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SafeCookies

This gem has a middleware that will make all cookies secure, by setting the HttpOnly and the secure flag for all cookies the application sets on the client.

Making a cookie HttpOnly prevents Javascripts from seeing it, which really should be the default. It makes it way harder to steal cookie information via malicious Javascript.

Making a cookie secure tells the browser to only send the cookie over HTTPS connections, protecting it from being sniffed by a man-in-the-middle. (Setting a HSTS header achieves the same, but Safari < 7 and IE < 11 don't speak HSTS.)

SafeCookies will additionally rewrite all cookies the user is sending. But it can only do so, if the cookie was registered before (see below). It will rewrite user cookies only once per user.

Installation

  1. Add gem 'safe_cookies' to your application's Gemfile, then run bundle install.

  2. Add a configuration block in an initializer (e.g. config/initializers/safe_cookies.rb):

    SafeCookies.configure do |config|
  # configuration ...
end

  3. Register the middleware:

    Rails 3+: add the following lines to the application block in config/application.rb:

    require 'safe_cookies'
config.middleware.insert_before ActionDispatch::Cookies, SafeCookies::Middleware

    Rails 2: add the following lines to the initializer block in config/environment.rb:

    require 'safe_cookies'
config.middleware.insert_before ActionController::Session::CookieStore, SafeCookies::Middleware

Now all new cookies will be made secure and HttpOnly. But what about cookies already out there?

Updating existing cookies

Unfortunately, the client won't ever tell us if it stores a cookie with flags such as secure or which expiry date it is stored with. Therefore, in order to make the middleware retroactively secure cookies owned by the client, you need to register each of those cookies with the middleware, specifying their properties.

Carefully scan your app for cookies you are using. There's no easy way to find out if you missed one (but see below for some help the gem provides).

SafeCookies.configure do |config|
  config.register_cookie 'remember_token', :expire_after => 1.year
  config.register_cookie 'last_action', :expire_after => 30.days, :path => '/commerce'
end

Available options are: :expire_after (required), :path, :secure, :http_only. For cookies with "session" expiry, set :expire_after => nil.

Tell SafeCookies which cookies not to make secure or HttpOnly by registering them, just like above:

SafeCookies.configure do |config|
  config.register_cookie 'default_language', :expire_after => 10.years, :secure => false
  config.register_cookie 'javascript_data', :expire_after => 1.day, :http_only => false
end

Finding unregistered user cookies

There are lots of cookies your application receives that you never did set. However, if you want to know about any unknown cookies touching your application, SafeCookies gives you two tools.

1) If you set config.log_unknown_cookies = true in the configuration block, all unknown cookies will be written to the Rails log. When you start implementing the middleware, closely watch it to find cookies you forgot to register.

2) You may overwrite SafeCookies::Middleware#handle_unknown_cookies(cookies) in the configuration block for customized behaviour (like, notifying you per email).

To ignore cookies that are irrelevant to you, you may configure them to be ignored. Use the config.ignore_cookie directive, which takes either a String or a Regex parameter. Be careful when using regular expressions!

In August 2013 we noticed a bug in SafeCookies < 0.1.4, by which secured cookies would be set for the current "directory" (see comments in cookie_path_fix.rb) instead of root (which usually is what you want). Users would get multiple cookies for that domain, leading to issues like being unable to sign in.

The configuration option config.fix_paths turns on fixing this error. It expects an option :for_cookies_secured_before => Time.parse('some minutes after you will have deployed') which reflects the point of time from which SafeCookies can expect cookies to be set with the correct path. It will only rewrite cookies with a new path if it had set them before that point of time.

Development

  • Tests live in spec.
  • You can run specs from the project root by saying bundle exec rake.

If you would like to contribute:

  • Fork the repository.
  • Push your changes with passing specs.
  • Send us a pull request.