Pixel Perfect Timing Attacks with HTML5

Research - Paul Stone - August 2013     

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HTML 5 and related technologies bring a whole slew of new features to web browsers, some of which can be a threat to security and privacy. This paper describes a number of new timing attack techniques that can be used by a malicious web page to steal sensitive data from modern web browsers, breaking cross-origin restrictions.

The new HTML5 requestAnimationFrame API can be used to time browser rendering operations and infer sensitive data based on timing data. Two techniques are demonstrated which use this API to exploit timing attacks against Chrome, Internet Explorer and Firefox in order to infer browsing history and read cross-origin data from other websites. The first technique allows the browser history to be sniffed by detecting redraw events. The second shows how SVG filters can be used to read pixel values from a web page. This allows pixels from cross-origin iframes to be read using an OCR-style technique to obtain sensitive data from websites.

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