// Copyright (c) 2017-2020, The Monero Project
//
// All rights reserved.
//
// Redistribution and use in source and binary forms, with or without modification, are
// permitted provided that the following conditions are met:
//
// 1. Redistributions of source code must retain the above copyright notice, this list of
// conditions and the following disclaimer.
//
// 2. Redistributions in binary form must reproduce the above copyright notice, this list
// of conditions and the following disclaimer in the documentation and/or other
// materials provided with the distribution.
//
// 3. Neither the name of the copyright holder nor the names of its contributors may be
// used to endorse or promote products derived from this software without specific
// prior written permission.
//
// THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS IS" AND ANY
// EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES OF
// MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL
// THE COPYRIGHT HOLDER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
// SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO,
// PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS
// INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT,
// STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF
// THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
//
// Parts of this file Copyright (c) 2009-2015 The Bitcoin Core developers
#define __STDC_WANT_LIB_EXT1__ 1
#include <string.h>
#include <stdlib.h>
#include <stdio.h>
#include <unistd.h>
#ifdef HAVE_EXPLICIT_BZERO
#include <strings.h>
#endif
#include "memwipe.h"
#if defined(_MSC_VER)
#define SCARECROW \
__asm;
#else
#define SCARECROW \
__asm__ __volatile__("" : : "r"(ptr) : "memory");
#endif
#ifdef HAVE_MEMSET_S
void *memwipe(void *ptr, size_t n)
{
if (n > 0 && memset_s(ptr, n, 0, n))
{
#ifdef NDEBUG
fprintf(stderr, "Error: memset_s failed\n");
_exit(1);
#else
abort();
#endif
}
SCARECROW // might as well...
return ptr;
}
#elif defined HAVE_EXPLICIT_BZERO
void *memwipe(void *ptr, size_t n)
{
if (n > 0)
explicit_bzero(ptr, n);
SCARECROW
return ptr;
}
#else
/* The memory_cleanse implementation is taken from Bitcoin */
/* Compilers have a bad habit of removing "superfluous" memset calls that
* are trying to zero memory. For example, when memset()ing a buffer and
* then free()ing it, the compiler might decide that the memset is
* unobservable and thus can be removed.
*
* Previously we used OpenSSL which tried to stop this by a) implementing
* memset in assembly on x86 and b) putting the function in its own file
* for other platforms.
*
* This change removes those tricks in favour of using asm directives to
* scare the compiler away. As best as our compiler folks can tell, this is
* sufficient and will continue to be so.
*
* Adam Langley <agl@google.com>
* Commit: ad1907fe73334d6c696c8539646c21b11178f20f
* BoringSSL (LICENSE: ISC)
*/
static void memory_cleanse(void *ptr, size_t len)
{
memset(ptr, 0, len);
/* As best as we can tell, this is sufficient to break any optimisations that
might try to eliminate "superfluous" memsets. If there's an easy way to
detect memset_s, it would be better to use that. */
SCARECROW
}
void *memwipe(void *ptr, size_t n)
{
if (n > 0)
memory_cleanse(ptr, n);
SCARECROW
return ptr;
}
#endif
