Re: [Ace] Key IDs ... RE: WGLC on draft-ietf-ace-cwt-proof-of-possession-02

Jim Schaad <ietf@augustcellars.com> Sat, 23 June 2018 16:05 UTC

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From: Jim Schaad <ietf@augustcellars.com>
To: 'Mike Jones' <Michael.Jones@microsoft.com>, 'Hannes Tschofenig' <Hannes.Tschofenig@arm.com>, <draft-ietf-ace-cwt-proof-of-possession@ietf.org>
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Date: Sat, 23 Jun 2018 18:05:27 +0200
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Subject: Re: [Ace] Key IDs ... RE: WGLC on draft-ietf-ace-cwt-proof-of-possession-02
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No not really, Hannes's language is much closer to what I am looking for.  I
don't care if they are different kinds of CWTs.  I care about impersonation.

> -----Original Message-----
> From: Mike Jones <Michael.Jones@microsoft.com>;
> Sent: Friday, June 22, 2018 10:44 PM
> To: Jim Schaad <ietf@augustcellars.com>;; Hannes Tschofenig
> <Hannes.Tschofenig@arm.com>;; draft-ietf-ace-cwt-proof-of-
> possession@ietf.org
> Cc: ace@ietf.org
> Subject: RE: Key IDs ... RE: [Ace] WGLC on draft-ietf-ace-cwt-proof-of-
> possession-02
> 
> I think you're looking for language something along these lines, right
Jim?
> 
> "Likewise, if PoP keys are used for multiple different kinds of CWTs in an
> application and the PoP keys are identified by Key IDs, care must be taken
to
> keep the keys for the different kinds of CWTs segregated so that an
attacker
> cannot cause the wrong PoP key to be used by using a valid Key ID for the
> wrong kind of CWT."
> 
> 				-- Mike
> 
> -----Original Message-----
> From: Jim Schaad <ietf@augustcellars.com>;
> Sent: Friday, June 22, 2018 7:59 AM
> To: Hannes Tschofenig <Hannes.Tschofenig@arm.com>;; Mike Jones
> <Michael.Jones@microsoft.com>;; draft-ietf-ace-cwt-proof-of-
> possession@ietf.org
> Cc: ace@ietf.org
> Subject: RE: Key IDs ... RE: [Ace] WGLC on draft-ietf-ace-cwt-proof-of-
> possession-02
> 
> That language works if you assume that there is only one CWT that an RS
will
> look to.  If there are multiple CWTs then one needs coordination language
> between them.
> 
> > -----Original Message-----
> > From: Hannes Tschofenig <Hannes.Tschofenig@arm.com>;
> > Sent: Friday, June 22, 2018 6:36 AM
> > To: Jim Schaad <ietf@augustcellars.com>;; 'Mike Jones'
> > <Michael.Jones@microsoft.com>;; draft-ietf-ace-cwt-proof-of-
> > possession@ietf.org
> > Cc: ace@ietf.org
> > Subject: Key IDs ... RE: [Ace] WGLC on draft-ietf-ace-cwt-proof-of-
> > possession-02
> >
> > Hi Jim,
> >
> > I would like to comment on this issue.
> >
> > -----
> > > > 14.  I have real problems w/ the use of a KID for POP
> > > > identification.  It
> > may
> > > identify the wrong key or, if used for granting access, may have
> > > problems
> > w/
> > > identity collisions.  These need to be spelt out someplace to help
> > > people tracking down questions of why can't I verify w/ this CWT, I
> > > know it's
> > right.
> > >
> > > The Key ID is a hint to help identify which PoP key to use.  Yes, if
> > > a Key
> > ID is
> > > sent that doesn't correspond to the right PoP key, failures may occur.
> > > I
> > view
> > > that as usage bug - not a protocol problem.  If keys aren't
> > > consistently
> > known
> > > and identified by both parties, there are lots of things that can go
> > wrong, and
> > > this is only one such instance.  That said, I can try to say
> > > something
> > about the
> > > need for keys to be consistently and known by both parties, if you
> > > think
> > that
> > > would help.
> >
> > > My problem is that if there are two different people with the same
> > > Key ID,
> > either intentionally or unintentionally, then using the key ID to
> > identify
> the
> > key may allow the other person to masquerade as the first person.  I
> > am unworried about the instance of a failure to get a key based on a key
id.
> > That is not the problem you are proposing to address.
> >
> > -----
> >
> > I think we should document this issue. Here is some text proposal that
> could
> > go into a separate operational consideration section (or into the
> > security consideration section instead).
> >
> > "
> > - Operational Considerations
> >
> > The use of CWTs with proof-of-possession keys requires additional
> > information to be shared between the involved parties in order to
> > ensure correct processing. The recipient needs to be able to use
> > credentials to
> verify
> > the authenticity, integrity and potentially the confidentiality of the
> > CWT
> and
> > its content. This requires the recipient to know information about the
> issuer.
> > Like-wise there needs to be an upfront agreement between the issuer
> > and the recipient about the claims that need to be present and what
> > degree of trust can be put into those.
> >
> > When an issuer creates a CWT containing a key id claim, it needs to
> > make sure that it does not issue another CWT containing the same key
> > id with a different content, or for a different subject, within the
> > lifetime of the
> CWTs,
> > unless intentionally desired. Failure to do so may allow one party to
> > impersonate another party with the potential to gain additional
> privileges.
> > "
> >
> >
> > Ciao
> > Hannes
> >
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