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/*
* randnum.c -- generate (good) randum numbers.
*
* Copyright (C) 2001,2002 by Theodore Ts'o
*
* This file may be distributed under the terms of the GNU Public
* License.
*/
#include <stdio.h>
#include <unistd.h>
#include <stdlib.h>
#include <sys/types.h>
#include <sys/time.h>
#include <sys/stat.h>
#include <fcntl.h>
#include <errno.h>
#include "pwgen.h"
#ifdef HAVE_DRAND48
extern double drand48(void);
#endif
static int get_random_fd(void);
/* Borrowed/adapted from e2fsprogs's UUID generation code */
static int get_random_fd()
{
struct timeval tv;
static int fd = -2;
if (fd == -2) {
gettimeofday(&tv, 0);
fd = open("/dev/urandom", O_RDONLY);
if (fd == -1)
fd = open("/dev/random", O_RDONLY | O_NONBLOCK);
}
return fd;
}
/*
* Generate a random number n, where 0 <= n < max_num, using
* /dev/urandom if possible.
*/
int pw_random_number(max_num)
int max_num;
{
unsigned int rand_num;
int i, fd = get_random_fd();
int lose_counter = 0, nbytes = sizeof(rand_num);
char *cp = (char *) &rand_num;
if (fd >= 0) {
while (nbytes > 0) {
i = read(fd, cp, nbytes);
if ((i < 0) &&
((errno == EINTR) || (errno == EAGAIN)))
continue;
if (i <= 0) {
if (lose_counter++ == 8)
break;
continue;
}
nbytes -= i;
cp += i;
lose_counter = 0;
}
}
if (nbytes == 0)
return (rand_num % max_num);
/* We weren't able to use /dev/random, fail hard */
fprintf(stderr, "No entropy available!\n");
exit(1);
}
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