Switch OS Reverse Engeneering

It is really hard to get informations about the proprietary OS that runs on many switches. The vendors don´t give away many informations how it actually works under the hood. The old model of security by obscurity is still applied here. I saw on the 25C3 conference in Berlin the “Cisco IOS attack and defense” talk from Felix FX Lindner that changed my mindset about code quality inside of switch OS completly. Felix FX Linder reverse engeneered the IOS code and showed very detailed how IOS works and wich attack vectors can be leveraged to get control over an IOS based device. Felix is one of the most talented persons in the community when it comes to reverse engeneering and I am very thankful for all the time and effort that he has spend on this project. The talk is about 1 hour and covers a really deep dive into Ciscos IOS code. I learned more about how IOS works from this talk than on all presantations that I have ever seen from Cisco.

This talk is from 2008 and was the first of a series of switch OS reverse engeneering projects from FX. The next target was the Huawei VRP OS. The results FX presented on DEFCON 2012. Huawei had a joint a venture with HP and I it looks like that most of the results are also apply for the H3C devices from HP. The myth that Huawei has copied the IOS code was disproved by FX. He found out that the Huawei VRP OS is based on VxWorks. At the end of the talk his devastating summary is “90´s style bugs, 90´s style exploration, 0 operating system hardening … no security advisories..”.

Beyond the physical switches FX also reverse engeneered the Cisco Nexus 1000v virtual switch. In the talk “Cisco in the sky with diamonds” FX presented the results of that research at the Signit 2013 conference.The NX-OS based Nexus 1000v is based on a Montavista Linux that runs a 2.6.10 Kernel. FX und Greg found a jailbreak wich they show in the talk and mention that the same jailbreak also works on the physical Nexus devices.

This shows the level of security that is embedded inside of the switches that FX has investigated is very poor. I think very different since I am aware of the resaerch of FX when it comes to protect a switch from getting owned by a hack. It also explains a lot of the bugs that I have expierenced in the past. Hopefully FX and Greg will continue their excellent work in the future.




About Dominik

Network problem solver
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