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Qubes OS and 3mdeb 'minisummit' 2019

In May we had pleasure to meet with Marek Marczykowski-Górecki in 3mdeb office in Gdańsk, Poland. Since we are long term fans of Qubes OS and its approach to security, as also fans of Joanna Rutkowska security research in area of firmware and computer architecture, we couldn’t miss the opportunity and decided to organize one day event during which we discussed topics at Qubes OS and firmware boundary.

Humorously we called it “minisummit”. Topics discussed and related presentations:

There were also lot of side-talks, but overall agenda was as above. Below I will elaborate more on presented topics below.

Qubes OS certification

Various 3mdeb customers are interested in Qubes OS certification. Recently Qubes OS announced on their website that Insurgo PrivacyBeast X230 Laptop meets and exceeds certification criteria. There is nothing that prevent hardware vendors to certify their hardware, but some firmware requirements have to be fulfilled:

  • hardware should run only open-source boot firmware - there are some technical exceptions to that e.g. CPU vendor binary blobs like FSP, AGESA, ME and PSP
  • properly exposed advanced hardware features for Intel those are VT-x, VT-d and SLAT
  • ACPI tables that expose above features to OS should be constructed correctly
    • DMAR for Intel and IVRS for AMD

Enabling or improving support of above features definitely lay in area of 3mdeb expertise, so if you looking for someone who can help you in Qubes OS hardware certification please contact us.

As mentioned on slides linked above we discussed also:

  • Alternative computer architectures that have potential of being not-harmful as x86 (in opposition to Joanna paper). Unfortunately we can’t see shiny future right now. Qubes OS focus on end-user devices, so laptops and workstations. It looks like we would have to wait little bit for reasonably performing ARM systems. There is also some hope in OpenPOWER and RISC-V, but ports to those architectures would require reasonably market demand for which we don’t see potential right now. Interestingly there is 2BTC bounty for Power Architecture support in Qubes OS you can read about it here.
  • It looks like Qubes OS development doesn’t face any significant issues from firmware level. It’s good to know that hardware Qubes OS operate on reasonable quality firmware.

Xen and Qubes OS status

There was no formal presentation about that topic, but discussion drifted to that topic, so it is definitely worth to mention. Of course we are not hard-core Xen or Qubes OS developers, so some of those information may be not complete:

  • There are some issues with PCI pass-through. Qubes OS would like to use that feature more, but because of complex PCI architecture and design assumptions in Xen, leveraging that feature is not so easy.
  • There is some problem PCI hot-plug since all connected devices automatically appear in dom0, which can cause some security issues if malicious device would be connected. Technically speaking Xen community know how to solve that, but there are no resources available at this point to address the problem.
  • USB Type C is another problem since host controller is visible only after connecting device, so OS doesn’t have control over it before
  • It seems that correct support for IOMMU can mitigate most of above problems
  • There are very interesting improvement in new microarchitectures like Denverton, especially VT-c, but Xen still doesn’t have support for that
  • There are also know issues in GPU support e.g. Nvidia requires dedicated, more expensive hardware, if it would be used in virtualized environment
  • Because of above problems and other reasons Qubes OS community consider KVM support

We also discussed how 3mdeb can involve in improving Qubes OS and Xen and of course community activity would be best approach. Of course as for-profit organization we have to align that with some business activity. We plan to work on that in 2019. As first step towards that is this blog and following ideas for contribution.

Qubes OS build system

According to documentation Qubes OS should be build using rpm-based distro like Fedora. According to Marek build should also work on Debian without big issues. Definitely it is something to check and maybe improve documentation.

But moving forward discussion about Qubes OS build system, as Yocto Participants, we advertised OE/Yocto as build system for dom0 in Qubes OS. During that discussion various problems pop up:

  • OE/Yocto not verify hashes or does it in doubtful way. We started discussion about that on Yocto mailing list.
  • We can’t freeze dom0, we need flexibility in extending it additional software through package manager - as Marek mentioned this statement is valid until GUI is in dom0 and pointed us to The Update Framework website and Package Management Security paper. Goal is definitely to get rid of GUI from dom0.
  • We should treat big distros like Debian and Fedora as role models in package management, they already use lots of good practice that are not followed by OE/Yocto, because of that 3mdeb should understand better how Debian/Fedora does package management and help reflect best practice in OE/Yocto to improve probability of using it as dom0 build system.
  • Build system should not require networking connection, this is question about security as well as control over whole building process. If package build system download arbitrary code during build process then definitely we loosing control over each component verification. Secure build should be performed on air-gapped hardware/VM.
  • Not all recipes in OE/Yocto are reproducible, Debian solve that issue by stripping stuff causing problems, maybe that approach should be adapted in OE/Yocto. More details about reproducible builds can be found here. There is also discussion related to that topic here.
  • Toolchain flags for security hardening are not easy to set and use.
  • Qubes OS will use Mirage OS as firewall. It is sign of another interesting technology in service of security , namely unikernels. Marek mentioned that there is big potential for unikernels in Qubes OS e.g. GPG VM, because unikernels are in-line with system goals and design.
  • It looks unikraft evolve as unikernels build system, we are concerned about another build system which would be very hard to integrate. We wondered if it would be possible to build unikernels using OE/Yocto Marek commented that it would be hard or impossible in practice, because unikernels are assumed to be single statically linked binary with libraries and “kernel”, what means completely different result then OE/Yocto produce by default.

Above claims will be elaborated in following blog post and maybe even some contribution from 3mdeb. We are very concern about mentioned potential security flows and would like to help in improving OE/Yocto state as well as spreading the word about it, since we believe OE/Yocto has many benefits if we want to achieve long term stable and minimal dom0.

We plan to create OE/Yocto hardening guidelines which hopefully can help rise probability of using OE/Yocto as build system for Qubes OS dom0.

TPM2.0

It looks that TPM2.0 is not supported in Qubes OS mostly because nobody had time to take a look at it. From 3mdeb it would be ideal contribution especially if can be combined with open-source firmware based hardware like Librebox.

There are various other ways how TPM2.0 can be leveraged in Qubes OS e.g. PKCS #11, VPN.

fwupd

Marek mentioned that he is very interested in fwupd support in Qubes OS. 3mdeb already contributed to LFSV/fwupd project, by adding flashrom support and ability to update coreboot-based platforms. LVFS/fwupd is treated by 3mdeb as strategic project since it exist at OS and firmware boundary.

There is even discussion started in this topic here. Key problem at this point is that dom0 has no networking connection, so fwupd have to respect other means of getting information from LVFS servers.

Richard (LFVS maintainer) and 3mdeb team will attend OSFC 2019 we believe it would be good opportunity to talk more about issues that Qubes OS may consider.

Summary

Overall we would like to thank Marek for spending whole day with 3mdeb team and providing his insights about Qubes OS and its relation to firmware. For us it was important step to build relation and improve networking. We look for similar meetings in future and hope to see each other during various security conferences happen in this year.

If you think we can help in improving Qubes OS support for your hardware, help you with Qubes OS certification on firmware level or you looking for someone who can boost your product by leveraging advanced features of used hardware platform, feel free to book a call with us or drop us email to contact<at>3mdeb<dot>com. If you are interested in similar content feel free to sing up to our newsletter


Piotr Król
Founder and Embedded Systems Consultant at 3mdeb as well as CTO of vitroTV. Passionate about building firmware that enables advanced hardware features in modern products. Dedicated to customers that treat embedded software security and upgradability as forethought. In favor of fixed price projects with the clear definition of success. Available as freelance CTO for startups and small business.




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