fail2ban-ui/docs/security.md

# Security guidance

This project can perform security-sensitive operations (bans, configuration changes). Deploy it as you would deploy every other administrative interface.

## Recommended deployment posture

- Do not expose the UI directly to the Internet.
- Prefer one of:
  - VPN-only access
  - Reverse proxy with strict allowlists
  - OIDC enabled (in addition to network controls)

If you must publish it, put it behind TLS and an authentication layer, and restrict source IPs.

See [`docs/reverse-proxy.md`](https://github.com/swissmakers/fail2ban-ui/blob/main/docs/reverse-proxy.md) for hardened proxy examples and WebSocket forwarding requirements.

## Input validation

All user-supplied IP addresses are validated using Go's `net.ParseIP` and `net.ParseCIDR` before they are passed to any integration, command, or database query. This applies to:

- Ban/Unban callbacks (`/api/ban`, `/api/unban`)
- Manual ban/unban actions from the dashboard
- Advanced action test endpoint (`/api/advanced-actions/test`)
- All integration connectors (MikroTik, pfSense, OPNsense)

Integration-specific identifiers (address list names, alias names) are validated against a strict alphanumeric pattern (`[a-zA-Z0-9._-]`) to prevent injection in both SSH commands and API payloads.

## WebSocket security

The WebSocket endpoint (`/api/ws`) is protected by:

- **Origin validation**: The upgrade handshake verifies that the `Origin` header matches the request's `Host` header (same-origin policy). Cross-origin WebSocket connections are rejected. This prevents cross-site WebSocket hijacking attacks.
- **Authentication**: When OIDC is enabled, the WebSocket endpoint requires a valid session.

## Callback endpoint protection

The callback endpoints (`/api/ban`, `/api/unban`) are protected by `CALLBACK_SECRET` (`X-Callback-Secret` header). If no secret is specified, Fail2Ban UI generates one on first start. Additional hardening:

- Use a long, random secret and rotate it on suspected leakage
- Restrict network access so only known Fail2Ban hosts can reach callback endpoints

Rotate the secret if you suspect leakage.

## SSH connector hardening

For SSH-managed hosts:

- Use a dedicated service account (not a human user).
- Require key-based auth.
- Restrict sudo to the minimum set of commands required to operate Fail2Ban (at minimum `fail2ban-client *` and `systemctl restart fail2ban`).
- Use filesystem ACLs for `/etc/fail2ban` rather than broad permissions to allow full modification capabilities for the specific user.

## Integration connector hardening

When using external firewall integrations (MikroTik, pfSense, OPNsense):

- Use a dedicated service account on the firewall device with the minimum permissions needed (address-list management only on MikroTik; alias management only on pfSense/OPNsense).
- For pfSense/OPNsense: use a dedicated API token with limited scope.
- Restrict network access so the Fail2ban-UI host is the only source allowed to reach the firewall management interface.

## Least privilege and file access

Local connector deployments typically require access to:
- `/var/run/fail2ban/fail2ban.sock`
- `/etc/fail2ban/`
- selected log paths (read-only, mounted to same place inside the container, where they are on the host.)

Avoid running with more privileges than necessary. If you run in a container, use the repository deployment guide and SELinux policies.

## SELinux

If SELinux is enabled, use the policies provided in:
- `deployment/container/SELinux/`

Do not disable SELinux as a shortcut. Fix always labeling and policy issues instead. -> Everytime you read "to disable SELinux" you can close that guide :)

## Alert provider security

Fail2Ban UI supports three alert providers: Email (SMTP), Webhook, and Elasticsearch. Each has specific security considerations.

### Email (SMTP)

- Use TLS (`Use TLS` enabled) for all SMTP connections.
- Avoid disabling TLS verification (`Skip TLS Verification`) in production. If you must, ensure the network path to the SMTP server is trusted.
- Use application-specific passwords or OAuth tokens where supported (e.g. Gmail, Office365) instead of primary account passwords.

### Webhook

- Use HTTPS endpoints whenever possible.
- If the webhook endpoint requires authentication, use custom headers (e.g. `Authorization: Bearer <token>`) rather than embedding credentials in the URL.
- Avoid disabling TLS verification for production endpoints. The `Skip TLS Verification` option exists for development/self-signed environments only.

### Elasticsearch

- Use API key authentication over basic auth when possible. API keys can be scoped to specific indices and rotated independently.
- Restrict the API key to write-only access on the `fail2ban-events-*` index pattern. Avoid cluster-wide or admin-level keys.
- Consider using Elasticsearch's built-in role-based access control to limit what the Fail2Ban UI service account can do.


## Audit and operational practices

- Back up `/config` (DB + settings) regularly.
- Treat the database as sensitive operational data.
- Keep the host and container runtime patched.
- Review Fail2Ban actions deployed to managed hosts as part of change control.