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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/>. |
fcdff139 RK |
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 | |
36 | static int random_count; | |
37 | static int random_fd = -1; | |
38 | static 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 | */ | |
44 | static 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) | |
2e9ba080 | 50 | disorder_fatal(errno, "opening /dev/urandom"); |
fcdff139 RK |
51 | } |
52 | if((n = read(random_fd, key, sizeof key)) < 0) | |
2e9ba080 | 53 | disorder_fatal(errno, "reading from /dev/urandom"); |
fcdff139 | 54 | if((size_t)n < sizeof key) |
2e9ba080 | 55 | disorder_fatal(0, "reading from /dev/urandom: short read"); |
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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 | 64 | void 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 */ |
77 | char *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 | /* |
87 | Local Variables: | |
88 | c-basic-offset:2 | |
89 | comment-column:40 | |
90 | fill-column:79 | |
91 | indent-tabs-mode:nil | |
92 | End: | |
93 | */ |