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1 /* Copyright libuv contributors. All rights reserved.
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2 *
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3 * Permission is hereby granted, free of charge, to any person obtaining a copy
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4 * of this software and associated documentation files (the "Software"), to
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5 * deal in the Software without restriction, including without limitation the
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6 * rights to use, copy, modify, merge, publish, distribute, sublicense, and/or
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7 * sell copies of the Software, and to permit persons to whom the Software is
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8 * furnished to do so, subject to the following conditions:
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9 *
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10 * The above copyright notice and this permission notice shall be included in
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11 * all copies or substantial portions of the Software.
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12 *
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13 * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
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14 * IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
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15 * FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
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16 * AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
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17 * LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING
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18 * FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS
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19 * IN THE SOFTWARE.
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20 */
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21
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22 #include "uv.h"
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23 #include "internal.h"
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24
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25 #include <sys/stat.h>
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26 #include <unistd.h>
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27
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28 static uv_once_t once = UV_ONCE_INIT;
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29 static int status;
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30
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31
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32 int uv__random_readpath(const char* path, void* buf, size_t buflen) {
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33 struct stat s;
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34 size_t pos;
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35 ssize_t n;
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36 int fd;
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37
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38 fd = uv__open_cloexec(path, O_RDONLY);
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39
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40 if (fd < 0)
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41 return fd;
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42
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43 if (uv__fstat(fd, &s)) {
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44 uv__close(fd);
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45 return UV__ERR(errno);
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46 }
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47
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48 if (!S_ISCHR(s.st_mode)) {
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49 uv__close(fd);
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50 return UV_EIO;
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51 }
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52
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53 for (pos = 0; pos != buflen; pos += n) {
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54 do
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55 n = read(fd, (char*) buf + pos, buflen - pos);
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56 while (n == -1 && errno == EINTR);
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57
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58 if (n == -1) {
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59 uv__close(fd);
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60 return UV__ERR(errno);
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61 }
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62
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63 if (n == 0) {
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64 uv__close(fd);
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65 return UV_EIO;
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66 }
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67 }
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68
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69 uv__close(fd);
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70 return 0;
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71 }
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72
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73
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74 static void uv__random_devurandom_init(void) {
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75 char c;
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76
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77 /* Linux's random(4) man page suggests applications should read at least
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78 * once from /dev/random before switching to /dev/urandom in order to seed
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79 * the system RNG. Reads from /dev/random can of course block indefinitely
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80 * until entropy is available but that's the point.
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81 */
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82 status = uv__random_readpath("/dev/random", &c, 1);
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83 }
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84
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85
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86 int uv__random_devurandom(void* buf, size_t buflen) {
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87 uv_once(&once, uv__random_devurandom_init);
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88
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89 if (status != 0)
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90 return status;
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91
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92 return uv__random_readpath("/dev/urandom", buf, buflen);
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93 }
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