03 §3.1: the controller-image write goes through a root verb (R-861 (a) A1); felhom-op's pct lines anchored (B2); decision 165

Co-Authored-By: Claude Opus 5.5 (1M context) <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_0159rPz1ZhFKsS53msqPYxtS

documentation/architecture/03-host-agent.md

@@ -110,11 +110,11 @@ fixed file, delivered by the signed config bundle):
 | `FELHOM_DNSMASQ` | the LAN split-horizon resolver | drop-ins via `felhom-priv-apply dnsmasq` (only `bind-interfaces`, `no-resolv`, `listen-address`, `server`, `local`, `address`); `rm` one exact name; exact `pct exec` reads | — |
 | `FELHOM_GUESTHOOK` | the pre-start self-heal hook | the hook is a FIXED bundle file; the agent only checks it (`SnippetReady`) and registers it; exact vmid/slot | — |
 | `FELHOM_INTERMEDIARY` | the shared drive parent + live drive binds | boot script + unit are FIXED bundle files (the agent only enables the unit); one-segment drive names (no leading dot, no `..`) | — |
-| `FELHOM_CONTROLLERSWAP` | the managed controller update | exact vmid; image ref pinned to `gitea.dooplex.hu/admin/felhom-controller:X.Y.Z` for the image check; the inspect template stays free text | **guest-scoped by design**: a compromised agent can still `tee` a chosen image ref and restart the guest's bootstrap — **any image from any registry**, because sudo cannot see the `tee` content on stdin and only the `inspect` line is pinned (corrected 2026-10-06 night, `audits/night-burndown-2026-10-06/design-R-861.md`) — the household's data, not host root |
+| `FELHOM_CONTROLLERSWAP` | the managed controller update | exact vmid; image ref pinned to `gitea.dooplex.hu/admin/felhom-controller:X.Y.Z` for the image check; the inspect template stays free text; **the write goes through `felhom-priv-apply controller-image <vmid>`** (the ref on stdin, re-checked as root against the same pattern — R-861 (a) A1, `09` §3 decision 165, agent after v0.150.0) | guest-scoped: a compromised agent can restart the guest's bootstrap and choose an OLDER version of OUR controller image (a downgrade); it can no longer hand the guest any other image. Until the A1 bundle reached a box, the agent's in-guest `tee` let it write any ref (sudo cannot see stdin — the 2026-10-06 night correction, `audits/night-burndown-2026-10-06/design-R-861.md`) |
 | `FELHOM_STALELOCK` / `FELHOM_SCRATCH_TEARDOWN` | stale-lock clear; failed restore-test scratch | exact vmid; the scratch band `99000[0-9]` was already exact | — |
 | `FELHOM_WG` | the off-site tunnel | conf via `felhom-priv-apply wg` (only the keys `renderConf` writes; no `PostUp`/`PreUp`/`DNS`/`Table`; `/32` only) | — |
 | `FELHOM_SELFUPDATE` | commit / rollback of the A/B flip | **`apply` removed**: the flip runs only inside `felhom-os-apply agent_update`, after the operator signature, host, window and nonce are checked as root and the staged bytes are hashed ONCE and copied to a root-owned dir (`/var/lib/felhom-os-apply/agent-update/`); the wrapper accepts only that dir | — |
-| `FELHOM_SSHD` | the out-of-band operator sshd | config via `felhom-priv-apply sshd-config` (the ONE template, only the Port varies, never 22); the felhom-op key via `sshd-key` (one plain key, no `command=`/`from=` options) | felhom-op's key itself is hub-delivered, not signed: a compromised agent can install its own key for **felhom-op** — whose sudo is scoped (`felhom-op.sudoers`), not root |
+| `FELHOM_SSHD` | the out-of-band operator sshd | config via `felhom-priv-apply sshd-config` (the ONE template, only the Port varies, never 22); the felhom-op key via `sshd-key` (one plain key, no `command=`/`from=` options) | felhom-op's key itself is hub-delivered, not signed: a compromised agent can install its own key for **felhom-op** — whose sudo is scoped (`felhom-op.sudoers`: fixed repair verbs and `pct start` / `stop` / `unlock` of ONE numeric vmid, anchored since R-861 (b) B2), not root — accepted (`09` §3 decision 165, B3) |
 | `FELHOM_OOB` | the OOB firewall sets | `add element` takes exactly `{ <ip>[/n] }` or `{ <port> }` — no chained command | — |
 | `FELHOM_PBSDR` / `FELHOM_BACKUPTARGET` | PBS DR entry; whole-system backup target | unchanged: the arguments stay coarse, and the root wrappers (`felhom-pbs-apply`, `felhom-backup-target-apply`) are the gate (fixed verbs, own validation) | coarse argv into a checking wrapper |
 | `FELHOM_ESCROW` | the recovery-code ceremony (runs the agent binary as root) | the binary is only ever an operator-signed one (`FELHOM_SELFUPDATE`); as root it pins the PVE secret dir and the WG state dir, refuses a storage id that is a path, and reads its two staged files by walking the path with `openat(O_NOFOLLOW)` (no symlink anywhere) | **by design the agent relays R**, so a compromised agent can still learn this box's PBS key through the ceremony — not root, but the backup key |