What is the best way to handle sessions with ADR?

Right before Christmas, I reached out to Paul Jones asking:

I’ve reached a point with a couple of my Radar projects where I need to add a login and set permissions. I’m trying to figure out the best way to handle this, especially with PSR-7 and ADR.

This led to discussing how to do sessions properly in Radar. I had read Paul’s post PSR-7 and Session Cookies which discussed how to tweak PHP Sessions to work better in a PSR-7 architecture. You don’t really want PHP automatically sending and reading cookies outside of the Request object.

Paul responded:

Finally, the more I work with separated domain layer, the more I dislike the built-in PHP session system. Lately, I have started to consider avoiding it entirely, in favor of something like a custom DomainSession. Attached are my very rough notes-in-code; maybe they’ll be useful to you.

Needless to say, they have been very useful. Paul has been incredibly generous with his time and after going back and forth through several rounds of refactoring and revising I’m ready to officially announce Cadre.DomainSession. The current version as of this post is 0.4.0.

Why DomainSession?

The reason for this package is that as Paul had said: “Anything that touches storage should be considered domain-layer work.” so it’s ok to read the session cookie in an Input class, and it’s ok to write the cookie in a Responder class, but pretty much everything else should be in the Domain layer.

For more information about Radar see Radar Under the Hood.

What does it do?

Cadre.DomainSession takes a session id (or generates one) and loads session data from storage. It’s smart enough to handle regenerating session ids and cleaning up expired sessions.

Demo

I’ve put together a small demo app using Radar and Cadre.DomainSession at radar-domain-session.

Loading the Session ID From a Cookie

Reading the session ID from a cookie is handled in the Input of your route. I used the excellent library dflydev-fig-cookies to simplify getting and setting cookies in PSR-7.

In Application\Delivery\DefaultInput I read from the SESSION_ID cookie, returning null if it doesn’t exist.

Starting, Using and Finishing the Session

In Application\Domain\Home I first inject the Cadre\DomainSession\SessionManager. Then I start the session with the session ID I passed in from the Input. I check to see if there is a timestamp session value (Unknown if not present) and assign it with the current timestamp. Finally, I finish the session which is what persists the data to storage. In this case, it’s just to the filesystem. One important thing to note is that I have to return the session object in the payload for the final step.

If you want to regenerate the session ID you can do so by calling $session->getId()->regenerate().

Persisting the Session ID in a Cookie

In Application\Delivery\DefaultResponder I check to see if there was a session in the payload. If there is, I check to see if the session ID has been updated (new or regenerated session id). If it’s been updated I persist the session ID value to the session cookie I’m reading from in the Input and that’s all there is to it.

Concerns

I have some concerns with this library. The built-in session handling has withstood the test of time. It’s been looked at and I assume many security concerns have been fixed. I’m not a security expert, so I worry that there are vulnerabilities in my code.

In particular, I’m using what I consider to be a fairly naive method for generating session IDs.

I need to do some research and find if session_create_id would be a better method to use. I’m not sure if it just generates an ID or if it depends on the storage implementation.

Summary

When you’re using ADR, it’s important to be absolutely clear what is and isn’t part of your domain. Paul considers anything that touches storage as domain-layer work. Reading and writing cookies is an implementation detail that is part of the delivery mechanism. Imagine using the same domain objects in a command line application. You wouldn’t use cookies, but perhaps you would pass a session ID in as a command line argument.

What am I missing? Do you find this implementation useful? Let me know in the comments.

UPDATE: There is also an interesting conversation going over on Reddit.

Author: Andrew Shell

Madison, WI developer, Co-Founder and CTO of Pinpoint Software, founder of Madison PHP.

4 thoughts on “What is the best way to handle sessions with ADR?”

  1. Hi Andrew, nice article!

    Do you have any thoughts on how this could be used from a CLI environment? I would very much like to be able to have one ApplicationService (Application\Domain\Home in your example) that I can use in my web interface (where it reads from the session) but also in my CLI commands (where it uses the current *nix user, or defaults to full administrative access, or whatever). I don’t see how I can do that, without making the domain aware of what the source of interaction is though.

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