Make Web API authentication return 401 instead of redirect to login page

Question

I have Web API with OWIN Authentication in Web MVC. I\'m using in Web.Config for my Web MVC so it\'s redirecting to login page.

Answer 1

In .NET Core I have solved it like this, Startup.cs:

    public void ConfigureServices(IServiceCollection services)
    {
            services.AddAuthentication(CookieAuthenticationDefaults.AuthenticationScheme)
            .AddCookie(options =>
            {
                options.Cookie.SameSite = SameSiteMode.Strict;
                options.Cookie.Name = "AuthCookie";
                options.Events.OnRedirectToAccessDenied = UnAuthorizedResponse;
                options.Events.OnRedirectToLogin = UnAuthorizedResponse;
            })
    ....
    }

    internal static Task UnAuthorizedResponse(RedirectContext<CookieAuthenticationOptions> context)
    {
        context.Response.StatusCode = (int) HttpStatusCode.Unauthorized;
        return Task.CompletedTask;
    }

Answer 2

I struggled with this issue and I came up with a way to only do the redirect if I didn't find the token that I use in the header for my custom manual authorization of my WebApi. This is my setup (notice the Provider object and OnApplyRedirect action)

    app.UseCookieAuthentication(new CookieAuthenticationOptions
   {
     AuthenticationType = DefaultAuthenticationTypes.ApplicationCookie,
     LoginPath = new PathString("/Account/Login"),
     ExpireTimeSpan = TimeSpan.FromMinutes(30),
     Provider =  new CookieAuthenticationProvider
      {
        OnApplyRedirect = (ctx) => {
            var token = HttpContext.Current.Request.Headers.Get("X-User-Token");
            if (token == null) ctx.Response.Redirect(ctx.RedirectUri);
         }
      }
   });  

Answer 3

This is what worked for me.

Creating a custom attribute:

[AttributeUsage(AttributeTargets.Class | AttributeTargets.Method, Inherited = true, AllowMultiple = true)]
public class NoRedirectAuthorizeAttribute : AuthorizeAttribute
{        
    protected override void HandleUnauthorizedRequest(HttpActionContext actionContext)
    {
        actionContext.Response = new System.Net.Http.HttpResponseMessage(System.Net.HttpStatusCode.Forbidden);
    }
}

Using the attribute in your controller:

    [HttpDelete]
    [NoRedirectAuthorizeAttribute(Roles = "Admin")]
    [Route("api/v3/thingstodelete/{id=id}")]
    public IHttpActionResult DeleteThingToDelete(Guid id)
    {
      //delete code
    }

Here are just overriding the HandleUnauthorizedRequest method of the AuthorizeAttribute. So, instead of sending a redirect (304) to the login page, we send Forbidden(403) HTTP status code.

Answer 4

I needed to configure the StatusCodePage middleware to avoid redirection

public void Configure(IApplicationBuilder app, IHostingEnvironment env)
{
    ...
    app.UseStatusCodePages();
    ...
}

Answer 5

In order to change the way IIS behaves based on a convention defined by URL, you want to branch your OWIN pipeline. You can do this by using IApplicationBuilder.Map. Assuming a static config:

public void Configure(IApplicationBuilder app)
{
    ...
    app.Map("/api", HandleWebApiRequests);
    ...
}

private static void HandleWebApiRequests(IApplicationBuilder app)
{
    app.UseWebApi(config);
}

The Map method branches the pipeline to the HandleWebApiRequests method based on an URL that begins with "/api".

This should cause 401 errors to behave like they are supposed to and simply return 401 with no redirect.

Answer 6

Create a custom AuthorizeAttribute:

public class MyAuthorizeAttribute : AuthorizeAttribute
{
    protected override void HandleUnauthorizedRequest(HttpActionContext actionContext)
    {
        actionContext.Response = actionContext.Request.CreateErrorResponse(HttpStatusCode.Unauthorized, "Unauthorized");
    }
}

If you in the future skip the web.config stuff and use owin to setup your authentication, you could in your Startup.cs do:

var provider = new CookieAuthenticationProvider();
var originalHandler = provider.OnApplyRedirect;
provider.OnApplyRedirect = context =>
{
    if (!context.Request.Uri.LocalPath.StartsWith(VirtualPathUtility.ToAbsolute("~/api")))
    {
        context.RedirectUri = new Uri(context.RedirectUri).PathAndQuery;
        originalHandler.Invoke(context);
    }
};

app.UseCookieAuthentication(new CookieAuthenticationOptions
{
    AuthenticationType = DefaultAuthenticationTypes.ApplicationCookie,
    CookieName = FormsAuthentication.FormsCookieName,
    LoginPath = new PathString("/Account/LogOn"),
    ExpireTimeSpan = TimeSpan.FromMinutes(240),
    Provider = provider
});