使用SHA256 SignedXml计算机签名

Question

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();

Answer 1

X509Certificate2将私钥从pfx文件加载到不支持SHA-256的Microsoft Enhanced Cryptographic Provider V1.0（提供程序类型1又名Prov_RSA_Full)中。

基于CNG的加密提供程序（在Vista和Server2008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，如rsacryptoServiceProvider，而不是rsacng，因此我们必须克服这些限制。

但是，另一个CryptoAPI提供程序Microsoft增强型RSA和AES加密提供程序（提供程序类型24又名prov_rsa_aes)支持SHA-256。所以如果我们把私钥放入这个提供程序，我们就可以用它签名了。

首先，您必须调整X509Certificate2构造函数，以便通过添加X509KeyStorageFlags.Exportable标志，使密钥能够从X509Certificate2放入的提供程序导出：

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的提供程序创建新的rsacryptoServiceProvider实例：

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

key.FromXmlString(exportedKeyMaterial);

signedXml.SigningKey = key;

现在它能起作用了。

下面是MSDN上提供程序类型及其代码的列表。

下面是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();