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115 lines
3.6 KiB
C
115 lines
3.6 KiB
C
// Copyright (c) 2017-2018, The Monero Project
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//
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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 modification, are
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// permitted provided that the following conditions are met:
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//
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// 1. Redistributions of source code must retain the above copyright notice, this list of
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// conditions and the following disclaimer.
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//
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// 2. Redistributions in binary form must reproduce the above copyright notice, this list
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// of conditions and the following disclaimer in the documentation and/or other
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// materials provided with the distribution.
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//
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// 3. Neither the name of the copyright holder nor the names of its contributors may be
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// used to endorse or promote products derived from this software without specific
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// prior written permission.
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//
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// THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS IS" AND ANY
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// EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES OF
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// MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL
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// THE COPYRIGHT HOLDER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
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// SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO,
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// PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS
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// INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT,
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// STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF
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// THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
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//
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// Parts of this file Copyright (c) 2009-2015 The Bitcoin Core developers
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#define __STDC_WANT_LIB_EXT1__ 1
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#include <string.h>
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#include <stdlib.h>
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#include <stdio.h>
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#include <unistd.h>
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#ifdef HAVE_EXPLICIT_BZERO
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#include <strings.h>
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#endif
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#include "memwipe.h"
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#if defined(_MSC_VER)
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#define SCARECROW \
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__asm;
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#else
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#define SCARECROW \
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__asm__ __volatile__("" : : "r"(ptr) : "memory");
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#endif
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#ifdef HAVE_MEMSET_S
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void *memwipe(void *ptr, size_t n)
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{
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if (n > 0 && memset_s(ptr, n, 0, n))
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{
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#ifdef NDEBUG
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fprintf(stderr, "Error: memset_s failed\n");
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_exit(1);
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#else
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abort();
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#endif
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}
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SCARECROW // might as well...
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return ptr;
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}
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#elif defined HAVE_EXPLICIT_BZERO
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void *memwipe(void *ptr, size_t n)
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{
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if (n > 0)
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explicit_bzero(ptr, n);
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SCARECROW
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return ptr;
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}
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#else
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/* The memory_cleanse implementation is taken from Bitcoin */
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/* Compilers have a bad habit of removing "superfluous" memset calls that
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* are trying to zero memory. For example, when memset()ing a buffer and
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* then free()ing it, the compiler might decide that the memset is
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* unobservable and thus can be removed.
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*
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* Previously we used OpenSSL which tried to stop this by a) implementing
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* memset in assembly on x86 and b) putting the function in its own file
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* for other platforms.
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*
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* This change removes those tricks in favour of using asm directives to
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* scare the compiler away. As best as our compiler folks can tell, this is
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* sufficient and will continue to be so.
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*
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* Adam Langley <agl@google.com>
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* Commit: ad1907fe73334d6c696c8539646c21b11178f20f
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* BoringSSL (LICENSE: ISC)
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*/
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static void memory_cleanse(void *ptr, size_t len)
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{
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memset(ptr, 0, len);
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/* As best as we can tell, this is sufficient to break any optimisations that
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might try to eliminate "superfluous" memsets. If there's an easy way to
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detect memset_s, it would be better to use that. */
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SCARECROW
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}
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void *memwipe(void *ptr, size_t n)
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{
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if (n > 0)
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memory_cleanse(ptr, n);
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SCARECROW
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return ptr;
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}
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#endif
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