What is NexMon?

NexMon is a firmware patching framework initially built for the BCM4339 WiFi firmware of Nexus 5 smartphones. However, this repository contains firmware patches for the BCM43438 WiFi chip used in the Raspberry Pi 3. It's main intention was to enable monitor mode and frame injection, which now works quite well. Nevertheless, we have also published many example patches that allow you to dive into firmware reverse engineering and firmware patching. The ability to write firmware patches in C makes it easy to use, especially for beginners.

News

• Have a look in our new Repoistory: https://github.com/seemoo-lab/nexmon. Future development will happend there.
• We moved to GitHub!

WARNING

Our software may damage your hardware and may void your hardware’s warranty! You use our tools at your own risk and responsibility! If you don't like these terms, don't use nexmon!

What this Repo contains

• A bootable image (Raspbian 8) for the micro SD card (8GB) of your Raspberry Pi 3, including a patched version of airgrack-ng:
  • see our latest release, the .tar.gz contains the dd image
• Everything needed to build the patches by yourself

Steps needed to run the prepared SD card image on your Raspberry Pi 3

• unpack the dd image
• copy the image to your SD card, e.g.: dd if=nexmon_rpi_12-10-2016.dd of=/dev/mmcblk0 bs=1M note: the sd card device (in this example mmcblk0) may change depending on your setup
• Login as root with the password nexmon
• Change the keymap if necessary: dpkg-reconfigure keyboard-configuration and shutdown -r now / invoke-rc.d keyboard-setup start to reload the keymap.

Monitor Mode

• insmod /root/brcmfmac.ko
• ifconfig wlan0 up
• thats it, try using tcpdump: tcpdump -i wlan0 -s0
• or airodump-ng: airodump-ng wlan0

Original firmware and driver

• Optional: remove the monitor mode driver rmmod brcmfmac
• cp /root/brcmfmac43430-sdio.orig.bin /lib/firmware/brcm/brcmfmac43430-sdio.bin
• use modprobe brcmfmac to load the unmodified driver and firmware

Steps to create your own firmware patches

Using a x86 based computer

• clone our repository
• set the environment in the repository folder: source setup_env.sh
• for the monitor mode patch: cd firmware_patching/nexmon/
• make
• copy the brcmfmac/brcmfmac.ko to the /root/ directory of your Raspberry Pi
• copy the brcmfmac43430-sdio.bin to /lib/firmware/brcm/ directory of your Raspberry Pi

Using your Raspberry Pi

• clone our repository
• upgrade your raspbian installation: apt-get update && apt-get upgrade
• sudo apt install raspberrypi-kernel-headers libgmp3-dev gawk
• remove wpa_supplicant for better control over the WiFi interface: apt-get remove wpasupplicant
• set the environment in the repository folder: source setup_env.sh
• for the monitor mode patch: cd firmware_patching/nexmon/
• make
• unload the original driver module: rmmod brcmfmac
• load the modified driver module: insmod brcmfmac/brcmfmac.ko
• copy the brcmfmac43430-sdio.bin to /lib/firmware/brcm/ directory of your Raspberry Pi (make a copy of the original file beforehand)
• set the interface up: ifconfig wlan0 up

Caveats

Read our papers

Feel free to read and reference our papers on the development of this project

• M. Schulz, D. Wegemer and M. Hollick. [NexMon: A Cookbook for Firmware Modifications on Smartphones to Enable Monitor Mode] (http://arxiv.org/abs/1601.07077), CoRR, vol. abs/1601.07077, December 2015. bibtex
• M. Schulz, D. Wegemer, M. Hollick. DEMO: Using NexMon, the C-based WiFi firmware modification framework, Proceedings of the 9th ACM Conference on Security and Privacy in Wireless and Mobile Networks, WiSec 2016, July 2016.

Contact

• Matthias Schulz [email protected]
• Daniel Wegemer [email protected]