OpenVPN server

This article relies on the following:

This how-to describes the method for setting up OpenVPN server on OpenWrt.
Follow OpenVPN client for client setup and OpenVPN extras for additional tuning.

Encrypt your internet connection to enforce security and privacy.
- Prevent data leak and traffic spoofing on the client side.
Bypass regional restrictions using commercial providers.
- Escape client side content filters and internet censorship.
Access your LAN services remotely without port forwarding.

Install the required packages. Specify the VPN server configuration parameters.

# Install packages
opkg update
opkg install openvpn-openssl openvpn-easy-rsa
 
# Configuration parameters
OVPN_DIR="/etc/openvpn"
OVPN_PKI="/etc/easy-rsa/pki"
OVPN_PORT="1194"
OVPN_PROTO="udp"
OVPN_POOL="192.168.8.0 255.255.255.0"
OVPN_DNS="${OVPN_POOL%.* *}.1"
OVPN_DOMAIN="$(uci get dhcp.@dnsmasq[0].domain)"
 
# Fetch WAN IP address
. /lib/functions/network.sh
network_flush_cache
network_find_wan NET_IF
network_get_ipaddr NET_ADDR "${NET_IF}"
OVPN_SERV="${NET_ADDR}"
 
# Fetch FQDN from DDNS client
NET_FQDN="$(uci -q get ddns.@service[0].lookup_host)"
if [ -n "${NET_FQDN}" ]
then OVPN_SERV="${NET_FQDN}"
fi

Use EasyRSA to manage the PKI. Utilize private key password protection if necessary.

# Configuration parameters
export EASYRSA_PKI="${OVPN_PKI}"
export EASYRSA_REQ_CN="ovpnca"
export EASYRSA_BATCH="1"
 
# Remove and re-initialize PKI directory
easyrsa init-pki
 
# Generate DH parameters
easyrsa gen-dh
 
# Create a new CA
easyrsa build-ca nopass
 
# Generate server keys and certificate
easyrsa build-server-full server nopass
openvpn --genkey tls-crypt-v2-server ${EASYRSA_PKI}/private/server.pem
 
# Generate client keys and certificate
easyrsa build-client-full client nopass
openvpn --tls-crypt-v2 ${EASYRSA_PKI}/private/server.pem \
--genkey tls-crypt-v2-client ${EASYRSA_PKI}/private/client.pem

Consider VPN network as private. Assign VPN interface to LAN zone to minimize firewall setup. Allow access to VPN server from WAN zone.

# Configure firewall
uci rename firewall.@zone[0]="lan"
uci rename firewall.@zone[1]="wan"
uci del_list firewall.lan.device="tun+"
uci add_list firewall.lan.device="tun+"
uci -q delete firewall.ovpn
uci set firewall.ovpn="rule"
uci set firewall.ovpn.name="Allow-OpenVPN"
uci set firewall.ovpn.src="wan"
uci set firewall.ovpn.dest_port="${OVPN_PORT}"
uci set firewall.ovpn.proto="${OVPN_PROTO}"
uci set firewall.ovpn.target="ACCEPT"
uci commit firewall
/etc/init.d/firewall restart

Configure VPN service and generate client profiles.

# Configure VPN service and generate client profiles
umask go=
OVPN_DH="$(cat ${OVPN_PKI}/dh.pem)"
OVPN_CA="$(openssl x509 -in ${OVPN_PKI}/ca.crt)"
ls ${OVPN_PKI}/issued \
| sed -e "s/\.\w*$//" \
| while read -r OVPN_ID
do
OVPN_TC="$(cat ${OVPN_PKI}/private/${OVPN_ID}.pem)"
OVPN_KEY="$(cat ${OVPN_PKI}/private/${OVPN_ID}.key)"
OVPN_CERT="$(openssl x509 -in ${OVPN_PKI}/issued/${OVPN_ID}.crt)"
OVPN_EKU="$(echo "${OVPN_CERT}" | openssl x509 -noout -purpose)"
case ${OVPN_EKU} in
(*"SSL server : Yes"*)
OVPN_CONF="${OVPN_DIR}/${OVPN_ID}.conf"
cat << EOF > ${OVPN_CONF} ;;
user nobody
group nogroup
dev tun
port ${OVPN_PORT}
proto ${OVPN_PROTO}
server ${OVPN_POOL}
topology subnet
client-to-client
keepalive 10 60
persist-tun
persist-key
push "dhcp-option DNS ${OVPN_DNS}"
push "dhcp-option DOMAIN ${OVPN_DOMAIN}"
push "redirect-gateway def1"
push "persist-tun"
push "persist-key"
<dh>
${OVPN_DH}
</dh>
EOF
(*"SSL client : Yes"*)
OVPN_CONF="${OVPN_DIR}/${OVPN_ID}.ovpn"
cat << EOF > ${OVPN_CONF} ;;
user nobody
group nogroup
dev tun
nobind
client
remote ${OVPN_SERV} ${OVPN_PORT} ${OVPN_PROTO}
auth-nocache
remote-cert-tls server
EOF
esac
cat << EOF >> ${OVPN_CONF}
<tls-crypt-v2>
${OVPN_TC}
</tls-crypt-v2>
<key>
${OVPN_KEY}
</key>
<cert>
${OVPN_CERT}
</cert>
<ca>
${OVPN_CA}
</ca>
EOF
done
/etc/init.d/openvpn restart
ls ${OVPN_DIR}/*.ovpn

Perform OpenWrt backup. Extract client profiles from the archive and import them to your clients.

Establish the VPN connection. Use traceroute and traceroute6 to verify your client traffic is routed via the VPN gateway.

traceroute openwrt.org
traceroute6 openwrt.org

Check your client public IP addresses.

https://ipleak.net/

Make sure there is no DNS leak on the client side.

https://dnsleaktest.com/

Delegate a public IPv6 prefix to the VPN network to use IPv6 by default.

Collect and analyze the following information.

# Restart services
/etc/init.d/log restart; /etc/init.d/openvpn restart; sleep 10
 
# Log and status
logread -e openvpn; netstat -l -n -p | grep -e openvpn
 
# Runtime configuration
pgrep -f -a openvpn
ip address show; ip route show table all
ip rule show; iptables-save -c
ip -6 rule show; ip6tables-save -c
 
# Persistent configuration
uci show network; uci show firewall; uci show openvpn
head -v -n -0 /etc/openvpn/*.conf

OpenVPN server

Introduction

Goals

Command-line instructions

1. Preparation

2. Key management

3. Firewall

4. VPN service

Testing

Troubleshooting