From: Michael Brown <mcb30@ipxe.org>
Date: Thu, 9 Jun 2016 07:39:25 +0000 (+0100)
Subject: [libc] Always use a non-zero seed for the (non-crypto) RNG
X-Git-Tag: v1.20.1~432
X-Git-Url: http://git.ipfire.org/cgi-bin/gitweb.cgi?a=commitdiff_plain;h=2c197517f2a82970ab6866e197f06a3099418324;p=thirdparty%2Fipxe.git

[libc] Always use a non-zero seed for the (non-crypto) RNG

The non-cryptographic RNG implemented by random() has the property
that a seed value of zero will result in a generated sequence of
all-zero values.  This situation can arise if currticks() returns zero
at start of day.

Work around this problem by falling back to a fixed non-zero seed if
necessary.

This has no effect on the separate DRBG used by cryptographic code.

Signed-off-by: Michael Brown <mcb30@ipxe.org>
---

diff --git a/src/core/random.c b/src/core/random.c
index a74175a79..975a03cf5 100644
--- a/src/core/random.c
+++ b/src/core/random.c
@@ -18,6 +18,8 @@ static int32_t rnd_seed = 0;
  */
 void srandom ( unsigned int seed ) {
 	rnd_seed = seed;
+	if ( ! rnd_seed )
+		rnd_seed = 4; /* Chosen by fair dice roll */
 }
 
 /**