🔒 Fix arbitrary file write / path traversal via session_id

.gitignore

@@ -0,0 +1 @@
+__pycache__/

hooks/security_guard.py

@@ -37,7 +37,8 @@ def debug_log(msg):
 
 def get_state_file(session_id):
     """Return path to session-specific state file for dedup."""
-    return os.path.expanduser(f"~/.claude/.seal_guard_state_{session_id}.json")
+    safe_session_id = re.sub(r"[^a-zA-Z0-9_-]", "_", str(session_id))
+    return os.path.expanduser(f"~/.claude/.seal_guard_state_{safe_session_id}.json")
 
 
 def load_shown(session_id):

hooks/test_security_guard.py

@@ -0,0 +1,24 @@
+import pytest
+import os
+
+# Mocking os.path.expanduser to avoid touching real ~
+original_expanduser = os.path.expanduser
+
+def mock_expanduser(path):
+    return path.replace("~", "/tmp/mock_home")
+
+def test_get_state_file(monkeypatch):
+    monkeypatch.setattr(os.path, "expanduser", mock_expanduser)
+
+    # We need to import get_state_file
+    import sys
+    sys.path.append(os.path.abspath(os.path.dirname(__file__)))
+    from security_guard import get_state_file
+
+    path1 = get_state_file("normal_id_123")
+    assert "/tmp/mock_home/.claude/.seal_guard_state_normal_id_123.json" == path1
+
+    # With path traversal attack
+    path2 = get_state_file("../../../etc/passwd")
+    # After sanitization it should be:
+    assert "/tmp/mock_home/.claude/.seal_guard_state__________etc_passwd.json" == path2