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Module: ActionController::RequestForgeryProtection

Overview

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. 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 <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 requests for JavaScript responses.

Subclasses of Base are protected by default with the :exception strategy, which raises an InvalidAuthenticityToken error on unverified requests.

APIs may want to disable this behavior since they are typically designed to be state-less: that is, the request API client handles the session instead of ::Rails. One way to achieve this is to use the :null_session strategy instead, which allows unverified requests to be handled, but with an empty session:

class ApplicationController < ActionController::Base
  protect_from_forgery with: :null_session
end

Note that API only applications don’t include this module or a session middleware by default, and so don’t require CSRF protection to be configured.

The token parameter is named authenticity_token by default. The name and value of this token must be added to every layout that renders forms by including csrf_meta_tags in the HTML head.

Learn more about CSRF attacks and securing your application in the [Ruby on ::Rails Security Guide](guides.rubyonrails.org/security.html).

Constant Summary

::ActiveSupport::Callbacks - Included

CALLBACK_FILTER_TYPES

::AbstractController::Callbacks - Attributes & Methods

::AbstractController::Helpers - Attributes & Methods

Class Method Summary

::ActiveSupport::DescendantsTracker - self

descendants, subclasses, clear, disable_clear!, reject!

::ActiveSupport::Concern - Extended

class_methods

Define class methods from given block.
included

Evaluate given block in context of base class, so that you can write class macros here.
prepended

Evaluate given block in context of base class, so that you can write class macros here.
append_features, prepend_features

Instance Attribute Summary

::AbstractController::Callbacks - Included

#__callbacks, #__callbacks?

Instance Method Summary

::AbstractController::Callbacks - Included

#process_action

Override AbstractController::Base#process_action to run the process_action callbacks around the normal behavior.

::ActiveSupport::Callbacks - Included

#run_callbacks

Runs the callbacks for the given event.
#halted_callback_hook

A hook invoked every time a before callback is halted.

::AbstractController::Helpers - Included

#_helpers

DSL Calls

included

[ GitHub ] 


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# File 'actionpack/lib/action_controller/metal/request_forgery_protection.rb', line 71

included do
  # Sets the token parameter name for RequestForgery. Calling
  # `protect_from_forgery` sets it to `:authenticity_token` 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?

  # Controls whether a CSRF failure logs a warning. On by default.
  config_accessor :log_warning_on_csrf_failure
  self.log_warning_on_csrf_failure = true

  # Controls whether the Origin header is checked in addition to the CSRF token.
  config_accessor :forgery_protection_origin_check
  self.forgery_protection_origin_check = false

  # Controls whether form-action/method specific CSRF tokens are used.
  config_accessor :per_form_csrf_tokens
  self.per_form_csrf_tokens = false

  # The strategy to use for storing and retrieving CSRF tokens.
  config_accessor :csrf_token_storage_strategy
  self.csrf_token_storage_strategy = SessionStore.new

  helper_method :form_authenticity_token
  helper_method :protect_against_forgery?
end

Class Attribute Details

._helper_methods (rw)

[ GitHub ] 

  


# File 'actionpack/lib/abstract_controller/helpers.rb', line 13



class_attribute :_helper_methods, default: Array.new


  








  

    ._helper_methods?  ⇒ Boolean  (rw)
  

  [ GitHub ]


  

  


# File 'actionpack/lib/abstract_controller/helpers.rb', line 13



class_attribute :_helper_methods, default: Array.new


  








  

    .raise_on_missing_callback_actions   (rw)
    Also known as: #raise_on_missing_callback_actions
  

  [ GitHub ]


  

  


# File 'actionpack/lib/abstract_controller/callbacks.rb', line 36



mattr_accessor :raise_on_missing_callback_actions, default: false


  







Instance Attribute Details



  

    #_helper_methods   (rw)
  

  [ GitHub ]


  

  


# File 'actionpack/lib/abstract_controller/helpers.rb', line 13



class_attribute :_helper_methods, default: Array.new


  








  

    #_helper_methods?  ⇒ Boolean  (rw)
  

  [ GitHub ]


  

  


# File 'actionpack/lib/abstract_controller/helpers.rb', line 13



class_attribute :_helper_methods, default: Array.new


  








  

    #any_authenticity_token_valid?  ⇒ Boolean  (readonly, private)
  



  

    

Checks if any of the authenticity tokens from the request are valid.


  





  


  [ GitHub ]


  

  


# File 'actionpack/lib/action_controller/metal/request_forgery_protection.rb', line 468



def any_authenticity_token_valid? # :doc:
  request_authenticity_tokens.any? do |token|
    valid_authenticity_token?(session, token)
  end
end


  








  

    #marked_for_same_origin_verification?  ⇒ Boolean  (readonly, private)
  



  

    

If the #verify_authenticity_token before_action ran, verify that JavaScript responses are only served to same-origin GET requests.


  





  


  [ GitHub ]


  

  


# File 'actionpack/lib/action_controller/metal/request_forgery_protection.rb', line 444



def marked_for_same_origin_verification? # :doc:
  @_marked_for_same_origin_verification ||= false
end


  








  

    #non_xhr_javascript_response?  ⇒ Boolean  (readonly, private)
  



  

    

Check for cross-origin JavaScript responses.


  





  


  [ GitHub ]


  

  


# File 'actionpack/lib/action_controller/metal/request_forgery_protection.rb', line 449



def non_xhr_javascript_response? # :doc:
  %r(\A(?:text|application)/javascript).match?(media_type) && !request.xhr?
end


  








  

    #protect_against_forgery?  ⇒ Boolean  (readonly, private)
  



  

    

Checks if the controller allows forgery protection.


  





  


  [ GitHub ]


  

  


# File 'actionpack/lib/action_controller/metal/request_forgery_protection.rb', line 611



def protect_against_forgery? # :doc:
  allow_forgery_protection && (!session.respond_to?(:enabled?) || session.enabled?)
end


  








  

    #raise_on_missing_callback_actions   (rw)
  

  [ GitHub ]


  

  


# File 'actionpack/lib/abstract_controller/callbacks.rb', line 36



mattr_accessor :raise_on_missing_callback_actions, default: false


  








  

    #valid_request_origin?  ⇒ Boolean  (readonly, private)
  



  

    

Checks if the request originated from the same origin by looking at the Origin header.


  





  


  [ GitHub ]


  

  


# File 'actionpack/lib/action_controller/metal/request_forgery_protection.rb', line 626



def valid_request_origin? # :doc:
  if forgery_protection_origin_check
    # We accept blank origin headers because some user agents don't send it.
    raise InvalidAuthenticityToken, NULL_ORIGIN_MESSAGE if request.origin == "null"
    request.origin.nil? || request.origin == request.base_url
  else
    true
  end
end


  








  

    #verified_request?  ⇒ Boolean  (readonly, private)
  



  

    

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?
    



  





  


  [ GitHub ]


  

  


# File 'actionpack/lib/action_controller/metal/request_forgery_protection.rb', line 462



def verified_request? # :doc:
  !protect_against_forgery? || request.get? || request.head? ||
    (valid_request_origin? && any_authenticity_token_valid?)
end


  







Instance Method Details



  

    #commit_csrf_token(request)  
  

  [ GitHub ]


  

  


# File 'actionpack/lib/action_controller/metal/request_forgery_protection.rb', line 374



def commit_csrf_token(request) # :doc:
  csrf_token = request.env[CSRF_TOKEN]
  csrf_token_storage_strategy.store(request, csrf_token) unless csrf_token.nil?
end


  








  

    #compare_with_global_token(token, session = nil)   (private)
  

  [ GitHub ]


  

  


# File 'actionpack/lib/action_controller/metal/request_forgery_protection.rb', line 549



def compare_with_global_token(token, session = nil) # :doc:
  ActiveSupport::SecurityUtils.fixed_length_secure_compare(token, global_csrf_token(session))
end


  








  

    #compare_with_real_token(token, session = nil)   (private)
  

  [ GitHub ]


  

  


# File 'actionpack/lib/action_controller/metal/request_forgery_protection.rb', line 545



def compare_with_real_token(token, session = nil) # :doc:
  ActiveSupport::SecurityUtils.fixed_length_secure_compare(token, real_csrf_token(session))
end


  








  

    #csrf_token_hmac(session, identifier)   (private)
  

  [ GitHub ]


  

  


# File 'actionpack/lib/action_controller/metal/request_forgery_protection.rb', line 586



def csrf_token_hmac(session, identifier) # :doc:
  OpenSSL::HMAC.digest(
    OpenSSL::Digest::SHA256.new,
    real_csrf_token(session),
    identifier
  )
end


  








  

    #decode_csrf_token(encoded_csrf_token)   (private)
  

  

    This method is for internal use only.
  

  [ GitHub ]


  

  


# File 'actionpack/lib/action_controller/metal/request_forgery_protection.rb', line 664



def decode_csrf_token(encoded_csrf_token) # :nodoc:
  Base64.urlsafe_decode64(encoded_csrf_token)
end


  








  

    #encode_csrf_token(csrf_token)   (private)
  

  

    This method is for internal use only.
  

  [ GitHub ]


  

  


# File 'actionpack/lib/action_controller/metal/request_forgery_protection.rb', line 660



def encode_csrf_token(csrf_token) # :nodoc:
  Base64.urlsafe_encode64(csrf_token, padding: false)
end


  








  

    #form_authenticity_param   (private)
  



  

    

The form’s authenticity parameter. Override to provide your own.


  



  [ GitHub ]


  

  


# File 'actionpack/lib/action_controller/metal/request_forgery_protection.rb', line 606



def form_authenticity_param # :doc:
  params[request_forgery_protection_token]
end


  








  

    #form_authenticity_token(form_options: {})   (private)
  



  

    

Creates the authenticity token for the current request.


  



  [ GitHub ]


  

  


# File 'actionpack/lib/action_controller/metal/request_forgery_protection.rb', line 480



def form_authenticity_token(form_options: {}) # :doc:
  masked_authenticity_token(form_options: form_options)
end


  








  

    #generate_csrf_token   (private)
  

  

    This method is for internal use only.
  

  [ GitHub ]


  

  


# File 'actionpack/lib/action_controller/metal/request_forgery_protection.rb', line 656



def generate_csrf_token # :nodoc:
  SecureRandom.urlsafe_base64(AUTHENTICITY_TOKEN_LENGTH)
end


  








  

    #global_csrf_token(session = nil)   (private)
  

  [ GitHub ]


  

  


# File 'actionpack/lib/action_controller/metal/request_forgery_protection.rb', line 582



def global_csrf_token(session = nil) # :doc:
  csrf_token_hmac(session, GLOBAL_CSRF_TOKEN_IDENTIFIER)
end


  








  

    #handle_unverified_request   (private)
  

  [ GitHub ]


  

  


# File 'actionpack/lib/action_controller/metal/request_forgery_protection.rb', line 399



def handle_unverified_request # :doc:
  protection_strategy = forgery_protection_strategy.new(self)

  if protection_strategy.respond_to?(:warning_message)
    protection_strategy.warning_message = unverified_request_warning_message
  end

  protection_strategy.handle_unverified_request
end


  








  

    #initialize  
  

  [ GitHub ]


  

  


# File 'actionpack/lib/action_controller/metal/request_forgery_protection.rb', line 364



def initialize(...)
  super
  @_marked_for_same_origin_verification = nil
end


  








  

    #mark_for_same_origin_verification!   (private)
  



  

    

GET requests are checked for cross-origin JavaScript after rendering.


  



  [ GitHub ]


  

  


# File 'actionpack/lib/action_controller/metal/request_forgery_protection.rb', line 438



def mark_for_same_origin_verification! # :doc:
  @_marked_for_same_origin_verification = request.get?
end


  








  

    #mask_token(raw_token)   (private)
  

  [ GitHub ]


  

  


# File 'actionpack/lib/action_controller/metal/request_forgery_protection.rb', line 538



def mask_token(raw_token) # :doc:
  one_time_pad = SecureRandom.random_bytes(AUTHENTICITY_TOKEN_LENGTH)
  encrypted_csrf_token = xor_byte_strings(one_time_pad, raw_token)
  masked_token = one_time_pad + encrypted_csrf_token
  encode_csrf_token(masked_token)
end


  








  

    #masked_authenticity_token(form_options: {})   (private)
  



  

    

Creates a masked version of the authenticity token that varies on each request. The masking is used to mitigate SSL attacks like BREACH.


  



  [ GitHub ]


  

  


# File 'actionpack/lib/action_controller/metal/request_forgery_protection.rb', line 486



def masked_authenticity_token(form_options: {})
  action, method = form_options.values_at(:action, :method)

  raw_token = if per_form_csrf_tokens && action && method
    action_path = normalize_action_path(action)
    per_form_csrf_token(nil, action_path, method)
  else
    global_csrf_token
  end

  mask_token(raw_token)
end


  








  

    #normalize_action_path(action_path)   (private)
  

  [ GitHub ]


  

  


# File 'actionpack/lib/action_controller/metal/request_forgery_protection.rb', line 636



def normalize_action_path(action_path) # :doc:
  uri = URI.parse(action_path)

  if uri.relative? && (action_path.blank? || !action_path.start_with?("/"))
    normalize_relative_action_path(uri.path)
  else
    uri.path.chomp("/")
  end
end


  








  

    #normalize_relative_action_path(rel_action_path)   (private)
  

  [ GitHub ]


  

  


# File 'actionpack/lib/action_controller/metal/request_forgery_protection.rb', line 646



def normalize_relative_action_path(rel_action_path) # :doc:
  uri = URI.parse(request.path)
  # add the action path to the request.path
  uri.path += "/#{rel_action_path}"
  # relative path with "./path"
  uri.path.gsub!("/./", "/")

  uri.path.chomp("/")
end


  








  

    #per_form_csrf_token(session, action_path, method)   (private)
  

  [ GitHub ]


  

  


# File 'actionpack/lib/action_controller/metal/request_forgery_protection.rb', line 575



def per_form_csrf_token(session, action_path, method) # :doc:
  csrf_token_hmac(session, [action_path, method.downcase].join("#"))
end


  








  

    #real_csrf_token(_session = nil)   (private)
  

  [ GitHub ]


  

  


# File 'actionpack/lib/action_controller/metal/request_forgery_protection.rb', line 567



def real_csrf_token(_session = nil) # :doc:
  csrf_token = request.env.fetch(CSRF_TOKEN) do
    request.env[CSRF_TOKEN] = csrf_token_storage_strategy.fetch(request) || generate_csrf_token
  end

  decode_csrf_token(csrf_token)
end


  








  

    #request_authenticity_tokens   (private)
  



  

    

Possible authenticity tokens sent in the request.


  



  [ GitHub ]


  

  


# File 'actionpack/lib/action_controller/metal/request_forgery_protection.rb', line 475



def request_authenticity_tokens # :doc:
  [form_authenticity_param, request.x_csrf_token]
end


  








  

    #reset_csrf_token(request)  
  

  [ GitHub ]


  

  


# File 'actionpack/lib/action_controller/metal/request_forgery_protection.rb', line 369



def reset_csrf_token(request) # :doc:
  request.env.delete(CSRF_TOKEN)
  csrf_token_storage_strategy.reset(request)
end


  








  

    #unmask_token(masked_token)   (private)
  

  [ GitHub ]


  

  


# File 'actionpack/lib/action_controller/metal/request_forgery_protection.rb', line 531



def unmask_token(masked_token) # :doc:
  # Split the token into the one-time pad and the encrypted value and decrypt it.
  one_time_pad = masked_token[0...AUTHENTICITY_TOKEN_LENGTH]
  encrypted_csrf_token = masked_token[AUTHENTICITY_TOKEN_LENGTH..-1]
  xor_byte_strings(one_time_pad, encrypted_csrf_token)
end


  








  

    #unverified_request_warning_message   (private)
  

  

    This method is for internal use only.
  

  [ GitHub ]


  

  


# File 'actionpack/lib/action_controller/metal/request_forgery_protection.rb', line 409



def unverified_request_warning_message # :nodoc:
  if valid_request_origin?
    "Can't verify CSRF token authenticity."
  else
    "HTTP Origin header (#{request.origin}) didn't match request.base_url (#{request.base_url})"
  end
end


  








  

    #valid_authenticity_token?(session, encoded_masked_token)  ⇒ Boolean  (private)
  



  

    

Checks the client’s masked token to see if it matches the session token. Essentially the inverse of #masked_authenticity_token.


  





  


  [ GitHub ]


  

  


# File 'actionpack/lib/action_controller/metal/request_forgery_protection.rb', line 501



def valid_authenticity_token?(session, encoded_masked_token) # :doc:
  if encoded_masked_token.nil? || encoded_masked_token.empty? || !encoded_masked_token.is_a?(String)
    return false
  end

  begin
    masked_token = decode_csrf_token(encoded_masked_token)
  rescue ArgumentError # encoded_masked_token is invalid Base64
    return false
  end

  # See if it's actually a masked token or not. In order to deploy this code, we
  # should be able to handle any unmasked tokens that we've issued without error.

  if masked_token.length == AUTHENTICITY_TOKEN_LENGTH
    # This is actually an unmasked token. This is expected if you have just upgraded
    # to masked tokens, but should stop happening shortly after installing this gem.
    compare_with_real_token masked_token

  elsif masked_token.length == AUTHENTICITY_TOKEN_LENGTH * 2
    csrf_token = unmask_token(masked_token)

    compare_with_global_token(csrf_token) ||
      compare_with_real_token(csrf_token) ||
      valid_per_form_csrf_token?(csrf_token)
  else
    false # Token is malformed.
  end
end


  








  

    #valid_per_form_csrf_token?(token, session = nil)  ⇒ Boolean  (private)
  



  

    
  





  


  [ GitHub ]


  

  


# File 'actionpack/lib/action_controller/metal/request_forgery_protection.rb', line 553



def valid_per_form_csrf_token?(token, session = nil) # :doc:
  if per_form_csrf_tokens
    correct_token = per_form_csrf_token(
      session,
      request.path.chomp("/"),
      request.request_method
    )

    ActiveSupport::SecurityUtils.fixed_length_secure_compare(token, correct_token)
  else
    false
  end
end


  








  

    #verify_authenticity_token   (private)
  



  

    

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.


  



  [ GitHub ]


  

  


# File 'actionpack/lib/action_controller/metal/request_forgery_protection.rb', line 389



def verify_authenticity_token # :doc:
  mark_for_same_origin_verification!

  if !verified_request?
    logger.warn unverified_request_warning_message if logger && log_warning_on_csrf_failure

    handle_unverified_request
  end
end


  








  

    #verify_same_origin_request   (private)
  



  

    

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.


  



  [ GitHub ]


  

  


# File 'actionpack/lib/action_controller/metal/request_forgery_protection.rb', line 428



def verify_same_origin_request # :doc:
  if marked_for_same_origin_verification? && non_xhr_javascript_response?
    if logger && log_warning_on_csrf_failure
      logger.warn CROSS_ORIGIN_JAVASCRIPT_WARNING
    end
    raise ActionController::InvalidCrossOriginRequest, CROSS_ORIGIN_JAVASCRIPT_WARNING
  end
end


  








  

    #xor_byte_strings(s1, s2)   (private)
  

  [ GitHub ]


  

  


# File 'actionpack/lib/action_controller/metal/request_forgery_protection.rb', line 594



def xor_byte_strings(s1, s2) # :doc:
  s2 = s2.dup
  size = s1.bytesize
  i = 0
  while i < size
    s2.setbyte(i, s1.getbyte(i) ^ s2.getbyte(i))
    i += 1
  end
  s2
end