SessionExpirable¶ ↑

All good things come to an end: At least that’s how it’s supposed to work.

SessionExpirable is an enhanced version of Devise[https://github.com/plataformatec/devise]‘s timeoutable module that ensures that no session is allowed to last forever.

Like Devise timeoutable, SessionExpirable adds a timestamp to sessions indicating the last time that the session was used, and checks these timestamps when a session is used to sign a user in. A configurable timeout_in option controls how long inactive sessions are considered valid.

Differences with Devise Timeoutable¶ ↑

When timeoutable reads a session that does not contain a timestamp, timestamp validation is bypassed: A session without a timestamp will never be considered as having timed out.

In order to prevent the abuse of non-expiring sessions, SessionExpirable treats sessions without timestamps as having already expired.

Another difference is that in the case of a timeout, timeoutable prevents other authentication strategies from being tried, although it has custom logic to allow Devise rememberable to work in spite of a timed-out session.

SessionExpirable does not allow a timed-out session to interfere with any authentication strategies that are configured. One consequence is that SessionExpirable does not support invalidation of authentication tokens from the Devise token_authenticatable module when a request with a valid authentication token is accompanied by an expired session.

One final difference is that SessionExpirable does not invoke the Devise FailureApp for requests that do not require authentication.

Configuration¶ ↑

Add devise_session_expirable to your Gemfile:

gem 'devise_session_expirable'

Include :session_expirable in your devise user model declaration:

class User < ActiveRecord::Base
  devise :database_authenticatable, :session_expirable # ...
end

Then update the Devise initializer:

Devise.setup do |config|
  # ...
  config.timeout_in = 15.minutes
  config.default_last_request_at = Time.parse('2013-02-16T00:00:00Z')
  # ...
end

Migrating from non-expiring sessions¶ ↑

The default_last_request_at option is intended to enable a less disruptive migration if sessions without timestamps have already been issued. The configured value will be used in place of the timestamp for sessions which don’t have one.

If default_last_request_at is configured, it should be set to a fixed date/time, ideally matching the time of deployment. If set to a dynamic time (e.g. Time.now), the lifetime of sessions without timestamps will be extended every time Rails is initialized.

After the timeout_in interval passes, any legacy sessions will have expired and default_last_request_at can be unset.

Alternatives¶ ↑

As long as you reset your secret_token when configuring Devise timeoutable to your rails application and avoid authenticating for actions which set devise.skip_trackable in the rack environment, you will have eliminated at least two possible sources of non-expiring sessions.

Acknowledgements¶ ↑

This module was adapted from Devise’s timeoutable module.

Thanks to the creators and maintainers of Devise and Warden for a truly extensible authentication library.

Contributing to devise_session_expirable¶ ↑

• Fork the project.

• Start a feature/bugfix branch.

• Commit and push.

• Make sure to add tests.

Copyright¶ ↑

Copyright © 2013 Riley Lynch, Teleological Software, LLC. See LICENSE.txt for further details.