From 6a39de8a71bd177ebc0d03e048e99ccb5828c020 Mon Sep 17 00:00:00 2001
From: markm <markm@FreeBSD.org>
Date: Mon, 17 Jul 2000 12:28:58 +0000
Subject: [PATCH] Add entropy caching. With this, some entropy is cached at
 shutdown time, and this is used to reseed the random number generator at boot
 time.

NOTE - this has no hope of working if you halt(); you need to
execute rc.shutdown to get the entropy stash.
---
 etc/defaults/rc.conf |  2 ++
 etc/rc               | 14 ++++++++++++++
 etc/rc.shutdown      | 15 +++++++++++++++
 3 files changed, 31 insertions(+)

diff --git a/etc/defaults/rc.conf b/etc/defaults/rc.conf
index 36a89ffe34b7..fcdf302f5b99 100644
--- a/etc/defaults/rc.conf
+++ b/etc/defaults/rc.conf
@@ -291,6 +291,8 @@ kern_securelevel_enable="NO"	# kernel security level (see init(8)),
 kern_securelevel="-1"	# range: -1..3 ; `-1' is the most insecure
 update_motd="YES"	# update version info in /etc/motd (or NO)
 start_vinum=""		# set to YES to start vinum
+entropy_file="/var/db/entropy"
+			# Set to NO to disable caching entropy through reboots
 
 ##############################################################
 ### Define source_rc_confs, the mechanism used by /etc/rc.* ##
diff --git a/etc/rc b/etc/rc
index 6d03e4936f79..47d15b44075a 100644
--- a/etc/rc
+++ b/etc/rc
@@ -132,6 +132,20 @@ if [ -n "${diskless_mount}" -a -r "${diskless_mount}" ]; then
 		sh ${diskless_mount}
 fi
 
+# Recover some entropy so the rebooting /dev/random can reseed
+#
+case ${entropy_file} in
+[Nn][Oo] | '')
+	;;
+*)
+	if [ -f ${entropy_file} -a -r ${entropy_file} ] ; then
+		echo -n "Reading entropy file"
+		cat ${entropy_file} > /dev/random
+		rm -f ${entropy_file}
+	fi
+	;;
+esac
+
 adjkerntz -i
 
 clean_var() {
diff --git a/etc/rc.shutdown b/etc/rc.shutdown
index 0d93bcf60460..7014c70e75f4 100644
--- a/etc/rc.shutdown
+++ b/etc/rc.shutdown
@@ -26,6 +26,21 @@ elif [ -r /etc/rc.conf ]; then
 	. /etc/rc.conf
 fi
 
+# Write some entropy so the rebooting /dev/random can reseed
+#
+case ${entropy_file} in
+[Nn][Oo] | '')
+	;;
+*)
+	if [ -f ${entropy_file} -a -r ${entropy_file} ] ; then
+		echo -n "Writing entropy file"
+		touch ${entropy_file} && \
+			chmod 600 ${entropy_file} && \
+			dd if=/dev/random of=${entropy_file} bs=4096 count=1
+	fi
+	;;
+esac
+
 # Check if /var/db/mounttab is clean.
 case $1 in
 reboot)