Date: Thu, 24 Dec 2009 15:45:15 +0300 From: Paul Graphov <graphov@gmail.com> To: freebsd-hackers@freebsd.org Subject: yarrow random generator Message-ID: <5a5b03660912240445x7df1498dt42e29d93105efebc@mail.gmail.com>
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Hello guys,
I've looked at FreeBSD 8.0 cryptographically secure pseudorandom
numbers generator and have a question. It looks like a bug but I'am
not sure.
In file sys/dev/randomdev.c, function random_read:
if (!random_systat.seeded)
error = (*random_systat.block)(flag);
It blocks until PRNG is seeded. For software random generator implementation
block method looks as follows, sys/dev/randomdev_soft.c:
random_yarrow_block(int flag)
{
int error = 0;
mtx_lock(&random_reseed_mtx);
/* Blocking logic */
while (random_systat.seeded && !error) {
if (flag & O_NONBLOCK)
error = EWOULDBLOCK;
else {
printf("Entropy device is blocking.\n");
error = msleep(&random_systat,
&random_reseed_mtx,
PUSER | PCATCH, "block", 0);
}
}
mtx_unlock(&random_reseed_mtx);
return error;
}
It seems that random_systat.seeded in "while" condition should be negated.
Or it will never block actually, or block erroneously until next reseed
(under very rare
conditions)
Am I right?
Thanks.
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