rails-angular-xss

When rendering AngularJS templates with a server-side templating engine like ERB 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 so AngularJS 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.

• Rails 5.0.x

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

1. Put this into your Gemfile

    gem 'rails-angular-xss'
   

2. Run bundle install.

3. Important: Add $rootScope.DOUBLE_LEFT_CURLY_BRACE = '{{' to your Angular app initialization.

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.

This gem originally patched ERB::Util HTML_ESCAPE constants to replace any occurence of the string {{ with the replacement ``{{ DOUBLE_LEFT_CURLY_BRACE }}. This will be interpolated by Angular, **and assuming you've followed step 4. above**, Angular returns the interpolated string {{`.

This allows users to actually use {{ without it being transformed by some invisible spaces, unicode characaters that look like a curly bracket and so on.

With Rails 5.0., ERB::Util utilizes the native CGI.escapeHTML of Ruby 2.3, we thus have to patch ERB::Util and SafeBuffer to check for {{ additionally.

• Fork the repository.
• Push your changes with specs. There is a Rails 5 test application in spec/app_root if you need to test integration with a live Rails app.
• Send a pull request.

Oliver Günther from OpenProject.

Original plugin and code for Rails < 5 by

Henning Koch from makandra.