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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 <errno.h>
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26 #include <string.h>
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27
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28 #include <syscall.h>
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29 #include <unistd.h>
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30
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31
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32 struct uv__sysctl_args {
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33 int* name;
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34 int nlen;
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35 void* oldval;
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36 size_t* oldlenp;
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37 void* newval;
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38 size_t newlen;
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39 unsigned long unused[4];
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40 };
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41
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42
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43 int uv__random_sysctl(void* buf, size_t buflen) {
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44 static int name[] = {1 /*CTL_KERN*/, 40 /*KERN_RANDOM*/, 6 /*RANDOM_UUID*/};
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45 struct uv__sysctl_args args;
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46 char uuid[16];
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47 char* p;
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48 char* pe;
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49 size_t n;
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50
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51 p = buf;
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52 pe = p + buflen;
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53
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54 while (p < pe) {
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55 memset(&args, 0, sizeof(args));
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56
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57 args.name = name;
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58 args.nlen = ARRAY_SIZE(name);
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59 args.oldval = uuid;
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60 args.oldlenp = &n;
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61 n = sizeof(uuid);
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62
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63 /* Emits a deprecation warning with some kernels but that seems like
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64 * an okay trade-off for the fallback of the fallback: this function is
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65 * only called when neither getrandom(2) nor /dev/urandom are available.
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66 * Fails with ENOSYS on kernels configured without CONFIG_SYSCTL_SYSCALL.
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67 * At least arm64 never had a _sysctl system call and therefore doesn't
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68 * have a SYS__sysctl define either.
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69 */
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70 #ifdef SYS__sysctl
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71 if (syscall(SYS__sysctl, &args) == -1)
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72 return UV__ERR(errno);
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73 #else
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74 {
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75 (void) &args;
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76 return UV_ENOSYS;
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77 }
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78 #endif
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79
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80 if (n != sizeof(uuid))
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81 return UV_EIO; /* Can't happen. */
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82
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83 /* uuid[] is now a type 4 UUID. Bytes 6 and 8 (counting from zero) contain
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84 * 4 and 5 bits of entropy, respectively. For ease of use, we skip those
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85 * and only use 14 of the 16 bytes.
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86 */
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87 uuid[6] = uuid[14];
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88 uuid[8] = uuid[15];
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89
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90 n = pe - p;
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91 if (n > 14)
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92 n = 14;
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93
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94 memcpy(p, uuid, n);
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95 p += n;
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96 }
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97
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98 return 0;
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99 }
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