`GetConfComputeGpuAttestationReport` does not accept a nonce

[derpsteb]

Hey,

the function GetConfComputeGpuAttestationReport does currently not accept a nonce for the report generation. This is insecure for CC use cases because an attacker might record a valid report once and replay it to a victim multiple times/on different machines, potentially with a modified GPU attached.

We have implemented this in our fork here. This works fine so it seems to be supported by the runtime.

Could you update that function?
Thanks,
Otto

[klueska]

I checked with the NVML team and they confirmed that if you pass a nonce in the calling struct to the underlying C API, then it will be used by the driver (rather than generating one on the fly).

I'll need to think about the right API for this because we don't like to stray too far from the underlying C API (with the exception of transforming inputs meant as return values to actual return values). In this case though, the argument to the C API is both a valid input AND a place to store the return value...

[derpsteb]

Hey. Did you have a chance to consider this? Would be cool if we could drop our fork.

[jmomort]

Note that the python nvtrust library that NVIDIA owns does indeed use the nonce: https://github.com/NVIDIA/nvtrust/blob/02b2d22211fb506ab5dce0a23b15858d993cf6d0/guest_tools/gpu_verifiers/local_gpu_verifier/src/verifier/nvml/__init__.py#L195-L199

So I think it's useful to have this upstream and available in golang, too rather than to fork.

[jmomort]

Can be resolved with #140

[klueska]

I'm looking at introducing an option to generically pass the return-value-as-argument (similar to what the C API does) in order to future proof support for this (and any future changes like it).

[klueska]

The following PR has been merged to address this and is included in the v0.13.0-1 tag: #159