Given the session key and secret, how can we decrypt Rails cookies?

Question

I've got a question about how Rails handles cookie encryption/decryption.

I've got this in my config/environment.rb

  config.action_controller.session = {
    :session_key => [some key],
    :secret => [some secret]
  }

And this in config/environment/production.rb et al.:

  ActionController::Base.session_options[:session_domain] = [some
domain]

So far, so good -- as long as all my Rails apps have the same session_key and secret, and are on the same domain, they can all use that same cookie.

However, a colleague now has a JSP application (on the same domain), with which he'd like to read the cookies I have set.

So, given a secret and an encrypted cookie value, how would we decrypt it to get the contents of that cookie?

(The docs seem to indicate this is one-way SHA1 encryption by default -- http://caboo.se/doc/classes/CGI/Session/CookieStore.html -- but then how would my Rails applications read the contents of a cookie that is one-way encrypted?)

Thanks in advance for any tips/pointers/insight,

Joe

Answer 1

If you pull the session.data field straight from the session data stored in your app's database (if you are using active_record_store in your environment.rb file)

config.action_controller.session_store = :active_record_store

... here is how you decode it and return the hash:

Marshal.load(ActiveSupport::Base64.decode64(@session.data))

... or in Rails >= 3.2 (thanks Chuck Vose)

Marshal.load(Base64.decode64(@session.data))

It is not encrypted at all.