Journey to a distributed PDS: TOTP auth

Previously on Journey to a distributed PDS, I discovered that when one node generates the DPoP nonce that a client uses as part of a request and another node then receives that as part of a request to validate, it would fail because node one would have generated it differently than node 2. This was due to Cocoon using an incremental counter on a timer which would get used to generate and then validate a nonce. Each node would have a different counter and so they would both calculate different values.

I had a couple ideas on how to solve this, but wasn't really feeling them and thankfully Devin suggested a really good idea.

View post on Bluesky

Once I saw this I knew immediately that this would probably be the best solution and I was annoyed that I didn't think of it myself.

So off I went to implement it and it turned out to be pretty damn easy to do and it worked perfectly.

https://tangled.org/willdot.net/distributed-pds/pulls/4/round/0

There's the PR that I used and it's relatively straight forward.

Some things to note are:

A new env which contains the nonce secret (so that all nodes can generate the same nonce). Previously this was just a randomly generated value that was then stored to a local file so that it was consistent across restarts. No harm in making it an env.

A new nonce generator that instead of using an incremental counter, used a rounded time value. Currently it's hardcoded to 15 minute intervals because I need to do some testing on how small I can make that interval. The smaller the interval, the less time that a nonce value is valid for which tightens up the secureness of the value.

I've been using it like this for a few weeks and haven't had any issues so far. The past few days I've attempted to test with a small interval and managed to get it down to 1 minute which is what Cocoon was using for it's rotation before, so I expect I'll PR that soon.

I was really impressed how this solution turned out because I was actually dreading getting into the OAuth trenches to figure it out.

Side note:

I created a new fork of Cocoon and called it distributed-pds because I wanted to have everything all in one place and not clutter up the fork I had for Cocoon which I like to contribute from time to time. Feel free to give it a star and follow the progress. I'm currently in the middle of adding some documentation on how to run it in distributed mode.