Organization of This Book

Because this book is a cookbook, the text is not presented in tutorial style; it is a comprehensive reference, filled with code that meets common security needs. We do not intend for this book to be read straight through. Instead, we expect that you will consult this book when you need it, just to pick out the information and code that you need.

To that end, here is a strategy for getting the most out of this book:

• Each recipe is named in some detail. Browse through the table of contents and through the list of supplemental recipes on the book's web site.

• Before reading appropriate recipes, take a look at the chapter introduction and the first few recipes in the chapter for fundamental background on the topic.

• Sometimes, we offer a general recipe providing an overview of possible solutions to a problem, and then more specific recipes for each solution. For example, we have a generic recipe on buffer overflows that helps you determine which technology is best for your application; then there are recipes covering specific technologies that couldn't have been covered concisely in the overview.

• If particular concepts are unclear, look them up in the glossary, which is available on the book's web site.

• Throughout each recipe, we detail potential "gotchas" that you should consider, so be sure to read recipes in their entirety.

The book is divided into 13 chapters:

Chapter 1, Safe Initialization, provides recipes for making sure your programs are in a secure state on startup and when calling out to other programs.

Chapter 2, Access Control, shows how to manipulate files and directories in a secure manner. We demonstrate both the Unix permissions model and the Windows access control lists used to protect files and other resources.

Chapter 3, Input Validation, teaches you how to protect your programs from malicious user input. In this chapter, we demonstrate techniques for preventing things like buffer overflow problems, cross-site scripting attacks, format string errors, and SQL-injection attacks.

Chapter 4, Symmetric Cryptography Fundamentals, covers basic encoding and storage issues that are often helpful in traditional encryption.

Chapter 5, Symmetric Encryption, shows how to choose and use symmetric encryption primitives such as AES, the Advanced Encryption Standard.

Chapter 6, Hashes and Message Authentication, focuses on ensuring data integrity using message authentication codes.

Chapter 7, Public Key Cryptography, teaches you how to use basic public key algorithms such as RSA.

Chapter 8, Authentication, shows you how to manipulate login credentials. We focus on implementing password-based systems as securely as possible, because this is what most people want to use. Here we also cover a wide variety of technologies, including PAM and Kerberos.

Chapter 9, Networking, provides code for securing your network connections. We discuss SSL and TLS, and also describe more lightweight protocols for when you do not want to set up a public key infrastructure. We strongly encourage you to come here before you go to the cryptography chapters, because it is exceedingly difficult to build a secure network protocol from parts.

Chapter 10, Public Key Infrastructure, is largely a supplement for Chapter 9 for when you are using a public key infrastructure (PKI), as well as when you are using the SSL/TLS protocol. In this chapter, we demonstrate best practices for using a PKI properly. For example, we show how to determine whether certificates have expired or are otherwise invalid.

Chapter 11, Random Numbers, describes how to get secure random data and turn such data into an efficient and secure stream of pseudo-random numbers.

Chapter 12, Anti-Tampering, gives you the foundations necessary to start protecting your software against reverse engineering. There are no absolute solutions in this area, but if you are willing to put a lot of effort into it, you can make reverse engineering significantly more difficult.

Chapter 13, Other Topics, contains a potpourri of topics that did not fit into other chapters, such as erasing secrets from memory properly, writing a secure signal handler, and preventing common attacks against the Windows messaging system.

In addition, our web site contains a glossary providing a comprehensive listing of the many security-related terms used throughout this book, complete with concise definitions.