[client] Authorize daemon IPC callers by their local identity (#6967)

client/ui/frontend/src/hooks/usePrivilege.ts

@@ -0,0 +1,32 @@
+import { useEffect, useState } from "react";
+import { Settings as SettingsSvc } from "@bindings/services";
+import { Privilege } from "@bindings/services/models.js";
+
+// usePrivilege reports whether this UI process may perform the changes the daemon
+// restricts to root/administrator. It is answered in-process from our own token
+// with the daemon's own rule, so there is no round-trip and it works while the
+// daemon is down.
+//
+// null means "not known yet", which includes the read having failed. Callers must
+// treat that as "do not restrict": the daemon enforces this regardless, so the
+// only thing a wrong guess here costs is a control that looks unavailable when it
+// is not, or a save that fails with the daemon's own guidance.
+export const usePrivilege = (): Privilege | null => {
+    const [privilege, setPrivilege] = useState<Privilege | null>(null);
+
+    useEffect(() => {
+        let cancelled = false;
+        SettingsSvc.Privilege()
+            .then((p) => {
+                if (!cancelled) setPrivilege(p);
+            })
+            .catch((e: unknown) => {
+                console.warn("[usePrivilege] read failed, not restricting controls", e);
+            });
+        return () => {
+            cancelled = true;
+        };
+    }, []);
+
+    return privilege;
+};