How to allow an anonymous user access to some given page in MVC?

Question

I have enabled form authentication in my ASP.NET MVC web application. I want to allow anonymous users access only to some specific pages, including Register.cshtml for instance. I was able to allow access to my CSS-file from my root web.config by doing this.

<location path="Content/Site.css">
    <system.web>
        <authorization>
            <allow users="*"/>
        </authorization>
    </system.web>
</location>

Now I want to allow anonymous access to other pages, like Home and Register. Do any body know how to achieve this?

Answer 1

In MVC you normally use the [Authorize] attribute to manage authorization. Controllers or individual actions that are dressed with that attribute will require that the user is authorized in order to access them - all other actions will be available to anonymous users.

In other words, a black-list approach, where actions that require authorization are black-listed for anonymous users using [Authorize] - all actions (not dressed with the attribute) will be available.

Update:

With MVC4 a new attribute has been introduced, namely the [AllowAnonymous] attribute. Together with the [Authorize] attribute, you can now take a white-list approach instead. The white-list approach is accomplished by dressing the entire controller with the [Authorize] attribute, to force authorization for all actions within that controller. You can then dress specific actions, that shouldn't require authorization, with the [AllowAnonymous] attribute, and thereby white-listing only those actions. With this approach, you can be confident that you don't, by accident, forget to dress an action with the [Authorize], leaving it available to anyone, even though it shouldn't.

Your code could then be something like this:

[Authorize]
public class UserController : Controller {

   [AllowAnonymous]
   public ActionResult LogIn () {
      // This action can be accessed by unauthorized users
   }

   public ActionResult UserDetails () {
      // This action can NOT be accessed by unauthorized users
   }
}