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/* $Id$ */
/*
*
* Copyright (C) 2003 David Mazieres (dm@uun.org)
*
* This program is free software; you can redistribute it and/or
* modify it under the terms of the GNU General Public License as
* published by the Free Software Foundation; either version 2, or (at
* your option) any later version.
*
* This program is distributed in the hope that it will be useful, but
* WITHOUT ANY WARRANTY; without even the implied warranty of
* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
* General Public License for more details.
*
* You should have received a copy of the GNU General Public License
* along with this program; if not, write to the Free Software
* Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA 02111-1307
* USA
*
*/
#include "sysconf.h"
/* XXX - need initializer because of broken Apple Darwin linker */
u_int32_t (*arandom_fn) () = 0;
#ifndef HAVE_ARC4RANDOM
/* This is a simple random number generator, based on the ARC4 stream
* cipher. THIS IS NOT CRYPTOGRAPHICALLY SECURE! It is simply for
* getting a somewhat random-looking series of bytes. In order to get
* cryptographically secure random numbers, you have to set the
* arandom_fn function pointer to a real cryptographic pseudo-random
* generator
*/
struct arc4rnd {
u_char i;
u_char j;
u_char s[256];
};
typedef struct arc4rnd arc4rnd;
static inline u_int32_t
arc4rnd_getbyte (arc4rnd *a)
{
u_char si, sj;
a->i = (a->i + 1) & 0xff;
si = a->s[a->i];
a->j = (a->j + si) & 0xff;
sj = a->s[a->j];
a->s[a->i] = sj;
a->s[a->j] = si;
return a->s[(si + sj) & 0xff];
}
static void
arc4rnd_reset (arc4rnd *a)
{
int n;
a->i = 0xff;
a->j = 0;
for (n = 0; n < 0x100; n++)
a->s[n] = n;
}
static void
_arc4rnd_setkey (arc4rnd *a, const u_char *key, size_t keylen)
{
u_int n, keypos;
u_char si;
for (n = 0, keypos = 0; n < 256; n++, keypos++) {
if (keypos >= keylen)
keypos = 0;
a->i = (a->i + 1) & 0xff;
si = a->s[a->i];
a->j = (a->j + si + key[keypos]) & 0xff;
a->s[a->i] = a->s[a->j];
a->s[a->j] = si;
}
}
static void
arc4rnd_setkey (arc4rnd *a, const void *_key, size_t len)
{
const u_char *key = (const u_char *) _key;
arc4rnd_reset (a);
while (len > 128) {
len -= 128;
key += 128;
_arc4rnd_setkey (a, key, 128);
}
if (len > 0)
_arc4rnd_setkey (a, key, len);
a->j = a->i;
}
static arc4rnd bad_random_state;
struct bad_random_junk {
struct timespec now;
pid_t pid;
};
static void
bad_random_init ()
{
int i;
struct bad_random_junk brj;
#ifdef SFS_DEV_RANDOM
int fd = open (SFS_DEV_RANDOM, O_RDONLY);
if (fd >= 0) {
char buf[256];
int n;
if ((n = fcntl (fd, F_GETFL)) != -1
&& fcntl (fd, F_SETFL, n | O_NONBLOCK) != -1
&& (n = read (fd, buf, sizeof (buf))) >= 12) {
close (fd);
arc4rnd_setkey (&bad_random_state, buf, n);
return;
}
close (fd);
}
#endif /* SFS_DEV_RANDOM */
clock_gettime (CLOCK_REALTIME, &brj.now);
brj.pid = getpid ();
arc4rnd_setkey (&bad_random_state, &brj, sizeof (brj));
for (i = 0; i < 256; i++)
arc4rnd_getbyte (&bad_random_state);
}
static u_int32_t
bad_random ()
{
return arc4rnd_getbyte (&bad_random_state)
| arc4rnd_getbyte (&bad_random_state) << 8
| arc4rnd_getbyte (&bad_random_state) << 16
| arc4rnd_getbyte (&bad_random_state) << 24;
}
#endif /* !HAVE_ARC4RANDOM */
u_int32_t
arandom ()
{
if (!arandom_fn) {
#ifdef HAVE_ARC4RANDOM
arandom_fn = arc4random;
#else /* !HAVE_ARC4RANDOM */
bad_random_init ();
arandom_fn = bad_random;
#endif /* !HAVE_ARC4RANDOM */
}
return (*arandom_fn) ();
}
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