Re: [ebxml-msg] Issue73:http://schemas.xmlsoap.org/soap/envelopenamespace

[Christopher Ferris <chris.ferris@sun.com>]

Doug,

I agree with all your points on the importance of
validating the received messages before processing... However,
SOAP does not *require* either DTD processing or XML Schema
validation. This does not preclude XML Schema validation
to assess the validity of the received message. I thnk that
at best we can *strongly recommend* that the practice
of validating the received message(s) against the XML
Schema instance to assure receipt of a both well-formed
and valid message before turning it over to further
processing by the MSH. I don't think that we can
necessarily *require* that this be done.

w/r/t the process=lax v strict issue, that raises an
interesting point that probably should be addressed
by the XML Protocol WG regarding the SOAP schema.

Cheers,

Chris

Doug Bunting wrote:

> While writing my previous email (on issue 56) to Dick, I recognised an 
> assumption not supported in the document (I think).  I've been assuming 
> the receiver MUST (at least SHOULD) validate a message against the ebXML 
> Messaging schema.  If that's not supported by our documentation and the 
> SOAP envelope schema, we're in a whole world of security hurt.  (Just 
> for example, code is often written assuming something is in the DOM tree 
> because the schema requires its presence.  That code fails in ugly ways 
> when those assumptions are violated by an non validating XML parser.)  
> Due to the changes currently proposed resolving issue 73, I don't think 
> we have the assurance of XML validation if we ever did in the past.
> 
>  
> 
> Two things determine whether or not an XML instance is validated against 
> a schema.  First, the parser responsible for reading the instance must 
> be configured to perform validation.  I don't recall whether or not SOAP 
> requires such a parser configuration.  Second, the specific elements of 
> interest must be declared within a processContents="strict" block.  
> Without strict interpretation of the block, a validating 
> parser MAY or MUST (depending on the precise declaration) skip the block.
> 
>  
> 
> The schema found at [1] does not match our hacked version at [2] in one 
> important way: The one we threw together for our own use required 
> validation of the SOAP extension elements found in the Envelope and 
> Header.  [2] instead uses processContents="lax".  This means a 
> validating parser MAY skip the contents of the Header and Envelope elements.
> 
>  
> 
> [1] http://schemas.xmlsoap.org/soap/envelopenamespace
> 
> [2] http://www.oasis-open.org/committees/ebxml-msg/schema/envelope.xsd
> 
>  
> 
> To make the suggested change to our msg-header.xsd file, we must change 
> the document in a few more ways than previously suggested.  In addition 
> to removing mention of our specific schema location for the SOAP 
> namespace, we must STRONGLY RECOMMEND the XML parser be configured to 
> interpret processContents="lax" as processContents="strict".   (I'd 
> prefer MUST to avoid long sentences describing requirements in this 
> area for any level of security assurance.)  If the SOAP specification 
> doesn't do this for us already, we should also require the XML parser to 
> validate received documents.
> 
>  
> 
> thanx,
> 
>     doug
> 
>  
>