save-entropy.sh revision 161683 
1#!/bin/sh
2#
3# Copyright (c) 2001-2006 Douglas Barton, DougB@FreeBSD.org
4# All rights reserved.
5#
6# Redistribution and use in source and binary forms, with or without
7# modification, are permitted provided that the following conditions
8# are met:
9# 1. Redistributions of source code must retain the above copyright
10#    notice, this list of conditions and the following disclaimer.
11# 2. Redistributions in binary form must reproduce the above copyright
12#    notice, this list of conditions and the following disclaimer in the
13#    documentation and/or other materials provided with the distribution.
14#
15# THIS SOFTWARE IS PROVIDED BY THE AUTHOR AND CONTRIBUTORS ``AS IS'' AND
16# ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
17# IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
18# ARE DISCLAIMED.  IN NO EVENT SHALL THE AUTHOR OR CONTRIBUTORS BE LIABLE
19# FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
20# DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
21# OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
22# HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
23# LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
24# OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
25# SUCH DAMAGE.
26#
27# $FreeBSD: head/libexec/save-entropy/save-entropy.sh 161683 2006-08-28 06:41:50Z dougb $
28
29# This script is called by cron to store bits of randomness which are
30# then used to seed /dev/random on boot.
31
32# Originally developed by Doug Barton, DougB@FreeBSD.org
33
34PATH=/bin:/usr/bin
35
36# If there is a global system configuration file, suck it in.
37#
38if [ -r /etc/defaults/rc.conf ]; then
39	. /etc/defaults/rc.conf
40	source_rc_confs 2>/dev/null
41elif [ -r /etc/rc.conf ]; then
42	. /etc/rc.conf 2>/dev/null
43fi
44
45case ${entropy_dir} in
46[Nn][Oo])
47	exit 0
48	;;
49*)
50	entropy_dir=${entropy_dir:-/var/db/entropy}
51	;;
52esac
53
54entropy_save_sz=${entropy_save_sz:-2048}
55entropy_save_num=${entropy_save_num:-8}
56
57if [ ! -d "${entropy_dir}" ]; then
58	umask 077
59	mkdir "${entropy_dir}" || {
60	    logger -is -t "$0" The entropy directory "${entropy_dir}" does not \
61exist, and cannot be created.  Therefore no entropy can be saved. ;
62	    exit 1;}
63	/usr/sbin/chown operator:operator "${entropy_dir}"
64	chmod 0700 "${entropy_dir}"
65fi
66
67umask 377
68
69esn_m1=$(( ${entropy_save_num} - 1 ))
70for file_num in `jot $esn_m1 $esn_m1 1`; do
71	if [ -e "${entropy_dir}/saved-entropy.${file_num}" ]; then
72		if [ -f "${entropy_dir}/saved-entropy.${file_num}" ]; then
73			new_file=saved-entropy.$(( $file_num + 1 ))
74			if [ -e "${entropy_dir}/${new_file}" ]; then
75				unlink ${entropy_dir}/${new_file}
76			fi
77			mv "${entropy_dir}/saved-entropy.${file_num}" \
78			    "${entropy_dir}/${new_file}"
79		else
80			logger -is -t "$0" \
81"${entropy_dir}/saved-entropy.${file_num} is not a regular file, and therefore \
82it will not be rotated. Entropy file harvesting is aborted."
83			exit 1
84		fi
85	fi
86done
87
88dd if=/dev/random of="${entropy_dir}/saved-entropy.1" \
89    bs="$entropy_save_sz" count=1 2> /dev/null
90
91exit 0
92
93