🐛 fix(probe): extract zipapp script privately

docs/changelog/206.security.rst

@@ -0,0 +1,2 @@
+When imported from an archive, python-discovery now extracts its interpreter probe into a private temporary directory.
+This prevents the probe from importing modules supplied in the shared temp directory.

src/python_discovery/_cached_py_info.py

@@ -195,13 +195,11 @@ def _resolve_py_info_script() -> Generator[Path]:
         if data is None:
             msg = f"cannot locate {_PY_INFO_SCRIPT.name} for subprocess interrogation"
             raise FileNotFoundError(msg)
-        fd, tmp = tempfile.mkstemp(suffix=".py")
-        try:
-            os.write(fd, data)
-            os.close(fd)
-            yield Path(tmp)
-        finally:
-            Path(tmp).unlink()
+        # Python prepends the probe script's directory to sys.path, so keep that directory private.
+        with tempfile.TemporaryDirectory() as private_dir:
+            script: Final[Path] = Path(private_dir) / _PY_INFO_SCRIPT.name
+            script.write_bytes(data)
+            yield script
 
 
 def _extract_between_cookies(out: str, start_cookie: str, end_cookie: str) -> tuple[str, str, int, int]:

tests/test_cached_py_info.py

@@ -4,6 +4,7 @@
 import logging
 import os
 import sys
+import tempfile
 from pathlib import Path
 from subprocess import TimeoutExpired, list2cmdline
 from typing import TYPE_CHECKING, Final
@@ -59,7 +60,9 @@ def test_resolve_py_info_script_fallback_to_pkgutil(mocker: MockerFixture) -> No
         assert script.exists()
         content = script.read_text(encoding="utf-8")
         assert content == "# mock script"
-    assert not script.exists()
+        assert script.parent != Path(tempfile.gettempdir())
+        assert list(script.parent.iterdir()) == [script]
+    assert not script.parent.exists()
 
 
 def test_resolve_py_info_script_pkgutil_returns_none(mocker: MockerFixture) -> None: