Subject: DSig support in Aggregators

From: Robert Sayre <[email-masked]>
Date: Tue, 24 Aug 2004 12:42:36 -0400

PaceDigitalSignatures:
"Atom consumers MUST be able to parse XMLDSig content to extract the 
Atom content, even if they cannot do any signature validation. Atom 
consumers MUST NOT reject an Atom item simply because it is signed."

Is this a reasonable demand to make? Could it be a SHOULD?

Do any aggregators support this now?

Robert Sayre

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From: Paul Hoffman / IMC <[email-masked]>
Date: Tue, 24 Aug 2004 09:58:18 -0700

At 12:42 PM -0400 8/24/04, Robert Sayre wrote:
>Is this a reasonable demand to make?

Yes. Parsing XMLDSig to find the Atom content is pretty trivial if 
you know know to parse XML at all, particularly if we do not allow 
signature enveloping (and, even better, if we pick a SHOULD for the 
style of signing).

>  Could it be a SHOULD?

Sure, but then we would not have any interoperability for signed 
content. Remember, the person who is deciding whether or not to sign 
an entry has no idea who will eventually read it. This is the 
opposite of encrypting entries, which requires that the sender know 
which recipient can read it.

If being able to read signed content is only a SHOULD, no one will 
sign anything unless they know they are in a closed environment. That 
will lead to the same mess we have in the email world. We have the 
opportunity to go well beyond that.

>Do any aggregators support this now?

Why is that relevant? We're writing a standard that is meant to be 
useful for decades in the future. Restricting it to features that 
already exist in pre-standards software hobbles it significantly.

--Paul Hoffman, Director
--Internet Mail Consortium

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From: "Bob Wyman" <[email-masked]>
Date: Tue, 24 Aug 2004 13:13:06 -0400

> Is this a reasonable demand to make? Could it be a SHOULD?
	The problem here may be the wording -- not the intent. The Pace
says: "Atom consumers MUST be able to parse XMLDSig content...". However, if
we accept the limitation that no enveloping signatures are allowed, then the
only real requirement is that consumers must be able to at least ignore the
signatures. (Yes, this involves "parsing". However, it only requires XML
parsing -- not any particular knowledge of XMLDSig.)
	It is reasonable to say that the mere presence of a signature, or
other unrecognized XML content, should not cause an entry to be dropped. 

		bob wyman

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From: Graham <[email-masked]>
Date: Tue, 24 Aug 2004 10:20:44 -0700

> Is this a reasonable demand to make? Could it be a SHOULD?

I don't know how easy is it? What do I have to do? I don't think it's 
reasonable to assume we all know, or we can have a decent discussion 
here if we all have to look it up.

Graham

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From: Mark Pilgrim <[email-masked]>
Date: Tue, 24 Aug 2004 13:29:18 -0400

> other unrecognized XML content, should not cause an entry to be dropped.

Yes, this was my thinking for restricting it to non-enveloping
signatures -- current aggregators already ignore stuff in random
namespaces they don't understand, so a Signature element in the DSig
namespace shouldn't pose a problem for existing clients that don't
care about signed content.

My original message spells this out in more detail, and has what I
believe are syntactically correct examples:

http://www.imc.org/atom-syntax/mail-archive/msg06963.html

-- 
Cheers,
-Mark

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From: Paul Hoffman / IMC <[email-masked]>
Date: Tue, 24 Aug 2004 10:56:48 -0700

>other unrecognized XML content, should not cause an entry to be dropped.

Almost. The mere presence of a signature MUST NOT cause an entry to 
be dropped. Without that mandate, someone will drop them and claim 
conformance, and people will stop signing. This is a true 
interoperability issue.

--Paul Hoffman, Director

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From: Robert Sayre <[email-masked]>
Date: Tue, 24 Aug 2004 13:58:56 -0400

Mark Pilgrim wrote:
>> However, if
>>signatures. 

> signatures...

Note that Paul (the Author) +1ed Mark's suggestion of disallowing 
enveloping signatures[0]. Paul, do you still agree?

In order for this line of thinking to move forward, we need:

* Revised spec text stating that "enveloped signatures are *not* OK", 
and possiblity recommending a signature style (enveloped, detached 
sibling, or detached external).
* "a standard 'Atom-ish' way of linking to externally stored signatures"

Robert Sayre

[0]
http://www.imc.org/atom-syntax/mail-archive/msg07019.html

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From: Antone Roundy <[email-masked]>
Date: Tue, 24 Aug 2004 12:49:47 -0600

Current text: "Atom consumers MUST be able to parse XMLDSig content to 
extract the Atom content,
even if they cannot do any signature validation. Atom consumers MUST 
NOT reject
an Atom item simply because it is signed."

If restricting to non-enveloping signatures (+1 to that), perhaps this: 
"Atom consumers MAY ignore XMLDSig content, but MUST NOT reject an Atom 
item simply because it is signed."

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From: Paul Hoffman / IMC <[email-masked]>
Date: Tue, 24 Aug 2004 11:56:52 -0700

>enveloping signatures[0]. Paul, do you still agree?

Yes. My preference would have been to allow enveloping signatures, 
but Mark points out:

- this is hard for some receivers

- we have other choices

>* Revised spec text stating that "enveloped signatures are *not* 
>OK", and possiblity recommending a signature style (enveloped, 
>detached sibling, or detached external).

Right. Do folks here have a preference between sibling or child 
signatures? My first thought is "child" for neatness, but that's a 
weak preference.

--Paul Hoffman, Director

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From: Dave Pawson <[email-masked]>
Date: Tue, 24 Aug 2004 20:27:22 +0100

> signatures? My first thought is "child" for neatness, but that's a 

Child, of the item being signed, 
  but optional please.

-- 
Regards DaveP.
XSLT&Docbook  FAQ
http://www.dpawson.co.uk/xsl

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From: "Bob Wyman" <[email-masked]>
Date: Tue, 24 Aug 2004 17:51:49 -0400

Paul Hoffman wrote:
> signatures? My first thought is "child" for neatness, but that's
> a weak preference.
	+1 for child, not sibling. Neatness is important... After all, as
many children know: "Cleanliness is next to Godliness..."

		bob wyman

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From: Asbjørn Ulsberg <[email-masked]>
Date: Wed, 25 Aug 2004 21:54:26 +0200

On Tue, 24 Aug 2004 11:56:52 -0700, Paul Hoffman / IMC <[email-masked]>  
wrote:

> Do folks here have a preference between sibling or child signatures?

Optional child element is my preference.

-- 
Asbjørn Ulsberg         -=|=-        [email-masked]
«He's a loathsome offensive brute, yet I can't look away»