diff --git a/include/string.h b/include/string.h
index af8b0d46c86c..9fe1f826d9cd 100644
--- a/include/string.h
+++ b/include/string.h
@@ -134,6 +134,8 @@ typedef	__ssize_t	ssize_t;
 void	 swab(const void * __restrict, void * __restrict, ssize_t);
 #endif /* _SWAB_DECLARED */
 
+int	 timingsafe_bcmp(const void *, const void *, size_t);
+int	 timingsafe_memcmp(const void *, const void *, size_t);
 #endif /* __BSD_VISIBLE */
 
 #if __POSIX_VISIBLE >= 200809 || defined(_XLOCALE_H_)
diff --git a/lib/libc/string/Makefile.inc b/lib/libc/string/Makefile.inc
index 1217b7bc82d2..7b2b9b734808 100644
--- a/lib/libc/string/Makefile.inc
+++ b/lib/libc/string/Makefile.inc
@@ -16,7 +16,10 @@ MISRCS+=bcmp.c bcopy.c bzero.c explicit_bzero.c \
 	strcspn.c strdup.c strerror.c strlcat.c strlcpy.c strlen.c strmode.c \
 	strncat.c strncmp.c strncpy.c strndup.c strnlen.c strnstr.c \
 	strpbrk.c strrchr.c strsep.c strsignal.c strspn.c strstr.c strtok.c \
-	strxfrm.c swab.c wcpcpy.c wcpncpy.c wcscasecmp.c wcscat.c \
+	strxfrm.c swab.c \
+	timingsafe_bcmp.c \
+	timingsafe_memcmp.c \
+	wcpcpy.c wcpncpy.c wcscasecmp.c wcscat.c \
 	wcschr.c wcscmp.c wcscoll.c wcscpy.c wcscspn.c wcsdup.c \
 	wcslcat.c wcslcpy.c wcslen.c wcsncasecmp.c wcsncat.c wcsncmp.c \
 	wcsncpy.c wcsnlen.c wcspbrk.c \
@@ -34,7 +37,9 @@ MAN+=	bcmp.3 bcopy.3 bstring.3 bzero.3 ffs.3 index.3 memccpy.3 memchr.3 \
 	memcmp.3 memcpy.3 memmem.3 memmove.3 memset.3 strcasecmp.3 strcat.3 \
 	strchr.3 strcmp.3 strcoll.3 strcpy.3 strdup.3 strerror.3 \
 	string.3 strlcpy.3 strlen.3 strmode.3 strpbrk.3 strsep.3 \
-	strspn.3 strstr.3 strtok.3 strxfrm.3 swab.3 wcscoll.3 wcstok.3 \
+	strspn.3 strstr.3 strtok.3 strxfrm.3 swab.3 \
+	timingsafe_bcmp.3 \
+	wcscoll.3 wcstok.3 \
 	wcswidth.3 wcsxfrm.3 wmemchr.3
 
 MLINKS+=bzero.3 explicit_bzero.3
@@ -69,6 +74,7 @@ MLINKS+=strstr.3 strcasestr.3 \
 	strstr.3 strcasestr_l.3
 MLINKS+=strtok.3 strtok_r.3
 MLINKS+=strxfrm.3 strxfrm_l.3
+MLINKS+=timingsafe_bcmp.3 timingsafe_memcmp.3
 MLINKS+=wmemchr.3 wcpcpy.3 \
 	wmemchr.3 wcpncpy.3 \
 	wmemchr.3 wcscasecmp.3 \
diff --git a/lib/libc/string/Symbol.map b/lib/libc/string/Symbol.map
index 59610925fe33..cbf80cf9751c 100644
--- a/lib/libc/string/Symbol.map
+++ b/lib/libc/string/Symbol.map
@@ -104,6 +104,11 @@ FBSD_1.4 {
 	explicit_bzero;
 };
 
+FBSD_1.5 {
+	timingsafe_bcmp;
+	timingsafe_memcmp;
+};
+
 FBSDprivate_1.0 {
 	__strtok_r;
 };
diff --git a/lib/libc/string/bcmp.3 b/lib/libc/string/bcmp.3
index fa5666c57ea0..e2d4063a1654 100644
--- a/lib/libc/string/bcmp.3
+++ b/lib/libc/string/bcmp.3
@@ -30,7 +30,7 @@
 .\"     @(#)bcmp.3	8.1 (Berkeley) 6/4/93
 .\" $FreeBSD$
 .\"
-.Dd June 4, 1993
+.Dd August 15, 2016
 .Dt BCMP 3
 .Os
 .Sh NAME
@@ -62,7 +62,8 @@ The strings may overlap.
 .Xr strcasecmp 3 ,
 .Xr strcmp 3 ,
 .Xr strcoll 3 ,
-.Xr strxfrm 3
+.Xr strxfrm 3 ,
+.Xr timingsafe_bcmp 3
 .Sh HISTORY
 A
 .Fn bcmp
diff --git a/lib/libc/string/memcmp.3 b/lib/libc/string/memcmp.3
index 00e8e1a1d759..245e2abe1d71 100644
--- a/lib/libc/string/memcmp.3
+++ b/lib/libc/string/memcmp.3
@@ -32,7 +32,7 @@
 .\"     @(#)memcmp.3	8.1 (Berkeley) 6/4/93
 .\" $FreeBSD$
 .\"
-.Dd June 4, 1993
+.Dd August 15, 2016
 .Dt MEMCMP 3
 .Os
 .Sh NAME
@@ -75,6 +75,7 @@ Zero-length strings are always identical.
 .Xr strcmp 3 ,
 .Xr strcoll 3 ,
 .Xr strxfrm 3 ,
+.Xr timingsafe_memcmp 3 ,
 .Xr wmemcmp 3
 .Sh STANDARDS
 The
diff --git a/lib/libc/string/timingsafe_bcmp.3 b/lib/libc/string/timingsafe_bcmp.3
new file mode 100644
index 000000000000..502e57176806
--- /dev/null
+++ b/lib/libc/string/timingsafe_bcmp.3
@@ -0,0 +1,92 @@
+.\"	$OpenBSD: timingsafe_bcmp.3,v 1.2 2014/06/21 20:22:15 tedu Exp $
+.\"
+.\" Copyright (c) 2014 Google Inc.
+.\"
+.\" 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.
+.\"
+.\" $FreeBSD$
+.Dd August 15, 2016
+.Dt TIMINGSAFE_BCMP 3
+.Os
+.Sh NAME
+.Nm timingsafe_bcmp ,
+.Nm timingsafe_memcmp
+.Nd timing-safe byte sequence comparisons
+.Sh SYNOPSIS
+.In string.h
+.Ft int
+.Fn timingsafe_bcmp "const void *b1" "const void *b2" "size_t len"
+.Ft int
+.Fn timingsafe_memcmp "const void *b1" "const void *b2" "size_t len"
+.Sh DESCRIPTION
+The
+.Fn timingsafe_bcmp
+and
+.Fn timingsafe_memcmp
+functions lexicographically compare the first
+.Fa len
+bytes (each interpreted as an
+.Vt unsigned char )
+pointed to by
+.Fa b1
+and
+.Fa b2 .
+.Pp
+Additionally, their running times are independent of the byte sequences compared,
+making them safe to use for comparing secret values such as cryptographic MACs.
+In contrast,
+.Xr bcmp 3
+and
+.Xr memcmp 3
+may short-circuit after finding the first differing byte.
+.Sh RETURN VALUES
+The
+.Fn timingsafe_bcmp
+function returns 0 or not zero if the byte sequence pointed to by
+.Fa b1
+compares equal to or not equal to (respectively)
+the byte sequence pointed to by
+.Fa b2 .
+.Pp
+The
+.Fn timingsafe_memcmp
+function returns a negative value, 0, or positive value if the byte sequence
+pointed to by
+.Fa b1
+compares less than, equal to, or greater than (respectively)
+the byte sequence pointed to by
+.Fa b2 .
+.Sh SEE ALSO
+.Xr bcmp 3 ,
+.Xr memcmp 3
+.Sh STANDARDS
+The
+.Fn timingsafe_bcmp
+and
+.Fn timingsafe_memcmp
+functions are
+.Fx
+extensions.
+.Sh HISTORY
+The
+.Fn timingsafe_bcmp
+function first appeared in
+.Ox 4.9 .
+.Pp
+The
+.Fn timingsafe_memcmp
+function first appeared in
+.Ox 5.6 .
+.Pp
+Both functions first appeared in
+.Fx 12.0 .
diff --git a/lib/libc/string/timingsafe_bcmp.c b/lib/libc/string/timingsafe_bcmp.c
new file mode 100644
index 000000000000..d098158059f3
--- /dev/null
+++ b/lib/libc/string/timingsafe_bcmp.c
@@ -0,0 +1,36 @@
+/*	$OpenBSD: timingsafe_bcmp.c,v 1.3 2015/08/31 02:53:57 guenther 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 <sys/cdefs.h>
+__FBSDID("$FreeBSD$");
+
+#include <string.h>
+
+int __timingsafe_bcmp(const void *, const void *, size_t);
+
+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);
+}
+
+__weak_reference(__timingsafe_bcmp, timingsafe_bcmp);
diff --git a/lib/libc/string/timingsafe_memcmp.c b/lib/libc/string/timingsafe_memcmp.c
new file mode 100644
index 000000000000..7abfb48045f8
--- /dev/null
+++ b/lib/libc/string/timingsafe_memcmp.c
@@ -0,0 +1,53 @@
+/*	$OpenBSD: timingsafe_memcmp.c,v 1.2 2015/08/31 02:53:57 guenther Exp $	*/
+/*
+ * Copyright (c) 2014 Google Inc.
+ *
+ * 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 <sys/cdefs.h>
+__FBSDID("$FreeBSD$");
+
+#include <limits.h>
+#include <string.h>
+
+int __timingsafe_memcmp(const void *, const void *, size_t);
+
+int
+__timingsafe_memcmp(const void *b1, const void *b2, size_t len)
+{
+        const unsigned char *p1 = b1, *p2 = b2;
+        size_t i;
+        int res = 0, done = 0;
+
+        for (i = 0; i < len; i++) {
+                /* lt is -1 if p1[i] < p2[i]; else 0. */
+                int lt = (p1[i] - p2[i]) >> CHAR_BIT;
+
+                /* gt is -1 if p1[i] > p2[i]; else 0. */
+                int gt = (p2[i] - p1[i]) >> CHAR_BIT;
+
+                /* cmp is 1 if p1[i] > p2[i]; -1 if p1[i] < p2[i]; else 0. */
+                int cmp = lt - gt;
+
+                /* set res = cmp if !done. */
+                res |= cmp & ~done;
+
+                /* set done if p1[i] != p2[i]. */
+                done |= lt | gt;
+        }
+
+        return (res);
+}
+
+__weak_reference(__timingsafe_memcmp, timingsafe_memcmp);