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hping2

    1: /* rc4-based pseudo-random number generator for hping.
    2:  * Copyright (C) 2003 Salvatore Sanfilippo
    3:  * This software is released under the GPL license
    4:  * All rights reserved */
    5: 
    6: #include <sys/types.h>
    7: #include <sys/stat.h>
    8: #include <fcntl.h>
    9: #include <unistd.h>
   10: #include <sys/time.h>
   11: #include <time.h>
   12: 
   13: u_int32_t hp_rand(void);
   14: 
   15: /* The rc4 sbox */
   16: static unsigned char rc4_sbox[256];
   17: /* This flags is used to initialize the sbox the first time,
   18:  * without an explicit intialization step outside this file. */
   19: static int rc4_seedflag = 0;
   20: 
   21: /* Initialize the sbox with pseudo random data */
   22: static void hp_rand_init(void)
   23: {
   24: 	int i, fd;
   25: 
   26: 	/* Strong sbox initialization */
   27: 	fd = open("/dev/urandom", O_RDONLY);
   28: 	if (fd != -1) {
   29: 		read(fd, rc4_sbox, 256);
   30: 		close(fd);
   31: 	}
   32: 	/* Weaker sbox initialization */
   33: 	for (i = 0; i < 256; i++) {
   34: 		struct timeval tv;
   35: 		gettimeofday(&tv, NULL);
   36: 		if (i&1)
   37: 			rc4_sbox[i] ^= (tv.tv_usec >> (i&0xF)) & 0xFF;
   38: 		else
   39: 			rc4_sbox[i] ^= (tv.tv_sec >> (i&0xF)) & 0xFF;
   40: 	}
   41: 	rc4_seedflag = 1;
   42: }
   43: 
   44: #if 0
   45: /* Re-seed the generator with user-provided bytes. Not used for now. */
   46: static void hp_rand_seed(void *seed, size_t len)
   47: {
   48: 	int i;
   49: 
   50: 	if (len > 256) len = 256;
   51: 	memcpy(rc4_sbox, seed, len);
   52: 	/* discard the first 256 bytes of output after the reseed */
   53: 	for (i = 0; i < 32; i++)
   54: 		(void) hp_rand();
   55: }
   56: #endif
   57: 
   58: /* Generates a 32bit random number using an RC4-like algorithm */
   59: u_int32_t hp_rand(void)
   60: {
   61: 	u_int32_t r = 0;
   62: 	unsigned char *rc = (unsigned char*) &r;
   63: 	static unsigned int i = 0, j = 0;
   64: 	unsigned int si, sj, x;
   65: 
   66: 	/* initialization, only needed the first time */
   67: 	if (!rc4_seedflag)
   68: 		hp_rand_init();
   69: 	/* generates 4 bytes of pseudo-random data using RC4 */
   70: 	for (x = 0; x < 4; x++) {
   71: 		i = (i+1) & 0xff;
   72: 		si = rc4_sbox[i];
   73: 		j = (j + si) & 0xff;
   74: 		sj = rc4_sbox[j];
   75: 		rc4_sbox[i] = sj;
   76: 		rc4_sbox[j] = si;
   77: 		*rc++ = rc4_sbox[(si+sj)&0xff];
   78: 	}
   79: 	return r;
   80: }
   81: