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fix: add resource limit in zen-proxy.mjs (CWE-770) #3

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fix: add resource limit in zen-proxy.mjs (CWE-770) #3

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24 changes: 24 additions & 0 deletions zen-proxy.mjs
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Original file line number Diff line number Diff line change
Expand Up @@ -108,6 +108,26 @@ const requestStats = { total: 0, errors: 0, recent: [], perMinute: new Map(), wi
const VALID_MODEL_ID = /^[A-Za-z0-9._:@+/%-]+$/
const MAX_BODY = 1024 * 1024

// Basic per-IP request throttling (CWE-770): without this, a single client can
// flood the router/upstream with unlimited concurrent requests.
const RATE_LIMIT_WINDOW_MS = Number(ENV.RATE_LIMIT_WINDOW_MS ?? 60_000)
const RATE_LIMIT_MAX = Number(ENV.RATE_LIMIT_MAX ?? 120)
const rateLimitBuckets = new Map()
function isRateLimited(req) {
const ip = clientIp(req) || "unknown"
const now = Date.now()
const bucket = rateLimitBuckets.get(ip)
if (!bucket || now - bucket.start >= RATE_LIMIT_WINDOW_MS) {
rateLimitBuckets.set(ip, { start: now, count: 1 })
if (rateLimitBuckets.size > 5000) {
for (const [k, v] of rateLimitBuckets) if (now - v.start >= RATE_LIMIT_WINDOW_MS) rateLimitBuckets.delete(k)
}
return false
}
bucket.count++
return bucket.count > RATE_LIMIT_MAX
}

// opencode's free tier requires every request to carry an `x-opencode-session`
// header (upstream returns 400 `MissingSessionID` otherwise). Generic agents
// never send one, so we mint stable per-client session IDs and inject them.
Expand Down Expand Up @@ -797,6 +817,10 @@ async function router(req, res) {
const url = new URL(req.url, `http://${req.headers.host ?? "localhost"}`)
const p = url.pathname

if (isRateLimited(req)) {
return json(res, 429, { error: { type: "rate_limit_error", message: "too many requests" } })
}

if (req.method === "GET" && (p === "/" || p === "/index.html" || p === "/ui")) {
res.writeHead(200, { "content-type": "text/html; charset=utf-8" })
return res.end(uiHtml || "<h1>UI not found</h1>")
Expand Down