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openbsd-compat/explicit_bzero.c

@@ -0,0 +1,57 @@
+/* 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 "openbsd-compat.h"
+
+#if !defined(HAVE_EXPLICIT_BZERO) && !defined(_WIN32)
+
+#include <string.h>
+
+/*
+ * explicit_bzero - don't let the compiler optimize away bzero
+ */
+
+#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 /* !defined(HAVE_EXPLICIT_BZERO) && !defined(_WIN32) */