| /* Implementation of getentropy based on the getrandom system call. |
| Copyright (C) 2016-2018 Free Software Foundation, Inc. |
| This file is part of the GNU C Library. |
| |
| The GNU C Library is free software; you can redistribute it and/or |
| modify it under the terms of the GNU Lesser General Public |
| License as published by the Free Software Foundation; either |
| version 2.1 of the License, or (at your option) any later version. |
| |
| The GNU C Library is distributed in the hope that it will be useful, |
| but WITHOUT ANY WARRANTY; without even the implied warranty of |
| MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU |
| Lesser General Public License for more details. |
| |
| You should have received a copy of the GNU Lesser General Public |
| License along with the GNU C Library; if not, see |
| <http://www.gnu.org/licenses/>. */ |
| |
| #include <sys/random.h> |
| #include <assert.h> |
| #include <errno.h> |
| #include <unistd.h> |
| |
| #ifdef __NR_getrandom |
| /* Write LENGTH bytes of randomness starting at BUFFER. Return 0 on |
| success and -1 on failure. */ |
| int |
| getentropy (void *buffer, size_t length) |
| { |
| /* The interface is documented to return EIO for buffer lengths |
| longer than 256 bytes. */ |
| if (length > 256) |
| { |
| __set_errno (EIO); |
| return -1; |
| } |
| |
| /* Try to fill the buffer completely. Even with the 256 byte limit |
| above, we might still receive an EINTR error (when blocking |
| during boot). */ |
| void *end = buffer + length; |
| while (buffer < end) |
| { |
| /* NB: No cancellation point. */ |
| ssize_t bytes = INLINE_SYSCALL_CALL (getrandom, buffer, end - buffer, 0); |
| if (bytes < 0) |
| { |
| if (errno == EINTR) |
| /* Try again if interrupted by a signal. */ |
| continue; |
| else |
| return -1; |
| } |
| if (bytes == 0) |
| { |
| /* No more bytes available. This should not happen under |
| normal circumstances. */ |
| __set_errno (EIO); |
| return -1; |
| } |
| /* Try again in case of a short read. */ |
| buffer += bytes; |
| } |
| return 0; |
| } |
| #else |
| int |
| getentropy (void *buffer, size_t length) |
| { |
| __set_errno (ENOSYS); |
| return -1; |
| } |
| #endif |
