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annotate rand-dev-random.c @ 25:616385fa1fd9

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Build common functions as a library that can be reused
author Guido Berhoerster <guido+pwm@berhoerster.name>
date Wed, 20 Sep 2017 23:57:51 +0200
parents 8768fbd09bc5
children
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1 /*
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2 * Copyright (C) 2017 Guido Berhoerster <guido+pwm@berhoerster.name>
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3 *
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4 * Permission is hereby granted, free of charge, to any person obtaining
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5 * a copy of this software and associated documentation files (the
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6 * "Software"), to deal in the Software without restriction, including
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7 * without limitation the rights to use, copy, modify, merge, publish,
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8 * distribute, sublicense, and/or sell copies of the Software, and to
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9 * permit persons to whom the Software is furnished to do so, subject to
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10 * the following conditions:
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11 *
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12 * The above copyright notice and this permission notice shall be included
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13 * in all copies or substantial portions of the Software.
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14 *
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15 * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND,
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16 * EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF
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17 * MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT.
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18 * IN NO EVENT SHALL THE AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY
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19 * CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER IN AN ACTION OF CONTRACT,
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20 * TORT OR OTHERWISE, ARISING FROM, OUT OF OR IN CONNECTION WITH THE
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21 * SOFTWARE OR THE USE OR OTHER DEALINGS IN THE SOFTWARE.
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22 */
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23
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24 #include "compat.h"
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25
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26 #ifdef HAVE_ERR_H
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27 #include <err.h>
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28 #endif /* HAVE_ERR_H */
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29 #include <errno.h>
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30 #include <fcntl.h>
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31 #include <sys/stat.h>
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32 #include <unistd.h>
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33
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34 #include "rand.h"
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35
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36 #ifdef __linux__
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37 #define PATH_DEV_RANDOM "/dev/urandom"
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38 #else
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39 #define PATH_DEV_RANDOM "/dev/random"
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40 #endif /* __linux__ */
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41
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42 void
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43 rand_buf(void *buf, size_t buf_size)
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44 {
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45 unsigned char *p = buf;
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46 int fd;
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47 ssize_t nread;
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48 size_t nsize = buf_size;
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49
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50 do {
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51 fd = open(PATH_DEV_RANDOM, O_RDONLY);
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52 } while ((fd < 0) && (errno == EINTR));
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53 if (fd < 0) {
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54 err(1, "open");
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55 }
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56
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57 while (nsize > 0) {
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58 nread = read(fd, p, nsize);
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59 if (nread < 0) {
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60 if (errno == EINTR) {
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61 continue;
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62 }
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63 err(1, "read");
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64 }
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65 p += nread;
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66 nsize -= nread;
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67 }
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68
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69 while ((close(fd) < 0) && (errno == EINTR));
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70 }
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71
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72 uint32_t
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73 rand_random(void)
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74 {
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75 uint32_t x;
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76
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77 rand_buf(&x, sizeof (x));
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78
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79 return (x);
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80 }
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81
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82 /* random number between 0 and upper_bound - 1 without modulo bias */
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83 uint32_t
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84 rand_uniform(uint32_t upper_bound)
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85 {
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86 uint32_t r;
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87 /* (2^32 - upper_bound) % upper_bound */
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88 uint32_t threshold = -upper_bound % upper_bound;
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89
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90 do {
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91 r = rand_random();
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92 } while (r < threshold);
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93
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94 return (r % upper_bound);
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95 }