1#!/bin/sh
2#
3# SPDX-License-Identifier: BSD-2-Clause
4#
5# Copyright (c) 2001-2006,2012 Douglas Barton, dougb@FreeBSD.org
6# All rights reserved.
7#
8# Redistribution and use in source and binary forms, with or without
9# modification, are permitted provided that the following conditions
10# are met:
11# 1. Redistributions of source code must retain the above copyright
12#    notice, this list of conditions and the following disclaimer.
13# 2. Redistributions in binary form must reproduce the above copyright
14#    notice, this list of conditions and the following disclaimer in the
15#    documentation and/or other materials provided with the distribution.
16#
17# THIS SOFTWARE IS PROVIDED BY THE AUTHOR AND CONTRIBUTORS ``AS IS'' AND
18# ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
19# IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
20# ARE DISCLAIMED.  IN NO EVENT SHALL THE AUTHOR OR CONTRIBUTORS BE LIABLE
21# FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
22# DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
23# OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
24# HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
25# LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
26# OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
27# SUCH DAMAGE.
28#
29# $FreeBSD$
30
31# This script is called by cron to store bits of randomness which are
32# then used to seed /dev/random on boot.
33
34# Originally developed by Doug Barton, dougb@FreeBSD.org
35
36PATH=/bin:/usr/bin
37
38# If there is a global system configuration file, suck it in.
39#
40if [ -r /etc/defaults/rc.conf ]; then
41	. /etc/defaults/rc.conf
42	source_rc_confs 2>/dev/null
43elif [ -r /etc/rc.conf ]; then
44	. /etc/rc.conf 2>/dev/null
45fi
46
47[ $(/sbin/sysctl -n security.jail.jailed) = 0 ] || exit 0
48
49case ${entropy_dir} in
50[Nn][Oo])
51	exit 0
52	;;
53*)
54	entropy_dir=${entropy_dir:-/var/db/entropy}
55	;;
56esac
57
58entropy_save_sz=${entropy_save_sz:-4096}
59entropy_save_num=${entropy_save_num:-8}
60
61if [ ! -d "${entropy_dir}" ]; then
62	install -d -o operator -g operator -m 0700 "${entropy_dir}" || {
63		logger -is -t "$0" The entropy directory "${entropy_dir}" does \
64		    not exist, and cannot be created. Therefore no entropy can \
65		    be saved.; exit 1; }
66fi
67
68cd "${entropy_dir}" || {
69	logger -is -t "$0" Cannot cd to the entropy directory: "${entropy_dir}". \
70	    Entropy file rotation is aborted.; exit 1; }
71
72for f in saved-entropy.*; do
73	case "${f}" in saved-entropy.\*) continue ;; esac	# No files match
74	[ ${f#saved-entropy\.} -gt ${entropy_save_num} ] && unlink ${f}
75done
76
77umask 177
78
79# Scan slots [1..$entropy_save_num), picking an empty slot or the oldest
80# existing file if no empty slot was available.
81#
82# 1. Find out the first regular file or empty slot (and its serial number)
83#
84n=1
85while [ ${n} -le ${entropy_save_num} ]; do
86	save_file="saved-entropy.${n}"
87	if [ ! -e "${save_file}" -o -f "${save_file}" ]; then
88		break
89	else
90		logger -is -t "$0" \
91		    "${save_file}" is not a regular file, skipped.
92	fi
93	n=$(( ${n} + 1 ))
94done
95#
96# 2. Start from (serial number + 1), and check if the slot is empty
97#    or is an older regular file, update save_file pointer in either
98#    case, and break early if we found an empty slot.
99#
100if [ -f ${save_file} ]; then
101	n=$(( ${n} + 1 ))
102	while [ ${n} -le ${entropy_save_num} ]; do
103		next_file=saved-entropy.${n}
104		if [ -f "${next_file}" ]; then
105			[ "${next_file}" -ot "${save_file}" ] && \
106			    save_file="${next_file}"
107		elif [ ! -e "${next_file}" ]; then
108			save_file="${next_file}"
109			break
110		else
111			logger -is -t "$0" \
112			    "${next_file}" is not a regular file, skipped.
113		fi
114		n=$(( ${n} + 1 ))
115	done
116fi
117#
118# 3. Check if the pointer we have in hand is really a regular file or
119#    an empty slot, and bail out as that means there is no available slot.
120#
121if [ -e "${save_file}" -a ! -f "${save_file}" ]; then
122	logger -is -t "$0" \
123		No available slot in "${entropy_dir}", save entropy is aborted.
124	exit 1
125fi
126
127# Save entropy to the selected slot.
128chmod 600 "${save_file}" 2>/dev/null || :
129dd if=/dev/random of="${save_file}" bs=${entropy_save_sz} count=1 2>/dev/null
130chflags nodump "${save_file}" 2>/dev/null || :
131fsync "${save_file}" "."
132
133exit 0
134