Steve August 20, 2020
exotic-device-gets-linux-support-via-wireshark-and-rust

What can you do if you have a nice piece of hardware that kinda works out of the box, but doesn’t have support for your operating system to get the full functionality out of it? [Harry Gill] found himself in such a situation with a new all-in-one (AIO) water cooling system. It didn’t technically require any operating system interaction to perform its main task, but things like settings adjustments or reading back statistics were only possible with Windows. He thought it would be nice to have those features in Linux as well, and as the communication is done via USB, figured the obvious solution is to reverse engineer the protocol and simply replicate it.

His first step was to set up a dual boot system (his attempts at running the software in a VM didn’t go very well) which allowed him to capture the USB traffic with Wireshark and USBPcap. Then it would simply be a matter of analyzing the captures and writing some Linux software to make sense of the data. The go-to library for USB tasks would be libusb, which has bindings for plenty of languages, but as an avid Rust user, that choice was never really an issue anyway.

How to actually make use of the captured data was an entirely different story though, and without documentation or much help from the vendor, [Harry] resorted to good old trial and error to find out which byte does what. Eventually he succeeded and was able to get the additional features he wanted supported in Linux — check out the final code in the GitHub repository if you’re curious what this looks like in Rust.

Capturing the USB communication with Wireshark seems generally a great way to port unsupported features to Linux, as we’ve seen earlier with an RGB keyboard and the VGA frame grabber that inspired it. If you want to dig deeper into the subject, [Harry] listed a few resources regarding USB in general, but there’s plenty more to explore with reverse engineering USB.

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