## Safemode

A library for safe evaluation of Ruby code based on RubyParser and
Ruby2Ruby. Provides Rails ActionView template handlers for ERB and Haml.

### Word of warning

This library is still highly experimental. Only use it at your own risk for
anything beyond experiments and playing.

That said, please **do** play with it, read and run the unit tests and provide
feedback to help make it waterproof and finally suitable for serious purposes.

### Usage

For manual evaluation of Ruby code and ERB templates see demo.rb

You can use the ActionView template handlers by registering them, e.g., in 
a config/initializer file like this:

    # in config/intializer/safemode_tempate_handlers.rb
    ActionView::Template.register_template_handler :serb, ActionView::TemplateHandlers::SafeErb
    ActionView::Template.register_template_handler :haml, ActionView::TemplateHandlers::SafeHaml

If you register the ERB template handler for the file extension :erb be aware
that this most probably will break when your application tries to render an
error message in development mode (because Rails will try to use the handler
to render the error message itself).

You will then have to "whitelist" all method calls to the objects that are
registered as template variables by explicitely allowing access to them. You
can do that by defining a Safemode::Jail class for your classes, like so:

    class User
      class Jail < Safemode::Jail
        allow :name
      end
    end  
  
This will allow your template users to access the name method on your User 
objects.

For more details about the concepts behind Safemode please refer to the 
following blog posts until a more comprehensive writeup is available:

* Initial reasoning: [http://www.artweb-design.de/2008/2/5/sexy-theme-templating-with-haml-safemode-finally](http://www.artweb-design.de/2008/2/5/sexy-theme-templating-with-haml-safemode-finally)
* Refined concept: [http://www.artweb-design.de/2008/2/17/sending-ruby-to-the-jail-an-attemp-on-a-haml-safemode](http://www.artweb-design.de/2008/2/17/sending-ruby-to-the-jail-an-attemp-on-a-haml-safemode)
* ActionView ERB handler: [http://www.artweb-design.de/2008/4/22/an-erb-safemode-handler-for-actionview](http://www.artweb-design.de/2008/4/22/an-erb-safemode-handler-for-actionview)
  
### Dependencies

Requires the gems:

* RubyParser
* Ruby2Ruby

As of writing RubyParser alters StringIO and thus breaks usage with Rails.
See [http://www.zenspider.com/pipermail/parsetree/2008-April/000026.html](http://www.zenspider.com/pipermail/parsetree/2008-April/000026.html)

A patch is included that fixes this issue and can be applied to RubyParser.
See lib/ruby\_parser\_string\_io\_patch.diff

### Credits

* Sven Fuchs - Maintainer
* Peter Cooper

This code and all of the Safemode library's code was initially written by 
Sven Fuchs to allow Haml to have a safe mode. It was then modified and
re-structured by Peter Cooper and Sven Fuchs to extend the idea to generic
Ruby eval situations.