For a while, I have felt that the following is the correct way to improve the mass assignment problem without increasing the burden on new users. Now that the problem with the Rails default has been brought up again, it's a good time to revisit it.
When creating a form with form_for
, include a signed token including all of the fields that were created at form creation time. Only these fields are allowed.
To allow new known fields to be added via JS, we could add:
<%= f.allowed_fields "foo", "bar", "baz" %>
The first strategy will not full satisfy apps that support a lot of HTTP requests that do not come from forms generated by Rails.
Because accessible fields is usually a function of authorization, and is not global, we should move allowed fields into the controller. The basic idea is:
class PostsController < ApplicationController
# attributes can be marked accessible for the entire controller
attr_accessible :foo, :bar
def create
# mass assignment can also be done on an instance basis
# this can be used to override the class defaults
attr_accessible(true) if user.admin?
...
end
end
I would imagine that Rails authorization frameworks like CanCan could add sugar to make this even easier in common cases.
The core problem with Rails mass assignment is that attribute protection is an authorization concern. By moving it to the controller, we can have smart defaults (like signed fields in form_for
) and in more advanced cases, make it easier to decide what fields are allowed on a per-user basis.
By moving it into the correct place, we will probably find other nice abstractions that we can use over time to make nice defaults for users without compromising security.
@bradphelan You could say that Rails is overengineered when compared to Sinatra. Of course there are simpler cases where any solution seems feels like "too much". And those simple cases are actually the mayority. That's why a new layer must be able to seem transparent in its "default" mode and at the same time offer powerful features.
You are not dealing, for instance, with the problem of attributes from nested models (as many have noted). Or, as I said, with different models acting as a single resource for the end user. There is where a not overengineered solution comes into play.