Frank
e006ad1f0f
The policy must ALLOW Anubis's own endpoints before the challenge-all rule or the challenge challenges itself: browsers POST-solve via make-challenge then GET-navigate pass-challenge, and a challenged answer renders as the browser's own fetch-failure error page. Non-JS clients never reach the verify step, which is why every curl probe looked green while every human hit a wall. Also records that v1.13.0's valid action verbs are ALLOW/CHALLENGE/DENY (ACCEPT crash-looped the unit on first deploy).
98 lines
5.6 KiB
Markdown
98 lines
5.6 KiB
Markdown
# Anubis — bot challenge proxy
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Anubis is the bot-challenge proxy that fronts the guarded public vhosts on
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Dankclaw. Browsers get a proof-of-work challenge; AI scraper user-agents are
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denied outright. It sits in a two-tier chain: client → Caddy TLS listener →
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Anubis (`:8923`, internal-only) → Caddy internal listener (`:8016`) → app.
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Host headers survive both hops, so per-vhost routing (and Authentik
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`forward_auth` for the wrapped apps) resumes unchanged behind it. See
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[[Caddy]] and [[Authentik]].
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```mermaid
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graph LR
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C[Client] --> T[Caddy TLS listener]
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T --> A[Anubis verify :8923]
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A -->|accepted| I[Caddy internal listener :8016]
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A -->|challenge or deny| C
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I --> P[per-vhost routing and forward_auth]
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```
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## Facts (live inventory)
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| Item | Value |
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|------|-------|
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| Runtime | Quadlet unit `anubis.service` (`dankclaw/anubis/quadlet/anubis.container`) — boot-persistent, self-healing |
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| Image | `ghcr.io/techarohq/anubis:v1.13.0`, run under a `localhost/` alias tag (see gotcha 1) |
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| Ports | `:8923` internal (no published port); metrics on `:9090` reachable only inside `dankclaw_default` |
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| Config surface | flags via flagenv — `TARGET=http://caddy:8016` sets `--target`, `POLICY_FNAME=/policy/policy.json` sets `--policy-fname` |
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| 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) |
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| Store | memory (no signing keys needed); a restart invalidates issued challenge JWTs — users simply re-challenge once |
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Policy content: an `ALLOW` rule for Anubis's own endpoints (the
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`/.within.website/x/cmd/anubis/*` API and static namespace — the challenge
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JS calls `make-challenge`/`pass-challenge` under that prefix, and challenging
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those endpoints makes the challenge challenge itself), then DENY for
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AI-scraper user-agent regexes (GPTBot, Claude-*, Perplexity*, CCBot,
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Bytespider, Amazonbot, meta-externalagent, and friends), then CHALLENGE for
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everything else (`path_regex: "."` catch-all). DNSBL off. Valid action verbs
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at this tag are `ALLOW`, `CHALLENGE`, `DENY` — `ACCEPT` is not one of them
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(first deploy of that rule crash-looped the unit on exactly that typo;
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verified against the image binary's string table). The policy schema at this
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tag is JSON-only — no `(data)/` imports and no CEL; first match wins.
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Upgrading the pin = stop the unit, pull + re-tag the `localhost/` alias,
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restart; re-verify the policy schema against the new tag first.
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## Exempt by construction
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These never route through Anubis (no policy bypass rule needed): plex
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(plain-HTTP legacy), auth.franksdank.cloud (the IdP login itself must stay
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ungated), and gitea (git smart-HTTP clients cannot solve JS challenges —
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`/info/refs` and `git-*-pack` paths pass unchallenged).
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## Gotchas (all verified live 2026-08-28)
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1. **Image ref casing.** Podman's reference parser rejects mixed-case
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repository refs before any network I/O (`repository name must be
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lowercase`). All refs use the lowercase `ghcr.io/techarohq/anubis` form —
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ghcr resolves case-insensitively at pull time.
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2. **Quadlet + registry-prefixed refs.** On this host's podman 5.7 quadlet
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path, a container created from a registry-prefixed image ref fails with
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`image not known` even when the image is present in storage; the identical
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argv works from a shell or a transient unit. The unit therefore runs the
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image under a `localhost/techarohq/anubis:v1.13.0` alias tag — deploy
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pulls the canonical ref, then `podman tag`s the alias (idempotent).
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3. **Health probe exec form.** The image is a distroless ko-build (no shell;
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entrypoint `/ko-app/anubis`). This quadlet generator joins `HealthCmd`
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into one `\x20`-escaped argv element and podman then runs it shell-form —
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exec of a missing shell exits 1 and the container sits unhealthy. A JSON
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exec-form array (`HealthCmd=["/ko-app/anubis","--healthcheck"]`) passes
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through the generator verbatim and executes the binary directly.
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4. **Rollback nuance.** `systemctl --user stop anubis.service` makes every
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guarded vhost return 502 (the chain is reverse-proxy-THROUGH Anubis, not
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forward_auth — Caddy's public listeners proxy to `:8923`). A true rollback
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is a Caddyfile revert + redeploy of the caddy service.
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5. **Deploy handler pull guard.** `deploy_anubis` guards the pull with
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`podman image exists`; a cold anonymous ghcr token request can 403 on the
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first fetch — retry once, the auth cache makes the second attempt local.
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6. **JS-capable clients are the canary.** Non-JS clients (curl, bots,
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scrapers) never solve challenges — they just receive the challenge page,
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so every curl probe looks green while the verification step is broken.
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The first JS-capable client to traverse a freshly deployed chain is the
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first real test of it: browsers POST-solve via `make-challenge` and
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GET-navigate `pass-challenge?response=<sha256(challenge+nonce)>&nonce=N
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&elapsedTime=T&redir=<path>`; if any own-endpoint path is challenged
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instead of allowed, the browser's fetch throws and it renders its own
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error page (iOS/macOS browsers phrase it as "the request failed and the
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interceptors did not return an alternative response") instead of the
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login flow. Verify with a JS-capable client end-to-end — mint via
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`make-challenge`, solve, submit with browser-exact query params — before
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declaring a challenge chain healthy.
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## Verify live
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```
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ssh dankclaw 'systemctl --user is-active anubis.service'
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curl -s -o /dev/null -w "%{http_code}\n" -A "GPTBot" https://franksdank.cloud/ # denied page
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curl -s -o /dev/null -w "%{http_code}\n" -A "Mozilla/5.0" https://franksdank.cloud/ # challenge 200
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```
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