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Introduction

The primary purpose of this playbook is to secure the private network of DigitalOcean Droplets with tinc VPN. You can use it with any Ubuntu servers that can reach each other over a network.

This sets up a tinc VPN between several servers. It also adds /etc/hosts entries for the inventory hostnames to resolve to the VPN IP addresses.

Prerequisites

This playbook been tested on Ubuntu 14.04 and CentOS 7 servers.

Your local machine (where Ansible is installed) must be able to log in to the remote servers as "root", preferably with passwordless public SSH key, which is specified as the remote_user in /ansible.cfg. Due to a bug with the Ansible Synchronize module, it is not possible to use a different remote_user at this time.

By default, this playbook will bind tinc to the IP address on the eth1 interface (private network interface on DigitalOcean Droplets). See the "Review Group Variables" section to change this.

Preparation

Create Inventory

Create a /hosts file with the nodes that you want to include in the VPN:

[vpn]
prod01 vpn_ip=10.0.0.1 ansible_host=162.243.125.98
prod02 vpn_ip=10.0.0.2 ansible_host=162.243.243.235
prod03 vpn_ip=10.0.0.3 ansible_host=162.243.249.86
prod04 vpn_ip=10.0.0.4 ansible_host=162.243.252.151

[removevpn]

The first line, [vpn], specifies that the host entries directly below it are part of the "vpn" group. Members of this group will have the Tinc mesh VPN configured on them.

  • The first column is where you set the inventory name of a host, "node01" in the first line of the example, how Ansible will refer to the host. This value is used to configure Tinc connections, and to generate /etc/hosts entries. Do not use hyphens here, as Tinc does not support them in host names
  • vpn_ip is the IP address that the node will use for the VPN
  • ansible_host must be set to a value that your ansible machine can reach the node at

Note: The inventory hostname, which we are using as each node's name in Tinc, can't contain characters that Tinc doesn't allow for node names. For example, hyphens (-) are not allowed.

Review Group Variables

The /group_vars/all file contains a few values that you may want to modify.

  • physical_ip specifies which IP address you want tinc to bind to, based on network interface name. It is set to eth1 (ansible_eth1) by default. On DigitalOcean, eth1 is the private network interface so Private Networking must be enabled unless you would rather use the public network interface (eth0)
  • netname specifies the tinc netname. It's set to nyc3 by default.
  • vpn_netmask specifies the netmask that the will be applied to the VPN interface. By default, it's set to 255.255.255.0, which means that each vpn_ip is a Class C address which can only communicate with other hosts within the same subnet. For example, a 10.0.0.x will not be able to communicate with a 10.0.1.x host unless the subnet is enlarged by changing vpn_netmask to something like 255.255.0.0.

The other variables probably don't need to be modified.

  • vpn_interface is the virtual network interface that tinc will use. It is tun0 by default.

Set Up Tinc

Run the playbook:

ansible-playbook site.yml

After the playbook completes, all of the hosts in the inventory file should be able to communicate with each other over the VPN network.

Quick Test

Log in to your first host and ping the second host:

ping 10.0.0.2

Or, assuming one of your hosts is named prod02, run this:

ping prod02

Feel free to test the other nodes.

How to Add or Remove Servers

Add New Servers

All servers listed in the the [vpn] group in the /hosts file will be part of the VPN. To add new VPN members, simply add the new servers to the [vpn] group then re-run the Playbook:

ansible-playbook site.yml

Remove Servers

To remove VPN members, move /hosts entries of the servers you want to remove under the [removevpn] group towards the bottom of the file.

For example, if we wanted to remove node04, the /hosts file would look like this:

[label /hosts — remove node04 from VPN]
[vpn]
node01 vpn_ip=10.0.0.1 ansible_host=192.0.2.55
node02 vpn_ip=10.0.0.2 ansible_host=192.0.2.240
node03 vpn_ip=10.0.0.3 ansible_host=198.51.100.4

[removevpn]
node04 vpn_ip=10.0.0.4 ansible_host=198.51.100.36

Save the hosts file. Note that the vpn_ip is optional and unused for [removevpn] group members.

Then re-run the Playbook:

ansible-playbook site.yml

This will stop Tinc and delete the Tinc configuration and host key files from the members of the [removevpn] group.

Note that removing hosts from the VPN will result in orphaned tinc hosts files and /etc/hosts entries on the remaining VPN members. This should not affect anything unless you later add new servers to the VPN but reuse the decommissioned names. Delete the appropriate /etc/hosts entries on each server, if this is a problem for you.

Running Multiple VPNs

This playbook does not support multiple VPNs but it could be easily extended.