[Twisted-web] Preventing XSS when using Nevow's vhost functionality

David Reid dreid at dreid.org
Thu Oct 20 13:06:35 MDT 2005

On Oct 19, 2005, at 4:39 PM, David Remahl wrote:
> I'm not sure your PoC encapsulates precisely the problem I  
> described, but it is a valid variant which doesn't require as many  
> preconditions (but is not possible to exploit in some browsers,  
> such as Safari, that won't trust JS from another host even if  
> directly referenced from goody). I think I should clarify that in  
> my example, goody.com and evil.net are two sites that _are_ indeed  
> served by the same nevow application. They each have their own  
> little space on the same server, but they don't administer the  
> application serving their content. I guess that's what you refer to  
> as "sister applications".

I just wrote this very long email about your suggested exploit, and  
then realized that the example configuration I imagined wouldn't  
cause the type of behavior you describe.   I can imagine a very  
complicated configuration that invovling 3  
vhost.VHostMonsterResources and 1 NameVirtualHost might allow someone  
to suddenly jump between two domains in the NameVirtualHost (at the  
urging of an attacker) but I haven't tried to put together a PoC. If  
this is in fact the configuration you're suggesting I only have this  
to say I can not think of a single use case for vhost.NameVirtualHost  
vhost.VHostMonsterResource being used today in a configuration such  
as what I believe you to be describing.  But if there is a use-case  
I'm honestly not sure there is a way to make it work without properly.

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