Problem with 'sgx_ra_msg3_t' mac field

Fabio_S_2 — Sun, 26 Jan 2020 19:59:23 GMT

On the latest version of developer reference (2.8 - p368), the 'mac' field is described as:

"AES-CMAC of g_a, ps_sec_prop, GID, and quote[], using SMK."

But the CMAC function returns a different value. If I remove the GID, the CMAC function result matches the mac field value. Someone else had the same problem?

Hello Fabio, you are correct.

JesusG_Intel — Tue, 28 Jan 2020 21:42:02 GMT

Hello Fabio, you are correct. The developer reference has a typo, it should not include the GID in the mac calculation. It should read: "AES-CMAC of g_a, ps_sec_prop, and quote[], using SMK.” The correct CMAC calculation for msg3 can be seen in Figure 3, which shows the full Remote Attestation Flow, on this page.

We will fix this error in the next revision of the document. Thank you for pointing it out.

Regards,

Jesus

topic Hello Fabio, you are correct. in Intel® Software Guard Extensions (Intel® SGX)

Problem with 'sgx_ra_msg3_t' mac field

Hello Fabio, you are correct.