Windows and Anonymous Authentication in .Net Core 2.0

Question

I'm trying to mix Windows and Anonymous authentication in a .Net Core 2.0 empty web app. I would like to avoid the [Authorize] attribute as I do not want to use Mvc or controllers.

My setup is as follows:

1. I created an empty .Net Core 2.0 web application

2. I went to project properties -> Debug -> Checked "Enable Windows Authentication" and disabled "Enable Anonymous Authentication". Now "windowsAuthentication": true and "anonymousAuthentication": false appeared in my launchSettings.json under "IIS".

3. Inside Startup.cs, in ConfigureServices I added services.AddAuthentication(Microsoft.AspNetCore.Server.IISIntegration.IISDefaults.AuthenticationScheme); as mentioned in https://learn.microsoft.com/en-us/aspnet/core/migration/1x-to-2x/identity-2x#windows-authentication-httpsys--iisintegration

4. I added a simple Console.WriteLine(context.User.Identity.Name); to see that it works inside app.Run and... It all works!

However... as soon as I set "anonymousAuthentication" to true in launchSettings.json it stops working and I cannot figure out what can I do to make the Windows authentication work alongside with it. Context.User.Identity.IsAuthenticated is always false. As you can see my configuration is very simple and I need it to stay this way. I want to enable/disable windows authentication on certain dynamic routes, so using controllers with the [Authorize] attribute is not an option.

What I'm trying to achieve is a simple app where the url "/authenticated" would reply with the value of context.User.Identity.Name and the url "/public" would reply with something like say "This is a public page!". Something similar to NTLM authentication on specific route in ASP.NET Core but without the [Authorize] attribute and controllers. The resources are very scarce... Anyone have any idea what I could be missing? Thanks!

Answer 1

Anonymous takes precedence. You need to call httpContext.ChallengeAsync() when you get an anonymous request to a restricted part of your app. That will cause the client to send credentials on the next request. Here's a test that does this.

Answer 2

Tratcher's answer saved me after some wasted time on this topic. For a very simple scenario (anonymous controller + windows authentication restricted in the rest), here is a quick start (middleware):

public class NtlmAndAnonymousSetupMiddleware
{
    private readonly RequestDelegate next;

    public NtlmAndAnonymousSetupMiddleware(RequestDelegate next)
    {
        this.next = next;
    }

    public async Task Invoke(HttpContext context)
    {
        if (context.User.Identity.IsAuthenticated || context.Request.Path.ToString().StartsWith("/Anonymous"))
        {
            await next(context);
            return;
        }

        await context.ChallengeAsync("Windows");
    }

}

I have just plugged this in at the beginning of Startup.Configure method:

app.UseMiddleware<NtlmAndAnonymousSetupMiddleware>();