Saturday, May 15, 2010

Subverting Ajax

I write this on 9/15/08 but never published it for some reason. The paper I'm discussing is still interesting, though, so here's the post, years late!

Today's paper is Subverting Ajax which was published in December 2006 at the 23rd Chaos Communication Congress. It is, as one might expect from the title, an overview of ways in which Ajax (Asynchronous JavaScript And XML) can be compromised.

You might think that since this paper was from 2006, many of these flaws would be closed, but sadly, the paper seems to retain its relevancy even in 2008.

Although the focus of this paper is on Ajax, particularly the case in which an attacker has placed another layer of communication "between" the browser and the server, it also covers a number of techniques that can be used in any JavaScript based attack. For example, the wrapper used around the built-in XMLHttpRequest could potentially be used to subvert any built-in JavaScript object. Also clever is the use of proxies and iframes. To be honest, the attacks I've seen in the wild have not been this complex, but if we ever close the obvious holes we can expect that more subtle attacks would happen, and it's good to understand them in advance.

The one downside to this paper is that it is clear the the authors are not native English speakers, and I'm sorry to admit that there were places where I found their use of language distracting.

Overall, I'll have to recommend the paper, as it was recommended to me, but I have high hopes that will produce easier to read documentation on Ajax-specific threats one of these days.

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