ASP.NET MVC Roles and Security

Question

Assume like this is my SampleController action method

public ActionResult AdminView()
{
    return View()
}

If want this controller method to be called if the logged in user belongs to admin role, otherwise this method call should be blocked and the user should get an some custom unauthorized access error page.

In my asp .net mvc web application, when the user logs in, I am storing the user role in a session as a string. And whenever there is a need to validate the user role, I compare the value stored in the session against a constant say "ADMIN_ROLE". But I am writing that piece of code to check for the user role in almost every controller action method and then either return an appropriate view for the user or an unauthorized access page view if the user role is restricted for the controller action method.

I googled and read that we can use something like this.

[Authorize(Roles="admin")]
public ActionResult AdminView()
{
  return View()
}

But I am not sure how the Authorize and the Roles keyword works. How when putting Roles = "Admin", is going to help in checking my user role string stored in the session, or how I can redirect a user to unauthorized page, in case the role does not match the role tagged for the action method.

Answer 1

As per my thinking you need to code for authorization.

public class AuthorizeAttribute : FilterAttribute, IAuthorizationFilter
{
    private readonly RoleEnum[] _acceptedRoles;

    public AuthorizeAttribute(params RoleEnum[] acceptedroles)
    {
        _acceptedRoles = acceptedroles;
    }

    public AuthorizeAttribute(params bool[] allowAll)
    {
        if (allowAll[0])
            _acceptedRoles = new RoleEnum[] { RoleEnum.Admin, RoleEnum.user};
    }

    public void OnAuthorization(AuthorizationContext filterContext)
    {
        if (SessionHelper.UserInSession == null)//user not logged in
        {
            FormsAuthentication.SignOut();
            filterContext.Result =
                 new RedirectToRouteResult(new System.Web.Routing.RouteValueDictionary {{ "controller", "Home" },
                                             { "action", "Index" },
                                             { "returnUrl",    filterContext.HttpContext.Request.RawUrl } });//send the user to login page with return url
            return;
        }
        if (!_acceptedRoles.Any(acceptedRole => SessionHelper.UserInSession.UserRoles.Any(currentRole => acceptedRole == currentRole.Role)))
            //allow if any of the user roles is among accepted roles. Else redirect to login page
            throw new UnauthorizedAccessException();

    }
}

This is also work for return URL.

Answer 2

As per comments, if you are using custom authentication/authorization mechanism then you need to implement custom authorize attribute where you can put custom logic to check if user has admin role or not. Something like below:

public class CustomizedAuthorizeAttribute : AuthorizeAttribute
{
    public override void OnAuthorization(AuthorizationContext filterContext)
    {
        //check for role in session variable "ADMIN_ROLE"

    //if not valid user then set
    filterContext.Result = new RedirectResult(URL)
    }
}

Answer 3

There is a small nice explanation in this link:

http://weblogs.asp.net/jgalloway/archive/2011/04/28/looking-at-how-asp-net-mvc-authorize-interacts-with-asp-net-forms-authorization.aspx

as per this:

ASP.NET MVC includes an [Authorize] attribute, which when placed on any controller actions will forbid unauthorized access. The AuthorizeAttribute allows you to specify a list of roles or users. You can also place the AuthorizeAttribute on a controller, in which case it will apply to all actions in the controller. Attempting to access an action secured by the AuthorizeAttribute when you're not logged in will take you to a standard LogOn screen, with a link to register if you don't already have an account.

How does the [Authorize] attribute redirect me to Log On?

The AuthorizeAttribute is an ActionFilter, which means that it can execute before the associated controller action. The AuthorizeAttribute performs its main work in the OnAuthorization method, which is a standard method defined in the IAuthorizationFilter interface. Checking the MVC source code, we can see that the underlying security check is really just looking at the underlying authentication information held by the ASP.NET context:

IPrincipal user = httpContext.User;

if (!user.Identity.IsAuthenticated)
{
    return false;
}

If the user fails authentication, an HttpUnauthorizedResult ActionResult is returned, which produces an HTTP 401(Unauthorized) status code. If it weren’t for ASP.NET Forms Authentication, an HTTP 401 status code would be sent to the browser, which would show the browser’s default login prompt.