Speed and security of /dev/urandom

[Andrey Chernov]

On 19.07.2014 0:06, Steven Chamberlain wrote:
> It's been pointed out to me that OpenBSD solved that particular issue
> with MAP_INHERIT_ZERO:  the state of the arc4random PRNG is zeroed out
> on forking, and it knows to reseed then.
> 
> FreeBSD since r227520 (2011-11-15), calls getpid() on every
> arc4random_buf call, to see if the pid has changed since it seeded, and
> thus reseed.  It was shown recently (in the context of LibreSSL
> Portable) that this may not work in a contrived corner-case, so there
> they added an atfork handler, but again might not always be called.

I always say that calling getpid on every arc4random call is ugly and
should be replaced by something. pthread_atfork belong to another
library and MAP_INHERIT_ZERO is not currently implemented.

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