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RE: Interop issue: how can clients force authentication?

From: Julian Reschke <julian.reschke@gmx.de>
Date: Mon, 21 Oct 2002 10:47:10 +0200
To: <w3c-dist-auth@w3.org>
Message-ID: <JIEGINCHMLABHJBIGKBCAEOFFJAA.julian.reschke@gmx.de>


a few comments:

- trying to set a dead property before going on with resource modifications
certainly is interoperable,

- I don't think that the information "which methods can I invoke with the
current credentials" belongs into a live property -- it certainly sounds
like an additional optional REPORT (for which support can be detected using

- I've got the feeling that this isn't how authentication should work in
HTTP. Either you are authenticated, or you aren't. If your current
privileges are not sufficient for a specific method, you'll get a 403. IMHO,
if a client thinks that it might succeed with different credentials, it
should be initiate the new authentication itself.


<green/>bytes GmbH -- http://www.greenbytes.de -- tel:+492512807760

> -----Original Message-----
> From: w3c-dist-auth-request@w3.org
> [mailto:w3c-dist-auth-request@w3.org]On Behalf Of Dan Brotsky
> Sent: Wednesday, October 16, 2002 5:52 PM
> To: w3c-dist-auth@w3.org
> Cc: Dan Brotsky
> Subject: Re: Interop issue: how can clients force authentication?
> The problem: Before starting a sequence of requests on a resource, a
> client wants to ensure that it is authenticated as a principal who is
> authorized to perform all the various methods in the sequence.  If it
> is not so authenticated, it wants to be rechallenged so it can
> reauthenticate.
> The proposal (with thanks but no blame to Julian): The client sends a
> (probably unauthorized) request to PROPPATCH the DAV:authorized-methods
> property of the resource with an methods element containing a
> checkauthorization element and elements for each of the methods it
> wishes to use.
>    <!ELEMENT methods (checkauthorization? options? get? put? mkcol?
> lock? ...) >
>    <!ELEMENT checkauthorization EMPTY >
>    <!ELEMENT options EMPTY >
>    <!ELEMENT get EMPTY >
>    ...
>    (extra credit: guess who desperately needs Julian, Stefan, and Geoff
> to fix his XML...)
> In the wonderfully-future-compliant case: the server actually looks at
> the value of the property specified, and continues to challenge (401)
> the client until the client authenticates as a user who is actually
> authorized to perform all those methods on that resource.  At that
> point the server return 409 because (ha!) DAV:authorized-methods is
> actually a read-only property.
> In the currently compliant server case: the server just
> authenticates/authorizes the user for the PROPPATCH on the resource,
> and then either sets the (dead) property or refuses the request (403,
> presumably), because the user is trying to set a property in the DAV:
> space that's not mentioned in the current version of the spec. :^)
> ----------
> PROPOSED LANGUAGE (first shot, sort of):
> - Define the property DAV:authorized-methods as a live property whose
> value is a methods element.
> - A server SHOULD return, as the result of a PROPFIND on
> DAV:authorized-methods, EITHER the set of methods that the requesting
> principal is authorized for over that resource OR 404 Not Found
> (meaning the server doesn't want to or is unable to tell you).
> - A server MAY treat DAV:authorized-methods as a dead property (for
> backward compatibility).
> - If a client attempts to PROPPATCH the value of
> DAV:authorized-methods, it MUST use a checkauthorization element as the
> first member of the property, and it MUST include all the methods that
> it want to check authorization for.
> - Servers SHOULD respond to client attempts to PROPPATCH the value of
> DAV:authorized-methods by responding with 401 until the client
> authenticates as a principal authorized to perform all such methods on
> the target resource (if there were a target resource).
> - Servers MAY respond to client attempts to PROPPATCH the value of
> DAV:authorized-methods as if DAV:authorized-methods were a dead
> property.
> ----------
> Some impressions and issues:
> 1. Sheesh.  What a hack.  But at least it covers the fairly common case
> of servers that authorize LOCK, PUT, PROPPATCH, UNLOCK (and usually
> DELETE) the same way.  Those servers just treat the new property as
> dead, and clients get what they want.
> 2. What exactly happens if you PROPPATCH an URL that's not bound to a
> resource, anyway?  That's going to be a very common case if you were
> planning to LOCK the resource first, and you probably don't want the
> server creating the resource on the PROPPATCH.
> OK, folks, have at it! :^)
>      dan
Received on Monday, 21 October 2002 04:47:55 UTC

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