Bitcoin Core  0.19.99
P2P Digital Currency
cleanse.cpp
Go to the documentation of this file.
1 // Copyright (c) 2009-2010 Satoshi Nakamoto
2 // Copyright (c) 2009-2019 The Bitcoin Core developers
3 // Distributed under the MIT software license, see the accompanying
4 // file COPYING or http://www.opensource.org/licenses/mit-license.php.
5 
6 #include <support/cleanse.h>
7 
8 #include <cstring>
9 
10 #if defined(_MSC_VER)
11 #include <Windows.h> // For SecureZeroMemory.
12 #endif
13 
14 void memory_cleanse(void *ptr, size_t len)
15 {
16 #if defined(_MSC_VER)
17  /* SecureZeroMemory is guaranteed not to be optimized out by MSVC. */
18  SecureZeroMemory(ptr, len);
19 #else
20  std::memset(ptr, 0, len);
21 
22  /* Memory barrier that scares the compiler away from optimizing out the memset.
23  *
24  * Quoting Adam Langley <agl@google.com> in commit ad1907fe73334d6c696c8539646c21b11178f20f
25  * in BoringSSL (ISC License):
26  * As best as we can tell, this is sufficient to break any optimisations that
27  * might try to eliminate "superfluous" memsets.
28  * This method is used in memzero_explicit() the Linux kernel, too. Its advantage is that it
29  * is pretty efficient because the compiler can still implement the memset() efficiently,
30  * just not remove it entirely. See "Dead Store Elimination (Still) Considered Harmful" by
31  * Yang et al. (USENIX Security 2017) for more background.
32  */
33  __asm__ __volatile__("" : : "r"(ptr) : "memory");
34 #endif
35 }
void memory_cleanse(void *ptr, size_t len)
Secure overwrite a buffer (possibly containing secret data) with zero-bytes.
Definition: cleanse.cpp:14