如何使证书中的私钥不可导出C#答案

【问题标题】：How to make priv key in certificate not exportable C#如何使证书中的私钥不可导出C#
【发布时间】：2017-05-07 23:16:42
【问题描述】：

因此，您将在下面找到我的代码，该代码使用其中的私钥创建自签名证书。它存储在用户存储中。现在当我使用 mmc 工具时，我可以从证书中导出私钥吗？我认为这是您在创建证书时必须明确添加的标志？

所以我想知道的是，如何更改此代码，使私钥不再可通过 mmc 导出。

代码：

public static X509Certificate2 GenerateSelfSignedCertificateNoCA(string subjectName, string issuerName)
{
        const int keyStrength = 2048;

        // Generating Random Numbers
        CryptoApiRandomGenerator randomGenerator = new CryptoApiRandomGenerator();
        SecureRandom random = new SecureRandom(randomGenerator);

        // The Certificate Generator
        X509V3CertificateGenerator certificateGenerator = new X509V3CertificateGenerator();

        // Serial Number
        BigInteger serialNumber = BigIntegers.CreateRandomInRange(BigInteger.One, BigInteger.ValueOf(Int64.MaxValue), random);
        certificateGenerator.SetSerialNumber(serialNumber);

        // Signature Algorithm
        const string signatureAlgorithm = "SHA256WithRSA";
        certificateGenerator.SetSignatureAlgorithm(signatureAlgorithm);

        // Issuer and Subject Name
        X509Name subjectDN = new X509Name(subjectName);
        X509Name issuerDN = new X509Name(issuerName);
        certificateGenerator.SetIssuerDN(issuerDN);
        certificateGenerator.SetSubjectDN(subjectDN);

        // Valid For
        DateTime notBefore = DateTime.UtcNow.Date;
        DateTime notAfter = notBefore.AddYears(2);

        certificateGenerator.SetNotBefore(notBefore);
        certificateGenerator.SetNotAfter(notAfter);

        // Subject Public Key
        AsymmetricCipherKeyPair subjectKeyPair;
        var keyGenerationParameters = new KeyGenerationParameters(random, keyStrength);
        var keyPairGenerator = new RsaKeyPairGenerator();
        keyPairGenerator.Init(keyGenerationParameters);
        subjectKeyPair = keyPairGenerator.GenerateKeyPair();

        certificateGenerator.SetPublicKey(subjectKeyPair.Public);

        // Generating the Certificate
        AsymmetricCipherKeyPair issuerKeyPair = subjectKeyPair;

        // selfsign certificate
        Org.BouncyCastle.X509.X509Certificate certificate = certificateGenerator.Generate(subjectKeyPair.Private, random);

        // correcponding private key
        PrivateKeyInfo info = PrivateKeyInfoFactory.CreatePrivateKeyInfo(subjectKeyPair.Private);

        // merge into X509Certificate2
        X509Certificate2 x509 = new System.Security.Cryptography.X509Certificates.X509Certificate2(certificate.GetEncoded());


        Asn1Sequence seq = (Asn1Sequence)Asn1Object.FromByteArray(info.PrivateKey.GetDerEncoded());
        if (seq.Count != 9)
        {
            //throw new PemException("malformed sequence in RSA private key");
        }

        RsaPrivateKeyStructure rsa = new RsaPrivateKeyStructure(seq);
        RsaPrivateCrtKeyParameters rsaparams = new RsaPrivateCrtKeyParameters(
            rsa.Modulus, rsa.PublicExponent, rsa.PrivateExponent, rsa.Prime1, rsa.Prime2, rsa.Exponent1, rsa.Exponent2, rsa.Coefficient);

        x509.PrivateKey = DotNetUtilities.ToRSA(rsaparams);
        // Console.Write("Private key: " + x509.PrivateKey);
        return x509;

}

【问题讨论】：

X509KeyStorageFlags.Exportable msdn.microsoft.com/en-us/library/…
是的，我知道它就在那里，只有在你想明确地将私钥设置为可导出时才使用它。不是反过来。如您所见，我没有使用它。
一切只依赖于软件的东西都很容易提取，即使它不能导出，你也可以等待你的程序使用它，然后内存转储它，或者其他什么。根据我的经验，如果您想安全起见，请使用 codemeter 加上 codeencryption/obfuscation 之类的东西。它并非不可破解，但几乎在所有情况下都不值得付出努力。
是的，我很痛苦地意识到这一点，问题是我们的客户很难按下“使其不可导出”部分。因此，我们尽力满足并给他们一种安全感。
我将尝试根据这篇文章重新实现创建自签名证书的方法：stackoverflow.com/questions/13806299/… - 有了这个库，我可以明确设置“不可导出”

标签： c# x509certificate x509certificate2

【解决方案1】：

DotNetUtilities.ToRSA 将始终将私钥设置为可导出。为了防止这种情况，有另一种方法可以将您的 BouncyCastle 密钥转换为 .NET X509Certificate2，如 from here

    public X509Certificate2 GenerateSelfSignedCertificateNoCA(string subjectName, string issuerName)
    {
        const int keyStrength = 2048;

        // Generating Random Numbers
        CryptoApiRandomGenerator randomGenerator = new CryptoApiRandomGenerator();
        SecureRandom random = new SecureRandom(randomGenerator);

        // The Certificate Generator
        X509V3CertificateGenerator certificateGenerator = new X509V3CertificateGenerator();

        // Serial Number
        BigInteger serialNumber = BigIntegers.CreateRandomInRange(BigInteger.One, BigInteger.ValueOf(Int64.MaxValue), random);
        certificateGenerator.SetSerialNumber(serialNumber);

        // Signature Algorithm
        const string signatureAlgorithm = "SHA256WithRSA";
        certificateGenerator.SetSignatureAlgorithm(signatureAlgorithm);

        // Issuer and Subject Name
        X509Name subjectDN = new X509Name(subjectName);
        X509Name issuerDN = new X509Name(issuerName);
        certificateGenerator.SetIssuerDN(issuerDN);
        certificateGenerator.SetSubjectDN(subjectDN);

        // Valid For
        DateTime notBefore = DateTime.UtcNow.Date;
        DateTime notAfter = notBefore.AddYears(2);

        certificateGenerator.SetNotBefore(notBefore);
        certificateGenerator.SetNotAfter(notAfter);

        // Subject Public Key
        AsymmetricCipherKeyPair subjectKeyPair;
        var keyGenerationParameters = new KeyGenerationParameters(random, keyStrength);
        var keyPairGenerator = new RsaKeyPairGenerator();
        keyPairGenerator.Init(keyGenerationParameters);
        subjectKeyPair = keyPairGenerator.GenerateKeyPair();

        certificateGenerator.SetPublicKey(subjectKeyPair.Public);

        // Generating the Certificate
        AsymmetricCipherKeyPair issuerKeyPair = subjectKeyPair;

        // selfsign certificate
        Org.BouncyCastle.X509.X509Certificate certificate = certificateGenerator.Generate(subjectKeyPair.Private, random);

        //import into store
        var certificateEntry = new X509CertificateEntry(certificate);
        string friendlyName = certificate.SubjectDN.ToString();
        var store = new Pkcs12Store();
        store.SetCertificateEntry(friendlyName, certificateEntry);
        store.SetKeyEntry(friendlyName, new AsymmetricKeyEntry(subjectKeyPair.Private), new[] {certificateEntry});

        //save to memorystream
        var password = "password";
        var stream = new MemoryStream();
        store.Save(stream, password.ToCharArray(), random);

        // convert into X509Certificate2
        X509Certificate2 x509 = new System.Security.Cryptography.X509Certificates.X509Certificate2(stream.ToArray(), password, X509KeyStorageFlags.UserKeySet);

        return x509;
    }

私钥现在被标记为 Exportable=false。

【讨论】：

【解决方案2】：

PKCS12/PFX 无法做到这一点。

您不应将不可导出的私钥视为“牢不可破”或“难以破解”的安全预防措施。有些实用程序也会导出不可导出的私钥。

如果您需要保护私钥，我建议您使用加密令牌/智能卡或硬件安全模块。

【讨论】：