The roads I take...

As mentioned previously here on my blog, my FOSDEM 2017 talk ended up opening up the code for my own OAuth2 login server which I created following my earlier post on the login systems question.

The video from the talk is now online at the details page of the talk (including downloadable versions if you want them), my slides are available as well.

The gist of it is that I found out that using a standard authentication protocol in my website/CMS systems instead of storing passwords with the websites is a good idea, but I also didn't want to report who is logging into which website at what point to a third party that I don't completely trust privacy-wise (like Facebook or Google). My way to deal with that was to operate my own OAuth2 login server, preferably with open code that I can understand myself.

As the language I know best is PHP (and I can write pretty clean and good quality code in that language), I looked for existing solutions there but couldn't find a finished one that I could just install, adapt branding-wise and operate.
I found a good library for OAuth2 (and by extension OpenID Connect) in oauth2-server-php, but the management of actual login processes and creating the various end points that call the library still had to be added, and so I set out to do just that. For storing passwords, I investigated what solutions would be good and in the end settled for using PHP's builtin password_hash function including its auto-upgrade-on-login functionalities, right now that means using bcrypt (which is decent but not fully ideal), with PHP 7.2, it will move to Argon2 (which is probably the best available option right now). That said, I wrote some code to add an on-disk random value to the passwords so that hacking the database alone will be insufficient for an offline brute-force attack on the hashes. In general, I tried to use a lot of advice from Mozilla's secure coding guidelines for websites, and also made sure my server passes with A+ score on Mozilla Observatory as well as SSL Labs, and put the changes for that in the code as much as possible, or example server configurations in the repository otherwise, so that other installations can profit from this as well.
For sending emails and building up HTML as DOM doucuments, I'm using helper classes from my own php-utility-classes and for some of the database access, esp. schema upgrades, I ended up including doctrine DBAL. Optionally, the code is there to monitor traffic via Piwik.

The code for all this is now available at https://github.com/KaiRo-at/authserver.

It should be relatively easy to install on a Linux system with Apache and MySQL - other web servers and databases should not be hard to add but are untested so far. The main README has some rudimentary documentation, but help is needed to improve on that. Also, all testing is done by trying logins with the two OAuth2 implementations I have done in my own projects, I need help in getting a real test suite set up for the system.
Right now, all the system supports is the OAuth2 "Authorization Code" flow, it would be great to extend it to support OIDC as well, which php-server-php can handle but the support code for it needs to be written.
Branding can easily be adapted for the operator running the service via the skin support (my own branding on my installation builds on that as well), and right now US English and German are supported by the service but more can easily be added if someone contributes them.

And last but not least, it's all under the MPL2 license, which I hope enables people easily to contribute - I hope including yourself!