Replace 'arc4random() % range' by 'arc4random_uniform(range)'.

Do this by introducing atcrandom_uniform(range) which returns
deterministic randomness or good randomness depending on whether
a seed was specified with the -r option.

Diff by Matthew Martin, reviewed by deraadt@ and me.

ok deraadt@

1 files changed, 14 insertions, 5 deletions

diff --git a/games/atc/update.c b/games/atc/update.c
index 36cf824bd27..0f172c5d737 100644
--- a/games/atc/update.c
+++ b/games/atc/update.c
@@ -1,4 +1,4 @@
-/*	$OpenBSD: update.c,v 1.16 2014/12/09 05:01:14 deraadt Exp $	*/
+/*	$OpenBSD: update.c,v 1.17 2015/12/15 18:39:50 tb Exp $	*/
 
 /*-
  * Copyright (c) 1990, 1993
@@ -59,6 +59,15 @@ atcrandom()
 		return arc4random();
 }
 
+uint32_t
+atcrandom_uniform(uint32_t upper_bound)
+{
+	if (seeded)
+		return random() % upper_bound;
+	else
+		return arc4random_uniform(upper_bound);
+}
+
 void
 update(int dummy)
 {
@@ -212,7 +221,7 @@ update(int dummy)
 	 * Otherwise, prop jobs show up *on* entrance.  Remember that
 	 * we don't update props on odd updates.
 	 */
-	if ((atcrandom() % sp->newplane_time) == 0)
+	if (atcrandom_uniform(sp->newplane_time) == 0)
 		addplane();
 }
 
@@ -308,10 +317,10 @@ addplane(void)
 	memset(&p, 0, sizeof (p));
 
 	p.status = S_MARKED;
-	p.plane_type = atcrandom() % 2;
+	p.plane_type = atcrandom_uniform(2);
 
 	num_starts = sp->num_exits + sp->num_airports;
-	rnd = atcrandom() % num_starts;
+	rnd = atcrandom_uniform(num_starts);
 
 	if (rnd < sp->num_exits) {
 		p.dest_type = T_EXIT;
@@ -324,7 +333,7 @@ addplane(void)
 	/* loop until we get a plane not near another */
 	for (i = 0; i < num_starts; i++) {
 		/* loop till we get a different start point */
-		while ((rnd2 = atcrandom() % num_starts) == rnd)
+		while ((rnd2 = atcrandom_uniform(num_starts)) == rnd)
 			;
 		if (rnd2 < sp->num_exits) {
 			p.orig_type = T_EXIT;