Comment by wizeman | Hacker News Reader

Comment by wizeman | Hacker News Reader

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> That's just an argument for better testing. That's not implementation verification.

No, I'm not talking about testing, I'm talking about really basic formal verification:

forall (x: Certificate), verify_certificate(x, flags = 0) == invalid ==> verify_certificate(x, flags = STRICT) == invalid

This is trivial to specify and almost as trivial to prove to be correct for all inputs. Testing can't do that, no matter how good your testing.

> Only if you thought to write that test to begin with. Writing a test for everything is... not really possible.

I agree, but I'm not talking about testing. I'm talking about formal verification.

> It's not. The reason the strictness flag was added was that OpenSSL was historically less strict than the spec demanded. It turns out that when you're dealing with more than 30 years of history, you get kinks in the works. It wouldn't be different for whatever thing replaces PKIX.

That's totally fine and wouldn't affect the verification of that function at all. This is a very simple property to verify and it would avoid this bug and all similar bugs in that function (even if that function calls other functions, no matter how large or complex they are).

Other functions also have such easy to verify properties, this is not hard at all to come up with (although sure, some more difficult properties might be harder to verify).

> You must be very popular at parties.

I didn't want to be dismissive of OpenSSL devs or other devs in general, I just find it frustrating that there are so many myths surrounding this topic, and a lot less education, interest and investment than I think there should be, nowadays.

You are confusing verification as in "certificate" with verification as in "theorem proving", and you are still assuming a formal description of what to verify (which I'll remind you: doesn't exist). And then you go on to talk about myths and uneducated and uninterested devs. Your approach is like tilting at windmills, and will achieve exactly as much.

If I understood you correctly, then I am not confusing those two things.

Maybe you haven't noticed but I actually wrote a theorem about a hypothetical verify_certificate() function in my previous comment. Maybe you also haven't noticed, but I didn't need a formal description of how certificate validation needs to be done to write that theorem.

And I assure you, if the implementation of verify_certificate() is anything except absolute garbage, it would be very easy to prove the theorem to be correct. I actually have some experience doing this, you know? I'm not just parroting something I read, I've proved code to be 100% correct multiple times using formal verification (i.e. theorem proving) tools. That is, according to certain basic and reasonable assumptions, of course, like e.g. the hardware is not faulty or buggy while running the code, and that the compiler itself is not buggy, which would be a lot more rare than a bug in my code -- and even then, note that compilers and CPUs can be (and have been) formally verified.

Maybe you don't agree with my approach but I think it's the most realistic one for a project such as this and I am absolutely confident it would be practical, would completely eliminate most (i.e. more than 50%, at least) existing bugs with minimal verification effort (which almost anyone would be capable of doing with minimal training), and would steadily become more and more bug-free with additional, incremental verification (i.e. theorem proving) and refactoring effort.

https://project-everest.github.io/ :

> Focusing on the HTTPS ecosystem, including components such as the TLS protocol and its underlying cryptographic algorithms, Project Everest began in 2016 aiming to build and deploy formally verified implementations of several of these components in the F* proof assistant.

> […] Code from HACL*, ValeCrypt and EverCrypt is deployed in several production systems, including Mozilla Firefox, Azure Confidential Consortium Framework, the Wireguard VPN, the upcoming Zinc crypto library for the Linux kernel, the MirageOS unikernel, the ElectionGuard electronic voting SDK, and in the Tezos and Concordium blockchains.

S2n is Amazon's formally verified TLS library. https://en.wikipedia.org/wiki/S2n

IDK about a formally proven PKIX. https://www.google.com/search?q=formally+verified+pkix lists a few things.

A formally verified stack for Certificate Transparency would be a good way to secure key distribution (and revocation); where we currently depend upon a TLS library (typically OpenSSL), GPG + HKP (HTTP Key Protocol).

Fuzzing on an actual hardware - with stochastic things that persist bits between points in spacetime - is a different thing.

Funny, the first hit for that search you linked is... my comment above. The "few things" other than that are for alternatives to PKIX, which is fine and good, but PKIX will be with us for a long time yet. As for Everest, it jives with what I wrote above, that verified implementations of TLS are feasible (Everest also implements QUIC and similar), but -surprise!- not listed is PKIX.

I know, it sounds crazy, really crazy, but PKIX is much bigger than TLS. It's big. It's just big.

The crypto, you can verify. The session and presentation layers, you can verify. Heck, maybe you can verify your app. PKIX implementations of course can be verified in principle, but in fact it would require a serious amount of resources -- it would be really expensive. I hope someone does it, to be sure.

I suppose the first step would be to come up with a small profile of PKIX that's just enough for the WebPKI. Though don't be fooled, that's not really enough because people do use "mTLS" and they do use PKINIT, and they do use IPsec (mostly just for remote access) with user certificates, and DoD has special needs and they're not the only ones. But a small profile would be a start -- a formal specification for that is within the realm of the achievable in reasonably short order, though still, it's not small.

Both a gap and an opportunity; someone like an agency or a FAANG with a budget for something like this might do well to - invest in the formal methods talent pipeline and - very technically interface with e.g. Everest about PKIX as a core component in need of formal methods.

"The SSL landscape: a thorough analysis of the X.509 PKI using active and passive measurements" (2011) ... "Analysis of the HTTPS certificate ecosystem" (2013) https://scholar.google.com/scholar?oi=bibs&hl=en&cites=16545...

TIL about "Frankencerts": Using Frankencerts for Automated Adversarial Testing of Certificate Validation in SSL/TLS Implementations (2014) https://scholar.google.com/scholar?cites=3525044230307445257... :

> Our first ingredient is "frankencerts," synthetic certificates that are randomly mutated from parts of real certificates and thus include unusual combinations of extensions and constraints. Our second ingredient is differential testing: if one SSL/TLS implementation accepts a certificate while another rejects the same certificate, we use the discrepancy as an oracle for finding flaws in individual implementations.

> Differential testing with frankencerts uncovered 208 discrepancies between popular SSL/TLS implementations such as OpenSSL, NSS, CyaSSL, GnuTLS, PolarSSL, MatrixSSL, etc.

W3C ld-signatures / Linked Data Proofs, and MerkleProof2017: https://w3c-ccg.github.io/lds-merkleproof2017/

"Linked Data Cryptographic Suite Registry" https://w3c-ccg.github.io/ld-cryptosuite-registry/

ld-proofs: https://w3c-ccg.github.io/ld-proofs/

W3C DID: Decentralized Identifiers don't solve for all of PKIX (x.509)?

"W3C DID x.509" https://www.google.com/search?q=w3c+did+x509

Thanks for the link about frankencerts!

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