Full Disclosure mailing list archives
Re: reduction of brute force login attempts via SSHthrough iptables --hashlimit
From: "GroundZero Security" <fd () g-0 org>
Date: Thu, 2 Mar 2006 14:47:01 +0100
Oh well...as i said its a QUICK script and not a PERFECT solution to the problem. I made it for personal use originally and it does its job..sofar i NEVER had problems with it and usually an attacker wont know you run it (i know thats not an execuse). Anyhow its no problem at all to modify, so if you dont like it, just dont use it.
Please note that this entire script can ALL be done in 1, count them 1, awk command. (sed as well, but not worth it).
ok so show me that 1 awk command that replaces the entire script...
If you are going to ATTEMPT to do something, at least use documented options. It's ``grep -A1'' not ``grep -1''. Then a pipe into sed THEN into awk?
After all it works. There are always more ways to do it, but if its -A1 or -1 really doesnt matter at all, its just you have to be pedantic over it i guess. Yep im not a bash guru maybe,but i really dont care much for optimization on a lame script like this as long as it WORKS and is not insecure.
Which brings me to another point. Your use of static temp files in the current working directory is just... my god.
Well this script is not ment to be run from a directory that normal users can access. I know that temporary files can be dangferous but not in a case where a normal user cant access the temp files i.e. if you run it from /root/bruteblock/ or so.
Ohh, we are almost done! I liked symlinking m to /dev/urandom. It made me feel good about myself.
Looks like you have too much time on your hands. Do something productive instead.
That just makes no sense, yet again. Here is where you would use -1, but with ls(documented and valid switch unlike in grep).
I used a different approach that works out. You can do it that way, i do it this way.
:( Your not blocking lIP did not matter, like it would anyways. You made me sad. Notice your pattern match just LOVED accepting 0.0.0.0/0.
Well this script asumes that your local users dont do stupid things. If you manage to get the script to block 0.0.0.0/0 remotely then let me know. Thats something i would change, but for now i dont feel like wasting time over this script. It was a simple and quick solution and does its job unless you cant trust your local users. In that case you should put it in a directory that only root can access like it is ment to be. Anyhow as i said i originally made it for personal use and i dont give my users shell access. Anyhow just thought someone else may have a use for it whos annoyed by those ssh bruteforce attempts. Its nice of you to point out problems though. Sure you could optimize it, but that would only speed up the script which isnt needed in my opinion unless you run Linux on your c64 then i would worry about resource consumption. If you really think it sucks sooo much that you cant take it, then before you reply to this mail now, go and optimize it and send your version to FD then you can be happy and feel superior :-) -sk ----- Original Message ----- From: "nocfed" <nocfed () gmail com> To: <full-disclosure () lists grok org uk> Sent: Thursday, March 02, 2006 1:48 PM Subject: Re: [Full-disclosure] reduction of brute force login attempts via SSHthrough iptables --hashlimit
On 3/1/06, GroundZero Security <fd () g-0 org> wrote:Well i had a few minutes time, so i updated the script a bit. I did not use lastb though, as it wouldnt work (read the manpage.....) Anyhow, maybe someone found it usefull so here is v.0.2 : http://www.groundzero-security.com/code/bruteforce-block.sh Any suggestions are welcome, insults and flames can be sent to /dev/null -sk GroundZero Security Research and Software Development http://www.groundzero-security.com Wir widersprechen der Nutzung oder Übermittlung unserer Daten für Werbezwecke oder für die Markt- oder Meinungsforschung (§ 28 Abs. 4 BDSG). pub 1024D/69928CB8 2004-09-27 Stefan Klaas <sk () groundzero-security com> sub 2048g/2A3C7800 2004-09-27 Key fingerprint = A93E 41F8 7E82 5F2C 3E76 41F1 4BCF 3096 6992 8CB8 -----BEGIN PGP PUBLIC KEY BLOCK----- Version: GnuPG v1.0.6 (GNU/Linux) Comment: For info see http://www.gnupg.org mQGiBEFX440RBADGTKOgZR9Y9VA/cfNLWTIN/OmXe9l6UZJ6pY8Hqcv6DFE//Kt9 UfQMU470i+I7SvIHZN066Kl4ts4r90sLxXrE4r5VQCLTsJM68cliatrM8MbbZZs+ xf3ldelZrHNvHkXDk4I/n3O56F9M6tZ/S71AIj++raIbFX57fn8Z8NNOnwCgwDr6 LDVP+5N4DML1/+uvXNtoL30D/A/GUXd6lJ8i7MoZMzwKk1uwDsgWwP+Wm0hMwJMr fR/di9K55pGdlGFNO5P2L3qOl2BaC8raNkLcXaweW+bao3P66nzpdtmecsjCMWq2 tQWgu/O7S1FgzlUAKJSOc2Th5PY9Raum8bXnSv4gnHZCKjNskIdrz8WDxCzEoPtZ eCssA/9ydHRvNIPjOTmzjXoE+UbJrB/U//u3dpAsLkzclKeSgjV2eYUgHGcqYn+H cFoubD78yFWqZqYtxfiyjBlItsIn9ls0gAZFKDFHd1XfOLFSa0/NHNpHLxCZGFIA tQ0Gp47VRmTPkWJ7lB505w0XioNs1H/1K1RSp++7+t1SNkBlobQpU3RlZmFuIEts YWFzIDxza0Bncm91bmR6ZXJvLXNlY3VyaXR5LmNvbT6IVwQTEQIAFwUCQVfjjQUL BwoDBAMVAwIDFgIBAheAAAoJEEvPMJZpkoy4AnYAmwTot1PMUty1YoCuMVg6cpr7 HKy1AJ98jyzD365YkIQAEiihXlQJ4zrxBLkCDQRBV+OvEAgAiu75prsTQZdNijtY eMQhl4tEL8qi8JOFluYGnvPYjDzU0PY9E4mNx/w2BgYcM3lTVzSmaiLEJ1AzeOHn w+pLDWsorRZuVI9q3+ExW3s2yFX4ppdHAVBMuYsQyVJRkbobCkcwTbUYXr23pKzh D8WRAJ991k2lNcQHxMgixAN+55XBFLhwLB0Yz7XmhFYLid5dLxdPllLIV3ZHDeY0 SEqMSpw96+gV0QpX7YH9U2VBr3Wz7Ss6qNZkcgHQw1xmk6Yy24QnT4a9oZD06Yjr cCocXnyI/YLW1wXo/6Hh44UH3b9mKUX6eh8ybn7QCnZDG7AdxbglLiPTkdcx0YoT NANZBwADBwf8CrjVKiXSzyhUsdH1es1KQCZ/zH6PvPzdxqYuGuVVMzgaJeeOMS2G 4rLfw2ILahAS0fjng6zX2c1ndPVJ6oAq3IygWsqJH6Uh23NmKTlyx3KtSgyW7YsB Rn/4wobuojArTHTl+X3U4JZTUEb9E4osB9bFjdsgXcxNSwXghQMh1x5eS5/fcjLd tACNq0x2/zh8zTJFHK+oNCLY2+iBjTUn7K03rEhQo6HqbPYwyc3LUCwBuFHFDVWp bZqa4knO0H5BBmbiI09kaVPOs0qRLXCAf1oy9PxK5ZBJ4WfQAnMAU+TuNrTuW2SU NMh92TCELdDpl/pMDbbBGeJdMvXZmY99HIhGBBgRAgAGBQJBV+OvAAoJEEvPMJZp koy4p1QAoIaYw3VxA0/mixUsMO4R13sXIL/pAJ9zodR+A9+bLqCRlVusG8JhItv1 Ow== =E0o1 -----END PGP PUBLIC KEY BLOCK----- Diese E-Mail kann vertrauliche Informationen enthalten. Wenn Sie nicht der richtige Adressat sind oder diese E-Mail irrtümlich erhalten haben, informieren Sie bitte sofort den Absender und vernichten Sie diese E-Mail. Das unerlaubte Kopieren sowie die unbefugte Weitergabe dieser E-Mail oder von Teilen dieser E-Mail ist nicht gestattet. This E-mail might contain confidential information. If you are not the right addressee or you have recived this Mail in error, please inform the Sender as soon as possible and delete this E-Mail immediately. You are not allowed to make any copies or relay this E-Mail. _______________________________________________ Full-Disclosure - We believe in it. Charter: http://lists.grok.org.uk/full-disclosure-charter.html Hosted and sponsored by Secunia - http://secunia.com/Is this supposed to be like some 'My first attempt at scripting? Please do not offer scripts like this as some people might believe it is useful, or even secure. The same people that will run this in /tmp with . in their path. Please note that this entire script can ALL be done in 1, count them 1, awk command. (sed as well, but not worth it). WTF is this? lIP=`ifconfig|grep -1 eth0|grep inet|sed 's/inet addr://'|awk '{print $1}'` If you are going to ATTEMPT to do something, at least use documented options. It's ``grep -A1'' not ``grep -1''. Then a pipe into sed THEN into awk? lIP=`/sbin/ifconfig | awk '/^eth0/{getline; sub(".*:","",$2); print $2}'` lIP=`/sbin/ifconfig | sed -ne '/^eth0/{n;s/^.*addr:\([^ \x09]*\).*/\1/;p}'` cat /var/log/messages |grep "Failed password" >$fail cat /var/log/messages |grep "Illegal user" >$fail2 cat /var/log/messages |grep "Invalid user" >$fail3 cat /var/log/messages |grep "Failed keyboard" >$fail4 Really? Really? yeah, /var/log/messages only has to be read ONE time and the other files can be written to. Which brings me to another point. Your use of static temp files in the current working directory is just... my god. We will just assume that 99% of all users do not use noclobber. You do know the implemencations of this, right? if [ "` cat $fail |grep "Failed password" |awk '{ print $15 }'`" == "" ]; then cat $fail |grep "Failed password" |awk '{ print $11 }' >ips1 fi if [ "` cat $fail2 |grep "Illegal user" |awk '{ print $14 }'`" == "" ]; then cat $fail2 |grep "Illegal user" |awk '{ print $10 }' >ips2 fi if [ "` cat $fail3 |grep "Invalid user" |awk '{ print $14 }'`" == "" ]; then cat $fail3 |grep "Invalid user" |awk '{ print $10 }' >ips3 fi if [ "` cat $fail4 |grep "Failed keyboard" |awk '{ print $17 }'`" == "" ]; then cat $fail4 |grep "Failed keyboard" |awk '{ print $13 }' >ips4 fi Ughh, reading those files enough? That makes no sense anyways, and yet again we are clobbering static TEMPORARY files in the current working directory. echo "~ sorting out ip by ip" for line in `cat ips1` # |read line do echo $line| grep '^[^.][^.]*\.[^.][^.]*\.[^.][^.]*\.[^.][^.]*$' >>ip.$line done for line in `cat ips2` # |read line do echo $line| grep '^[^.][^.]*\.[^.][^.]*\.[^.][^.]*\.[^.][^.]*$' >>ip.$line done for line in `cat ips3` # |read line do echo $line| grep '^[^.][^.]*\.[^.][^.]*\.[^.][^.]*\.[^.][^.]*$' >>ip.$line done for line in `cat ips4` # |read line do echo $line| grep '^[^.][^.]*\.[^.][^.]*\.[^.][^.]*\.[^.][^.]*$' >>ip.$line done See above. Not even going to comment on that again, let alone the pattern match. Will throw something at that in a minute. ls -la ip.*|awk '{ print $9 }' > ip.lst That just makes no sense, yet again. Here is where you would use -1, but with ls(documented and valid switch unlike in grep). for line in `cat ip.lst` do if [ `wc -l $line |awk '{ print $1 }'` = '1' ]; then # echo "" # echo "not enough failed logins, probably no attack from: $line" echo -n "*" else if [ `wc -l $line |awk '{ print $1 }'` = '2' ]; then # echo "" # echo "not enough failed logins, probably no attack from: $line" echo -n "*" else if [ `wc -l $line |awk '{ print $1 }'` = '3' ]; then # echo "" # echo "not enough failed logins, probably no attack from: $line" echo -n "*" else if [ `wc -l $line |awk '{ print $1 }'` = '4' ]; then # echo "" # echo "not enough failed logins, probably no attack from: $line" echo -n "*" else # generate list of the ip's to be blocked # echo "* IP: $line will be blocked!" echo -n "." echo $line >>$blocklist i=1; fi fi fi fi done You should have just done this way differently in the first place. And Yippy! Another static temp file. $blocklist can be fun. This time no clobbering so its even easier. if [ $i != 0 ]; then # edit blocklist (sometimes needs to be commented out or edited) cat $blocklist |sed 's/ip.::ffff://' >g && mv g $blocklist # cleanup rm -f ip.* ips1 ips2 ips3 ips4 ip.lst $fail $fail2 $fail3 $fail4 for host in `cat $blocklist` do if ((${#host}>6)) && ((${#host}<16)) then blk="`echo $host| grep '^[^.][^.]*\.[^.][^.]*\.[^.][^.]*\.[^.][^.]*$'`" if [[ "$blk" != "$lIP" && "$blk" != "" ]]; then echo " blocking IP: $blk" >> $log echo "host: $host blk: $blk" $fw -A INPUT -s $blk -j REJECT fi fi done cp $blocklist saved.blocklist rm -f $blocklist # left this in, in case you may not want to run this in background. # # echo "~ do you want to clean those entries from /var/log/messages ?" # read -e answer # if [ "$answer" == "y" ]; # then echo "+ cleaning system logs.." cat /var/log/messages |grep -v "llegal user" |grep -v "ailed password" |grep -v "nvalid user"|grep -v "ailed keyboard" >m echo "+ creating backup of old logfile.." cp /var/log/messages msg.copy echo "+ replacing logfile.." cat m > /var/log/messages rm -f m # fi else echo "no attackers found." fi echo "finished." Ohh, we are almost done! I liked symlinking m to /dev/urandom. It made me feel good about myself. grep | grep | grep | grep | grep | tee | grep | grep | cat | grep > /dev/stdout What else do we have here? $ export blocklist=blocklist fw=echo log=log $ echo 0.0.0.0/0 >> $blocklist $ for host in `cat $blocklist`do if ((${#host}>6)) && ((${#host}<16)) then blk="`echo $host| grep '^[^.][^.]*\.[^.][^.]*\.[^.][^.]*\.[^.][^.]*$'`" if [[ "$blk" != "$lIP" && "$blk" != "" ]]; then echo " blocking IP: $blk" >> $log echo "host: $host blk: $blk" $fw -A INPUT -s $blk -j REJECT fi fi donehost: 0.0.0.0/0 blk: 0.0.0.0/0 -A INPUT -s 0.0.0.0/0 -j REJECT $ cat log blocking IP: 0.0.0.0/0 :( Your not blocking lIP did not matter, like it would anyways. You made me sad. Notice your pattern match just LOVED accepting 0.0.0.0/0. Hints: bash [ -e "$file" ] [ -h "$file" ] [ -n "$variable" ] set -o case/esac IFS=.; set -- $host ${VAR//} bc mktemp _______________________________________________ Full-Disclosure - We believe in it. Charter: http://lists.grok.org.uk/full-disclosure-charter.html Hosted and sponsored by Secunia - http://secunia.com/
_______________________________________________ Full-Disclosure - We believe in it. Charter: http://lists.grok.org.uk/full-disclosure-charter.html Hosted and sponsored by Secunia - http://secunia.com/
Current thread:
- reduction of brute force login attempts via SSH through iptables --hashlimit Jay Libove (Mar 01)
- Re: reduction of brute force login attempts via SSH through iptables --hashlimit GroundZero Security (Mar 01)
- Re: reduction of brute force login attempts via SSH through iptables --hashlimit Giancarlo Razzolini (Mar 01)
- Re: reduction of brute force login attempts via SSH through iptables --hashlimit nocfed (Mar 02)
- Re: reduction of brute force login attempts via SSHthrough iptables --hashlimit GroundZero Security (Mar 02)
- Re: reduction of brute force login attempts via SSHthrough iptables --hashlimit Gary Leons (Mar 02)
- Re: reduction of brute force login attempts via SSHthrough iptables --hashlimit GroundZero Security (Mar 02)
- Re: reduction of brute force login attempts via SSHthrough iptables --hashlimit Benjamin Bennett (Mar 02)
- Re: reduction of brute force login attempts via SSHthrough iptables --hashlimit Gary Leons (Mar 02)
- Re: reduction of brute force login attempts via SSHthrough iptables --hashlimit GroundZero Security (Mar 02)
- Re: reduction of brute force login attempts via SSH through iptables --hashlimit GroundZero Security (Mar 01)
- Re: reduction of brute force login attempts viaSSHthrough iptables --hashlimit Dave Korn (Mar 03)
- Re: Re: reduction of brute force login attemptsviaSSHthrough iptables --hashlimit GroundZero Security (Mar 03)