mirror of
https://github.com/tytso/pwgen.git
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5f96a6ea2d
given a known file, and a known seed. (ie: pwgen -H ~/my_favourite.mp3#olivier@guerrier.com gives me a list of possibles passwords for my pop3 account, and I can ask this list again and again). Feature suggested and implemented by Olivier Guerrier <olivier@guerrier.com>.
96 lines
1.9 KiB
C
96 lines
1.9 KiB
C
/*
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* randnum.c -- generate (good) randum numbers.
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*
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* Copyright (C) 2001,2002 by Theodore Ts'o
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*
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* This file may be distributed under the terms of the GNU Public
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* License.
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*/
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#include <unistd.h>
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#include <stdlib.h>
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#include <sys/types.h>
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#include <sys/time.h>
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#include <sys/stat.h>
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#include <fcntl.h>
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#include <errno.h>
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#include "pwgen.h"
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#ifdef HAVE_DRAND48
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extern double drand48(void);
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#endif
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static int get_random_fd(void);
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/* Borrowed/adapted from e2fsprogs's UUID generation code */
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static int get_random_fd()
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{
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struct timeval tv;
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static int fd = -2;
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int i;
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if (fd == -2) {
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gettimeofday(&tv, 0);
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fd = open("/dev/urandom", O_RDONLY);
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if (fd == -1)
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fd = open("/dev/random", O_RDONLY | O_NONBLOCK);
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#ifdef HAVE_DRAND48
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srand48((tv.tv_sec<<9) ^ (getpgrp()<<15) ^
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(getpid()) ^ (tv.tv_usec>>11));
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#else
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srandom((getpid() << 16) ^ (getpgrp() << 8) ^ getuid()
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^ tv.tv_sec ^ tv.tv_usec);
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#endif
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}
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/* Crank the random number generator a few times */
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gettimeofday(&tv, 0);
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for (i = (tv.tv_sec ^ tv.tv_usec) & 0x1F; i > 0; i--)
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#ifdef HAVE_DRAND48
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drand48();
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#else
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random();
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#endif
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return fd;
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}
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/*
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* Generate a random number n, where 0 <= n < max_num, using
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* /dev/urandom if possible.
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*/
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int pw_random_number(max_num)
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int max_num;
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{
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int i, fd = get_random_fd();
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int lose_counter = 0, nbytes=4;
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unsigned int rand_num;
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char *cp = (char *) &rand_num;
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if (fd >= 0) {
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while (nbytes > 0) {
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i = read(fd, cp, nbytes);
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if ((i < 0) &&
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((errno == EINTR) || (errno == EAGAIN)))
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continue;
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if (i <= 0) {
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if (lose_counter++ == 8)
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break;
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continue;
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}
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nbytes -= i;
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cp += i;
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lose_counter = 0;
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}
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}
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if (nbytes == 0)
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return (rand_num % max_num);
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/* OK, we weren't able to use /dev/random, fall back to rand/rand48 */
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#ifdef HAVE_DRAND48
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return ((int) ((drand48() * max_num)));
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#else
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return ((int) (random() / ((float) RAND_MAX) * max_num));
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#endif
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}
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