Emulating various devices with Pi Zero - how to do it?

If you want to emulate a network adapter, keyboard, drive, and everything else with Pi Zero, all at the same time, you can do it all. LibComposite comes to the rescue, however, in this case you need to remember that there is no solution under Windows, the method is suitable only for Linux or Mac OS X. A detailed description of the user’s actions to achieve the result described in the header is in the sequel ( source ).

Step 0 - configure the SD card

Download and install the latest Raspbian Jessie distribution on a suitable SD card (should be capacious enough), and increase the root partition.

Step 1 - The Kernel

You need to use Kernel 4.4, which does not come by default with the Rasbian distribution. But updating is easy enough, you just need to execute this console command:

sudo BRANCH = next rpi-update

After that, do this:

echo "dtoverlay = dwc2" | sudo tee -a /boot/config.txt
echo "dwc2" | sudo tee -a / etc / modules

Finally, activate the libcomposite driver:

sudo echo “libcomposite” | sudo tee -a / etc / modules

Step 2 - configure devices

Now you need to decide which device to emulate - a network card, keyboard, or all of this together?

We configure this using ConfigFS, the virtual file system in / sys /. It is automatically mounted at the start of the "raspberry", so in the future you can work with it.
There is a great example for a device called USBArmory, an example here . Everything else will be shown on its basis.

We create a configuration script.

You will have to run it every time you start the device. Create the isticktoit_usb in / usr / bin / file using your favorite text editor. We write this:
sudo touch / usr / bin / isticktoit_usb #create the file
sudo chmod + x / usr / bin / isticktoit_usb #make it executable
sudo nano / usr / bin / isticktoit_usb #edit the file

After that, the script must be run automatically at startup. For best performance, you can create a systemd unit file, but for now, let's get around rc.local. (This is part of the old sysvinit system, but it runs on raspberry pi by default).

Open the root /etc/rc.local and add a line (before !!!) a line containing the word "exit":

sudo nano /etc/rc.local
/etc/rc.local.../usr
/ bin / isticktoit_usb # libcomposite configuration
exit

Creating a gadget

This is a global configuration, so it doesn't matter how many USB gadgets you would like to use. You can change the serial number, manufacturer and product name in this block.

/ usr / bin / isticktoit_usbcd / sys / kernel / config / usb_gadget /
mkdir -p isticktoit
cd isticktoit
echo 0x1d6b> idVendor # Linux Foundation
echo 0x0104> idProduct # Multifunction Composite Gadget
echo 0x0100> bcdDbc 0d0b
USB0cho 0x0100.0 bxd0e0b USB0cho 0x000 0x USB 0x0b0d0b0d0b0d0e0b
mkdir -p strings / 0x409
echo "fedcba9876543210"> strings / 0x409 / serialnumber
echo "Tobias Girstmair"> strings / 0x409 / manufacturer
echo "iSticktoit.net USB Device"> strings / 0x409 / product
mkdir -p configs / c.1 / strings / 0x409
echo "Config 1: ECM network"> configs / c.1 / strings / 0x409 / configuration
echo 250> configs / c.1 / MaxPower
# Add functions here
# see gadget configurations below
# End functions
ls / sys / class / udc> UDC

Ethernet adapter

First of all, let's add this to our configuration file:

sudo nano / usr / bin / isticktoit_usb
/ usr / bin / isticktoit_usb # Add functions here
mkdir -p functions / ecm .usb0
# first byte of address must be even
HOST = “48: 6f: 73: 74: 50: 43” # “HostPC”
SELF = “42: 61: 64: 55: 53: 42” # “BadUSB”
echo $ HOST> functions / ecm.usb0 / host_addr
echo $ SELF> functions / ecm.usb0 / dev_addr
ln -s functions / ecm.usb0 configs / c.1 /
# End functions
ls / sys / class / udc> UDC
#put this at the very end of the file:
ifconfig $ N 10.0.0.1 netmask 255.255.255.252 up
route add -net default gw 10.0.0.2

We save and exit, then go to the host PC:
If there are problems with automatic connection, disconnect and do this:

dmesg | grep cdc_ether
[13890.668557] cdc_ether 1-1: 1.2 eth0: register 'cdc_ether' at usb-0000: 00: 14.0-1, CDC Ethernet Device, 48: 6f: 73: 74: 50: 43
[13890.674117] usbcore: registered new interface driver cdc_ether
[13890.687619] cdc_ether 1-1: 1.2 enp0s20u1i2: renamed from eth0 You can

rename the adapter even after, while let's call it enp0s20u1i2

sudo ifconfig enp0s20u1i2 10.0.0.2 netmask 255.255.255.252 up

and connect via ssh to PI:

ssh 10.0.0.1 -l pi

Keyboard, mouse, joystick (HID)

sudo nano / usr / bin / isticktoit_usb
/ usr / bin / isticktoit_usb # Add functions here
mkdir -p functions / hid.usb0
echo 1> functions / hid.0 / protocol
echo 1> functions / hid.0 / subclass
echo 8> functions / hid.0 / report_length
echo - ne \\ x05 \\ x01 \\ x09 \\ x06 \\ xa1 \\ x01 \\ x05 \\ x07 \\ x19 \\ xe0 \\ x29 \\ xe7 \\ x15 \\ x00 \\ x25 \\ x01 \ \ x75 \\ x01 \\ x95 \\ x08 \\ x81 \\ x02 \\ x95 \\ x01 \\ x75 \\ x08 \\ x81 \\ x03 \\ x95 \\ x05 \\ x75 \\ x01 \\ x05 \\ x08 \\ x19 \\ x01 \\ x29 \\ x05 \\ x91 \\ x02 \\ x95 \\ x01 \\ x75 \\ x03 \\ x91 \\ x03 \\ x95 \\ x06 \\ x75 \\ x08 \\ x15 \\ x00 \\ x25 \\ x65 \\ x05 \\ x07 \\ x19 \\ x00 \\ x29 \\ x65 \\ x81 \\ x00 \\ xc0> functions / hid.0 / report_desc
ln - s functions / hid.usb0 configs / c.1 /
# End functions

Here is the easiest way to send keystrokes to the device file:
echo "\ 0 \ 0 \ x4 \ 0 \ 0 \ 0 \ 0 \ 0"> / dev / hidg0 #press the A-button
echo "\ 0 \ 0 \ 0 \ 0 \ 0 \ 0 \ 0 \ 0"> / dev / hidg0 #release all keys

But this is not the most practical way, so you should use this example and download it to your PC. Then we extract it to the “raspberry” SD card and start it.

On Pi:
cd PATH_TO_HARDPASS_REPO
make #compile the program
echo -n "hello world!" | sudo ./scan / dev / hidg0 1 2

Here ‚1 'means the American keyboard layout, and" 2 "- German-Austrian. the second number is needed to enter characters that are not on your keyboard (2 = Linux, 3 = Windows (although there are no drivers for this OS)).

Storage device

This is harder to do. You can use only a disk image file. The example creates a very small disk image file to save the ethernet host configuration.
First, let's make a disk. This is a fairly lengthy process, the tutorial is here .
Then again we go to the configuration:

sudo nano / usr / bin / isticktoit_usb
/ usr / bin / isticktoit_usb # Add functions here
FILE = / home / pi / usbdisk.img
mkdir -p $ {FILE / img / d}
mount -o loop, ro, offset = 1048576 -t ext4 $ FILE $ {FILE / img / d}
mkdir -p functions / mass_storage.usb0
echo 1> functions / mass_storage.usb0 / stall
echo 0> functions / mass_storage.usb0 / lun.0 / cdrom
echo 0> functions / mass_storage.usb0 / lun.0 / ro
echo 0> functions / mass_storage.usb0 / lun.0 / nofua
echo $ FILE> functions / mass_storage.usb0 / lun.0 / file
ln -s functions / mass_storage.usb0 configs / c.1 /
# End functions

After that there should be a removable disk in FAT32 format is available, which will be shown after the next Pi connection to the main PC. To access files stored on the Pi, you can run unmount and then reconnect it somewhere else.

What else?

In total there are about 20 USB gadgets that can be emulated by the Linux kernel. Here is more information about this !

Useful links:
Tutorial by gbaman
libcomposite in the Kernel documentation
-> hardpass - PiZero project (Keyboad emulation) <- USBArmory Wiki Page