Install and configure Tor as proxy for all OpenVPN server traffic

tor-openvpn.sh

# what we want:
# client -> OpenVPN -> Tor -> Internet

# Install & configure OpenVPN
# https://www.digitalocean.com/community/tutorials/how-to-set-up-an-openvpn-server-on-ubuntu-16-04

# assumed OpenVPN configuration
# 10.8.0.1/24-Subnet
# tun0-Interface

# Install & configure Tor
sudo apt install tor

sudo vi /etc/tor/torrc

  VirtualAddrNetwork 10.192.0.0/10
  AutomapHostsOnResolve 1
  DNSPort 10.8.0.1:53530
  TransPort 10.8.0.1:9040

sudo service tor restart

# Check ports
sudo netstat -tulpen | grep tor

  tcp 0 0 10.8.0.1:9040 0.0.0.0:* LISTEN 0 3964140 1525/tor 
  tcp 0 0 127.0.0.1:9051 0.0.0.0:* LISTEN 0 3964141 1525/tor 
  udp 0 0 10.8.0.1:53530 0.0.0.0:* 0 3964139 1525/tor

# Config IPtables to route all traffic trough Tor proxy
export IPTABLES=/sbin/iptables
export OVPN=tun0
# transparent Tor proxy
$IPTABLES -A INPUT -i $OVPN -s 10.8.0.0/24 -m state --state NEW -j ACCEPT
$IPTABLES -t nat -A PREROUTING -i $OVPN -p udp --dport 53 -s 10.8.0.0/24 -j DNAT --to-destination 10.8.0.1:53530
$IPTABLES -t nat -A PREROUTING -i $OVPN -p tcp -s 10.8.0.0/24 -j DNAT --to-destination 10.8.0.1:9040
$IPTABLES -t nat -A PREROUTING -i $OVPN -p udp -s 10.8.0.0/24 -j DNAT --to-destination 10.8.0.1:9040