From f5b3ad741679cd42d2c145e574168dafe3ac15c1 Mon Sep 17 00:00:00 2001
From: Daniel Watkins <oddbloke@ubuntu.com>
Date: Fri, 23 Oct 2020 15:20:18 -0400
Subject: [PATCH] stages: don't reset permissions of cloud-init.log every boot
 (#624)

ensure_file needed modification to support doing this, so this commit
also includes the following changes:

test_util: add tests for util.ensure_file
util: add preserve_mode parameter to ensure_file
util: add (partial) type annotations to ensure_file

LP: #1900837
---
 cloudinit/stages.py            |  2 +-
 cloudinit/tests/test_util.py   | 45 ++++++++++++++++++++++++
 cloudinit/util.py              |  8 +++--
 3 files changed, 52 insertions(+), 3 deletions(-)

diff --git a/cloudinit/stages.py b/cloudinit/stages.py
index 765f4aab..0cce6e80 100644
--- a/cloudinit/stages.py
+++ b/cloudinit/stages.py
@@ -148,7 +148,7 @@ class Init(object):
         util.ensure_dirs(self._initial_subdirs())
         log_file = util.get_cfg_option_str(self.cfg, 'def_log_file')
         if log_file:
-            util.ensure_file(log_file)
+            util.ensure_file(log_file, preserve_mode=True)
             perms = self.cfg.get('syslog_fix_perms')
             if not perms:
                 perms = {}
diff --git a/cloudinit/tests/test_util.py b/cloudinit/tests/test_util.py
index 096a3037..77714928 100644
--- a/cloudinit/tests/test_util.py
+++ b/cloudinit/tests/test_util.py
@@ -771,4 +771,49 @@ class TestRedirectOutputPreexecFn:
 
         assert 0 == m_setgid.call_count
 
+@mock.patch("cloudinit.util.write_file")
+class TestEnsureFile:
+    """Tests for ``cloudinit.util.ensure_file``."""
+
+    def test_parameters_passed_through(self, m_write_file):
+        """Test the parameters in the signature are passed to write_file."""
+        util.ensure_file(
+            mock.sentinel.path,
+            mode=mock.sentinel.mode,
+            preserve_mode=mock.sentinel.preserve_mode,
+        )
+
+        assert 1 == m_write_file.call_count
+        args, kwargs = m_write_file.call_args
+        assert (mock.sentinel.path,) == args
+        assert mock.sentinel.mode == kwargs["mode"]
+        assert mock.sentinel.preserve_mode == kwargs["preserve_mode"]
+
+    @pytest.mark.parametrize(
+        "kwarg,expected",
+        [
+            # Files should be world-readable by default
+            ("mode", 0o644),
+            # The previous behaviour of not preserving mode should be retained
+            ("preserve_mode", False),
+        ],
+    )
+    def test_defaults(self, m_write_file, kwarg, expected):
+        """Test that ensure_file defaults appropriately."""
+        util.ensure_file(mock.sentinel.path)
+
+        assert 1 == m_write_file.call_count
+        _args, kwargs = m_write_file.call_args
+        assert expected == kwargs[kwarg]
+
+    def test_static_parameters_are_passed(self, m_write_file):
+        """Test that the static write_files parameters are passed correctly."""
+        util.ensure_file(mock.sentinel.path)
+
+        assert 1 == m_write_file.call_count
+        _args, kwargs = m_write_file.call_args
+        assert "" == kwargs["content"]
+        assert "ab" == kwargs["omode"]
+
+
 # vi: ts=4 expandtab
diff --git a/cloudinit/util.py b/cloudinit/util.py
index e47f1cf6..83727544 100644
--- a/cloudinit/util.py
+++ b/cloudinit/util.py
@@ -1804,8 +1804,10 @@ def append_file(path, content):
     write_file(path, content, omode="ab", mode=None)
 
 
-def ensure_file(path, mode=0o644):
-    write_file(path, content='', omode="ab", mode=mode)
+def ensure_file(path, mode=0o644, preserve_mode=False):
+    write_file(
+        path, content="", omode="ab", mode=mode, copy_mode=preserve_mode
+    )
 
 
 def safe_int(possible_int):
-- 
2.27.0