angular_xss

When rendering AngularJS templates with a server-side templating engine like ERB or Haml it is easy to introduce XSS vulnerabilities. These vulnerabilities are enabled by AngularJS evaluating user-provided strings containing interpolation symbols (default symbols are {{ and }}).

This gem patches ERB/rails_xss and Haml so Angular interpolation symbols are auto-escaped in unsafe strings. And by auto-escaped we mean replacing {{ with {{ $root.DOUBLE_LEFT_CURLY_BRACE }}. To leave AngularJS interpolation marks unescaped, mark the string as html_safe.

This is an unsatisfactory hack. A better solution is very much desired, but is not possible without some changes in AngularJS. See the related AngularJS issue.

Disable escaping locally

If you want to disable angular_xss in some part of your app, you can use

AngularXss.disable do
  # no escaping here
end
# escaped again

Installation

0. Read the code so you know what you're getting into.

1. Put this into your Gemfile after other templating engines like Haml or Erubis:

    gem 'angular_xss' # put me after Haml, Erubis and other templating engines
   

2. Run bundle install.

3. Add this to your Angular code (replacing "myApp" of course):

   angular.module('myApp', []).run(['$rootScope', function($rootScope) {
     $rootScope.DOUBLE_LEFT_CURLY_BRACE = '{{';
   }]);
   

4. Run your test suite to find the places that broke.

5. Mark any string that is allowed to contain Angular expressions as #html_safe.

Known limitations

• Requires Haml. It could be refactored to only patch ERB/rails_xss.
• When using Haml with angular_xss, you can no longer use interpolation symbols in class or id attributes, even if the value is marked as html_safe. This is a limitation of Haml. Try using ng-class instead.

Development

• Fork the repository.
• Push your changes with specs. There is a Rails 3 test application in spec/app_root if you need to test integration with a live Rails app.
• You may run single tests with a specified Rails version via BUNDLE_GEMFILE=Gemfile.rails-7.0.haml-5 bundle exec rspec ./spec/angular_xss
• Send a pull request.

Credits

Henning Koch from makandra.