ASP.NET MVC Attribute to only let user edit his/he

问题:

I have a controller method called Edit in which the user can edit data they had created like so ...

public ActionResult Edit(int id)
{
    Submission submission = unit.SubmissionRepository.GetByID(id);
    User user = unit.UserRepository.GetByUsername(User.Identity.Name);

    //Make sure the submission belongs to the user
    if (submission.UserID != user.UserID)
    {
        throw new SecurityException("Unauthorized access!");
    }

    //Carry out method
}

This method works fine however it is a little messy to put in every controller Edit method. Each table always has a UserID so I was wondering if there was an easier way to automate this via an [Authorize] Attribute or some other mechanism to make the code cleaner.

回答1:

Yes, you could achieve that through a custom Authorize attribute:

public class MyAuthorizeAttribute : AuthorizeAttribute
{
    protected override bool AuthorizeCore(HttpContextBase httpContext)
    {
        var authorized = base.AuthorizeCore(httpContext);
        if (!authorized)
        {
            return false;
        }

        var rd = httpContext.Request.RequestContext.RouteData;

        var id = rd.Values["id"];
        var userName = httpContext.User.Identity.Name;

        Submission submission = unit.SubmissionRepository.GetByID(id);
        User user = unit.UserRepository.GetByUsername(userName);

        return submission.UserID == user.UserID;
    }
}

and then:

[MyAuthorize]
public ActionResult Edit(int id)
{
    // Carry out method
}

and let's suppose that you need to feed this submission instance that we fetched into the custom attribute as action parameter to avoid hitting the database once again you could do the following:

public class MyAuthorizeAttribute : AuthorizeAttribute
{
    protected override bool AuthorizeCore(HttpContextBase httpContext)
    {
        var authorized = base.AuthorizeCore(httpContext);
        if (!authorized)
        {
            return false;
        }

        var rd = httpContext.Request.RequestContext.RouteData;

        var id = rd.Values["id"];
        var userName = httpContext.User.Identity.Name;

        Submission submission = unit.SubmissionRepository.GetByID(id);
        User user = unit.UserRepository.GetByUsername(userName);

        rd.Values["model"] = submission;

        return submission.UserID == user.UserID;
    }
}

and then:

[MyAuthorize]
public ActionResult Edit(Submission model)
{
    // Carry out method
}

回答2:

I would suggest you pull the logic out of the action/controller and build a domain class to handle that logic.

Action methods should really only deal with getting data from and sending data to the view. You could create something generic enough to handle your needs but will also follow the single responsibility principal.

public class AuthorizedToEdit 
{
     protected override bool AuthorizeCore(string user, int itemId)
     {
         var userName = httpContext.User.Identity.Name;

         var authUsers = SubmissionRepository.GetAuthoriedUsers(itemId);

         return authUsers.Contains(user);
     }
}

This would also allow you to have the flexibility later on to allow something like admin users

回答3:

I recommend reading up on the AuthorizeAttribute (see here). Also, have you seen this post? It goes over how to override the authentication attribute innards and how to use IPrincipal and IIdentity.