1 files changed, 57 insertions, 0 deletions
diff --git a/bsd/freebsd/contrib/ntp/lib/isc/tsmemcmp.c b/bsd/freebsd/contrib/ntp/lib/isc/tsmemcmp.c
new file mode 100644
index 0000000..781612c
--- /dev/null
+++ b/bsd/freebsd/contrib/ntp/lib/isc/tsmemcmp.c
@@ -0,0 +1,57 @@
+#include <machine/rtems-bsd-user-space.h>
+
+/*
+ * Copyright (C) 2004-2007, 2011, 2012  Internet Systems Consortium, Inc. ("ISC")
+ * Copyright (C) 1999-2001, 2003  Internet Software Consortium.
+ *
+ * Permission to use, copy, modify, and/or distribute this software for any
+ * purpose with or without fee is hereby granted, provided that the above
+ * copyright notice and this permission notice appear in all copies.
+ *
+ * THE SOFTWARE IS PROVIDED "AS IS" AND ISC DISCLAIMS ALL WARRANTIES WITH
+ * REGARD TO THIS SOFTWARE INCLUDING ALL IMPLIED WARRANTIES OF MERCHANTABILITY
+ * AND FITNESS.  IN NO EVENT SHALL ISC BE LIABLE FOR ANY SPECIAL, DIRECT,
+ * INDIRECT, OR CONSEQUENTIAL DAMAGES OR ANY DAMAGES WHATSOEVER RESULTING FROM
+ * LOSS OF USE, DATA OR PROFITS, WHETHER IN AN ACTION OF CONTRACT, NEGLIGENCE
+ * OR OTHER TORTIOUS ACTION, ARISING OUT OF OR IN CONNECTION WITH THE USE OR
+ * PERFORMANCE OF THIS SOFTWARE.
+ */
+
+/* $Id$ */
+
+/*! \file */
+
+#include <config.h>
+#include <limits.h>
+#include <isc/string.h>
+
+/* Making a portable memcmp that has no internal branches and loops always
+ * once for every byte without early-out shortcut has a few challenges.
+ *
+ * Inspired by 'timingsafe_memcmp()' from the BSD system and
+ * https://github.com/libressl-portable/openbsd/blob/master/src/lib/libc/string/timingsafe_memcmp.c
+ *
+ * Sadly, that one is not portable C: It makes assumptions on the representation
+ * of negative integers and assumes sign-preserving right-shift of negative
+ * signed values. This is a rewrite from scratch that should not suffer from
+ * such issues.
+ *
+ * 2015-12-12, J. Perlinger (perlinger-at-ntp-dot-org)
+ */
+int
+isc_tsmemcmp(const void *p1, const void *p2, size_t nb) {
+	const unsigned char *ucp1 = p1;
+	const unsigned char *ucp2 = p2;
+	unsigned int isLT = 0u;
+	unsigned int isGT = 0u;
+	volatile unsigned int mask = (1u << CHAR_BIT);
+
+	for (/*NOP*/; 0 != nb; --nb, ++ucp1, ++ucp2) {
+		isLT |= mask &
+		    ((unsigned int)*ucp1 - (unsigned int)*ucp2);
+		isGT |= mask &
+		    ((unsigned int)*ucp2 - (unsigned int)*ucp1);
+		mask &= ~(isLT | isGT);
+	}
+	return (int)(isGT >> CHAR_BIT) - (int)(isLT >> CHAR_BIT);
+}