Harden validation, improve runtime security and refactor core services

server/src/middleware.rs

@@ -9,3 +9,25 @@ pub async fn log_request(req: Request, next: Next) -> Response {
     tracing::info!("{} {} -> {}", method, uri, response.status());
     response
 }
+
+/// Injects defensive HTTP response headers on every response.
+///
+/// These headers mitigate several classes of attacks:
+/// - `X-Content-Type-Options: nosniff` — prevents MIME-type sniffing.
+/// - `X-Frame-Options: DENY` — blocks clickjacking via framing.
+/// - `Referrer-Policy: no-referrer` — suppresses referrer leakage.
+/// - `X-XSS-Protection: 0` — disables legacy XSS auditors (can introduce bugs).
+/// - `Permissions-Policy` — restricts powerful browser features.
+pub async fn security_headers(req: Request, next: Next) -> Response {
+    let mut response = next.run(req).await;
+    let headers = response.headers_mut();
+    headers.insert("x-content-type-options", "nosniff".parse().unwrap());
+    headers.insert("x-frame-options", "DENY".parse().unwrap());
+    headers.insert("referrer-policy", "no-referrer".parse().unwrap());
+    headers.insert("x-xss-protection", "0".parse().unwrap());
+    headers.insert(
+        "permissions-policy",
+        "camera=(), microphone=(), geolocation=()".parse().unwrap(),
+    );
+    response
+}