How to create a valid, self-signed X509Certificate2 programmatically, not loading from file in .NET Core

Question

What I currently do is that I use OpenSSL to generate PFX file. This is causing an unwanted dependency, especially for Windows users. So I found some examples on how to crea

Answer 1

I found this other SO question that put me on the right track. Certificates API was added to .Net Core on 2.0 version. I have a function like the next one to create self signed certificates that I later import into My store to use them on IIS.

    private X509Certificate2 buildSelfSignedServerCertificate()
    {
        SubjectAlternativeNameBuilder sanBuilder = new SubjectAlternativeNameBuilder();
        sanBuilder.AddIpAddress(IPAddress.Loopback);
        sanBuilder.AddIpAddress(IPAddress.IPv6Loopback);
        sanBuilder.AddDnsName("localhost");
        sanBuilder.AddDnsName(Environment.MachineName);

        X500DistinguishedName distinguishedName = new X500DistinguishedName($"CN={CertificateName}");

        using (RSA rsa = RSA.Create(2048))
        {
            var request = new CertificateRequest(distinguishedName, rsa, HashAlgorithmName.SHA256,RSASignaturePadding.Pkcs1);

            request.CertificateExtensions.Add(
                new X509KeyUsageExtension(X509KeyUsageFlags.DataEncipherment | X509KeyUsageFlags.KeyEncipherment | X509KeyUsageFlags.DigitalSignature , false));


            request.CertificateExtensions.Add(
               new X509EnhancedKeyUsageExtension(
                   new OidCollection { new Oid("1.3.6.1.5.5.7.3.1") }, false));

            request.CertificateExtensions.Add(sanBuilder.Build());

            var certificate= request.CreateSelfSigned(new DateTimeOffset(DateTime.UtcNow.AddDays(-1)), new DateTimeOffset(DateTime.UtcNow.AddDays(3650)));
            certificate.FriendlyName = CertificateName;

            return new X509Certificate2(certificate.Export(X509ContentType.Pfx, "WeNeedASaf3rPassword"), "WeNeedASaf3rPassword", X509KeyStorageFlags.MachineKeySet);
        }
    }

If you want the pfx, the Export function on X509Certificate2 should do the trick. It returns a byte array with the raw pfx data.