| 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 2 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, 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. |
| 14 | * |
| 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 |
| 18 | * USA |
| 19 | */ |
| 20 | |
| 21 | /** @file lib/random.c |
| 22 | * @brief Random number generator |
| 23 | * |
| 24 | */ |
| 25 | |
| 26 | #include "common.h" |
| 27 | |
| 28 | #include <fcntl.h> |
| 29 | #include <unistd.h> |
| 30 | #include <errno.h> |
| 31 | |
| 32 | #include "random.h" |
| 33 | #include "log.h" |
| 34 | #include "arcfour.h" |
| 35 | #include "basen.h" |
| 36 | #include "mem.h" |
| 37 | |
| 38 | static int random_count; |
| 39 | static int random_fd = -1; |
| 40 | static arcfour_context random_ctx[1]; |
| 41 | |
| 42 | /** @brief Rekey the RNG |
| 43 | * |
| 44 | * Resets the RNG's key to a random one read from /dev/urandom |
| 45 | */ |
| 46 | static void random__rekey(void) { |
| 47 | char key[128]; |
| 48 | int n; |
| 49 | |
| 50 | if(random_fd < 0) { |
| 51 | if((random_fd = open("/dev/urandom", O_RDONLY)) < 0) |
| 52 | fatal(errno, "opening /dev/urandom"); |
| 53 | } |
| 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; |
| 60 | } |
| 61 | |
| 62 | /** @brief Get random bytes |
| 63 | * @param ptr Where to put random bytes |
| 64 | * @param bytes How many random bytes to generate |
| 65 | */ |
| 66 | void random_get(void *ptr, size_t bytes) { |
| 67 | if(random_count == 0) |
| 68 | random__rekey(); |
| 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) |
| 73 | random_count = 0; |
| 74 | else |
| 75 | random_count -= bytes; |
| 76 | } |
| 77 | |
| 78 | /** @brief Return a random ID string */ |
| 79 | char *random_id(void) { |
| 80 | unsigned long words[2]; |
| 81 | char id[128]; |
| 82 | |
| 83 | random_get(words, sizeof words); |
| 84 | basen(words, sizeof words / sizeof *words, id, sizeof id, 62); |
| 85 | return xstrdup(id); |
| 86 | } |
| 87 | |
| 88 | /* |
| 89 | Local Variables: |
| 90 | c-basic-offset:2 |
| 91 | comment-column:40 |
| 92 | fill-column:79 |
| 93 | indent-tabs-mode:nil |
| 94 | End: |
| 95 | */ |