fix(lora): never serve a LoraManager folder that holds the home folder (#355)

The folder guard also rejects ancestors of the home folder (/home,
C:\Users), compared in the realpath + normcase form, so a LoraManager
setting cannot widen the image server's allow-list to every user's files.

py/lora_manager_layout.py

@@ -161,15 +161,17 @@ def _guard_folder(
 ) -> Optional[str]:
     """The canonical form of ``path`` when it may be read and served, else None.
 
-    Kept only when it is a folder, not a filesystem root and not the home
-    folder itself.
+    Kept only when it is a folder, not a filesystem root, and neither the
+    home folder nor one of its ancestors (``/home``, ``C:\\Users``: a
+    security review ruled that a folder holding the home folder must never
+    be read or served).
     """
     isdir = isdir or os.path.isdir
     try:
         canonical = _canonical(path, pathmod)
         if not isdir(canonical) or _is_filesystem_root(canonical, pathmod):
             return None
-        if canonical == _canonical(home, pathmod):
+        if _inside(home, (canonical,), pathmod):
             return None
     except (OSError, ValueError):
         return None

tests/test_lora_manager_layout.py

@@ -688,6 +688,59 @@ class FolderGuardTests(unittest.TestCase):
         )
         self.assertIsNone(layout_module._guard_folder(str(self.tmp), str(self.tmp)))
 
+    def test_ancestors_of_home_are_rejected(self):
+        # Security review (#355): a settings folder that contains the home
+        # folder would serve every user's files.
+        home = self.tmp / "home" / "me"
+        inside = home / "loras"
+        inside.mkdir(parents=True)
+        guard = layout_module._guard_folder
+        self.assertIsNone(guard(str(self.tmp / "home"), str(home)))
+        self.assertIsNone(guard(str(self.tmp), str(home)))
+        self.assertIsNone(guard(str(home), str(home)))
+        self.assertEqual(guard(str(inside), str(home)), os.path.normcase(str(inside)))
+        # A sibling sharing the name prefix is not an ancestor.
+        sibling = self.tmp / "home" / "me2"
+        sibling.mkdir()
+        self.assertEqual(guard(str(sibling), str(home)), os.path.normcase(str(sibling)))
+
+    def test_windows_ancestors_of_home_are_rejected(self):
+        self.assertIsNone(self.guard_nt("C:\\Users", home="C:\\Users\\me"))
+        self.assertIsNone(self.guard_nt("c:/users/", home="C:\\Users\\me"))
+        self.assertEqual(
+            self.guard_nt("C:\\Users\\me\\Loras", home="C:\\Users\\me"),
+            "c:\\users\\me\\loras",
+        )
+        self.assertEqual(
+            self.guard_nt("C:\\Users\\meta", home="C:\\Users\\me"),
+            "c:\\users\\meta",
+        )
+
+    def test_settings_folders_that_contain_home_are_not_served(self):
+        home = self.tmp / "home" / "me"
+        home.mkdir(parents=True)
+        settings = self.tmp / "settings"
+        settings.mkdir()
+        (settings / "settings.json").write_text(
+            json.dumps(
+                {
+                    "folder_paths": {"loras": [str(self.tmp / "home")]},
+                    "example_images_path": str(self.tmp),
+                }
+            )
+        )
+        with patch.object(layout_module.Path, "home", return_value=home):
+            layout = load_layout(
+                str(self.tmp),
+                default_roots=lambda: [],
+                environ={"LORA_MANAGER_SETTINGS_DIR": str(settings)},
+                user_config_dir=lambda: str(self.tmp / "unused"),
+            )
+        self.assertIsNone(layout.error)
+        self.assertEqual(layout.lora_roots, ())
+        self.assertIsNone(layout.example_images_root)
+        self.assertEqual(layout.media_roots, ())
+
     def test_missing_folders_add_nothing(self):
         self.assertIsNone(layout_module._guard_folder(str(self.tmp / "x"), "/home"))
         self.assertIsNone(