[DGD] capability based security?

Wed Mar 23 16:49:06 CET 2016

Actually based on the general literature I have always viewed subjects as
any entity about which one wants to know whether it can be granted access
or not to a given x via a security matrix lookup. This is kind of what I
meant by the definition. I.e. it could be a set of almost anything that you
want to make this query about.

I think for the papers in the areas of capabilities and permissions there
tend to be very few actual serious proofs in the papers I've encounter.
They mainly describe the implementation details of the specific realisation
of the basic principles.

As this paper mentions-

http://citeseerx.ist.psu.edu/viewdoc/download?doi=10.1.1.112.8296&rep=rep1&type=pdf

<http://citeseerx.ist.psu.edu/viewdoc/download?doi=10.1.1.112.8296&rep=rep1&type=pdf>

The problem of administration is a fundamental problem with practical
capability systems- I am not sure how practical they really are since they
don't have much of a great presence outside the research setting. The
burden placed on a mud admin might be quite great given that many of the
ones I have known aren't necessarily that technically inclined.

Regards,

Silenus.

<http://citeseerx.ist.psu.edu/viewdoc/download?doi=10.1.1.112.8296&rep=rep1&type=pdf>

On Wed, Mar 23, 2016 at 6:16 PM, <bart at wotf.org> wrote:

> Well, Shentino is trying to build a
> practical system, and I am looking at actual
> implementations that have seen use in the
> real world outside a pure research env.
>
> The definition of subject is highly relevant
> for proving the security of a system, even
> more so within the context of an lpc
> environment which has no concept of process,
> but in case of dgd can offer persistent
> subjects which are not based on a principal.
>
> Because the things you can prove about a
> capability based system strongly depend on
> how you define those subjects, its certainly
> much more then the implementation choice you
> suggest.
>
> This is also documented in various papers
> and for example one of the fundamental
> considerations behind eros.
>
> Bart
>
> On Wed, 23 Mar 2016 17:01:39 +0800, Carter
> Cheng wrote
> > I actually was just quoting a textbook
> description by I believe Tanenbaum.
> > I suspect that what is defined as a
> subject is an issue of implementation
> > rather than theory. Whether the subject is
> a process itself or an
> > individual user is mainly a matter of
> definition from a theoretical
> > perspective since the matrix is
> fundamental to descriptions of security
> > even in the research literature. From this
> perspective the smallest element
> > typically is similar to what raymond is
> describing which is kind of the
> > associate action that can be taken S x R x
> A matrix. In the case of the
> > implementation of the security matrix I
> sort of agree. However if
> > you look at some capability based research
> systems a fundamental
> > element most such systems is transfer of
> the socalled key.
> > Revocation is known to be problematic in
> capability based systems
> > but not impossible. For many
> implementations it is however quite
> > difficult given how the key is
> represented.
> >
> > >From a more practical standpoint the
> number of such elements is quite
> > large. So the data denoting the various
> "keys" can be difficult to manage.
> > I think from a practical standpoint in a
> dgd based system one has to
> > decide
> > (practical issue) what the subjects are
> and how to cope with revocation
> > under transfer. My sense is ideally it
> should be closed under a kind
> > of transfer operator in a transitive
> manner i.e. if A gives a copy
> > of a key to B and B then gives a copy of
> the key transferred in this
> > manner to C. If A subsequently revokes B's
> key C should be revoked
> > as well unless it was transferred to C by
> some other source as well.
> > This kind of management might require
> somewhat complex book keeping
> > however and also might have unforeseen
> consequences when one isn't
> > exactly sure of the history of transfers
> when doing a revocation.
> >
> > There are probably a number of research
> papers describing research systems
> > out there that one could look at for some
> examples.
> >
> > Regards,
> >
> > Silenus.
> >
> > On Fri, Mar 18, 2016 at 6:13 PM,
> <bart at wotf.org> wrote:
> >
> > > In a more general sense, capabilities
> are a way to grant a privilege to a
> > > subject, which does not depend on
> listing all allowed subjects on the
> > > target,
> > > but rather on giving the subject some
> kind of token that can be verified by
> > > the target.
> > >
> > > It assumes this token cannot be forged
> and can be verified reliably. Being
> > > able to transfer a capability is often
> but not always part of this.
> > >
> > > An important distinction between
> permission based systems and capability
> > > based
> > > systems is a permission based system
> requiring a subject for a privilege
> > > to be
> > > linked to a principal (user), whereas a
> capability system does not, a
> > > subject
> > > can be a single process, or program, or
> object, without any relation to a
> > > specific user. Due to this, the approach
> that capabilities and permissions
> > > are
> > > just 2 different ways to slice up the
> security matrix is at least
> > > incomplete,
> > > and in many cases incorrect. A
> permission based system has subjects based
> > > on
> > > principals on one axis, whereas a
> capability based system shouldn't,
> > > rather,
> > > it should have subjects based on the
> smallest entity in the system which
> > > can
> > > still use a privilege (usually a
> process, but this could be a single
> > > program,
> > > or part of a program, ie, a single
> function)
> > >
> > > Bart.
> > >
> > > On Thu, 17 Mar 2016 17:06:00 -0700,
> Raymond Jennings wrote
> > > > I think capabilities are this:
> > > >
> > > > Subject X (a user, or a process
> associated with a user) can possess a
> > > > capability Y (read, write, execute, or
> other such access) for object
> > > > Z (a file, a user, a process).
> > > >
> > > > A privileged process W creates the
> capability Y and gives it to
> > > > subject X once X proves it has
> authorization (presenting a password,
> > > > authenticating, or even in some cases
> picking up another capability),
> > > >  and then X can freely use capability
> Y without further
> > > > administrivia or authentication, or
> more importantly, X can pass
> > > > capability Y to any other agent Q, and
> Q can use that capability on
> > > > behalf of X.
> > > >
> > > > Of course, we are trusting that X
> protects capability Y and only
> > > > hands it out to other agents Q that it
> trusts.
> > > >
> > > > A further assumption may be that the
> capability may be arbitrarily
> > > revoked
> > > > or suppressed at any moment by a
> privileged process of some sort.
> > > >
> > > > On Thu, Mar 17, 2016 at 1:00 PM,
> Carter Cheng
> > > > <cartercheng at gmail.com> wrote:
> > > >
> > > > > I had looked into capabillity based
> security some years ago and
> > > partially
> > > > > implemented a system for doing them
> for a modified version of the dead
> > > > > souls library in fluffos. I never
> quite finished it since I was
> > > somewhat
> > > > > uncertain how to mitigate the
> complexity of transmitting capabilities
> > > and
> > > > > modifying the capability during such
> transmission to limit the
> > > permissions
> > > > > an object had. My limited
> understanding of the capabilties versus
> > > > > permissions approach is both
> represent different ways of cutting up the
> > > > > security matrix (one vertically and
> one horizontally). I am not sure
> > > what
> > > > > you are quite meaning by a
> capability. My understanding is that in most
> > > > > systems that are in research these
> are some sort of string denoting the
> > > > > horizontal or vertical slice of the
> matrix and that transmission
> > > involves
> > > > > copying a portion of this string
> into a new object. The problem I think
> > > > > would be in designing a simple
> approach for copying a "portion" of the
> > > > > string and specifying which portion
> in order that less technically
> > > savvy
> > > > > users (which includes a lot of mud
> adminstrators and coders) would know
> > > > > what to do when asked to supply a
> substring of the original string.
> > > > > I guess I don't mud that much
> nowadays so I haven't tried finishing my
> > > > > implementation but that was the main
> problem I was running into.
> > > > >
> > > > > Regards,
> > > > >
> > > > > Silenus.
> > > > >
> > > > > On Thu, Mar 17, 2016 at 1:01 AM,
> <bart at wotf.org> wrote:
> > > > >
> > > > > > A few comments on this:
> > > > > > - you can't protect against
> stupidity but
> > > > > > for any security system a fail-
> safe approach
> > > > > > should be used, put differently,
> doing
> > > > > > dangerous things should take
> enough work to
> > > > > > not just happen by accident. The
> very large
> > > > > > majority of security issues are a
> result of
> > > > > > this not being done properly by
> many
> > > > > > security systems.
> > > > > >
> > > > > > - doing all security checks in the
> wiztool,
> > > > > > I'd rather think a security check
> should be
> > > > > > done as close to the resource
> needing
> > > > > > protection to ensure as few ways
> to bypass
> > > > > > those checks as possible.
> > > > > >
> > > > > > - having the object to which a
> capability is
> > > > > > given registered on the 'badge'
> and hence
> > > > > > requiring a formal interface to
> pass on a
> > > > > > capability seems akin to putting a
> name and
> > > > > > picture (and nowadays biometric
> info) on a
> > > > > > badge, and seems a really good
> idea if the
> > > > > > purpose is to verify the holder of
> the
> > > > > > badge.
> > > > > >
> > > > > > This can be done with a kernel
> service but
> > > > > > if the data is centralized this
> has a
> > > > > > potential of not playing well with
> hydra.
> > > > > >
> > > > > > Bart
> > > > > >
> > > > > > On Wed, 16 Mar 2016 01:08:39
> -0500, Jared
> > > > > > Maddox wrote
> > > > > > > > Date: Wed, 9 Mar 2016 12:29:43
> -0800
> > > > > > > > From: Raymond Jennings
> > > > > > <shentino at gmail.com>
> > > > > > > > To: All about DGD and Hydra
> > > > > > <dgd at dworkin.nl>
> > > > > > > > Subject: Re: [DGD] capability
> based
> > > > > > security?
> > > > > > > > Message-ID:
> > > > > > > >
> > > > > > <CAGDaZ_r3VdEPv=bh6cP+eHLbWpG2z7-
> > > > > >
> tTZNC1S8krKZj5VJq0A at mail.gmail.com>
> > > > > > > > Content-Type: text/plain;
> charset=UTF-8
> > > > > > > >
> > > > > > > > I figured that the
> construction,
> > > > > > configuration, and destruction of
> > > > > > > > capabilities and their handles
> would be
> > > > > > the perview of trusted code (like
> a
> > > > > > > > microkernel) and then its at
> the
> > > > > > discretion of the code taking the
> caps on
> > > > > > > > what they do with the actual
> > > > > > handles...and that if they screw
> it up its
> > > > > > > > their own fault.
> > > > > > > >
> > > > > > > > Is it valid to say "I
> guarantee the
> > > > > > security that nobody will be able
> to
> > > > > > > > use this capability unless you
> let them,
> > > > > > but if you give it away you're on
> > > > > > > > your own"?
> > > > > > > >
> > > > > > >
> > > > > > > "I guarantee security against
> all but your
> > > > > > own stupidity"? I think
> > > > > > > that sort of thing works it's
> way into
> > > > > > most user agreements.
> > > > > > >
> > > > > > > > Date: Wed, 9 Mar 2016 22:31:13
> +0100
> > > > > > > > From: bart at wotf.org
> > > > > > > > To: All about DGD and Hydra
> > > > > > <dgd at dworkin.nl>
> > > > > > > > Subject: Re: [DGD] capability
> based
> > > > > > security?
> > > > > > > > Message-ID:
> > > > > >
> <20160309210855.M49546 at bartsplace.net>
> > > > > > > > Content-Type: text/plain;
> > > > > > charset=utf-8
> > > > > > > >
> > > > > > > > It depends. If something wants
> to check
> > > > > > if your object has a certain
> > > > > > > > capability, and you present it
> your
> > > > > > badge, itstrivial for the code
> checking it
> > > > > > > > to clone it and reuse it,
> unless you
> > > > > > actively prevent that. What I
> mentioned
> > > > > > > > may be a way, registering in
> the handle
> > > > > > which object it was given to.
> > > > > > > >
> > > > > > >
> > > > > > > This could be tended to with a
> kernel
> > > > > > service instead.
> > > > > > >
> > > > > > > Beyond that, if most or all code
> can
> > > > > > create capability objects to
> > > > > > > represent whatever capabilities
> it has,
> > > > > > then objects can use it to
> > > > > > > implement security layers.
> > > > > > >
> > > > > > > > Date: Wed, 9 Mar 2016 17:05:56
> -0800
> > > > > > > > From: Raymond Jennings
> > > > > > <shentino at gmail.com>
> > > > > > > > To: All about DGD and Hydra
> > > > > > <dgd at dworkin.nl>
> > > > > > > > Subject: Re: [DGD] capability
> based
> > > > > > security?
> > > > > > > > Message-ID:
> > > > > > > >
> <CAGDaZ_p3OHFkUMJgs2DSx-
> > > > > > 4YgctFJ5Lf-c5a+3-da-
> F6qDPvnw at mail.gmail.com>
> > > > > > > > Content-Type: text/plain;
> charset=UTF-8
> > > > > > > >
> > > > > > > > ooh...good point
> > > > > > > >
> > > > > > > > capabilities will probably
> need their
> > > > > > own ACLs that can be manipulated
> by
> > > > > > > > the objects thereon.
> > > > > > > >
> > > > > > >
> > > > > > > I think capabilities should
> ideally be
> > > > > > carried around inside wiztools
> > > > > > > & such: if a security check
> needs to be
> > > > > > done, the wiztool can do it
> > > > > > > transparently.
> > > > > > >
> > > > > > > If arbitrary pieces of code can
> create the
> > > > > > wiztools, then they can
> > > > > > > also strengthen the security of
> the
> > > > > > wiztool.
> > > > > > >
> > > > > >
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