freezmo/lib/model-guard.ts
Martin Dvorak 8822baf4b7 Security: model budget + concurrency caps, SSRF guards, spoof-proof limits
Audit pass with the threats that actually apply to a self-hosted, account-less
app: getting the Ollama key throttled or banned, and someone grinding the app
down. Per-route windows already existed; these are the missing layers.

- lib/model-guard.ts: every route that spends a model call now takes a slot —
  60 calls per window across all clients (RATE_LIMIT_MODEL_TOTAL), 3 in flight
  per IP, 6 in total — and the slot is released when the call finishes, on
  errors and on client disconnects. Over the concurrency cap answers 429
  kind=busy, not a punishment. Slots are taken after every cheap rejection so
  a malformed request cannot hold one (found by the new suite: early 400s
  were leaking slots).
- Images must be base64 data URLs (dataUrlSchema in lib/schemas): a plain URL
  in an images field made Ollama fetch an arbitrary address on our behalf.
- Push endpoints must be a real push service (PUSH_ALLOWED_HOSTS, defaulting
  to FCM/Mozilla/Apple/WNS): the server POSTs to whatever is stored.
- The rate-limit identity is the LAST x-forwarded-for hop. Reading the first
  let a client spoof its own IP and dodge every per-IP limit.
- Disk guards: reports.jsonl stops at REPORTS_MAX_BYTES (8 MB), reminder
  devices cap at PUSH_MAX_SUBSCRIPTIONS (50).
- Security headers: frame-ancestors 'none' + X-Frame-Options DENY, nosniff, a
  referrer policy and a Permissions-Policy without camera/mic/geo/payment.

New tests/security-test.mjs (13 checks, registered in run-all) proves each
guard against a slow stub Ollama with deliberately tiny limits. README:
security notes + rate-limit tables updated. Version 0.1.3, SW -> v51.
2026-10-12 20:40:57 +00:00

60 lines
2 KiB
TypeScript

import type { ServerConfig } from "./config";
import { translate, type Locale } from "./i18n-dict";
import { acquireSlot, clientKey, rateLimit, rateLimitResponse, releaseSlot } from "./rate-limit";
/**
* One gate in front of every route that spends an Ollama call:
*
* - a **global budget** per window (all clients together) so no flood can
* burn through the account — the thing that gets a key throttled or banned;
* - a **per-IP concurrency cap** and a **global one**, so a burst of parallel
* requests can't pile up model calls (or sockets and memory).
*
* The slot is released once, when the response is finished — including a
* client that disconnects mid-stream, and including routes that throw.
*/
export type ModelGate = { release: () => void };
export function acquireModelGate(
request: Request,
config: ServerConfig,
locale: Locale,
): { gate: ModelGate } | { response: Response } {
const perIpKey = `model-ip:${clientKey(request)}`;
const totalKey = "model-total";
if (!acquireSlot(totalKey, config.rateLimits.concurrentTotal)) {
return { response: busyResponse(locale) };
}
if (!acquireSlot(perIpKey, config.rateLimits.concurrent)) {
releaseSlot(totalKey);
return { response: busyResponse(locale) };
}
const budget = rateLimit("model-budget", config.rateLimits.modelTotal, config.rateLimits.windowMs);
if (!budget.allowed) {
releaseSlot(perIpKey);
releaseSlot(totalKey);
return { response: rateLimitResponse(budget, locale) };
}
let released = false;
return {
gate: {
release: () => {
if (released) return;
released = true;
releaseSlot(perIpKey);
releaseSlot(totalKey);
},
},
};
}
/** 429 for "something is already running" — not a rate-limit punishment. */
function busyResponse(locale: Locale): Response {
return Response.json(
{ error: translate(locale, "server.busy"), kind: "busy", retryAfter: 5 },
{ status: 429, headers: { "Retry-After": "5", "Cache-Control": "no-store" } },
);
}