Writing files uses unsafe patterns in the tripleo client

[Bogdan Dobrelya]

As Steve noticed in https://review.openstack.org/#/c/542875/26/tripleoclient/v1/undercloud_config.py, such a pattern risks a corrupted file if a new file is shorter than the old file. At some point this needs to be changed to http://git.openstack.org/cgit/openstack/heat-agents/tree/heat-config-ansible/install.d/hook-ansible.py#n73

There are more places to inspect.

[OpenStack Infra (hudson-openstack)]

Fix proposed to branch: master
Review: https://review.openstack.org/553604

[Ben Nemec (bnemec)]

This is not true. Opening a file for 'w' access in Python truncates it immediately. You don't even have to write anything to it.

[bnemec@RedHat tmp]$ echo foo > foo
[bnemec@RedHat tmp]$ cat foo
foo
[bnemec@RedHat tmp]$ python
Python 2.7.14 (default, Dec 11 2017, 16:08:01)
[GCC 7.2.1 20170915 (Red Hat 7.2.1-2)] on linux2
Type "help", "copyright", "credits" or "license" for more information.
>>> open('foo', 'w')
<open file 'foo', mode 'w' at 0x7f97e4ff7660>
>>>
[bnemec@RedHat tmp]$ cat foo
[bnemec@RedHat tmp]$

The same test with 'wb' behaves the same, so I don't think this is necessary in the heat-agents case either.

[OpenStack Infra (hudson-openstack)]

Change abandoned by Radoslaw Smigielski (<email address hidden>) on branch: master
Review: https://review.openstack.org/553604