Network Security with OpenSSL

Chapter 2. Command-Line Interface

OpenSSL is primarily a library that is used by developers to include support for strong cryptography in their programs, but it is also a tool that provides access to much of its functionality from the command line. The command-line tool makes it easy to perform common operations, such as computing the MD5 hash of a file’s contents. What’s more, the command-line tool provides the ability to access much of OpenSSL’s higher-level functionality from shell scripts on Unix or batch files on Windows. It also provides a simple interface for languages that do not have native SSL bindings, but can run shell commands.

There’s no question that the command-line tool can seem quite complex to the uninitiated. It sports a large set of commands, and even larger sets of options that can be used to further refine and control those commands. OpenSSL does come with some documentation that covers most of the available commands and options supported by the command-line tool, but even that documentation can seem intimidating. Indeed, when you’re trying to discover the magical incantation to create a self-signed certificate, the documentation provided with OpenSSL does not provide an intuitive way to go about finding that information, even though it is in fact buried in there.

This chapter contains an overview of the command-line tool, providing some basic background information that will help make some sense of how the tool’s command structure is organized. We’ll also ...