tree 51c7f6d2268fdbefc74500e8ff36231224a52f2e
parent 5a421a8f492ae1ab74e4197af87a9f85d9ee53b3
author Willy Tarreau <w@1wt.eu> 1583517435 +0100
committer Willy Tarreau <w@1wt.eu> 1583557871 +0100
encoding latin1

BUG/MEDIUM: random: initialize the random pool a bit better

Since the UUID sample fetch was created, some people noticed that in
certain virtualized environments they manage to get exact same UUIDs
on different instances started exactly at the same moment. It turns
out that the randoms were only initialized to spread the health checks
originally, not to provide "clean" randoms.

This patch changes this and collects more randomness from various
sources, including existing randoms, /dev/urandom when available,
RAND_bytes() when OpenSSL is available, as well as the timing for such
operations, then applies a SHA1 on all this to keep a 160 bits random
seed available, 32 of which are passed to srandom().

It's worth mentioning that there's no clean way to pass more than 32
bits to srandom() as even initstate() provides an opaque state that
must absolutely not be tampered with since known implementations
contain state information.

At least this allows to have up to 4 billion different sequences
from the boot, which is not that bad.

Note that the thread safety was still not addressed, which is another
issue for another patch.

This must be backported to all versions containing the UUID sample
fetch function, i.e. as far as 2.0.