Module: ActionController::RequestForgeryProtection

Relationships & Source Files
Namespace Children
Modules: `ClassMethods`, `ProtectionMethods`
Classes: `CookieStore`, `SessionStore`
Extension / Inclusion / Inheritance Descendants
Included In: `Base`, `::ActionView::TestCase::TestController`, `::Rails::ApplicationController`, `::Rails::DevtoolsController`, `::Rails::HealthController`, `::Rails::InfoController`, `::Rails::MailersController`, `::Rails::PwaController`, `::Rails::WelcomeController`
Super Chains via Extension / Inclusion / Inheritance
Class Chain: self, `::ActiveSupport::DescendantsTracker`, `::ActiveSupport::Concern`
Instance Chain: self, `::AbstractController::Callbacks`, `::ActiveSupport::Callbacks`, `::AbstractController::Helpers`
Defined in:	actionpack/lib/action_controller/metal/request_forgery_protection.rb

Overview

Controller actions are protected from Cross-Site Request Forgery (CSRF) attacks by checking the Sec-Fetch-Site header sent by modern browsers to indicate the relationship between request's initiator origin and the origin of the requested resource (https://developer.mozilla.org/en-US/docs/Web/HTTP/Reference/Headers/Sec-Fetch-Site)

For applications that need to support older browsers, there's a token-based fallback. A token is included in the rendered HTML for your application. This token is stored as a random string in the session, to which an attacker does not have access. When a request reaches your application, ::Rails verifies the received token with the token in the session. All requests are checked except GET requests as these should be idempotent. Keep in mind that all session-oriented requests are CSRF protected by default, including JavaScript and HTML requests.

Since HTML and JavaScript requests are typically made from the browser, we need to ensure to verify request authenticity for the web browser. We can use session-oriented authentication for these types of requests, by using the protect_from_forgery method in our controllers.

GET requests are not protected since they don't have side effects like writing to the database and don't leak sensitive information. JavaScript requests are an exception: a third-party site can use a