linux-kernel.vger.kernel.org archive mirror
 help / color / mirror / Atom feed
From: Jarkko Sakkinen <jarkko@kernel.org>
To: Shuah Khan <skhan@linuxfoundation.org>
Cc: Shuah Khan <shuah@kernel.org>,
	linux-kselftest@vger.kernel.org, linux-sgx@vger.kernel.org,
	Reinette Chatre <reinette.chatre@intel.com>,
	Borislav Petkov <bp@alien8.de>,
	Tianjia Zhang <tianjia.zhang@linux.alibaba.com>,
	Dave Hansen <dave.hansen@linux.intel.com>,
	linux-kernel@vger.kernel.org
Subject: Re: [PATCH v2] selftests/sgx: Fix Q1 and Q2 calculation in sigstruct.c
Date: Tue, 27 Jul 2021 06:12:27 +0300	[thread overview]
Message-ID: <20210727031227.tx2gqx2qg3mg4522@kernel.org> (raw)
In-Reply-To: <be6227d1-728a-c658-f962-380c28afc926@linuxfoundation.org>

On Fri, Jul 23, 2021 at 01:53:06PM -0600, Shuah Khan wrote:
> On 7/4/21 11:09 PM, Jarkko Sakkinen wrote:
> > From: Tianjia Zhang <tianjia.zhang@linux.alibaba.com>
> > 
> > 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")
> > Link: https://lore.kernel.org/linux-sgx/20210301051836.30738-1-tianjia.zhang@linux.alibaba.com/
> > Signed-off-by: Tianjia Zhang <tianjia.zhang@linux.alibaba.com>
> > Signed-off-by: Jarkko Sakkinen <jarkko@kernel.org>
> > ---
> > The original patch did a bad job explaining the code change but it
> > turned out making sense. I wrote a new description.
> > 
> > v2:
> > - Added a fixes tag.
> >   tools/testing/selftests/sgx/sigstruct.c | 41 +++++++++++++------------
> >   1 file changed, 21 insertions(+), 20 deletions(-)
> > 
> > diff --git a/tools/testing/selftests/sgx/sigstruct.c b/tools/testing/selftests/sgx/sigstruct.c
> > index dee7a3d6c5a5..92bbc5a15c39 100644
> > --- a/tools/testing/selftests/sgx/sigstruct.c
> > +++ b/tools/testing/selftests/sgx/sigstruct.c
> > @@ -55,10 +55,27 @@ static bool alloc_q1q2_ctx(const uint8_t *s, const uint8_t *m,
> >   	return true;
> >   }
> > +static void reverse_bytes(void *data, int length)
> > +{
> > +	int i = 0;
> > +	int j = length - 1;
> > +	uint8_t temp;
> > +	uint8_t *ptr = data;
> > +
> > +	while (i < j) {
> > +		temp = ptr[i];
> > +		ptr[i] = ptr[j];
> > +		ptr[j] = temp;
> > +		i++;
> > +		j--;
> > +	}
> > +}
> 
> I was just about apply this one and noticed this reverse_bytes().
> Aren't there byteswap functions you could call instead of writing
> your own?

Sorry for latency, just came from two week leave.

glibc does provide bswap for 16, 32, 64 bit numbers but nothing better.
 
I have no idea if libssl has such function. Since the test code already
uses this function, and it works, and it's not a newly added function in
this patch, I would consider keeping it.
 
> thanks,
> -- Shuah

/Jarkko

  reply	other threads:[~2021-07-27  3:12 UTC|newest]

Thread overview: 6+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2021-07-05  5:09 Jarkko Sakkinen
2021-07-05  5:10 ` Jarkko Sakkinen
2021-07-23 19:53 ` Shuah Khan
2021-07-27  3:12   ` Jarkko Sakkinen [this message]
2021-07-29 21:33     ` Shuah Khan
2021-07-30  1:03       ` Jarkko Sakkinen

Reply instructions:

You may reply publicly to this message via plain-text email
using any one of the following methods:

* Save the following mbox file, import it into your mail client,
  and reply-to-all from there: mbox

  Avoid top-posting and favor interleaved quoting:
  https://en.wikipedia.org/wiki/Posting_style#Interleaved_style

* Reply using the --to, --cc, and --in-reply-to
  switches of git-send-email(1):

  git send-email \
    --in-reply-to=20210727031227.tx2gqx2qg3mg4522@kernel.org \
    --to=jarkko@kernel.org \
    --cc=bp@alien8.de \
    --cc=dave.hansen@linux.intel.com \
    --cc=linux-kernel@vger.kernel.org \
    --cc=linux-kselftest@vger.kernel.org \
    --cc=linux-sgx@vger.kernel.org \
    --cc=reinette.chatre@intel.com \
    --cc=shuah@kernel.org \
    --cc=skhan@linuxfoundation.org \
    --cc=tianjia.zhang@linux.alibaba.com \
    --subject='Re: [PATCH v2] selftests/sgx: Fix Q1 and Q2 calculation in sigstruct.c' \
    /path/to/YOUR_REPLY

  https://kernel.org/pub/software/scm/git/docs/git-send-email.html

* If your mail client supports setting the In-Reply-To header
  via mailto: links, try the mailto: link

This is a public inbox, see mirroring instructions
for how to clone and mirror all data and code used for this inbox;
as well as URLs for NNTP newsgroup(s).