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Subject: Re: [regrep-security] FW: [ebxml-msg] XMLDSIG and v1.05 comments


Some comments/responses below.



Damodaran, Suresh wrote:

> Sekhar,
> FYI: My comments on ebXML MSG use of xmldsig
> and response from the editor. I am reposting because
> these would be relevant to our work on Registry xmldsig.
> Cheers,
> -Suresh 
> -----Original Message-----
> From: David Fischer [mailto:david@drummondgroup.com]
> Sent: Tuesday, October 23, 2001 2:24 PM
> To: Damodaran, Suresh; ebxml-msg@lists.oasis-open.org
> Subject: RE: [ebxml-msg] XMLDSIG and v1.05 comments
> I agree on items 1-5 (some of them are REQUIRED).  Since no one has
> commented, I
> will make these changes.  (Comments anyone?)
> I can see some benefits to item 6 (use of the ds:Signature/Manifest) but I
> am
> concerned that it will cause systems not to be Interoperable if some systems
> do
> this and some don't.  Anyone have thoughts?
> Regards,
> David Fischer
> Drummond Group.
> P.S.  Mr. Burdett, would you mind capturing these in the change DB?
> -----Original Message-----
> From: Damodaran, Suresh [mailto:Suresh_Damodaran@stercomm.com]
> Sent: Friday, October 19, 2001 3:44 PM
> To: 'ebxml-msg@lists.oasis-open.org'
> Subject: [ebxml-msg] XMLDSIG and v1.05 comments
> I have some comments and change proposals on Section 4.1.3 Signature
> Generation
> 1. Line 1088 suggests that ds:CanonicalizationMethod element is optional
> in ds:SignedInfo. I don't believe it is true. Section 4.3.1 of XMLDSIG spec
> [1]
> states that "CanonicalizationMethod is a required element that specifies the
> canonicalization algorithm
> applied to the SignedInfo element...". Therefore, I propose we restate the
> sentence
> with a "MUST." Para starting 1090 needs to be rewritten too.

I agree. I think that what happened here is that the intent was to say that
the choice of C14N algorithm was optional (up to the parties to
agree upon). Clearly, the element is REQUIRED.

> 2. I also propose we provide a RECOMMENDED algorithm for
> CanonicalizationMethod as
> http://www.w3.org/TR/2001/REC-xml-c14n-20010315 (this one omits comments)
> e.g.,
> <ds:CanonicalizationMethod
> Algorithm="http://www.w3.org/TR/2001/REC-xml-c14n-20010315"/>

That would be fine, but some consideration should be given to
providing guidance as to what implications there might be in
excluding comments. It may be that the comments are significant...
Both the with and without comments algorithms are REQUIRED to be
supported by conformant XMLDSig implementations, so either
should be acceptable.

> 3. Sentence on line 1100 says that the signature is calculated over the SOAP
> Header. I would argue that the signature be calculated over
> SOAP-ENV:Envelope instead of SOAP-ENV:Header. This would include the
> <eb:Manifest> in the SOAP-ENV:Body. Why is this needed? It is possible that
> ds:Signature element is eliminated from the message after signature
> validation is done. Beyond that point, the application would look at
> eb:Manifest to locate the resources. Therefore, the integrity of eb:Manifest
> element is important. The change from SOAP Header to SOAP Envelope needs to
> be made in the whole section.
> 4. Line 1107 talks about the ds:Transform elements. I propose we add another
> REQUIRED ds:Transform
> element
> <ds:Transform Algorithm="http://www.w3.org/TR/2001/REC-xml-c14n-20010315"/>
> for the SOAP Envelope after the "enveloped-signature" transform. This new
> transform will make sure the SOAP envelope is canonicalized before signed.

I don't believe that this is necesary. It is redundant is it not?

> 5. Line 1120 suggests that URI attribute need not match the manifest
> reference. I don't know what purpose this serves. I propose we delete
> "However, this is NOT REQUIRED"
> 6. Line 1103: The Type attribute is optional according to the spec. Note
> that if the reference type is
> not manifest [http://www.w3.org/TR/xmldsig-core/#sec-Manifest]  the
> reference (i.e., payload) is required to be
> validated as per XMLDSIG. We may want to give more control to the
> application on validation. Therefore, mention of the manifest Type would be
> good. The manifest itself is an ds:Object which is an element of
> ds:Signature. I propose we REQUIRE the type attribute for the Reference
> element of SOAP Envelope with a value of either
> http://www.w3.org/2000/09/xmldsig#Object or
> http://www.w3.org/2000/09/xmldsig#Manifest.

I'm not sure I agree. I don't think that you want to give this
level of control to the application. The purpose of the signature
is to provide for integrity of the message. If the signature validation
fails, it means that the message may have been tampered with in transit.

> ----------------------------------------------------------------------------
> ----------------------------------------
> [1] XML-Signature Syntax and Processing - W3C Proposed Recommendation
> http://www.w3.org/TR/xmldsig-core/
> Cheers,
> -Suresh
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