Add explicit_bzero() function from OpenBSD

include/bsd/string.h

@@ -41,6 +41,8 @@ size_t strlcpy(char *dst, const char *src, size_t siz);
 size_t strlcat(char *dst, const char *src, size_t siz);
 char *strnstr(const char *str, const char *find, size_t str_len);
 void strmode(mode_t mode, char *str);
+
+void explicit_bzero(void *buf, size_t len);
 __END_DECLS
 
 #endif

man/Makefile.am

@@ -23,6 +23,7 @@ dist_man_MANS = \
 	closefrom.3 \
 	dehumanize_number.3 \
 	expand_number.3 \
+	explicit_bzero.3 \
 	fgetln.3 \
 	fgetwln.3 \
 	flopen.3 \

man/explicit_bzero.3

@@ -0,0 +1,72 @@
+.\" Copyright (c) 1990, 1991 The Regents of the University of California.
+.\" All rights reserved.
+.\"
+.\" This code is derived from software contributed to Berkeley by
+.\" Chris Torek.
+.\" Redistribution and use in source and binary forms, with or without
+.\" modification, are permitted provided that the following conditions
+.\" are met:
+.\" 1. Redistributions of source code must retain the above copyright
+.\"    notice, this list of conditions and the following disclaimer.
+.\" 2. Redistributions in binary form must reproduce the above copyright
+.\"    notice, this list of conditions and the following disclaimer in the
+.\"    documentation and/or other materials provided with the distribution.
+.\" 3. Neither the name of the University nor the names of its contributors
+.\"    may be used to endorse or promote products derived from this software
+.\"    without specific prior written permission.
+.\"
+.\" THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND
+.\" ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
+.\" IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
+.\" ARE DISCLAIMED.  IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE
+.\" FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
+.\" DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
+.\" OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
+.\" HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
+.\" LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
+.\" OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
+.\" SUCH DAMAGE.
+.\"
+.\"	$OpenBSD: bzero.3,v 1.10 2014/01/22 21:06:45 tedu Exp $
+.\"
+.Dd $Mdocdate: January 22 2014 $
+.Dt BZERO 3
+.Os
+.Sh NAME
+.Nm explicit_bzero
+.Nd write zeroes to a byte string
+.Sh LIBRARY
+.ds str-Lb-libbsd Utility functions from BSD systems (libbsd, \-lbsd)
+.Lb libbsd
+.Sh SYNOPSIS
+.In bsd/string.h
+.Ft void
+.Fn explicit_bzero "void *buf" "size_t len"
+.Sh DESCRIPTION
+The
+.Fn explicit_bzero
+function writes
+.Fa len
+zero bytes to the string
+.Fa buf .
+If
+.Fa len
+is zero,
+.Fn explicit_bzero
+does nothing.
+.Pp
+The
+.Fn explicit_bzero
+variant behaves the same as the
+.Fn bzero
+function, but will not be removed by a compiler's dead store optimization
+pass, making it useful for clearing sensitive memory such as a password.
+.Sh SEE ALSO
+.Xr bzero 3 ,
+.Xr memset 3 ,
+.Xr swab 3
+.Sh HISTORY
+The
+.Fn explicit_bzero
+function first appeared in
+.Ox 5.5 .

src/Makefile.am

@@ -50,6 +50,7 @@ libbsd_la_SOURCES = \
 	dehumanize_number.c \
 	err.c \
 	expand_number.c \
+	explicit_bzero.c \
 	fgetln.c \
 	fgetwln.c \
 	flopen.c \

src/explicit_bzero.c

@@ -0,0 +1,19 @@
+/*	$OpenBSD: explicit_bzero.c,v 1.3 2014/06/21 02:34:26 matthew Exp $ */
+/*
+ * Public domain.
+ * Written by Matthew Dempsky.
+ */
+
+#include <string.h>
+
+__attribute__((weak)) void
+__explicit_bzero_hook(void *buf, size_t len)
+{
+}
+
+void
+explicit_bzero(void *buf, size_t len)
+{
+	memset(buf, 0, len);
+	__explicit_bzero_hook(buf, len);
+}

src/libbsd.map

@@ -132,3 +132,7 @@ LIBBSD_0.7 {
     _time_to_int;
     _int_to_time;
 } LIBBSD_0.6;
+
+LIBBSD_0.8 {
+    explicit_bzero;
+} LIBBSD_0.7;

test/.gitignore

@@ -1,3 +1,4 @@
+bzero
 closefrom
 endian
 fgetln

test/Makefile.am

@@ -12,6 +12,7 @@ LDADD = $(top_builddir)/src/libbsd.la
 check_PROGRAMS = \
 	headers \
 	overlay \
+	bzero \
 	closefrom \
 	endian \
 	humanize \

test/bzero.c

@@ -0,0 +1,47 @@
+/*
+ * Copyright © 2015 Guillem Jover <guillem@hadrons.org>
+ *
+ * Redistribution and use in source and binary forms, with or without
+ * modification, are permitted provided that the following conditions
+ * are met:
+ * 1. Redistributions of source code must retain the above copyright
+ *    notice, this list of conditions and the following disclaimer.
+ * 2. Redistributions in binary form must reproduce the above copyright
+ *    notice, this list of conditions and the following disclaimer in the
+ *    documentation and/or other materials provided with the distribution.
+ * 3. The name of the author may not be used to endorse or promote products
+ *    derived from this software without specific prior written permission.
+ *
+ * THIS SOFTWARE IS PROVIDED ``AS IS'' AND ANY EXPRESS OR IMPLIED WARRANTIES,
+ * INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY
+ * AND FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED.  IN NO EVENT SHALL
+ * THE AUTHOR BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL,
+ * EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO,
+ * PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS;
+ * OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY,
+ * WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR
+ * OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF
+ * ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
+ */
+
+#include <assert.h>
+#include <string.h>
+
+int
+main()
+{
+	unsigned char array[40];
+	size_t i;
+
+	memset(array, 0x3e, sizeof(array));
+
+	explicit_bzero(array, 0);
+	for (i = 0; i < sizeof(array); i++)
+		assert(array[i] == 0x3e);
+
+	explicit_bzero(array, sizeof(array));
+	for (i = 0; i < sizeof(array); i++)
+		assert(array[i] == 0);
+
+	return 0;
+}