xamxam/docs/security.md

# Security

Current security posture for XAMXAM.

> This supersedes the earlier `security.md` (2026-02-08 audit). The original
> 16-item audit is closed; the items below reflect the current state.

---

## Authentication — admin

- **PHP session auth:** `app/src/AdminAuth.php`. Password-only (no username).
  Credentials previously in a gitignored PHP file; the current build stores the
  bcrypt hash in `site_settings.admin_password_hash` (manageable from
  `/admin/account`).
- `AdminAuth::requireLogin()` guards every admin action/route.
- Session cookies hardened: `HttpOnly`, `SameSite=Strict`, `Secure`,
  `Path=/admin`; regenerated on login.
- **Session timeouts** (server-side, enforced by `AdminAuth::enforceSessionTimeout()`
  on every gated request):
  - **Idle timeout** — 30 min without activity → session destroyed, redirected
    to login.
  - **Absolute timeout** — 12 h since login → forced re-login, regardless of
    activity.
  - Session ID rotated periodically (every 30 min) to limit fixation/replay.
  - The session *cookie* `lifetime` is 7 days, but that is only an upper bound
    on browser retention — the actual session is bounded by the two timeouts above.
- **PHP-FPM session GC tuning** — see below. The app enforces its own timeouts,
  so `session.gc_maxlifetime` must be ≥ the 12 h absolute timeout or PHP would
  reap active sessions early.
- nginx `auth_basic` layer has been removed; the PHP session layer is the only
  gate. (LDAP-based login is a proposed future enhancement — see
  [`ldap.md`](ldap.md). It is **not** implemented.)

### PHP-FPM session GC configuration

The admin session's lifetime is enforced *by the app* (the timeouts above), so
PHP's own session garbage collector must not reap active sessions before the
12 h absolute timeout. The following is provisioned by
`scripts/deploy-server.sh` (run via `just deploy-nginx`):

**File:** `/etc/php/8.4/fpm/conf.d/zz-xamxam-session.ini`

```ini
; XAMXAM session tuning.
; AdminAuth enforces its own idle/absolute timeouts (30 min / 12 h), so
; gc_maxlifetime must be >= the absolute timeout or PHP would reap active
; sessions from under the app.
session.gc_maxlifetime = 43200
session.gc_probability = 1
session.gc_divisor     = 100
```

- `gc_maxlifetime = 43200` (12 h) — matches `ABSOLUTE_TIMEOUT_SECONDS`;
  **must stay ≥ the app's absolute timeout**.
- `gc_probability = 1` / `gc_divisor = 100` — re-enables the GC (default was
  `gc_probability = 0`, i.e. disabled, so stale session files were never reaped).
- Applied on FPM reload (`systemctl reload php8.4-fpm`), done by the deploy script.

> ⚠️ Keep these three knobs in sync with the constants in
> `app/src/AdminAuth.php` (`IDLE_TIMEOUT_SECONDS`, `ABSOLUTE_TIMEOUT_SECONDS`,
> `COOKIE_LIFETIME_SECONDS`). If you raise the app's absolute timeout beyond
> 12 h, raise `gc_maxlifetime` to match.

## Transport & headers

Enforced in `nginx/xamxam.conf` (see `nginx/docs/SECURITY_HEADERS.md`):

- **HSTS** (`Strict-Transport-Security`, 730 days, preload)
- **CSP** — `default-src 'self'; … frame-ancestors 'none'` on public pages;
  `frame-ancestors 'self'` where the app embeds allowed content; admin CSP
  includes `script-src 'unsafe-inline'` for the OverType editor. `object-src 'none'`.
- `X-Frame-Options: DENY` (clickjacking)
- `X-Content-Type-Options: nosniff`
- `Referrer-Policy: strict-origin-when-cross-origin`
- `Permissions-Policy` (geo/mic/camera disabled)
- `Cross-Origin-Opener-Policy` / `Cross-Origin-Resource-Policy: same-origin`
- `X-Robots-Tag: noindex, nofollow` on `/admin/`

`X-XSS-Protection` is intentionally **omitted** (deprecated; see
`nginx/docs/SECURITY_HEADERS.md` for rationale).

## Rate limiting

Defined in the nginx config `limit_req_zone` and enforced by
`app/src/RateLimit.php`:

- General requests: `30 r/m`
- Search endpoint: `30 r/m`
- Admin panel: `300 r/m` (burst 30)

The PHP limiter uses `REMOTE_ADDR` only (not `X-Forwarded-For`) to avoid IP
spoofing.

## Files & storage

- Uploads live **outside the webroot** under `app/storage/` (`tfe/`, `theses/`),
  served on demand via `MediaController`/`FileAccessController` through
  controlled endpoints (`/media`), not direct static access.
- nginx blocks `/storage`, `/src`, `/templates`, DB/sql/env/md files, and hidden
  files. The DocumentRoot is `app/public/` only.
- Restricted-file downloads are gated by a request/approval/token flow
  (`file_access_*` tables).
- Logs write to `/var/log/xamxam/` in production (and `app/storage/logs/`
  only in dev/cli-server) — outside the webroot, not publicly served.

## Injection & output

- **SQL:** all queries use PDO prepared statements.
- **LIKE wildcards:** `Database::escapeLikeString()` escapes `%` and `_`
  (public search and related queries).
- **XSS:** `htmlspecialchars()` on all user-controlled output; integer/ID
  inputs cast.
- **CSRF:** per-session tokens (`bin2hex(random_bytes(32))`), compared with
  `hash_equals()`.
- **File uploads:** MIME validated (`finfo`); FilePond prevalidation +
  server-side checks in `FilepondHandler`.
- **Markdown/HTML:** user content (pages, help blocks) rendered via
  `league/commonmark`; HTML in admin-editable content is expected.

## Defence in depth / misc

- External links use `rel="noopener noreferrer"`.
- Decryption/`Crypto` failures are logged without leaking secrets; SMTP
  password is stored encrypted in `smtp_settings` and rotated via
  `just reencrypt-password`.
- Admin operations are recorded in `admin_audit_log` (resource, action,
  status, IP, User-Agent).

## Areas to keep monitored

- Tightening the public CSP (`frame-ancestors 'none'` vs `'self'` on embed
  routes) is an active topic — see `TODO.md`.
- Sensitive file downloads and their expiry/token handling are worth periodic
  review as usage grows.

See also: `nginx/docs/SECURITY_HEADERS.md`, `nginx/docs/PHP_AUTH_LAYER.md`,
`nginx/docs/PRODUCTION_DEPLOYMENT.md`.