TPM-based Network Device Remote Integrity Verification
draft-ietf-rats-tpm-based-network-device-attest-14

[Ballot comment]
Thanks for addressing my previous Discuss point and the preponderance of
my previous Comments!  I retain a couple here, as I think they still
apply to some extent.

Section 1.5

  3.  Conveyance of Evidence reliably transports the collected Evidence
      from Attester to a Verifier to allow a management station to
      perform a meaningful appraisal in Step 4.  The transport is
      typically carried out via a management network.  The channel must
      provide integrity and authenticity, and, in some use cases, may
      also require confidentiality.

It seems like there is some subtlety here if we insist that the
communications channel to a potentially untrustworthy endpoint will
provide integrity and authenticity (let alone confidentiality).  I suggest
giving more clarity on what threats these technical measures are
protecting against in relation to the potentially untrusted endpoint.
[ed. I do see the added text to indicate that the TPM signing key
does provide a separate signature over the critical evidence, but
that does not explain why we still say we want integrity and authentication
(and in some cases confidentiality) of the channel that conveys such evidence.]
Section 3.3

  In this application, each device may need to be equipped with signed
  RIMs to act as an Attester, and also an Appraisal Policy for Evidence
  and a selection of trusted X.509 root certificates, to allow the
  device to act as a Verifier.  An existing link layer protocol such as
  802.1X [IEEE-802.1X] or 802.1AE [IEEE-802.1AE], with Evidence being
  enclosed over a variant of EAP [RFC3748] or LLDP [LLDP] are suitable
  methods for such an exchange.

Should we say that the details of those "variant"s being out of scope for
this document?  (What we do say is pretty far from a complete solution.)

[Ballot comment]
Thanks for working on this specification.

This was good read. (I was dishearten to find ,my interest, "virtualization and containerization" was out of scope :-()

Supporting Benjamin Kaduk's discuss.

[Ballot comment]
Agree with Ben's DISCUSS. This Informational document seems to want to
normatively talk about and reference quite a few other documents. However,
that's not really something an Informational document can really (normatively)
do.

Found terminology that should be reviewed for inclusivity; see
https://www.rfc-editor.org/part2/#inclusive_language for background and more
guidance:

* Term "native"; alternatives might be "built-in", "fundamental",
  "ingrained", "intrinsic", "original" (matched "native" rule, pattern
  ((\bnative\w*\b)\w*)).

Thanks to Linda Dunbar for their General Area Review Team (Gen-ART) review
(https://mailarchive.ietf.org/arch/msg/gen-art/uJfSJiH2jjpTrxAlux60VNEDF-0).

-------------------------------------------------------------------------------
All comments below are about very minor potential issues that you may choose to
address in some way - or ignore - as you see fit. Some were flagged by
automated tools (via https://github.com/larseggert/ietf-reviewtool), so there
will likely be some false positives. There is no need to let me know what you
did with these suggestions.

Section 1.5. , paragraph 7, nit:
> station Result, used to inform decision making. In practice, this means comp
>                                ^^^^^^^^^^^^^^^
The noun "decision-making" (= the process of deciding something) is spelled
with a hyphen.

Section 1.5. , paragraph 8, nit:
> ation expected by the Verifier. Subsequently the Appraisal Policy for Evidenc
>                                ^^^^^^^^^^^^
A comma may be missing after the conjunctive/linking adverb "Subsequently".

Section 1.6. , paragraph 3, nit:
>  attestation of Linux or other multi-threaded operating system processes aft
>                                ^^^^^^^^^^^^^^
This word is normally spelled as one.

Section 2.1.1. , paragraph 8, nit:
> ader | 8 | 9 | | (e.g GRUB2 for Linux) |
>                  ^^^
The abbreviation "e.g." (= for example) requires two periods.

Section 2.3. , paragraph 16, nit:
> arly system startup (e.g., BIOS, boot loader, OS kernel) are essentially sing
>                                  ^^^^^^^^^^^
This word is normally spelled as one.

Section 2.4.1. , paragraph 5, nit:
> d in [I-D.ietf-rats-architecture]. However additional prerequisites have been
>                                    ^^^^^^^
A comma may be missing after the conjunctive/linking adverb "However".

Section 4. , paragraph 10, nit:
>  redundant information, or add an additional layer of signing using external
>                            ^^^^^^^^^^^^^^^^^^^^^^^
This phrase might be redundant. Consider either removing or replacing the
adjective "additional".

Document references draft-ietf-rats-yang-tpm-charra-12, but -13 is the latest
available revision.

Document references draft-birkholz-rats-reference-interaction-model-03, but -05
is the latest available revision.

These URLs in the document can probably be converted to HTTPS:
* http://www.uefi.org

[Ballot discuss]
Something of a process question, but in §2.3 we refer to
[Canonical-Event-Log] in a normative manner ("MUST be formatted according
to ..."), but the referenced document is marked as "draft" and "work in
progress", with warning that "Readers should not design products based
on this document".  Are we planning to hold publication of this document
until the TCG dependency is finalized?

[Ballot comment]
There are quite a few requirements that are stated in multiple locations
in this document, using normative language in the multiple locations.
This can lead to confusion and ambiguity if the different statements are
found to be subtly different, and I would recommend making a normative
statement of each requirement exactly once, with other instances merely
mentioning as a statement of fact that the behavior in question is
required.  I note some (but presumably not all) instances in the
section-by-section remarks as they occur.

Other than that, it's generally well-written and was quite easy to follow.
Thanks!  (That, of course, could not possibly keep me from having further
comments to make, though...)

Section 1.5

  3.  Conveyance of Evidence reliably transports the collected Evidence
      from Attester to a Verifier to allow a management station to
      perform a meaningful appraisal in Step 4.  The transport is
      typically carried out via a management network.  The channel must
      provide integrity and authenticity, and, in some use cases, may
      also require confidentiality.

It seems like there is some subtlety here if we insist that the
communications channel to a potentially untrustworthy endpoint will
provide integrity and authenticity (let alone confidentiality).  I suggest
giving more clarity on what threats these technical measures are
protecting against in relation to the potentially untrusted endpoint.

Section 2.1

  The result is that the Verifier can verify the device's identity by
  checking the subject attribute of the distinguished name and
  signature of the certificate containing the TPM's attestation public

Please just refer to the Subject [RFC5280] of the certificate; per
draft-ietf-uta-rfc6125bis the subjectAltName (not the DN) is the preferred
representation for this information.

  *  Credentials - Administrators may wish to verify via attestation
      that public keys (and other credentials) outside the Root of Trust
      have not been subject to unauthorized tampering.  (By definition,

It's a bit surprising to see public keys referred to as Credentials; while
a private key or a signed certificate might be deemed a credential, a
public key devoid of other context seems to just be a public key.  Unless
the intent was to refer to public keys that are entries in a trust store,
in which they might be said to be credentials of the trusted entities that
hold the corresponding private keys?

Section 2.2

  *  When separate Identity and Attestation keys are used, the
      Attestation Key (AK) and its X.509 certificate should parallel the
      DevID, with the same device ID information as the DevID
      certificate (that is, the same subject and subjectAltName (if
      present), even though the key pairs are different).  This allows a
      quote from the device, signed by an AK, to be linked directly to
      the device that provided it, by examining the corresponding AK
      certificate.  [...]

This seems to also implicitly assume that the issuer of these certificates
does not issue any other credentials using the same subject information.
When the device serial number is included, this seems pretty reliable, but
in other cases the situation is less clear.

Section 2.3

  5.  Quotes MUST be retrieved from the TPM according to TCG TAP
      Information Model [TAP] and the CHARRA YANG model
      [I-D.ietf-rats-yang-tpm-charra].  While the TAP IM gives a
      [...]
      the signature, to preserve the trust model.  The
      [I-D.ietf-rats-yang-tpm-charra] can be used for this purpose.

If we're going to MUST-level require something, then "can be used for this
purpose" seems inaccurate -- wouldn't "is used" be better?

Section 2.4

  *  The product to be attested MUST be shipped by the equipment vendor
      with both an IEEE 802.1AR Device Identity and an Initial
      Attestation Key (IAK) with certificate in place.  The IAK

I feel like this is maybe the third time we've had "MUST ship with IDevID
and IAK"; once is probably enough, and would avoid any confusion if the
different locations in the text are subsequently found to be subtly
different.
(A couple of the other requirements in this section are, I think,
duplicates for the second time.)

Section 2.4.2

  Quotes from a TPM can provide evidence of the state of a device up to
  the time the evidence was recorded, but to make sense of the quote in
  most cases an event log that identifies which software modules
  contributed which values to the quote during startup MUST also be
  provided.  [...]

The "in most cases" seems to be a heavy qualifier on the "MUST".  How do I
know when the "MUST" does not apply?  (Or does it always apply, and there
are just rare instances where it is not actually needed for Verifier
operation?)

Section 3.1.1

  A secure Device Identity (DevID) in the form of an IEEE 802.1AR DevID
  certificate [IEEE-802-1AR] MUST be provisioned in the Attester's
  TPMs.

(Fourth time as a "MUST"?)

Section 3.2.1

  Network Management systems MUST retrieve signed PCR based Evidence
  using [I-D.ietf-rats-yang-tpm-charra] with NETCONF or RESTCONF.

We had a MUST-level requirement up in §3.2 for "accomplished via an
interface that implements the YANG Data Model for [tpm-charra]", but this
one also requires (NETCONF or RESTCONF), excluding potential future
developments such as CORECONF.  This is exactly the sort of skew between
restatements of a single requirement that has been problematic in other
documents, as I alluded to previously.

  Implementations that use NETCONF MUST do so over a TLS or SSH secure
  tunnel.  Implementations that use RESTCONF transport MUST do so over
  a TLS or SSH secure tunnel.

This is not a requirement I've seen before.  Everything else typically
just uses the YANG security considerations boilerplate that notes that the
mandatory (to implement) secure transport for RESTCONF is TLS and the
mandatory secure transport for NETCONF is SSH.  I don't even know that you
*can* use SSH for RESTCONF (NETCONF seems pretty clear that TLS is okay).

Section 3.3

  In this application, each device may need to be equipped with signed
  RIMs to act as an Attester, and also an Appraisal Policy for Evidence
  and a selection of trusted X.509 root certificates, to allow the
  device to act as a Verifier.  An existing link layer protocol such as
  802.1X [IEEE-802.1X] or 802.1AE [IEEE-802.1AE], with Evidence being
  enclosed over a variant of EAP [RFC3748] or LLDP [LLDP] are suitable
  methods for such an exchange.

Should we say that the details of those "variant"s being out of scope for
this document?  (What we do say is pretty far from a complete solution.)

Section 5

Do we want to incorporate by reference the security considerations
discussed in any other documents?

There may also be some banal things to say about the security of the
system as a whole being compromised if any omissions are made when
building the parts for measuring code, configuration, etc.

Section 5.1

  With these elements, the device's manufacturer and serial number can
  be identified by analyzing the DevID certificate plus the chain of
  intermediate certificates leading back to the manufacturer's root
  certificate.  As is conventional in TLS or SSH connections, a random
  nonce must be signed by the device in response to a challenge,
  proving possession of its DevID private key.

  RIV uses the DevID to validate a TLS or SSH connection to the device
  as the attestation session begins.  Security of this process derives
  from TLS or SSH security, with the DevID providing proof that the
  session terminates on the intended device.  See [RFC8446], [RFC4253].

  Evidence of software integrity is delivered in the form of a quote
  signed by the TPM itself.  Because the contents of the quote are
  signed inside the TPM, any external modification (including

I think somewhere in here would be a good place to reiterate that we
require a binding between the DevID key and the AK as residing in the same
TPM on the device, and that we rely on the presence of the device serial
number as Subject information combined with trust in the manufacturer to
not reuse serial numbers (or sign bogus stuff) in order to obtain that
binding.
(Or maybe it fits better near the start of this section where we
specifically list the two different sets of keypairs.)

Section 5.2

  *  The entire device could be spoofed.  If the Verifier goes to
      appraise a specific Attester, it might be redirected to a
      different Attester.  Use of the 802.1AR Device Identity (DevID) in
      the TPM ensures that the Verifier's TLS or SSH session is in fact
      terminating on the right device.

We might mention that if the device in question is compromised it could
then go and tunnel the contents of that TLS or SSH session to a different
Attester.  (As I understand it, we then go on to talk about how such an
attack would be detected/prevented.)

  This is accomplished in RIV through use of an AK certificate with the
  same elements as the DevID (same manufacturer's serial number, signed
  by the same manufacturer's key), but containing the device's unique
  AK public key instead of the DevID public key.

I would probably reiterate that it is vital to the security of the system
to enforce that the AK and DevID certificates are signed by the same
manufacturer's key.

Section 5.4

  *  TCG document [Platform-DevID-TPM-2.0] shows how the initial
      Attestation keys can be used to certify LDevID and LAK keys.  Use
      of the LDevID and LAK allows the device owner to use a uniform
      identity structure across device types from multiple manufacturers
      (in the same way that an "Asset Tag" is used by many enterprises
      to identify devices they own).  [...]

I think we should go into more detail on how the requirements that applied
to manufacturers as relate to IDevID+IAK are translated to requirements on
device owners when they elect to use local device credentials.  E.g., the
requirement to use the same subject information in the certificates
remains, as does the requirement to not issue certs to multiple devices
that use the same identifier.  On the other hand, though, the requirement
for being signed "by the same manufacturer key" seems to need
modification, as the "same key" is going go be higher up in the
certification path now.  (Hmm, maybe in a slightly different spot in the
section, as it also applies to the "any other mechanism" bullet point.)

  Clearly, local keys can't be used for secure Zero Touch provisioning;
  installation of the local keys can only be done by some process that
  runs before the device is installed for network operation.

How does this assertion relate to what BRSKI (RFC 8995) does?

Section 5.5

  RIV also depends on reliable Reference Values, as expressed by the
  RIM [RIM].  The definition of trust procedures for RIMs is out of
  scope for RIV, and the device owner is free to use any policy to
  validate a set of reference measurements.  RIMs may be conveyed out-
  of-band or in-band, as part of the attestation process (see
  Section 3.1.3).  But for network devices, where software is usually
  shipped as a self-contained package, RIMs signed by the manufacturer
  and delivered in-band may be more convenient for the device owner.

Is there a risk of a "replay attack" for in-band delivery of RIM data?
That is, deliberaly giving the peer stale RIM data that corresponds to an
old (e.g., vulnerable) firmware instead of the latest one (for patched
firmware)?

Section 9.2

  to record the results, and a Root of Trust for Reporting to report
  the results [TCGRoT], [SP800-155], [SP800-193].

The [TCGRoT] reference contains the word "reporting" only once, in a
non-normative note that lists the "one or more security-specific
functions" that a RoT can perform, so it may not be a particularly good
reference here.  [SP800-193] seems to mention reporting only insofar as to
say that RTRec is for Recovery, not Reporting.

Section 9.4

  --------------------------------------------------------------------
  | Connect the TPM to the TLS stack                | Vendor TLS    |
  |    o  Use the DevID in the TPM to authenticate  | stack (This    |
  |      TAP connections, identifying the device  | action is      |
  |                                                | simply        |
  |                                                | configuring TLS|
  |                                              | to use the DevID |
  |                                              | as its client    |
  |                                              | certificate)    |

Configuring a TLS stack to use a certificate with inaccessible private key
is not always a "simple" action :)

  | Make CoSWID tags for BIOS/Loader/Kernel objects | IETF CoSWID    |

Should we use RFC numbers/I-D names in addition to prose names?

Section 10.1

It will be interesting to see what the RFC Editor thinks about [IMA] as a
normative reference.  I seem to recall some controversy over in NFSv4
about whether IMA was suitable to reference in an RFC...

RFC 7950 is cited only once, in a context that does not call out to be
classified as normative.  (Perhaps it should be cited from other locations
if it is indeed expected to be normative?)

I'm not convinced that RFC 8572 needs to be classified as normative.
While it does appear adjacent to a MUST, that seems to be of the form "if
you might be used for 8572, you MUST do  to be prepared".  Only the
seems normative in that construction, not any use of 8572.

Section 10.2

If "A normative taxonomy of terms is given in
[I-D.ietf-rats-architecture]", how could we possibly classify that draft
as informative?

NITS

I found both https://github.com/ietf-rats-wg and
https://github.com/ietf-rats but neither seemed to have a repo that holds
current and ongoing development for this document, so I gave up and am
submitting these the old-fashioned way.

Section 1

  A generic architecture for remote attestation has been defined in
  [I-D.ietf-rats-architecture].  Additionally, the use cases for
  remotely attesting networking devices are discussed within Section 6
  of [I-D.richardson-rats-usecases].  [...]

I suggest s/the use cases/use cases/ -- no need to implicitly claim to be
an exhaustive listing.

Section 1.2

  or a threat detection and mitigation tool, etc.).  While informally
  referred to as attestation, this document focuses on a specific
  subset of attestation tasks, defined here as Remote Integrity
  Verification (RIV).  RIV takes a network equipment centric
  perspective that includes a set of protocols and procedures for

I suggest s/RIV takes/RIV in this document takes/

I also think that "network-equipment-centric" should be hyphenated, but
the RFC Editor will probably catch it if we're unsure.

Section 1.5

  Software used to boot a device can be described as a chain of
  measurements, anchored at the start by a Root of Trust for

I don't think that software in general can be described *as* a bunch of
measurements.  To say it is described *by* a bunch of measurements seems
much less problematic.

Section 1.7

  *  This solution is for use in non-privacy-preserving applications
      (for example, networking, Industrial IoT), avoiding the need for a
      Privacy Certificate Authority for attestation keys [AK-Enrollment]

The referenced document seems to indicate that the term "Attestation CA"
is now preferred to "Privacy CA".

  *  Run-Time Attestation: The Linux Integrity Measurement Architecture
      [IMA] attests each process launched after a device is started (and
      is in scope for RIV), but continuous run-time attestation of Linux

Perhaps "in scope for RIV in general"?

      or other multi-threaded operating system processes after they've
      started considerably expands the scope of the problem.  Many

I think that, sentence-structure wise, "they've" refers to the processes
having started, but perhaps we intend to refer to the OSes as having
started?

  *  Processor Sleep Modes: Network equipment typically does not
      "sleep", so sleep and hibernate modes are not considered.
      Although out of scope for RIV, Trusted Computing Group
      specifications do encompass sleep and hibernate states.

Are they out of scope for RIV in general or just for RIV as handled in
this document (for network equipment)?

  *  Virtualization and Containerization: In a non-virtualized system,
      the host OS is responsible for measuring each User Space file or
      process, but that's the end of the boot process.  For virtualized

We could probably tighten this up around "that's the end of the boot
process".  Is it that "the boot process (which is what this document
considers itself with) ends once the files have been verified" or maybe
"such measurement occurs after the boot process has completed"?

Section 2.1

      Reset---------------flow-of-time-during-boot--...------->

Is the '...' (vs '---') intentional?

Section 2.3

  2.  For devices using UEFI and Linux, measurements of firmware and
      bootable modules MUST be taken according to TCG PC Client
      [PC-Client-EFI-TPM-1.2] or [PC-Client-BIOS-TPM-2.0], and Linux
      IMA [IMA]

Full stop at end of sentence.

Section 3.3

Figure 5 lacks a "Step 0B" annotation (though I'd be hard-pressed to find
a place to fit it in)

Section 9.3

Why is there a box in Figure 6 for UDP, that doesn't line up with anything
else?

Also, the TAP (PTS2.0) box seems misaligned.

(Via drafts-lastcall@iana.org): IESG/Authors/WG Chairs:

The IANA Functions Operator has reviewed draft-ietf-rats-tpm-based-network-device-attest-10, which is currently in Last Call, and has the following comments:

We understand that this document doesn't require any registry actions.

While it's often helpful for a document's IANA Considerations section to remain in place upon publication even if there are no actions, if the authors strongly prefer to remove it, we do not object.

If this assessment is not accurate, please respond as soon as possible.

Thank you,

Sabrina Tanamal
Lead IANA Services Specialist

The following Last Call announcement was sent out (ends 2022-01-19):

From: The IESG
To: IETF-Announce
CC: draft-ietf-rats-tpm-based-network-device-attest@ietf.org, ncamwing@cisco.com, rats-chairs@ietf.org, rats@ietf.org, rdd@cert.org
Reply-To: last-call@ietf.org
Sender:
Subject: Last Call:  (TPM-based Network Device Remote Integrity Verification) to Informational RFC


The IESG has received a request from the Remote ATtestation ProcedureS WG
(rats) to consider the following document: - 'TPM-based Network Device Remote
Integrity Verification'
  as Informational
  RFC

The IESG plans to make a decision in the next few weeks, and solicits final
comments on this action. Please send substantive comments to the
last-call@ietf.org mailing lists by 2022-01-19. Exceptionally, comments may
be sent to iesg@ietf.org instead. In either case, please retain the beginning
of the Subject line to allow automated sorting.

Abstract


  This document describes a workflow for remote attestation of the
  integrity of firmware and software installed on network devices that
  contain Trusted Platform Modules [TPM1.2], [TPM2.0], as defined by
  the Trusted Computing Group (TCG).




The file can be obtained via
https://datatracker.ietf.org/doc/draft-ietf-rats-tpm-based-network-device-attest/



No IPR declarations have been submitted directly on this I-D.

Shepherd writeup for draft-ietf-rats-yang-tpm-charra and draft-ietf-rats-tpm-based-network-device-attest

1. Summary
This publication request covers two related drafts for enabling Remote Attestations on devices that contain TPMs:
- draft-ietf-rats-tpm-based-network-device-attest: is submitted to be published as an informational RFC as it describes the profile or workflow for affecting a TPM based remote attestation
- draft-ietf-rats-yang-tpm-charra: is submitted to be published as a standards RFC as it defines the Yang Data model for enabling a challenge-response remote attestation using TPMs
As the draft-ietf-rats-tpm-based-network-device-attest provides an overview and guidance for affecting TPM based remote attestations it depends on the  draft-ietf-rats-yang-tpm-charra draft; as such, they are submitted together with their intended status also indicated in their title page headers.


2. Document Announcement Write-up

Technical Summary:

A Yang RPCs and configuration nodes are defined in draft-ietf-rats-yang-tpm-charra (aka “charra”) to facilitate the retrieval of attestation evidence about integrity measurements from a device on TPM based devices.  The workflow and guidance for enabling remote integrity verifications on these TPM based devices are further described in draft-ietf-rats-tpm-based-network-device-attest.

Working Group Summary:

These documents were one of the first set of adopted and working group documents, with salient discussions to mature both specifications.  In addition, the “charra” draft received both early and WGLC Yang doctor review to ensure it was following appropriate norms and conventions all comments received have been addressed.

Document Quality:
Both documents are well written and has gone through working group review as well as external (TCG participant) reviews.  The YANG module definitions have gone through both early and WGLC Yang doctor review.



Personnel:
Nancy Cam-Winget is the Document Shepherd
Roman Danyliw is the responsible Area Director

(3) Briefly describe the review of this document that was performed by the Document Shepherd. If this version of the document is not ready for publication, please explain why the document is being forwarded to the IESG.
I have reviewed both documents throughout the comment review period and reached out to the Yang Doctors mail list to solicit review and follow up.  At this time, both documents have received solid review with all comments addressed, some interoperability implementations have also occurred to mature the document to its current state.  I believe the documents are now ready for publication.

(4) Does the document Shepherd have any concerns about the depth or breadth of the reviews that have been performed?
No.

(5) Do portions of the document need review from a particular or from broader perspective, e.g., security, operational complexity, AAA, DNS, DHCP, XML, or internationalization? If so, describe the review that took place.
The only review needed was for the Yang modules which has been reviewed by both the working group as well as the Yang Doctors representative (Mahesh Jethanandani).

(6) Describe any specific concerns or issues that the Document Shepherd has with this document that the Responsible Area Director and/or the IESG should be aware of? For example, perhaps he or she is uncomfortable with certain parts of the document, or has concerns whether there really is a need for it. In any event, if the WG has discussed those issues and has indicated that it still wishes to advance the document, detail those concerns here.
No concerns.

(7) Has each author confirmed that any and all appropriate IPR disclosures required for full conformance with the provisions of BCP 78 and BCP 79 have already been filed. If not, explain why?
All authors for draft-ietf-rats-tpm-based-network-device-attest have asserted no knowledge of IPR. The main authors for the draft-ietf-rats-yang-tpm-charra have disclosed that they are not aware of any IPR issues; one of the authors (Frank Xia) has since moved on from focusing on this document and has not responded.

(8) Has an IPR disclosure been filed that references this document? If so, summarize any WG discussion and conclusion regarding the IPR disclosures.
No disclosures for either drafts have been filed.

(9) How solid is the WG consensus behind this document? Does it represent the strong concurrence of a few individuals, with others being silent, or does the WG as a whole understand and agree with it?
There was strong consensus that both of these drafts are ready for publication.

(10) Has anyone threatened an appeal or otherwise indicated extreme discontent? If so, please summarise the areas of conflict in separate email messages to the Responsible Area Director. (It should be in a separate email because this questionnaire is publicly available.)
No.

(11) Identify any ID nits the Document Shepherd has found in this document. (See http://www.ietf.org/tools/idnits/ and the Internet-Drafts Checklist). Boilerplate checks are not enough; this check needs to be thorough.
There are 4 warnings in draft-ietf-rats-tpm-based-network-device-attest-08 : these are due to document referencing an array that the idnits tool is confusing as a reference.  The document also includes informative references to drafts that are still under construction and thus the revisions are not updated.

There are 3 errors in draft-ietf-rats-yang-tpm-charra-10.txt : as the document includes references to the network device attestation draft that is being requested to publish at the same time.  It is also referencing an informational draft (the RATS Architecture) which is continuously being revised and has also completed WGLC and should be going to IESG for publication request soon.


(12) Describe how the document meets any required formal review criteria, such as the MIB Doctor, YANG Doctor, media type, and URI type reviews.
The draft-ietf-rats-tpm-based-network-device-attest does not have any such requirements.
The draft-ietf-rats-yang-tpm-charra has undergone YANG Doctor review both prior to WGLC and as part of the WGLC, comments were received and addressed in both reviews.
The datatracker tools shows lint errors that is actually due to a bug in Yanglint itself for which a ticket was opened (https://github.com/CESNET/libyang/issues/1674) and resolved with the note that the yangvalidator is still using an older version of yanglint.


(13) Have all references within this document been identified as either normative or informative?
Yes. 

(14) Are there normative references to documents that are not ready for advancement or are otherwise in an unclear state? If such normative references exist, what is the plan for their completion?
These two drafts are being packaged together as the “network device attestation” draft is a profile guide for affecting remote attestations using the “CHARRA” draft, so there are references to these drafts that can be addressed as they’re packaged together.
They also reference the draft-ietf-rats-architecture and draft-ietf-rats-reference-interaction-models which are informational drafts that may not push to publication until the standards based specifications (such as “CHARRA”) mature and publish first; this was the working group’s decision to ensure that the RATs overview for how components “fit” (e.g. in the architecture) and how they flow together (e.g. interaction model) go together.



(15) Are there downward normative references references (see RFC 3967)? If so, list these downward references to support the Area Director in the Last Call procedure.
There are two drafts, one of which is interdependent and is packaged to publish at the same time (e.g. draft-ietf-rats-tpm-based-network-device-attest) .
The second draft, draft-ietf-rats-architecture has also completed WGLC and is expected to go to IESG request to publish sometime soon.



(16) Will publication of this document change the status of any existing RFCs? Are those RFCs listed on the title page header, listed in the abstract, and discussed in the introduction? If the RFCs are not listed in the Abstract and Introduction, explain why, and point to the part of the document where the relationship of this document to the other RFCs is discussed. If this information is not in the document, explain why the WG considers it unnecessary.
No.

(17) Describe the Document Shepherd's review of the IANA considerations section, especially with regard to its consistency with the body of the document. Confirm that all protocol extensions that the document makes are associated with the appropriate reservations in IANA registries. Confirm that any referenced IANA registries have been clearly identified. Confirm that newly created IANA registries include a detailed specification of the initial contents for the registry, that allocations procedures for future registrations are defined, and a reasonable name for the new registry has been suggested (see RFC 8126).
I have reviewed the request for IANA assignments that they look to comply with both the XML (RFC3688) and Yang parameter registries (RFC 6020).

(18) List any new IANA registries that require Expert Review for future allocations. Provide any public guidance that the IESG would find useful in selecting the IANA Experts for these new registries.
The registry requests are for the XML namespace for TPM based remote attestation and its crypto algorithms.

(19) Describe reviews and automated checks performed by the Document Shepherd to validate sections of the document written in a formal language, such as XML code, BNF rules, MIB definitions, YANG modules, etc.
I have performed both the IDNits and the Yang verification tools and provided my findings.

(20) If the document contains a YANG module, has the module been checked with any of the recommended validation tools (https://trac.ietf.org/trac/ops/wiki/yang-review-tools) for syntax and formatting validation? If there are any resulting errors or warnings, what is the justification for not fixing them at this time? Does the YANG module comply with the Network Management Datastore Architecture (NMDA) as specified in RFC8342?
The Yang Doctor (Mahesh) has done a thorough review, the “charra” draft actually found a bug in the lint tool for which a ticket was opened.  I have run  https://yangcatalog.org/yangvalidator/validator against the draft and see no errors.

Shepherd writeup for draft-ietf-rats-yang-tpm-charra and draft-ietf-rats-tpm-based-network-device-attest

1. Summary
This publication request covers two related drafts for enabling Remote Attestations on devices that contain TPMs:
- draft-ietf-rats-tpm-based-network-device-attest: is submitted to be published as an informational RFC as it describes the profile or workflow for affecting a TPM based remote attestation
- draft-ietf-rats-yang-tpm-charra: is submitted to be published as a standards RFC as it defines the Yang Data model for enabling a challenge-response remote attestation using TPMs
As the draft-ietf-rats-tpm-based-network-device-attest provides an overview and guidance for affecting TPM based remote attestations it depends on the  draft-ietf-rats-yang-tpm-charra draft; as such, they are submitted together with their intended status also indicated in their title page headers.


2. Document Announcement Write-up

Technical Summary:

A Yang RPCs and configuration nodes are defined in draft-ietf-rats-yang-tpm-charra (aka “charra”) to facilitate the retrieval of attestation evidence about integrity measurements from a device on TPM based devices.  The workflow and guidance for enabling remote integrity verifications on these TPM based devices are further described in draft-ietf-rats-tpm-based-network-device-attest.

Working Group Summary:

These documents were one of the first set of adopted and working group documents, with salient discussions to mature both specifications.  In addition, the “charra” draft received both early and WGLC Yang doctor review to ensure it was following appropriate norms and conventions all comments received have been addressed.

Document Quality:
Both documents are well written and has gone through working group review as well as external (TCG participant) reviews.  The YANG module definitions have gone through both early and WGLC Yang doctor review.



Personnel:
Nancy Cam-Winget is the Document Shepherd
Roman Danyliw is the responsible Area Director

(3) Briefly describe the review of this document that was performed by the Document Shepherd. If this version of the document is not ready for publication, please explain why the document is being forwarded to the IESG.
I have reviewed both documents throughout the comment review period and reached out to the Yang Doctors mail list to solicit review and follow up.  At this time, both documents have received solid review with all comments addressed, some interoperability implementations have also occurred to mature the document to its current state.  I believe the documents are now ready for publication.

(4) Does the document Shepherd have any concerns about the depth or breadth of the reviews that have been performed?
No.

(5) Do portions of the document need review from a particular or from broader perspective, e.g., security, operational complexity, AAA, DNS, DHCP, XML, or internationalization? If so, describe the review that took place.
The only review needed was for the Yang modules which has been reviewed by both the working group as well as the Yang Doctors representative (Mahesh Jethanandani).

(6) Describe any specific concerns or issues that the Document Shepherd has with this document that the Responsible Area Director and/or the IESG should be aware of? For example, perhaps he or she is uncomfortable with certain parts of the document, or has concerns whether there really is a need for it. In any event, if the WG has discussed those issues and has indicated that it still wishes to advance the document, detail those concerns here.
No concerns.

(7) Has each author confirmed that any and all appropriate IPR disclosures required for full conformance with the provisions of BCP 78 and BCP 79 have already been filed. If not, explain why?
All authors for draft-ietf-rats-tpm-based-network-device-attest have asserted no knowledge of IPR. The main authors for the draft-ietf-rats-yang-tpm-charra have disclosed that they are not aware of any IPR issues; one of the authors (Frank Xia) has since moved on from focusing on this document and has not responded.

(8) Has an IPR disclosure been filed that references this document? If so, summarize any WG discussion and conclusion regarding the IPR disclosures.
No disclosures for either drafts have been filed.

(9) How solid is the WG consensus behind this document? Does it represent the strong concurrence of a few individuals, with others being silent, or does the WG as a whole understand and agree with it?
There was strong consensus that both of these drafts are ready for publication.

(10) Has anyone threatened an appeal or otherwise indicated extreme discontent? If so, please summarise the areas of conflict in separate email messages to the Responsible Area Director. (It should be in a separate email because this questionnaire is publicly available.)
No.

(11) Identify any ID nits the Document Shepherd has found in this document. (See http://www.ietf.org/tools/idnits/ and the Internet-Drafts Checklist). Boilerplate checks are not enough; this check needs to be thorough.
There are 4 warnings in draft-ietf-rats-tpm-based-network-device-attest-08 : these are due to document referencing an array that the idnits tool is confusing as a reference.  The document also includes informative references to drafts that are still under construction and thus the revisions are not updated.

There are 3 errors in draft-ietf-rats-yang-tpm-charra-10.txt : as the document includes references to the network device attestation draft that is being requested to publish at the same time.  It is also referencing an informational draft (the RATS Architecture) which is continuously being revised and has also completed WGLC and should be going to IESG for publication request soon.


(12) Describe how the document meets any required formal review criteria, such as the MIB Doctor, YANG Doctor, media type, and URI type reviews.
The draft-ietf-rats-tpm-based-network-device-attest does not have any such requirements.
The draft-ietf-rats-yang-tpm-charra has undergone YANG Doctor review both prior to WGLC and as part of the WGLC, comments were received and addressed in both reviews.
The datatracker tools shows lint errors that is actually due to a bug in Yanglint itself for which a ticket was opened (https://github.com/CESNET/libyang/issues/1674) and resolved with the note that the yangvalidator is still using an older version of yanglint.


(13) Have all references within this document been identified as either normative or informative?
Yes. 

(14) Are there normative references to documents that are not ready for advancement or are otherwise in an unclear state? If such normative references exist, what is the plan for their completion?
These two drafts are being packaged together as the “network device attestation” draft is a profile guide for affecting remote attestations using the “CHARRA” draft, so there are references to these drafts that can be addressed as they’re packaged together.
They also reference the draft-ietf-rats-architecture and draft-ietf-rats-reference-interaction-models which are informational drafts that may not push to publication until the standards based specifications (such as “CHARRA”) mature and publish first; this was the working group’s decision to ensure that the RATs overview for how components “fit” (e.g. in the architecture) and how they flow together (e.g. interaction model) go together.



(15) Are there downward normative references references (see RFC 3967)? If so, list these downward references to support the Area Director in the Last Call procedure.
There are two drafts, one of which is interdependent and is packaged to publish at the same time (e.g. draft-ietf-rats-tpm-based-network-device-attest) .
The second draft, draft-ietf-rats-architecture has also completed WGLC and is expected to go to IESG request to publish sometime soon.



(16) Will publication of this document change the status of any existing RFCs? Are those RFCs listed on the title page header, listed in the abstract, and discussed in the introduction? If the RFCs are not listed in the Abstract and Introduction, explain why, and point to the part of the document where the relationship of this document to the other RFCs is discussed. If this information is not in the document, explain why the WG considers it unnecessary.
No.

(17) Describe the Document Shepherd's review of the IANA considerations section, especially with regard to its consistency with the body of the document. Confirm that all protocol extensions that the document makes are associated with the appropriate reservations in IANA registries. Confirm that any referenced IANA registries have been clearly identified. Confirm that newly created IANA registries include a detailed specification of the initial contents for the registry, that allocations procedures for future registrations are defined, and a reasonable name for the new registry has been suggested (see RFC 8126).
I have reviewed the request for IANA assignments that they look to comply with both the XML (RFC3688) and Yang parameter registries (RFC 6020).

(18) List any new IANA registries that require Expert Review for future allocations. Provide any public guidance that the IESG would find useful in selecting the IANA Experts for these new registries.
The registry requests are for the XML namespace for TPM based remote attestation and its crypto algorithms.

(19) Describe reviews and automated checks performed by the Document Shepherd to validate sections of the document written in a formal language, such as XML code, BNF rules, MIB definitions, YANG modules, etc.
I have performed both the IDNits and the Yang verification tools and provided my findings.

(20) If the document contains a YANG module, has the module been checked with any of the recommended validation tools (https://trac.ietf.org/trac/ops/wiki/yang-review-tools) for syntax and formatting validation? If there are any resulting errors or warnings, what is the justification for not fixing them at this time? Does the YANG module comply with the Network Management Datastore Architecture (NMDA) as specified in RFC8342?
The Yang Doctor (Mahesh) has done a thorough review, the “charra” draft actually found a bug in the lint tool for which a ticket was opened.  I have run  https://yangcatalog.org/yangvalidator/validator against the draft and see no errors.