ASP.NET Core 3.0 app not working on Windows Server 2012 R2 due to ERR_HTTP2_INADEQUATE_TRANSPORT_SECURITY

Question

I took a working ASP.NET Core 2.2 app, upgraded it to 3.0 and suddenly the app no longer works in Windows Server 2012. It comes up with the following:

ERR_HTTP2_INADEQUATE_TRANSPORT_SECURITY

Chrome:

Firefox:

It seems that before I had to opt into HTTP/2 and now its the default along with HTTP1.1. There is a post here https://github.com/aspnet/AspNetCore/issues/14350 but that is totally confusing with no real solution.

I have tried all sorts of enabling / disabling insecure protocols but to no avail. Such as https://www.admin-enclave.com/de/articles-by-year/11-data-articles/website_articles/articles/exchange_articles/405-resolved-error-err_spdy_inadequate_transport_security-when-using-google-chome-and-owa.html

Works fine on Windows 10 due to what I assume more better protocol suite. But in Fiddler I checked and the only difference when negotiating with Kestrel is:

Windows Server 2012 R2:

[0A0A]  Unrecognized cipher - See http://www.iana.org/assignments/tls-parameters/
[1301]  Unrecognized cipher - See http://www.iana.org/assignments/tls-parameters/
[1302]  Unrecognized cipher - See http://www.iana.org/assignments/tls-parameters/
[1303]  Unrecognized cipher - See http://www.iana.org/assignments/tls-parameters/
[C02B]  TLS_ECDHE_ECDSA_WITH_AES_128_GCM_SHA256
[C02F]  Unrecognized cipher - See http://www.iana.org/assignments/tls-parameters/
[C02C]  TLS_ECDHE_ECDSA_WITH_AES_256_GCM_SHA384
[C030]  Unrecognized cipher - See http://www.iana.org/assignments/tls-parameters/
[CCA9]  Unrecognized cipher - See http://www.iana.org/assignments/tls-parameters/
[CCA8]  Unrecognized cipher - See http://www.iana.org/assignments/tls-parameters/
[C013]  TLS1_CK_ECDHE_RSA_WITH_AES_128_CBC_SHA
[C014]  TLS1_CK_ECDHE_RSA_WITH_AES_256_CBC_SHA
[009C]  Unrecognized cipher - See http://www.iana.org/assignments/tls-parameters/
[009D]  Unrecognized cipher - See http://www.iana.org/assignments/tls-parameters/
[002F]  TLS_RSA_AES_128_SHA
[0035]  TLS_RSA_AES_256_SHA
[000A]  SSL_RSA_WITH_3DES_EDE_SHA

Windows 10:

[3A3A]  Unrecognized cipher - See http://www.iana.org/assignments/tls-parameters/
[1301]  Unrecognized cipher - See http://www.iana.org/assignments/tls-parameters/
[1302]  Unrecognized cipher - See http://www.iana.org/assignments/tls-parameters/
[1303]  Unrecognized cipher - See http://www.iana.org/assignments/tls-parameters/
[C02B]  TLS_ECDHE_ECDSA_WITH_AES_128_GCM_SHA256
[C02F]  Unrecognized cipher - See http://www.iana.org/assignments/tls-parameters/
[C02C]  TLS_ECDHE_ECDSA_WITH_AES_256_GCM_SHA384
[C030]  Unrecognized cipher - See http://www.iana.org/assignments/tls-parameters/
[CCA9]  Unrecognized cipher - See http://www.iana.org/assignments/tls-parameters/
[CCA8]  Unrecognized cipher - See http://www.iana.org/assignments/tls-parameters/
[C013]  TLS1_CK_ECDHE_RSA_WITH_AES_128_CBC_SHA
[C014]  TLS1_CK_ECDHE_RSA_WITH_AES_256_CBC_SHA
[009C]  Unrecognized cipher - See http://www.iana.org/assignments/tls-parameters/
[009D]  Unrecognized cipher - See http://www.iana.org/assignments/tls-parameters/
[002F]  TLS_RSA_AES_128_SHA
[0035]  TLS_RSA_AES_256_SHA
[000A]  SSL_RSA_WITH_3DES_EDE_SHA

The top line is different, but that is all. Not sure what is it, it is some GREASE value.

Program.cs:

    public static IWebHostBuilder CreateWebHostBuilder(string[] args) =>
      WebHost.CreateDefaultBuilder(args)
      .UseKestrel(opts => {
        opts.ListenAnyIP(5000);
        opts.ListenAnyIP(5001, listenOpts => {
          listenOpts.UseHttps(new HttpsConnectionAdapterOptions {
            ServerCertificate = new X509Certificate2("certificate-server.pfx", "...")
          });
        });
        opts.Limits.MaxRequestBodySize = null;
      })
      .UseContentRoot(Directory.GetCurrentDirectory())
      .UseStartup<Startup>();
  }

Update

Seems I am on the right track thanks to @chris-pratt. Changing the certificate cipher to ECDSA_nistP256 make the web application work. But unfortunately I am using the cert to also sign the JWT tokens, and now that is broken with:

System.NotSupportedException: The certificate key algorithm is not supported. at System.Security.Cryptography.X509Certificates.PublicKey.get_Key()

The signing code is:

  var privateKey = new X509SecurityKey(new X509Certificate2("certificate-server.pfx", "..."));
  var token = new JwtSecurityToken(
    issuer: "Sentry",
    claims: claims,
    notBefore: DateTime.Now,
    expires: DateTime.Now.AddDays(1),
    signingCredentials: new SigningCredentials(privateKey, SecurityAlgorithms.RsaSha256Signature));

  return new JwtSecurityTokenHandler().WriteToken(token);

I tried changing the SecurityAlgorithms enum but did not get any success.

Answer 1

Windows 2012 R2 does not support the cypher suites that are allowed for HTTP/2. I assume that starting with Core 3.0 the HTTP/2 protocol is enabled by default. I solved my problem by disabling HTTP/2 in kestrel as follows:

public static IHostBuilder CreateHostBuilder(string[] args) =>

  Host.CreateDefaultBuilder(args).ConfigureWebHostDefaults(webBuilder =>
  {
      webBuilder.UseKestrel(options =>
      {
        options.Listen(System.Net.IPAddress.Parse(DomainIp), 80);
        options.Listen(System.Net.IPAddress.Parse(DomainIp), 443, l =>
        {
          l.UseHttps(
            DomainCertificateFile,
            DomainCertificatePassword);
          l.Protocols = Microsoft.AspNetCore.Server.Kestrel.Core.HttpProtocols.Http1;
        });
      });
      webBuilder.UseStaticWebAssets();
      webBuilder.UseStartup<Startup>();
   });