django-ca is a feature rich certificate authority written in Python, using the django framework. The project exists for long, have great documentation and code comments all around. As I was looking around for possible CAs which can be used in multiple projects at work, django-ca seems to be a good base fit. Though it has still a few missing parts (which are important for us), for example HSM support and Certificate Management over CMS.

I started looking into the codebase of django-ca more and meanwhile also started cleaning up (along with Magnus Svensson) another library written at work for HSM support. I also started having conversion with Mathias (who is the author of django-ca) about this feature.

Thanks to the amazing design of the Python Cryptography team, I could just add several Private key implementations in our library, which in turn can be used as a normal private key.

I worked on a proof of concept branch (PoC), while getting a lot of tests also working.

===== 107 failed, 1654 passed, 32 skipped, 274 errors in 286.03s (0:04:46) =====

Meanwhile Mathias also started writing a separate feature branch where he is moving the key operations encapsulated inside of backends, and different backends can be implemented to deal with HSM or normal file based storage. He then chatted with me on Signal over 2 hours explaining the code and design of the branch he is working on. He also taught me many other django/typing things which I never knew before in the same call. His backend based approach makes my original intention of adding HSM support very easy. But, it also means at first he has to modify the codebase (and the thousands of test cases) first.

I am writing this blog post also to remind folks that not every piece of code needs to go to production (or even merged). I worked on a PoC, that validates the idea. And then we have a better and completely different design. It is perfectly okay to work hard for a PoC and later use a different approach.

As some friends asked on Mastodon, I will do a separate post about the cleanup of the other library.

How to get a TLS certificate for a domain inside of my local network? This was a question for me for a long time. I thought of creating a real subdomain, getting the certificate, and copying over the files locally, and then enforcing local domain names via the DNS or /etc/hosts. But, during the TLS training from Scott Helme, I learned about getting certificates via DNS challenge using acme.sh.

I use DreamHost nameservers for most of m domains. I got an API_KEY from them for only DNS manipulation.

Next, I just had to execute one single command along with the API_KEY to fetch fresh and hot certificate from Let's Encrypt.

The following command fetches for fire.das.community subdomain.

DH_API_KEY=MYAPIKEY acme.sh --issue --dns dns_dreamhost -d fire.das.community

There is a wiki page listing how to use acme.sh tool for various DNS providers.