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trezor-firmware/crypto/memzero.c

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#ifndef __STDC_WANT_LIB_EXT1__
#define __STDC_WANT_LIB_EXT1__ 1 // C11's bounds-checking interface.
#endif
#include <string.h>
#ifdef _WIN32
#include <windows.h>
#endif
#ifdef __unix__
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#include <strings.h>
#include <sys/param.h>
#endif
// C11's bounds-checking interface.
#if defined(__STDC_LIB_EXT1__)
#define HAVE_MEMSET_S 1
#endif
// GNU C Library version 2.25 or later.
#if defined(__GLIBC__) && \
(__GLIBC__ > 2 || (__GLIBC__ == 2 && __GLIBC_MINOR__ >= 25))
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#define HAVE_EXPLICIT_BZERO 1
#endif
// Newlib
#if defined(__NEWLIB__)
#define HAVE_EXPLICIT_BZERO 1
#endif
// FreeBSD version 11.0 or later.
#if defined(__FreeBSD__) && __FreeBSD_version >= 1100037
#define HAVE_EXPLICIT_BZERO 1
#endif
// OpenBSD version 5.5 or later.
#if defined(__OpenBSD__) && OpenBSD >= 201405
#define HAVE_EXPLICIT_BZERO 1
#endif
// NetBSD version 7.2 or later.
#if defined(__NetBSD__) && __NetBSD_Version__ >= 702000000
#define HAVE_EXPLICIT_MEMSET 1
#endif
// Adapted from
// https://github.com/jedisct1/libsodium/blob/1647f0d53ae0e370378a9195477e3df0a792408f/src/libsodium/sodium/utils.c#L102-L130
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void memzero(void *const pnt, const size_t len) {
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#ifdef _WIN32
SecureZeroMemory(pnt, len);
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#elif defined(HAVE_MEMSET_S)
memset_s(pnt, (rsize_t)len, 0, (rsize_t)len);
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#elif defined(HAVE_EXPLICIT_BZERO)
explicit_bzero(pnt, len);
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#elif defined(HAVE_EXPLICIT_MEMSET)
explicit_memset(pnt, 0, len);
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#else
volatile unsigned char *volatile pnt_ = (volatile unsigned char *volatile)pnt;
size_t i = (size_t)0U;
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while (i < len) {
pnt_[i++] = 0U;
}
#endif
// explicitly mark the memory as overwritten for the Clang MemorySanitizer
// this is only included at compile time if MemorySanitizer is enabled and
// should not come with any downsides during regular builds
#if defined(__has_feature)
#if __has_feature(memory_sanitizer)
memset(pnt, 0, len);
#endif
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#endif
}