view debian/dropbear.init @ 1715:3974f087d9c0

Disallow leading lines before the ident for server (#102) Per RFC4253 4.2 clients must be able to process other lines of data before the version string, server behavior is not defined neither with MUST/SHOULD nor with MAY. If server process up to 50 lines too - it may cause too long hanging session with invalid/evil client that consume host resources and potentially may lead to DDoS on poor embedded boxes. Let's require first line from client to be version string and fail early if it's not - matches both RFC and real OpenSSH behavior.
author Vladislav Grishenko <themiron@users.noreply.github.com>
date Mon, 15 Jun 2020 18:22:18 +0500
parents 4ca2872c7d9e
children
line wrap: on
line source

#!/bin/sh
### BEGIN INIT INFO
# Provides:          dropbear
# Required-Start:    $remote_fs $syslog
# Required-Stop:     $remote_fs $syslog
# Default-Start:     2 3 4 5
# Default-Stop:      0 1 6
# Short-Description: Dropbear SSH server
### END INIT INFO
#
# Do not configure this file. Edit /etc/default/dropbear instead!
#

PATH=/usr/local/sbin:/usr/local/bin:/sbin:/bin:/usr/sbin:/usr/bin
DAEMON=/usr/sbin/dropbear
NAME=dropbear
DESC="Dropbear SSH server"

DROPBEAR_PORT=22
DROPBEAR_EXTRA_ARGS=
NO_START=0

set -e

cancel() { echo "$1" >&2; exit 0; };
test ! -r /etc/default/dropbear || . /etc/default/dropbear
test -x "$DAEMON" || cancel "$DAEMON does not exist or is not executable."
test ! -x /usr/sbin/update-service || ! update-service --check dropbear ||
  cancel 'The dropbear service is controlled through runit, use the sv(8) program'

test -z "$DROPBEAR_BANNER" || \
  DROPBEAR_EXTRA_ARGS="$DROPBEAR_EXTRA_ARGS -b $DROPBEAR_BANNER"
test -n "$DROPBEAR_RSAKEY" || \
  DROPBEAR_RSAKEY="/etc/dropbear/dropbear_rsa_host_key"
test -n "$DROPBEAR_DSSKEY" || \
  DROPBEAR_DSSKEY="/etc/dropbear/dropbear_dss_host_key"
test -n "$DROPBEAR_RECEIVE_WINDOW" || \
  DROPBEAR_RECEIVE_WINDOW="65536"

case "$1" in
  start)
	test "$NO_START" = "0" || cancel 'NO_START is not set to zero.'
	echo -n "Starting $DESC: "
	start-stop-daemon --start --quiet --pidfile /var/run/"$NAME".pid \
	  --exec "$DAEMON" -- -d "$DROPBEAR_DSSKEY" -r "$DROPBEAR_RSAKEY" \
	    -p "$DROPBEAR_PORT" -W "$DROPBEAR_RECEIVE_WINDOW" $DROPBEAR_EXTRA_ARGS
	echo "$NAME."
	;;
  stop)
	echo -n "Stopping $DESC: "
	start-stop-daemon --stop --quiet --oknodo --pidfile /var/run/"$NAME".pid
	echo "$NAME."
	;;
  restart|force-reload)
	test "$NO_START" = "0" || cancel 'NO_START is not set to zero.'
	echo -n "Restarting $DESC: "
	start-stop-daemon --stop --quiet --oknodo --pidfile /var/run/"$NAME".pid
	sleep 1
	start-stop-daemon --start --quiet --pidfile /var/run/"$NAME".pid \
	  --exec "$DAEMON" -- -d "$DROPBEAR_DSSKEY" -r "$DROPBEAR_RSAKEY" \
	    -p "$DROPBEAR_PORT" -W "$DROPBEAR_RECEIVE_WINDOW" $DROPBEAR_EXTRA_ARGS
	echo "$NAME."
	;;
  *)
	N=/etc/init.d/$NAME
	echo "Usage: $N {start|stop|restart|force-reload}" >&2
	exit 1
	;;
esac

exit 0