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

[Christopher Lemmer Webber <cwebber@dustycloud.org>]

raingloom writes:

> On Mon, 23 Nov 2020 03:32:08 +0100
> Taylan Kammer <taylan.kammer@gmail.com> wrote:
>
>> On 23.11.2020 00:20, Christopher Lemmer Webber wrote:
>> > Okay, I just realized I left a friend vulnerable by guiding them
>> > through a Guix graphical install and telling them it would give
>> > them a decent setup.  They turned on openssh support.
>> > 
>> > Then I realized their config had password-authentication? on.
>> > 
>> > That's unacceptable.  We need to change this default.  This is
>> > known to leave users open to attack, and selecting a password
>> > secure enough against brute forcing is fairly difficult, much more
>> > difficult than only allowing entry by keys.  Plus, few
>> > distributions do what we're doing anymore, precisely because of
>> > wanting to be secure by default.
>> > 
>> > Yes, I know some people want password authentication on as part of a
>> > bootstrapping process.  Fine... those users know to put it on.
>> > Let's not leave our users open to attack by default though.
>> > 
>> > Happy to produce a patch and change the documentation, but I'd like
>> > to hear that we have consensus to make this change.  But we should,
>> > because otherwise else I think we're going to hurt users.  
>> 
>> I think most ideal would be if the user is asked the following two 
>> questions, with a short explanation of what each means:
>> 
>> - Allow root login via SSH?
>> 
>> - Allow password authentication in SSH?
>> 
>> (I think Debian does this.)
>> 
>> Because as you say, on one hand password authentication in SSH can be
>> a security risk.  But on the other hand many machines never have
>> their SSH port exposed to the Internet, and the intranet is assumed
>> to be safe. In those cases it would be an annoyance to have to enable
>> it manually.
>> 
>> Both points apply to direct root login as well I think.
>> 
>> Allowing password authentication but disabling root login might also
>> be considered safe enough on machines exposed to the Internet,
>> because the attacker needs to guess the username as well.  Only
>> presents a small increase in complexity for the attacker though.
>> 
>> 
>> - Taylan
>> 
>> 
>> 
>
> Most people won't know why allowing password authentication is
> unsecure. Either it should be worded differently, have a warning, or
> not be an option.
>
> Same goes doubly so for allowing root login.

Agreed on both counts.