freebsd-dev/libexec/save-entropy/save-entropy.sh

#!/bin/sh
#
# Copyright (c) 2001-2005 Douglas Barton, DougB@FreeBSD.org
# All rights reserved.
#
# 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.
#
# THIS SOFTWARE IS PROVIDED BY THE AUTHOR 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 AUTHOR 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.
#
# $FreeBSD$

# This script is called by cron to store bits of randomness which are
# then used to seed /dev/random on boot.

# Originally developed by Doug Barton, DougB@FreeBSD.org

PATH=/bin:/usr/bin

# If there is a global system configuration file, suck it in.
#
if [ -r /etc/defaults/rc.conf ]; then
	. /etc/defaults/rc.conf
	source_rc_confs
elif [ -r /etc/rc.conf ]; then
	. /etc/rc.conf
fi

case ${entropy_dir} in
[Nn][Oo])
	exit 0
	;;
*)
	entropy_dir=${entropy_dir:-/var/db/entropy}
	;;
esac

entropy_save_sz=${entropy_save_sz:-2048}
entropy_save_num=${entropy_save_num:-8}

if [ ! -d "${entropy_dir}" ]; then
	umask 077
	mkdir "${entropy_dir}" || {
	    logger -is -t "$0" The entropy directory "${entropy_dir}" does not \
exist, and cannot be created.  Therefore no entropy can be saved. ;
	    exit 1;}
	/usr/sbin/chown operator:operator "${entropy_dir}"
	chmod 0700 "${entropy_dir}"
fi

umask 377

for file_num in `jot ${entropy_save_num} ${entropy_save_num} 1`; do
	if [ -e "${entropy_dir}/saved-entropy.${file_num}" ]; then
		if [ -f "${entropy_dir}/saved-entropy.${file_num}" ]; then
			new_num=$(($file_num + 1))
			if [ "${new_num}" -gt "${entropy_save_num}" ]; then
				rm -f "${entropy_dir}/saved-entropy.${file_num}"
			else
				mv "${entropy_dir}/saved-entropy.${file_num}" \
				    "${entropy_dir}/saved-entropy.${new_num}"
			fi
		else
			logger -is -t "$0" \
"${entropy_dir}/saved-entropy.${file_num} is not a regular file, and therefore \
it will not be rotated. Entropy file harvesting is aborted."
			exit 1
		fi
	fi
done

dd if=/dev/random of="${entropy_dir}/saved-entropy.1" \
    bs="$entropy_save_sz" count=1 2> /dev/null

exit 0