full-disclosure - Re: OpenSSH - System Account Enumeration if S/Key is used

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Date: Tue, 24 Apr 2007 10:06:58 -0400
From: "Brian Eaton" <eaton.lists@...il.com>
To: "Stanislaw Klekot" <dozzie@...amit.im.pwr.wroc.pl>
Cc: full-disclosure@...ts.grok.org.uk, rembrandt <rembrandt@...ith.org>
Subject: Re: OpenSSH - System Account Enumeration if S/Key
	is used

On 4/24/07, Stanislaw Klekot <dozzie@...amit.im.pwr.wroc.pl> wrote:
> Look closer to challenge message. There's salt and key number included.
> Consider now three logins: first isn't valid account on the target
> system, second is valid but without OTP set, and third with OTP set.
> First two are indistinguishable for attacker as in these cases system
> presents random challenge, but for third account system will present the
> same challenge over and over again.
>
> How about that?

Perhaps rather than presenting a random challenge, the challenge could
be based on a hash of the account name used and a per-system salt?

Regards,
Brian

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