Re: [Anima-bootstrap] brsky concern1: separating audit-log retrieval from voucher generation

Toerless Eckert <tte@cs.fau.de> Wed, 02 November 2016 01:35 UTC

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Date: Wed, 2 Nov 2016 02:35:44 +0100
From: Toerless Eckert <tte@cs.fau.de>
To: "Max Pritikin (pritikin)" <pritikin@cisco.com>
Message-ID: <20161102013544.GB4057@faui40p.informatik.uni-erlangen.de>
References: <20161101201523.GB9776@faui40p.informatik.uni-erlangen.de> <C825BB00-9DEF-4293-8ACB-A453F4C896A6@cisco.com>
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Cc: Toerless Eckert <tte+ietf@cs.fau.de>, "anima-bootstrap@ietf.org" <anima-bootstrap@ietf.org>
Subject: Re: [Anima-bootstrap] brsky concern1: separating audit-log retrieval from voucher generation
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On Tue, Nov 01, 2016 at 10:16:45PM +0000, Max Pritikin (pritikin) wrote:
> I see this as the same discussion for ???concern2??? so please look to that thread for responses.

I can not identify any text n the sections 6.4 and 7 (that you referred
to in the other mail reply) that are discusing the case i made below.

Cheers
    Toerless


> - max
> 
> > On Nov 1, 2016, at 2:15 PM, Toerless Eckert <tte+ietf@cs.fau.de> wrote:
> > 
> > As discussed today on the call, restated for the rest of the team with more detail:
> > 
> > -> pledge connects to two networks, A, B.
> > -> Pledge tries to well-behave, only offers nonce to one network first, A.
> > -> (registrar of) A gets voucher. A looks at audit-log. Audit log is fine.
> >   Ultimately, A decides  not to enroll pledge though.
> > -> Pledge offers nonce to B, B gets voucher and audit-log.
> >   Audit log shows A, so B is concerned. B rejects device.
> >   Without the entry in audit log, B would have enrolled device.
> > 
> > My worry is that the current audit log approach can too easily create
> > false positives that will make enrolment fail if a device has multiple network
> > connections:
> > 
> > It's impossible for A to get an audit-log without also getting
> > a voucher, which in return would make another domain suspicious and likely
> > make it decide not to accept the device.
> > 
> > Separating out request for voucher from request for audit-log could work like this:
> > 
> >  A->MASA: request audit-log for (pledge,nonce1)
> >  MASA:    audit-log entry: "A requested audit log for pledge, hash(nonce1)" [1]
> >  MASA->A: reply: audit-log
> > 
> >  ... A makes up its mind if it wants pledge and decides that it does NOT.
> > 
> >  -> A doesn't do anything more. Audit log would show B that A did see device,
> >     but also that A never got voucher so that it could not have modified
> >     device == B will happily enroll pledge.
> > 
> > 
> >  ... A makes up its mind if it wants pledge and decides that it does want to:
> > 
> >  A->MASA: request voucher for (pledge,nonce1)
> >  MASA:    Examine audit-log that no voucher was granted since the audit-log
> >           was given to A [1]. requests for audit-logs since [1] are
> > 	   ignored in this determination.
> >  MASA->A: If audit-log ok:
> >           reply OK: voucher(nonce1)
> >           audit-log entry: "A received voucher for pledge, hash(nonce1)" [2]
> > 
> > 	   If audit-log nok:
> >           reply NOK: audit-log
> >           audit-log entry: "A failed voucher request for pledge, hash(nonce1), hash(nonce2)"
> > 	   hash(nonce2) would be from an audit-log entry that did happen after
> > 	   [1] and 
> > 
> > 
> > Cheers
> >    Toerless
> > 
> > _______________________________________________
> > Anima-bootstrap mailing list
> > Anima-bootstrap@ietf.org
> > https://www.ietf.org/mailman/listinfo/anima-bootstrap
> 

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tte@cs.fau.de