# Security posture

This site is meant to demonstrate the discipline it advertises. Security is treated
as acceptance criteria, not polish.

## Attack surface

- **Static output** - no server runtime, no database, no user input, no forms.
- Served by `nginx-unprivileged` (uid 101, read-only root filesystem, all Linux
  capabilities dropped, no service-account token) on Kubernetes.
- Exposed **outbound-only via a Cloudflare Tunnel** - no open inbound ports, a single
  public hostname, no catch-all.

## Headers

Split by where they belong:

**Origin (nginx, ships in the image - `nginx/security-headers.conf`)**

| Header | Value |
|---|---|
| Content-Security-Policy | `default-src 'self'; script-src 'self'; style-src 'self' 'unsafe-inline'; img-src 'self' data:; font-src 'self'; connect-src 'self'; worker-src 'self'; manifest-src 'self'; object-src 'none'; base-uri 'self'; form-action 'self'; frame-ancestors 'none'; upgrade-insecure-requests` |
| X-Content-Type-Options | `nosniff` |
| X-Frame-Options | `DENY` |
| Referrer-Policy | `strict-origin-when-cross-origin` |
| Permissions-Policy | camera/mic/geo/payment/usb... all denied |
| Cross-Origin-Opener-Policy | `same-origin` |
| Cross-Origin-Resource-Policy | `same-origin` |

**Edge (Cloudflare dashboard)** - HSTS, HTTP->HTTPS redirect, SSL Full, Bot Fight,
rate-limiting. HSTS ships **without** `includeSubDomains`/`preload` initially because
`*.bztmon.com` resolves to the WAN and the subdomain form would brick non-public hosts.

## CSP notes

- **`script-src 'self'` with zero inline scripts.** All JS (pre-paint theme, toggle,
  scroll reveal) lives in one external `/site.js`. No `unsafe-inline`, no `unsafe-eval`,
  no hashes to maintain.
- **`style-src` allows `'unsafe-inline'`** - the one conscious exception. Shiki's
  dual-theme syntax highlighting emits per-token CSS custom-properties as inline `style`
  attributes; hashing them is impractical (they vary per page). The security-critical
  directive (`script-src`) stays strict. Everything else is self-hosted: fonts are system
  stacks (zero font requests), no third-party scripts, so SRI is moot.
- CSP is emitted as a real HTTP **header** (not `<meta>`) so `frame-ancestors` is honoured
  and header scanners can see it.

## Build-time gate

`npm run scan` (`scripts/check-build.sh`) fails the build on:
- secret-like strings in `dist/`
- any inline `<script>` (would break the strict CSP)
- third-party `<script>`/`<link>` origins

Runs in CI before the image is built.

## Targets (verified post-deploy)

- securityheaders.com -> A+
- Mozilla Observatory -> A/A+ (small deduction expected for `style-src 'unsafe-inline'`)
- Lighthouse >= 95 across Performance / Accessibility / Best Practices / SEO
- CSP: zero console violations in a real browser (incl. code blocks + diagrams)

## Reporting

Found something? Email the address on the site.
