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/*
* Copyright (c) 1999,2000,2004 Damien Miller <djm@mindrot.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 "includes.h"
#include <sys/types.h>
#include <string.h>
#include <stdarg.h>
#include "log.h"
#ifndef HAVE_ARC4RANDOM
#include <openssl/rand.h>
#include <openssl/rc4.h>
#include <openssl/err.h>
/* Size of key to use */
#define SEED_SIZE 20
/* Number of bytes to reseed after */
#define REKEY_BYTES (1 << 24)
static int rc4_ready = 0;
static RC4_KEY rc4;
unsigned int
arc4random(void)
{
unsigned int r = 0;
static int first_time = 1;
if (rc4_ready <= 0) {
if (first_time)
seed_rng();
first_time = 0;
arc4random_stir();
}
RC4(&rc4, sizeof(r), (unsigned char *)&r, (unsigned char *)&r);
rc4_ready -= sizeof(r);
return(r);
}
void
arc4random_stir(void)
{
unsigned char rand_buf[SEED_SIZE];
int i;
memset(&rc4, 0, sizeof(rc4));
if (RAND_bytes(rand_buf, sizeof(rand_buf)) <= 0)
fatal("Couldn't obtain random bytes (error %ld)",
ERR_get_error());
RC4_set_key(&rc4, sizeof(rand_buf), rand_buf);
/*
* Discard early keystream, as per recommendations in:
* http://www.wisdom.weizmann.ac.il/~itsik/RC4/Papers/Rc4_ksa.ps
*/
for(i = 0; i <= 256; i += sizeof(rand_buf))
RC4(&rc4, sizeof(rand_buf), rand_buf, rand_buf);
memset(rand_buf, 0, sizeof(rand_buf));
rc4_ready = REKEY_BYTES;
}
#endif /* !HAVE_ARC4RANDOM */
#ifndef ARC4RANDOM_BUF
void
arc4random_buf(void *_buf, size_t n)
{
size_t i;
u_int32_t r;
char *buf = (char *)_buf;
for (i = 0; i < n; i++) {
if (i % 4 == 0)
r = arc4random();
buf[i] = r & 0xff;
r >>= 8;
}
i = r = 0;
}
#endif /* !HAVE_ARC4RANDOM_BUF */
#ifndef ARC4RANDOM_UNIFORM
/*
* 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;
}
#endif /* !HAVE_ARC4RANDOM_UNIFORM */
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