1 /*
2 __ __ _
3 ___\ \/ /_ __ __ _| |_
4 / _ \\ /| '_ \ / _` | __|
5 | __// \| |_) | (_| | |_
6 \___/_/\_\ .__/ \__,_|\__|
7 |_| XML parser
8
9 Copyright (c) 2017-2026 Sebastian Pipping <sebastian@pipping.org>
10 Copyright (c) 2026 Matthew Fernandez <matthew.fernandez@gmail.com>
11 Licensed under the MIT license:
12
13 Permission is hereby granted, free of charge, to any person obtaining
14 a copy of this software and associated documentation files (the
15 "Software"), to deal in the Software without restriction, including
16 without limitation the rights to use, copy, modify, merge, publish,
17 distribute, sublicense, and/or sell copies of the Software, and to permit
18 persons to whom the Software is furnished to do so, subject to the
19 following conditions:
20
21 The above copyright notice and this permission notice shall be included
22 in all copies or substantial portions of the Software.
23
24 THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND,
25 EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF
26 MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN
27 NO EVENT SHALL THE AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM,
28 DAMAGES OR OTHER LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR
29 OTHERWISE, ARISING FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE
30 USE OR OTHER DEALINGS IN THE SOFTWARE.
31 */
32
33 #include "random_dev_urandom.h"
34
35 #if ! defined(_POSIX_C_SOURCE) \
36 || (defined(_POSIX_C_SOURCE) && (_POSIX_C_SOURCE < 200809L))
37 # define _POSIX_C_SOURCE 200809L // for O_CLOEXEC
38 #endif
39
40 #include <errno.h>
41 #include <fcntl.h> // open
42 #include <unistd.h> // close
43
44 /* Extract entropy from /dev/urandom */
45 bool
writeRandomBytes_dev_urandom(void * target,size_t count)46 writeRandomBytes_dev_urandom(void *target, size_t count) {
47 int success = false; /* full count bytes written? */
48 size_t bytesWrittenTotal = 0;
49
50 const int fd = open("/dev/urandom", O_RDONLY | O_CLOEXEC);
51 if (fd < 0) {
52 return 0;
53 }
54
55 do {
56 void *const currentTarget = (void *)((char *)target + bytesWrittenTotal);
57 const size_t bytesToWrite = count - bytesWrittenTotal;
58
59 errno = 0;
60
61 const ssize_t bytesWrittenMore = read(fd, currentTarget, bytesToWrite);
62
63 if (bytesWrittenMore > 0) {
64 bytesWrittenTotal += bytesWrittenMore;
65 if (bytesWrittenTotal >= count)
66 success = true;
67 }
68 } while (! success && (errno == EINTR));
69
70 close(fd);
71 return success;
72 }
73