Re: [PATCH v2] selftests/sgx: Fix Q1 and Q2 calculation in sigstruct.c

[Jarkko Sakkinen]

On Mon, Jul 05, 2021 at 08:09:21AM +0300, Jarkko Sakkinen wrote:
> From: Tianjia Zhang <tianjia.zhang@xxxxxxxxxxxxxxxxx>
> 
> Q1 and Q2 are numbers with *maximum* length of 384 bytes. If the calculated
> length of Q1 and Q2 is less than 384 bytes, things will go wrong.
> 
> E.g. if Q2 is 383 bytes, then
> 
> 1. The bytes of q2 are copied to sigstruct->q2 in calc_q1q2().
> 2. The entire sigstruct->q2 is reversed, which results it being
>    256 * Q2, given that the last byte of sigstruct->q2 is added
>    to before the bytes given by calc_q1q2().
> 
> Either change in key or measurement can trigger the bug. E.g. an unmeasured
> heap could cause a devastating change in Q1 or Q2.
> 
> Reverse exactly the bytes of Q1 and Q2 in calc_q1q2() before returning to
> the caller.
> 
> Fixes: dedde2634570 ("selftests/sgx: Trigger the reclaimer in the selftests")

Oops :-(

Was meant to be

Fixes: 2adcba79e69d ("selftests/x86: Add a selftest for SGX")

/Jarkko