IDX20803: Unable to obtain configuration from: /.well-known/openid-configuration

Question

I am trying to connect my api service (.net core) to identity (.net core + identityserver4) and I am getting this error message

System.InvalidOperationException: IDX20803: Unable to obtain configuration from...

that's because the identity discovery endpoint expects an additional custom header. I created custom IDocumentRetriever

public class AppHttpDocumentRetriever : HttpDocumentRetriever, IDocumentRetriever

and registered it in Startup

services.AddTransient<IDocumentRetriever, AppHttpDocumentRetriever>();

but it doesn't inject in ConfigurationManager. I don't want to add this custom header to all outbound requests via custom middleware. Are there other approaches to adding a custom header to request to the discovery endpoint?

Answer 1

All requests made in the background are performed using HttpClient. What you can do is inject a HttpMessageHandler into the HttpClient.

To set your own handler, you can set the BackchannelHttpHandler property.

like:

.AddOpenIdConnect(options =>
   {
        options.BackchannelHttpHandler = new BackChannelListener();
         ....
   }

A sample handler that logs the requests is shown below and from that I am sure you can figure out how to add a custom header on the outgoing request.

namespace Infrastructure
{
    /// <summary>
    /// Backchannel listener, that will log requests made to our IdentityServer 
    /// Source: IdentityServer in Production training class https://www.tn-data.se
    /// </summary>
    public class BackChannelListener : DelegatingHandler
    {
        public BackChannelListener() : base(new HttpClientHandler())
        {
            Console.WriteLine();
        }

        protected override Task<HttpResponseMessage> SendAsync(HttpRequestMessage request, CancellationToken cancellationToken)
        {
            Console.WriteLine("BackChannelListener");
            Console.WriteLine("@@@@ SendASync: " + request.RequestUri);

            var sw = new Stopwatch();
            sw.Start();

            var result = base.SendAsync(request, cancellationToken);

            result.ContinueWith(t =>
            {
                sw.Stop();

                Console.WriteLine("@@@@ success: " + result.IsFaulted);
                Console.WriteLine("@@@@ loadtime: " + sw.ElapsedMilliseconds.ToString());
                Console.WriteLine("@@@@ url: " + request.RequestUri);

                Serilog.Log.Logger.ForContext("SourceContext", "BackChannelListener")
                                  .ForContext("url", request.RequestUri)
                                  .ForContext("loadtime", sw.ElapsedMilliseconds.ToString() + " ms")
                                  .ForContext("success", result.IsCompletedSuccessfully)
                                  .Information("Loading IdentityServer configuration");
            });

            return result;
        }
    }
}