Last year, we announced the Qubes-certified laptops program. The main purpose of the program is to provide a simple way for new users to get a laptop that can run Qubes OS well. Apart from “running Qubes well” we have not imposed any specific requirements thus far. Now, we’re introducing additional conditions, designed to also make such devices actually more secure than what one can get in a supermarket. The rules below will become obligatory for hardware to be certified for the upcoming Qubes 4.x branch. We expect the first release candidate (4.0-rc1) to be out in September and the final 4.0 sometime around the end of the year.
One of the most important security improvements that we plan to introduce with the release of Qubes 4 is to ditch paravirtualization (PV) technology and replace it with hardware-enforced memory virtualization, which recent processors have made possible thanks to so-called Second Level Address Translation (SLAT), also known as EPT in Intel parlance. SLAT (EPT) is an extension to Intel VT-x virtualization, which originally was capable of only CPU virtualization but not memory virtualization and hence required a complex Shadow Page Tables approach (which – we believed back then – was actually less attractive than the PV approach). We hope that embracing SLAT-based memory virtualization will allow us to prevent disastrous security bugs, such as the infamous XSA 148, publicly disclosed in October of last year, which – unlike many other major Xen bugs – regrettably did affect Qubes OS. Consequently, we will be requiring SLAT support of all certified hardware for Qubes OS 4 and later.
Another important requirement we’re introducing today is that Qubes-certified hardware should run only open-source boot firmware (aka “the BIOS”), such as coreboot. The only exception is the use of a (properly authenticated) CPU-vendor-provided blobs for silicon and memory initialization (see Intel FSP) as well as other internal operations (see Intel ME). However, we specifically require all code used for and dealing with the System Management Mode (SMM) to be open-source.
While we well recognize the potential problems that proprietary CPU-vendor code can cause, we are also pragmatic enough to realize that we need to take smaller steps first, before we can implement even stronger countermeasures such as the stateless laptop I proposed a few months ago. A switch to open source boot firmware is one such very important step on this roadmap.
Of course, to be compatible with Qubes OS, the BIOS must properly expose all the VT-x, VT-d, and SLAT functionality that the underlying hardware offers (and which we require). Among other things, this implies proper DMAR ACPI table construction.
Finally, we are going to require that Qubes-certified hardware does not have any built-in USB-connected microphones (e.g. as part of a USB-connected built-in camera) that cannot be easily physically disabled by the user, e.g. via a convenient mechanical switch. However, it should be noted that the majority of laptops on the market that we have seen satisfy this condition out of the box, because their built-in microphones are typically connected to the internal audio device, which itself is a PCIe type of device. This is important, because such PCIe audio devices are – by default – assigned to Qubes’ (trusted) dom0 and exposed through our carefully designed protocol only to select AppVMs when the user explicitly chooses to do so. The rest of the time, they should be outside the reach of malware.
While we also recommend a physical kill switch on the built-in camera (or, if possible, not to have a built-in camera), we also recognize this isn’t a critical requirement, because users who are concerned about it can easily deactivate it with… a piece of tape (something that, regrettably, cannot be easily done with a microphone).
Similarly, we don’t consider physical kill switches on Wi-Fi and Bluetooth devices to be mandatory. Users who plan on using Qubes in an air-gap scenario would do best if they manually remove all such devices persistently (as well as the builtin speakers!), rather than rely on easy-to-flip-by-mistake switches, while others should benefit from the Qubes default sandboxing of all networking devices in dedicated VMs.
We hope these updated hardware requirements will encourage the development of more secure and trustworthy devices capable of running Qubes OS and also pave the way for even more ambitious solutions, such as the stateless laptop.