Engineering with Enclaves
onefootprint.com
onefootprint.com
There are some third party implementations available, but we'd worry too much about maintenance of those to use them. Something officially supported would really be helpful.
The idea is basic secret forwarding - you want to send a secret to many destinations, but find it too cumbersome to encrypt it with each destination’s public key, or you might not have all the public keys in hand.
To address this, we provide you with a code base running inside a Nitro Enclave. You have a KMS account, and you configure it to allow access only to 1) our code base hash AND 2) only when that signed code is running inside a certified Nitro Enclave.
The enclave bootstraps itself on first run by generating a key pair and encrypting the private key with a data key from KMS.
You can then send a secret to the enclave encrypted with its public key, and verifiably know exactly what’s going to happen. Only trusted code running inside the secure confines of the enclave would be able to decrypt and operate on the secret.
There’s lots of gotchas - if you make a server in the enclave remember to use a server that binds on the VSOCK AF and port; on the host run socat or a systemd socket unit to translate HTTP/TCP calls into the enclave’s VSOCK. Make sure you enrich all requests passed into the enclave with all the data and encrypted artefacts it needs to work. Make sure to send the encrypted artefacts out from the enclave and store them safely.
We do this for cinema movie distribution - filmmakers just send their movie’s encryption key to this system, and it sends it out to the public key of each projector in each screen in each theatre in the world. And big studios can verify that their billion dollar movies aren’t going anywhere other than their chosen rules.
Do they provide certifications or audits confirming conformance to multi-level security guarantees? Or do they provide you detailed specifications allowing you to evaluate that yourselves? Did you run red team exercises that resulted in no detected deficiencies as would be required by a multi-level security claim?
Which is what we and our customers do already, when we run our workloads on it.
We know this is a problem, but this is where we’re ok with drawing the line. If you’ve seen Reflections on Trusting Trust you’ll know we have to draw the line somewhere.
In the case of the cloud I haven't seen FIPS certification of any of the internal systems from cloud providers yet.
This need for certification needs to be balanced against usability - it's relatively easier to certify a hardware design that has no compute, or a physically isolated CPU and memory like a SEE Machine, but it's also much less useful.
We prefer general purpose machines that have the same strength barriers that we already know are being deployed to protect customers from each other, that are being probed and tested all day every day both by AWS internally and by bad actors trying to steal other people's data. The lack of known pending exploits, continuous patching by AWS and being battle tested on a massive scale is more important to us than a FIPS certification at this point. Although if AWS managed to get FIPS to certify the Nitro system it would be a big plus.
Literally everybody has been promising general purpose machine isolation for decades and basically every one of them has failed. Actually designing such a system is a extraordinary claim demanding extraordinary evidence. Actual standards that can actually distinguish such a property such as the Common Criteria at EAL 6 and 7 require rigorous verification work such as formal proofs of correctness to actually positively assert such properties. It is ridiculous that people keep believing such claims without any guarantees, verifications, or audits when everything uncertified is so catastrophically bad at achieving isolation.
To quote Theo de Raadt:
“You are absolutely deluded, if not stupid, if you think that a worldwide collection of software engineers who can't write operating systems or applications without security holes, can then turn around and suddenly write virtualization layers without security holes.
You've seen something on the shelf, and it has all sorts of pretty colours, and you've bought it.“
Very good isolation at all layers, formal verification, highly resistant to tampering, fuzzing, and so on. Every single part was locked down in a very thoughtful way.
There may be no legal liability with the purchase contracts, but these manufacturers certainly seem to approach the problem with the level of consideration that I’d hope for given the importance of the technology.
It sounds like Amazon should be getting that! I wonder if perhaps it's just ill-suited to service providers, and only really workable for hardware.
Unfortunately certification against that standard directly is no longer possible in the normal course because as part of the security assurance requirement (SAR) AVA_VLA_EXP.4 it requires a NSA penetration test and evaluation that identifies no deficiences to cross-verify the proofs of correctness.
However, with the amount of money the US government is spending on AWS it should be trivial for them to get such a certification done if they were competent to actually do it. In addition, you could always just use a comparable standard that replaces AVA_VLA with the standard AVA_VAN which just validates against a “generic nation-state attacker” similar to what PikeOS [3] did. Given that PikeOS is made by a relatively small company, especially compared to something like Amazon or even the just the AWS division, it would again be easy for Amazon to demonstrate such capability if they were competent to do so.
Instead Amazon is 100% guaranteed to fail such a evaluation like how Microsoft failed their evaluations because, like Microsoft, nobody in their organization has ever designed, worked on, or probably even seen a actual high security system and they have no incentive to learn when they can just make up bullshit that people believe. Their organizations and management are structurally incapable of developing secure systems without a complete management and technology replacement.
[1] https://www.niap-ccevs.org/profile/Info.cfm?PPID=65&id=65
[2] https://www.commoncriteriaportal.org/files/epfiles/st_vid101...
[3] https://www.commoncriteriaportal.org/files/epfiles/1146a_pdf...
Consider a scenario where you need to compute some a function of secret data, but unfortunately that function isn't of the shape that any CC- or FIPS-certified solution (HSM or otherwise) supports out of the box, and ordering one to be built against your specifications would eat through your budget for the next 15-20 years. Your choices roughly are:
- Use a HSM anyway, but only use it to encrypt the data (or its encryption key), and have your application servers decrypt, evaluate the function, return the result and delete the data from memory every time they need to? Then you're arguably just doing fancy encryption at rest.
- Use enclaves. Even though they are much less hardened than a CC certified and audited solution, let's say you assign some probability to the event that somebody compromises them and burns the corresponding 0-day on you. Would you assert that that probability is 1? If not, why not still do it?
And you can still store the actual data encryption keys in a HSM and any higher-level features that it does support! In fact, if you use your HSM in a pretty low-level way (i.e. with an interface like "decrypt data x using key k"), access to the HSM needs to be guarded carefully, and enclaves can be a candidate for that.
- Don't evaluate the function, or possibly don't even store the data in the first place. The only problem with enclaves, in my view, is if they would make people disregard this option due to the misunderstanding that "enclaves are perfectly secure". (This applies to any security technology, but the fancier/more magical a solution looks like or is marketed as, the higher the temptation.)
- Do none of the above, but still store the data and evaluate the function on your systems. This is arguably the norm today in most organizations.
So I'm wondering what's the advantage of Nitro Enclaves? Better out of the box tooling?
Also, it's passingly strange to see PCRs mentioned with no mention of TPMs.
Side note - I work on confidential computing at Anjuna, would love to talk more.