explicit_bzero.c

/* OPENBSD ORIGINAL: lib/libc/string/explicit_bzero.c */
/*	$OpenBSD: explicit_bzero.c,v 1.1 2014/01/22 21:06:45 tedu Exp $ */
/*
 * Public domain.
 * Written by Ted Unangst
 */

#include <string.h>

/*
 * explicit_bzero - don't let the compiler optimize away bzero
 */

#ifndef HAVE_EXPLICIT_BZERO

#include "util.h"

#ifdef HAVE_MEMSET_S

void explicit_bzero(void *p, size_t n) {
  if (n == 0)
    return;
  (void) memset_s(p, n, 0, n);
}

#else /* HAVE_MEMSET_S */

/*
 * Indirect bzero through a volatile pointer to hopefully avoid
 * dead-store optimisation eliminating the call.
 */
static void (*volatile ssh_bzero)(void *, size_t) = bzero;

void explicit_bzero(void *p, size_t n) {
  if (n == 0)
    return;
    /*
     * clang -fsanitize=memory needs to intercept memset-like functions
     * to correctly detect memory initialisation. Make sure one is called
     * directly since our indirection trick above successfully confuses it.
     */
#if defined(__has_feature)
#if __has_feature(memory_sanitizer)
  memset(p, 0, n);
#endif
#endif

  ssh_bzero(p, n);
}

#endif /* HAVE_MEMSET_S */

#endif /* HAVE_EXPLICIT_BZERO */