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

Combining point-to-point mode with certificates

For the next example, we borrow some bits from Chapter 3, PKIs and Certificates. In client/server mode, OpenVPN is configured using a Public Key Infrastructure (PKI), with X.509 certificates and private keys. It is also possible to use X.509 certificates and private keys to set up a point-to-point tunnel. The advantage of using X.509 certificates over pre-shared keys is that it offers Perfect Forwarding Secrecy (PFS), which greatly enhances the security of your VPN data. Without PFS, if an attacker manages to break the encryption at some point, then all previously recorded VPN traffic can be decrypted. With PFS, it is not possible to decrypt old data.

In order to set up a point-to-point tunnel using certificates, we must first copy over the CA certificate and the certificate/private key pair for both endpoints:

[root@server] # mkdir -p /etc/openvpn/movpn
[root@server] # chmod 700 /etc/openvpn/movpn
[root@server] # cd /etc/openvpn/movpn