2 * This file is part of DisOrder
3 * Copyright (C) 2008 Richard Kettlewell
5 * This program is free software; you can redistribute it and/or modify
6 * it under the terms of the GNU General Public License as published by
7 * the Free Software Foundation; either version 2 of the License, or
8 * (at your option) any later version.
10 * This program is distributed in the hope that it will be useful, but
11 * WITHOUT ANY WARRANTY; without even the implied warranty of
12 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
13 * General Public License for more details.
15 * You should have received a copy of the GNU General Public License
16 * along with this program; if not, write to the Free Software
17 * Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA 02111-1307
21 /** @file lib/random.c
22 * @brief Random number generator
38 static int random_count
;
39 static int random_fd
= -1;
40 static arcfour_context random_ctx
[1];
42 /** @brief Rekey the RNG
44 * Resets the RNG's key to a random one read from /dev/urandom
46 static void random__rekey(void) {
51 if((random_fd
= open("/dev/urandom", O_RDONLY
)) < 0)
52 fatal(errno
, "opening /dev/urandom");
54 if((n
= read(random_fd
, key
, sizeof key
)) < 0)
55 fatal(errno
, "reading from /dev/urandom");
56 if((size_t)n
< sizeof key
)
57 fatal(0, "reading from /dev/urandom: short read");
58 arcfour_setkey(random_ctx
, key
, sizeof key
);
59 random_count
= 8 * 1024 * 1024;
62 /** @brief Get random bytes
63 * @param ptr Where to put random bytes
64 * @param bytes How many random bytes to generate
66 void random_get(void *ptr
, size_t bytes
) {
69 /* Encrypting 0s == just returning the keystream */
70 memset(ptr
, 0, bytes
);
71 arcfour_stream(random_ctx
, (char *)ptr
, (char *)ptr
, bytes
);
72 if(bytes
> (size_t)random_count
)
75 random_count
-= bytes
;
78 /** @brief Return a random ID string */
79 char *random_id(void) {
80 unsigned long words
[2];
83 random_get(words
, sizeof words
);
84 basen(words
, sizeof words
/ sizeof *words
, id
, sizeof id
, 62);