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annotate compat/getentropy.c @ 17:a08ef0674d8e

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author Guido Berhoerster <guido+pwm@berhoerster.name>
date Sat, 12 Aug 2017 10:41:52 +0200
parents a7e41e1a79c8
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1 /*
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2 * Copyright (C) 2016 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 /* needed for syscall(2) on Linux */
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25 #define _GNU_SOURCE
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26
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27 /* Linux >= 3.17 has getrandom(2) system call */
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28 #ifdef __linux__
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29 #include <unistd.h>
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30 #include <sys/syscall.h>
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31 #include <linux/random.h>
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32 #ifdef SYS_getrandom
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33 #define HAVE_GETRANDOM
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34 #endif /* SYS_getrandom */
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35 #endif /* __linux__ */
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36 /*
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37 * on unknown Unix systems without getentropy(2) or Linux without getrandom(2)
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38 * fall back to * reading from /dev/(u)random
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39 */
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40 #ifndef HAVE_GETRANDOM
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41 #include <stdio.h>
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42 #ifndef RANDOM_DEVICE
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43 #ifdef __linux__
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44 /* on Linux /dev/urandom should be good enough */
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45 #define RANDOM_DEVICE "/dev/urandom"
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46 #else /* __linux__ */
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47 /* on unknown Unix systems use the possibly blocking /dev/random */
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48 #define RANDOM_DEVICE "/dev/random"
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49 #endif /* __linux__ */
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50 #endif /* !RANDOM_DEVICE */
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51 #endif /* !HAVE_GETRANDOM */
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52 #include <errno.h>
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53
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54 #ifdef HAVE_GETRANDOM
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55 static int
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56 getentropy_linux_getrandom(void *buf, size_t buf_len)
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57 {
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58 int retval;
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59
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60 retval = syscall(SYS_getrandom, buf, buf_len, 0);
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61 if (retval < 0) {
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62 return (-1);
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63 } else if ((size_t)retval != buf_len) {
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64 errno = EIO;
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65 return (-1);
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66 }
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67
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68 return (0);
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69 }
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70 #else
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71 static int
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72 getentropy_dev_random(void *buf, size_t buf_len)
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73 {
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74 FILE *fp;
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75 int saved_errno;
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76
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77 fp = fopen(RANDOM_DEVICE, "r");
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78 if (fp == NULL) {
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79 return (-1);
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80 }
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81 if (fread(buf, 1, buf_len, fp) != buf_len) {
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82 saved_errno = errno;
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83 fclose(fp);
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84 errno = saved_errno;
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85 return (-1);
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86 }
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87 if (fclose(fp) != 0) {
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88 return (-1);
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89 }
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90
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91 return (0);
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92 }
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93 #endif /* HAVE_GETRANDOM */
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94
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95 int
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96 getentropy(void *buf, size_t buf_len)
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97 {
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98 if (buf_len > 256) {
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99 errno = EIO;
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100 return (-1);
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101 }
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102
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103 return (
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104 #ifdef HAVE_GETRANDOM
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105 getentropy_linux_getrandom(
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106 #else /* HAVE_GETRANDOM */
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107 getentropy_dev_random(
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108 #endif /* HAVE_GETRANDOM */
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109 buf, buf_len));
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110 }