ayurishchev/OpenVPN-Monitoring-Simple
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Run API services unprivileged; add root helper for OpenVPN config and service control

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- Profiler: when not root, render server.conf to the staging dir and let
  the root helper validate (directive allowlist) and install it; control
  the openvpn service through the helper (doas, fixed commands).
- Add ovpmon-helper and doas rules under DOCS/General/privilege-separation.
- Document the design, rollout, results and limitations.

Co-Authored-By: Claude Sonnet 5.5 <noreply@anthropic.com>
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iclaoudezinandClaude Sonnet 5.5 committed 2026-09-30 12:33:15 +00:00
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DOCS/Changes/2026-09-30_Privilege_Separation.md
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# Privilege separation: API services no longer run as root (2026-09-30)
Problem: `ovpmon-api`, `ovpmon-gatherer` and `ovpmon-profiler` ran as root. Any bug in an API (or a stolen admin token combined with an input-validation gap) meant root on the host.
## Design
```
ovpmon-api / gatherer / profiler (user ovpmon, no login shell)
|
| doas -n /usr/local/sbin/ovpmon-helper <fixed args> (only 5 exact commands allowed)
v
ovpmon-helper (root) -> install-config : validates the staged server.conf against an allowlist,
installs /etc/openvpn/server.conf atomically
-> service start|stop|restart|status : rc-service openvpn
```
| Item | Detail |
|---|---|
| Service user | `ovpmon` (system user, nologin), owns `/var/lib/ovpmon` (DBs, `staging/`), `/var/log/ovpmon`, `APP_PROFILER/{easy-rsa,client-config,profiler.log}`, runtime logs and `__pycache__`. Code and virtualenvs stay root-owned (read-only for the service) |
| OpenRC | `command_user="ovpmon:ovpmon"` in the three `ovpmon-*` init scripts; `/etc/ovpmon/env` stays `root:root 600` (read by the init script before the privilege drop) |
| doas | `/etc/doas.d/ovpmon.conf`: `permit nopass ovpmon as root cmd /usr/local/sbin/ovpmon-helper args <install-config \| service start\|stop\|restart\|status>`; nothing else is permitted |
| Helper | `/usr/local/sbin/ovpmon-helper` (root, 755). Source: `DOCS/General/privilege-separation/ovpmon-helper` |
| Profiler code | `services/process.py`: when not root, calls the helper (`_run_helper`, `install_config`); `routers/server.py`: renders to `/var/lib/ovpmon/staging/server.conf`, then asks the helper to install it (rejection → HTTP 400). Container and root paths are unchanged |
| Status log | the helper sets `root:ovpmon 640` on `openvpn-status.log` before every start/restart so the gatherer can read it |
### What the helper allows in `server.conf`
Only the directives the template produces, each with checked arguments: `dev tun`, `proto`, `port`, `ca/cert/key/dh/tls-auth/crl-verify` (files must resolve inside the PKI directory), `tun-mtu`, `mssfix`, `topology subnet`, `server`, fixed `ifconfig-pool-persist`, `log`, `log-append`, `status`, `verb`, `push` (only `redirect-gateway def1 bypass-dhcp`, `route <net>`, `dhcp-option DNS <ip>`), `user nobody`, `group nogroup`, ciphers/auth/keepalive, `client-to-client`, `duplicate-cn`, `persist-*`, `script-security 2`, `client-connect/disconnect` (script must be root-owned, not group/other-writable, directly in `/etc/openvpn/scripts/`), `management` (loopback only). Everything else (`up`, `down`, `plugin`, `route-up`, `tls-verify`, `setenv`, `config`, ...) is rejected. `user nobody`, `group nogroup`, `server`, `ca`, `cert`, `key` are mandatory. The file is read once (no TOCTOU between check and install), must be an `ovpmon`-owned regular file (no symlinks), ASCII only, at most 64 KiB.
## Rollout (what was done)
1. Backup: `/root/backup-p2-*.tar` (`/etc/openvpn`, `/var/lib/ovpmon`, `easy-rsa`, `client-config`, init scripts, doas config, changed code) and `/root/app-bak/p2/`.
2. Create the user/group, install the helper and the doas rules; test the helper as `ovpmon` before touching services.
3. Patch `process.py` / `server.py` (root code path unchanged, so nothing changed while services still ran as root).
4. `chown` runtime data, add `command_user`, restart the gatherer, then the API, then the profiler, checking each.
## Results
| Check | Result |
|---|---|
| Processes | gunicorn, uvicorn and the gatherer run as `ovpmon`; only the `supervise-daemon` supervisors are root |
| Helper: current live config | accepted, live `server.conf` byte-identical |
| Helper: 17 injected directives (`up`, `plugin`, `script-security 3`, `client-connect /tmp/x`, `route-up`, `tls-verify`, `setenv`, `config`, `ca /etc/shadow`, `management 0.0.0.0`, `log /etc/passwd`, `user root`, `status /etc/cron.d/x`, `push "setenv-safe"`, `dev tap`, multi-argument `push`) | all rejected, live config unchanged |
| Helper: missing `user nobody`, cert outside PKI, CR injection, symlinked staged file | rejected |
| doas: arbitrary command, helper with other args | denied |
| Service user cannot | read `/etc/shadow`, `/root`, `/etc/hysteria/*.yaml`, `/etc/ovpmon/env`; write `/etc/openvpn`, `/etc/init.d`, `authorized_keys`, application code; run `iptables` |
| API: monitoring, config, process stats, `server/configure` via helper (config identical) | 200 |
| API: create profile (easyrsa), download `.ovpn`, revoke | 200 |
| API: OpenVPN restart through the helper | 200; OpenVPN running, `tun0` up, status log readable by the gatherer, egress rules (`ip rule 102`, MASQUERADE to `hytun`) intact, no gatherer errors |
## 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).
- 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).