feat: provision Alpine LXC 136 running Atheos, wired to Gitea
Provisions a LAN-only browser code editor (Atheos) in an Alpine 3.23 LXC on the scotty PVE node, with armistace/blog cloned and ready to edit. Built via the AI-DLC workflow; the full process trail is in aidlc-docs/. Deliverables - scripts/provision.sh rebuild the guest from scratch (re-runnable) - scripts/update-atheos.sh move Atheos to latest upstream and RE-PIN - scripts/build-and-test.sh captures evidence for every acceptance criterion - files/atheos.conf nginx vhost (socket path byte-matches the FPM pool) - files/ssh-config ~atheos/.ssh/config deploy-key alias - RUNBOOK.md operational guide (START AT STEP 1) - docs/security-notes.md credential model + wider-web hardening TODOs - docs/resiliency-notes.md what a non-PoC deployment would need Design decisions - D1 no git identity is configured by the agent; the operator sets it. Git will refuse the first commit until then, which is deliberate (requirement FR-11). - D2 Atheos pinned to commit f90cd18 (build 611) with a verified tarball sha256, plus update-atheos.sh as the deliberate escape hatch. - D3 nginx :80, web root /var/www/atheos, php-fpm over a unix socket. - D6 git auth is a per-repository DEPLOY KEY scoped to armistace/blog, not a personal access token (a PAT's write:repository scope reaches every repo the account can write). Verified on the live guest (40 checks, 0 failures) - AC-2 Atheos served over HTTP 200 by nginx+php-fpm; socket paths byte-match - AC-3 20 posts + themes/cleanblog present; owned by the php-fpm user - AC-4 all five writable paths writable as the service user - AC-5 remote targets armistace/blog; deploy key authenticates over SSH - AC-6 survival proven with a real container restart, marker byte-identical - AC-8 no python/pelican/pip/make and no DB engine - scope boundary enforced - FR-11 git identity is empty; deploy key mode 600 owned by the service user Traps documented in the RUNBOOK (each cost real debugging time) - The Gitea SSH user is `gitea`, NOT `git` (app.ini SSH_USER=gitea). With `git`, sshd answers "Invalid user git" and rejects before reading authorized_keys, which is indistinguishable from a bad key. - The Gitea SSH endpoint is the LAN address (:22 is not forwarded publicly). - `uptime` and `free` report the PVE HOST inside an LXC without lxcfs, so a container that just restarted can claim days of uptime.
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# Security Notes — atheos-blog-lxc
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**Status**: security-baseline extension **opted out** (LAN-only PoC) per Andrew's standing preference.
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**Purpose**: preserve the hardening trail so that *if this ever moves to the wider web*, the work is
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already scoped, and nobody has to re-derive it. Every item names its code touch-point.
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**Reviewed**: 2026-09-29. Design decision **D6** (see `application-design.md`).
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---
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## 1. The credential model (the load-bearing decision)
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**Chosen: a per-repository Gitea _deploy key_, scoped to `armistace/blog`, write-enabled.**
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### Why not the alternatives
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| Option | Scope if stolen | Verdict |
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|---|---|---|
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| **Deploy key** (chosen) | `armistace/blog` **only** | ✅ per-repo scoping, explicit `read_only` flag |
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| `armistace` personal access token | **every repo armistace can write** (scopes are route-groups like `write:repository`, matched against user access — *not* per-repo) | ❌ account-wide blast radius |
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| `armistace` personal SSH key | whole account, incl. web/API | ❌ |
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| Dedicated "Atheos" Gitea user | whatever it owns/grants — **no reduction** for `blog` | ❌ adds a credential + muddies attribution |
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**Verified, not assumed** (2026-09-29, live instance 1.27.3):
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- API schema: `AccessToken.scopes` = `["read:repository","write:repository",…]`; `DeployKey` carries
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`read_only: bool` and is bound to one repository. Deploy-key endpoints
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`/repos/{owner}/{repo}/keys` exist and are **per-repo**.
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- The instance's own token inventory shows the risk concretely: `armistace` holds 8 access tokens,
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one with scope **`all`**.
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> **Threat model this addresses.** Atheos is itself the untrusted component: it is a file editor
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> with shell-exec reach (`codegit` invokes `git`; Atheos uses `exec`/`system`) and it is reachable by
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> anyone on the LAN. The goal is not to make compromise impossible — it is to make the **blast radius
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> one repository** when it happens.
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### Implementation (code touch-points)
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| Item | Where | Detail |
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|---|---|---|
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| Keypair generated **on the guest**, never leaves it | `scripts/provision.sh`, U4 | `ssh-keygen -t ed25519 -f ~/<fpmuser>/.ssh/id_ed25519_blog -N ''` |
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| Key owned **only** by the php-fpm run user, mode `600` | U4 | not readable by nginx or other users |
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| `IdentitiesOnly yes` + a named host alias | `~/<fpmuser>/.ssh/config` | `Host gitea-blog` so a stray push cannot target another repo |
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| Remote uses the alias | U4 | `gitea-blog:armistace/blog.git` |
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| **Public** half handed to the operator | via Matrix | operator adds it: repo → Settings → Deploy Keys → **Allow write access** |
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⚠️ **Honest limitation.** For push to work, the deploy key must be readable by the web-app user, so a
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full Atheos compromise *can* use it to write `blog`. Unavoidable for any push-capable editor. The
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deploy key makes that the **floor** (one repo, one protected branch), not the **ceiling** (8 repos).
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---
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## 2. If this is ever exposed beyond the LAN
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| # | Item | Touch-point |
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|---|---|---|
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| S-1 | **Terminate TLS** at NPM; never serve Atheos plaintext to the internet | NPM proxy host |
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| S-2 | **Authenticate in front of Atheos**, not just inside it — an NPM Access List / SSO so the app is not the only gate | NPM |
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| S-3 | **fail2ban** on the guest for failed Atheos logins and nginx 401/403s | guest + `nginx.conf` log format |
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| S-4 | **Rate-limit** the login endpoint in nginx (`limit_req_zone`) | `nginx.conf` |
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| S-5 | **Force HTTPS** redirect; set `Strict-Transport-Security` | `nginx.conf` |
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| S-6 | **Session hardening**: `session.cookie_secure=1`, `session.cookie_httponly=1`, `session.cookie_samesite=Lax` | `php.ini` |
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| S-7 | **Disable PHP dangerous functions** Atheos does not need: `exec, shell_exec, system, passthru, proc_open, popen` — *except* git needs `proc_open`/`exec`, so this needs testing before applying | `php.ini` — ⚠️ test, do not blind-apply |
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| S-8 | **`open_basedir`** to `/var/www/atheos` + `/tmp` to contain a file-read bug | `php.ini` |
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| S-9 | **nginx hardening**: `X-Content-Type-Options`, `X-Frame-Options`, `Referrer-Policy`, deny dotfiles, deny `*.md`/`*.py`/`.git` serving | `nginx.conf` |
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| S-10 | **Protect the deploy key + config** from being served: verify `/.ssh`, `/config.php`, `/data` are not web-reachable | `nginx.conf` — **verify with curl, not by reading config** |
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| S-11 | **Gitea-side**: consider an IP allowlist / rate limit on the git endpoint if the box is public | Gitea/NPM |
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| S-12 | **Alerting** on: nginx 5xx rate, new git remote, deploy-key use, file changes under `/var/www/atheos` | not built — would need the observability stack |
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| S-13 | **Keep Atheos patched** — it is PHP, no releases; re-pin deliberately (see `scripts/update-atheos.sh`) | update script |
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| S-14 | **`allow_url_fopen=On`** is currently enabled (needed for the plugin marketplace). Turn it **off** for internet exposure unless the marketplace is genuinely required | `php.ini` |
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## 3. Standing hygiene (applies now, LAN or not)
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- Branch protection on `armistace/blog` **master** — so a compromised editor cannot force-push master,
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only propose. *(Repo-side; operator-owned.)*
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- The deploy key is **write-enabled** by explicit choice. If push ever becomes unnecessary, flip it to
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read-only in the repo settings — zero code change.
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- No secrets in git: the private key is generated on the guest and never committed (`.gitignore`).
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- Agent must never create `armistace` credentials (FR-11).
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## 4. Accepted risks (conscious, recorded)
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| Risk | Why accepted | Revisit trigger |
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|---|---|---|
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| Atheos has shell-exec capability | it is a git-integrated editor; unavoidable | if exposed publicly → apply S-2, S-7, S-8 |
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| Deploy key readable by the web user | required for push | if push no longer needed → set read-only |
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| LAN has no TLS | LAN-only scope (FR-10) | on any external exposure → S-1 |
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| `allow_url_fopen=On` | plugin marketplace | if the marketplace is unused → set Off |
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| No monitoring/alerting | out of scope; observability stack is separate | if exposed publicly → S-12 |
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