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pelya / android-keyboard-gadget

Convert your Android device into USB keyboard/mouse, control your PC from your Android device remotely, including BIOS/bootloader.
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Convert your Android device into USB keyboard/mouse, control your PC from your Android device remotely, including BIOS/bootloader.

For newer Kernel versions (>= 3.19) the patch is not anymore required and can be replaced by ConfigFS (USB Gadget Tool).

Apps & tools using android-keyboard-gadget:

Installation

Nexus 7 2012 WiFi (Grouper)

Nexus 7 2013

LG G2

LG G2 with Cyanogenmod 12.0

Nexus 5

Nexus 4

Sony Ericsson phones

Motorola Moto G with Cyanogenmod

Motorola Moto E with Cyanogenmod

Motorola Moto G 2014

Motorola Moto X Style (Pure) 2015

OnePlus One

Galaxy S4

Galaxy Note 2

Huawei Ideos X5

Sony Xperia Z3 and Z3 Compact

Sony Xperia Z Ultra

Xiaomi Redmi 1S

Xiaomi Redmi 3S

Galaxy Ace 2

Xiaomi MI3

Galaxy Note 4

Asus Zenfone 2 ZE551ML

Asus Zenfone 2 Laser (Z00L/Z00T)

Sony Xperia Z5 Premium E6853

Sony Xperia Z5 Compact

Xiaomi Redmi 2

Sony Xperia SP

http://forum.xda-developers.com/xperia-sp/development/kernel-helium-v1-t3251298

Xiaomi Redmi Note 3

Samsung Galaxy Tab 2 (any espresso3g based device)

Other devices

Scripting

There is a possibility to send keypresses in an automated way, using terminal emulator for Android or similar app. This is done using hid-gadget-test utility.

First, copy this utility to your device.

adb push hid-gadget-test /data/local/tmp
adb shell chmod 755 /data/local/tmp/hid-gadget-test

You will need to set world-writable permissions on /dev/hidg0, or run hid-gadget-test from root shell.

adb shell
su
chmod 666 /dev/hidg0 /dev/hidg1

To always have root shell, so you don't need to enter 'su' each time, run command

adb root

Then, use hid-gadget-test to send keypresses.

adb shell
cd /data/local/tmp

# Send letter 'a'
echo a | ./hid-gadget-test /dev/hidg0 keyboard

You can also run this command without launching ADB shell, from shell script or .bat file.

adb shell 'echo a | /data/local/tmp/hid-gadget-test /dev/hidg0 keyboard'

Advanced examples.

# Send letter 'B'
echo left-shift b | ./hid-gadget-test /dev/hidg0 keyboard

# Send string 'abcdeZ'
for C in a b c d e 'left-shift z' ; do echo "$C" ; sleep 0.1 ; done | ./hid-gadget-test /dev/hidg0 keyboard

# You may combine several modifier keys
echo left-ctrl left-shift enter | ./hid-gadget-test /dev/hidg0 keyboard

# Try to guess what this command sends
echo left-ctrl left-alt del | ./hid-gadget-test /dev/hidg0 keyboard

# Bruteforce 4-digit PIN-code, that's a particularly popular script
# that people keep asking me for. It executes for 42 hours.
for a in 0 1 2 3 4 5 6 7 8 9; do
for b in 0 1 2 3 4 5 6 7 8 9; do
for c in 0 1 2 3 4 5 6 7 8 9; do
for d in 0 1 2 3 4 5 6 7 8 9; do
echo $a $b $c $d
for C in $a $b $c $d enter ; do echo "$C" ; sleep 0.2 ; done | ./hid-gadget-test /dev/hidg0 keyboard
sleep 15
done
done
done
done

# Press right mouse button
echo --b2 | ./hid-gadget-test /dev/hidg1 mouse

# Hold left mouse button, drag 100 pixels to the right and 50 pixels up, then release
echo --hold --b1 | ./hid-gadget-test /dev/hidg1 mouse
echo --hold --b1 100 0 | ./hid-gadget-test /dev/hidg1 mouse
echo --hold --b1 0 -50 | ./hid-gadget-test /dev/hidg1 mouse
echo --b1 | ./hid-gadget-test /dev/hidg1 mouse

You can check the modification time of file /sys/devices/virtual/hidg/hidg0/dev to know when the USB cable has been plugged into PC, however this does not always work, so it's better to simply check if hid-gadget-test returned an error.

Here's a sample shell script that will send a predefined key sequence when USB cable is plugged into PC:

#!/system/bin/sh
while true; do
    until echo volume-up | ./hid-gadget-test /dev/hidg0 keyboard >/dev/null 2>&1; do
        sleep 2
    done
    echo "USB cable plugged"
    sleep 1
    for C in 'left-meta r' c m d enter s t a r t space i e x p l o r e space x x x period c o m enter \
        ; do echo "$C" ; sleep 0.3 ; done | ./hid-gadget-test /dev/hidg0 keyboard
    echo "Done sending commands"
    while echo volume-up | ./hid-gadget-test /dev/hidg0 keyboard >/dev/null 2>&1; do
        sleep 2
    done
    echo "USB cable unplugged"
done

Here is the list of keys that hid-gadget-test utility supports

If you need to crack a PIN code, but the target system loses keypresses (happens in MacOS BIOS), there is a handy app for that, which uses camera to check if each keypress is recognized.

You can also run DuckyScript files used by USB Rubber Ducky keystroke injection tool, with the help of this neat shell script.

Compiling kernel

You have to run all following commands on Linux. Windows is not supported. These instructions are for Nexus 7 2012, change them for your device accordingly.

To compile kernel, launch commands

git clone https://android.googlesource.com/platform/prebuilts/gcc/linux-x86/arm/arm-eabi-4.8
git clone https://android.googlesource.com/kernel/tegra.git
export PATH=`pwd`/arm-eabi-4.8/bin:$PATH
export ARCH=arm
export SUBARCH=arm
export CROSS_COMPILE=arm-eabi-
cd tegra
git checkout android-tegra3-grouper-3.1-lollipop-mr1
patch -p1 < ../kernel-3.1.patch
make tegra3_android_defconfig
make -j4

https://github.com/pelya/android-keyboard-gadget/tree/master/patches/existing_tested - Tested patch files (pro) Tip: generic_kernel_version_3.xx.patch is just patches for AOSP roms and just by basic kernel versions. 3.01 is acceptable for 3.0.101. Other patch files is for devices only. The file named HTC Flounder will be acceptable ONLY FOR HTC Flounder!

To compile boot.img, launch commands

mkdir ~/bin
export PATH=~/bin:$PATH
curl http://commondatastorage.googleapis.com/git-repo-downloads/repo > ~/bin/repo
chmod a+x ~/bin/repo
mkdir aosp
cd aosp
repo init -u https://android.googlesource.com/platform/manifest -b android-4.4.2_r1
repo sync
cp -f ../tegra/arch/arm/boot/zImage device/asus/grouper/kernel
make -j4 TARGET_PRODUCT=aosp_grouper TARGET_BUILD_VARIANT=userdebug

You then can find boot.img in directory aosp/out/target/product/grouper.

Nexus 7 2012 does not put any SELinux restrictions on the files inside /dev, however most other devices typically restrict all access inside /dev for apps, which means you will be able to use hid-gadget-test command from the root shell, but the Android app will fail to launch.

SELinux can be temporarily disabled with a command

setenforce 0

however this will considerably weaken your device security, so it's better to add specific SELinux exception for /dev/hidg0 and /dev/hidg1.

SELinux rules can be found at path

device/asus/grouper/sepolicy

Replace asus/grouper with your device manufacturer/model, then add following lines to SELinux rules.

In file device.te - the declaration of SELinux security context type:

type hid_gadget_device, dev_type;

In file file_contexts - binding the device paths to the security context:

# USB Gadget
/dev/hidg(.*)                        u:object_r:hid_gadget_device:s0

In file app.te - the rule itself to allow apps using this security context:

allow appdomain hid_gadget_device:chr_file rw_file_perms;

Then recompile boot.img.

Compiling USB Keyboard app

To compile USB Keyboard app, install Android SDK and NDK from site http://developer.android.com/ , and launch commands

git clone https://github.com/pelya/commandergenius.git
cd commandergenius
git submodule update --init --recursive
rm -f project/jni/application/src
ln -s hid-pc-keyboard project/jni/application/src
./changeAppSettings.sh -a
android update project -p project

How it works

The custom kernel you have compiled adds two new devices, /dev/hidg0 for keyboard, and /dev/hidg1 for mouse.

You can open these two files, using open() system call, and write raw keyboard/mouse events there, using write() system call, which will be sent through USB cable to your PC.

A short description of the events format is provided below. For a more comprehensive overview see the OS Dev Wiki.

Keyboard events

Keyboard events are 8 bytes long: Offset Length Field
0 1 byte Modifier keys bitmask
1 1 byte Reserved padding
2 6 bytes Pressed keys in the order they were pressed in

First byte is a bitmask of currently pressed modifier keys:

typedef enum {
    LCTRL = 0x1,
    LSHIFT = 0x2,
    LALT = 0x4,
    LSUPER = 0x8, // Windows key
    RCTRL = 0x10,
    RSHIFT = 0x20,
    RALT = 0x40,
    RSUPER = 0x80, // Windows key
} ModifierKeys_t;

The second byte is reserved and usually ignored by software.

Remaining 6 bytes are a list of all other keys currently pressed, one byte for one key, or 0 if no key is pressed. A handy table with key scancodes can be found here.

Extended keys, such as Play/Pause, are not supported, because they require modifying USB descriptor in kernel patch.

Consequently, the maximum amount of keys that may be pressed at the same time is 6, excluding modifier keys. Professional or 'gamer' USB keyboards report several keyboard HID descriptors, which creates several keyboard devices in host PC, to overcome that 6-key limit.

Note that after writing an event the keys will be held indefinitely, so when finished an empty event should be sent to release all keys.

Mouse events

Mouse event is an array of 4 bytes, first byte is a bitmask of currently pressed mouse buttons:

typedef enum {
    BUTTON_LEFT = 0x1,
    BUTTON_RIGHT = 0x2,
    BUTTON_MIDDLE = 0x4,
} MouseButtons_t;

Remaining 3 bytes are X movement offset, Y movement offset, and mouse wheel offset, represented as signed integers. Horizontal wheel is not supported yet.

See functions outputSendKeys() and outputSendMouse() inside file input.cpp for reference implementation.