English | [日本語](security-hardening.ja.md)

# Security Hardening Guide

MAESTRO runs LLM-driven tasks that execute code, fetch the web, drive a browser,
and optionally run SSH commands. **Treat it as a privileged service.** This
guide turns the baseline in [SECURITY.md](../SECURITY.md) into an actionable,
ordered checklist for moving from "works on my laptop" to "safe for others to
reach."

For how to report a vulnerability, see [SECURITY.md](../SECURITY.md). For where
secrets live and their file permissions, see its *Secrets and Data* section.

## Threat model in one paragraph

Anyone who can reach the UI/API can create tasks, and a task can run tools
(Bash, web, browser, files, and — if enabled — SSH/MCP). Without authentication
that means anyone who can reach the port can run code on the host. The default
deployment is therefore **localhost-only and unauthenticated**; everything below
is about safely widening that.

## 1. Network exposure

- The app binds to `127.0.0.1` by default (bare metal) and Docker Compose
  publishes only `127.0.0.1:9876`. Keep it that way until auth and TLS are in
  place.
- When you do expose it, change the bind/port deliberately (`server.port`, the
  Compose port mapping) and front it with TLS — either MAESTRO's native HTTPS
  (`server.tls`) or a reverse proxy.

## 2. Authentication

Authentication is **off by default**. Before exposing the service beyond
localhost, turn it on:

- **OAuth** (Google / Gitea) or **local accounts** (email + password). Configure
  under `auth` in `config.yaml` or via Settings → Authentication.
- Set `auth.primary_provider` (`google` | `gitea` | `local`) when more than one
  provider is enabled to avoid an unintended login path.
- Restrict who becomes admin via `auth.admin_emails`.
- Set a stable `auth.session_secret` (or rely on the persisted
  `data/secrets/session-secret.key`); share it across nodes in a multi-node
  deployment so sessions survive failover.

## 3. Authorization and visibility

Tasks, schedules, and jobs carry an owner and a visibility scope: `private`
(owner + admin), `org` (members of the same organization), or `public` (any
logged-in user). Default new resources to `private` and grant `org`/`public`
only deliberately. Admins can see everything — keep the admin set small.

## 4. The Bash sandbox

The `Bash` tool runs inside a sandbox controlled by `safety.bash_sandbox`:

- `auto` (default) — use bubblewrap when available, otherwise a hardened
  allowlist.
- `always` — **required for multi-user / untrusted deployments**; fails closed
  if bubblewrap is unavailable rather than silently downgrading.
- `off` — no isolation; only for a trusted single operator.

bubblewrap needs unprivileged user namespaces. See
[operations/bash-sandbox-provisioning.md](operations/bash-sandbox-provisioning.md)
and, for containers, [docker.md](docker.md).

## 5. Transport security (TLS)

- Enable `server.tls` for native HTTPS, or terminate TLS at a reverse proxy.
- Set `auth.secure_cookie: true` whenever TLS terminates upstream (behind a
  proxy) so the session cookie carries the `Secure` flag. Native TLS sets it
  automatically.
- The default self-signed certificate makes browsers warn; install a real
  certificate for anything others use.

## 6. The metrics endpoint

`/metrics` exposes operational data. In production, restrict it:

- set a `bearer_token` (worker and/or gateway metrics config), and/or
- limit `allowed_hosts` to the scraper's source IPs.

Do not leave `/metrics` open on an internet-facing deployment.

## 7. Tools and integrations

Each enabled capability widens the blast radius. Before granting access to
untrusted users, review which tools and integrations are on:

- **SSH** — runs commands on remote hosts; credentials are envelope-encrypted
  with the master key. Enable only for trusted operators.
- **MCP** — external tool servers; credentials require `MCP_ENCRYPTION_KEY`.
- **Browser** — drives a real Chromium; treat fetched/automated content as
  untrusted input.

## 8. Secrets

See the *Secrets and Data* section of [SECURITY.md](../SECURITY.md). In short:
generated secrets live under `data/secrets/` at mode `0600`, are gitignored and
dockerignored, and core dumps are excluded because they can contain decrypted
keys. Rotate after any suspected exposure and review the audit log.

## 9. Updates and monitoring

- Track releases and apply security fixes promptly (fixes land on the latest
  release and `main`).
- Review the audit log after permission or configuration changes.

## Production checklist

Copy-paste before exposing MAESTRO to anyone but yourself:

- [ ] Authentication enabled (`auth.*`), `primary_provider` set, `admin_emails` minimal
- [ ] Stable `auth.session_secret` (shared across nodes if clustered)
- [ ] `safety.bash_sandbox: always`
- [ ] TLS terminated (native `server.tls` or a proxy) + `secure_cookie` matched
- [ ] Bind/port restricted to the intended interface
- [ ] `/metrics` protected (`bearer_token` and/or `allowed_hosts`)
- [ ] New resources default to `private`; `org`/`public` granted deliberately
- [ ] SSH/MCP/browser reviewed; enabled only as needed
- [ ] Secrets out of version control and backups; rotation plan in place
- [ ] A process to apply security updates