topic index 1 in tdxtcbcomponents in Intel® Software Guard Extensions (Intel® SGX)

index 1 in tdxtcbcomponents

UsamaS — Mon, 04 Sep 2023 08:11:30 GMT

In the "Get TDX TCB Info" flow (https://api.portal.trustedservices.intel.com/documentation#pcs-tcb-info-tdx-v4), step 4 states:

"For the selected TCB level verify that SVN at index 1 in tdxtcbcomponents array matches the value of SVN at index 1 in TEE TCB SVNs array (from TD Report in Quote). In case of a mismatch the selected TCB level should be rejected as TCB Info that was used for the comparison is not supported for this platform configuration."

My question is:

What is so special about index 1 that it requires an equality check? What does index 1 represent? Typically all SVNs have a non-equality check (>=) as in step 3 (a,b,c).

Re:index 1 in tdxtcbcomponents

Peh_Intel — Wed, 06 Sep 2023 01:07:01 GMT

Hi UsamaS,

Thanks for reaching out to us.

Let me check with the relevant team and get back to you at the earliest.

Regards,

Peh

Re:index 1 in tdxtcbcomponents

Peh_Intel — Fri, 15 Sep 2023 01:04:28 GMT

Hi UsamaS,

Thanks for your patience. I just received the updates as follow.

This index 1 SVN is the TDX Module major version. Originally, there was only 1 TDX 1.0 module, so the SVN had to match. Now that we have TDX 1.5 coming, it has a new major version, so the logic has to change, and those steps will also. The API doc will be updated soon to reflect this.

Regards,

Peh

Re:index 1 in tdxtcbcomponents

Peh_Intel — Fri, 22 Sep 2023 05:29:21 GMT

Hi UsamaS,

This thread will no longer be monitored since we have provided answer. If you need any additional information from Intel, please submit a new question.

Regards,

Peh