Add timingsafe_bcmp()

This function is used by LibreSSL and OpenSSH and is provided by the
OpenBSD libc.

	* libc/include/string.h (timingsafe_bcmp): Declare.
	* libc/string/timingsafe_bcmp.c: New file.
	* libc/string/Makefile.am: Add new file.
	* libc/string/Makefile.in: Regenerate.

1 files changed, 29 insertions, 0 deletions

diff --git a/newlib/libc/string/timingsafe_bcmp.c b/newlib/libc/string/timingsafe_bcmp.c
new file mode 100644
index 000000000..0b736154c
--- /dev/null
+++ b/newlib/libc/string/timingsafe_bcmp.c
@@ -0,0 +1,29 @@
+/*	$OpenBSD: timingsafe_bcmp.c,v 1.2 2014/06/10 04:17:37 deraadt Exp $	*/
+/*
+ * Copyright (c) 2010 Damien Miller.  All rights reserved.
+ *
+ * Permission to use, copy, modify, and 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 THE AUTHOR DISCLAIMS ALL WARRANTIES
+ * WITH REGARD TO THIS SOFTWARE INCLUDING ALL IMPLIED WARRANTIES OF
+ * MERCHANTABILITY AND FITNESS. IN NO EVENT SHALL THE AUTHOR 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.
+ */
+
+#include <string.h>
+
+int
+timingsafe_bcmp(const void *b1, const void *b2, size_t n)
+{
+	const unsigned char *p1 = b1, *p2 = b2;
+	int ret = 0;
+
+	for (; n > 0; n--)
+		ret |= *p1++ ^ *p2++;
+	return (ret != 0);
+}