fix(proxy): prevent remote 401 from triggering local session logout

- Add x-sencho-proxy sentinel header to all proxied responses so
  the frontend can distinguish remote auth failures from local session
  expiry, breaking the logout loop when a node's api_token expires
- Add authMiddleware to all 5 /api/notifications endpoints that were
  missing protection (default-deny policy enforcement)
- Expand CSP to include connectSrc ws:/wss: and workerSrc blob:
  for WebSocket and Monaco editor worker support

CHANGELOG.md

@@ -6,6 +6,12 @@ and this project adheres to [Semantic Versioning](https://semver.org/spec/v2.0.0
 
 ## [Unreleased]
 
+### Fixed
+- **Login loop caused by remote node auth failure:** When a configured remote node had an expired or invalid API token, every proxied request to that node returned 401. Both `apiFetch` and `fetchForNode` treated any 401 as a user session failure and dispatched `sencho-unauthorized`, immediately logging the user out and sending them back to the login page — even after a successful login. Fixed by adding a `proxyRes` handler that stamps all remote-proxied responses with `x-sencho-proxy: 1`; the frontend now only fires `sencho-unauthorized` when this header is absent (i.e., it's a genuine local session failure).
+- **Missing `authMiddleware` on notifications endpoints:** `GET /api/notifications`, `POST /api/notifications/read`, `DELETE /api/notifications/:id`, `DELETE /api/notifications`, and `POST /api/notifications/test` were all missing `authMiddleware`, violating the default-deny policy. Added to all five.
+- **CSP `workerSrc` missing (Monaco editor workers):** The Content Security Policy had no explicit `worker-src` directive, which in practice relied on `default-src 'self'`. Monaco editor creates Web Workers via `blob:` URLs for language services; these were silently failing. Added `worker-src 'self' blob:`.
+- **CSP `connectSrc` implicit (WebSocket):** Added explicit `connect-src 'self' ws: wss:` to clearly permit same-origin WebSocket connections in both HTTP and HTTPS contexts.
+
 ### Fixed
 - **Blank page on HTTP deployments (CSP `upgrade-insecure-requests`):** Helmet's default CSP included `upgrade-insecure-requests`, which causes browsers to silently upgrade all HTTP sub-resource fetches (JS, CSS, images) to HTTPS. On a plain-HTTP self-hosted deployment this produces a completely blank page with `ERR_SSL_PROTOCOL_ERROR`. The directive is now explicitly omitted from the CSP.
 - **HSTS permanently breaking HTTP access:** Helmet's default `Strict-Transport-Security` header was being sent over HTTP, instructing browsers to refuse non-HTTPS connections for 1 year. HSTS is now disabled and must only be re-enabled by users who terminate HTTPS at a reverse proxy in front of Sencho.

backend/src/index.ts

@@ -87,6 +87,12 @@ app.use(helmet({
       scriptSrc: ["'self'"],
       scriptSrcAttr: ["'none'"],
       styleSrc: ["'self'", 'https:', "'unsafe-inline'"],
+      // connect-src: explicit 'self' covers same-origin fetch/XHR/WebSocket.
+      // ws: and wss: are included for WebSocket connections in any scheme context.
+      connectSrc: ["'self'", 'ws:', 'wss:'],
+      // worker-src: Monaco editor creates Web Workers via blob: URLs for language
+      // services (syntax highlighting, intellisense). Without blob: they silently fail.
+      workerSrc: ["'self'", 'blob:'],
       // 'upgrade-insecure-requests' is intentionally absent — see comment above.
     },
   },
@@ -450,6 +456,15 @@ const remoteNodeProxy = createProxyMiddleware<Request, Response>({
       // http-proxy's req.pipe(proxyReq) forwards the body automatically.
       // No manual body rewriting needed here.
     },
+    proxyRes: (proxyRes) => {
+      // Mark every response forwarded from a remote node with a sentinel header.
+      // The frontend (apiFetch / fetchForNode) checks this before firing the
+      // global 'sencho-unauthorized' event: a 401 from a remote means the stored
+      // api_token for that node is invalid — not that the user's own session
+      // expired. Without this distinction, any node with a bad token causes an
+      // immediate logout loop.
+      proxyRes.headers['x-sencho-proxy'] = '1';
+    },
     error: (err, _req, proxyRes) => {
       console.error('[Proxy] Remote node error:', (err as Error).message);
       // proxyRes can be either a ServerResponse (HTTP) or a raw Socket (WS/TCP errors).
@@ -1559,7 +1574,7 @@ app.delete('/api/alerts/:id', async (req: Request, res: Response) => {
   }
 });
 
-app.get('/api/notifications', async (req: Request, res: Response) => {
+app.get('/api/notifications', authMiddleware, async (req: Request, res: Response) => {
   try {
     const history = DatabaseService.getInstance().getNotificationHistory();
     res.json(history);
@@ -1568,7 +1583,7 @@ app.get('/api/notifications', async (req: Request, res: Response) => {
   }
 });
 
-app.post('/api/notifications/read', async (req: Request, res: Response) => {
+app.post('/api/notifications/read', authMiddleware, async (req: Request, res: Response) => {
   try {
     DatabaseService.getInstance().markAllNotificationsRead();
     res.json({ success: true });
@@ -1577,7 +1592,7 @@ app.post('/api/notifications/read', async (req: Request, res: Response) => {
   }
 });
 
-app.delete('/api/notifications/:id', async (req: Request, res: Response) => {
+app.delete('/api/notifications/:id', authMiddleware, async (req: Request, res: Response) => {
   try {
     const id = parseInt(req.params.id as string, 10);
     DatabaseService.getInstance().deleteNotification(id);
@@ -1587,7 +1602,7 @@ app.delete('/api/notifications/:id', async (req: Request, res: Response) => {
   }
 });
 
-app.delete('/api/notifications', async (req: Request, res: Response) => {
+app.delete('/api/notifications', authMiddleware, async (req: Request, res: Response) => {
   try {
     DatabaseService.getInstance().deleteAllNotifications();
     res.json({ success: true });
@@ -1596,7 +1611,7 @@ app.delete('/api/notifications', async (req: Request, res: Response) => {
   }
 });
 
-app.post('/api/notifications/test', async (req: Request, res: Response) => {
+app.post('/api/notifications/test', authMiddleware, async (req: Request, res: Response) => {
   try {
     const { type, url } = req.body;
     await NotificationService.getInstance().testDispatch(type, url);

frontend/src/lib/api.ts

@@ -26,8 +26,13 @@ export async function apiFetch(
   const response = await fetch(url, { ...defaultOptions, ...fetchOptions });
 
   if (response.status === 401) {
-    // Signal auth failure to AuthContext without a hard page reload
-    window.dispatchEvent(new Event('sencho-unauthorized'));
+    // Only fire the global logout event for local auth failures.
+    // When the response carries x-sencho-proxy, the 401 came from a remote
+    // Sencho node (expired/invalid api_token) — not from the user's own session.
+    // Logging out in that case creates an unrecoverable loop.
+    if (!response.headers.get('x-sencho-proxy')) {
+      window.dispatchEvent(new Event('sencho-unauthorized'));
+    }
     throw new Error('Unauthorized');
   }
 
@@ -66,7 +71,10 @@ export async function fetchForNode(
   });
 
   if (response.status === 401) {
-    window.dispatchEvent(new Event('sencho-unauthorized'));
+    // Same logic as apiFetch: only log out for local auth failures.
+    if (!response.headers.get('x-sencho-proxy')) {
+      window.dispatchEvent(new Event('sencho-unauthorized'));
+    }
     throw new Error('Unauthorized');
   }