Book Image

Mastering OpenVPN

By : Jan Just Keijser, Eric F Crist
Book Image

Mastering OpenVPN

By: Jan Just Keijser, Eric F Crist

Overview of this book

Security on the internet is increasingly vital to both businesses and individuals. Encrypting network traffic using Virtual Private Networks is one method to enhance security. The internet, corporate, and “free internet” networks grow more hostile every day. OpenVPN, the most widely used open source VPN package, allows you to create a secure network across these systems, keeping your private data secure. The main advantage of using OpenVPN is its portability, which allows it to be embedded into several systems. This book is an advanced guide that will help you build secure Virtual Private Networks using OpenVPN. You will begin your journey with an exploration of OpenVPN, while discussing its modes of operation, its clients, its secret keys, and their format types. You will explore PKI: its setting up and working, PAM authentication, and MTU troubleshooting. Next, client-server mode is discussed, the most commonly used deployment model, and you will learn about the two modes of operation using "tun" and "tap" devices. The book then progresses to more advanced concepts, such as deployment scenarios in tun devices which will include integration with back-end authentication, and securing your OpenVPN server using iptables, scripting, plugins, and using OpenVPN on mobile devices and networks. Finally, you will discover the strengths and weaknesses of the current OpenVPN implementation, understand the future directions of OpenVPN, and delve into the troubleshooting techniques for OpenVPN. By the end of the book, you will be able to build secure private networks across the internet and hostile networks with confidence.
Table of Contents (17 chapters)
Mastering OpenVPN
About the Authors
About the Reviewers

The basic setup

The basic setup for OpenVPN in tap mode is almost exactly the same as in the tun mode. In tap mode, we use the following line in the server configuration file:

dev tap

While in tun mode, we use the following lines:

dev tun
topology subnet

The option topology subnet is not required, but provides a network addressing scheme that is more sensible and will be the default in a future version of OpenVPN.

For the sake of completeness, we first create the server configuration file:

proto udp
port 1194
dev tap

keepalive 10 60

remote-cert-tls client
tls-auth /etc/openvpn/movpn/ta.key 0
dh       /etc/openvpn/movpn/dh2048.pem
ca       /etc/openvpn/movpn/movpn-ca.crt
cert     /etc/openvpn/movpn/server.crt
key      /etc/openvpn/movpn/server.key

user  nobody
group nobody

verb 3
log-append /var/log/openvpn.log

We will reuse this basic tap-mode server configuration file in this chapter and others. Save it as tap-udp-server.conf so...