Protect from forgery by default

Rather than protecting from forgery in the generated
ApplicationController, add it to ActionController::Base by config. This
configuration defaults to false to support older versions which have
removed it from their ApplicationController, but is set to true for
Rails 5.2.

3 files changed, 22 insertions, 0 deletions

diff --git a/actionpack/CHANGELOG.md b/actionpack/CHANGELOG.md
index f8fd2403ef..59a7f12ac6 100644
--- a/actionpack/CHANGELOG.md
+++ b/actionpack/CHANGELOG.md
@@ -1,3 +1,13 @@
+*   Protect from forgery by default
+
+    Rather than protecting from forgery in the generated ApplicationController,
+    add it to ActionController::Base depending on
+    `config.action_controller.default_protect_from_forgery`. This configuration
+    defaults to false to support older versions which have removed it from their
+    ApplicationController, but is set to true for Rails 5.2.
+
+    *Lisa Ugray*
+
 *   Fallback `ActionController::Parameters#to_s` to `Hash#to_s`.
 
     *Kir Shatrov*
diff --git a/actionpack/lib/action_controller/metal/request_forgery_protection.rb b/actionpack/lib/action_controller/metal/request_forgery_protection.rb
index 4468cbb2fc..117dee2219 100644
--- a/actionpack/lib/action_controller/metal/request_forgery_protection.rb
+++ b/actionpack/lib/action_controller/metal/request_forgery_protection.rb
@@ -85,6 +85,10 @@ module ActionController #:nodoc:
       config_accessor :per_form_csrf_tokens
       self.per_form_csrf_tokens = false
 
+      # Controls whether forgery protection is enabled by default.
+      config_accessor :default_protect_from_forgery
+      self.default_protect_from_forgery = false
+
       helper_method :form_authenticity_token
       helper_method :protect_against_forgery?
     end
diff --git a/actionpack/lib/action_controller/railtie.rb b/actionpack/lib/action_controller/railtie.rb
index 31db7518f1..1c1cd58732 100644
--- a/actionpack/lib/action_controller/railtie.rb
+++ b/actionpack/lib/action_controller/railtie.rb
@@ -69,5 +69,13 @@ module ActionController
         config.compile_methods! if config.respond_to?(:compile_methods!)
       end
     end
+
+    initializer "action_controller.request_forgery_protection" do |app|
+      ActiveSupport.on_load(:action_controller_base) do
+        if app.config.action_controller.default_protect_from_forgery
+          protect_from_forgery with: :exception
+        end
+      end
+    end
   end
 end