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Improving trust in the cloud with OpenStack and AMD SEV

By , September 13, 2019 1:00 pm

This post contains an exciting announcement, but first I need to provide some context!

Ever heard that joke “the cloud is just someone else’s computer”?

Coffee mug saying "There is no cloud. It's just someone else's computer"

Of course it’s a gross over-simplification, but there’s more than a grain of truth in it. And that raises the question: if your applications are running in someone else’s data-centre, how can you trust that they’re not being snooped upon, or worse, invasively tampered with?

Until recently, the answer was “you can’t”. Well, that’s another over-simplification. You could design your workload to be tamperproof; for example even if individual mining nodes in Bitcoin or Ethereum are compromised, the blockchain as a whole will resist the attack just fine. But there’s still the snooping problem.

Hardware to the rescue?

However, there’s some good news on this front. Intel and AMD realised this was a problem, and have both introduced new hardware capabilities to help improve the level to which cloud users can trust the environment in which their workloads are executed, e.g.:

  • AMD SEV (Secure Encrypted Virtualization) which can encrypt the memory of a running VM with a key which is only accessible to the owner of that VM. This is done on-chip so that even if you have physical access to the machine, it makes it a lot harder to snoop in on the running VM1.

    It can also provide the guest owner with an attestation which cryptographically proves that the memory was encrypted correctly and can only be decrypted by the owner.

  • Intel MKTME (Multi-Key Total Memory Encryption) which is a similar approach.

But even with that hardware support, there is the question to what degree anyone can trust public clouds run on proprietary technology. There is a growing awareness that Free (Libre) / Open Source Software tends to be inherently more secure and trustworthy, since its transparency enables unlimited peer review, and its openness allows anyone to contribute improvements.

And these days, OpenStack is pretty much the undisputed king of the Open Source cloud infrastructure world.

An exciting announcement

So I’m delighted to be able to announce a significant step forward in trustworthy cloud computing: as of this week, OpenStack is now able to launch VMs with SEV enabled! (Given the appropriate AMD hardware, of course.)

The new hw:mem_encryption flavor extra spec

The core functionality is all merged and will be in the imminent Train release. You can read the documentation, and you will also find it mentioned in the Nova Release Notes.

While this is “only” an MVP and far from the end of the journey (see below), it’s an important milestone in a strong partnership between my employer SUSE and AMD. We started work on adding SEV support into OpenStack around a year ago:

The original blueprint for integrating AMD SEV into nova

This resulted in one of the most in-depth technical specification documentations I’ve ever had to write, plus many months of intense collaboration on the code and several changes in design along the way.

SEV code reviews. Click to view in Gerrit!

I’d like to thank not only my colleagues at SUSE and AMD for all their work so far, but also many members of the upstream OpenStack community, especially the Nova team. In particular I enjoyed fantastic support from the PTL (Project Technical Lead) Eric Fried, and several developers at Red Hat, which I think speaks volumes to how well the “coopetition” model works in the Open Source world.

The rest of this post gives a quick tour of the implementation via screenshots and brief explanations, and then concludes with what’s planned next.

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