How to request authentication from custom middleware in ASP.NET Core 2.0

Question

I have two custom ASP.NET Core middlewares: one for authentication (that registers its own authentication scheme) and a second one for some business work.

How can I use the authentication middleware in another middleware? I can use authentication easily in an MVC like that:

 services.AddMvc(config =>
 {
     var policy = new AuthorizationPolicyBuilder()
                      .RequireAuthenticatedUser()
                      .Build();
     config.Filters.Add(new AuthorizeFilter(policy));
 });

I can also provide my own AuthenticationSchemeProvider to use different authentication schemes based on the requested URL. But the authentication middleware only runs for MVC controllers. I want it to run also before my custom middleware runs. Is it possible to do that?

Answer 1

In custom middleware method Invoke() call ChallengeAsync() if user is not authenticated:

public async Task Invoke(HttpContext httpContext, IServiceProvider serviceProvider)
{
    if (!httpContext.User.Identity.IsAuthenticated)
    {
        await httpContext.ChallengeAsync();
    }
    else { /* logic here */ }
}

NuGet package Microsoft.AspNetCore.Authentication.Abstractions has to be added.

Above code will run the default authentication service to authenticate user. If the default one is your custom authentication middleware, then it will be called.