# Anubis — bot challenge proxy

Anubis is the bot-challenge proxy that fronts the guarded public vhosts on
Dankclaw. Browsers get a proof-of-work challenge; AI scraper user-agents are
denied outright. It sits in a two-tier chain: client → Caddy TLS listener →
Anubis (`:8923`, internal-only) → Caddy internal listener (`:8016`) → app.
Host headers survive both hops, so per-vhost routing (and Authentik
`forward_auth` for the wrapped apps) resumes unchanged behind it. See
[[Caddy]] and [[Authentik]].

```mermaid
graph LR
    C[Client] --> T[Caddy TLS listener]
    T --> A[Anubis verify :8923]
    A -->|accepted| I[Caddy internal listener :8016]
    A -->|challenge or deny| C
    I --> P[per-vhost routing and forward_auth]
```

## Facts (live inventory)

| Item | Value |
|------|-------|
| Runtime | Quadlet unit `anubis.service` (`dankclaw/anubis/quadlet/anubis.container`) — boot-persistent, self-healing |
| Image | `ghcr.io/techarohq/anubis:v1.13.0`, run under a `localhost/` alias tag (see gotcha 1) |
| Ports | `:8923` internal (no published port); metrics on `:9090` reachable only inside `dankclaw_default` |
| Config surface | flags via flagenv — `TARGET=http://caddy:8016` sets `--target`, `POLICY_FNAME=/policy/policy.json` sets `--policy-fname` |
| Policy | `dankclaw/anubis/policy.json` mounted read-only into the container; parsed at process start only (no reload signal exists — every policy change needs a unit restart) |
| Store | memory (no signing keys needed); a restart invalidates issued challenge JWTs — users simply re-challenge once |

Policy content: DENY for AI-scaper user-agent regexes (GPTBot, Claude-*,
Perplexity*, CCBot, Bytespider, Amazonbot, meta-externalagent, and friends),
CHALLENGE for everything else (`path_regex: "."` catch-all), DNSBL off.
Policy schema at this tag is JSON-only — no `(data)/` imports and no CEL;
first match wins. Upgrading the pin = stop the unit, pull + re-tag the
`localhost/` alias, restart; re-verify the policy schema against the new tag first.

## Exempt by construction

These never route through Anubis (no policy bypass rule needed): plex
(plain-HTTP legacy), auth.franksdank.cloud (the IdP login itself must stay
ungated), and gitea (git smart-HTTP clients cannot solve JS challenges —
`/info/refs` and `git-*-pack` paths pass unchallenged).

## Gotchas (all verified live 2026-08-28)

1. **Image ref casing.** Podman's reference parser rejects mixed-case
   repository refs before any network I/O (`repository name must be
   lowercase`). All refs use the lowercase `ghcr.io/techarohq/anubis` form —
   ghcr resolves case-insensitively at pull time.
2. **Quadlet + registry-prefixed refs.** On this host's podman 5.7 quadlet
   path, a container created from a registry-prefixed image ref fails with
   `image not known` even when the image is present in storage; the identical
   argv works from a shell or a transient unit. The unit therefore runs the
   image under a `localhost/techarohq/anubis:v1.13.0` alias tag — deploy
   pulls the canonical ref, then `podman tag`s the alias (idempotent).
3. **Health probe exec form.** The image is a distroless ko-build (no shell;
   entrypoint `/ko-app/anubis`). This quadlet generator joins `HealthCmd`
   into one `\x20`-escaped argv element and podman then runs it shell-form —
   exec of a missing shell exits 1 and the container sits unhealthy. A JSON
   exec-form array (`HealthCmd=["/ko-app/anubis","--healthcheck"]`) passes
   through the generator verbatim and executes the binary directly.
4. **Rollback nuance.** `systemctl --user stop anubis.service` makes every
   guarded vhost return 502 (the chain is reverse-proxy-THROUGH Anubis, not
   forward_auth — Caddy's public listeners proxy to `:8923`). A true rollback
   is a Caddyfile revert + redeploy of the caddy service.
5. **Deploy handler pull guard.** `deploy_anubis` guards the pull with
   `podman image exists`; a cold anonymous ghcr token request can 403 on the
   first fetch — retry once, the auth cache makes the second attempt local.

## Verify live

```
ssh dankclaw 'systemctl --user is-active anubis.service'
curl -s -o /dev/null -w "%{http_code}\n" -A "GPTBot" https://franksdank.cloud/   # denied page
curl -s -o /dev/null -w "%{http_code}\n" -A "Mozilla/5.0" https://franksdank.cloud/  # challenge 200
```