util: teach write_file about copy_mode option

On centos/fedora/rhel/derivatives, /etc/ssh/sshd_config has mode 0600,
but cloud-init unilaterally sets file modes to 0644 when no explicit
mode is passed to util.write_file. On ubuntu/debian, this file has
mode 0644.  With this patch, write_file learns about the copy_mode
option, which will cause it to use the mode of the existing file by
default, falling back to the explicit mode parameter if the file does
not exist.

LP: #1644064
Resolves: rhbz#1295984

1 files changed, 31 insertions, 2 deletions

diff --git a/tests/unittests/test_util.py b/tests/unittests/test_util.py
index ab74311e..5d21b4b7 100644
--- a/tests/unittests/test_util.py
+++ b/tests/unittests/test_util.py
@@ -103,8 +103,8 @@ class TestWriteFile(helpers.TestCase):
         self.assertTrue(os.path.isdir(dirname))
         self.assertTrue(os.path.isfile(path))
 
-    def test_custom_mode(self):
-        """Verify custom mode works properly."""
+    def test_explicit_mode(self):
+        """Verify explicit file mode works properly."""
         path = os.path.join(self.tmp, "NewFile.txt")
         contents = "Hey there"
 
@@ -115,6 +115,35 @@ class TestWriteFile(helpers.TestCase):
         file_stat = os.stat(path)
         self.assertEqual(0o666, stat.S_IMODE(file_stat.st_mode))
 
+    def test_copy_mode_no_existing(self):
+        """Verify that file is created with mode 0o644 if copy_mode
+        is true and there is no prior existing file."""
+        path = os.path.join(self.tmp, "NewFile.txt")
+        contents = "Hey there"
+
+        util.write_file(path, contents, copy_mode=True)
+
+        self.assertTrue(os.path.exists(path))
+        self.assertTrue(os.path.isfile(path))
+        file_stat = os.stat(path)
+        self.assertEqual(0o644, stat.S_IMODE(file_stat.st_mode))
+
+    def test_copy_mode_with_existing(self):
+        """Verify that file is created using mode of existing file
+        if copy_mode is true."""
+        path = os.path.join(self.tmp, "NewFile.txt")
+        contents = "Hey there"
+
+        open(path, 'w').close()
+        os.chmod(path, 0o666)
+
+        util.write_file(path, contents, copy_mode=True)
+
+        self.assertTrue(os.path.exists(path))
+        self.assertTrue(os.path.isfile(path))
+        file_stat = os.stat(path)
+        self.assertEqual(0o666, stat.S_IMODE(file_stat.st_mode))
+
     def test_custom_omode(self):
         """Verify custom omode works properly."""
         path = os.path.join(self.tmp, "NewFile.txt")