# Authentication

`AUTH_MODE` selects how users sign in. The container refuses to start without a working
configuration – there is no unauthenticated mode.

| Mode | Use when |
|---|---|
| `local` | one shared admin account is enough |
| `oidc` | you have an identity provider (Authentik, Keycloak, Authelia, Zitadel, …) |
| `local,oidc` | SSO with a local fallback account |
| `proxy` | your reverse proxy already authenticates (forward auth, basic auth, IP allow list) |

Every change (ban/unban) additionally needs the per-session CSRF token and a matching
`Origin` header, and every action is written to the audit log with the user name.

## Local user

```bash
docker compose run --rm -it fail2ban-webui hash-password
```

```ini
AUTH_MODE=local
AUTH_USER=admin
AUTH_PASSWORD_HASH='scrypt:32768:8:1$…'
```

- Passwords need at least 12 characters; the hash is scrypt (Werkzeug).
- After `LOGIN_MAX_ATTEMPTS` (5) failures a client IP is locked for `LOGIN_LOCK_MINUTES` (15).
- Failed logins are logged as `LOGIN_FAILED user=… ip=…` – see
  [operations.md](operations.md#protecting-the-login-with-fail2ban) to let fail2ban ban
  them at the proxy.
- Set `TRUSTED_PROXY_HOPS=1` behind a reverse proxy, otherwise all clients appear with the
  proxy's address and share one lockout counter.

## OpenID Connect

Requirements: `PUBLIC_URL` is set to the external `https://` URL, and the provider allows
the redirect URI **`<PUBLIC_URL>/auth/callback`**.

The UI uses the authorization code flow with PKCE (`S256`) and a confidential client.
User name: `OIDC_USERNAME_CLAIM` (default `preferred_username`); groups:
`OIDC_GROUPS_CLAIM` (default `groups`).

**Always restrict who may sign in** with `OIDC_ALLOWED_GROUPS` and/or
`OIDC_ALLOWED_USERS` – or with an access policy in the provider. Without either, every
account that the provider lets use this client can ban IPs (a warning is logged at start).

### Authentik

1. **Applications → Providers → Create → OAuth2/OpenID Provider**
   - Name: `fail2ban-webui`
   - Authorization flow: `default-provider-authorization-explicit-consent` (or implicit)
   - Client type: **Confidential** – note *Client ID* and *Client Secret*
   - Redirect URIs: `strict` · `https://fail2ban.example.org/auth/callback`
   - Signing key: any certificate (e.g. `authentik Self-signed Certificate`)
   - Advanced protocol settings → Scopes: `openid`, `email`, `profile`
     (the default *profile* mapping contains the `groups` claim)
2. **Applications → Applications → Create**
   - Name: `fail2ban-webui`, Slug: `fail2ban-webui`, Provider: the one from step 1
3. **Directory → Groups → Create** `fail2ban-admins` and add the users.
4. Optional, recommended: in the application under **Policy / Group / User Bindings**
   bind the group `fail2ban-admins`, so nobody else even reaches the consent screen.
5. `.env`:

   ```ini
   PUBLIC_URL=https://fail2ban.example.org
   AUTH_MODE=oidc
   OIDC_ISSUER=https://auth.example.org/application/o/fail2ban-webui/
   OIDC_CLIENT_ID=…
   OIDC_CLIENT_SECRET='…'
   OIDC_ALLOWED_GROUPS=fail2ban-admins
   OIDC_BUTTON_LABEL=Authentik
   ```

6. `docker compose up -d`, open `PUBLIC_URL`, click **Sign in with Authentik**.

The issuer URL is shown in Authentik on the provider page (*OpenID Configuration Issuer*).

### Other providers

| Provider | `OIDC_ISSUER` | Groups |
|---|---|---|
| Keycloak | `https://kc.example.org/realms/<realm>` | add a *Group Membership* mapper with claim name `groups`, "Full group path" off |
| Authelia | `https://auth.example.org` | `groups` scope; set `OIDC_SCOPES=openid email profile groups` |
| Zitadel | `https://<instance>.zitadel.cloud` | roles instead of groups – use `OIDC_ALLOWED_USERS` or a project role check in Zitadel |

### Sign out

"Sign out" ends the session in the web UI. The session at the provider stays active, so
the next "Sign in with …" usually logs in again without a password.

## Reverse-proxy mode

The proxy does the authentication; the UI only checks where requests come from and,
optionally, which user the proxy reports.

```ini
AUTH_MODE=proxy
TRUSTED_PROXY_HOPS=1
# only accept requests from the proxy (address as seen by the container)
AUTH_PROXY_ALLOWED_IPS=172.23.51.1/32
# optional: user name for the audit log, set by the proxy
AUTH_PROXY_HEADER=X-authentik-username
# optional: logout URL of the proxy/IdP
AUTH_PROXY_LOGOUT_URL=https://fail2ban.example.org/outpost.goauthentik.io/sign_out
```

- `AUTH_PROXY_ALLOWED_IPS` is checked against the **direct** peer of the container, not
  against `X-Forwarded-For`. If the proxy runs on the same Docker host and reaches the
  container via the published port, that is the network gateway (`172.23.51.1` in the
  example compose file); check with `docker compose logs` after a request.
- With `AUTH_PROXY_HEADER` set, requests without the header are rejected (401). Make sure
  the proxy **removes** that header from client requests – forward-auth integrations
  (Authentik, Authelia) do that.
- Without `AUTH_PROXY_HEADER` the audit log shows the user `proxy`.

Examples for Nginx Proxy Manager, Traefik and Caddy are in
[reverse-proxy.md](reverse-proxy.md).