Validate state.json is a normal file

tests/test_state_safety.py

@@ -0,0 +1,49 @@
+from __future__ import annotations
+
+import json
+import os
+from pathlib import Path
+
+import pytest
+
+from enroll.state import StateSafetyError, load_state, open_state_file
+
+
+def test_load_state_reads_regular_state_json(tmp_path: Path):
+    (tmp_path / "state.json").write_text(
+        json.dumps({"host": {"hostname": "test-host"}}), encoding="utf-8"
+    )
+
+    assert load_state(tmp_path)["host"]["hostname"] == "test-host"
+
+
+def test_load_state_rejects_state_json_symlink(tmp_path: Path):
+    target = tmp_path / "target.json"
+    target.write_text("{}", encoding="utf-8")
+    (tmp_path / "state.json").symlink_to(target)
+
+    with pytest.raises(StateSafetyError, match="state.json is a symlink"):
+        load_state(tmp_path)
+
+
+def test_load_state_rejects_non_regular_state_json(tmp_path: Path):
+    (tmp_path / "state.json").mkdir()
+
+    with pytest.raises(StateSafetyError, match="state.json is not a regular file"):
+        load_state(tmp_path)
+
+
+def test_load_state_rejects_hardlinked_state_json(tmp_path: Path):
+    state_file = tmp_path / "state.json"
+    state_file.write_text("{}", encoding="utf-8")
+    os.link(state_file, tmp_path / "state-copy.json")
+
+    with pytest.raises(StateSafetyError, match="state.json is hardlinked"):
+        load_state(tmp_path)
+
+
+def test_open_state_file_rejects_oversized_state_json(tmp_path: Path):
+    (tmp_path / "state.json").write_text("{}", encoding="utf-8")
+
+    with pytest.raises(StateSafetyError, match="state.json is too large"):
+        open_state_file(tmp_path, max_bytes=1)