Kali WSL2 - Custom Kernel and rtl8812au driver installation

📌 This tutorial demonstrates how to build and use a custom kernel for WSL2 distros.

Setup Kali WSL2

• Disable password prompt when using sudo command :

echo "kevin ALL=(ALL) NOPASSWD: ALL" | sudo tee -a /etc/sudoers.d/010_kevin-nopasswd > /dev/null

• Update the system :

sudo apt update && sudo apt upgrade

• Install useful packages :

sudo apt install bash-completion build-essential gcc g++ avr-libc avrdude default-jre default-jdk git clang make nano xz-utils usbip wget
source .bashrc

• Install Kali packages :

sudo apt install kali-linux-large

• Setup remote access :

sudo apt install kali-win-kex
kex --esm -s

Build and install a custom WSL2 kernel

• Install required packages :

sudo apt install flex bison libssl-dev libelf-dev git dwarves bc

• Download official WSL2 kernel and prepare the installation :

wget https://github.com/microsoft/WSL2-Linux-Kernel/archive/refs/tags/linux-msft-wsl-$(uname -r | cut -d- -f 1).tar.gz
tar -xvf linux-msft-wsl-$(uname -r | cut -d- -f 1).tar.gz
cd WSL2-Linux-Kernel-linux-msft-wsl-$(uname -r | cut -d- -f 1)
cat /proc/config.gz | gunzip > .config
make prepare modules_prepare -j $(expr $(nproc) - 1)

• Open the kernel's configuration menu to add cfg80211 wireless modules (802.11 protocols) :

make menuconfig -j $(expr $(nproc) - 1)

• Build and install modules :

make modules -j $(expr $(nproc) - 1)
sudo make modules_install
make -j $(expr $(nproc) - 1)
sudo make install

Note : Kernel headers are going to be installed in the /lib/modules/ directory.

• Copy the built kernel image to C:\Users\<User>\ :

cp vmlinux /mnt/c/Users/Kevin/

• Create a .wslconfig file to declare the new kernel :

nano /mnt/c/Users/Kevin/.wslconfig

• Paste the following content into this file :

[wsl2]
kernel=C:\\Users\\Kevin\\vmlinux

• Switch to Powershell and shutdown running WSL2 distros :

wsl --shutdown

🚩 When a WSL2 distro will be rebooted, the default WSL2 kernel located in C:\Windows\System32\lxss\tools\kernel will be replaced by the newly built kernel.

Compile and load a kernel module

Note : This example illustrates how to build and load the rtl8812au module to the WSL2 kernel.

• Clone the aircrack-ng/rtl8812au Github repository :

git clone https://github.com/aircrack-ng/rtl8812au
cd rtl8812au

• Build the module with the new kernel headers :

sudo make

✅ This commands generates a .ko file which correspond to the built module.
⚠️ The headers must be installed in the /lib/modules/$(uname -r)/build directory.
You can check your WSL2 version by running uname -r.

Test : Enable cfg80211 and 88XXau.ko modules :

sudo modprobe cfg80211
sudo insmod 88XXau.ko
lsmod

⚠️ cfg80211 module must be loaded before 88XXau.ko.

• Install the module :

sudo mkdir -p /lib/modules/$(uname -r)/kernel/drivers/net/wireless
sudo make install

Note : Now, sudo modprobe 88XXau command will work.

• Enable the module :

sudo modprobe 88XXau

Load modules at boot time

• Add modules that need to be loaded at boot time to the /etc/modules-load.d/ directory :

echo "cfg80211" | sudo tee -a /etc/modules-load.d/cfg80211.conf
echo "88XXau" | sudo tee -a /etc/modules-load.d/88XXau.conf

⚠️ Don't add .ko extension to the module name.

Wi-Fi adapter connection using rtl8812au driver :

• Attach a USB device using usbip :

sudo usbip list --remote=<IP>
sudo usbip attach --remote=<IP> --busid=<BUS-ID>
ip a

• Install aircrack-ng packages :

sudo apt install aircrack-ng pciutils

• Set the adapter in monitor mode :

sudo airmon-ng
sudo ip link set wlan0 stop
sudo airmon-ng start wlan0

• Search WEP networks with airodump-ng :

sudo airodump-ng wlan0 --encrypt WEP

• Test wireless packet injection :

sudo aireplay-ng -9 -e [SSID] -a [BSSID] --ignore-negative-one wlan0

• Capture IVs and decode WEP key :

sudo besside-ng -c 11 -b 82:A9:40:96:BE:48 wlan0

• Launch aircrack-ng to crack WEP key :

sudo aircrack-ng wep.cap

• Disable monitor mode on wlan0 interface :

airmon-ng stop wlan0

• Detach USB device :

sudo usbip port
sudo usbip detach --port=

Create usbip scripts

Attach a USB device

• Create and edit a file called musb :

nano musb

• Add the following content to this file :

#!/bin/bash

if ! [ $(id -u) = 0 ]; then
   echo "The script need to be run as root." >&2
   exit 1
fi

echo "Enter the IP address of the foreign device :"
read ip

echo ""
usbip list -r $ip

echo "Enter the name of the shared USB device to import :"
read usb

echo ""
usbip attach -r $ip -b $usb

sleep 1
usbip port

• Add execution permissions to the file :

chmod +x musb

• Run the script :

sudo ./musb

Detach a USB device

• Create and edit a file called musb :

nano uusb

• Add the following content to this file :

#!/bin/bash

if ! [ $(id -u) = 0 ]; then
   echo "The script need to be run as root." >&2
   exit 1
fi

usbip port

echo ""
echo "Enter the USB device to detach :"
read usb

echo ""
usbip detach -p $usb

sleep 1
usbip port

• Add execution permissions to the file :

chmod +x uusb

• Run the script :

sudo ./uusb

References

• Microsoft Github Repository - WSL2-Linux-Kernel
• WSL2 /lib/modules Stack Exchange Discussion
• Github Gist - Custom WSL2 Kernel Build
• RTL8812AU Driver Installation On RPI
• Basic RTL8812AU Drive Configuration
• aircrack-ng Deauthentication Attack
• WEP Wi-Fi Network Cracking
• Windows aireplay-ng Packet Injection
• Wireless Capture On Windows
• NPCAP Developer Guide
• USB-IP For Windows
• WSL2 Setup Guide
• Kali Tools Guide