/*
- * Arc4 random number generator for OpenBSD.
- * Copyright 1996 David Mazieres <dm@lcs.mit.edu>.
+ * Copyright (c) 1996, David Mazieres <dm@uun.org>
+ * 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.
*
- * Modification and redistribution in source and binary forms is
- * permitted provided that due credit is given to the author and the
- * OpenBSD project (for instance by leaving this copyright notice
- * intact).
+ * 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.
*/
/*
+ * Arc4 random number generator for OpenBSD.
+ *
* This code is derived from section 17.1 of Applied Cryptography,
* second edition, which describes a stream cipher allegedly
* compatible with RSA Labs "RC4" cipher (the actual description of
*/
#include <sys/cdefs.h>
-__FBSDID("$FreeBSD: src/lib/libc/gen/arc4random.c,v 1.10 2004/03/24 14:44:57 green Exp $");
+__FBSDID("$FreeBSD$");
#include <sys/types.h>
#include <sys/time.h>
};
#define RANDOMDEV "/dev/urandom"
+#define KEYSIZE 128
+
#ifdef __REENTRANT
static pthread_mutex_t arc4random_mtx = PTHREAD_MUTEX_INITIALIZER;
#define THREAD_LOCK() pthread_mutex_lock(&arc4random_mtx)
static struct arc4_stream rs;
static int rs_initialized;
static int rs_stired;
+static int arc4_count;
-static inline u_int8_t arc4_getbyte(struct arc4_stream *);
-static void arc4_stir(struct arc4_stream *);
+static inline u_int8_t arc4_getbyte(void);
+static void arc4_stir(void);
static inline void
-arc4_init(struct arc4_stream *as)
+arc4_init(void)
{
int n;
for (n = 0; n < 256; n++)
- as->s[n] = n;
- as->i = 0;
- as->j = 0;
+ rs.s[n] = n;
+ rs.i = 0;
+ rs.j = 0;
}
static inline void
-arc4_addrandom(struct arc4_stream *as, u_char *dat, int datlen)
+arc4_addrandom(u_char *dat, int datlen)
{
int n;
u_int8_t si;
- as->i--;
+ rs.i--;
for (n = 0; n < 256; n++) {
- as->i = (as->i + 1);
- si = as->s[as->i];
- as->j = (as->j + si + dat[n % datlen]);
- as->s[as->i] = as->s[as->j];
- as->s[as->j] = si;
+ rs.i = (rs.i + 1);
+ si = rs.s[rs.i];
+ rs.j = (rs.j + si + dat[n % datlen]);
+ rs.s[rs.i] = rs.s[rs.j];
+ rs.s[rs.j] = si;
}
+ rs.j = rs.i;
}
static void
-arc4_stir(struct arc4_stream *as)
+arc4_stir(void)
{
- int fd, n;
+ int done, fd, n;
struct {
- struct timeval tv;
- pid_t pid;
- u_int8_t rnd[128 - sizeof(struct timeval) - sizeof(pid_t)];
- } rdat;
+ struct timeval tv;
+ pid_t pid;
+ u_int8_t rnd[KEYSIZE];
+ } rdat;
- gettimeofday(&rdat.tv, NULL);
- rdat.pid = getpid();
fd = open(RANDOMDEV, O_RDONLY, 0);
+ done = 0;
if (fd >= 0) {
- (void) read(fd, rdat.rnd, sizeof(rdat.rnd));
- close(fd);
+ if (read(fd, &rdat, KEYSIZE) == KEYSIZE)
+ done = 1;
+ (void)close(fd);
}
- /* fd < 0? Ah, what the heck. We'll just take whatever was on the
- * stack... */
+ if (!done) {
+ (void)gettimeofday(&rdat.tv, NULL);
+ rdat.pid = getpid();
+ /* We'll just take whatever was on the stack too... */
+ }
- arc4_addrandom(as, (void *) &rdat, sizeof(rdat));
+ arc4_addrandom((u_char *)&rdat, KEYSIZE);
/*
* Throw away the first N bytes of output, as suggested in the
* by Ilya Mironov.
*/
for (n = 0; n < 1024; n++)
- arc4_getbyte(as);
+ (void) arc4_getbyte();
+ arc4_count = 1600000;
}
static inline u_int8_t
-arc4_getbyte(struct arc4_stream *as)
+arc4_getbyte(void)
{
u_int8_t si, sj;
- as->i = (as->i + 1);
- si = as->s[as->i];
- as->j = (as->j + si);
- sj = as->s[as->j];
- as->s[as->i] = sj;
- as->s[as->j] = si;
+ rs.i = (rs.i + 1);
+ si = rs.s[rs.i];
+ rs.j = (rs.j + si);
+ sj = rs.s[rs.j];
+ rs.s[rs.i] = sj;
+ rs.s[rs.j] = si;
- return (as->s[(si + sj) & 0xff]);
+ return (rs.s[(si + sj) & 0xff]);
}
static inline u_int32_t
-arc4_getword(struct arc4_stream *as)
+arc4_getword(void)
{
u_int32_t val;
- val = arc4_getbyte(as) << 24;
- val |= arc4_getbyte(as) << 16;
- val |= arc4_getbyte(as) << 8;
- val |= arc4_getbyte(as);
+ val = arc4_getbyte() << 24;
+ val |= arc4_getbyte() << 16;
+ val |= arc4_getbyte() << 8;
+ val |= arc4_getbyte();
return (val);
}
arc4_check_init(void)
{
if (!rs_initialized) {
- arc4_init(&rs);
+ arc4_init();
rs_initialized = 1;
}
}
-static void
+static inline void
arc4_check_stir(void)
{
- if (!rs_stired) {
- arc4_stir(&rs);
+ if (!rs_stired || arc4_count <= 0) {
+ arc4_stir();
rs_stired = 1;
}
}
void
-arc4random_stir()
+arc4random_stir(void)
{
THREAD_LOCK();
arc4_check_init();
- arc4_stir(&rs);
+ arc4_stir();
+ rs_stired = 1;
THREAD_UNLOCK();
}
void
-arc4random_addrandom(dat, datlen)
- u_char *dat;
- int datlen;
+arc4random_addrandom(u_char *dat, int datlen)
{
THREAD_LOCK();
arc4_check_init();
arc4_check_stir();
- arc4_addrandom(&rs, dat, datlen);
+ arc4_addrandom(dat, datlen);
THREAD_UNLOCK();
}
u_int32_t
-arc4random()
+arc4random(void)
{
u_int32_t rnd;
THREAD_LOCK();
arc4_check_init();
arc4_check_stir();
- rnd = arc4_getword(&rs);
+ rnd = arc4_getword();
+ arc4_count -= 4;
THREAD_UNLOCK();
return (rnd);
}
+void
+arc4random_buf(void *_buf, size_t n)
+{
+ u_char *buf = (u_char *)_buf;
+
+ THREAD_LOCK();
+ arc4_check_init();
+ while (n--) {
+ arc4_check_stir();
+ buf[n] = arc4_getbyte();
+ arc4_count--;
+ }
+ THREAD_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.
+ */
+u_int32_t
+arc4random_uniform(u_int32_t upper_bound)
+{
+ u_int32_t r, min;
+
+ if (upper_bound < 2)
+ return (0);
+
+#if (ULONG_MAX > 0xffffffffUL)
+ min = 0x100000000UL % upper_bound;
+#else
+ /* Calculate (2**32 % upper_bound) avoiding 64-bit math */
+ if (upper_bound > 0x80000000)
+ min = 1 + ~upper_bound; /* 2**32 - upper_bound */
+ else {
+ /* (2**32 - (x * 2)) % x == 2**32 % x when x <= 2**31 */
+ min = ((0xffffffff - (upper_bound * 2)) + 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.
+ */
+ for (;;) {
+ r = arc4random();
+ if (r >= min)
+ break;
+ }
+
+ return (r % upper_bound);
+}
+
#if 0
/*-------- Test code for i386 --------*/
#include <stdio.h>
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