bug#44808: Default to allowing password authentication on leaves users vulnerable

[Leo Famulari]

On Thu, Feb 11, 2021 at 07:46:51AM +0000, raid5atemyhomework via Bug reports 
for GNU Guix wrote:
> Hi guix users,
> 
> It strikes me that a better course of action here would be, rather than 
> providing a warning that might not be noticed by the user, to remove the 
> default and force people to explicitly put `password-authentication? #t` or 
> `password-authentication? #f`.

I like this idea.

> 
> That way if I have set up a headless server (possibly having a temporary 
> keyboard/mouse/monitor during initial install, then forever logging in 
> afterwards over intranet using my super secret password 
> "raid5isnotagooddog"), with an existing `configuration.scm` that does not 
> explicitly give the setting, I cannot accidentally lose access to my headless 
> server by doing a random `guix pull && sudo guix system reconfigure 
> configuration.scm` without noticing the warning.
> 
> Especially since there exists an `unattended-upgrades-service-type` which 
> automates this `guix pull && sudo guix system reconfigure configuration.scm`, 
> which makes changing this default ***VERY DANGEROUS*** in this use-case.  I'd 
> rather I noticeably error out in this case.

I agree, changing the default will cause problems, and I'm not convinced
it's a serious problem that warrants changing anyways.