W3C home > Mailing lists > Public > w3c-ietf-xmldsig@w3.org > April to June 2001

RE: signature portability / C14N / inherited namespaces

From: John Boyer <JBoyer@PureEdge.com>
Date: Wed, 16 May 2001 08:56:44 -0700
Message-ID: <7874BFCCD289A645B5CE3935769F0B520C33D1@tigger.PureEdge.com>
To: "merlin" <merlin@baltimore.ie>, "Rob Lugt" <roblugt@elcel.com>
Cc: <w3c-ietf-xmldsig@w3.org>

Hi Merlin and Rob,

The group discussed this issue at length before deciding on the current
methodology.  If a namespace attribute is not being used anywhere within
a document subset, and it is inheriting that declaration from the
outside, then there is no good reason to keep the namespace declaration.
But if a namespace declaration is inherited from the outside and it *is*
being used, then moving the document subset from one context to the
other changes the meaning of the signed information without breaking the
signature.  The group's decision to always import the full namespace
context was based on the relative difficulty of assessing whether a
namespace attribute is actually being used.  It seemed a passable if not
desirable compromise to put some onus on the application creating the
signatures to capture the contexts under which they might be
transported, even if such must be done dynamically.   

At a minimum, the fact that my signature was taken from some context and
placed into another means that there is already not that much of a
burden to take my signature back out of the foreign context before
trying to validate it.  The fact that one XML syntax might be meant as a
container for elements in other namespaces does not mean that those
other elements can retain their exact meaning when in the container.  To
wit, many document processors will report errors if the root document
element does not have the tag that they are expecting to process.  The
element must be removed from the container before it can be used.

John Boyer
Senior Product Architect, Software Development
Internet Commerce System (ICS) Team
PureEdge Solutions Inc. 
Trusted Digital Relationships
v: 250-708-8047  f: 250-708-8010
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-----Original Message-----
From: merlin [mailto:merlin@baltimore.ie]
Sent: Wednesday, May 16, 2001 7:29 AM
To: Rob Lugt
Cc: w3c-ietf-xmldsig@w3.org
Subject: Re: signature portability / C14N / inherited namespaces 

Hi Rob,

>One last try at a workable solution whilst adhering to the c14n
>specification:- re-use the same namespace prefix from the SOAP header.
><ns:Envelope xmlns:ns="http://schemas.xmlsoap.org/soap/envelope/">
> <ns:Body>
>  ...
>  <Contract xmlns="&foo;">
>   <ns:Signature xmlns:ns="&dsig;">...</ns:Signature>
>  </Contract>
> </ns:Body>
>I think the namespace prefix should ideally be a descriptive name which
>makes this solution less than elegant.  But perhaps it satisfies your
>current requirement?

I've actually solved it for myself by using a framework that can
defer signing until the final document is complete. This is okay
for my particular needs, but it won't work for someone who is
using, for example, Apache's SOAP framework (which never builds
a DOM tree, but instead manually marshals the SOAP envelope in
text format*) or who has no control over the final embedding of
their signature.

My concern really revolves a bit more around interop and the dsig
spec than this particular instance.


* It does make the namespace available, but not through DOM.

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Received on Wednesday, 16 May 2001 11:58:48 UTC

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