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/* rc4-based pseudo-random number generator for hping.
* Copyright (C) 2003 Salvatore Sanfilippo
* This software is released under the GPL license
* All rights reserved */
/* $Id: random.c,v 1.3 2004/06/04 07:22:38 antirez Exp $ */
#include <sys/types.h>
#include <sys/stat.h>
#include <fcntl.h>
#include <unistd.h>
#include <sys/time.h>
#include <time.h>
#include "fixtypes.h"
u_int32_t hp_rand(void);
/* The rc4 sbox */
static unsigned char rc4_sbox[256];
/* This flags is used to initialize the sbox the first time,
* without an explicit intialization step outside this file. */
static int rc4_seedflag = 0;
/* Initialize the sbox with pseudo random data */
static void hp_rand_init(void)
{
int i, fd;
/* Strong sbox initialization */
fd = open("/dev/urandom", O_RDONLY);
if (fd != -1) {
read(fd, rc4_sbox, 256);
close(fd);
}
/* Weaker sbox initialization */
for (i = 0; i < 256; i++) {
struct timeval tv;
gettimeofday(&tv, NULL);
if (i&1)
rc4_sbox[i] ^= (tv.tv_usec >> (i&0xF)) & 0xFF;
else
rc4_sbox[i] ^= (tv.tv_sec >> (i&0xF)) & 0xFF;
}
rc4_seedflag = 1;
}
#if 0
/* Re-seed the generator with user-provided bytes. Not used for now. */
static void hp_rand_seed(void *seed, size_t len)
{
int i;
if (len > 256) len = 256;
memcpy(rc4_sbox, seed, len);
/* discard the first 256 bytes of output after the reseed */
for (i = 0; i < 32; i++)
(void) hp_rand();
}
#endif
/* Generates a 32bit random number using an RC4-like algorithm */
u_int32_t hp_rand(void)
{
u_int32_t r = 0;
unsigned char *rc = (unsigned char*) &r;
static unsigned int i = 0, j = 0;
unsigned int si, sj, x;
/* initialization, only needed the first time */
if (!rc4_seedflag)
hp_rand_init();
/* generates 4 bytes of pseudo-random data using RC4 */
for (x = 0; x < 4; x++) {
i = (i+1) & 0xff;
si = rc4_sbox[i];
j = (j + si) & 0xff;
sj = rc4_sbox[j];
rc4_sbox[i] = sj;
rc4_sbox[j] = si;
*rc++ = rc4_sbox[(si+sj)&0xff];
}
return r;
}