ASP.NET Core 2.0 disable automatic challenge

Question

After upgrading my ASP.NET Core project to 2.0, attempts to access protected endpoints no longer returns 401, but redirects to an (non-existing) endpoint in an attempt to let the user authenticate.

The desired behaviour is for the application simply to return a 401. Previously I would set AutomaticChallenge = false when configuring authentication, but according to this article the setting is no longer relevant (in fact it doesn't exist anymore).

My authentication is configured like this:

Startup.cs.ConfigureServices():

services.AddAuthentication(CookieAuthenticationDefaults.AuthenticationScheme)
                .AddCookie(o =>
                {
                    o.Cookie.Name = options.CookieName;
                    o.Cookie.Domain = options.CookieDomain;
                    o.SlidingExpiration = true;
                    o.ExpireTimeSpan = options.CookieLifetime;
                    o.TicketDataFormat = ticketFormat;
                    o.CookieManager = new CustomChunkingCookieManager();
                });

Configure():

app.UseAuthentication();

How can I disable automatic challenge, so that the application returns 401 when the user is not authenticated?

Answer 1

Similiar to @Serverin, setting the OnRedirectToLogin of the Application Cookie worked, but must be done in statement following services.AddIdentity in Startup.cs:ConfigureServices:

services.ConfigureApplicationCookie(options => {
  options.Events.OnRedirectToLogin = context => {
    context.Response.Headers["Location"] = context.RedirectUri;
    context.Response.StatusCode = 401;
    return Task.CompletedTask;
  };
});