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

Fixing common configuration mistakes

When setting up an OpenVPN configuration, there are a few common mistakes that are easily made. These configuration mistakes can be roughly divided up into four categories:

  • Certificate (PKI) errors and mismatches

  • Option mismatches, such as tun versus tap, ciphers, and compression

  • Insufficient privileges to run OpenVPN

  • Routing mistakes

In this section, we will go through the first three of these categories. Routing mistakes will be discussed later in this chapter.

Wrong CA certificate in the client configuration

The client configuration file will almost always contain three lines like this:

ca ca.crt
cert client.crt
key client.key

These certificate and private key files were created in Chapter 3, PKIs and Certificates, and are used extensively in subsequent chapters.

The CA file, however, does not need to specify the certificate authority that was used to sign the client certificate file. It must be the public certificate of the certificate authority that was...