any netplan config for wifi devices should not be world readable

This bug was originally filed in Launchpad as [LP: #1726651](https://bugs.launchpad.net/cloud-init/+bug/1726651)

Launchpad details

affected_projects = ['curtin']

assignee = None

assignee_name = None

date_closed = None

date_created = 2017-10-24T01:05:05.231760+00:00

date_fix_committed = None

date_fix_released = None

id = 1726651

importance = medium

is_complete = False

lp_url = https://bugs.launchpad.net/cloud-init/+bug/1726651

milestone = None

owner = mwhudson

owner_name = Michael Hudson-Doyle

private = False

status = confirmed

submitter = mwhudson

submitter_name = Michael Hudson-Doyle

tags = ['id-59ea6cab4da427a5652de7a3', 'id-59ea6cd3cd57bbca34370d52']

duplicates = []

_Launchpad user **Michael Hudson-Doyle(mwhudson)** wrote on 2017-10-24T01:05:05.231760+00:00_

Currently, as near as I can tell, curtin writes netplan config to a world readable file in /etc/cloud/ and cloud-init writes it to a world readable file in /etc/netplan. But if there are any wpa2 psks in the config they should be put in a 0600 file.

This doesn't really make any sense for actual clouds, but subiquity should be able to get this right.

One way to do this would be for cloud-init to check through the provided config and put wifis in a separate file or another would be for there to be a way to direct cloud-init to write different parts of the netplan config to different files and a way to set the modes of those files (neither of which appears to be possible today), and for curtin to make use of that. I don't really care :)