[Howto] Install and configure basic OpenVPN server for Oleg firmware

[ecaddict]

Introduction/Installing
OpenVPN is one of the most useful tools that can be installed on the router (sad that it's not part of the firmware itself, also not part of the excellent raas tutorial that I've re-used).
OpenVPN is a complex topic and unfortunately I'm not in a position to introduce you to all aspects. Basically the server running on the router allows you to access the router (and other machines on the router's LAN) from a remote machine over the internet like you would do it locally (you have to have OpenVPN client installed and properly configured on the remote machine though). Thus in short you can access the router e.g. from your relatives/friends, from public WiFi hotspots or from your workplace (unless restricted).

While installing OpenVPN is quite straightforward, it's not just ipkg install but you have to generate keys and set up the firewall properly etc.

This tutorial helps you in that. In fact it's sufficient to run only a script that does everything for you (questions will be asked though):

#!/bin/sh
#written by ecaddict, distributed (conveyed) under GPL version 3 or any later version

PORT=${1:-563}
VSNM=${2}
CONFIG="/opt/etc/openvpn/server${VSNM}.conf"
STARTS="/opt/etc/init.d/S20openvpn${VSNM}"
RSAVAR="/opt/share/easy-rsa/vars"
CKDIR="/mnt/protected"
#user editable part end

CONFD="${CONFIG%\/*}"
CONFF="${CONFIG##*/}"
INITD="${STARTS%\/*}"
INITF="${STARTS##*/}"
VARSD="${RSAVAR%\/*}"
VARSF="${RSAVAR##*/}"
VKDIR="${CONFD}/easy-rsa/keys${VSNM}"
TUNIF="tun0"

ipkg install openssl lzo net-tools easy-rsa psmisc openvpn

export EASY_RSA=${VARSD}
#creating certificates (if needed)
if [ ! -d "${VKDIR}" ]; then
 if [ -d "${VARSD}" ]; then
  cd ${VARSD} && [ ! -f ${VARSF}.old ] && cp ${VARSF} ${VARSF}.old
  echo -e "\033[1;32mSeveral questions will be asked that will be reflected in the keys\033[0m"
  echo -e "for private use your answer does not matter. \nSave previously generated keys from ${VARSD}/keys (if any)."
  echo -e "\033[1;32mType the number of clients you need keys for and press Enter\033[0m to continue."
  echo -e "Guess your number of clients well as it takes time both to generate and generate keys again."
  read CKEYN; CKEYN=${CKEYN:-1}; [ "${CKEYN}" -gt 9 ] && CKEYN=9
  ./clean-all
  source ${RSAVAR}
  echo -e "\033[1;32mGenerating CA key\033[0m"
  ./build-ca
  echo -e "\033[1;32mGenerating Diffie-Hellman parameters\033[0m"
  ./build-dh
  echo -e "\033[1;32mGenerating Server key \033[0m" && ./build-key-server server
  I=0; while [ ${I} -lt "${CKEYN}" ]; do
    let "I+=1"
      echo -e "\033[1;32mGenerating keys for client ${I}\033[0m" && ./pkitool --interact --inter client0${I}
  done
  mkdir -p ${VKDIR}
  mv ./keys/server* "${VKDIR}"
  mv ./keys/ca* "${VKDIR}"
  mv ./keys/dh1024.pem "${VKDIR}"
  mv ./keys/client* "${VKDIR}" #temporally
  else
   echo -e "\033[1;31mDirectory ${VARSD} does not exist\033[0m"
   exit 1
  fi
else
 echo -e "\033[1;33mThe directory ${VKDIR} exists, no keys are generated.\033[0m"
fi

cd ${CONFD} && [ ! -f ${CONFF}.old ] && mv ${CONFF} ${CONFF}.old
cat > ${CONFF} << __EOF__
port ${PORT}
proto tcp
dev tun
ca ${VKDIR}/ca.crt
cert ${VKDIR}/server.crt
key ${VKDIR}/server.key
dh ${VKDIR}/dh1024.pem

server 10.8.0.0 255.255.255.0
ifconfig-pool-persist ipp.txt
push "route 192.168.1.0 255.255.255.0"
duplicate-cn
keepalive 10 120
comp-lzo
persist-key
persist-tun
status openvpn-status.log
verb 3
__EOF__

tar -cvzf ${CKDIR}/vpnkeys${VSNM}.tar.gz ${VKDIR}/ca.crt ${VKDIR}/client0?.crt ${VKDIR}/client0?.key

cd ${INITD} && [ ! -f old.${INITF} ] && mv ${INITF} old.${INITF}
cat > ${INITF} << __EOF__
#!/bin/sh
#
# Startup script for openvpn as standalone server
#
PREFIX="/opt"
PORT=${PORT}
NAME=openvpn
PFILE="/opt/var/run/vpnserver${VSNM}.pid"
OPTS="--daemon --cd /opt/etc/openvpn --log-append /opt/var/log/openvpn.log --config ${CONFF} --writepid \${PFILE}"

# Make sure IP forwarding is enabled
echo 1 > /proc/sys/net/ipv4/ip_forward

# Make device if not present (not devfs)
if ( [ ! -c /dev/net/tun ] ) then
  # Make /dev/net directory if needed
  if ( [ ! -d /dev/net ] ) then
        mkdir -m 755 /dev/net
  fi
  mknod /dev/net/tun c 10 200
fi

# Make sure the tunnel driver is loaded
if ( !(lsmod | grep -q "^tun") ); then
        insmod tun
fi

if [ -z "\$1" ] ; then
    case \`echo "\$0" | sed 's:^.*/\(.*\):\1:g'\` in
        S??*) rc="start" ;;
        K??*) rc="stop" ;;
        *) rc="usage" ;;
    esac
else
    rc="\$1"
fi

case "\$rc" in
    start)
        echo "Starting: \$NAME"
        \${PREFIX}/sbin/\${NAME} \$OPTS
        iptables -I INPUT -i \`nvram get wan_ifname\` -p tcp --dport \$PORT -j ACCEPT
        ;;
    stop)
        if [ -f \${PFILE} ] ; then
          kill \`cat \${PFILE}\` >/dev/null 2>&1
          rm -f \${PFILE}
          iptables -D INPUT -i \`nvram get wan_ifname\` -p tcp --dport \$PORT -j ACCEPT
        else
          killall "\$NAME"
        fi
        ;;
    restart)
        "\$0" stop
        sleep 1
        "\$0" start
        ;;
    *)
        echo "Usage: \$0 (start|stop|restart|usage)"
        ;;
esac

__EOF__

[ -n "$2" ] && TUNIF="tun+"
if [ -z "`sed -n 's/-i '${TUNIF}' -j ACCEPT/&/p' /usr/local/sbin/post-firewall`" ]; then
cat >> /usr/local/sbin/post-firewall << __EOF__
iptables -I INPUT -i ${TUNIF} -j ACCEPT
iptables -I FORWARD -i ${TUNIF} -j ACCEPT
iptables -I FORWARD -o ${TUNIF} -j ACCEPT
iptables -I OUTPUT -o ${TUNIF} -j ACCEPT
__EOF__
iptables -I INPUT -i ${TUNIF} -j ACCEPT
iptables -I FORWARD -i ${TUNIF} -j ACCEPT
iptables -I FORWARD -o ${TUNIF} -j ACCEPT
iptables -I OUTPUT -o ${TUNIF} -j ACCEPT
 flashfs save && flashfs commit && flashfs enable
fi

chmod u+x ${INITF}
${STARTS} start

The script will ask how many client keys should be generated (max 9) and typical questions for the keys like your location etc. Answer as you wish but you have to answer with y (yes) to the sign the certificate and commit questions.

There are the following typical options for the server port for OpenVPN:
1194 or 443 or 563
While 1194 is the well known port for OpenVPN, some restrictive firewalls don't allow this port so you may need to use 563 that's typically allowed (and also the script uses) or 443 (https port). If you plan to use port 443, it means that you cannot use it with the lighttpd which is not nice.

If you wish to use some other port start the script with the port ./install.sh <port>.
If you plan to start multiple server instances not only have to give different port but also different number or names to them like ./install.sh <port> <number/name>.

You can download the OpenVPN client from http://openvpn.net/index.php/open-source/downloads.html
Learn more about OpenVPN:
http://linux.die.net/man/8/openvpn
http://openvpn.net/index.php/open-so...ion/howto.html

The generated client keys are copied to /mnt/protected/
On Windows you need the following keys (taken from the router):
C:\Program Files\OpenVPN\config\ca.crt
C:\Program Files\OpenVPN\config\client.crt
C:\Program Files\OpenVPN\config\client.key

If you use port 563/443 then you probably have to set the proxy as well in the client to proxy IP and typically 8080 port.
(Note: if your proxy uses NTLM authentication you have to run as admin openvpn.exe as the GUI has some issue and --config for the .ovpn file containing
http-proxy yourproxyIP 8080 stdin ntlm; alternatively use cntlm http://cntlm.sourceforge.net/)

Here are some snapshots from the example run I've made:




You can download and run the script from here: install.tar.gz

If you're fine with the default parameters (single server, port: 563), you can paste the following line to your terminal (single line install).

cd /tmp && wget -O install.tar.gz "http://wl500g.info/attachment.php?attachmentid=8371&d=1318414980" && tar xvzf install.tar.gz && ./install.sh

By default the starter script is
/opt/etc/init.d/S20openvpn

The config file is:
/opt/etc/openvpn/server.conf

The keys are located in:
/opt/etc/openvpn/easy-rsa/keys/