Where do I prevent users from accessing other users' data?

Question

On a website I am building I need to allow users to edit their orders. Easy enough. But how do I ensure that a user cannot edit other users' orders? Do I perform checks in the model or in the controller to verify that the order belongs to the authenticated user?

Answer 1

Well hopefully your site doesn't have any way for a user to even attempt to edit someone else's orders. But if it's still possible to try, you could put that logic in either the model or controller. It's a matter of opinion. Some people will say that the controller should do things like access checks, and the model only knows how to modify itself. Others will say "fat model, skinny controller" and say that the security checks need to be reusable across controllers and so they should go in the model. It's your call.

Answer 2

Put checks in the view (yes, the view) for rapid response to user errors.

Put checks in the controller to ensure data integrity.

For example, in a web based app, you might have browser javascript to check all fields, including username, so the user gets rapid response to fix erroneous transactions. However, back at your server, you can not rely on the browser to really validate the data, since the browser is outside your control -- it might be corrupted, either intentionally or accidentally, and not doing validation as you intend. Thus you need to revalidate everything on your server to ensure integrity.