SslCertificateHelper.cs

public class SslCertificateHelper
{
    [SupportedOSPlatform("windows")]
    public static X509Certificate2? GetX509Certificate2(string subject = "CN=localhost")
    {
        X509Certificate2? certificate = null;
        using var certStore = new X509Store(StoreName.My, StoreLocation.LocalMachine);
        certStore.Open(OpenFlags.ReadWrite | OpenFlags.OpenExistingOnly);
        var certs = certStore.Certificates.Find(X509FindType.FindBySubjectDistinguishedName, subject, false);
        if (certs.Count > 0)
        {
            certificate = certs[0];
        }
        else
        {
            certificate = CreateSelfSignedCertificate(subject);
            if (certificate != null)
                certStore.Add(certificate);
        }
        return certificate;
    }

    [SupportedOSPlatform("windows")]
    private static X509Certificate2? CreateSelfSignedCertificate(string subject = "CN=localhost")
    {
        using var rsa = new RSACryptoServiceProvider(4096, new CspParameters(24, "Microsoft Enhanced RSA and AES Cryptographic Provider", Guid.NewGuid().ToString()));
        var req = new CertificateRequest(subject, rsa, HashAlgorithmName.SHA256, RSASignaturePadding.Pkcs1);
        var cert = req.CreateSelfSigned(DateTimeOffset.Now, DateTimeOffset.Now.AddYears(1));
        var password = Guid.NewGuid().ToString();
        var rsaCert = new X509Certificate2(cert.Export(X509ContentType.Pfx, password), password, X509KeyStorageFlags.MachineKeySet | X509KeyStorageFlags.PersistKeySet | X509KeyStorageFlags.Exportable);
        return rsaCert;
    }
}