Module Name: src
Committed By: christos
Date: Fri Feb 4 22:07:08 UTC 2011
Modified Files:
src/include: stdlib.h
src/lib/libc/gen: arc4random.3 arc4random.c
Log Message:
add arc4random_{buf,uniform}, from OpenBSD.
To generate a diff of this commit:
cvs rdiff -u -r1.94 -r1.95 src/include/stdlib.h
cvs rdiff -u -r1.7 -r1.8 src/lib/libc/gen/arc4random.3
cvs rdiff -u -r1.9 -r1.10 src/lib/libc/gen/arc4random.c
Please note that diffs are not public domain; they are subject to the
copyright notices on the relevant files.
Modified files:
Index: src/include/stdlib.h
diff -u src/include/stdlib.h:1.94 src/include/stdlib.h:1.95
--- src/include/stdlib.h:1.94 Wed Dec 22 14:47:56 2010
+++ src/include/stdlib.h Fri Feb 4 17:07:07 2011
@@ -1,4 +1,4 @@
-/* $NetBSD: stdlib.h,v 1.94 2010/12/22 19:47:56 jruoho Exp $ */
+/* $NetBSD: stdlib.h,v 1.95 2011/02/04 22:07:07 christos Exp $ */
/*-
* Copyright (c) 1990, 1993
@@ -250,6 +250,8 @@
uint32_t arc4random(void);
void arc4random_stir(void);
+void arc4random_buf(void *, size_t);
+uint32_t arc4random_uniform(uint32_t);
void arc4random_addrandom(u_char *, int);
char *getbsize(int *, long *);
char *cgetcap(char *, const char *, int);
Index: src/lib/libc/gen/arc4random.3
diff -u src/lib/libc/gen/arc4random.3:1.7 src/lib/libc/gen/arc4random.3:1.8
--- src/lib/libc/gen/arc4random.3:1.7 Mon Dec 26 14:40:14 2005
+++ src/lib/libc/gen/arc4random.3 Fri Feb 4 17:07:07 2011
@@ -1,4 +1,4 @@
-.\" $NetBSD: arc4random.3,v 1.7 2005/12/26 19:40:14 perry Exp $
+.\" $NetBSD: arc4random.3,v 1.8 2011/02/04 22:07:07 christos Exp $
.\" $OpenBSD: arc4random.3,v 1.17 2000/12/21 14:07:41 aaron Exp $
.\"
.\" Copyright 1997 Niels Provos <pro...@physnet.uni-hamburg.de>
@@ -31,11 +31,13 @@
.\"
.\" Manual page, using -mandoc macros
.\"
-.Dd April 15, 1997
+.Dd February 4, 2011
.Dt ARC4RANDOM 3
.Os
.Sh NAME
.Nm arc4random ,
+.Nm arc4random_buf ,
+.Nm arc4random_uniform ,
.Nm arc4random_stir ,
.Nm arc4random_addrandom
.Nd arc4 random number generator
@@ -46,6 +48,10 @@
.Ft uint32_t
.Fn arc4random "void"
.Ft void
+.Fn arc4random_buf "void *buffer" "size_t length"
+.Ft uint32_t
+.Fn arc4random_uniform "uint32_t upper_bound"
+.Ft void
.Fn arc4random_stir "void"
.Ft void
.Fn arc4random_addrandom "u_char *dat" "int datlen"
@@ -76,6 +82,20 @@
and
.Xr drand48 3 .
.Pp
+The
+.Fn arc4random_buf
+function fills the
+.Fa buffer
+with
+.Fa length
+bytes of ARC4-derived random data.
+.Pp
+The
+.Fn arc4random_uniform
+function returns a uniformly distributed random number less than
+.Fa upper_bound
+avoiding modulo bias when the upper bound is not a power of two.
+.Pp
The
.Fn arc4random_stir
function reads data from
Index: src/lib/libc/gen/arc4random.c
diff -u src/lib/libc/gen/arc4random.c:1.9 src/lib/libc/gen/arc4random.c:1.10
--- src/lib/libc/gen/arc4random.c:1.9 Sat Dec 24 16:11:16 2005
+++ src/lib/libc/gen/arc4random.c Fri Feb 4 17:07:07 2011
@@ -1,4 +1,4 @@
-/* $NetBSD: arc4random.c,v 1.9 2005/12/24 21:11:16 perry Exp $ */
+/* $NetBSD: arc4random.c,v 1.10 2011/02/04 22:07:07 christos Exp $ */
/* $OpenBSD: arc4random.c,v 1.6 2001/06/05 05:05:38 pvalchev Exp $ */
/*
@@ -27,7 +27,7 @@
#include <sys/cdefs.h>
#if defined(LIBC_SCCS) && !defined(lint)
-__RCSID("$NetBSD: arc4random.c,v 1.9 2005/12/24 21:11:16 perry Exp $");
+__RCSID("$NetBSD: arc4random.c,v 1.10 2011/02/04 22:07:07 christos Exp $");
#endif /* LIBC_SCCS and not lint */
#include "namespace.h"
@@ -44,9 +44,9 @@
#endif
struct arc4_stream {
- u_int8_t i;
- u_int8_t j;
- u_int8_t s[256];
+ uint8_t i;
+ uint8_t j;
+ uint8_t s[256];
};
static int rs_initialized;
@@ -55,12 +55,11 @@
static inline void arc4_init(struct arc4_stream *);
static inline void arc4_addrandom(struct arc4_stream *, u_char *, int);
static void arc4_stir(struct arc4_stream *);
-static inline u_int8_t arc4_getbyte(struct arc4_stream *);
-static inline u_int32_t arc4_getword(struct arc4_stream *);
+static inline uint8_t arc4_getbyte(struct arc4_stream *);
+static inline uint32_t arc4_getword(struct arc4_stream *);
static inline void
-arc4_init(as)
- struct arc4_stream *as;
+arc4_init(struct arc4_stream *as)
{
int n;
@@ -71,13 +70,10 @@
}
static inline void
-arc4_addrandom(as, dat, datlen)
- struct arc4_stream *as;
- u_char *dat;
- int datlen;
+arc4_addrandom(struct arc4_stream *as, u_char *dat, int datlen)
{
int n;
- u_int8_t si;
+ uint8_t si;
as->i--;
for (n = 0; n < 256; n++) {
@@ -91,8 +87,7 @@
}
static void
-arc4_stir(as)
- struct arc4_stream *as;
+arc4_stir(struct arc4_stream *as)
{
int fd;
struct {
@@ -140,11 +135,10 @@
arc4_getbyte(as);
}
-static inline u_int8_t
-arc4_getbyte(as)
- struct arc4_stream *as;
+static inline uint8_t
+arc4_getbyte(struct arc4_stream *as)
{
- u_int8_t si, sj;
+ uint8_t si, sj;
as->i = (as->i + 1);
si = as->s[as->i];
@@ -155,11 +149,10 @@
return (as->s[(si + sj) & 0xff]);
}
-static inline u_int32_t
-arc4_getword(as)
- struct arc4_stream *as;
+static inline uint32_t
+arc4_getword(struct arc4_stream *as)
{
- u_int32_t val;
+ uint32_t val;
val = arc4_getbyte(as) << 24;
val |= arc4_getbyte(as) << 16;
val |= arc4_getbyte(as) << 8;
@@ -168,7 +161,7 @@
}
void
-arc4random_stir()
+arc4random_stir(void)
{
if (!rs_initialized) {
arc4_init(&rs);
@@ -178,23 +171,89 @@
}
void
-arc4random_addrandom(dat, datlen)
- u_char *dat;
- int datlen;
+arc4random_addrandom(u_char *dat, int datlen)
{
if (!rs_initialized)
arc4random_stir();
arc4_addrandom(&rs, dat, datlen);
}
-u_int32_t
-arc4random()
+uint32_t
+arc4random(void)
{
if (!rs_initialized)
arc4random_stir();
return arc4_getword(&rs);
}
+void
+arc4random_buf(void *buf, size_t len)
+{
+ uint8_t *bp = buf;
+ uint8_t *ep = bp + len;
+
+ bp[0] = arc4_getbyte(&rs) % 3;
+ while (bp[0]--)
+ (void)arc4_getbyte(&rs);
+
+ while (bp < ep)
+ *bp++ = arc4_getbyte(&rs);
+}
+
+/*-
+ * Written by Damien Miller.
+ * With simplifications by Jinmei Tatuya.
+ */
+
+/*
+ * 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 the range
+ * [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;
+
+#if defined(ULONG_MAX) && (ULONG_MAX > 0xFFFFFFFFUL)
+ min = 0x100000000UL % upper_bound;
+#else
+ /* calculate (2^32 % upper_bound) avoiding 64-bit math */
+ if (upper_bound > 0x80000000U)
+ /* 2^32 - upper_bound (only one "value area") */
+ min = 1 + ~upper_bound;
+ else
+ /* ((2^32 - x) % x) == (2^32 % x) when x <= 2^31 */
+ min = (0xFFFFFFFFU - upper_bound + 1) % upper_bound;
+#endif
+
+ /*
+ * 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 (at all).
+ */
+ if (!rs_initialized)
+ arc4random_stir();
+ if (arc4_getbyte(&rs) & 1)
+ (void)arc4_getbyte(&rs);
+ do
+ r = arc4_getword(&rs);
+ while (r < min);
+
+ return r % upper_bound;
+}
+
+
#if 0
/*-------- Test code for i386 --------*/
#include <stdio.h>
