Re: [lamps] Seeking guidance on proceeding with question from IETF-104 presentation on lightweight CMP profile

"Fries, Steffen" <> Wed, 03 April 2019 16:12 UTC

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From: "Fries, Steffen" <>
To: Jim Schaad <>, "" <>
Thread-Topic: [lamps] Seeking guidance on proceeding with question from IETF-104 presentation on lightweight CMP profile
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Date: Wed, 3 Apr 2019 16:11:48 +0000
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Subject: Re: [lamps] Seeking guidance on proceeding with question from IETF-104 presentation on lightweight CMP profile
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Hi Jim, 
> This is a quick walk through what you have below.  It would have been helpful to have pointers to the sections/bullet points where
> things are meant to be modified.
First of all, thank you for the walk through. I made some comments to your questions. 

> > Hi,
> >
> > during the LAMPS session in IETF-104 we presented a draft for a
> lightweight
> > industrial CMP profile. The document as such bases on CMP and targets
> > to simplify the very versatile CMP.
> >
> > During the presentation we have been asked to also talk to the ACE WG
> chair
> > regarding potential interest in this work, as it was not sure if LAMPS
> > is
> the
> > right home. I talked to Jim Schaad and as we only work on CMP
> > directly,
> not
> > with the transport nor specific considerations for constraint devices,
> > ACE
> may
> > not be the right home. Also, Jim was asking if the draft needs to be a
> > standards track RFC and thus be adopted in a WG. An alternative
> > approach could also be an independent submission. To make this
> > decision, we need some guidance.
> >
> > For this, let me enumerate the main points we addressed in the draft:
> > - Generally Section 1.4 enlists the exceptions from the mandatory CMP
> > Profile as defined in RFC4210 Appendix D:
> >  o  signature-based protection is the default protection; initial
> transactions may also use HMAC,
> Depending on what is being proven this is reasonable.  I would consider this to be profiling
> > o  certification of a second key pair within the same transaction is
> > not
> supported,
> I would consider this to be profiling
> > o  proof-of-possession (POPO) with self-signature of the certTemplate
> according to [RFC4211] section 4.1 clause 3 is the only supported POPO method,
> I would consider this to be profiling
> > o  confirmation of newly enrolled certificates may be omitted, and
> especially
> I would consider this to be profiling
> > o  all transactions consist of request-response message pairs
> > originating
> at the end entity (EE), i.e.,  announcement messages are omitted.
> I would consider this to be profiling
> > - In section 4.1.5 the proceeding of central key generation needed
> > extensions at least for ECC key pairs.
> Not sure what you think falls here and the document is not forth coming.
> This may have already been done.
Our understanding was that the current approach in RFC 4210 requires at least some support for RSA even if the generated key pair is ECDSA. This is due to the statement for encrypting the private key when sending the generated material back to the client. Here, the encryption key is to be encrypted with a short term asymmetric key of the client. 

> > - In section 4.4.1 the RootCAUpdate is specified as request-response
> > transaction and differs from the announcement message as specified in
> > RFC4210 section 4.4 and Appendix E.
> Depending on how this is done, it will require an update of RFC 4211.  I believe that this means it must be an IETF consensus document
> and may need to be standards track.
The intention here was to avoid the announce messages for the RootCA update completely to better support application in constraint devices, which may be temporarily offline or my not feature a server part listening for announce messages. Using a request response allows the client to simply ask for an update. 
Why do you think this will influence also RFC 4211?

> > - In section 5 the new Extended Key Usages id-kp-cmpRA is introduced
> > to indicate that a key pair is entitled to be used by an LRA/RA for
> signature-
> > based protection of a CMP message.
> This can be considered to be a profile.
> > - Generally further topics to clarify CMP or CRMF may come up during
> > WG review.
> >
> > Based on this list, are these point to be handled as profiling of the
> > base protocol or are they rather seen as technical change/enhancement?
> > My understanding is that for profiling an independent RFC would be
> > fine,
> as
> > the base spec can be normatively referenced by other standards. In
> > this
> case
> > the CMP profile document can be informational.
> > If some of the points listed qualify rather for technical changes of
> > the
> base
> > protocol, my understanding is that we need to find a home for the
> > draft
> and
> > target the standard track. @Jim, I hope my conclusion based on our
> > conversation is right.
> >
> > Regarding interest in the resulting RFC there is work ongoing in ANIMA
> > WG and EAP WG, that can directly leverage the lightweight CMP.
> Have either of these groups expressed any active interest in this work?
> This is not something that EAP would normally be looking at as far as I know as they normally consider the act of setting up the EAP
> credentials to be a "Not My Problem" space.
Both groups are not active regarding CMP adaptation to my knowledge. But there are documents discussed (currently individual submissions and not WG items), which can leverage a lightweight CMP without the need of specifying something by their own. 
In EAP draft-pala-eap-creds targets enrollment over EAP and specifically addresses CMP. We also talked to Max (the author) and he is interested in utilizing a lightweight CMP for this. 
In ANIMA, we proposed BRSKI-AE to allow for enrollment in domains, which are not always online or which do not feature an on-site PKI. Here, self-contained objects are necessary to bind the initial authentication of an enrolling device to the certification request directly, instead of binding it to the underlying transport protocol. CMP would be applicable as one option for providing such a self-contained object. 

Best regards

> Jim
> >
> > In either case your view is appreciated.
> >
> > Best regards
> > Steffen
> >
> > _______________________________________________
> > Spasm mailing list
> >
> >