RE: [xml-dev] Interesting mailing list & a rare broadside

["Dare Obasanjo" <dareo@microsoft.com>]

> -----Original Message-----
> From: James Clark [mailto:jjc@jclark.com] 
> Sent: Friday, June 07, 2002 8:35 PM
> To: Dare Obasanjo; xml-dev@lists.xml.org
> Subject: RE: [xml-dev] Interesting mailing list & a rare broadside
>
> So, are you saying that the answer to my question is 
> basically "no", since 
> there is always the possibility that the root element of the 
> instance will 
> use a namespace not in the schema cache?
> 
> If that's so, although it's perfectly conformant, it seems 
> like a fairly 
> major potential security/robustness hole.  Suppose an 
> application is trying 
> to use validation to protect itself from bad input. It 
> carefully loads the 
> schema cache with the namespaces it knows about, and calls 
> validate().  Now 
> the bad guy comes along and uses a root element from some 
> other namespace 
> and uses xsi:schemaLocation to point to his own schema that 
> that has a 
> declaration for that element and uses <xs:any namespace="##any" 
> processContents="skip"/>.  Won't they just have almost completely 
> undermined any protection that was supposed to come from validation?

That is an interesting theoretical attack which I don't think anything
in the W3C XML Schema recommendation prevents. You bring up a good point
which I'll have to discuss with our resident W3C XML Schema folks when
they get in on Monday. 
 
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