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.
@migueisan +5 for funny but I didn't mean to confuse you with the DSL magic and make you not notice that the example was deliberately degenerate.
My main issue is that too much responsibility is given to the update method when, with a complex model (which my example is not ) you should be calling object methods with a tightly defined parameter list to effect state change and not be using update_attributes with role based attr_accessible Just reading DHH's preferred method at http://rubydoc.info/gems/strong_parameters/0.1.3/frames and it makes sense with my suggested approach except I would move the strong parameter signatures into the model under explicit method names.
and in CANCAN
CANCAN enabled controller reduces to