Re: Bindings and permissions

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).

Cheers,
Geoff


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?
> 
> Lisa
> 
>