C# – ASP.NET – Redirect to Error Page if Roles Authorization Fails

asp.net-mvcauthenticationcforms-authenticationnet

I am using MVC 3 with Forms Authentication. On my controller or methods, I am doing the following:

[Authorize (Roles = "developer")]

In this situation, I want to check if the user is logged in and if not, return them to the login page. However, if the 'IsInRole' check for that user returns false, I want them to go to a different view that says something like 'Not authorized'.

What is the best way to accomplish something like this? I was hoping to avoid creating a new Authorization attribute so I didn't have to refactor every Authorize attribute in my entire application, but if that is what is required, I will go that route.

Best Answer

A custom authorize attribute overriding the HandleUnauthorizedRequest method could do the job:

public class MyAuthorizeAttribute : AuthorizeAttribute
{
    protected override void HandleUnauthorizedRequest(AuthorizationContext filterContext)
    {
        if (!filterContext.HttpContext.User.Identity.IsAuthenticated)
        {
            // The user is not authenticated
            base.HandleUnauthorizedRequest(filterContext);
        }
        else if (!this.Roles.Split(',').Any(filterContext.HttpContext.User.IsInRole))
        {
            // The user is not in any of the listed roles => 
            // show the unauthorized view
            filterContext.Result = new ViewResult
            {
                ViewName = "~/Views/Shared/Unauthorized.cshtml"
            };
        }
        else
        { 
            base.HandleUnauthorizedRequest(filterContext);
        }
    }
}

and then:

[MyAuthorize(Roles = "developer")]
public ActionResult Develop()
{
    ...
}

Related Solutions

Asp.net-mvc – Why does AuthorizeAttribute redirect to the login page for authentication and authorization failures

When it was first developed, System.Web.Mvc.AuthorizeAttribute was doing the right thing - older revisions of the HTTP specification used status code 401 for both "unauthorized" and "unauthenticated".

From the original specification:

If the request already included Authorization credentials, then the 401 response indicates that authorization has been refused for those credentials.

In fact, you can see the confusion right there - it uses the word "authorization" when it means "authentication". In everyday practice, however, it makes more sense to return a 403 Forbidden when the user is authenticated but not authorized. It's unlikely the user would have a second set of credentials that would give them access - bad user experience all around.

Consider most operating systems - when you attempt to read a file you don't have permission to access, you aren't shown a login screen!

Thankfully, the HTTP specifications were updated (June 2014) to remove the ambiguity.

From "Hyper Text Transport Protocol (HTTP/1.1): Authentication" (RFC 7235):

The 401 (Unauthorized) status code indicates that the request has not been applied because it lacks valid authentication credentials for the target resource.

From "Hypertext Transfer Protocol (HTTP/1.1): Semantics and Content" (RFC 7231):

The 403 (Forbidden) status code indicates that the server understood the request but refuses to authorize it.

Interestingly enough, at the time ASP.NET MVC 1 was released the behavior of AuthorizeAttribute was correct. Now, the behavior is incorrect - the HTTP/1.1 specification was fixed.

Rather than attempt to change ASP.NET's login page redirects, it's easier just to fix the problem at the source. You can create a new attribute with the same name (AuthorizeAttribute) in your website's default namespace (this is very important) then the compiler will automatically pick it up instead of MVC's standard one. Of course, you could always give the attribute a new name if you'd rather take that approach.

[AttributeUsage(AttributeTargets.Class | AttributeTargets.Method, Inherited = true, AllowMultiple = true)]
public class AuthorizeAttribute : System.Web.Mvc.AuthorizeAttribute
{
    protected override void HandleUnauthorizedRequest(System.Web.Mvc.AuthorizationContext filterContext)
    {
        if (filterContext.HttpContext.Request.IsAuthenticated)
        {
            filterContext.Result = new System.Web.Mvc.HttpStatusCodeResult((int)System.Net.HttpStatusCode.Forbidden);
        }
        else
        {
            base.HandleUnauthorizedRequest(filterContext);
        }
    }
}

.net – How to redirect to a dynamic login URL in ASP.NET MVC

In the RTM version of ASP.NET MVC, the Cancel property is missing. This code works with ASP.NET MVC RTM:

using System;
using System.Web;
using System.Web.Mvc;
using System.Web.Mvc.Resources;

namespace ePegasus.Web.ActionFilters
{
    public class CustomAuthorize : AuthorizeAttribute
    {
        public override void OnAuthorization(AuthorizationContext filterContext)
        {
            base.OnAuthorization(filterContext);
            if (filterContext.Result is HttpUnauthorizedResult)
            {
                filterContext.Result = new RedirectToRouteResult(
                    new System.Web.Routing.RouteValueDictionary
                        {
                                { "langCode", filterContext.RouteData.Values[ "langCode" ] },
                                { "controller", "Account" },
                                { "action", "Login" },
                                { "ReturnUrl", filterContext.HttpContext.Request.RawUrl }
                        });
            }
        }
    }
}

Edit: You may want to disable the default forms authentication loginUrl in web.config - in case somebody forgets you have a custom attribute and uses the built in [Authorize] attribute by mistake.

Modify the value in web.config:

 <forms loginUrl="~/Account/ERROR" timeout="2880" />

Then make an action method 'ERROR' that logs an error and redirects the user to the most generic login page you have.

Best Answer

Related Solutions

Asp.net-mvc – Why does AuthorizeAttribute redirect to the login page for authentication and authorization failures

.net – How to redirect to a dynamic login URL in ASP.NET MVC

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