Site Security Policy

June 8, 2008 – 8:18 AM

OK gang, this is one of those rare moments where feedback from community will directly influence a security feature that’ll make a real difference. First some background…

About 6 months ago Brandon Sterne left a cushy infosec position at eBay for Mozilla to solve an extremely important Web security problem he couldn’t while he was there. The same exact problem a lot of major website properties have including Google, Yahoo, MySpace, Microsoft, Facebook and so on. Where business requirements say that users must be able to upload dynamic content (HTML/JavaScript) where it’ll interact with other users. The other being including CDN content (advertising) supplied by multiple unknown upstream providers. We all know the damage this stuff do when abused.

Unfortunately browsers lack any mechanism to specify what the content on its website should be able to do and where its supposed to originate. When accepting user-supplied dynamic content on a website, it’s all or nothing. Website owners need more granularity. This is where the idea of content-restrictions came from years ago, ironically by RSnake whom also worked for eBay years back. The idea never really got off the paper and into browser code despite a lot experts, including myself, pleading for even a limited implementation. This is where Brandon comes in and this presentation on “Web Application Security and the Browser” he recently gave during Yahoo Security Week.

Brandon is in the process of creating Site Security Policy, a specification for people to comment on and proof-of-concept extension for people to play around with. He’s got policy provisions worked in to help prevent XSS, CSRF, and even Intranet Hacking. Brandon even has some cool client-side IDS stuff worked in. The vision is to later formalize the specification through W3C and integrate the feature natively into the browser once trouble spots are ironed out.

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