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

[Leo Famulari]

On Sat, Dec 05, 2020 at 01:22:23PM -0500, Christopher Lemmer Webber wrote:
> >   2. Change the default value of the relevant field in
> >      <openssh-configuration>.
> >
> > #2 is more thorough but also more risky: people could find themselves
> > locked out of their server after reconfiguration, though this could be
> > mitigated by a news entry.

I do think we should avoid changing the default. I know that passphrases
are inherently riskier than keys — compromise is more likely than with a
key, but I think it's even more likely that people will lose access to
their servers if we change this default.

How bad is the risk, from a practical perspective? How many times per
second can a remote attacker attempt passphrase authentication? If the
number is high, we could petition OpenSSH to introduce a delay.