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Re: Bindings and permissions

From: Geoffrey M Clemm <geoffrey.clemm@us.ibm.com>
Date: Sun, 22 Jan 2006 08:54:57 -0500
To: " webdav" <w3c-dist-auth@w3.org>
Message-ID: <OF27BF3350.82BF3142-ON852570FE.004B5CA9-852570FE.004C71D2@us.ibm.com>
Perhaps if you could address the issues raised in my message
(i.e., the ACL spec doesn't support dynamic ACL inheritance,
your suggested changes mistakenly assume that the ACL spec
does support dynamic ACL inheritance, and the issues of 
multiple inheritance occur whether or not you have multiple
bindings to a resource and therefore is not
a bind-specific issue), rather than just stating that you
disagree and re-proposing your changes, we could have a
more productive discussion.

Cheers,
Geoff

Lisa Dusseault <lisa@osafoundation.org> wrote on 01/21/2006 07:09:12 PM:

> I fundamentally disagree that this situation isn't affected by the 
> Bind mechanics and can't be addressed at all in the Bind spec.  It's
> pretty absolute of you to say that there is "nothing that can be 
> changed about the bind spec to address this issue" as I've suggested
> some changes in the past.   
> 
> lisa
> 
> On Jan 21, 2006, at 1:50 PM, Geoffrey M Clemm wrote:
> 
> 
> The issues/questions raised by Lisa are not related to the bind spec; 
> they are about dynamically inherited ACL's, which is not something that 
> is currently modeled in the ACL spec.  So there is nothing that can 
> be changed about the bind spec to address this issue ... it is an ACL 
> spec issue.  If the ACL spec were extended to model dynamically 
inherited 
> ACL's, then it would need to deal with multiple parents, but that is no 
> harder than dealing with the interaction of the ACL directly on a 
resource 
> with the ACL's that it inherits, so multiple bindings does not introduce 

> any new issues in that regard. 
> 
> Cheers, 
> Geoff 
> 
> Cullen wrote on 01/21/2006 04:32:34 PM:
> > Hmm, some of this was before I was following webdav. It does not 
> > surprise me that the IESG said the some proposed ACL model was not 
> > simple enough to implement and requested changes. It would surprise 
> > me greatly that they would be looking for something that was so 
> > simple that it was not capable of solving the problem. 
> > 
> > I suspect the guiding principle here should be as simple as possible
> > but no simpler. Something that does not explants how to deal with 
> > the situations that bind allows either mean that bind need to be 
> > changed to allow less situations or that the solution is not complete. 
 
> 
> > On 12/16/05 6:29 PM, "Geoffrey M Clemm" <geoffrey.clemm@us.ibm.com> 
wrote:
> > There are ways to model this kind of thing, but the guidance we 
> > received for the ACL spec is that the resulting ACL model is too 
> > complicated, which is why we ended up with a much simpler model 
> > (that cannot model this kind of thing).  So I think the simple answer 
> > is "no, there is no way for a client to find out about complex 
> > ACL situations such as the ones you describe" (unless the IESG 
> > changes its mind about how complex an ACL model is acceptable). 
> 
> > Lisa wrote on 12/16/2005 07:13:21 PM:
> > > I was thinking about the bindings and permissions stuff today.  I've 

> > > discussed it before but this may be a new take on the subject. 
 Recall 
> > > we don't really know what the behavior is with dynamically inherited 

> > > ACLs (when a parent's ACLs automatically apply to its child 
resources) 
> > > when some of those children are bindings to resources that also have 

> > > bindings.  Some of the possible solutions to this:
> > > 
> > > 1.  Directory permissions are not dynamically applicable to children 
or 
> > > at least to bindings.
> > > 2.  You can't bind resources into directories that have different 
ACLs 
> > > than where they're bound already - server returns 403 or something
> > > 3.  Permissions are path-dependent.
> > > 4.  Not all bindings are first-class -- there's a "real name" and 
then 
> > > there are aliases.  The collection containing the "real name" is the 

> > > one that inherits permissions
> > > 5.  There's some algorithm for "summing" or "intersecting" the 
> > > permissions according to the parents of all the bindings.
> > > 
> > > There may be other possible models.
> > > 
> > > It seems to me clients have no way of knowing which solution the 
server 
> > > has chosen and behavior can be quite unpredictable.  Is there some 
way 
> > > to advertise the server's model? Are some of these choices 
forbidden?  
> > > Of those that aren't forbidden, is one of them recommended?
> > > 
> > > It would be extremely surprising if the 'bind' privilege grants 
> > > somebody the ability to make a new mapping of a resource into a new 
> > > directory, AND that a consequence of that 'bind' operation is to 
change 
> > > the permissions on the underlying resource -- without requiring 
> > > 'writeacl' privilege.  Since that's a possible security hole, what 
> > > should that be -- a MUST NOT?  A security consideration?
Received on Sunday, 22 January 2006 13:55:01 GMT

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