How can I generate a self-signed cert without using obsolete BouncyCastle 1.7.0 code?

Question

I have the following code which generates a nice self-signed cert, works great, but I'd like to update to the latest BouncyCastle (1.8.1.0) and I'm getting warnings about obsolete usage:

var persistedCertificateFilename = "ClientCertificate.pfx";
if (!string.IsNullOrWhiteSpace(ConfigurationManager.AppSettings["PersistedCertificateFilename"])) { persistedCertificateFilename = ConfigurationManager.AppSettings["PersistedCertificateFilename"].Trim(); }
if (persistCertificateToDisk)
{
    if (File.Exists(persistedCertificateFilename))
    {
        var certBytes = File.ReadAllBytes(persistedCertificateFilename);
                this.clientCertificate = new X509Certificate2(certBytes, (string) null, X509KeyStorageFlags.MachineKeySet | X509KeyStorageFlags.Exportable | X509KeyStorageFlags.PersistKeySet);
    }
}

if (this.clientCertificate == null)
{
    // Initialize the new secure keys
    KeyGenerator keyGenerator = KeyGenerator.Create();
    KeyPair keyPair = keyGenerator.GenerateKeyPair();
    this.privateKey = keyPair.ToEncryptedPrivateKeyString(privateKeySecret);
    this.publicKey = keyPair.ToPublicKeyString();

    // Client certificate permissions
    var certificatePermissions = new ArrayList()
    {
         KeyPurposeID.IdKPCodeSigning,
         KeyPurposeID.IdKPServerAuth,
         KeyPurposeID.IdKPTimeStamping,
         KeyPurposeID.IdKPOcspSigning,
         KeyPurposeID.IdKPClientAuth
    };

    // Initialize the certificate generation
    var certificateGenerator = new X509V3CertificateGenerator();
    BigInteger serialNo = BigInteger.ProbablePrime(128, new Random());
    certificateGenerator.SetSerialNumber(serialNo);
    certificateGenerator.SetSubjectDN(GetLicenseeDN());
    certificateGenerator.SetIssuerDN(GetLicencerDN());
    certificateGenerator.SetNotAfter(DateTime.Now.AddYears(100));
    certificateGenerator.SetNotBefore(DateTime.Now.Subtract(new TimeSpan(7, 0, 0, 0)));
    //ISignatureFactory signatureFactory = new Asn1SignatureFactory("SHA512WITHRSA", keyPair.PrivateKey); // ??
    certificateGenerator.SetSignatureAlgorithm("SHA512withRSA");
    certificateGenerator.AddExtension(X509Extensions.ExtendedKeyUsage, false, new ExtendedKeyUsage(certificatePermissions));
    var subjectKeyIdentifier = new SubjectKeyIdentifier(SubjectPublicKeyInfoFactory.CreateSubjectPublicKeyInfo(keyPair.PublicKey));
    certificateGenerator.AddExtension(X509Extensions.SubjectKeyIdentifier.Id, false, subjectKeyIdentifier);
    certificateGenerator.SetPublicKey(keyPair.PublicKey);
    var result = certificateGenerator.Generate(keyPair.PrivateKey);
    var secure = new SecureString();
    foreach (char c in privateKeySecret)
    {
        secure.AppendChar(c);
    }

    X509KeyStorageFlags flags = X509KeyStorageFlags.MachineKeySet;
    if (persistCertificateToDisk) { flags |= X509KeyStorageFlags.Exportable; flags |= X509KeyStorageFlags.PersistKeySet; }
    this.clientCertificate = new X509Certificate2(Org.BouncyCastle.Security.DotNetUtilities.ToX509Certificate(result).Export(X509ContentType.Cert), secure, flags);

    // This section allows us to use this certificate on Azure (no file access required)
    CspParameters cspParams;
    const int PROVIDER_RSA_FULL = 1;
    cspParams = new CspParameters(PROVIDER_RSA_FULL);
    cspParams.KeyContainerName = new Guid().ToString();
    cspParams.Flags = CspProviderFlags.UseMachineKeyStore;
    cspParams.ProviderName = "Microsoft Strong Cryptographic Provider";
    var rule = new CryptoKeyAccessRule("everyone", CryptoKeyRights.FullControl, AccessControlType.Allow);
    cspParams.CryptoKeySecurity = new CryptoKeySecurity();
    cspParams.CryptoKeySecurity.SetAccessRule(rule);

    // Set the private key
    var tempRcsp = (RSACryptoServiceProvider) Org.BouncyCastle.Security.DotNetUtilities.ToRSA((RsaPrivateCrtKeyParameters) keyPair.PrivateKey);
    var rcsp = new RSACryptoServiceProvider(cspParams);
    rcsp.ImportCspBlob(tempRcsp.ExportCspBlob(true));
    this.clientCertificate.PrivateKey = rcsp;

    if (persistCertificateToDisk)
    {
        if (!File.Exists(persistedCertificateFilename))
        {
            File.WriteAllBytes(persistedCertificateFilename, this.clientCertificate.Export(X509ContentType.Pkcs12, (string) null));
        }
    }
}

Specifically, the warnings are:

'X509V3CertificateGenerator.SetSignatureAlgorithm(string)' is obsolete: 'Not needed if Generate used with an ISignatureFactory'

and

'X509V3CertificateGenerator.Generate(AsymmetricKeyParameter)' is obsolete: 'Use Generate with an ISignatureFactory'

So, my questions are:

1. Do I need to worry about these warnings?
2. If so, what lines change?
3. If I do update this code, is there a performance benefit?

Note: If any one is curious, the reason I'm persisting this to disk is that this code created a cert every time the client was instantiated, and this was particularly harsh due to the min key size being 2048 and the performance of 1.7.0.

Answer 1

I struggled with this for some time, too. I finally have a solution for this. Let's take one of the errors:

'X509V3CertificateGenerator.Generate(AsymmetricKeyParameter)' is obsolete: 'Use Generate with an ISignatureFactory'

You are basically using (i was doing the same thing) the Generate method like this:

var certificate = certificateGenerator.Generate(issuerCertificate.PrivateKey, random);

where certificateGenerator is instance of class CertificateContainer Error says that: 'Use Generate with an ISignatureFactory'
So for this let us create first an instance to ISignatureFactory.

ISignatureFactory signatureFactory = new Asn1SignatureFactory("SHA512WITHRSA", issuerKeyPair.Private, random);

And for this to work correctly before this you should also declare the followings:

var randomGenerator = new CryptoApiRandomGenerator();
var random = new SecureRandom(randomGenerator);
AsymmetricCipherKeyPair subjectKeyPair = default(AsymmetricCipherKeyPair);
var keyGenerationParameters = new KeyGenerationParameters(random, keyStrength);

keyPairGenerator.Init(keyGenerationParameters);
subjectKeyPair = keyPairGenerator.GenerateKeyPair();
AsymmetricCipherKeyPair issuerKeyPair = subjectKeyPair;

And now after these changes, change the method Generate from:

var certificate = certificateGenerator.Generate(issuerCertificate.PrivateKey, random);

to:

var certificate = certificateGenerator.Generate(signatureFactory);

I hope it helps.