Patch OpenVPN client config to support DNS in Ubuntu/Debian

patch.sh

#!/bin/bash

#
# A utility for patching the user's client connection profile to support DNS
# resolution in OpenVPN clients which do not otherwise support it.
#

if ! pidof systemd 2>&1 >/dev/null; then
    echo "This script currently supports only SystemD users"
    return 1 2>/dev/null
    exit 1
fi

if ! type wget 2>&1 >/dev/null && ! type curl 2>&1 >/dev/null ; then
    echo "This script requires either wget or curl"
    return 1 2>/dev/null
    exit 1
fi

if ! type sed 2>&1 >/dev/null ; then
    echo "This script requires sed"
    return 1 2>/dev/null
    exit 1
fi

if [ ! -f "$1" ]; then
    echo "First argument must be the path to an OpenVPN client configuration"
    return 1 2>/dev/null
    exit 1
fi

# Download the script for updating resolved
if [ ! -f "/etc/openvpn/scripts/update-systemd-resolved" ]; then
    if type wget 2>&1 >/dev/null ; then
        sudo wget https://raw.githubusercontent.com/jonathanio/update-systemd-resolved/master/update-systemd-resolved -P /etc/openvpn/scripts
    elif type curl 2>&1 >/dev/null ; then
        curl -O /etc/openvpn/scripts/update-systemd-resolved https://raw.githubusercontent.com/jonathanio/update-systemd-resolved/master/update-systemd-resolved
    fi
    sudo chmod +x /etc/openvpn/scripts/update-systemd-resolved
fi

# Update the OpenVPN client connection configuration
sed -i -e '/^#\?\(\s*script-security\s\).*/{s//\12/;:a;n;ba;q}' -e '$ascript-security 2' "$1"
sed -i -e '/^#\?\(\s*up\s\).*/{s//\1\/etc\/openvpn\/scripts\/update-systemd-resolved/;:a;n;ba;q}' -e '$aup /etc/openvpn/scripts/update-systemd-resolved' "$1"
sed -i -e '/^#\?\(\s*down\s\).*/{s//\1\/etc\/openvpn\/scripts\/update-systemd-resolved/;:a;n;ba;q}' -e '$adown /etc/openvpn/scripts/update-systemd-resolved' "$1"