1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
137
138
139
140
141
142
143
144
145
146
147
148
149
150
151
152
153
154
155
156
157
158
159
160
161
162
163
164
165
166
167
168
169
170
171
172
173
174
175
176
177
178
179
180
181
182
183
184
185
186
187
188
189
190
191
192
193
194
195
196
197
198
199
200
201
202
203
204
205
206
207
|
require 'rack/session/abstract/id'
require 'action_controller/metal/exceptions'
module ActionController #:nodoc:
class InvalidAuthenticityToken < 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). Also, GET requests are not protected as these
# should be idempotent.
#
# 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 FooController < ApplicationController
# protect_from_forgery except: :index
#
# You can disable csrf protection on controller-by-controller basis:
#
# skip_before_action :verify_authenticity_token
#
# It can also be disabled for specific controller actions:
#
# skip_before_action :verify_authenticity_token, except: [:create]
#
# 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
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
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
def handle_unverified_request
forgery_protection_strategy.new(self).handle_unverified_request
end
# The actual before_action that is used. Modify this to change how you handle unverified requests.
def verify_authenticity_token
unless verified_request?
logger.warn "Can't verify CSRF token authenticity" if logger
handle_unverified_request
end
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
|
