[Caml-list] Implementing JWT RS256 verification

[Malcolm Matalka <mmatalka@gmail.com>]

Hello,

I'm trying to implement verification of JWT's signed with RS256 and
having some trouble finding the crypto library I should use for this.
Nocrypt and CryptoKit are the obvious choices by searching opam, however
neither of them seem to quite have what I'm looking for.  RS256 is RSA
with SHA256 and something called PKCS1v1.5 for padding.  I see both of
these libraries have RSA options but it doesn't seem possible to specify
the hashing algorithm.  Nocrypto has a PKCS1v1.5 module in the RSA
module but no hash.  When I call [sig_decode] on my message I get back
a message text but it also doesn't seem to match what I'm expecting.

My input is the message, the signed signature, and the public key, and
I'd like to know verify these match correctly.

I really don't know much about crypto and am just trying to implement a
spec.  Anyone have a suggestion for what library I should use?  Am I
just missing something?

Thanks,
/Malcolm