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

src/lib/libc/crypt/Makefile.inc

@@ -1,8 +1,9 @@
-#	$OpenBSD: Makefile.inc,v 1.21 2014/05/16 22:11:00 jmc Exp $
+#	$OpenBSD: Makefile.inc,v 1.22 2014/07/12 13:24:54 deraadt Exp $
 
 .PATH: ${LIBCSRCDIR}/arch/${MACHINE_CPU}/crypt ${LIBCSRCDIR}/crypt
 
-SRCS+=	crypt.c crypt2.c cryptutil.c arc4random.c blowfish.c bcrypt.c
+SRCS+=	crypt.c crypt2.c cryptutil.c arc4random.c arc4random_uniform.c \
+	blowfish.c bcrypt.c
 
 MAN+=	crypt.3 blowfish.3 arc4random.3
 MLINKS+=crypt.3 setkey.3 crypt.3 crypt_checkpass.3 crypt.3 encrypt.3

src/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;
-}

src/lib/libc/crypt/arc4random_uniform.c

@@ -0,0 +1,56 @@
+/*	$OpenBSD: arc4random_uniform.c,v 1.1 2014/07/12 13:24:54 deraadt Exp $	*/
+
+/*
+ * Copyright (c) 2008, Damien Miller <djm@openbsd.org>
+ *
+ * Permission to use, copy, modify, and distribute this software for any
+ * purpose with or without fee is hereby granted, provided that the above
+ * copyright notice and this permission notice appear in all copies.
+ *
+ * THE SOFTWARE IS PROVIDED "AS IS" AND THE AUTHOR DISCLAIMS ALL WARRANTIES
+ * WITH REGARD TO THIS SOFTWARE INCLUDING ALL IMPLIED WARRANTIES OF
+ * MERCHANTABILITY AND FITNESS. IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR
+ * ANY SPECIAL, DIRECT, INDIRECT, OR CONSEQUENTIAL DAMAGES OR ANY DAMAGES
+ * WHATSOEVER RESULTING FROM LOSS OF USE, DATA OR PROFITS, WHETHER IN AN
+ * ACTION OF CONTRACT, NEGLIGENCE OR OTHER TORTIOUS ACTION, ARISING OUT OF
+ * OR IN CONNECTION WITH THE USE OR PERFORMANCE OF THIS SOFTWARE.
+ */
+
+#include <sys/types.h>
+#include <stdlib.h>
+
+/*
+ * 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;
+}