Web Application Security

Chapter 25. Defending Against Injection

Previously we discussed the risk that injection-style attacks bring against web applications. These attacks are still common (although more common in the past), typically as a result of improper attention on the part of the developer writing any type of automation involving a CLI and user-submitted data.

Injection attacks also cover a wide surface area. Injection can be used against CLIs or any other isolated interpreter running on the server (when it hits the OS level, it becomes command injection instead). As a result, when considering how we will defend against injection-style attacks, it is easier to break such defensive measures up into a few categories.

First off, we should evaluate defenses against SQL injection attacks—the most common and well-known form of injection. After investigating what we can do to protect against SQL injection, we can see which of those defenses will be applicable to other forms of injection attacks. Finally, we can evaluate a few generic methods of defense against injection that are not specific to any particular subset of injection-based attack.

Mitigating SQL Injection

SQL injection is the most common form of injection attack, and likewise one of the easiest to defend against. Since it is so widespread, potentially affecting nearly every complex web application (due to the prevalence of SQL databases), many mitigations and countermeasures have been developed against SQL injection.

Furthermore, because ...