Split arc4random_uniform into it's own file, to assist other projects

now using this as upstream code.  The particular problem is systems
that contain older arc4random derivations lacking arc4random_uniform().
ok tedu miod

1 files changed, 1 insertions, 37 deletions

diff --git a/lib/libc/crypt/arc4random.c b/lib/libc/crypt/arc4random.c
index 13b94ed111e..9460af1e542 100644
--- a/lib/libc/crypt/arc4random.c
+++ b/lib/libc/crypt/arc4random.c
@@ -1,4 +1,4 @@
-/*	$OpenBSD: arc4random.c,v 1.40 2014/07/09 16:52:09 bcook Exp $	*/
+/*	$OpenBSD: arc4random.c,v 1.41 2014/07/12 13:24:54 deraadt Exp $	*/
 
 /*
  * Copyright (c) 1996, David Mazieres <dm@uun.org>
@@ -211,39 +211,3 @@ arc4random_buf(void *buf, size_t n)
 	_rs_random_buf(buf, n);
 	_ARC4_UNLOCK();
 }
-
-/*
- * Calculate a uniformly distributed random number less than upper_bound
- * avoiding "modulo bias".
- *
- * Uniformity is achieved by generating new random numbers until the one
- * returned is outside the range [0, 2**32 % upper_bound).  This
- * guarantees the selected random number will be inside
- * [2**32 % upper_bound, 2**32) which maps back to [0, upper_bound)
- * after reduction modulo upper_bound.
- */
-uint32_t
-arc4random_uniform(uint32_t upper_bound)
-{
-	uint32_t r, min;
-
-	if (upper_bound < 2)
-		return 0;
-
-	/* 2**32 % x == (2**32 - x) % x */
-	min = -upper_bound % upper_bound;
-
-	/*
-	 * This could theoretically loop forever but each retry has
-	 * p > 0.5 (worst case, usually far better) of selecting a
-	 * number inside the range we need, so it should rarely need
-	 * to re-roll.
-	 */
-	for (;;) {
-		r = arc4random();
-		if (r >= min)
-			break;
-	}
-
-	return r % upper_bound;
-}