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658b5848a8
Due to the built-in tables, __NR_getrandom is always defined. Reviewed-by: Adhemerval Zanella <adhemerval.zanella@linaro.org>
65 lines
2.0 KiB
C
65 lines
2.0 KiB
C
/* Implementation of getentropy based on the getrandom system call.
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Copyright (C) 2016-2020 Free Software Foundation, Inc.
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This file is part of the GNU C Library.
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The GNU C Library is free software; you can redistribute it and/or
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modify it under the terms of the GNU Lesser General Public
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License as published by the Free Software Foundation; either
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version 2.1 of the License, or (at your option) any later version.
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The GNU C Library is distributed in the hope that it will be useful,
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but WITHOUT ANY WARRANTY; without even the implied warranty of
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MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
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Lesser General Public License for more details.
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You should have received a copy of the GNU Lesser General Public
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License along with the GNU C Library; if not, see
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<https://www.gnu.org/licenses/>. */
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#include <sys/random.h>
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#include <assert.h>
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#include <errno.h>
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#include <unistd.h>
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/* Write LENGTH bytes of randomness starting at BUFFER. Return 0 on
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success and -1 on failure. */
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int
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getentropy (void *buffer, size_t length)
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{
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/* The interface is documented to return EIO for buffer lengths
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longer than 256 bytes. */
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if (length > 256)
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{
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__set_errno (EIO);
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return -1;
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}
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/* Try to fill the buffer completely. Even with the 256 byte limit
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above, we might still receive an EINTR error (when blocking
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during boot). */
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void *end = buffer + length;
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while (buffer < end)
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{
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/* NB: No cancellation point. */
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ssize_t bytes = INLINE_SYSCALL_CALL (getrandom, buffer, end - buffer, 0);
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if (bytes < 0)
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{
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if (errno == EINTR)
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/* Try again if interrupted by a signal. */
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continue;
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else
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return -1;
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}
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if (bytes == 0)
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{
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/* No more bytes available. This should not happen under
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normal circumstances. */
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__set_errno (EIO);
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return -1;
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}
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/* Try again in case of a short read. */
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buffer += bytes;
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}
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return 0;
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}
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