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