[PATCH v3] Seed random generator in main()

Robin McCorkell rmccorkell at karoshi.org.uk
Wed Jun 17 12:33:29 MDT 2015


On 17/06/2015 3:58 PM, Simo wrote:
> On Wed, 2015-06-17 at 15:52 +0200, Volker Lendecke wrote:
>> On Wed, Jun 17, 2015 at 09:49:31AM -0400, Simo wrote:
>>> krb5 runs on all platforms and uses cryptographically secure PRNGs
>>> (urandom on Linux), perhaps we can use that libraries for random number
>>> generation.
>> Ah, ok. "using urandom" means going through Kerberos, right?
> Well for me it meant "not using our own PRNG", so yeah we can use krb5
> or openssl or what you have, as long as we use something that is vetted
> an updated by people that know what they are doing and consider good
> random number generation as one of their top priorities.
>
> Simo.
>

Relevant thread discussed on the list a while back:
https://lists.samba.org/archive/samba-technical/2014-May/099731.html

Do we really want to use cryptographically secure random generation for
even simple tasks like shuffling responses? Besides, this discussion
hides a real problem: at the moment, shuffling (of DFS referrals and DFS
DC referrals at the moment) is poor, since the RNG gets seeded every
time the shuffle function is called, and is seeded with the current
time. This makes it so that queries made in the same second will have
the same shuffling of responses. This patch fixes that, and the
technique is already used in nmbd so it is just becoming more consistent.

As for long-term crypto needs: my vote, however insignificant, goes to
using the krb5 libraries. It's just a shame the API isn't quite the same
for both Heimdal and MIT.

Robin

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