1/* Copyright libuv contributors. All rights reserved.
2 *
3 * Permission is hereby granted, free of charge, to any person obtaining a copy
4 * of this software and associated documentation files (the "Software"), to
5 * deal in the Software without restriction, including without limitation the
6 * rights to use, copy, modify, merge, publish, distribute, sublicense, and/or
7 * sell copies of the Software, and to permit persons to whom the Software is
8 * furnished to do so, subject to the following conditions:
9 *
10 * The above copyright notice and this permission notice shall be included in
11 * all copies or substantial portions of the Software.
12 *
13 * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
14 * IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
15 * FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
16 * AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
17 * LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING
18 * FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS
19 * IN THE SOFTWARE.
20 */
21
22#include "uv.h"
23#include "internal.h"
24
25#include <errno.h>
26#include <string.h>
27
28#include <syscall.h>
29#include <unistd.h>
30
31
32struct uv__sysctl_args {
33  int* name;
34  int nlen;
35  void* oldval;
36  size_t* oldlenp;
37  void* newval;
38  size_t newlen;
39  unsigned long unused[4];
40};
41
42
43int uv__random_sysctl(void* buf, size_t buflen) {
44  static int name[] = {1 /*CTL_KERN*/, 40 /*KERN_RANDOM*/, 6 /*RANDOM_UUID*/};
45  struct uv__sysctl_args args;
46  char uuid[16];
47  char* p;
48  char* pe;
49  size_t n;
50
51  p = buf;
52  pe = p + buflen;
53
54  while (p < pe) {
55    memset(&args, 0, sizeof(args));
56
57    args.name = name;
58    args.nlen = ARRAY_SIZE(name);
59    args.oldval = uuid;
60    args.oldlenp = &n;
61    n = sizeof(uuid);
62
63    /* Emits a deprecation warning with some kernels but that seems like
64     * an okay trade-off for the fallback of the fallback: this function is
65     * only called when neither getrandom(2) nor /dev/urandom are available.
66     * Fails with ENOSYS on kernels configured without CONFIG_SYSCTL_SYSCALL.
67     * At least arm64 never had a _sysctl system call and therefore doesn't
68     * have a SYS__sysctl define either.
69     */
70#ifdef SYS__sysctl
71    if (syscall(SYS__sysctl, &args) == -1)
72      return UV__ERR(errno);
73#else
74    {
75      (void) &args;
76      return UV_ENOSYS;
77    }
78#endif
79
80    if (n != sizeof(uuid))
81      return UV_EIO;  /* Can't happen. */
82
83    /* uuid[] is now a type 4 UUID. Bytes 6 and 8 (counting from zero) contain
84     * 4 and 5 bits of entropy, respectively. For ease of use, we skip those
85     * and only use 14 of the 16 bytes.
86     */
87    uuid[6] = uuid[14];
88    uuid[8] = uuid[15];
89
90    n = pe - p;
91    if (n > 14)
92      n = 14;
93
94    memcpy(p, uuid, n);
95    p += n;
96  }
97
98  return 0;
99}
100