fix: harden filesystem trust boundaries

tools/scripts/tests/test_generate_index_security.py

@@ -0,0 +1,53 @@
+import importlib.util
+import json
+import pathlib
+import sys
+import tempfile
+import unittest
+
+
+REPO_ROOT = pathlib.Path(__file__).resolve().parents[3]
+sys.path.insert(0, str(REPO_ROOT / "tools" / "scripts"))
+
+
+def load_module(module_path: str, module_name: str):
+    spec = importlib.util.spec_from_file_location(module_name, REPO_ROOT / module_path)
+    module = importlib.util.module_from_spec(spec)
+    spec.loader.exec_module(module)
+    return module
+
+
+generate_index = load_module("tools/scripts/generate_index.py", "generate_index")
+
+
+class GenerateIndexSecurityTests(unittest.TestCase):
+    def test_parse_frontmatter_rejects_non_mapping_yaml(self):
+        metadata = generate_index.parse_frontmatter("---\njust-a-string\n---\nbody\n")
+        self.assertEqual(metadata, {})
+
+    def test_generate_index_skips_symlinked_skill_markdown(self):
+        with tempfile.TemporaryDirectory() as temp_dir:
+            skills_dir = pathlib.Path(temp_dir) / "skills"
+            safe_skill_dir = skills_dir / "safe-skill"
+            linked_skill_dir = skills_dir / "linked-skill"
+            outside_dir = pathlib.Path(temp_dir) / "outside"
+            output_file = pathlib.Path(temp_dir) / "skills_index.json"
+
+            safe_skill_dir.mkdir(parents=True)
+            linked_skill_dir.mkdir(parents=True)
+            outside_dir.mkdir()
+
+            (safe_skill_dir / "SKILL.md").write_text("---\nname: Safe Skill\n---\nbody\n", encoding="utf-8")
+            target = outside_dir / "secret.txt"
+            target.write_text("outside data", encoding="utf-8")
+            (linked_skill_dir / "SKILL.md").symlink_to(target)
+
+            skills = generate_index.generate_index(str(skills_dir), str(output_file))
+
+            self.assertEqual([skill["id"] for skill in skills], ["safe-skill"])
+            written = json.loads(output_file.read_text(encoding="utf-8"))
+            self.assertEqual([skill["id"] for skill in written], ["safe-skill"])
+
+
+if __name__ == "__main__":
+    unittest.main()