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1 /*
2  * Copyright 2017 Timothy Arceri
3  *
4  * Permission is hereby granted, free of charge, to any person obtaining a
5  * copy of this software and associated documentation files (the "Software"),
6  * to deal in the Software without restriction, including without limitation
7  * the rights to use, copy, modify, merge, publish, distribute, sublicense,
8  * and/or sell copies of the Software, and to permit persons to whom the
9  * Software is furnished to do so, subject to the following conditions:
10  *
11  * The above copyright notice and this permission notice (including the next
12  * paragraph) shall be included in all copies or substantial portions of the
13  * Software.
14  *
15  * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
16  * IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
17  * FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT.  IN NO EVENT SHALL
18  * THE AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
19  * LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
20  * OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE
21  * SOFTWARE.
22  *
23  */
24 
25 #include "detect_os.h"
26 
27 #if !DETECT_OS_WINDOWS
28 #if defined(HAVE_GETRANDOM)
29 #include <sys/random.h>
30 #endif
31 #include <unistd.h>
32 #include <fcntl.h>
33 #endif
34 
35 #include <time.h>
36 
37 #include "rand_xor.h"
38 
39 /* Super fast random number generator.
40  *
41  * This rand_xorshift128plus function by Sebastiano Vigna belongs
42  * to the public domain.
43  */
44 uint64_t
rand_xorshift128plus(uint64_t seed[2])45 rand_xorshift128plus(uint64_t seed[2])
46 {
47    uint64_t *s = seed;
48 
49    uint64_t s1 = s[0];
50    const uint64_t s0 = s[1];
51    s[0] = s0;
52    s1 ^= s1 << 23;
53    s[1] = s1 ^ s0 ^ (s1 >> 18) ^ (s0 >> 5);
54 
55    return s[1] + s0;
56 }
57 
58 void
s_rand_xorshift128plus(uint64_t seed[2],bool randomised_seed)59 s_rand_xorshift128plus(uint64_t seed[2], bool randomised_seed)
60 {
61    if (!randomised_seed) {
62       /* Use a fixed seed */
63       seed[0] = 0x3bffb83978e24f88;
64       seed[1] = 0x9238d5d56c71cd35;
65       return;
66    }
67 
68 #if !DETECT_OS_WINDOWS
69    size_t seed_size = sizeof(uint64_t) * 2;
70 
71 #if defined(HAVE_GETRANDOM)
72    ssize_t ret = getrandom(seed, seed_size, GRND_NONBLOCK);
73    if (ret == seed_size)
74       return;
75 #endif
76 
77    int fd = open("/dev/urandom", O_RDONLY);
78    if (fd >= 0) {
79       if (read(fd, seed, seed_size) == seed_size) {
80          close(fd);
81          return;
82       }
83       close(fd);
84    }
85 #endif
86 
87    seed[0] = 0x3bffb83978e24f88;
88    seed[1] = time(NULL);
89 }
90