1 | /* Implementation of getentropy based on getrandom. |
2 | Copyright (C) 2016-2024 Free Software Foundation, Inc. |
3 | This file is part of the GNU C Library. |
4 | |
5 | The GNU C Library is free software; you can redistribute it and/or |
6 | modify it under the terms of the GNU Lesser General Public |
7 | License as published by the Free Software Foundation; either |
8 | version 2.1 of the License, or (at your option) any later version. |
9 | |
10 | The GNU C Library is distributed in the hope that it will be useful, |
11 | but WITHOUT ANY WARRANTY; without even the implied warranty of |
12 | MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU |
13 | Lesser General Public License for more details. |
14 | |
15 | You should have received a copy of the GNU Lesser General Public |
16 | License along with the GNU C Library; if not, see |
17 | <https://www.gnu.org/licenses/>. */ |
18 | |
19 | #include <sys/random.h> |
20 | #include <assert.h> |
21 | #include <errno.h> |
22 | #include <unistd.h> |
23 | #include <hurd.h> |
24 | |
25 | /* Write LENGTH bytes of randomness starting at BUFFER. Return 0 on |
26 | success and -1 on failure. */ |
27 | int |
28 | getentropy (void *buffer, size_t length) |
29 | { |
30 | /* The interface is documented to return EIO for buffer lengths |
31 | longer than 256 bytes. */ |
32 | if (length > 256) |
33 | return __hurd_fail (EIO); |
34 | |
35 | /* Try to fill the buffer completely. Even with the 256 byte limit |
36 | above, we might still receive an EINTR error (when blocking |
37 | during boot). */ |
38 | void *end = buffer + length; |
39 | while (buffer < end) |
40 | { |
41 | /* NB: No cancellation point. */ |
42 | ssize_t bytes = __getrandom (buffer, end - buffer, 0); |
43 | if (bytes < 0) |
44 | { |
45 | if (errno == EINTR) |
46 | /* Try again if interrupted by a signal. */ |
47 | continue; |
48 | else |
49 | return -1; |
50 | } |
51 | if (bytes == 0) |
52 | /* No more bytes available. This should not happen under |
53 | normal circumstances. */ |
54 | return __hurd_fail (EIO); |
55 | /* Try again in case of a short read. */ |
56 | buffer += bytes; |
57 | } |
58 | return 0; |
59 | } |
60 | |