intel / intel/confidential-computing.tdx.tdx-module
How to get the reference value of MRSEAM for each build version of TDX-Module?
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Description
Hi, I am currently working on a project involves analyzing TDX measurement results.
I created a TD-enabled instance on [Google Cloud's CVM](https://cloud.google.com/confidential-computing/confidential-vm/docs/create-a-confidential-vm-instance#amd-sev-snp) and retrievered the attestation (i.e., the TD Quote) using [google/go-tdx-guest](https://github.com/google/go-tdx-guest). After verifying the validity of the certificates and signatures, I continued to check the measurement results (including MRSEAM, MRTD, RTMR) inside the TD Report. However, to my surprise, I can hardly find the expected reference values for these measurement results.
The measurement most relevant to this repo is the MRSEAM value. According to Intel TDX , it is the the measurement of the TDX-Module and is recored on the `TEE_TCB_INFO` structure in the TD Quote (see Section 12.3 of [TDX Module Base Specification](https://cdrdv2.intel.com/v1/dl/getContent/733575)). Expected MRSEAM value is stored in `SEAM_SIGSTRUCT.MRSEAM` (see Section 4.2 of [SEAM Loader Interface specification](https://cdrdv2.intel.com/v1/dl/getContent/733584)).
I have the following questions:
1. Shouldn't MRSEAM be consistent across different BIOS settings and _only_ depend on the specific build version of TDX-Module binary?
2. Does Intel publish the reference value of MRSEAM for each build version of TDX-Module?
3. Is there any guidance on how to reproduce this reference value **locally** (for both TDX-enabled machine and non TDX machine)?
Additionally, I know that Intel provides the [Trust Authority](https://docs.trustauthority.intel.com/main/articles/introduction.html) attestation services for customers. However, since I currently do not have access to it, I am curious about the scope of its attestation.
4. Does it only checks the validity of the certificates and signatures, or does it also check if the measurements results matched references values?
5. Since MRSEAM is derived from the TDX-Module, it seems feasible for Intel to check the MRSEAM value. Will Intel Trust Authority check MRSEAM value?
6. But how does Intel check whether MRTD and RTMR are correct if these values depend on the firmware and OS image that the TD instance was created from (in my case, the OVMF and OS image Google Cloud are using)?
Any insights or guidance would be greatly appreciated! Thanks!
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