Publish CRL for the unprivileged OpenVPN user so crl_verify works

- ovpmon-helper: new publish-crl command (validated copy of pki/crl.pem to
  /etc/openvpn/crl.pem, root:root 644); crl-verify allowlisted only for
  that path; CRL is refreshed on service start/restart.
- Profiler: publish after gen-crl (init/revoke) and on server/configure;
  generator renders the published path when running unprivileged.
- doas rule for publish-crl; docs and helper copy updated.

Co-Authored-By: Claude Sonnet 5.5 <noreply@anthropic.com>

DOCS/Changes/2026-09-30_Privilege_Separation.md

@@ -7,10 +7,11 @@ Problem: `ovpmon-api`, `ovpmon-gatherer` and `ovpmon-profiler` ran as root. Any
 ```
 ovpmon-api / gatherer / profiler  (user ovpmon, no login shell)
         |
-        |  doas -n /usr/local/sbin/ovpmon-helper <fixed args>     (only 5 exact commands allowed)
+        |  doas -n /usr/local/sbin/ovpmon-helper <fixed args>     (only 6 exact commands allowed)
         v
 ovpmon-helper (root)  ->  install-config : validates the staged server.conf against an allowlist,
                                             installs /etc/openvpn/server.conf atomically
+                      ->  publish-crl : copies pki/crl.pem to /etc/openvpn/crl.pem (root:root 644)
                       ->  service start|stop|restart|status : rc-service openvpn
 ```
 
@@ -49,6 +50,28 @@ Only the directives the template produces, each with checked arguments: `dev tun
 ## Limitations / notes
 - The supervisors stay root by design (they only respawn the service user's process).
 - Helper checks resolve PKI paths at install time; a service-user-owned PKI directory could later swap a file for a symlink before OpenVPN (root) starts. Impact is limited to OpenVPN failing to parse or reading a key/cert-shaped file; keep the PKI directory owned by `ovpmon` only.
-- With `crl_verify` enabled the unprivileged OpenVPN user (`nobody`) must be able to read `crl.pem`, but `easy-rsa` creates `pki/` as `700`. Either keep CRL checking off or publish a copy of `crl.pem` to a root-owned, world-readable location (not automated yet).
+- CRL checking (`crl_verify`) works with the unprivileged API, see the section below.
 - systemd deployments: same idea with `User=ovpmon`, a polkit/sudoers rule for the helper's fixed commands, and the same helper (replace `rc-service` with `systemctl`).
 - Rollback: restore `/etc/init.d/ovpmon-*` from `/root/app-bak/p2/`, `chown -R root:root` the data directories, restart the services (the helper and doas rules can stay).
+
+## CRL publishing (`crl_verify`)
+
+OpenVPN drops to `nobody` after start and re-reads the CRL on each new connection. `easy-rsa` creates `pki/` as `0700` owned by the service user, so `nobody` could not read `pki/crl.pem` and every client would be refused once `crl_verify` was enabled.
+
+| Item | Detail |
+|---|---|
+| Published copy | `/etc/openvpn/crl.pem`, `root:root 644`, written atomically by `ovpmon-helper publish-crl` |
+| Helper checks | source must resolve inside the PKI directory, regular file (no symlink) owned by the service user, at most 1 MiB, PEM CRL markers, and `openssl crl` must parse it |
+| When it runs | after `gen-crl` in *Initialize PKI* and in *revoke* (`services/pki.py`, if publishing fails the revoke call reports an error instead of silently leaving the old CRL), on *server/configure* (an error only when `crl_verify` is on) and on every helper `service start\|restart` |
+| Config | with an unprivileged API the generator renders `crl-verify /etc/openvpn/crl.pem`; as root/in a container it still uses `pki/crl.pem`. The helper allowlist accepts only the published path for `crl-verify` |
+| doas | one more exact rule: `args publish-crl` |
+
+Results (throw-away second OpenVPN instance on another port/subnet running as `nobody` with the same PKI and `crl-verify /etc/openvpn/crl.pem`; production OpenVPN untouched):
+
+| Check | Result |
+|---|---|
+| `publish-crl` as `ovpmon` | ok; copy is `root:root 644`, readable by `nobody`; `pki/crl.pem` still unreadable by `nobody` |
+| Garbage file, fake PEM markers, symlinked source | rejected |
+| `crl_verify=true` via API + `server/configure` | 200; config contains `crl-verify /etc/openvpn/crl.pem`, accepted by the helper; setting restored afterwards, live `server.conf` byte-identical to the original |
+| Valid client with active CRL check | connects (`Initialization Sequence Completed`) |
+| Revoke through the API, then reconnect | server sends `certificate revoked`, client is refused; no CRL read errors |