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 3 of the License, or
8 * (at your option) any later version.
10 * This program is distributed in the hope that it will be useful,
11 * but WITHOUT ANY WARRANTY; without even the implied warranty of
12 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
13 * GNU 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, see <http://www.gnu.org/licenses/>.
19 /** @file lib/random.c
20 * @brief Random number generator
36 static int random_count
;
37 static int random_fd
= -1;
38 static arcfour_context random_ctx
[1];
40 /** @brief Rekey the RNG
42 * Resets the RNG's key to a random one read from /dev/urandom
44 static void random__rekey(void) {
49 if((random_fd
= open("/dev/urandom", O_RDONLY
)) < 0)
50 disorder_fatal(errno
, "opening /dev/urandom");
52 if((n
= read(random_fd
, key
, sizeof key
)) < 0)
53 disorder_fatal(errno
, "reading from /dev/urandom");
54 if((size_t)n
< sizeof key
)
55 disorder_fatal(0, "reading from /dev/urandom: short read");
56 arcfour_setkey(random_ctx
, key
, sizeof key
);
57 random_count
= 8 * 1024 * 1024;
60 /** @brief Get random bytes
61 * @param ptr Where to put random bytes
62 * @param bytes How many random bytes to generate
64 void random_get(void *ptr
, size_t bytes
) {
67 /* Encrypting 0s == just returning the keystream */
68 memset(ptr
, 0, bytes
);
69 arcfour_stream(random_ctx
, (char *)ptr
, (char *)ptr
, bytes
);
70 if(bytes
> (size_t)random_count
)
73 random_count
-= bytes
;
76 /** @brief Return a random ID string */
77 char *random_id(void) {
81 random_get(words
, sizeof words
);
82 basen(words
, sizeof words
/ sizeof *words
, id
, sizeof id
, 62);