support for pure-rust make credentials

[baloo]

This brings support for a pure rust implementation of make credentials which will not involve the TPM or tpm2-tss.

Fixes #160

[wiktor-k]

Looks really cool. Of course error handling and other niceties are missing but that's not the point. Happy to see tests, I've skimmed them.

Thanks! 👍

[baloo]

sha2::Sha256, aes::Aes128 here codes for EKHash and EkCipher.
Those should be read from the template of the EK ideally.

Although in reality, the template would have been dropped already and we're only working with a PEM encoded public key, and there should be some kind of default value.
https://github.com/tpm2-software/tpm2-tools/blob/master/tools/tpm2_makecredential.c#L340

Anyone with an opinion?

[ionut-arm]

Is your question about this test in particular, or about the interface of make_credential_ecc, and whether we can deduce the type params from the inputs?

I think generally you should be able to deduce the hash and the cipher for the EK if you know the nature of the public key, for example by doing the reverse of the mapping done here: https://github.com/parallaxsecond/rust-tss-esapi/blob/main/tss-esapi/src/abstraction/ek.rs

[baloo]

No that was an API question.

I know how to get the parameters from a Public, but I don't expect the public or its template to always available.

[baloo]

I've finished support for both RSA and ECC, and there is now error management.
There isn't much else I can do.

[ionut-arm]

Only had a brief look, will come back for more :)

[ionut-arm]

Is your question about this test in particular, or about the interface of make_credential_ecc, and whether we can deduce the type params from the inputs?

I think generally you should be able to deduce the hash and the cipher for the EK if you know the nature of the public key, for example by doing the reverse of the mapping done here: https://github.com/parallaxsecond/rust-tss-esapi/blob/main/tss-esapi/src/abstraction/ek.rs

[baloo]

There is something that locks up the TPM in the CI, but I don't know what it is.

EDIT: a regression in the weak key detection or something
EDIT2: no I'm just an idiot and somehow had the test backwards.

[su-sd]

This is getting into great shape 🔥
Thanks to anyone involved!

[baloo]

I've split the secret sharing, from the credentials which I intend to reuse for duplicate (#585)

[gibix]

I tested the pull request and is just great to have this feature coming! I noticed a bad error message that need to be documented. If the challenge payload is to big the error message is Invalid bytes(&[u8]) size(> 132), but the real allowed size of the payload is 96 bytes.

If you want to created a challenge from a bigger payload is considered safe to split in 96-bytes-long chunks and make separate attestation?