[xml] XML and canonicalization

[Marius Kjeldahl <marius kjeldahl net>]

I'm working on a project which require messages to be signed using a 
<Signature> tag inside the XML document. This again requires canonicalization 
of the xml document before signing, and I am having trouble finding 
utilities/code that demonstrate canonicalization.

According to the homepage of the XML C library for Gnome (libxml2), this may 
be supported already - the homepage says:

"Canonical XML Version 1.0: http://www.w3.org/TR/xml-c14n and the Exclusive 
XML Canonicalization CR draft http://www.w3.org/TR/xml-exc-c14n "

I've searched through the mailing list archives and the include files for 
libxml2, but I can not find anything related to canonicalization in libxml2.

I did find a perl module that claims to do canonicalization, which again is 
built on top of gdome. I've looked through gdome, and can not find "canonical" 
mentioned anywhere in the source there either.

I've also checked the expat library, and according to the docs, calling xmlwf 
with the -d parameter supposedly generate canonical xml output. When I test 
this utility, I do get a new xml document which has been reformatted 
(replacing my linefeeds with "&#10;" sections. The document output from xmlwf 
_may_ be correct according to the standard for canonicalization, but since 
this is the only ready-to-use example I have found it is hard to validate.

Anyway, do you know about the status on canonicalisation on the the gnome xml 
projects (libxml2 and gdome2), and/or have other information about where I can 
get actual code using any library that does canonicalization?

Yes, I know where to find the standard, but before trying to interpret and 
implement it myself, I was hoping some of the XML specialists had done this 
already.

Anyway, thanks for any hints you may have.

Marius Kjeldahl