104 lines
3.0 KiB
C
104 lines
3.0 KiB
C
/*-
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* SPDX-License-Identifier: BSD-2-Clause-FreeBSD
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*
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* Copyright (c) 2018 Conrad Meyer <cem@FreeBSD.org>
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* All rights reserved.
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*
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* Redistribution and use in source and binary forms, with or without
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* modification, are permitted provided that the following conditions
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* are met:
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* 1. Redistributions of source code must retain the above copyright
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* notice, this list of conditions and the following disclaimer.
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* 2. Redistributions in binary form must reproduce the above copyright
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* notice, this list of conditions and the following disclaimer in the
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* documentation and/or other materials provided with the distribution.
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*
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* THIS SOFTWARE IS PROVIDED BY THE AUTHOR AND CONTRIBUTORS ``AS IS'' AND
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* ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
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* IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
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* ARE DISCLAIMED. IN NO EVENT SHALL THE AUTHOR OR CONTRIBUTORS BE LIABLE
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* FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
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* DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
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* OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
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* HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
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* LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
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* OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
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* SUCH DAMAGE.
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*/
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#include <sys/cdefs.h>
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__FBSDID("$FreeBSD$");
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#include <sys/param.h>
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#include <sys/random.h>
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#include <errno.h>
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#include <stdlib.h>
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#include "libc_private.h"
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/*
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* If a newer libc is accidentally installed on an older kernel, provide high
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* quality random data anyway. The sysctl interface is not as fast and does
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* not block by itself, but is provided by even very old kernels.
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*/
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static int
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getentropy_fallback(void *buf, size_t buflen)
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{
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/*
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* oldp (buf) == NULL has a special meaning for sysctl that results in
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* no EFAULT. For compatibility with the kernel getrandom(2), detect
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* this case and return the appropriate error.
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*/
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if (buf == NULL && buflen > 0) {
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errno = EFAULT;
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return (-1);
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}
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if (__arc4_sysctl(buf, buflen) != buflen) {
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if (errno == EFAULT)
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return (-1);
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/*
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* This cannot happen. _arc4_sysctl() spins until the random
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* device is seeded and then repeatedly reads until the full
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* request is satisfied. The only way for this to return a zero
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* byte or short read is if sysctl(2) on the kern.arandom MIB
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* fails. In this case, exceping the user-provided-a-bogus-
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* buffer EFAULT, give up (like for arc4random(3)'s arc4_stir).
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*/
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abort();
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}
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return (0);
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}
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int
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getentropy(void *buf, size_t buflen)
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{
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ssize_t rd;
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if (buflen > 256) {
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errno = EIO;
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return (-1);
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}
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while (buflen > 0) {
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rd = getrandom(buf, buflen, 0);
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if (rd == -1) {
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if (errno == EINTR)
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continue;
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else if (errno == ENOSYS || errno == ECAPMODE)
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return (getentropy_fallback(buf, buflen));
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else
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return (-1);
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}
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/* This cannot happen. */
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if (rd == 0)
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abort();
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buf = (char *)buf + rd;
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buflen -= rd;
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}
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return (0);
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}
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