freebsd-dev/libexec/save-entropy/save-entropy.sh
Doug Barton e8ea7f0260 1. Attempt to take one bullet out of the foot-shooting gun by silently
ignoring errors when sourcing rc.conf* files. The most common error
occurs when users put a command of some sort into those files.
(ifconfig is a popular choice)

2. Make the file rotation logic simpler by starting one down from
the "top" of the list, rather than at the top.

3. Try to make file rotation more secure by calling unlink(1) on all
new file names before rotating an old file to the new name, rather than
merely calling 'rm -f' on any files that exceed the number of files
to save.
2006-08-28 06:41:50 +00:00

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#!/bin/sh
#
# Copyright (c) 2001-2006 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 2>/dev/null
elif [ -r /etc/rc.conf ]; then
. /etc/rc.conf 2>/dev/null
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
esn_m1=$(( ${entropy_save_num} - 1 ))
for file_num in `jot $esn_m1 $esn_m1 1`; do
if [ -e "${entropy_dir}/saved-entropy.${file_num}" ]; then
if [ -f "${entropy_dir}/saved-entropy.${file_num}" ]; then
new_file=saved-entropy.$(( $file_num + 1 ))
if [ -e "${entropy_dir}/${new_file}" ]; then
unlink ${entropy_dir}/${new_file}
fi
mv "${entropy_dir}/saved-entropy.${file_num}" \
"${entropy_dir}/${new_file}"
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