OpenVPN server

• 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.

Set up DDNS client if required. Install the packages and 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="$(uci -q get "$(uci -q show ddns \
| sed -n -e "/\.enabled='1'$/s//.lookup_host/p" \
| sed -n -e "1p")")"
if [ -n "${NET_FQDN}" ]
then OVPN_SERV="${NET_FQDN}"
fi

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

# Configuration parameters
export EASYRSA_PKI="${OVPN_PKI}"
export EASYRSA_REQ_CN="ovpnca"
export EASYRSA_BATCH="1"
 
# Remove and re-initialize the PKI directory
easyrsa init-pki
 
# Generate DH parameters
easyrsa gen-dh
 
# Create a new CA
easyrsa build-ca nopass
 
# Generate a key pair and sign locally for a server
easyrsa build-server-full server nopass
 
# Generate a key pair and sign locally for a client
easyrsa build-client-full client nopass
 
# Generate TLS PSK
openvpn --genkey --secret ${OVPN_PKI}/tc.pem

Consider VPN network as private and 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.

# Configuration parameters
OVPN_DH="$(cat ${OVPN_PKI}/dh.pem)"
OVPN_TC="$(sed -e "/^#/d;/^\w/N;s/\n//" ${OVPN_PKI}/tc.pem)"
OVPN_CA="$(openssl x509 -in ${OVPN_PKI}/ca.crt)"
NL=$'\n'
 
# Configure VPN service and generate client profiles
umask go=
ls ${OVPN_PKI}/issued \
| sed -e "s/\.\w*$//" \
| while read -r OVPN_ID
do
OVPN_KEY="$(cat ${OVPN_PKI}/private/${OVPN_ID}.key)"
OVPN_CERT="$(openssl x509 -in ${OVPN_PKI}/issued/${OVPN_ID}.crt)"
OVPN_EKU="$(openssl x509 -in ${OVPN_PKI}/issued/${OVPN_ID}.crt -purpose)"
OVPN_CONF_SERVER="\
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 ${OVPN_DOMAIN}\"
push \"redirect-gateway def1\"
push \"persist-tun\"
push \"persist-key\"
<dh>${NL}${OVPN_DH}${NL}</dh>"
OVPN_CONF_CLIENT="\
dev tun
nobind
client
remote ${OVPN_SERV} ${OVPN_PORT} ${OVPN_PROTO}
auth-nocache
remote-cert-tls server"
OVPN_CONF_COMMON="\
<tls-crypt>${NL}${OVPN_TC}${NL}</tls-crypt>
<key>${NL}${OVPN_KEY}${NL}</key>
<cert>${NL}${OVPN_CERT}${NL}</cert>
<ca>${NL}${OVPN_CA}${NL}</ca>"
case ${OVPN_EKU} in
(*"SSL server : Yes"*) cat << EOF > ${OVPN_DIR}/${OVPN_ID}.conf ;;
${OVPN_CONF_SERVER}
${OVPN_CONF_COMMON}
EOF
(*"SSL client : Yes"*) cat << EOF > ${OVPN_DIR}/${OVPN_ID}.ovpn ;;
${OVPN_CONF_CLIENT}
${OVPN_CONF_COMMON}
EOF
esac
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.

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; ip -6 rule show; iptables-save; ip6tables-save
 
# Persistent configuration
uci show network; uci show firewall; uci show openvpn
head -n -0 /etc/openvpn/*.conf