParameters = */ true);
var key = new RSACryptoServiceProvider(new CspParameters(24 /* PROV_RSA_AES */));
key.PersistKeyInCsp = false;
key.FromXmlString(exportedKeyMaterial);

XmlDocument doc = new XmlDocument();
doc.PreserveWhitespace = true;
doc.Load(@"input.xml");

SignedXml signedXml = new SignedXml(doc);
signedXml.SigningKey = key;
signedXml.SignedInfo.SignatureMethod = "http://www.w3.org/2001/04/xmldsig-more#rsa-sha256";

// 
// Add a signing reference, the uri is empty and so the whole document 
// is signed. 
Reference reference = new Reference();
reference.AddTransform(new XmlDsigEnvelopedSignatureTransform());
reference.AddTransform(new XmlDsigExcC14NTransform());
reference.Uri = "";
signedXml.AddReference(reference);

// 
// Add the certificate as key info, because of this the certificate 
// with the public key will be added in the signature part. 
KeyInfo keyInfo = new KeyInfo();
keyInfo.AddClause(new KeyInfoX509Data(cert));
signedXml.KeyInfo = keyInfo;
// Generate the signature. 
signedXml.ComputeSignature();