| | 1 | /* |
| | 2 | * This file is part of DisOrder |
| | 3 | * Copyright (C) 2008 Richard Kettlewell |
| | 4 | * |
| | 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. |
| | 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 | * |
| | 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/>. |
| | 17 | */ |
| | 18 | |
| | 19 | /** @file lib/random.c |
| | 20 | * @brief Random number generator |
| | 21 | * |
| | 22 | */ |
| | 23 | |
| | 24 | #include "common.h" |
| | 25 | |
| | 26 | #include <fcntl.h> |
| | 27 | #include <unistd.h> |
| | 28 | #include <errno.h> |
| | 29 | |
| | 30 | #include "random.h" |
| | 31 | #include "log.h" |
| | 32 | #include "arcfour.h" |
| | 33 | #include "basen.h" |
| | 34 | #include "mem.h" |
| | 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) |
| | 50 | disorder_fatal(errno, "opening /dev/urandom"); |
| | 51 | } |
| | 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; |
| | 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 | */ |
| | 64 | void random_get(void *ptr, size_t bytes) { |
| | 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 | |
| | 76 | /** @brief Return a random ID string */ |
| | 77 | char *random_id(void) { |
| | 78 | uint32_t words[2]; |
| | 79 | char id[128]; |
| | 80 | |
| | 81 | random_get(words, sizeof words); |
| | 82 | basen(words, sizeof words / sizeof *words, id, sizeof id, 62); |
| | 83 | return xstrdup(id); |
| | 84 | } |
| | 85 | |
| | 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 | */ |
~mdw / disorder / blame_incremental