The middleware should be compatible with any framework using a recent version of Rack. It has been tested with Rack 2-3 and Rails 5.2-7.2.
The optional ActiveRecord Session Store extension requires Rails.
If using Rack < 2.0.9 or Rails < 5.2, use LimitedSessions 4.x.
No changes are required to upgrade from LimitedSessions 4.x to 5.0.
Add this gem to your Gemfile or otherwise make it available to your app. Then, configure as required.
-
If you don't already have an updated_at
column on your sessions table, create a migration and add it. If you plan to use the hard session limit feature, you'll also need to add created_at
.
-
Tell Rails to use your the new session store. Change config/initializers/session_store.rb
to reflect the following:
Rails.application.config.session_store :active_record_store
ActionDispatch::Session::ActiveRecordStore.session_class = LimitedSessions::SelfCleaningSession
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Configuration options.
Each of the following options should also be added to your initializer file from step 2.
Self-cleaning
By default, SelfCleaningSession will clean the sessions table every 1000 page views. Technically, it's a 1 in 1000 chance on each page. For most sites this is good. Higher traffic sites may want to increase it to 10000 or more. Set to 0 to disable self-cleaning.
LimitedSessions::SelfCleaningSession.self_clean_sessions = 1000
Session activity timeout
The default session activity timeout is 2 hours. This uses the updated_at
column which will be updated on every page load.
This can also be disabled by setting to nil
. However, the updated_at
column is still required for self-cleaning and will effectively function as if set to 1.week
. If you really want it longer, set it to 1.year
or something.
LimitedSessions::SelfCleaningSession.recent_activity = 2.hours
Maximum session length
By default, maximum session length handling is disabled. When enabled, it uses the created_at
column to do its work.
A value of nil
disables this feature and created_at
does not need to exist in this case.
LimitedSessions::SelfCleaningSession.max_session = 12.hours
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Do I need both the middleware and the ActiveRecord Session Store?
No. While it should work, it is not necessary to use both the middleware
and the ActiveRecord Session Store. If you are storing sessions via AR,
then use the ActiveRecord Session Store. If you are storing sessions any
other way, then use the middleware.
-
I'm storing sessions in {Memcache, Redis, etc.} and they auto-expire sessions. Do I need this?
Maybe, maybe not. Normally, that auto-expire period is equivalent to LimitedSessions' :recent_activity. If that's all you want, then you don't need this. However, if you'd also like to put a maximum cap on session length, regardless of activity, then LimitedSessions' :max_session
feature will still be useful.
-
Can I use the middleware with ActiveRecord instead of the ActionRecord Session Store enhancement?
Yes. Session expiry (recent activity and max session length) should work fine in this circumstance. The only thing you won't get is self-cleaning of the AR sessions table.
-
How are session expiry times tracked?
The middleware adds one or two keys to the session data: :last_visit
and/or :first_visit
.
The AR enhancement uses updated_at
and possibly created_at
.
-
How is this different from using the session cookie's own expires= value?
The cookie's own value puts the trust in the client to self-expire. If you really want to control session lengths, then you need to manage the values on the application side. LimitedSessions is fully compatible with the cookie's expires= value, however, and the two can be used together.
-
What's the difference between :recent_activity
and :max_session
?
Recent activity requires regular access on your site. If it's set to 15 minutes, then a page must be loaded at least once every 15 minutes.
Max session is a cap on the session from the very beginning. If it's set to 12 hours, then even if a user is accessing the page constantly, and not triggering the recent activity timeout, after 12 hours their session would be reset anyway.
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What are the security implications of using LimitedSessions?
LimitedSessions enhances security by reducing risk of session cookie replay attacks. The specifics will depend on what cookie store you're using.
For Rails' default cookie store, :max_session
handling is perhaps most valuable as it guarantees an end to the session. Rails' default behavior allows a session to last for an infinite time. If a cookie is somehow exposed, the holder of the cookie has an open-ended session. Note that signing and/or encryption do not mitigate this.
For any session store that uses a server-side database (AR, memcache, Redis, etc.), at least the user can formally logout and terminate the session. Auto-expiring sessions (memcache, Redis, AR w/SelfCleaningSession, etc.) will also expire if allowed to, but can also be maintained perpetually by ongoing access.
Since the cookie store doesn't expire ever, :recent_activity
addresses this by making sessions expire similarly to if memcache, Redis, or something similar was being used.
It is recommended to use both aspects of LimitedSessions for best security.
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What are the performance implications of using LimitedSessions?
The middleware should have minimal impact.
The AR enhancement should result in an overall net gain in performance as the size of the AR sessions table will be kept to a smaller size. The 1 in 1000 hit (or whatever you've configured it to) may be slightly slower while the database cleanup is in progress.