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

Session key renegotiation

To ensure the security of each OpenVPN connection, the server periodically renegotiates the secret key for the data channel with each client. This is controlled using three options:

  • reneg-sec N: Renegotiate data channel key after N seconds (default is 3600)

  • reneg-bytes N: Renegotiate data channel key after N bytes (default=0=off)

  • reneg-pkts N: Renegotiate data channel key after N packets (default=0=off)

If a VPN client is experiencing periodic timeouts when connected to the server, it is often useful to vary these parameters. If you set the reneg-sec parameter at a very short interval, however, the performance of the VPN will be severely degraded.

The reneg options can be specified on either the client or the server side, or both. The reneg option that runs the most frequently on either side will reset the counters on both ends. If the server specifies reneg-sec 500 but the client specifies reneg-sec 60, then the data channel renegotiation will occur approximately...