“It Depends”

In my research and writings that I’ve already done, I’ve noticed something about trying to share helpful security advice to fellow developers – you can provide all of the code examples and describe the threats all you want, but the problem really boils down to two words:

“It depends”

Much like other development-related issues, there’s a lot of things you have to take into consideration when thinking about the security of your application. Code security by itself is good, and there’s some best practices for that that have been shared all over the web. Unfortunately, this only paints a small part of the picture. Web applications, by their nature, are really complex systems composed of multiple pieces of software all running together to make this useful, functional service for its consumers. If you’re a PHP developer, there’s things you can do to help prevent common attacks (like XSS, CSRF or SQL injection to name some popular ones), but unless you look at the bigger picture, you’re getting a false sense of security.

“But I’m only responsible for the code!” you say. You like the idea that your code can be as secure as possible by filtering output, escaping user input and using defensive coding techniques. You commit your code, run your tests and happily go about your business, thinking things are good. Unfortunately, if you don’t consider the ecosystem your application lives in, chances are you missed something.

I’m not talking about code challenges here – preventing things like XSS or SQL injections is relatively easy (as long as you know what to do). The problems I’m talking about are things that may be true for one environment but not for another – things like:

  • Working with multiple databases and storing their credentials securely
  • Effective logging to a remote syslog server
  • Potentially protecting your data from a physical intrusion
  • Working with sensitive data
  • Bridging authentication/authorization across applications
  • Concurrency issues coming from multiple installations of the same application

While a lot of these kinds of concerns revolve around the architecture of the application, developers still need to keep them in mind when creating their applications. At the very least, you need to keep these kinds of concerns in mind when writing your code. Like anything else, there’s ways to structure the code to make things like this simpler to change. The trick is to keep things loosely coupled enough to make life simpler down the road.

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