Hi all, we are hiring a remote worker and will be supplying a laptop to them. The laptop will be running a Debian variant of Linux on it.

We are a small shop and this is the first time we have entrusted somebody outside of our small pool of trusted employees.

We have sensitive client data on the laptop that they need to access for their day-to-day work.

However, if something goes wrong, and they do the wrong thing, we want to be able to send out some kind of command or similar, that will completely lock, block, or wipe the sensitive data.

We don’t want any form of spying or tracking. We are not interested in seeing how they use the computer, or any of the logs. We just want to be able to delete that data, or block access, if they don’t return the laptop when they leave, or if they steal the laptop, or if they do the wrong thing.

What systems are in place in the world of Linux that could do this?

Any advice or suggestions are greatly appreciated? Thank you.

  • Max-P@lemmy.max-p.me
    2·
    27 days ago

    You’ll first want to lock down the laptop with using the TPM so it only boots kernels signed by you, and also encrypt the drive using the TPM as the locking key so the key is only ever available to a kernel you signed. From there you’ll probably want to use dm-verity to also verify the integrity of the system or at least during the boot process.

    Then, on top of that, once online and the machine is still authorized to access that data, you download a key from a server under your control to unlock the rest of the drive (as another partition). And log those accesses of course.

    Then, when you want to revoke access to it, all you have to do is stop replying with the key whenever requested. That just puts a ton of hurdles to overcome to access the data once the server stops handing the key. They would have to pry out the key from the TPM to unlock the first stage and even be able to see how it works and how to potentially obtain the key. They could still manage to copy the data out while the system is fully unlocked and still trusted, which you can make a lot harder by preventing access to external drives or network shares. But they have physical access so they kind of have the last word if they really really really want to exfiltrate data.

    This is the best you can do because it’s a passive: you stop supplying the unlock key so it’s stuck locked encrypted with no key, so the best they can do is format the laptop and sell it or use it for themselves. Any sort of active command system can be pretty easy to counter: just don’t get it online if you suspect the kill signal is coming, and it will never come, and therefore never get wiped. You want that system to be wiped by default unless your server decides it’s not.