[openssl-dev] [openssl.org #4545] Crash in crypto/rand/md_rand.c

[Mick Saxton via RT]

Hi Matt

The test program runs against our major new development so I cannot share it as is.

I will try to produce a skeleton version which I could let you have.

-          But that will be end if next week as I am away for a few days

-          That is providing that exhibits the bug.

Mick


From: Matt Caswell via RT [mailto:rt at openssl.org]
Sent: 27 May 2016 10:46
To: Mick Saxton
Cc: openssl-dev at openssl.org
Subject: [openssl.org #4545] Crash in crypto/rand/md_rand.c

On Fri May 20 15:49:49 2016, micks at 1e.com<mailto:micks at 1e.com> wrote:
> Hi
>
> Before going any further I would like to state that I have only seen
> this problem when we have 10000 or more concurrent connections.
>
> Mostly we notice it on Windows but I have seen it on linux (Ubuntu).
>
> I first noticed it when using v1.0.2d but have seen it again since
> upgrading to v1.0.2h.
>
> It can happen in one of two places and results in a call to MD_Update
> with a negative value.
>
> I have come up with a temporary fix which avoids the possibility of
> crashing at the expense of some randomness.
> The system is very highly stressed at this point so debugging further
> is difficult.
>
> The fix I am using is probably not what you eventually will want to
> implement but it does improve stability.
>
> 273: MD_Update(&m, &(state[st_idx]), (j - k) );
> Change to
> 273: MD_Update(&m, &(state[st_idx]), (j - k) > 0 ? j - k :
> 1); // micks at 1e.com<mailto:micks at 1e.com> (j -k) must not be negative
>
> And
>
> 495: MD_Update(&m, &(state[st_idx]), MD_DIGEST_LENGTH / 2 -
> k )
> Change to
> 495: MD_Update(&m, &(state[st_idx]), MD_DIGEST_LENGTH / 2 -
> k > 0 ? MD_DIGEST_LENGTH / 2 - k : 1); // micks at 1e.com<mailto:micks at 1e.com> (j -k) must
> not be negative
>
>
> I do have a test program which can reproduce this behaviour.

Hi Mick

Are you able to share your test program?

Thanks

Matt

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