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OpenKuBSD design document

Author: Solène
Date: 06 June 2023
Tags: openbsd qubesos security

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Introduction

I got an idea today (while taking a shower...) about _partially_ reusing Qubes OS design of using VMs to separate contexts and programs, but doing so on OpenBSD.

To make explanations CLEAR, I won't reimplement Qubes OS entirely on OpenBSD. Qubes OS is an interesting operating system with a very strong focus on security (from a very practical point of view ), but it's in my opinion overkill for most users, and hence not always practical or usable.

In the meantime, I think the core design could be reused and made it easy for users, like we are used to do in OpenBSD.

Why this project?

I like the way Qubes OS allows to separate things and to easily run a program using a VPN without affecting the rest of the system. Using it requires a different mindset, one has to think about data silos, what do I need for which context?

However, I don't really like that Qubes OS has so many opened issues, governance isn't clear, and Xen seems to be creating a lot of troubles with regard to hardware compatibility.

I'm sure I can provide a similar but lighter experience, at the cost of "less" security. My threat model is more preventing data leak in case of a compromised system/software, than protecting my computer from a government secret agency.

After spending two months using "immutables" distributions (openSUSE MicroOS, Vanilla OS, Silverblue), where they all want to you use root-less containers (with podman) through distrobox, I hate that idea, it integrates poorly with the host, it's a nightmare to maintain, can create issues due to different versions of programs altering your user data directory, and that just doesn't bring anything much to the table except allowing users to install software without being root (and without having to reboot on those systems).

Key features

Here is a list of features that I think good to implement.

vmd based OpenBSD and Alpine template (installation automated), with the help of qcow2 format for VMs, it's possible to create a disk based on another, a must for using templates
disposable VMs, they are started from the template but using a derived disk of the template, destroyed after use
AppVM, a VM created with a persistent /home, and the rest of the system is inherited from the template using a derived qcow2 from template
VPN VMs that could be used by other VMs as their network source (Tor VPN template should be provided)
Simple configuration file describing your templates, your VMS, packages installed (in templates), and which network source to use for which VM
Installing software in templates will create .desktop files in menus to easily start programs (over `ssh -Y`)
OpenBSD host should be USABLE (hardware acceleration, network handling, no perf issues)
OpenBSD host should be able to transfer files between VMs using ssh
Audio disabled by default on VMs, sndio could be allowed (by the user in a configuration file) to send the sound to the host
Should work with at least 4 GB of memory (I would like to make just 2 as a requirement if possible)

Some kind of quick diagram explaining relationship of various components. This doesn't show the whole picture because it wouldn't be easy to represent (and I didn't had time to try doing so yet):

OpenKuBSD design diagram

What I don't plan to do

HVM support and passthrough, this could be done one day if vmd supports passthrough, but this creates too much problems, and only help security for niche use case I don't want to focus on
USB passthrough, too complex to implement, too niche use case
VM RPC, except for the host being able to copy files from one vm to the other using ssh
An OpenBSD distribution, OpenKuBSD must be installable on top of OpenBSD with the least friction possible, not as a separate system
Support Windows guests

Roadmap

The first step is to make a proof of concept:

generate the OpenBSD template automatically
being able to start a disposable VM using the OpenBSD template
generate an OpenBSD Tor template
being able to use it in the disposable VM

Trivia

I announced it as OpenKuBISD, but I prefer to name it OpenKuBSD :)