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fix(cors): allow loopback origins + deny cleanly instead of 500 #1

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fix(cors): allow loopback origins + deny cleanly instead of 500 #1

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26 changes: 25 additions & 1 deletion src/index.ts
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Original file line number Diff line number Diff line change
Expand Up @@ -33,6 +33,25 @@ function sendShareViewer(res: express.Response) {
res.send(shareViewerHtml);
}

/**
* iClaw is local-first: the desktop app and the `npx` build serve their UI from a
* loopback host on an ephemeral port (e.g. http://127.0.0.1:54321), which can't be
* put in a static allow-list. Treat any loopback HTTP origin as trusted — the
* Origin header is browser-set (can't be forged cross-site), and the share API only
* ever stores opaque ciphertext anyway.
*/
function isLoopbackOrigin(origin: string): boolean {
try {
const { protocol, hostname } = new URL(origin);
return (
protocol === 'http:' &&
(hostname === '127.0.0.1' || hostname === 'localhost' || hostname === '[::1]')
);
} catch {
return false;
}
}

function buildApp(): express.Express {
const app = express();

Expand Down Expand Up @@ -62,7 +81,12 @@ function buildApp(): express.Express {
// Same-origin / non-browser requests have no Origin header.
if (!origin) return cb(null, true);
if (allow.includes(origin)) return cb(null, true);
cb(new Error(`Origin ${origin} is not allowed by CORS`));
// Local-first iClaw clients run on a loopback host with an ephemeral port.
if (isLoopbackOrigin(origin)) return cb(null, true);
// Deny WITHOUT throwing: cb(Error) makes cors call next(err) → a 500 on the
// preflight, which the browser surfaces as a useless "Failed to fetch".
// cb(null, false) is a clean CORS denial (no allow header, no 500).
cb(null, false);
},
methods: ['GET', 'POST', 'OPTIONS'],
allowedHeaders: ['Content-Type'],
Expand Down