fix: rewrite preserver_owner method complitely

Previous implementation was somewhat working in the most) scenarios, but
was super slow to handle permissions. However, it is actually very
limited operations in which the application can do anything, so it is
much easier to just drop privileged user to normal one

src/ahriman/application/handlers/setup.py

@@ -72,14 +72,16 @@ class Setup(Handler):
 
         application = Application(repository_id, configuration, report=report)
 
-        with application.repository.paths.preserve_owner():
-            Setup.configuration_create_makepkg(args.packager, args.makeflags_jobs, application.repository.paths)
-            Setup.executable_create(application.repository.paths, repository_id)
-            repository_server = f"file://{application.repository.paths.repository}" if args.server is None else args.server
-            Setup.configuration_create_devtools(
-                repository_id, args.from_configuration, args.mirror, args.multilib, repository_server)
-            Setup.configuration_create_sudo(application.repository.paths, repository_id)
+        # basically we create configuration here as root, but it is ok, because those files are only used for reading
+        Setup.configuration_create_makepkg(args.packager, args.makeflags_jobs, application.repository.paths)
+        Setup.executable_create(application.repository.paths, repository_id)
+        repository_server = f"file://{application.repository.paths.repository}" if args.server is None else args.server
+        Setup.configuration_create_devtools(
+            repository_id, args.from_configuration, args.mirror, args.multilib, repository_server)
+        Setup.configuration_create_sudo(application.repository.paths, repository_id)
 
+        # finish initialization
+        with application.repository.paths.preserve_owner():
             application.repository.repo.init()
             # lazy database sync
             application.repository.pacman.handle  # pylint: disable=pointless-statement

src/ahriman/core/alpm/pacman.py

@@ -130,7 +130,7 @@ class Pacman(LazyLogging):
             return  # database for some reason deos not exist
 
         self.logger.info("copy pacman database %s from operating system root to ahriman's home %s", src, dst)
-        with self.repository_paths.preserve_owner(dst.parent):
+        with self.repository_paths.preserve_owner():
             shutil.copy(src, dst)
 
     def database_init(self, handle: Handle, repository: str, architecture: str) -> DB:

src/ahriman/core/exceptions.py

@@ -20,7 +20,6 @@
 import subprocess
 
 from collections.abc import Callable
-from pathlib import Path
 from typing import Any, Self
 
 from ahriman.models.repository_id import RepositoryId
@@ -229,20 +228,6 @@ class PkgbuildParserError(ValueError):
         ValueError.__init__(self, message)
 
 
-class PathError(ValueError):
-    """
-    exception which will be raised on path which is not belong to root directory
-    """
-
-    def __init__(self, path: Path, root: Path) -> None:
-        """
-        Args:
-            path(Path): path which raised an exception
-            root(Path): repository root (i.e. ahriman home)
-        """
-        ValueError.__init__(self, f"Path `{path}` does not belong to repository root `{root}`")
-
-
 class PasswordError(ValueError):
     """
     exception which will be raised in case of password related errors

src/ahriman/core/utils.py

@@ -54,7 +54,6 @@ __all__ = [
     "pretty_interval",
     "pretty_size",
     "safe_filename",
-    "safe_iterdir",
     "srcinfo_property",
     "srcinfo_property_list",
     "trim_package",
@@ -449,22 +448,6 @@ def safe_filename(source: str) -> str:
     return re.sub(r"[^A-Za-z\d\-._~:\[\]@]", "-", source)
 
 
-def safe_iterdir(path: Path) -> Iterator[Path]:
-    """
-    wrapper around :func:`pathlib.Path.iterdir`, which suppresses :exc:`PermissionError`
-
-    Args:
-        path(Path): path to iterate
-
-    Yields:
-        Path: content of the directory
-    """
-    try:
-        yield from path.iterdir()
-    except PermissionError:
-        pass
-
-
 def srcinfo_property(key: str, srcinfo: Mapping[str, Any], package_srcinfo: Mapping[str, Any], *,
                      default: Any = None) -> Any:
     """

src/ahriman/models/repository_paths.py

@@ -27,9 +27,8 @@ from functools import cached_property
 from pathlib import Path
 from pwd import getpwuid
 
-from ahriman.core.exceptions import PathError
 from ahriman.core.log import LazyLogging
-from ahriman.core.utils import owner, safe_iterdir
+from ahriman.core.utils import owner
 from ahriman.models.repository_id import RepositoryId
 
 
@@ -209,33 +208,6 @@ class RepositoryPaths(LazyLogging):
 
         return set(walk(instance))
 
-    def _chown(self, path: Path) -> None:
-        """
-        set owner of path recursively (from root) to root owner
-
-        Notes:
-            More likely you don't want to call this method explicitly, consider using :func:`preserve_owner`
-            as context manager instead
-
-        Args:
-            path(Path): path to be chown
-
-        Raises:
-            PathError: if path does not belong to root
-        """
-        def set_owner(current: Path) -> None:
-            uid, gid = owner(current)
-            if uid == root_uid and gid == root_gid:
-                return
-            os.chown(current, root_uid, root_gid, follow_symlinks=False)
-
-        if self.root not in path.parents:
-            raise PathError(path, self.root)
-        root_uid, root_gid = self.root_owner
-        while path != self.root:
-            set_owner(path)
-            path = path.parent
-
     def cache_for(self, package_base: str) -> Path:
         """
         get path to cached PKGBUILD and package sources for the package base
@@ -249,13 +221,10 @@ class RepositoryPaths(LazyLogging):
         return self.cache / package_base
 
     @contextlib.contextmanager
-    def preserve_owner(self, path: Path | None = None) -> Iterator[None]:
+    def preserve_owner(self) -> Iterator[None]:
         """
         perform any action preserving owner for any newly created file or directory
 
-        Args:
-            path(Path | None, optional): use this path as root instead of repository root (Default value = None)
-
         Examples:
             This method is designed to use as context manager when you are going to perform operations which might
             change filesystem, especially if you are doing it under unsafe flag, e.g.::
@@ -266,25 +235,26 @@ class RepositoryPaths(LazyLogging):
             Note, however, that this method doesn't handle any exceptions and will eventually interrupt
             if there will be any.
         """
-        path = path or self.root
+        # guard non-root
+        # the reason we do this is that it only works if permissions can be actually changed. Hence,
+        # non-privileged user (e.g. personal user or ahriman user) can't change permissions.
+        # The only one who can do so is root, so if user is not root we just terminate function
+        current_uid, current_gid = os.getuid(), os.getgid()
+        if current_uid != 0:
+            yield
+            return
 
-        def walk(root: Path) -> Iterator[Path]:
-            # basically walk, but skipping some content
-            for child in safe_iterdir(root):
-                yield child
-                if child in (self.chroot.parent,):
-                    yield from safe_iterdir(child)  # we only yield top-level in chroot directory
-                elif child.is_dir():
-                    yield from walk(child)
+        # set uid and gid to root owner
+        target_uid, target_gid = self.root_owner
+        os.setegid(target_gid)
+        os.seteuid(target_uid)
 
-        # get current filesystem and run action
-        previous_snapshot = set(walk(path))
-        yield
-
-        # get newly created files and directories and chown them
-        new_entries = set(walk(path)).difference(previous_snapshot)
-        for entry in new_entries:
-            self._chown(entry)
+        try:
+            yield
+        finally:
+            # reset uid and gid
+            os.seteuid(current_uid)
+            os.setegid(current_gid)
 
     def tree_clear(self, package_base: str) -> None:
         """

tests/ahriman/core/alpm/test_pacman.py

@@ -67,7 +67,7 @@ def test_database_copy(pacman: Pacman, mocker: MockerFixture) -> None:
     pacman.database_copy(pacman.handle, database, path, use_ahriman_cache=True)
     mkdir_mock.assert_called_once_with(mode=0o755, exist_ok=True)
     copy_mock.assert_called_once_with(path / "sync" / "core.db", dst_path)
-    owner_guard_mock.assert_called_once_with(dst_path.parent)
+    owner_guard_mock.assert_called_once_with()
 
 
 def test_database_copy_skip(pacman: Pacman, mocker: MockerFixture) -> None:

tests/ahriman/core/test_utils.py

@@ -436,17 +436,6 @@ def test_safe_filename() -> None:
     assert safe_filename("tolua++-1.0.93-4-x86_64.pkg.tar.zst") == "tolua---1.0.93-4-x86_64.pkg.tar.zst"
 
 
-def test_safe_iterdir(mocker: MockerFixture, resource_path_root: Path) -> None:
-    """
-    must suppress PermissionError
-    """
-    assert list(safe_iterdir(resource_path_root))
-
-    iterdir_mock = mocker.patch("pathlib.Path.iterdir", side_effect=PermissionError)
-    assert list(safe_iterdir(Path("root"))) == []
-    iterdir_mock.assert_called_once_with()
-
-
 def test_srcinfo_property() -> None:
     """
     must correctly extract properties

tests/ahriman/models/test_repository_paths.py

@@ -3,9 +3,8 @@ import pytest
 from collections.abc import Callable
 from pathlib import Path
 from pytest_mock import MockerFixture
-from unittest.mock import MagicMock, call as MockCall
+from unittest.mock import call as MockCall
 
-from ahriman.core.exceptions import PathError
 from ahriman.models.package import Package
 from ahriman.models.repository_id import RepositoryId
 from ahriman.models.repository_paths import RepositoryPaths
@@ -186,56 +185,6 @@ def test_known_repositories_empty(repository_paths: RepositoryPaths, mocker: Moc
     iterdir_mock.assert_not_called()
 
 
-def test_chown(repository_paths: RepositoryPaths, mocker: MockerFixture) -> None:
-    """
-    must correctly set owner for the directory
-    """
-    mocker.patch("ahriman.models.repository_paths.owner", _get_owner(repository_paths.root, same=False))
-    mocker.patch.object(RepositoryPaths, "root_owner", (42, 42))
-    chown_mock = mocker.patch("os.chown")
-
-    path = repository_paths.root / "path"
-    repository_paths._chown(path)
-    chown_mock.assert_called_once_with(path, 42, 42, follow_symlinks=False)
-
-
-def test_chown_parent(repository_paths: RepositoryPaths, mocker: MockerFixture) -> None:
-    """
-    must correctly set owner for the directory including parents
-    """
-    mocker.patch("ahriman.models.repository_paths.owner", _get_owner(repository_paths.root, same=False))
-    mocker.patch.object(RepositoryPaths, "root_owner", (42, 42))
-    chown_mock = mocker.patch("os.chown")
-
-    path = repository_paths.root / "parent" / "path"
-    repository_paths._chown(path)
-    chown_mock.assert_has_calls([
-        MockCall(path, 42, 42, follow_symlinks=False),
-        MockCall(path.parent, 42, 42, follow_symlinks=False)
-    ])
-
-
-def test_chown_skip(repository_paths: RepositoryPaths, mocker: MockerFixture) -> None:
-    """
-    must skip ownership set in case if it is same as root
-    """
-    mocker.patch("ahriman.models.repository_paths.owner", _get_owner(repository_paths.root, same=True))
-    mocker.patch.object(RepositoryPaths, "root_owner", (42, 42))
-    chown_mock = mocker.patch("os.chown")
-
-    path = repository_paths.root / "path"
-    repository_paths._chown(path)
-    chown_mock.assert_not_called()
-
-
-def test_chown_invalid_path(repository_paths: RepositoryPaths) -> None:
-    """
-    must raise invalid path exception in case if directory outside the root supplied
-    """
-    with pytest.raises(PathError):
-        repository_paths._chown(repository_paths.root.parent)
-
-
 def test_cache_for(repository_paths: RepositoryPaths, package_ahriman: Package) -> None:
     """
     must return correct path for cache directory
@@ -249,30 +198,49 @@ def test_preserve_owner(tmp_path: Path, repository_id: RepositoryId, mocker: Moc
     """
     must preserve file owner during operations
     """
+    mocker.patch("os.getuid", return_value=0)
+    mocker.patch("os.getgid", return_value=0)
+    seteuid_mock = mocker.patch("os.seteuid")
+    setegid_mock = mocker.patch("os.setegid")
+
     repository_paths = RepositoryPaths(tmp_path, repository_id)
+    target_uid, target_gid = repository_paths.root_owner
     repository_paths.tree_create()
-    chown_mock = mocker.patch("ahriman.models.repository_paths.RepositoryPaths._chown")
-
-    with repository_paths.preserve_owner():
-        (repository_paths.root / "created1").touch()
-        (repository_paths.chroot / "created2").touch()
-    chown_mock.assert_has_calls([MockCall(repository_paths.root / "created1")])
+    seteuid_mock.assert_has_calls([MockCall(target_uid), MockCall(0)])
+    setegid_mock.assert_has_calls([MockCall(target_gid), MockCall(0)])
 
 
-def test_preserve_owner_specific(tmp_path: Path, repository_id: RepositoryId, mocker: MockerFixture) -> None:
+def test_preserve_owner_exception(tmp_path: Path, repository_id: RepositoryId, mocker: MockerFixture) -> None:
     """
-    must preserve file owner during operations only in specific directory
+    must return to original uid and gid even during exception
     """
+    mocker.patch("os.getuid", return_value=0)
+    mocker.patch("os.getgid", return_value=0)
+    mocker.patch("pathlib.Path.mkdir", side_effect=Exception)
+    seteuid_mock = mocker.patch("os.seteuid")
+    setegid_mock = mocker.patch("os.setegid")
+
     repository_paths = RepositoryPaths(tmp_path, repository_id)
-    repository_paths.tree_create()
-    (repository_paths.root / "content").mkdir()
-    chown_mock = mocker.patch("ahriman.models.repository_paths.RepositoryPaths._chown")
+    target_uid, target_gid = repository_paths.root_owner
+    with pytest.raises(Exception):
+        repository_paths.tree_create()
+    seteuid_mock.assert_has_calls([MockCall(target_uid), MockCall(0)])
+    setegid_mock.assert_has_calls([MockCall(target_gid), MockCall(0)])
 
-    with repository_paths.preserve_owner(repository_paths.root / "content"):
-        (repository_paths.root / "created1").touch()
-        (repository_paths.root / "content" / "created2").touch()
-        (repository_paths.chroot / "created3").touch()
-    chown_mock.assert_has_calls([MockCall(repository_paths.root / "content" / "created2")])
+
+def test_preserve_owner_non_root(tmp_path: Path, repository_id: RepositoryId, mocker: MockerFixture) -> None:
+    """
+    must skip processing if user is not root
+    """
+    mocker.patch("os.getuid", return_value=42)
+    mocker.patch("os.getgid", return_value=42)
+    repository_paths = RepositoryPaths(tmp_path, repository_id)
+    seteuid_mock = mocker.patch("os.seteuid")
+    setegid_mock = mocker.patch("os.setegid")
+
+    repository_paths.tree_create()
+    seteuid_mock.assert_not_called()
+    setegid_mock.assert_not_called()
 
 
 def test_tree_clear(repository_paths: RepositoryPaths, package_ahriman: Package, mocker: MockerFixture) -> None: