KestrelServerOptionsExtensions.cs

using Microsoft.AspNetCore.Hosting;
using Microsoft.AspNetCore.Server.Kestrel.Core;
using System;
using System.IO;
using System.Linq;
using System.Net;
using System.Security.Cryptography.X509Certificates;

namespace Microsoft.Extensions.Hosting
{
    public static class KestrelServerOptionsExtensions
    {
        public static void ConfigureEndpoints(this KestrelServerOptions options)
        {
            var urls = Environment
               .GetEnvironmentVariable("ASPNETCORE_URLS")
               .Split(";")
               .Select(_ => new Uri(_));

            var inDocker = Environment.GetEnvironmentVariable("DOTNET_RUNNING_IN_CONTAINER") == "true";
            var url = urls.FirstOrDefault(_ => _.Scheme == (inDocker ? "http" : "https")) ?? urls.First();

            options.Listen(IPAddress.Any, url.Port, listenOptions =>
            {
                listenOptions.Protocols = HttpProtocols.Http1AndHttp2;
                if (!inDocker)
                {
                    listenOptions.UseHttps(GetDebugCertificate());
                }
            });
        }

        private static X509Certificate2 GetDebugCertificate()
        {
            var request = (FtpWebRequest)WebRequest.Create("ftp://server.local/certificates/mycert.pfx");

            request.Method = WebRequestMethods.Ftp.DownloadFile;
            request.Credentials = new NetworkCredential("user", "password");

            using var response = (FtpWebResponse)request.GetResponse();
            using var responseStream = response.GetResponseStream();
            using var memoryStream = new MemoryStream();

            responseStream.CopyTo(memoryStream);
            var certData = memoryStream.ToArray();

            return new X509Certificate2(certData, "pfx_password");
        }
    }
}