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require 'active_support/core_ext/class/attribute'
module ActionController #:nodoc:
class InvalidAuthenticityToken < ActionControllerError #:nodoc:
end
# Protecting controller actions from CSRF attacks by ensuring that all forms are coming from the current
# web application, not a forged link from another site, is done by embedding a token based on a random
# string stored in the session (which an attacker wouldn't know) in all forms and Ajax requests generated
# by Rails and then verifying the authenticity of that token in the controller. Only HTML/JavaScript
# requests are checked, so this will not protect your XML API (presumably you'll have a different
# authentication scheme there anyway). Also, GET requests are not protected as these should be
# idempotent anyway.
#
# This is turned on with the <tt>protect_from_forgery</tt> method, which will check the token and raise an
# ActionController::InvalidAuthenticityToken if it doesn't match what was expected. You can customize the
# error message in production by editing public/422.html. A call to this method in ApplicationController is
# generated by default in post-Rails 2.0 applications.
#
# The token parameter is named <tt>authenticity_token</tt> by default. If you are generating an HTML form
# manually (without the use of Rails' <tt>form_for</tt>, <tt>form_tag</tt> or other helpers), you have to
# include a hidden field named like that and set its value to what is returned by
# <tt>form_authenticity_token</tt>.
#
# Request forgery protection is disabled by default in test environment. If you are upgrading from Rails
# 1.x, add this to config/environments/test.rb:
#
# # Disable request forgery protection in test environment
# config.action_controller.allow_forgery_protection = false
#
# == Learn more about CSRF (Cross-Site Request Forgery) attacks
#
# Here are some resources:
# * http://isc.sans.org/diary.html?storyid=1750
# * http://en.wikipedia.org/wiki/Cross-site_request_forgery
#
# Keep in mind, this is NOT a silver-bullet, plug 'n' play, warm security blanket for your rails application.
# There are a few guidelines you should follow:
#
# * Keep your GET requests safe and idempotent. More reading material:
# * http://www.xml.com/pub/a/2002/04/24/deviant.html
# * http://www.w3.org/Protocols/rfc2616/rfc2616-sec9.html#sec9.1.1
# * Make sure the session cookies that Rails creates are non-persistent. Check in Firefox and look
# for "Expires: at end of session"
#
module RequestForgeryProtection
extend ActiveSupport::Concern
include AbstractController::Helpers
include AbstractController::Callbacks
included do
# Sets the token parameter name for RequestForgery. Calling +protect_from_forgery+
# sets it to <tt>:authenticity_token</tt> by default.
config_accessor :request_forgery_protection_token
self.request_forgery_protection_token ||= :authenticity_token
# Controls whether request forgergy protection is turned on or not. Turned off by default only in test mode.
config_accessor :allow_forgery_protection
self.allow_forgery_protection = true if allow_forgery_protection.nil?
helper_method :form_authenticity_token
helper_method :protect_against_forgery?
end
module ClassMethods
# Turn on request forgery protection. Bear in mind that only non-GET, HTML/JavaScript requests are checked.
#
# Example:
#
# class FooController < ApplicationController
# protect_from_forgery :except => :index
#
# # you can disable csrf protection on controller-by-controller basis:
# skip_before_filter :verify_authenticity_token
# end
#
# Valid Options:
#
# * <tt>:only/:except</tt> - Passed to the <tt>before_filter</tt> call. Set which actions are verified.
def protect_from_forgery(options = {})
self.request_forgery_protection_token ||= :authenticity_token
before_filter :verify_authenticity_token, options
end
end
protected
def protect_from_forgery(options = {})
self.request_forgery_protection_token ||= :authenticity_token
before_filter :verify_authenticity_token, options
end
# The actual before_filter that is used. Modify this to change how you handle unverified requests.
def verify_authenticity_token
verified_request? || raise(ActionController::InvalidAuthenticityToken)
end
# Returns true or false if a request is verified. Checks:
#
# * is the format restricted? By default, only HTML requests are checked.
# * is it a GET request? Gets should be safe and idempotent
# * Does the form_authenticity_token match the given token value from the params?
def verified_request?
!protect_against_forgery? || request.forgery_whitelisted? ||
form_authenticity_token == params[request_forgery_protection_token]
end
# Sets the token value for the current session.
def form_authenticity_token
session[:_csrf_token] ||= ActiveSupport::SecureRandom.base64(32)
end
# The form's authenticity parameter. Override to provide your own.
def form_authenticity_param
params[request_forgery_protection_token]
end
def protect_against_forgery?
allow_forgery_protection
end
end
end
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