chiark / gitweb /
Merge from disorder.dev.
[disorder] / lib / random.c
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1/*
2 * This file is part of DisOrder
3 * Copyright (C) 2008 Richard Kettlewell
4 *
e7eb3a27 5 * This program is free software: you can redistribute it and/or modify
fcdff139 6 * it under the terms of the GNU General Public License as published by
e7eb3a27 7 * the Free Software Foundation, either version 3 of the License, or
fcdff139 8 * (at your option) any later version.
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9 *
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.
14 *
fcdff139 15 * You should have received a copy of the GNU General Public License
e7eb3a27 16 * along with this program. If not, see <http://www.gnu.org/licenses/>.
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17 */
18
19/** @file lib/random.c
20 * @brief Random number generator
21 *
22 */
23
05b75f8d 24#include "common.h"
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25
26#include <fcntl.h>
27#include <unistd.h>
28#include <errno.h>
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29
30#include "random.h"
31#include "log.h"
32#include "arcfour.h"
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33#include "basen.h"
34#include "mem.h"
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35
36static int random_count;
37static int random_fd = -1;
38static arcfour_context random_ctx[1];
39
40/** @brief Rekey the RNG
41 *
42 * Resets the RNG's key to a random one read from /dev/urandom
43 */
44static void random__rekey(void) {
45 char key[128];
46 int n;
47
48 if(random_fd < 0) {
49 if((random_fd = open("/dev/urandom", O_RDONLY)) < 0)
50 fatal(errno, "opening /dev/urandom");
51 }
52 if((n = read(random_fd, key, sizeof key)) < 0)
53 fatal(errno, "reading from /dev/urandom");
54 if((size_t)n < sizeof key)
55 fatal(0, "reading from /dev/urandom: short read");
56 arcfour_setkey(random_ctx, key, sizeof key);
57 random_count = 8 * 1024 * 1024;
58}
59
60/** @brief Get random bytes
61 * @param ptr Where to put random bytes
62 * @param bytes How many random bytes to generate
63 */
fdca70ee 64void random_get(void *ptr, size_t bytes) {
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65 if(random_count == 0)
66 random__rekey();
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)
71 random_count = 0;
72 else
73 random_count -= bytes;
74}
75
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76/** @brief Return a random ID string */
77char *random_id(void) {
1c814807 78 uint32_t words[2];
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79 char id[128];
80
81 random_get(words, sizeof words);
067eeb5f 82 basen(words, sizeof words / sizeof *words, id, sizeof id, 62);
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83 return xstrdup(id);
84}
85
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86/*
87Local Variables:
88c-basic-offset:2
89comment-column:40
90fill-column:79
91indent-tabs-mode:nil
92End:
93*/