Few days ago, I bought a USB Wi-Fi adapter to learn about pentesting. The goal was using this adapter to connect a virtual Kali Linux distribution in VirtualBox to Wi-Fi network through USB.

After some hesitations, I picked up a cheap enough model which uses a RT18812AU chip. An important factor to choose this chip is that it is dual-band. This was the first time I’m dealing with such material. Of course, there was no such thing as plug-and-play. So I had to manually install the driver.

The adapter comes with a “quick installation guide” written in gibberish English.¹ So, not very promising. I decided to insert directly the provided CD and see if I can do something. There were three directories for respectively OSX, Windows and Linux. I extracted the Linux directory and ran the install.sh without too much hesitation. It failed. No worry, such thing happens, I read the install.sh, again gibberish English comments²… I went to the driver directory (rtl88x2BU_WiFi_linux_v5.3.1_27678.20180430_COEX20180427-5959) to see if I can do something and got the marvelous idea to feed the driver name to Google to see if I can get an up-to-date version. I found one,

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git clone https://github.com/morrownr/88x2bu.git

and followed the instructions. It compiles! The bad news is the plugged adapter doesn’t have any sign of life. Weird! After all kinds of attempts and reboots, I naively ran a new command

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lsusb

which reveals that the chip was actually a RT18812AU. I double-checked the chip model and realized that it’s right, and thought I bought a BU but finally picked a AU. So… why they ever put an outdate RT18812BU in the CD? Mystery. Again, I searched a driver for this chip, and found this one:

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git clone https://github.com/gnab/rtl8812au

… followed the instructions, and bingo! The adapter LED started blinking. I expected that it would work painless in VirtualBox… was wrong. In the Kali Linux USB settings, the button “add new USB filter” didn’t display my USB devices, contrary to what I expected. After heavy surfing on the Internet, I found this relevant thread. Ah, I wasn’t in vboxusers group:

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groups

So, I had to add it.

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sudo usermod -a -G vboxusers firmart

Logged out. Log back. And finally:

Ventre Saint-Antoine!, would say a medieval Frenchman.

Conclusion.

• If you are on Linux, do not even bother to insert the CD (and to read the “quick installation guide”).
• Search right away on Google <chip> github and you would find an enhanced driver with a useful README.
• lsusb is actually useful to make sure the USB device is there and to double-check the chip model.

This tale³ would not be written without the help of ~/.zsh_history and my browser history.