pre-commit · asottile · May 23, 2025 · Apr 13, 2025
diff --git a/pre_commit/languages/docker.py b/pre_commit/languages/docker.py
@@ -1,5 +1,6 @@
 from __future__ import annotations
 
+import functools
 import hashlib
 import json
 import os
@@ -101,7 +102,32 @@ def install_environment(
     os.mkdir(directory)
 
 
+@functools.lru_cache(maxsize=1)
+def _is_rootless() -> bool:  # pragma: win32 no cover
+    retcode, out, _ = cmd_output_b(
+        'docker', 'system', 'info', '--format', '{{ json . }}',
+    )
+    if retcode != 0:
+        return False
+
+    info = json.loads(out)
+    try:
+        return (
+            # docker:
+            # https://docs.docker.com/reference/api/engine/version/v1.48/#tag/System/operation/SystemInfo
+            'name=rootless' in info.get('SecurityOptions', ()) or
+            # podman:
+            # https://docs.podman.io/en/latest/_static/api.html?version=v5.4#tag/system/operation/SystemInfoLibpod
+            info['host']['security']['rootless']
+        )
+    except KeyError:
+        return False
+
+
 def get_docker_user() -> tuple[str, ...]:  # pragma: win32 no cover
+    if _is_rootless():
+        return ()
+
     try:
         return ('-u', f'{os.getuid()}:{os.getgid()}')
     except AttributeError:

diff --git a/tests/languages/docker_test.py b/tests/languages/docker_test.py
@@ -62,6 +62,42 @@ def invalid_attribute():
         assert docker.get_docker_user() == ()
 
 
+@pytest.fixture(autouse=True)
+def _avoid_cache():
+    with mock.patch.object(
+            docker,
+            '_is_rootless',
+            docker._is_rootless.__wrapped__,
+    ):
+        yield
+
+
+@pytest.mark.parametrize(
+    'info_ret',
+    (
+        (0, b'{"SecurityOptions": ["name=rootless","name=cgroupns"]}', b''),
+        (0, b'{"host": {"security": {"rootless": true}}}', b''),
+    ),
+)
+def test_docker_user_rootless(info_ret):
+    with mock.patch.object(docker, 'cmd_output_b', return_value=info_ret):
+        assert docker.get_docker_user() == ()
+
+
+@pytest.mark.parametrize(
+    'info_ret',
+    (
+        (0, b'{"SecurityOptions": ["name=cgroupns"]}', b''),
+        (0, b'{"host": {"security": {"rootless": false}}}', b''),
+        (0, b'{"respone_from_some_other_container_engine": true}', b''),
+        (1, b'', b''),
+    ),
+)
+def test_docker_user_non_rootless(info_ret):
+    with mock.patch.object(docker, 'cmd_output_b', return_value=info_ret):
+        assert docker.get_docker_user() != ()
+
+
 def test_in_docker_no_file():
     with mock.patch.object(builtins, 'open', side_effect=FileNotFoundError):
         assert docker._is_in_docker() is False
@@ -195,3 +231,14 @@ def test_docker_hook(tmp_path):
 
     ret = run_language(tmp_path, docker, 'echo hello hello world')
     assert ret == (0, b'hello hello world\n')
+
+
+@xfailif_windows  # pragma: win32 no cover
+def test_docker_hook_mount_permissions(tmp_path):
+    dockerfile = '''\
+FROM ubuntu:22.04
+'''
+    tmp_path.joinpath('Dockerfile').write_text(dockerfile)
+
+    retcode, _ = run_language(tmp_path, docker, 'touch', ('README.md',))
+    assert retcode == 0