qubes-doc/configuration/vpn.md

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How To make a VPN Gateway in Qubes

Although setting up a VPN connection is not by itself Qubes specific, there are a number of Qubes-related details that can make using the connection more versatile and secure. This document is a Qubes-specific outline for choosing the type of VM to use, and shows how to prepare a ProxyVM for either NetworkManager or a set of fail-safe VPN scripts.

Please refer to guest OS and VPN service documentation when considering the specific steps and parameters for your connection(s); The relevant documentation for the Qubes default guest OS (Fedora) is Establishing a VPN Connection.

NetVM

The simplest case is to set up a VPN connection using the NetworkManager service inside your NetVM. Because the NetworkManager service is already started, you are ready to set up your VPN connection. However this has some disadvantages:

• You have to place (and probably save) your VPN credentials inside the NetVM, which is directly connected to the outside world
• All your AppVMs which are connected to the NetVM will be connected to the VPN (by default)

AppVM

While the NetworkManager service is not started here (for a good reason), you can configure any kind of VPN client in your AppVM as well. However this is only suggested if your VPN client has special requirements.

ProxyVM

One of the best things in Qubes is that you can use a special type of VM called a ProxyVM. The special thing is that your AppVMs see this as a NetVM (or uplink), and your NetVMs see it as a downstream AppVM. Because of this, you can place a ProxyVM between your AppVMs and your NetVM. This is how the default sys-firewall VM functions.

Using a ProxyVM to set up a VPN client gives you the ability to:

• Separate your VPN credentials from Your NetVM.
• Separate your VPN credentials from Your AppVM data.
• Easily control which of your AppVMs are connected to your VPN by simply setting it as a NetVM of the desired AppVM.

Set up a ProxyVM as a VPN gateway using NetworkManager

1. Create a new VM: Name it, click the ProxyVM radio button then choose a color and template.

   

2. Add the network-manager service to this new VM.

   

3. Set up your VPN as described in the NetworkManager documentation linked above.

4. Configure your AppVMs to use the new VM as a NetVM.

   

5. Optionally, you can install some custom icons for your VPN

Set up a ProxyVM as a VPN gateway using iptables and CLI scripts

This method is more involved than the one above, but has anti-leak features that also make the connection fail closed should it be interrupted. It has been tested with Fedora 23 and Debian 8 templates.

1. Create a new VM: Name it, click the ProxyVM radio button then choose a color and template.

   

   Note: Do not enable NetworkManager in the ProxyVM, as it can interfere with the scripts' DNS features. If you enabled NetworkManager or used other methods in a previous attempt, do not re-use the old ProxyVM... Create a new one according to this step.

   If your choice of template VM doesn't already have the VPN client software, you'll need to install the software in the template before proceeding. Disable any auto-starting service that comes with the software package: for example sudo systemctl disable openvpn.service.

   You may also wish to install nano or other simple text editor for entering the scripts below.

2. Set up and initial test of the VPN client.

   Make sure the VPN VM and its template VM are not running.

   Run a terminal (CLI) in the VPN VM -- this will start the VM. Then make a new 'vpn' folder with sudo mkdir /rw/config/vpn and copy your VPN config files here (the example config filename used here is openvpn-client.ovpn). Files accompanying the main config such as *.crt and *.pem should also go here, and should not be referenced in the main config by absolute paths such as '/etc/...'.

   Notes about VPN config options: The VPN scripts here are intended to work with commonly used tun interfaces, whereas tap mode is untested. Also, the config should route all traffic through your VPN's interface after a connection is created; For openvpn the directive for this is redirect-gateway def1. Lastly, the VPN client may not be able to prompt you for credentials when connecting to the server: Creating a file in the 'vpn' folder with your credentials and using a directive such as openvpn's auth-user-pass <filename> is recommended.

   Test your client configuration: Run the client from a CLI prompt in the 'vpn' folder, preferably as root. For example:

   sudo openvpn --cd /rw/config/vpn --config openvpn-client.ovpn
   

   Watch for status messages that indicate whether the connection is successful and test from another VPN VM terminal window with ping and traceroute. DNS may be tested at this point by replacing addresses in /etc/resolv.conf with ones appropriate for your VPN (although this file will not be used when setup is complete). Diagnose any connection problems using resources such as client documentation and help from your VPN service provider.

   Proceed to the next step when you're sure the basic VPN connection is working.

3. Create the DNS-handling script. Use sudo nano /rw/config/vpn/qubes-vpn-handler.sh to edit and add:

   #!/bin/bash
   set -e
   export PATH="$PATH:/usr/sbin:/sbin"
   
   case "$1" in
   
   up)
   # To override DHCP DNS, assign DNS addresses to 'vpn_dns' env variable before calling this script;
   # Format is 'X.X.X.X  Y.Y.Y.Y [...]'
   if [[ -z "$vpn_dns" ]] ; then
   	# Parses DHCP foreign_option_* vars to automatically set DNS address translation:
   	for optionname in ${!foreign_option_*} ; do
   		option="${!optionname}"
   		unset fops; fops=($option)
   		if [ ${fops[1]} == "DNS" ] ; then vpn_dns="$vpn_dns ${fops[2]}" ; fi
   	done
   fi
   
   iptables -t nat -F PR-QBS
   if [[ -n "$vpn_dns" ]] ; then
   	# Set DNS address translation in firewall:
   	for addr in $vpn_dns; do
   		iptables -t nat -A PR-QBS -i vif+ -p udp --dport 53 -j DNAT --to $addr
   		iptables -t nat -A PR-QBS -i vif+ -p tcp --dport 53 -j DNAT --to $addr
   	done
   	su - -c 'notify-send "$(hostname): LINK IS UP." --icon=network-idle' user
   else
   	su - -c 'notify-send "$(hostname): LINK UP, NO DNS!" --icon=dialog-error' user
   fi
   
   ;;
   down)
   su - -c 'notify-send "$(hostname): LINK IS DOWN !" --icon=dialog-error' user
   ;;
   esac
   

   Now save the script and make it executable:
   sudo chmod +x /rw/config/vpn/qubes-vpn-handler.sh

4. Configure client to use the DNS handling script. Using openvpn as an example, edit the config with sudo nano /rw/config/vpn/openvpn-client.ovpn and add these lines:

   script-security 2
   up 'qubes-vpn-handler.sh up'
   down 'qubes-vpn-handler.sh down'
   

   Restart the client and test the connection again ...this time from an AppVM!

5. Set up iptables anti-leak rules.

   Edit the firewall script with sudo nano /rw/config/qubes-firewall-user-script then clear out the existing lines and add:

   #!/bin/bash
   #    Block forwarding of connections through upstream network device
   #    (in case the vpn tunnel breaks):
   iptables -I FORWARD -o eth0 -j DROP
   iptables -I FORWARD -i eth0 -j DROP
   
   #    Block all outgoing traffic
   iptables -P OUTPUT DROP
   iptables -F OUTPUT
   iptables -I OUTPUT -o lo -j ACCEPT
   
   #    Add the `qvpn` group to system, if it doesn't already exist
   if ! grep -q "^qvpn:" /etc/group ; then
       groupadd -rf qvpn
       sync
   fi
   sleep 2s
   
   #    Allow traffic from the `qvpn` group to the uplink interface (eth0);
   #    Our VPN client will run with group `qvpn`.
   iptables -I OUTPUT -p all -o eth0 -m owner --gid-owner qvpn -j ACCEPT
   

   Now save the script and make it executable:
   sudo chmod +x /rw/config/qubes-firewall-user-script

6. Set up the VPN's autostart.

   Use sudo nano /rw/config/rc.local to clear out the existing lines and add:

   #!/bin/bash
   VPN_CLIENT='openvpn'
   VPN_OPTIONS='--cd /rw/config/vpn/ --config openvpn-client.ovpn --daemon'
   
   su - -c 'notify-send "$(hostname): Starting $VPN_CLIENT..." --icon=network-idle' user
   groupadd -rf qvpn ; sleep 2s
   sg qvpn -c "$VPN_CLIENT $VPN_OPTIONS"
   

   Change the VPN_CLIENT and VPN_OPTIONS variables to match your VPN software.

   Now save the script and make it executable:
   sudo chmod +x /rw/config/rc.local

7. Restart the new VM! The link should then be established automatically with a popup notification to that effect.

Usage

Configure your AppVMs to use the VPN VM as a NetVM...

Troubleshooting

• Always test your basic VPN connection before adding scripts.
• Test DNS: Ping a familiar domain name from an appVM. It should print the IP address for the domain.
• For scripting: Ping external IP addresses from inside the VPN VM using sudo sg qvpn -c 'ping ...', then from an appVM using just ping .... Once the firewall rules are in place, you will have to use sudo sg to run any IP network commands in the VPN VM.
• Use iptables -L -v and iptables -L -v -t nat to check firewall rules. The latter shows the critical PR-QBS chain that enables DNS forwarding.