[XML-SIG] problem with elementtree 1.2.6

Chris Withers chris at simplistix.co.uk
Fri Nov 30 00:30:59 CET 2007

Fredrik Lundh wrote:
> Chris Withers wrote:
>>> That's how escaping works, be it in XML, encodings, compression, whatever.
>> Well yes and no. I'd expect escaping to work such that whatever we're 
>> dealing with can be round tripped, ie: parsed, serialiazed, parsed 
>> again, etc.
> that's exactly how it works in ET, of course.  

I didn't say it didn't ;-)

> cdata is character data; see
>      http://www.w3.org/TR/html401/types.html#h-6.2
> that's not the same thing as a "CDATA section" (which is just one of 
> several ways to store character data in an XML file). 

Ug. How confusing :-(

> how things are 
> stored doesn't matter; that's just a serialization detail:
>      http://www.w3.org/TR/xml-infoset/#omitted
>      What is not in the Information Set
>      6. Whether characters are represented by character references.
>      19. The boundaries of CDATA marked sections.
>      ...

I'm not sure I follow what you're trying to say...

>> I and many others do not ;-) When writing content into an html template, 
>> that content often comes from other sources that spit out lumps of html. 
>> Being able to insert them without escaping is a common use case.
> HTML might be similar to XML, but an XML parser cannot parse HTML, so 
> you cannot insert HTML fragments into an XML document without either
> escaping it, or pre-processing it to make sure it's well-formed.

What about xhtml?

> if you want to embed HTML fragments in an ET tree, use ElementTidy or 
> ElementSoup (or equivalent) to turn the fragment into properly nested 
> and properly namespaced XHTML.

Fair enough...

> if you want to do unstructured string handling, use a template library 

I'm using/building a templating library, it just happens that ET is an 
implementation detail of that template library ;-)

>> That's true, sometimes. That inserted lump may have come from a process 
>> which can only spit out perfect html fragments, in which case you're 
>> fine, or it may come from user input, in which case you're doomed but 
>> will likely have happy customers ;-)
> the hackers will be happy, at least:
>      http://en.wikipedia.org/wiki/Cross_site_scripting

user -> content author in this case.
Since they usually own and run the system to which they're adding 
content, a much more effective attack would just be to turn the box off :-P



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