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
32 struct 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
uv__random_sysctl(void * buf,size_t buflen)43 int 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
