/*
- * 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: src/lib/libc/gen/arc4random.c,v 1.25 2008/09/09 09:46:36 ache Exp $");
#include "namespace.h"
#include <sys/types.h>
u_int8_t s[256];
};
-static pthread_mutex_t arc4random_mtx = PTHREAD_MUTEX_INITIALIZER;
+static int lock = 0;
+extern void spin_lock(int*);
+extern void spin_unlock(int*);
-#define RANDOMDEV "/dev/urandom"
+#define RANDOMDEV "/dev/random"
+#define KEYSIZE 128
#define THREAD_LOCK() \
do { \
if (__isthreaded) \
- _pthread_mutex_lock(&arc4random_mtx); \
+ spin_lock(&lock); \
} while (0)
#define THREAD_UNLOCK() \
do { \
if (__isthreaded) \
- _pthread_mutex_unlock(&arc4random_mtx); \
+ spin_unlock(&lock); \
} while (0)
-static struct arc4_stream rs;
+static struct arc4_stream rs = {
+ .i = 0,
+ .j = 0,
+ .s = {
+ 0, 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15,
+ 16, 17, 18, 19, 20, 21, 22, 23, 24, 25, 26, 27, 28, 29, 30, 31,
+ 32, 33, 34, 35, 36, 37, 38, 39, 40, 41, 42, 43, 44, 45, 46, 47,
+ 48, 49, 50, 51, 52, 53, 54, 55, 56, 57, 58, 59, 60, 61, 62, 63,
+ 64, 65, 66, 67, 68, 69, 70, 71, 72, 73, 74, 75, 76, 77, 78, 79,
+ 80, 81, 82, 83, 84, 85, 86, 87, 88, 89, 90, 91, 92, 93, 94, 95,
+ 96, 97, 98, 99, 100, 101, 102, 103, 104, 105, 106, 107, 108, 109, 110, 111,
+ 112, 113, 114, 115, 116, 117, 118, 119, 120, 121, 122, 123, 124, 125, 126, 127,
+ 128, 129, 130, 131, 132, 133, 134, 135, 136, 137, 138, 139, 140, 141, 142, 143,
+ 144, 145, 146, 147, 148, 149, 150, 151, 152, 153, 154, 155, 156, 157, 158, 159,
+ 160, 161, 162, 163, 164, 165, 166, 167, 168, 169, 170, 171, 172, 173, 174, 175,
+ 176, 177, 178, 179, 180, 181, 182, 183, 184, 185, 186, 187, 188, 189, 190, 191,
+ 192, 193, 194, 195, 196, 197, 198, 199, 200, 201, 202, 203, 204, 205, 206, 207,
+ 208, 209, 210, 211, 212, 213, 214, 215, 216, 217, 218, 219, 220, 221, 222, 223,
+ 224, 225, 226, 227, 228, 229, 230, 231, 232, 233, 234, 235, 236, 237, 238, 239,
+ 240, 241, 242, 243, 244, 245, 246, 247, 248, 249, 250, 251, 252, 253, 254, 255
+ }
+};
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(as)
- struct arc4_stream *as;
-{
- int n;
-
- for (n = 0; n < 256; n++)
- as->s[n] = n;
- as->i = 0;
- as->j = 0;
-}
+static struct {
+ struct timeval tv;
+ pid_t pid;
+ u_int8_t rnd[KEYSIZE];
+} rdat;
+static volatile int rs_data_available = 0;
static inline void
-arc4_addrandom(as, dat, datlen)
- 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(as)
- struct arc4_stream *as;
+arc4_fetch(void)
{
- int fd, n;
- struct {
- struct timeval tv;
- pid_t pid;
- u_int8_t rnd[128 - sizeof(struct timeval) - sizeof(pid_t)];
- } rdat;
-
- gettimeofday(&rdat.tv, NULL);
- rdat.pid = getpid();
+ int done, fd;
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));
+static void
+arc4_stir(void)
+{
+ int n;
+ /*
+ * If we don't have data, we need some now before we can integrate
+ * it into the static buffers
+ */
+ if (!rs_data_available)
+ {
+ arc4_fetch();
+ }
+ rs_data_available = 0;
+ __sync_synchronize();
+
+ 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;
+ rs_stired = 1;
}
static inline u_int8_t
-arc4_getbyte(as)
- 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(as)
- 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);
}
-static void
-arc4_check_init(void)
+/* 7944700: force restir in child */
+__private_extern__ void
+_arc4_fork_child(void)
{
- if (!rs_initialized) {
- arc4_init(&rs);
- rs_initialized = 1;
- }
+ rs_stired = 0;
+ rs_data_available = 0;
}
-static void
+static inline int
arc4_check_stir(void)
{
- if (!rs_stired) {
- arc4_stir(&rs);
- rs_stired = 1;
+ if (!rs_stired || arc4_count <= 0) {
+ arc4_stir();
+ return 1;
}
+ return 0;
}
void
-arc4random_stir()
+arc4random_stir(void)
{
THREAD_LOCK();
- arc4_check_init();
- arc4_stir(&rs);
+ arc4_stir();
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);
+
+ int did_stir = arc4_check_stir();
+ rnd = arc4_getword();
+ arc4_count -= 4;
+
THREAD_UNLOCK();
+ if (did_stir)
+ {
+ /* stirring used up our data pool, we need to read in new data outside of the lock */
+ arc4_fetch();
+ rs_data_available = 1;
+ __sync_synchronize();
+ }
return (rnd);
}
+void
+arc4random_buf(void *_buf, size_t n)
+{
+ u_char *buf = (u_char *)_buf;
+ int did_stir = 0;
+
+ THREAD_LOCK();
+
+ while (n--) {
+ if (arc4_check_stir())
+ {
+ did_stir = 1;
+ }
+ buf[n] = arc4_getbyte();
+ arc4_count--;
+ }
+
+ THREAD_UNLOCK();
+ if (did_stir)
+ {
+ /* stirring used up our data pool, we need to read in new data outside of the lock */
+ arc4_fetch();
+ rs_data_available = 1;
+ __sync_synchronize();
+ }
+}
+
+/*
+ * 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>
projects / apple / libc.git / blobdiff