Index: head/libexec/save-entropy/save-entropy.sh
===================================================================
--- head/libexec/save-entropy/save-entropy.sh	(revision 355246)
+++ head/libexec/save-entropy/save-entropy.sh	(revision 355247)
@@ -1,96 +1,133 @@
 #!/bin/sh
 #
 # SPDX-License-Identifier: BSD-2-Clause-FreeBSD
 #
 # Copyright (c) 2001-2006,2012 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
 
 [ $(/sbin/sysctl -n security.jail.jailed) = 0 ] || exit 0
 
 case ${entropy_dir} in
 [Nn][Oo])
 	exit 0
 	;;
 *)
 	entropy_dir=${entropy_dir:-/var/db/entropy}
 	;;
 esac
 
 entropy_save_sz=${entropy_save_sz:-4096}
 entropy_save_num=${entropy_save_num:-8}
 
 if [ ! -d "${entropy_dir}" ]; then
 	install -d -o operator -g operator -m 0700 "${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; }
 fi
 
 cd "${entropy_dir}" || {
 	logger -is -t "$0" Cannot cd to the entropy directory: "${entropy_dir}". \
 	    Entropy file rotation is aborted.; exit 1; }
 
 for f in saved-entropy.*; do
 	case "${f}" in saved-entropy.\*) continue ;; esac	# No files match
-	[ ${f#saved-entropy\.} -ge ${entropy_save_num} ] && unlink ${f}
+	[ ${f#saved-entropy\.} -gt ${entropy_save_num} ] && unlink ${f}
 done
 
-umask 377
+umask 177
 
-n=$(( ${entropy_save_num} - 1 ))
-while [ ${n} -ge 1 ]; do
-	if [ -f "saved-entropy.${n}" ]; then
-		mv "saved-entropy.${n}" "saved-entropy.$(( ${n} + 1 ))"
-	elif [ -e "saved-entropy.${n}" -o -L "saved-entropy.${n}" ]; then
+# Scan slots [1..$entropy_save_num), picking an empty slot or the oldest
+# existing file if no empty slot was available.
+#
+# 1. Find out the first regular file or empty slot (and its serial number)
+#
+n=1
+while [ ${n} -le ${entropy_save_num} ]; do
+	save_file="saved-entropy.${n}"
+	if [ ! -e "${save_file}" -o -f "${save_file}" ]; then
+		break
+	else
 		logger -is -t "$0" \
-	"${entropy_dir}/saved-entropy.${n}" is not a regular file, and so \
-	    it will not be rotated. Entropy file rotation is aborted.
-		exit 1
+		    "${save_file}" is not a regular file, skipped.
 	fi
-	n=$(( ${n} - 1 ))
+	n=$(( ${n} + 1 ))
 done
+#
+# 2. Start from (serial number + 1), and check if the slot is empty
+#    or is an older regular file, update save_file pointer in either
+#    case, and break early if we found an empty slot.
+#
+if [ -f ${save_file} ]; then
+	n=$(( ${n} + 1 ))
+	while [ ${n} -le ${entropy_save_num} ]; do
+		next_file=saved-entropy.${n}
+		if [ -f "${next_file}" ]; then
+			[ "${next_file}" -ot "${save_file}" ] && \
+			    save_file="${next_file}"
+		elif [ ! -e "${next_file}" ]; then
+			save_file="${next_file}"
+			break
+		else
+			logger -is -t "$0" \
+			    "${next_file}" is not a regular file, skipped.
+		fi
+		n=$(( ${n} + 1 ))
+	done
+fi
+#
+# 3. Check if the pointer we have in hand is really a regular file or
+#    an empty slot, and bail out as that means there is no available slot.
+#
+if [ -e "${save_file}" -a ! -f "${save_file}" ]; then
+	logger -is -t "$0" \
+		No available slot in "${entropy_dir}", save entropy is aborted.
+	exit 1
+fi
 
-dd if=/dev/random of=saved-entropy.1 bs=${entropy_save_sz} count=1 2>/dev/null
-chflags nodump saved-entropy.1 2>/dev/null || :
-fsync saved-entropy.1 "."
+# Save entropy to the selected slot.
+chmod 600 "${save_file}" 2>/dev/null || :
+dd if=/dev/random of="${save_file}" bs=${entropy_save_sz} count=1 2>/dev/null
+chflags nodump "${save_file}" 2>/dev/null || :
+fsync "${save_file}" "."
 
 exit 0