Re: sshd permits logon using disabled user?

[Stefan Baur <X2Go-ML-1@baur-itcs.de>]

Am 25.01.19 um 05:42 schrieb matthew patton via cygwin:
> Why is this even a discussion? You *ALWAYS* refuse a login to an account that is disabled, locked out, or has an expired password or failed any of the other criteria that might be in effect (day/time restrictions, source IP restrictions, etc.)

Not on Linux (and possibly other Unices).  There, it's perfectly valid
to disable an account's password login (both locally and remote), but to
at the same time allow ssh key file based logins for the same account.

Since cygwin aims to be Linux-/POSIX-compatible to a certain degree, it
is indeed worthy of discussion - even if the final decision might be to
just block logins completely, even with an ssh key pair.

Before Corinna pushed her fix, it was possible to log in via SSH key,
even when the account was locked out/disabled.  Someone might have been
using that "feature" on cygwin, knowing it from Linux, where it is
indeed a feature/design choice.

If this fix hits stable, the same people might be wondering why their
ssh logins fail all of a sudden.

This could be a scenario for scripted uploads via rsync/scp/sftp, for
example, where people are using ssh keys locked down to certain
commands.  You just don't want that user account to be able to log in
with only a password, ever - because the only reason that would happen
would be an account compromise.  And because of that, having a "there is
no valid password for this account, you can try as hard as you like"
setting makes more sense than just setting a long and complex password
that hopefully no one ever guesses/bruteforces/sidechannel-hacks/...

Kind Regards,
Stefan Baur


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