Re: [PATCH] selftests/sgx: fix EINIT failure dueto SGX_INVALID_SIGNATURE

[Tianjia Zhang]

On 3/2/21 1:54 PM, Andy Lutomirski wrote:
> On Mon, Mar 1, 2021 at 9:06 PM Tianjia Zhang
> <tianjia.zhang@xxxxxxxxxxxxxxxxx> 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.

I agree with your opinion.

Thanks,
Tianjia