1 /*
2 __ __ _
3 ___\ \/ /_ __ __ _| |_
4 / _ \\ /| '_ \ / _` | __|
5 | __// \| |_) | (_| | |_
6 \___/_/\_\ .__/ \__,_|\__|
7 |_| XML parser
8
9 Copyright (c) 2017-2026 Sebastian Pipping <sebastian@pipping.org>
10 Copyright (c) 2017 Chanho Park <chanho61.park@samsung.com>
11 Copyright (c) 2022 Sean McBride <sean@rogue-research.com>
12 Copyright (c) 2026 Matthew Fernandez <matthew.fernandez@gmail.com>
13 Licensed under the MIT license:
14
15 Permission is hereby granted, free of charge, to any person obtaining
16 a copy of this software and associated documentation files (the
17 "Software"), to deal in the Software without restriction, including
18 without limitation the rights to use, copy, modify, merge, publish,
19 distribute, sublicense, and/or sell copies of the Software, and to permit
20 persons to whom the Software is furnished to do so, subject to the
21 following conditions:
22
23 The above copyright notice and this permission notice shall be included
24 in all copies or substantial portions of the Software.
25
26 THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND,
27 EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF
28 MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN
29 NO EVENT SHALL THE AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM,
30 DAMAGES OR OTHER LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR
31 OTHERWISE, ARISING FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE
32 USE OR OTHER DEALINGS IN THE SOFTWARE.
33
34 SPDX-License-Identifier: MIT
35 */
36
37 #include "expat_config.h" // for HAVE_GETRANDOM, HAVE_SYSCALL_GETRANDOM
38
39 #include "random_getrandom.h"
40
41 #if defined(HAVE_GETRANDOM)
42 # include <sys/random.h> /* getrandom */
43 #endif
44
45 #if defined(HAVE_SYSCALL_GETRANDOM)
46 # if ! defined(_GNU_SOURCE)
47 # define _GNU_SOURCE 1 /* syscall prototype */
48 # endif
49 # include <unistd.h> /* syscall */
50 # include <sys/syscall.h> /* SYS_getrandom */
51 #endif // defined(HAVE_SYSCALL_GETRANDOM)
52
53 #if ! defined(GRND_NONBLOCK)
54 # define GRND_NONBLOCK 0x0001
55 #endif /* defined(GRND_NONBLOCK) */
56
57 #include "memory_sanitizer.h"
58 #include <assert.h>
59 #include <errno.h>
60 #include <limits.h> // for INT_MAX
61
62 /* Obtain entropy on Linux 3.17+ */
63 bool
writeRandomBytes_getrandom_nonblock(void * target,size_t count)64 writeRandomBytes_getrandom_nonblock(void *target, size_t count) {
65 int success = false; /* full count bytes written? */
66 size_t bytesWrittenTotal = 0;
67 const unsigned int getrandomFlags = GRND_NONBLOCK;
68
69 do {
70 void *const currentTarget = (char *)target + bytesWrittenTotal;
71 const size_t bytesToWrite = count - bytesWrittenTotal;
72
73 assert(bytesToWrite <= INT_MAX);
74
75 errno = 0;
76
77 const int bytesWrittenMore =
78 #if defined(HAVE_GETRANDOM)
79 (int)getrandom(currentTarget, bytesToWrite, getrandomFlags);
80 // MSan understands `getrandom`, so does not need extra guidance
81 #else
82 (int)syscall(SYS_getrandom, currentTarget, bytesToWrite,
83 getrandomFlags);
84 // MSan does not understand `syscall`, so explain its effects
85 if (bytesWrittenMore > 0)
86 MSAN_UNPOISON(currentTarget, bytesWrittenMore);
87 #endif
88
89 if (bytesWrittenMore > 0) {
90 bytesWrittenTotal += bytesWrittenMore;
91 if (bytesWrittenTotal >= count)
92 success = true;
93 }
94 } while (! success && (errno == EINTR));
95
96 return success;
97 }
98