screentinker/server/test/ota-hardening.test.js
ScreenTinker f037dd476a fix(#146) C: OTA hardening under SNAT — no per-request fs, global download caps
The fleet SNATs to one IP, so nothing on the OTA path may key on IP.

- /api/update/check: EARLY-RETURN before any filesystem call when the breaker won't
  offer (rate-backoff / up-to-date / phantom / client-newer). A looping client that
  gets rate-backoff now does ZERO fs — the flood can't become a statSync flood.
- lib/apk-cache.js: resolve APK path/size/mtime once at boot + refresh on an interval;
  the check/download endpoints read cached metadata (get() does no fs, proven by test).
- lib/ota-download-guard.js + /download/apk: GLOBAL concurrency + rate caps + critical-
  band shed (503 Retry-After), NEVER per-IP. Replaces the per-IP-per-10min log throttle
  (which hid the flood under SNAT) with a per-window served/shed aggregate so a download
  flood is VISIBLE. Bounded single rolling-state object; in-flight released on finish/close.
- Breaker unchanged; no IP limiting or device_id requirement added (legacy field clients
  send no device_id on OTA checks — must keep working).

Tests: apk-cache get() = 0 statSync over 1000 reads; download guard sheds past global
concurrency + per-window rate + critical band; admit() has no IP parameter. Suite 259/259.

Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>
2026-06-30 21:05:32 -05:00

71 lines
3.1 KiB
JavaScript

'use strict';
// #146 hardening (Item C) — OTA under SNAT. Cached APK resolution (no per-request fs)
// + GLOBAL download admission (concurrency + rate + critical-band shed, never per-IP).
const os = require('node:os');
const path = require('node:path');
const fs = require('node:fs');
const crypto = require('node:crypto');
process.env.DATA_DIR = path.join(os.tmpdir(), 'st-otahard-' + crypto.randomBytes(4).toString('hex'));
process.env.OTA_DOWNLOAD_MAX_CONCURRENT = '3';
process.env.OTA_DOWNLOAD_MAX_PER_WINDOW = '5';
process.env.OTA_DOWNLOAD_WINDOW_MS = '100000';
const { test } = require('node:test');
const assert = require('node:assert/strict');
const guard = require('../lib/ota-download-guard');
const apkCache = require('../lib/apk-cache');
test('apk-cache: get() never touches the filesystem (resolution cached at boot/refresh)', () => {
// seed a fake APK under DATA_DIR and refresh once
const apk = path.join(process.env.DATA_DIR, 'ScreenTinker.apk');
fs.mkdirSync(process.env.DATA_DIR, { recursive: true });
fs.writeFileSync(apk, 'FAKEAPKBYTES');
const c = apkCache.refresh();
assert.equal(c.exists, true);
assert.equal(c.size, 12);
// count fs.statSync calls across many get()s -> must be ZERO (a poll/download flood
// can't become a statSync flood).
const realStat = fs.statSync; let calls = 0;
fs.statSync = (...a) => { calls++; return realStat(...a); };
try { for (let i = 0; i < 1000; i++) apkCache.get(); } finally { fs.statSync = realStat; }
assert.equal(calls, 0, 'get() does no fs; 1000 reads = 0 statSync');
});
test('download guard: global concurrency cap -> 503 (not per-IP)', () => {
const s = guard.newState();
assert.equal(guard.admit(s, 'normal').allow, true);
assert.equal(guard.admit(s, 'normal').allow, true);
assert.equal(guard.admit(s, 'normal').allow, true); // 3 in-flight = cap
const over = guard.admit(s, 'normal');
assert.equal(over.allow, false);
assert.equal(over.status, 503);
assert.ok(over.retryAfter > 0);
guard.release(s); // free one slot
assert.equal(guard.admit(s, 'normal').allow, true, 'a freed slot admits again');
});
test('download guard: global per-window rate cap -> 503', () => {
const s = guard.newState();
for (let i = 0; i < 5; i++) { assert.equal(guard.admit(s, 'normal').allow, true); guard.release(s); } // 5 served this window
const over = guard.admit(s, 'normal');
assert.equal(over.allow, false, '6th in the window is shed');
assert.equal(over.status, 503);
});
test('download guard: critical band sheds regardless of caps', () => {
const s = guard.newState();
const v = guard.admit(s, 'critical');
assert.equal(v.allow, false);
assert.equal(v.retryAfter, 30, 'critical band asks for a longer backoff');
});
test('download guard admission takes NO ip argument (global by construction)', () => {
// admit(state, band, now) — there is no IP parameter, so it cannot key on IP.
assert.equal(guard.admit.length <= 3, true);
const s = guard.newState();
assert.equal(guard.admit(s, 'normal').allow, true); // works with zero IP context
});