Questions about implementations and types

[benluelo]

Hello, we are working on an implementation of the ics23 spec and we have a few questions about the spec and implementations found here.

• What is this check against 32 for?

  ics23/go/proof.go

  Line 158 in bf89d95

  if len(res) > int(spec.InnerSpec.ChildSize) && int(spec.InnerSpec.ChildSize) >= 32 {

• is ProofSpec.InnerSpec nullable/optional? afaict, every use site of that field requires it to be set, but I'm not 100% sure since in the testdata, it is omitted sometimes: https://github.com/cosmos/ics23/blob/master/go/proof_test.go#L36

• What are the validations against the IAVL spec in LeafOp.CheckAgainstSpec (go, rust) and InnerOp.CheckAgainstSpec (go, rust) for?

[colin-axner]

Not sure if you still need answers (if not can we close?)

(1) looks to be ensuring that the resulting child is not greater than the child size, but I'm unsure why the &&
(2) interesting question! I cannot fathom how an empty inner spec could ever be used in practice (this should probably be made more explicit in the code)
(3) I just deobfuscated the code. Along with other things, it ensures the prefix is bounded such that an attacker cannot use it to prove a key which doesn't exist