Allow temporary VM keyboard capture with user consent

sudo qubes-dom0-update python3-evdev

mkdir -p /home/user/bin
cat << 'EOF' | tee /home/user/bin/kbcapture.py > /dev/null
#!/usr/bin/python3
# First argument is a path to a keyboard input device e.g. /dev/input/eventX

import evdev
import subprocess
import re
import sys

def notify_send(summary, body):
    display = ':'+subprocess.check_output(['ls', '/tmp/.X11-unix/']).decode('utf-8').replace('X', '')[0]
    who = subprocess.check_output(['who']).decode('utf-8')
    user = [line for line in who.split('\n') if f'({display})' in line][0].split(None, 1)[0]
    uid = subprocess.check_output(['id', '-u', user]).decode('utf-8').rstrip()
    subprocess.Popen(['sudo', '-u', user, f'DISPLAY={display}', f'DBUS_SESSION_BUS_ADDRESS=unix:path=/run/user/{uid}/bus', 'notify-send', summary, body])

if len(sys.argv) == 1:
    notify_send('Keyboard capture ERROR', f"Specify the path to a keyboard input device as an argument.")
    sys.exit(1)

window = subprocess.check_output(['xdotool', 'getwindowfocus'])
try:
    qube_name = re.findall('"([^"]*)"', subprocess.check_output(['xprop', '_QUBES_VMNAME', '-id', window]).decode('utf-8'))[0]
except:
    notify_send('Keyboard capture ERROR', f"Couldn't get the qube's name from the focused window.")
    sys.exit(1)

try:
    kbd = evdev.InputDevice(sys.argv[1])
except:
    notify_send('Keyboard capture ERROR', f"Couldn't open the keyboard input device. Make sure that you passed the correct path as an argument.")
    sys.exit(1)

kbd.grab()

RCtrl = False
LCtrl = False

with evdev.UInput.from_device(kbd, name='kbdcapture') as ui:
    p=subprocess.Popen(['qvm-run', '-u', 'root', '--pass-io', f'--localcmd=input-proxy-sender {ui.device.path}', qube_name, 'input-proxy-receiver --keyboard'], stdout=subprocess.DEVNULL, stderr=subprocess.STDOUT)
    notify_send('Keyboard capture', f'dom0 keyboard is captured by the qube {qube_name}')
    for ev in kbd.read_loop():
        if ev.type == evdev.ecodes.EV_KEY:
            if (ev.code == evdev.ecodes.KEY_LEFTCTRL and ev.value == 1 and RCtrl or
                ev.code == evdev.ecodes.KEY_RIGHTCTRL and ev.value == 1 and LCtrl):
                p.terminate()
                notify_send('Keyboard capture', f'dom0 keyboard is released from the qube {qube_name}')
                kbd.ungrab()
                break
            else:
                ui.write(evdev.ecodes.EV_KEY, ev.code, ev.value)
            LCtrl = (ev.code == evdev.ecodes.KEY_LEFTCTRL and ev.value)
            RCtrl = (ev.code == evdev.ecodes.KEY_RIGHTCTRL and ev.value)
        else:
            ui.write(ev.type, ev.code, ev.value)
EOF
chmod +x /home/user/bin/kbcapture.py

sudo libinput list-devices

...

Device:           AT Translated Set 2 keyboard
Kernel:           /dev/input/event2
Group:            3
Seat:             seat0, default
Capabilities:     keyboard 
Tap-to-click:     n/a
Tap-and-drag:     n/a
Tap drag lock:    n/a
Left-handed:      n/a
Nat.scrolling:    n/a
Middle emulation: n/a
Calibration:      n/a
Scroll methods:   none
Click methods:    none
Disable-w-typing: n/a
Disable-w-trackpointing: n/a
Accel profiles:   n/a
Rotation:         n/a

...

sudo /home/user/bin/kbcapture.py /dev/input/eventX