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Re: [Full-disclosure] Exploiting sibling domains cookie isolation policy to DoS CDN users



On Thu, Apr 11, 2013 at 05:01:57PM +0200, Jan Wrobel wrote:
> Hello,
> 
> In short:
> 
> Browsers can be easily cut from any resources hosted on Content
> Delivery Networks that use a domain shared between users, by a visit
> to a malicious site that sets large number of cookies on the common
> prefix of the CDN domain.
> 
> For example, an HTML document on 'foo.rackcdn.com' (visited directly
> or iframed) can set large number of large cookies with a domain
> attribute set to 'rackcdn.com'. This prevents the browser from
> accessing any content on '*.rackcdn.com'. A single site can target
> multiple CDNs at once.
> 
> More detailed writeup:
> http://mixedbit.org/blog/2013/04/11/dos_attack_on_cdn_users.html

Wow, interesting!

CDNs could mitigate this by, instead of resetting connections with lots of 
headers,
just reading all the cookies and throwing them into the bit bucket instead of 
keeping
them in RAM, right? That way, there would still be the wasted bandwidth, but
combined with the Google approach, it should work fine, right? If the client 
sends too
many headers, just ignore everything until you reach \n\n, then send back the 
error
script?

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