linux-kernel - Re: [PATCH] selftests/sgx: fix EINIT failure dueto SGX_INVALID

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Message-ID: <YEk8f/29icpsUhas@kernel.org>
Date:   Wed, 10 Mar 2021 23:39:11 +0200
From:   Jarkko Sakkinen <jarkko@...nel.org>
To:     Jia Zhang <zhang.jia@...ux.alibaba.com>
Cc:     Andy Lutomirski <luto@...capital.net>,
        Tianjia Zhang <tianjia.zhang@...ux.alibaba.com>,
        Thomas Gleixner <tglx@...utronix.de>,
        Ingo Molnar <mingo@...hat.com>, Borislav Petkov <bp@...en8.de>,
        "H. Peter Anvin" <hpa@...or.com>,
        Sean Christopherson <seanjc@...gle.com>,
        Shuah Khan <shuah@...nel.org>, X86 ML <x86@...nel.org>,
        linux-sgx@...r.kernel.org,
        "open list:KERNEL SELFTEST FRAMEWORK" 
        <linux-kselftest@...r.kernel.org>,
        LKML <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH] selftests/sgx: fix EINIT failure dueto
 SGX_INVALID_SIGNATURE

On Wed, Mar 10, 2021 at 08:44:44PM +0800, Jia Zhang wrote:
> 
> 
> On 2021/3/2 下午9:47, Jarkko Sakkinen wrote:
> > On Mon, Mar 01, 2021 at 09:54:37PM -0800, Andy Lutomirski wrote:
> >> On Mon, Mar 1, 2021 at 9:06 PM Tianjia Zhang
> >> <tianjia.zhang@...ux.alibaba.com> wrote:
> >>>
> >>>
> >>>
> >>> On 3/1/21 5:54 PM, Jarkko Sakkinen wrote:
> >>>> On Mon, Mar 01, 2021 at 01:18:36PM +0800, Tianjia Zhang wrote:
> >>>>> q2 is not always 384-byte length. Sometimes it only has 383-byte.
> >>>>
> >>>> What does determine this?
> >>>>
> >>>>> In this case, the valid portion of q2 is reordered reversely for
> >>>>> little endian order, and the remaining portion is filled with zero.
> >>>>
> >>>> I'm presuming that you want to say "In this case, q2 needs to be reversed because...".
> >>>>
> >>>> I'm lacking these details:
> >>>>
> >>>> 1. Why the length of Q2 can vary?
> >>>> 2. Why reversing the bytes is the correct measure to counter-measure
> >>>>     this variation?
> >>>>
> >>>> /Jarkko
> >>>>
> >>>
> >>> When use openssl to generate a key instead of using the built-in
> >>> sign_key.pem, there is a probability that will encounter this problem.
> >>>
> >>> Here is a problematic key I encountered. The calculated q1 and q2 of
> >>> this key are both 383 bytes, If the length is not processed, the
> >>> hardware signature will fail.
> >>
> >> Presumably the issue is that some keys have parameters that have
> >> enough leading 0 bits to be effectively shorter.  The openssl API
> >> (and, sadly, a bunch  of the ASN.1 stuff) treats these parameters as
> >> variable-size integers.
> > 
> > But the test uses a static key. It used to generate a key on fly but
> 
> IMO even though the test code, it comes from the linux kernel, meaning
> that its quality has a certain guarantee and it is a good reference, so
> the test code still needs to ensure its correctness.

Hmm... what is working incorrectly then?

/Jarkko