Network Security with OpenSSL

Chapter 4. Support Infrastructure

The OpenSSL library is composed of many different packages. Some of the lower-level packages can be used independently, while the higher-level ones may make use of several of the lower-level ones. To use the OpenSSL library effectively, it is important to understand the fundamental concepts of cryptography that we’ve already introduced, and to gain familiarity with the more important supplemental package offerings.

In this chapter, we concentrate on the lower-level APIs that are most useful with the higher-level APIs that we discuss through the rest of this book. We’ll start by demonstrating what is necessary when using the OpenSSL library in a multithreaded environment by developing a small “drop-in” library for Windows and Unix platforms that use POSIX threads. We’ll also examine OpenSSL’s error handling and its input/output interface, which are both quite different from how most other development libraries deal with the same things. OpenSSL also provides packages for arbitrary precision math and secure random number generation, as we already mentioned. These packages are both fundamental to strong crypto, and we’ll cover them as well.

For all of the packages that we examine in this chapter, we’ll discuss how to use them and provide examples. Additionally, we’ll discuss some of the common pitfalls that developers often encounter.

Note that if some of the material in this chapter doesn’t seem immediately relevant and interesting, it is safe to ...