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Shiflett on the danger of cross-domain AJAX scripting

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Chris Shiflett has posted a good piece in his blog on the potential danger of cross-domain AJAX scripting (digg here).  When Chris and I discussed this at OSCON, I was pretty surprised that anyone would think that violating the same-origin restrictions was in any way a good idea.  His post gives a good example of how dangerous this would be.

CERIAS at Portland OSCON 2006

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Just a reminder: next week I’ll be in Portland at OSCON 2006.  I’ll be moderating the PHP Security Hoedown wednesday night.  If you’re interested in meeting up and talking about web app security stuff or CERIAS, please drop us a line at oscon@cerias.purdue.edu.

The biggest mistake of Myspace

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Myspace, the super-popular web site that your kid uses and you don’t, was once again hit by a worm, this time utilizing Macromedia Flash as its primary vector.  This was a reminder for me of just how badly Myspace has screwed up when it comes to input filtering:

  • They use a “blacklist” approach, disallowing customized markup that they know could be an issue.  How confident are you that they covered all their bases, and could anticipate future problems?  I don’t trust my own code that much, let alone theirs.
  • They allow embed HTML tags.  That means letting folks embed arbitrary content that utilizes plugins, like… Flash. While Myspace filters Javascript, they seem to have forgotten that Flash has Javascript interaction and DOM manipulation capabilities.  If you’re a Myspace user, you may have noticed Javascript alert()-style pop-up windows appearing on some profiles—those are generated by embedding an offsite Flash program into a profile, which then generates Javascript code.

Even if they can plug these holes, it’s unlikely that anything short of a full rewrite/refactorization of their profile customization system can ever be considered moderately secure.

So will Myspace get their act together and modify their input filtering approaches? Very unlikely.  A large portion of Myspace’s appeal relies upon the customization techniques that allow users to decorate their pages with all manner of obnoxious flashing, glittery animations and videos.  Millions of users use cobbled-together hacks to twist their profiles into something fancier than the default, and a substantial cottage industry has sprung up around the subject.  Doing proper input filtering means undoing much of that.

Even if relatively secure equivalent techniques are offered, Myspace would certainly find themselves with a disgruntled user base that’s more likely to bail to a competitor.  That’s an incredibly risky move in the social networking market, and will likely lead Myspace to continue plugging holes rather than building a dam that works.

This is why you can’t design web applications with security as an afterthought.  Myspace has, and I think it will prove to be their biggest mistake.

Hacking the MacBook for Biometric Security

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Via Infinite Loop, I came across an interesting post from a hawdcore MacBook Pro user who bellied up to the bar and retrofitted a Sony fingerprint scanner into his precious Apple laptop.  No indication that the hardware actually interfaces at all with OS X, but it’s pretty cool, and maybe Apple will get some inspiration from this. 8)

OSCON 2006: PHP Security BOF

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So who’s going to OSCON 2006?  I am, and if you are too, drop me a line so we can meet up.  I’m also going to be “moderating” a PHP Security BOF meet, so if you have some interest in PHP Security or secure web dev in general, come by and participate in the chaos.

If you’re planning on going, make sure to check out the official wiki and the OSCamp wiki.