3.0 KiB
Save data from your BadUSB scripts directly to the Flipper's SD Card!
Inspired by this thread: https://forum.flipperzero.one/t/anyway-to-save-files-back-to-the-flipper-using-badusb/2372
Credit: Major credit to @LupusE for taking my original proof-of-concept, running with it, and making a proper example payload!
This proof of concept is for Windows-only.
BadUSB script that uses inline Powershell to enumerate which COM port the Flipper is connected to, and then use Powershell's serial module to interface with Flipper's CLI and write text data to a specified file in Flipper's SD Card. It will automatically detect when the Flipper has exited BadUSB mode before writing the data to the SD card.
What makes this method unique?
There are plenty of examples of using Ducky Script to exfiltrate data. Exfiltration by webhook/discord can be detected/blocked by IDS and firewall rules. Exfiltration by copying data to a USB flash drive (mass storage driver) can be thwarted by rules disallowing access to USB mass storage devices. The "Save to Flipper" POC makes use of Windows' COM ports and the Powershell serial module. This traffic is much more problematic to block, as many legitimate things can use the COM ports, and it is not affected by blocking access to mass storage devices. Further, you can tweak the device ID to further bypass any restrictions.
Limitations:
Using serial to interface to the Flipper's CLI in order to save a file is slow. This is not a huge problem for small amounts of text data, but could be problematic for a larger exfiltration.
There also appears to be some kind of buffer size limit that will cause the exfiltrated data to fail to save. This is being investigated.
Usage:
Attach Flipper to computer by USB cable and run the BadUSB script. When the Flipper shows 100% completion, hit Back enough times to get to the Flipper application list (otherwise it won't save the data) and wait a moment and then remove the Flipper.
Variables:
$d is the command who's output you want to exfiltrate to the Flipper's storage. Make sure to include |Out-String as the last part of the command.
$BHID and $BPID allow you to specify the Device ID parameters of your Flipper.
$SPATH is the location on the SD card to store your exfiltrated data. By default, it saves to /ext/apps_data/exfil_data
Example
This proof-of-concept stores the output of the Powershell Get-ComputerInfo
There are two payload examples included in the script. One will output to the Powershell console the state of the Flipper (BadUSB/NoFZ) to help you learn how to Back out of the BadUSB application and the timing. The other payload is without debugging and without a delay if the Flipper is simply disconnected.
Note about early disconnection
If the Flipper is disconnected from the host computer while it is receiving the exfiltrated data, the Flipper may remain stuck with it's serial CLI open, which will cause it to have an error when connecting it to qFlipper. Simply reboot the Flipper to get it working normally again.