Class CGI::Session::CookieStore
In: lib/action_controller/session/cookie_store.rb
Parent: Object

This cookie-based session store is the Rails default. Sessions typically contain at most a user_id and flash message; both fit within the 4K cookie size limit. Cookie-based sessions are dramatically faster than the alternatives.

If you have more than 4K of session data or don‘t want your data to be visible to the user, pick another session store.

CookieOverflow is raised if you attempt to store more than 4K of data. TamperedWithCookie is raised if the data integrity check fails.

A message digest is included with the cookie to ensure data integrity: a user cannot alter his user_id without knowing the secret key included in the hash. New apps are generated with a pregenerated secret in config/environment.rb. Set your own for old apps you‘re upgrading.

Session options:

  • :secret: An application-wide key string or block returning a string called per generated digest. The block is called with the CGI::Session instance as an argument. It‘s important that the secret is not vulnerable to a dictionary attack. Therefore, you should choose a secret consisting of random numbers and letters and more than 30 characters. Examples:
      :secret => '449fe2e7daee471bffae2fd8dc02313d'
      :secret => Proc.new { User.current_user.secret_key }
    
  • :digest: The message digest algorithm used to verify session integrity defaults to ‘SHA1’ but may be any digest provided by OpenSSL, such as ‘MD5’, ‘RIPEMD160’, ‘SHA256’, etc.

To generate a secret key for an existing application, run "rake secret" and set the key in config/environment.rb.

Note that changing digest or secret invalidates all existing sessions!

Methods

Classes and Modules

Class CGI::Session::CookieStore::CookieOverflow
Class CGI::Session::CookieStore::TamperedWithCookie

Constants

MAX = 4096   Cookies can typically store 4096 bytes.
SECRET_MIN_LENGTH = 30

Public Class methods

Public Instance methods

Write the session data cookie if it was loaded and has changed.

Delete the session data by setting an expired cookie with no data.

To prevent users from using something insecure like "Password" we make sure that the secret they‘ve provided is at least 30 characters in length.

Generate the HMAC keyed message digest. Uses SHA1 by default.

Restore session data from the cookie.

Wait until close to write the session data cookie.

[Validate]