osutils: WriteFile: support append+sudo using dd
BUG=chromium:1050646
TEST=CQ passes
Change-Id: I3eb97c0cf35e465a4ffa8166ff3150732c619955
Reviewed-on: https://chromium-review.googlesource.com/c/chromiumos/chromite/+/2067184
Commit-Queue: Mike Frysinger <vapier@chromium.org>
Tested-by: Mike Frysinger <vapier@chromium.org>
Reviewed-by: Andrew Lassalle <andrewlassalle@chromium.org>
diff --git a/lib/osutils.py b/lib/osutils.py
index c463bba..8814b9c 100644
--- a/lib/osutils.py
+++ b/lib/osutils.py
@@ -140,8 +140,8 @@
raise ValueError('mode must be one of {"%s"}, not %r' %
('", "'.join(sorted(_VALID_WRITE_MODES)), mode))
- if sudo and ('a' in mode or '+' in mode):
- raise ValueError('append mode does not work in sudo mode')
+ if sudo and atomic and ('a' in mode or '+' in mode):
+ raise ValueError('append mode does not work in sudo+atomic mode')
if 'b' in mode:
if encoding is not None or errors is not None:
@@ -168,24 +168,33 @@
# If the file needs to be written as root and we are not root, write to a temp
# file, move it and change the permission.
if sudo and os.getuid() != 0:
- with tempfile.NamedTemporaryFile(mode=mode, delete=False) as temp:
- write_path = temp.name
- temp.writelines(write_wrapper(cros_build_lib.iflatten_instance(content)))
- os.chmod(write_path, 0o644)
+ if 'a' in mode or '+' in mode:
+ # Use dd to run through sudo & append the output, and write the new data
+ # to it through stdin.
+ cros_build_lib.sudo_run(
+ ['dd', 'conv=notrunc', 'oflag=append', 'status=none',
+ 'of=%s' % (path,)], print_cmd=False, input=content)
- try:
- mv_target = path if not atomic else path + '.tmp'
- cros_build_lib.sudo_run(['mv', write_path, mv_target],
- print_cmd=False, stderr=True)
- Chown(mv_target, user='root', group='root')
- if atomic:
- cros_build_lib.sudo_run(['mv', mv_target, path],
+ else:
+ with tempfile.NamedTemporaryFile(mode=mode, delete=False) as temp:
+ write_path = temp.name
+ temp.writelines(write_wrapper(
+ cros_build_lib.iflatten_instance(content)))
+ os.chmod(write_path, 0o644)
+
+ try:
+ mv_target = path if not atomic else path + '.tmp'
+ cros_build_lib.sudo_run(['mv', write_path, mv_target],
print_cmd=False, stderr=True)
+ Chown(mv_target, user='root', group='root')
+ if atomic:
+ cros_build_lib.sudo_run(['mv', mv_target, path],
+ print_cmd=False, stderr=True)
- except cros_build_lib.RunCommandError:
- SafeUnlink(write_path)
- SafeUnlink(mv_target)
- raise
+ except cros_build_lib.RunCommandError:
+ SafeUnlink(write_path)
+ SafeUnlink(mv_target)
+ raise
else:
# We have the right permissions, simply write the file in python.
diff --git a/lib/osutils_unittest.py b/lib/osutils_unittest.py
index 43f976a..619372d 100644
--- a/lib/osutils_unittest.py
+++ b/lib/osutils_unittest.py
@@ -90,10 +90,14 @@
self.assertEqual('test', osutils.ReadFile(filename))
self.assertEqual(0, os.stat(filename).st_uid)
- # Appending to a file is not supported with sudo.
- self.assertRaises(ValueError, osutils.WriteFile,
- os.path.join(root_owned_dir, 'nope'), 'data',
- sudo=True, mode='a')
+ def testSudoWriteAppend(self):
+ """Verify that we can write a file as sudo when appending."""
+ with osutils.TempDir(sudo_rm=True) as tempdir:
+ path = os.path.join(tempdir, 'foo')
+ osutils.WriteFile(path, 'one', sudo=True)
+ self.assertRaises(IOError, osutils.WriteFile, path, 'data')
+ osutils.WriteFile(path, 'two', mode='a', sudo=True)
+ self.assertEqual('onetwo', osutils.ReadFile(path))
def testReadFileNonExistent(self):
"""Verify what happens if you ReadFile a file that isn't there."""
