full-disclosure - Re: Dropbear SSH server Denial of Service

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Message-ID: <Pine.BSO.4.64.0603111349120.1260@fuyu.mindrot.org>
Date: Sat Mar 11 03:59:07 2006
From: djm at mindrot.org (Damien Miller)
Subject: Re: Dropbear SSH server Denial of Service

On Fri, 10 Mar 2006, Matt Johnston wrote:

> Dropbear 0.48 mitigates this issue by having a per-IP limit
> as well as a global limit - this will at least prevent an
> IP-deprived attacker from denying service.
> 
> It's worth noting that various other network services (such
> as netkit-inetd and OpenSSH) have the same design issues, at
> least in default configurations.

OpenSSH has had connection-flood DoS mitigation since 2000, in the 
form of random early drop of connections so legitimate users have a
probabalistic change of getting in. See the "MaxStartups" documentation
in sshd_config(5)

-d