Reject submodule paths through outside symlinks

Resolve the worktree and checkout paths before applying containment so an in-repository symlink cannot redirect update or another filesystem consumer outside the repository.

Add a regression covering update through a symlinked path component.

Validation: .venv/bin/python -m pytest test/test_submodule.py -q; pre-commit run --files git/objects/submodule/base.py test/test_submodule.py; mypy git/objects/submodule/base.py; git diff --check.

Author: codex

git/objects/submodule/base.py

@@ -416,8 +416,11 @@ def _to_relative_path(cls, parent_repo: "Repo", path: PathLike) -> PathLike:
 
     @property
     def abspath(self) -> PathLike:
-        self._to_relative_path(self.repo, self.path)
-        return super().abspath
+        path = super().abspath
+        root = self.repo.working_tree_dir
+        assert root is not None
+        _to_relative_path(osp.realpath(root), osp.realpath(path))
+        return path
 
     @classmethod
     def _write_git_file_and_module_config(cls, working_tree_dir: PathLike, module_abspath: PathLike) -> None:

test/test_submodule.py

@@ -1384,6 +1384,22 @@ def test_update_rejects_checkout_path_outside_parent(self, rwdir):
             with pytest.raises(ValueError, match="is not in repository"):
                 submodule.update(init=True)
 
+    @with_rw_directory
+    def test_update_rejects_checkout_path_through_outside_symlink(self, rwdir):
+        parent = git.Repo.init(osp.join(rwdir, "parent"))
+        os.symlink(osp.join(rwdir, "outside"), osp.join(parent.working_tree_dir, "link"))
+        submodule = Submodule(
+            parent,
+            Submodule.NULL_BIN_SHA,
+            name="module",
+            path=osp.join("link", "module"),
+            url="unused",
+        )
+
+        with mock.patch.object(Submodule, "_clone_repo", side_effect=AssertionError("clone attempted")):
+            with pytest.raises(ValueError, match="is not in repository"):
+                submodule.update(init=True)
+
     @skipUnless(sys.platform == "win32", "Specifically for Windows.")
     @with_rw_directory
     def test_to_relative_path_windows_path_kinds(self, rwdir):