Link：http://rootatnasro.wordpress.com/2014/01/11/how-i-saved-your-a-from-the-zynos-rom-0-attack-full-disclosure/
HOW I SAVED YOUR A** FROM THE ZYNOS (ROM-0) ATTACK !! ( FULL DISCLOSURE )

Hello everyone, I just wanted to discuss some vulnerability I found and exploited for GOODNESS .. just so that SCRIPT KIDIES won’t attack your home/business network .

Well, in Algeria the main ISP ( Algerie Telecom ) provide you with a router when you pay for an internet plan. So you can conclude that every subscriber is using that router . TD-W8951ND is one of them, I did some ip scanning and I found that every router is using ZYXEL embedded firmware.

Analysis :

Let’s download an update and take a look at it and try to find some vulnerabilities. ( http://www.tp-link.com/Resources/software/TD-W8951ND_V3.0_110729_FI.rar )

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The ras file is in LIF format !! …
Hmmm let’s put that file for Binwalk test for God’s sake ! ( check : http://code.google.com/p/binwalk/wiki/Installation for more informations on how to install it ).

This is what Binwalk told me about that file :
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You can clearly see and confirm that the router is using zynos firmware. We can also see that there is two blocks of LZMA compressed data … let’s extract them and have a look.
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The problem is that when I tried to decompress the two blocks I get an error : ” Compressed data is corrupt “Image

Hmm, first the “ras” file was in LIF format .. and now the lzma compress blocks are corrupted !!
I googled this and tried to find a solution for this, FOUND NOTHING . How am I going to solve this ??
One idea came in my mind .. “Strings” command and here is what I got :

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Aaaah ! so the blocks aren’t compressed with LZMA or anything ! and the whole “ras” firmware file is just big chunk of data in clear text.
Ok, let’s try and find some useful STRINGS …

After some time searching “I” didn’t find the useful thing that will help us find vulnerabilities on the firmware !!

I didn’t give up …
I just was thinking and questioning :

Me: What do you want from this firmware file !
Me: I want to find remote vulnerabilities that will help me extract the “admin” password.
Me: Does the web interface let you save the current configuration ?
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Me: yes !!
Me: Is the page password protected ?
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Me: No !!! I tired to access that page on a different IP and it didn’t require a passowrd !
Ok, enough questions haha ..

Now, when I activated TamperData and clicked “ROMFILE SAVE”  I’ve found out that the rom-0 file is located on “IP/rom-0″ and the directory isn’t password protected or anything.

So we are able to download the configuration file which contains the “admin” password. I took a look at rom-0 file and couldn’t figure out how to reverse-engineer it, and when you don’t know something it’s not a shame to ask for help .. and that’s what I did !
I contacted “Craig” from devttys0.com, he is an expect when it comes to hacking embdded devices . He’s a great guy and he replied to my email and pointed me to http://50.57.229.26/zynos.php which is a free rom-0 file decompressor .

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When you upload and submit the rom-0 file there, the php page replies back with the configuration in clear text ( INCLUDING THE PASSWORD ) .

So what i need to do now is to automate the process of :

Download rom-0 file.
Upload it to http://50.57.229.26/zynos.php
get the repy back and extract the admin password from it.
loop this process to a range of ip addresses.
And that’s exactly what I did, I opened an OLD OLD poc python script of mine that accessed routers via telnet using the default passwords. So what I just need to do now is to add some functionality to it.

Well I thought about  this, and I’m posting this script online ONLY FOR EDUCATIONAL PURPOSES.

You can find the scripts here : https://github.com/MrNasro/zynos-attacker/

Demo :

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PS : I OWN ALL THE IP RANGE I WAS SCANNING ” FOR SURE ;) “

Prevention :

Now ! how do you prevent attackers from downloading your rom-0 configuration file and manipulating your router ? This is pretty simple if you think about it ..
You just have to forward port 80 on the router to and inused IP address on your network :
forward

THATS ALL, or if you want to play a little with attackers that are using scripts too .. just forward port 80 to you local http server and put a LARGE file in the root directory and name it rom-0 .. just let them download like 1GB rom-0 file haha haha .. I have also automated the process of port forwarding and I’m running the scripts daily just to prevent hackers from attacking weak users …

In the next post I’ll demonstrate how would a malicious hacker exploit this to hack TONS of networks and get a meterpreter/reverse_shell on every PC on the target network ..

Hope you enjoyed this analysis, if you have anything to add or any questions to ask don’t hesitate to contact me ! BE THEIR HERO, HAPPY HACKING ;)

[培训]《安卓高级研修班(网课)》月薪三万计划，掌握调试、分析还原ollvm、vmp的方法，定制art虚拟机自动化脱壳的方法