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
30# This script is called by cron to store bits of randomness which are
31# then used to seed /dev/random on boot.
32
33# Originally developed by Doug Barton, dougb@FreeBSD.org
34
35PATH=/bin:/usr/bin
36
37# If there is a global system configuration file, suck it in.
38#
39if [ -r /etc/defaults/rc.conf ]; then
40	. /etc/defaults/rc.conf
41	source_rc_confs 2>/dev/null
42elif [ -r /etc/rc.conf ]; then
43	. /etc/rc.conf 2>/dev/null
44fi
45
46[ $(/sbin/sysctl -n security.jail.jailed) = 0 ] || exit 0
47
48case ${entropy_dir} in
49[Nn][Oo])
50	exit 0
51	;;
52*)
53	entropy_dir=${entropy_dir:-/var/db/entropy}
54	;;
55esac
56
57entropy_save_sz=${entropy_save_sz:-4096}
58entropy_save_num=${entropy_save_num:-8}
59
60if [ ! -d "${entropy_dir}" ]; then
61	install -d -o operator -g operator -m 0700 "${entropy_dir}" || {
62		logger -is -t "$0" The entropy directory "${entropy_dir}" does \
63		    not exist, and cannot be created. Therefore no entropy can \
64		    be saved.; exit 1; }
65fi
66
67cd "${entropy_dir}" || {
68	logger -is -t "$0" Cannot cd to the entropy directory: "${entropy_dir}". \
69	    Entropy file rotation is aborted.; exit 1; }
70
71for f in saved-entropy.*; do
72	case "${f}" in saved-entropy.\*) continue ;; esac	# No files match
73	[ ${f#saved-entropy\.} -gt ${entropy_save_num} ] && unlink ${f}
74done
75
76umask 177
77
78# Scan slots [1..$entropy_save_num), picking an empty slot or the oldest
79# existing file if no empty slot was available.
80#
81# 1. Find out the first regular file or empty slot (and its serial number)
82#
83n=1
84while [ ${n} -le ${entropy_save_num} ]; do
85	save_file="saved-entropy.${n}"
86	if [ ! -e "${save_file}" -o -f "${save_file}" ]; then
87		break
88	else
89		logger -is -t "$0" \
90		    "${save_file}" is not a regular file, skipped.
91	fi
92	n=$(( ${n} + 1 ))
93done
94#
95# 2. Start from (serial number + 1), and check if the slot is empty
96#    or is an older regular file, update save_file pointer in either
97#    case, and break early if we found an empty slot.
98#
99if [ -f ${save_file} ]; then
100	n=$(( ${n} + 1 ))
101	while [ ${n} -le ${entropy_save_num} ]; do
102		next_file=saved-entropy.${n}
103		if [ -f "${next_file}" ]; then
104			[ "${next_file}" -ot "${save_file}" ] && \
105			    save_file="${next_file}"
106		elif [ ! -e "${next_file}" ]; then
107			save_file="${next_file}"
108			break
109		else
110			logger -is -t "$0" \
111			    "${next_file}" is not a regular file, skipped.
112		fi
113		n=$(( ${n} + 1 ))
114	done
115fi
116#
117# 3. Check if the pointer we have in hand is really a regular file or
118#    an empty slot, and bail out as that means there is no available slot.
119#
120if [ -e "${save_file}" -a ! -f "${save_file}" ]; then
121	logger -is -t "$0" \
122		No available slot in "${entropy_dir}", save entropy is aborted.
123	exit 1
124fi
125
126# Save entropy to the selected slot.
127chmod 600 "${save_file}" 2>/dev/null || :
128dd if=/dev/random of="${save_file}" bs=${entropy_save_sz} count=1 2>/dev/null
129chflags nodump "${save_file}" 2>/dev/null || :
130fsync "${save_file}" "."
131
132exit 0
133