[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>
ipxe · Jun 9, 2016 · 2c19751 · 2c19751
1 parent f6e8b80
commit 2c19751
Showing 1 changed file with 2 additions and 0 deletions.
diff --git 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 */
 }
 
 /**