I am encountering an infinite redirect loop between login.microsoftonline.com and my application. My project is implementing authentication and authorization in an Asp.net 4.8 web forms project. I am able to add authentication using the default Owin startup file and then require authentication in the web config file. The below works correctly for requiring a user to sign in before being able to access pages/AuthRequired

StartupAuth.CS

public partial class Startup
    {
        private static string clientId = ConfigurationManager.AppSettings["ida:ClientId"];
        private static string postLogoutRedirectUri = ConfigurationManager.AppSettings["ida:PostLogoutRedirectUri"];
        private static string authority = ConfigurationManager.AppSettings["ida:Authority"];
        private static string clientSecret = ConfigurationManager.AppSettings["AppRegistrationSecret-Local"];
        public void ConfigureAuth(IAppBuilder app)
        {
            //for debugging
            //IdentityModelEventSource.ShowPII = true;

            app.SetDefaultSignInAsAuthenticationType(CookieAuthenticationDefaults.AuthenticationType);

            app.UseCookieAuthentication(new CookieAuthenticationOptions());
            app.UseOpenIdConnectAuthentication(
                new OpenIdConnectAuthenticationOptions
                {
                    ClientId = clientId,
                    Authority = authority,
                    PostLogoutRedirectUri = postLogoutRedirectUri,
                    ClientSecret = clientSecret,
                    RedirectUri = postLogoutRedirectUri,
                    //This allows multitenant
                    //https://github.com/Azure-Samples/guidance-identity-management-for-multitenant-apps/blob/master/docs/03-authentication.md
                    TokenValidationParameters = new TokenValidationParameters
                    {
                        ValidateIssuer = false
                    },

                    Notifications = new OpenIdConnectAuthenticationNotifications()
                    {
                        AuthenticationFailed = (context) =>
                        {
                            return Task.FromResult(0);
                        }
                    }
                }
                );

            // This makes any middleware defined above this line run before the Authorization rule is applied in web.config
            app.UseStageMarker(PipelineStage.Authenticate);
        }
    }

Web.Config

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I need to add authorization so that only users with the admin role will be able to access Pages/AuthRequired. I have done that by updating the web config:

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Adding authorization to the authenticated page works correctly if the user has that role, but if a user who doesn't have the role tries to access the page they are redirected back to login.microsoftonline.com and then back to the application in an infinite loop.

I can see that Owin UseOpenIdConnectAuthentication is returning a 302 response on unauthorized and that is causing the loop.

How can I change it so that instead of redirecting unauthorized (but authenticated) users to login.microsoftonline.com, that user should be directed to an app page that displays a 401 error?