Require Password (or encryption key) to ADB into VOXL2

John Nomikos

Good afternoon,

I was wondering if there was a built-in method to require the user to input a password or have a correct adb encryption key to ADB into the VOXL2.

I could not find documentation relating to this on ModalAI website, and a lot of advice online seems to be only applicable to android devices.

Is there an area on the VOXL2 where the adb server is hosted so I can tinker around with it? Or is the adb functionality baked into the firmware itself?

The goal is to make the system more secure by only allowing authorized users to adb in.

If there is no way to require a password for adb on the VOXL2, is there a way to disable adb?

I have been able to change the ssh password which is nice.

Thank you,

John Nomikos.

Moderator

@John-Nomikos This might be helpful: https://android.stackexchange.com/questions/171934/storage-location-of-adb-keys/219320#219320

John Nomikos

@Moderator

Tried what that article suggested and did some research. I think adb encryption is not a feature on adb daemon for linux devices, and is only available on actual android devices. I could be wrong, but it appears that way. Could also be a feature on newer adb daemon.

Regardless, I think it might be possible for me to open up a USB port on an extension board for ssh. That way I could have password protected serial access while having adb disabled. Am I wrong in thinking this?

Alex Kushleyev

@John-Nomikos , yes this should work.

You can test temporarily disabling adb using the following command:

systemctl stop adbd

if you are running an adb session, you will get disconnected after running this command and no longer able to adb into the device. After reboot, the adb daemon will restart. In order to disable the adb daemon from autostarting at boot, you can run:

#WARNING: if you run this, adb connection will be disabled after reboot
#make sure you know how to re-enable it
#(via ssh connection or forcing fastboot and re-flash the board)
systemctl disable adbd

This will not stop the currently running adb server, but will prevent auto start after reboot

John Nomikos

@Alex-Kushleyev Thank you for the advice.

Since adbd is a static service (the usb service depends on it), it cannot be disabled through a systemctl disable.

I am going to take a look at other methods to disable it.

Alex Kushleyev

@John-Nomikos , do you mean that if you disable adbd then USB stops working? i did not check that.

John Nomikos

I was able to "disable adb" by simply changing the name of the adbd executable to .adbd

John Nomikos

@Alex-Kushleyev I mean, since it is a static service, disabling it does not actually disable it. It appears to do nothing. Upon rebooting, adb still works

Alex Kushleyev

@John-Nomikos i see, yes, most likely due to:

/lib/systemd/system/multi-user.target.wants/adbd.service

That re-enables it after reboot..

Anyway, it looks like you found a workaround. Alternatively you could potentially remove that dependency from multi-user.target.wants/ but i have not tested that