1 | /* $OpenBSD: arc4random.c,v 1.52 2015/01/16 16:48:51 deraadt Exp $ */ |
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2 | |
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3 | /* |
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4 | * Copyright (c) 1996, David Mazieres <dm@uun.org> |
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5 | * Copyright (c) 2008, Damien Miller <djm@openbsd.org> |
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6 | * Copyright (c) 2013, Markus Friedl <markus@openbsd.org> |
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7 | * Copyright (c) 2014, Theo de Raadt <deraadt@openbsd.org> |
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8 | * |
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9 | * Permission to use, copy, modify, and distribute this software for any |
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10 | * purpose with or without fee is hereby granted, provided that the above |
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11 | * copyright notice and this permission notice appear in all copies. |
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12 | * |
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13 | * THE SOFTWARE IS PROVIDED "AS IS" AND THE AUTHOR DISCLAIMS ALL WARRANTIES |
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14 | * WITH REGARD TO THIS SOFTWARE INCLUDING ALL IMPLIED WARRANTIES OF |
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15 | * MERCHANTABILITY AND FITNESS. IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR |
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16 | * ANY SPECIAL, DIRECT, INDIRECT, OR CONSEQUENTIAL DAMAGES OR ANY DAMAGES |
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17 | * WHATSOEVER RESULTING FROM LOSS OF USE, DATA OR PROFITS, WHETHER IN AN |
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18 | * ACTION OF CONTRACT, NEGLIGENCE OR OTHER TORTIOUS ACTION, ARISING OUT OF |
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19 | * OR IN CONNECTION WITH THE USE OR PERFORMANCE OF THIS SOFTWARE. |
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20 | */ |
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21 | |
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22 | /* |
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23 | * ChaCha based random number generator for OpenBSD. |
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24 | */ |
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25 | |
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26 | #include <fcntl.h> |
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27 | #include <limits.h> |
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28 | #include <signal.h> |
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29 | #include <stdint.h> |
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30 | #include <stdlib.h> |
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31 | #include <string.h> |
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32 | #include <unistd.h> |
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33 | #include <sys/types.h> |
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34 | #include <sys/time.h> |
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35 | |
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36 | #define KEYSTREAM_ONLY |
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37 | #include "chacha_private.h" |
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38 | |
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39 | #define min(a, b) ((a) < (b) ? (a) : (b)) |
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40 | #ifdef __GNUC__ |
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41 | #define inline __inline |
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42 | #else /* !__GNUC__ */ |
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43 | #define inline |
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44 | #endif /* !__GNUC__ */ |
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45 | |
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46 | #define KEYSZ 32 |
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47 | #define IVSZ 8 |
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48 | #define BLOCKSZ 64 |
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49 | #define RSBUFSZ (16*BLOCKSZ) |
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50 | |
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51 | /* Marked MAP_INHERIT_ZERO, so zero'd out in fork children. */ |
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52 | static struct _rs { |
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53 | size_t rs_have; /* valid bytes at end of rs_buf */ |
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54 | size_t rs_count; /* bytes till reseed */ |
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55 | } *rs; |
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56 | |
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57 | /* Maybe be preserved in fork children, if _rs_allocate() decides. */ |
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58 | static struct _rsx { |
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59 | chacha_ctx rs_chacha; /* chacha context for random keystream */ |
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60 | u_char rs_buf[RSBUFSZ]; /* keystream blocks */ |
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61 | } *rsx; |
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62 | |
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63 | static inline int _rs_allocate(struct _rs **, struct _rsx **); |
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64 | static inline void _rs_forkdetect(void); |
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65 | #include "arc4random.h" |
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66 | |
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67 | static inline void _rs_rekey(u_char *dat, size_t datlen); |
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68 | |
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69 | static inline void |
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70 | _rs_init(u_char *buf, size_t n) |
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71 | { |
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72 | if (n < KEYSZ + IVSZ) |
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73 | return; |
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74 | |
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75 | if (rs == NULL) { |
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76 | if (_rs_allocate(&rs, &rsx) == -1) |
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77 | abort(); |
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78 | } |
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79 | |
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80 | chacha_keysetup(&rsx->rs_chacha, buf, KEYSZ * 8, 0); |
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81 | chacha_ivsetup(&rsx->rs_chacha, buf + KEYSZ); |
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82 | } |
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83 | |
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84 | static void |
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85 | _rs_stir(void) |
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86 | { |
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87 | u_char rnd[KEYSZ + IVSZ]; |
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88 | |
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89 | if (getentropy(rnd, sizeof rnd) == -1) |
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90 | _getentropy_fail(); |
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91 | |
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92 | if (!rs) |
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93 | _rs_init(rnd, sizeof(rnd)); |
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94 | else |
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95 | _rs_rekey(rnd, sizeof(rnd)); |
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96 | explicit_bzero(rnd, sizeof(rnd)); /* discard source seed */ |
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97 | |
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98 | /* invalidate rs_buf */ |
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99 | rs->rs_have = 0; |
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100 | memset(rsx->rs_buf, 0, sizeof(rsx->rs_buf)); |
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101 | |
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102 | rs->rs_count = 1600000; |
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103 | } |
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104 | |
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105 | static inline void |
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106 | _rs_stir_if_needed(size_t len) |
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107 | { |
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108 | _rs_forkdetect(); |
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109 | if (!rs || rs->rs_count <= len) |
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110 | _rs_stir(); |
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111 | if (rs->rs_count <= len) |
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112 | rs->rs_count = 0; |
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113 | else |
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114 | rs->rs_count -= len; |
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115 | } |
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116 | |
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117 | static inline void |
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118 | _rs_rekey(u_char *dat, size_t datlen) |
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119 | { |
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120 | #ifndef KEYSTREAM_ONLY |
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121 | memset(rsx->rs_buf, 0, sizeof(rsx->rs_buf)); |
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122 | #endif |
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123 | /* fill rs_buf with the keystream */ |
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124 | chacha_encrypt_bytes(&rsx->rs_chacha, rsx->rs_buf, |
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125 | rsx->rs_buf, sizeof(rsx->rs_buf)); |
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126 | /* mix in optional user provided data */ |
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127 | if (dat) { |
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128 | size_t i, m; |
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129 | |
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130 | m = min(datlen, KEYSZ + IVSZ); |
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131 | for (i = 0; i < m; i++) |
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132 | rsx->rs_buf[i] ^= dat[i]; |
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133 | } |
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134 | /* immediately reinit for backtracking resistance */ |
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135 | _rs_init(rsx->rs_buf, KEYSZ + IVSZ); |
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136 | memset(rsx->rs_buf, 0, KEYSZ + IVSZ); |
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137 | rs->rs_have = sizeof(rsx->rs_buf) - KEYSZ - IVSZ; |
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138 | } |
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139 | |
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140 | static inline void |
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141 | _rs_random_buf(void *_buf, size_t n) |
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142 | { |
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143 | u_char *buf = (u_char *)_buf; |
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144 | u_char *keystream; |
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145 | size_t m; |
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146 | |
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147 | _rs_stir_if_needed(n); |
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148 | while (n > 0) { |
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149 | if (rs->rs_have > 0) { |
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150 | m = min(n, rs->rs_have); |
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151 | keystream = rsx->rs_buf + sizeof(rsx->rs_buf) |
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152 | - rs->rs_have; |
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153 | memcpy(buf, keystream, m); |
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154 | memset(keystream, 0, m); |
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155 | buf += m; |
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156 | n -= m; |
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157 | rs->rs_have -= m; |
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158 | } |
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159 | if (rs->rs_have == 0) |
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160 | _rs_rekey(NULL, 0); |
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161 | } |
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162 | } |
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163 | |
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164 | static inline void |
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165 | _rs_random_u32(uint32_t *val) |
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166 | { |
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167 | u_char *keystream; |
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168 | |
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169 | _rs_stir_if_needed(sizeof(*val)); |
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170 | if (rs->rs_have < sizeof(*val)) |
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171 | _rs_rekey(NULL, 0); |
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172 | keystream = rsx->rs_buf + sizeof(rsx->rs_buf) - rs->rs_have; |
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173 | memcpy(val, keystream, sizeof(*val)); |
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174 | memset(keystream, 0, sizeof(*val)); |
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175 | rs->rs_have -= sizeof(*val); |
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176 | } |
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177 | |
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178 | uint32_t |
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179 | arc4random(void) |
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180 | { |
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181 | uint32_t val; |
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182 | |
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183 | #ifndef __SINGLE_THREAD__ |
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184 | _ARC4_LOCK(); |
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185 | #endif |
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186 | _rs_random_u32(&val); |
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187 | #ifndef __SINGLE_THREAD__ |
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188 | _ARC4_UNLOCK(); |
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189 | #endif |
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190 | return val; |
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191 | } |
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192 | |
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193 | void |
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194 | arc4random_buf(void *buf, size_t n) |
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195 | { |
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196 | #ifndef __SINGLE_THREAD__ |
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197 | _ARC4_LOCK(); |
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198 | #endif |
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199 | _rs_random_buf(buf, n); |
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200 | #ifndef __SINGLE_THREAD__ |
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201 | _ARC4_UNLOCK(); |
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202 | #endif |
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203 | } |
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