dashboard: format guard on post_purge_tombstone (path traversal hole — argus 🔴 on #593)

hive-c0re/src/dashboard.rs

@@ -1886,6 +1886,17 @@ async fn post_purge_tombstone(
     State(state): State<AppState>,
     AxumPath(name): AxumPath<String>,
 ) -> Response {
+    // Format guard FIRST so a name like `..` can't traverse into the
+    // parent of `/var/lib/hyperhive/agents/{name}` and have
+    // `remove_dir_all` wipe `/var/lib/hyperhive/` itself. Existing
+    // manager + live-container checks below don't catch `..` — only
+    // the whitelist does. (argus #593 🔴.) Existence check via
+    // `containers_snapshot()` is deliberately NOT used here:
+    // tombstoned agents are gone from the snapshot by design; that's
+    // the whole point of this endpoint.
+    if let Some(reason) = validate_agent_name(&name) {
+        return (StatusCode::BAD_REQUEST, format!("bad agent name: {reason}")).into_response();
+    }
     if name == lifecycle::MANAGER_NAME {
         return error_response("refusing to purge the manager's state");
     }