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

[Dmitry Belyavsky]

Hello,

I can confirm that I have seen a similar behavior in multi-thread
environment. Unfortunately, I do not have a script to reproduce it either.

On Fri, May 20, 2016 at 6:49 PM, Mick Saxton via RT <rt at openssl.org> 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 (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 (j -k) must not be
> negative
>
>
> I do have a test program which can reproduce this behaviour.
>
> If I can be of further help - please contact me by email.
>
> Regards
> Mick Saxton
>
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-- 
SY, Dmitry Belyavsky
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