jcoffey-dev
f72c67864e
The server writes to one path and no other: SESSION_FILE, from sessions.ts. Everything else it touches on disk it only reads. So a container with a read-only root filesystem already works -- except that `VOLUME ["/data"]` quietly undid it. Docker acts on that directive: a container started without `-v` gets an anonymous volume mounted there anyway, writable even under `--read-only`. It persisted nothing across a redeploy, since each new container got a fresh empty volume, and it left an orphan behind every time one was replaced. Deployments that want the sessions to survive already say so themselves -- docker-compose.yml and deploy.example.sh both mount a named volume -- so removing the line changes nothing for them. IMMUTABLE=1 asserts that this is how the instance is running. It is checked rather than believed: the server refuses to start if SESSION_FILE is still set, or if the filesystem it is installed on turns out to be writable. Left unchecked the misconfiguration is silent, because persisting sessions is best-effort -- a read-only /data costs one warning at the first sign-in and nothing more until the instance is replaced and everyone is signed out. SessionBackend names what the rest of the server asks of a session store, and `sessions` in app.ts is typed as it. Nothing changes today; SessionStore is still the only implementation. It is there so the OAuth work is written against the interface rather than the class, and so the interface can record which of its methods a stateless backend could satisfy alone: create, resolve, reseal and destroy each touch one session, while listForUser and destroyAllForUser have to reach sessions other than the caller's. The second of those carries the guarantee that changing a password invalidates the sessions still holding the old one, which is why it needs a registry -- Stalwart's token registry, once sign-in goes through OAuth.