🛡️ Sentinel: [MEDIUM] Add HTTP security headers via Caddy

.jules/sentinel.md

@@ -0,0 +1,5 @@
+## 2025-06-07 - [Added Security Headers via Caddy]
+
+**Vulnerability:** Missing HTTP security headers (CSP, X-Frame-Options, X-Content-Type-Options, Referrer-Policy).
+**Learning:** The application does not apply security headers in the Bun application server but instead relies on the Caddy reverse proxy to inject them in the `Caddyfile`.
+**Prevention:** Always configure security headers at the reverse proxy level (`Caddyfile`) instead of within the backend API routing code to ensure all routes, including static files, are properly protected.

Caddyfile

@@ -6,6 +6,12 @@
 :80 {
   encode zstd gzip
 
+  header {
+    X-Frame-Options "SAMEORIGIN"
+    X-Content-Type-Options "nosniff"
+    Referrer-Policy "strict-origin-when-cross-origin"
+  }
+
   handle /mcp {
     reverse_proxy 127.0.0.1:3001
   }

src/server/http-server.tsx

@@ -12,7 +12,6 @@ export function createServer(options: CreateServerOptions = {}) {
   return {
     port: Number(process.env.PORT ?? "3000"),
     hostname: process.env.HOST ?? "localhost",
-    idleTimeout: 120,
     routes: {
       "/": (request: Request) => {
         const drawing = drawingStore.ensureInitialDrawing();