On 18 July 2018 at 03:17, Michael Paquier <michael@paquier.xyz> wrote:
>> [1] https://wiki.openssl.org/index.php/Random_Numbers
>
> This quote from the wiki is scary so that's not quite clean either for
> Windows:
> "Be careful when deferring to RAND_poll on some Unix systems because it
> does not seed the generator. See the code guarded with
> OPENSSL_SYS_VXWORKS in rand_unix.c. Additionally, RAND_poll can have
> negative interactions on newer Windows platforms, so your program could
> hang or crash depending on the potential issue. See Windows Issues
> below."
>
I think that wiki page is somewhat out of date in places. Both the
Windows issues it links to seem to have been fixed a long time ago, so
I think using RAND_poll() is probably safe now, although perhaps there
are still some Unix platforms on which it won't help either.
>> [2] https://github.com/benvanik/openssl/blob/master/openssl/crypto/rand/md_rand.c
>
> This repository is outdated, on OpenSSL HEAD I am seeing this used only
> in rand_win.c. And this commit is sort of interesting because there was
> a retry loop done with RAND_poll(). Please see this one:
> commit: c16de9d8329d41a2433d0f273c080d9d06ad7a87
> author: Dr. Matthias St. Pierre <Matthias.St.Pierre@ncp-e.com>
> date: Thu, 31 Aug 2017 23:16:22 +0200
> committer: Ben Kaduk <kaduk@mit.edu>
> date: Wed, 18 Oct 2017 08:39:20 -0500
> Fix reseeding issues of the public RAND_DRBG
>
> apps/ocsp.c also has the wisdom to check for a failure on RAND_poll().
OK, I guess that it is possible that an older version of OpenSSL
requires RAND_poll() to be called multiple times. Here's an updated
patch doing that (with up to 8 retries, based on the old OpenSSL
code).
Regards,
Dean