Rich data: the dark side to Web 2.0 applications
With great programming comes great responsibility
Would you open an HTML document sent to you?
One factor that makes detecting these attacks difficult is that the web enables so many different types of encoding. There are more than 100 different character encodings, and we've added higher level encodings such as percent-encoding, HTML-entity encoding, and bbcode on top of those.
The real nightmare here is that anywhere downstream, systems may decode this data and reawaken a dormant attack. So, even if your application isn't vulnerable to injection, someone might use the data from your application or service.
As Web 2.0 continues to mashup data from different sources, the likelihood of these attacks increases.
Stamp out injection
You should view untrusted data as though it's malicious code and treat it accordingly: validate, separate, and encode.
Validate: have a whitelist input validation rule for every input - no exceptions. Not just for form fields, but hidden fields, URL parameters, headers, cookies, and all backend systems.
Separate: don't mix up the data into command strings. Wherever possible, you should use parameterized interfaces, such as PreparedStatement in Java, that prevent injection by keeping code and data separate.
Show you care
Injection is not a new problem - we've known about it for decades. The body of knowledge on XSS and SQL injection is extensive. If your system forwards an attack to an innocent victim, though, you not only make yourself look bad but in the Web 2.0 world there's a chance your software will lead to wider a proliferation of attacks than was possible in the bad old days.
Jeff Williams is the founder and CEO of Aspect Security and the volunteer chair of the Open Web Application Security Project. His latest project is the Enterprise Security API, a free and open set of foundational security building blocks for developers.
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