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151 lines
3.5 KiB
C
151 lines
3.5 KiB
C
/*
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* Copyright (c) 1999,2000,2004 Damien Miller <djm@mindrot.org>
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*
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* Permission to use, copy, modify, and distribute this software for any
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* purpose with or without fee is hereby granted, provided that the above
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* copyright notice and this permission notice appear in all copies.
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*
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* THE SOFTWARE IS PROVIDED "AS IS" AND THE AUTHOR DISCLAIMS ALL WARRANTIES
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* WITH REGARD TO THIS SOFTWARE INCLUDING ALL IMPLIED WARRANTIES OF
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* MERCHANTABILITY AND FITNESS. IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR
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* ANY SPECIAL, DIRECT, INDIRECT, OR CONSEQUENTIAL DAMAGES OR ANY DAMAGES
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* WHATSOEVER RESULTING FROM LOSS OF USE, DATA OR PROFITS, WHETHER IN AN
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* ACTION OF CONTRACT, NEGLIGENCE OR OTHER TORTIOUS ACTION, ARISING OUT OF
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* OR IN CONNECTION WITH THE USE OR PERFORMANCE OF THIS SOFTWARE.
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*/
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#include "includes.h"
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#include <sys/types.h>
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#include <string.h>
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#include <stdlib.h>
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#include <stdarg.h>
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#include "log.h"
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#ifndef HAVE_ARC4RANDOM
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#include <openssl/rand.h>
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#include <openssl/rc4.h>
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#include <openssl/err.h>
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/* Size of key to use */
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#define SEED_SIZE 20
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/* Number of bytes to reseed after */
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#define REKEY_BYTES (1 << 24)
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static int rc4_ready = 0;
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static RC4_KEY rc4;
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unsigned int
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arc4random(void)
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{
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unsigned int r = 0;
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static int first_time = 1;
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if (rc4_ready <= 0) {
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if (first_time)
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seed_rng();
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first_time = 0;
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arc4random_stir();
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}
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RC4(&rc4, sizeof(r), (unsigned char *)&r, (unsigned char *)&r);
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rc4_ready -= sizeof(r);
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return(r);
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}
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void
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arc4random_stir(void)
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{
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unsigned char rand_buf[SEED_SIZE];
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int i;
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memset(&rc4, 0, sizeof(rc4));
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if (RAND_bytes(rand_buf, sizeof(rand_buf)) <= 0)
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fatal("Couldn't obtain random bytes (error %ld)",
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ERR_get_error());
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RC4_set_key(&rc4, sizeof(rand_buf), rand_buf);
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/*
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* Discard early keystream, as per recommendations in:
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* http://www.wisdom.weizmann.ac.il/~itsik/RC4/Papers/Rc4_ksa.ps
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*/
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for(i = 0; i <= 256; i += sizeof(rand_buf))
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RC4(&rc4, sizeof(rand_buf), rand_buf, rand_buf);
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memset(rand_buf, 0, sizeof(rand_buf));
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rc4_ready = REKEY_BYTES;
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}
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#endif /* !HAVE_ARC4RANDOM */
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#ifndef HAVE_ARC4RANDOM_BUF
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void
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arc4random_buf(void *_buf, size_t n)
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{
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size_t i;
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u_int32_t r = 0;
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char *buf = (char *)_buf;
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for (i = 0; i < n; i++) {
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if (i % 4 == 0)
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r = arc4random();
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buf[i] = r & 0xff;
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r >>= 8;
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}
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i = r = 0;
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}
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#endif /* !HAVE_ARC4RANDOM_BUF */
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#ifndef HAVE_ARC4RANDOM_UNIFORM
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/*
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* Calculate a uniformly distributed random number less than upper_bound
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* avoiding "modulo bias".
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*
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* Uniformity is achieved by generating new random numbers until the one
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* returned is outside the range [0, 2**32 % upper_bound). This
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* guarantees the selected random number will be inside
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* [2**32 % upper_bound, 2**32) which maps back to [0, upper_bound)
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* after reduction modulo upper_bound.
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*/
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u_int32_t
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arc4random_uniform(u_int32_t upper_bound)
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{
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u_int32_t r, min;
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if (upper_bound < 2)
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return 0;
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#if (ULONG_MAX > 0xffffffffUL)
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min = 0x100000000UL % upper_bound;
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#else
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/* Calculate (2**32 % upper_bound) avoiding 64-bit math */
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if (upper_bound > 0x80000000)
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min = 1 + ~upper_bound; /* 2**32 - upper_bound */
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else {
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/* (2**32 - (x * 2)) % x == 2**32 % x when x <= 2**31 */
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min = ((0xffffffff - (upper_bound * 2)) + 1) % upper_bound;
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}
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#endif
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/*
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* This could theoretically loop forever but each retry has
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* p > 0.5 (worst case, usually far better) of selecting a
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* number inside the range we need, so it should rarely need
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* to re-roll.
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*/
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for (;;) {
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r = arc4random();
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if (r >= min)
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break;
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}
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return r % upper_bound;
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}
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#endif /* !HAVE_ARC4RANDOM_UNIFORM */
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