[Add] Proper User managment

iota-util/tests/private_export.rs

@@ -0,0 +1,29 @@
+use iota_util::atomic_file::create_private;
+
+#[test]
+fn private_export_refuses_to_replace_existing_file() {
+    let directory = tempfile::tempdir().unwrap();
+    let path = directory.path().join("alice.tu");
+    create_private(&path, b"first").unwrap();
+
+    assert_eq!(
+        create_private(&path, b"second").unwrap_err().kind(),
+        std::io::ErrorKind::AlreadyExists
+    );
+    assert_eq!(std::fs::read(path).unwrap(), b"first");
+}
+
+#[cfg(unix)]
+#[test]
+fn private_export_uses_owner_only_permissions() {
+    use std::os::unix::fs::PermissionsExt;
+
+    let directory = tempfile::tempdir().unwrap();
+    let path = directory.path().join("alice.tu");
+    create_private(&path, b"secret").unwrap();
+
+    assert_eq!(
+        std::fs::metadata(path).unwrap().permissions().mode() & 0o777,
+        0o600
+    );
+}