MassassignmentSecurityForm
===============

Usage:
------

1. Add gem to your Gemfile
gem 'massassignment_security_form', :git => 'git://github.com/webhoernchen/massassignment_security_form.git'

2. bundle install

3. Create an initializer (massassignment_security_form.rb) like this:
MassassignmentSecurityForm::Config.password = 'Long secure password for encryption'

4. Your forms are secure now!


Example:
--------
<% form_tag({:action => "update"}) do %>
  <%= error_messages_for :user %>

  <table>
    <tr>
      <td><label for="user_title">Title:</label></td>
      <td><%= text_field :user, :title %></td>
    </tr>
    <tr>
      <td><label for="user_first_name">First name:</label></td>
      <td><%= text_field :user, :first_name %></td>
    </tr>
    <tr>
      <td><label for="user_name">Name:</label></td>
      <td><%= text_field :user, :name %></td>
    </tr>
  </table>
<% end %>

It creates the following form:

<form method="post" action="/route/to/users/update">
  <table>
    <tr>
      <td><label for="user_title">Titel:</label></td>
      <td><input type="text" value="" size="30" name="user[title]" id="user_title"></td>
    </tr>
    <tr>
      <td><label for="user_first_name">First name:</label></td>
      <td><input type="text" value="Christian" size="30" name="user[first_name]" id="user_first_name"></td>
    </tr>
    <tr>
      <td><label for="user_name">Name:</label></td>
      <td><input type="text" value="Eichhorn" size="30" name="user[name]" id="user_name"></td>
    </tr>
    <tr>
      <td>
        <input type="submit" value="save" name="commit">
      </td>
    </tr>
  </table>

  <input type="hidden" value="EncryptedHashWithFormFieldsForUser" name="massassignment_fields">
</form>

After the form is committed your controller remove all attributes of the users hash, which are not allowed in the form.


Security Example:
If your Admin-Verfication is an attribute of the user (:admin => true) and 
anyone adds a form field to your form in the browser like this:
<input type="hidden" value="1" name="user[admin]">

Normally (if you add no protection to the user class):
ActiveRecord will set the attribute "admin" to true for the given user on 
user.#update_attributes(params[:user])

This GEM removes the attr "admin" of the user params hash, because the attribute is not used in the form!


For Testing:
------------
Disable the Gem for your functional tests:

MassassignmentSecurityForm::Config.remove_not_allowed_massassignment_fields = false


Motivation
----------
 * Write a simple fix for the massassignment security problem in rails (ActiveRecord)


Tested with:
------------

* Rails 2.3.14
* formtastic 1.2.4


Help:
-----
This GEM should work with the most form_helpers in Rails

If you use a plugin or a gem with other form_helpers you can add the functionality of this GEM:
Define an extension for your form_helper like this:

def other_form_helper(object_name, method, *args)
  _add_form_field(object_name, method)
  super(object_name, method, *args)
end

Thats all!

For all other improvements:
* Please fork this GEM and send a pull request!


Credits
-------

Written by Christian Eichhorn
http://www.webmasters.de