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require 'rack/session/abstract/id'
require 'action_controller/metal/exceptions'
module ActionController #:nodoc:
class InvalidAuthenticityToken < ActionControllerError #:nodoc:
end
class InvalidCrossOriginRequest < ActionControllerError #:nodoc:
end
# Controller actions are protected from Cross-Site Request Forgery (CSRF) attacks
# by including a token 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. Only HTML and JavaScript requests are checked,
# so this will not protect your XML API (presumably you'll have a different
# authentication scheme there anyway).
#
# 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 <script> tag to reference a JavaScript
# URL on your site. When your JavaScript response loads on their site, it executes.
# With carefully crafted JavaScript on their end, sensitive data in your JavaScript
# response may be extracted. To prevent this, only XmlHttpRequest (known as XHR or
# Ajax) requests are allowed to make GET requests for JavaScript responses.
#
# It's important to remember that XML or JSON requests are also affected and if
# you're building an API you'll need something like:
#
# class ApplicationController < ActionController::Base
# protect_from_forgery
# skip_before_action :verify_authenticity_token, if: :json_request?
#
# protected
#
# def json_request?
# request.format.json?
# end
# end
#
# CSRF protection is turned on with the <tt>protect_from_forgery</tt> method,
# which checks the token and resets the session if it doesn't match what was expected.
# A call to this method is generated for new \Rails applications by default.
#
# The token parameter is named <tt>authenticity_token</tt> by default. The name and
# value of this token must be added to every layout that renders forms by including
# <tt>csrf_meta_tags</tt> in the html +head+.
#
# Learn more about CSRF attacks and securing your application in the
# {Ruby on Rails Security Guide}[http://guides.rubyonrails.org/security.html].
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
# Holds the class which implements the request forgery protection.
config_accessor :forgery_protection_strategy
self.forgery_protection_strategy = nil
# Controls whether request forgery 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.
#
# class ApplicationController < ActionController::Base
# protect_from_forgery
# end
#
# class FooController < ApplicationController
# protect_from_forgery except: :index
#
# You can disable CSRF protection on controller by skipping the verification before_action:
# skip_before_action :verify_authenticity_token
#
# Valid Options:
#
# * <tt>:only/:except</tt> - Passed to the <tt>before_action</tt> call. Set which actions are verified.
# * <tt>:with</tt> - Set the method to handle unverified request.
#
# Valid unverified request handling methods are:
# * <tt>:exception</tt> - Raises ActionController::InvalidAuthenticityToken exception.
# * <tt>:reset_session</tt> - Resets the session.
# * <tt>:null_session</tt> - Provides an empty session during request but doesn't reset it completely. Used as default if <tt>:with</tt> option is not specified.
def protect_from_forgery(options = {})
self.forgery_protection_strategy = protection_method_class(options[:with] || :null_session)
self.request_forgery_protection_token ||= :authenticity_token
prepend_before_action :verify_authenticity_token, options
append_after_action :verify_same_origin_request
end
private
def protection_method_class(name)
ActionController::RequestForgeryProtection::ProtectionMethods.const_get(name.to_s.classify)
rescue NameError
raise ArgumentError, 'Invalid request forgery protection method, use :null_session, :exception, or :reset_session'
end
end
module ProtectionMethods
class NullSession
def initialize(controller)
@controller = controller
end
# This is the method that defines the application behavior when a request is found to be unverified.
def handle_unverified_request
request = @controller.request
request.session = NullSessionHash.new(request.env)
request.env['action_dispatch.request.flash_hash'] = nil
request.env['rack.session.options'] = { skip: true }
request.env['action_dispatch.cookies'] = NullCookieJar.build(request)
end
protected
class NullSessionHash < Rack::Session::Abstract::SessionHash #:nodoc:
def initialize(env)
super(nil, env)
@data = {}
@loaded = true
end
# no-op
def destroy; end
def exists?
true
end
end
class NullCookieJar < ActionDispatch::Cookies::CookieJar #:nodoc:
def self.build(request)
key_generator = request.env[ActionDispatch::Cookies::GENERATOR_KEY]
host = request.host
secure = request.ssl?
new(key_generator, host, secure, options_for_env({}))
end
def write(*)
# nothing
end
end
end
class ResetSession
def initialize(controller)
@controller = controller
end
def handle_unverified_request
@controller.reset_session
end
end
class Exception
def initialize(controller)
@controller = controller
end
def handle_unverified_request
raise ActionController::InvalidAuthenticityToken
end
end
end
protected
# The actual before_action that is used to verify the CSRF token.
# Don't override this directly. Provide your own forgery protection
# strategy instead. If you override, you'll disable same-origin
# `<script>` verification.
#
# Lean on the protect_from_forgery declaration to mark which actions are
# due for same-origin request verification. If protect_from_forgery is
# enabled on an action, this before_action flags its after_action to
# verify that JavaScript responses are for XHR requests, ensuring they
# follow the browser's same-origin policy.
def verify_authenticity_token
mark_for_same_origin_verification!
if !verified_request?
logger.warn "Can't verify CSRF token authenticity" if logger
handle_unverified_request
end
end
def handle_unverified_request
forgery_protection_strategy.new(self).handle_unverified_request
end
CROSS_ORIGIN_JAVASCRIPT_WARNING = "Security warning: an embedded " \
"<script> tag on another site requested protected JavaScript. " \
"If you know what you're doing, go ahead and disable forgery " \
"protection on this action to permit cross-origin JavaScript embedding."
private_constant :CROSS_ORIGIN_JAVASCRIPT_WARNING
# If `verify_authenticity_token` was run (indicating that we have
# forgery protection enabled for this request) then also verify that
# we aren't serving an unauthorized cross-origin response.
def verify_same_origin_request
if marked_for_same_origin_verification? && non_xhr_javascript_response?
logger.warn CROSS_ORIGIN_JAVASCRIPT_WARNING if logger
raise ActionController::InvalidCrossOriginRequest, CROSS_ORIGIN_JAVASCRIPT_WARNING
end
end
# GET requests are checked for cross-origin JavaScript after rendering.
def mark_for_same_origin_verification!
@marked_for_same_origin_verification = request.get?
end
# If the `verify_authenticity_token` before_action ran, verify that
# JavaScript responses are only served to same-origin GET requests.
def marked_for_same_origin_verification?
@marked_for_same_origin_verification ||= false
end
# Check for cross-origin JavaScript responses.
def non_xhr_javascript_response?
content_type =~ %r(\Atext/javascript) && !request.xhr?
end
# Returns true or false if a request is verified. Checks:
#
# * is it a GET or HEAD request? Gets should be safe and idempotent
# * Does the form_authenticity_token match the given token value from the params?
# * Does the X-CSRF-Token header match the form_authenticity_token
def verified_request?
!protect_against_forgery? || request.get? || request.head? ||
form_authenticity_token == params[request_forgery_protection_token] ||
form_authenticity_token == request.headers['X-CSRF-Token']
end
# Sets the token value for the current session.
def form_authenticity_token
session[:_csrf_token] ||= SecureRandom.base64(32)
end
# The form's authenticity parameter. Override to provide your own.
def form_authenticity_param
params[request_forgery_protection_token]
end
# Checks if the controller allows forgery protection.
def protect_against_forgery?
allow_forgery_protection
end
end
end
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