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Great Scott Gadgets

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Reverse Engineering Black Box Systems with GreatFET, Troopers 2018

In this presentation at Troopers 2018, Kate Temkin and Dominic Spill used GreatFET One and the Facedancer software framework to demonstrate techniques for reverse engineering embedded USB hosts.

It is often fairly simple to set up an environment for reversing a USB device; you just plug it into a host that you control. Then you can manipulate software on the host to test or monitor USB communications between the host and device. Even if the host operating system doesn’t provide a way for you to monitor USB (hint: it probably does), you can run it inside a virtual machine that runs on top of Linux and use Linux’s usbmon capability.

But how do you sniff USB if the USB host is an embedded platform that you don’t control? What if it is a game console or a photocopier with software that you can’t run in a virtual machine? Kate and Dominic show how you can use GreatFET One and a laptop to proxy USB between a device and a host without controlling software on either the device or the host. With the USBProxy solution they implemented in Facedancer, it is possible not only to monitor USB communication but also to modify USB data in transit.

Additionally they demonstrate how the Facedancer software for GreatFET can be used to emulate a USB device, allowing them to reverse engineer “black box” USB hosts and test them for vulnerabilities.

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Making USB Accessible, Teardown 2019

On Sunday, Kate Temkin and Mikaela Szekely presented Making USB Accessible: Developing Ultra-low-cost, Open USB Tools at Teardown 2019 in Portland. In this well-received talk, they debuted ViewSB, a USB analyzer that supports various capture backends including GreatFET, OpenVizsla, and usbmon.

In the days leading up to the talk, Kate went on a tear, developing ViewSB to complement the hardware solutions for USB capture that she and Mikaela had been working on. I asked, “Why do we need ViewSB when we already have tools such as PulseView and Wireshark?”

Her answer was that the existing open source software tools for USB analysis don’t present data in a way that is useful enough for USB developers. I recalled my past confusion about USB nomenclature and how the most essential thing I learned from Kate’s training class at last year had been an understanding of the differences between USB packets, transactions, and transfers. Thinking back to the tools we used in that class, I realized that she was right that a new tool was needed. In fact, the limitations of the existing tools were probably largely responsible for my confusion!

As you can see in this video, ViewSB presents low level USB packet data in a visual format that groups packets together into transactions, something that I had previously seen only in software for proprietary USB analyzers. It makes USB much easier to understand. I wholeheartedly agree with Mikaela and Kate that their work makes USB accessible!

Code used in the presentation can be found in the usb-tools organization on GitHub.

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GreatFET on Hak5

I recently sat down with Darren Kitchen to record a couple Hak5 episodes. First we introduced GreatFET One to his viewers and demonstrated using its Facedancer capability to emulate a USB device. Then we did some infrared hacking with Gladiolus, a prototype GreatFET neighbor we plan to release later this year. Thanks for having me on the show, Darren!

Introducing the GreatFET One Hacking Infrared with Mike Ossmann and the GreatFET One

Defeating Spread Spectrum Communication with Software Defined Radio, ToorCon 2013

Fortunately in this video you can't hear the jackhammers at work in the hotel lobby while I gave this presentation at the ToorCon San Diego seminars in October, 2013. Apart from having to talk over the construction noise, it was great to share SDR techniques that can be used to point out flaws in security claims made about spread spectrum communication technologies.

One of the things I showed in the talk was how Direct Sequence Spread Spectrum (DSSS) communications can be reverse engineered. I used SPOT Connect, a device operating on the GlobalStar satellite network as an example. A couple years later, Colby Moore did a more complete job of showing how the GlobalStar system can be attacked.

If you aren't familiar with the Pastor Manul Laphroaig, mentioned at the beginning of this talk, check out our PoC||GTFO mirror.

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Rapid Radio Reversing, ToorCon 2015

In this video of my presentation at ToorCon 2015, I demonstrate how helpful it can be to use a combination of both SDR and non-SDR tools for reverse engineering wireless systems. I use both HackRF One and YARD Stick One to reverse engineer a wireless cabinet lock.

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code from the presentation