[cap-talk] Semantics : is this a capability system & am I using
the right semantics? (fwd)
capibara at xs4all.nl
Wed Apr 13 03:41:02 EDT 2005
On Tue, 12 Apr 2005, Jed at Webstart wrote:
> <Did the above comment by Rob go to the list? I didn't see it.>
I seem to have send it to have been replying to the list with the wrong
mail adres. Ill send my last two posts again :
On Tue, 12 Apr 2005, David Hopwood wrote:
> # A second type of role based systems does involve some state. In this
> # type of system a user can assume a role from its profile, only one role
> # at a time.
> In a capability system, when an object (= subject) makes a request, it
> must present all of the capabilities needed for that request. An object
> can, if its programmer wants, partition the capabilities it holds into
> sets that are equivalent to roles, thus simulating a role-based system.
> In fact this simulates a more expressive role-based system in which an
> object can assume more than one role for a given request.
> However, being required by the system design to partition capabilities
> into role-sets chosen in advance is quite limiting (unless the sets
> each contain a single capability and objects can assume more than one
> role-set; in that case it is not limiting, but is pointlessly complex).
The main goal of the system I am working on is creating an authorization
system with hooks for an incident response system. The incident response
system will to a great extend initiate role changes, for example changing
the role of a 'server', based on the fact that the server software is
determined to be either 'fully-patched', 'vulnerable', or 'compromized'.
Likewise a user or a file or any other type of stateful object, could
based on incidents be asigned an other role by the IDS.
If I understand correctly what you mean by limiting, I believe this
form of limiting might be the core requirement for being able to
create the required hooks for incident response. 'role' might not be the
right semantics, but I definetly need the capabilities to only be
usable within such constraints with respect to IDS issued state of the
objects. I hope this makes some sense.
> There is no evidence to suggest that it would help. To achieve POLA the
> programmer should just pass whatever individual capabilities are needed.
> So in a capability system it is entirely unnecessary to have roles as a
> base concept.
Given the importance of the IDS imposed state on objects, what
alternatives would there be to still implement the strict dependance on
these without resorting to roles?
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