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Manages the new SameSite=None behavior for Rails apps that use cookie-based authentication for cross-domain requests
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README.md

RailsSameSiteCookie

This gem sets the SameSite=None directive on all cookies coming from your Rails app that are missing the SameSite directive. This behavior can also be limited to only requests coming from a specific user agent.

This is useful because in February 2020 Chrome will start treating any cookies without the SameSite directive set as though they are SameSite=Lax(https://www.chromestatus.com/feature/5088147346030592). This is a breaking change from the previous default behavior which was to treat those cookies as SameSite=None. See this explanation for more information on the SameSite directive and the reasons for this change.

This new behavior shouldn't be a problem for most apps but if your Rails app provides an API that uses cookies for authentication (which itself may or may not be ill-advised), the new behavior means cookie authenticated requests to your API from third-party domains will no longer work in Chrome. In addition, fixing the problem isn't as simple as just setting SameSite=None on your app's cookies because there are a number of user agents that will either (a) ignore cookies with SameSite=None or (b) treat SameSite=None as SameSite=Strict. In other words, if a cookie-authenticated API sets SameSite=None it will break for some users, and if it doesn't set SameSite=None, it will also break for many users.

This gem fixes the above problems by explicity setting SameSite=None for all cookies where the SameSite directive is missing and the requesting user agent is not in Chrome's provided list of known incompatible clients.

Note about HTTP requests and local testing

Note that the gem only sets the "Secure" flag (which Chrome will also require for SameSite=None cookies) on cookies sent over HTTPS. So if you're testing on your local machine and you haven't setup your localhost to use SSL you will see warnings in Chrome about the cookies lacking the Secure flag. If the gem did set this flag in these cases, you would not see the warning and instead the cookies would simply be ignored. Once Chrome 80 is released you will either have to setup SSL on your localhost or start using a different browser for development, because Chrome will begin ignoring these cookies for lacking the Secure flag.

Installation

Add this line to your application's Gemfile:

gem 'rails_same_site_cookie'

And then execute:

$ bundle

Or install it yourself as:

$ gem install rails_same_site_cookie

Usage

Once you've installed the gem that's basically it unless you want to limit the SameSite=None behavior to specific user agents. This can be useful, for example, if you have a cordova app (or other client) that accesses your API using a custom user agent string and you know in those situations that the cookie will not be accessible to third party sites because the containing browser will never be allowed to navigate to other domains.

To set this up:

#config/initializers/rails_same_site_cookie.rb
RailsSameSiteCookie.configure do |config|
  config.user_agent_regex = /MyCustomUserAgentString/
end

Now only user agents that support SameSite=None and match the given regex string will have the directive set.

Development

After checking out the repo, run bin/setup to install dependencies. Then, run rake spec to run the tests. You can also run bin/console for an interactive prompt that will allow you to experiment.

To install this gem onto your local machine, run bundle exec rake install. To release a new version, update the version number in version.rb, and then run bundle exec rake release, which will create a git tag for the version, push git commits and tags, and push the .gem file to rubygems.org.

Contributing

Bug reports and pull requests are welcome on GitHub at https://github.com/[USERNAME]/rails_same_site_cookie. This project is intended to be a safe, welcoming space for collaboration, and contributors are expected to adhere to the Contributor Covenant code of conduct.

License

The gem is available as open source under the terms of the MIT License.

Code of Conduct

Everyone interacting in the RailsSameSiteCookie project’s codebases, issue trackers, chat rooms and mailing lists is expected to follow the code of conduct.

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