# Authentik — the homelab's SSO / OIDC provider

Authentik is the single sign-on (SSO) and OpenID Connect (OIDC) provider for the
homelab. It fronts the Caddy vhosts that do not carry their own
application-level authentication. Apps that have their own login (Grafana,
Gitea, OpenWebUI, Jellyfin, the *arr stack, Pi-hole) are not wrapped in
forward_auth — they handle their own session.

- **Version:** `2026.8.0` (pinned in `dankclaw/compose.yaml`)
- **Host:** dankclaw (`192.168.0.143`)
- **Name:** `auth.franksdank.cloud`
- **Stack:** 3 compose services — `authentik-postgres`, `authentik-server`,
  `authentik-worker` (see [Pi-hole](Pi-hole.md) for the LAN-DNS pattern)

## Why Authentik

The comparison that chose it (against Authelia, Keycloak, Zitadel, Ory) is in
`.docaudit/research/auth.md`. In short: full OIDC with single-logout, a web GUI
for all configuration, a native Caddy `forward_auth` outpost, and a footprint
that fits on a 3-user homelab (~1–1.5 GB idle). Redis was removed in 2025.10,
so the stack is 3 services, not 4.

## Architecture

```mermaid
graph LR
    subgraph Browser
        U[User]
    end
    subgraph Caddy [Caddy - auth gate]
        FA[forward_auth]
    end
    subgraph AK [Authentik]
        SRV[server :9000]
        WKR[worker]
        PG[(postgres)]
        OUT[outpost /auth/caddy]
    end
    subgraph App [Target app]
        A1[SearXNG / Hermes / Prometheus<br/>RomM / Copyparty / homepage]
    end

    U -->|1. GET /| FA
    FA -->|2. GET /outpost.../auth/caddy| OUT
    OUT -->|3. no session: 302 login| U
    U -->|4. login at auth.franksdank.cloud| SRV
    SRV --> PG
    WKR --> PG
    SRV -->|5. 2xx: session valid| FA
    FA -->|6. proxy with headers| A1
```

1. The browser hits a protected vhost (e.g. `search.franksdank.cloud`).
2. Caddy `forward_auth` clones the request to the Authentik outpost
   (`/outpost.goauthentik.io/auth/caddy`).
3. With no valid session, the outpost returns a `302` to the Authentik login
   page (`auth.franksdank.cloud`).
4. The user logs in at Authentik (email + password, TOTP/WebAuthn MFA, or an
   upstream provider).
5. On the next request the outpost returns `2xx`; Caddy copies the
   `X-Authentik-*` headers and proxies to the app.

## The three compose services

| Service | Role | Image |
|---|---|---|
| `authentik-postgres` | PostgreSQL 16 (users, flows, sessions, events) | `docker.io/library/postgres:16-alpine` |
| `authentik-server` | Core + admin API + the embedded Caddy outpost (port 9000) | `ghcr.io/goauthentik/server:2026.8.0` |
| `authentik-worker` | Background tasks (event processing, provider sync, flows) | `ghcr.io/goauthentik/server:2026.8.0` |

- **Postgres** is the only stateful store. Sessions, caching, and WebSockets
  moved to PostgreSQL in 2025.10 (Redis removed).
- **Server** and **worker** run the same image; the `command` selects the role
  (`server` / `worker`).
- The worker runs as `0:0` (rootless: container root maps to the host user that
  owns the data dir).
- Data persists under `/home/dank/authentik/` (bind mounts, repo policy — no
  named volumes).

## Caddy integration

The Caddyfile wraps the no-auth vhosts in a `route` block. The pattern (one
example; the others are identical):

```caddyfile
search.franksdank.cloud {
	route {
		# 1. The outpost path is proxied to Authentik (login UI + session).
		reverse_proxy /outpost.goauthentik.io/* authentik-server:9000
		# 2. forward_auth checks the session before serving the app.
		forward_auth authentik-server:9000 {
			uri /outpost.goauthentik.io/auth/caddy
			copy_headers X-Authentik-Username X-Authentik-Groups X-Authentik-Email X-Authentik-Name
			trusted_proxies private_ranges
		}
		# 3. The app.
		reverse_proxy 192.168.0.143:8081
	}
}
```

Vhosts protected by forward_auth: the homepage (`franksdank.cloud`,
`www.franksdank.cloud`), SearXNG, Hermes, Prometheus, RomM, Copyparty. The
`auth.franksdank.cloud` vhost proxies to the server directly (no forward_auth —
it *is* the login).

## Configuration (secrets)

Two secrets live in the host `.env` (git-ignored; placeholders in
`.env.example`):

- `AUTHENTIK_PG_PASS` — the PostgreSQL password. Generate: `openssl rand -base64 32`.
- `AUTHENTIK_SECRET_KEY` — the server's signing key. Generate: `openssl rand -base64 48`.

## First-time setup

1. `./scripts/deploy.sh dankclaw` — pulls, starts the 3 services (postgres
   health-gated), reloads Caddy.
2. Open `https://auth.franksdank.cloud` — the initial setup wizard runs. It
   creates the superuser (email + password) and generates the DB schema.
3. In the admin interface: **Directory → Applications** → add a **Proxy**
   application (or an **OAuth2/OpenID Connect** provider) for each vhost you
   protect. The Caddy outpost reads the application's policy.
4. For apps with native OIDC (Grafana, Gitea, OpenWebUI): add an **OAuth2/OpenID
   Connect** provider, create the app with the correct redirect URI, and paste
   the `client_id` / `client_secret` into the app's SSO settings.

## Operations

- **Health:** `https://auth.franksdank.cloud/-/health/` (the server healthcheck
  probes this).
- **Logs:** `podman logs authentik-server` / `podman logs authentik-worker`.
- **Backups:** `pg_dump` the `authentik-postgres` database (the single source of
  truth). The `/home/dank/authentik/` dir holds media + static files.
- **Upgrades:** bump the image tag in `dankclaw/compose.yaml`, run
  `./scripts/deploy.sh dankclaw`. Authentik migrates the schema on startup.

## Failure modes

| Symptom | Cause | Fix |
|---|---|---|
| Every vhost 502s at the outpost | `authentik-server` down | `podman logs authentik-server`; check postgres health |
| Login loops (302 → login → 302) | `trusted_proxies` / `X-Forwarded-*` mismatch | Confirm Caddy sets `X-Forwarded-For`; the outpost trusts `private_ranges` |
| "Invalid signature" on the outpost | `AUTHENTIK_SECRET_KEY` differs between server and worker | Both services read the same `.env` var; re-deploy |
| Postgres "password authentication failed" | `AUTHENTIK_PG_PASS` changed after first init | Reset via `pg_ctl` or re-init the data dir |

## Cross-references

- [Caddy](Caddy.md) — the reverse proxy that carries the forward_auth directives
- [Pi-hole](Pi-hole.md) — the LAN DNS that resolves `auth.franksdank.cloud`
- [Network Architecture](../Architecture/Network%20Architecture.md) — the flat naming scheme
- Research: `.docaudit/research/auth.md` — the full provider comparison