Transport Layer Security (TLS) Extension for Token Binding Protocol Negotiation
draft-ietf-tokbind-negotiation-14

Shepherd Write-Up for "Transport Layer Security (TLS) Extension for Token Binding Protocol Negotiation"


(1) What type of RFC is being requested (BCP, Proposed Standard,
Internet Standard, Informational, Experimental, or Historic)?  Why
is this the proper type of RFC?  Is this type of RFC indicated in the
title page header?

This specification is proposed as a 'Proposed Standard' document. The
type of RFC is indicated. This document specifies a Transport Layer Security (TLS) [RFC5246] extension for the negotiation of Token Binding protocol [I-D.ietf-tokbind-protocol] version and key parameters.


(2) The IESG approval announcement includes a Document Announcement
Write-Up. Please provide such a Document Announcement Write-Up. Recent
examples can be found in the "Action" announcements for approved
documents. The approval announcement contains the following sections:


Technical Summary

In order to use the Token Binding protocol [I-D.ietf-tokbind-protocol], the client and server need to agree on the Token Binding protocol version and the parameters (signature algorithm, length) of the Token Binding key.  This document specifies a new TLS [RFC5246] extension to accomplish this negotiation without introducing additional network round-trips in TLS 1.2 and earlier versions.  The negotiation of the Token Binding protocol and key parameters in combination with TLS 1.3 and later versions is beyond the scope of this document.

Working Group Summary

This document achieved WG consensus and had no objections.

Document Quality

Multiple Implementations of Token Binding exist and have undergone informal interoperability testing.
Google has token binding behind a feature flag in Chrome that is currently defaulted off.  They have also implemented it in their reverse proxy infrastructure. They have also added support to the boringssl open source project.
Microsoft added support in Windows 10 RS2 at the beginning of 2017 (later back ported to RS1) .  Edge and IE use that platform support.  It is also available to other applications via system API.  There is also support in ADFS. https://docs.microsoft.com/en-us/windows-server/security/token-binding/introducing-token-binding
NGINX has an open source module https://github.com/google/ngx_token_binding
Token Binding support for Apache https://github.com/zmartzone/mod_token_binding
Openssl patches in opensource https://github.com/google/token_bind
Ping Identity has tested patches to Java and set up a test environment. https://www.ietf.org/mail-archive/web/unbearable/current/msg01332.html
A useful slide share overview https://www.slideshare.net/Identiverse/beyond-bearer-token-binding-as-the-foundation-for-a-more-secure-web-cis-2017
Drafts using token binding exist in the OAuth work group and for OpenID Connect.

Personnel

John Bradley is the document shepherd and the responsible area
director is Eric Rescorla.

(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.

The document shepherd was involved in the working group review process
and verified the document for correctness.

(4) Does the document Shepherd have any concerns about the depth or
breadth of the reviews that have been performed? 

There are no concerns regarding the document reviews.

(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.

No

(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.

The document shepherd has no concerns with the document.

(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.

The authors have confirmed full conformance with the provisions of BCP 78
and BCP 79:

A. Popov: https://mailarchive.ietf.org/arch/msg/unbearable/m4tDDn5jgZRUV1ODjKloTv7oQkA

M. Nystroem: https://mailarchive.ietf.org/arch/msg/unbearable/Gg0i1hTdnZ85Uu3MBNnCqwtwxoE

D. Balfanz: https://mailarchive.ietf.org/arch/msg/unbearable/Pxnj-Oo39hoaufrgMuuT-8Ulh98
A. Langley: https://mailarchive.ietf.org/arch/msg/unbearable/iCQdNsZaT3Z2cLSY_eQsSjaiJD4



(8) Has an IPR disclosure been filed that references this document?
If so, summarize any WG discussion and conclusion regarding the IPR
disclosures.

No IPR disclosures have been filed for this document.

(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 is solid consensus in the working group for publishing this
document.

(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.)

Nobody threatened an appeal or expressed extreme discontent.

(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.

The shepherd checked the document.

(12) Describe how the document meets any required formal review
criteria, such as the MIB Doctor, media type, and URI type reviews.

No formal review is needed.

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

Yes. The references are split into normative and informative references.

(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?

I-D.ietf-tokbind-protocol is part of this cluster of specs being submitted.


All other normative references are published RFCs.

(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 no downward normative references.

(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.

This document does not change the status of an existing RFC.

(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 5226).

This document does not request any actions by IANA.

(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.

None.

(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, etc.

There is no text in formal languages in the document.

[Ballot comment]
  struct {
      uint8 major;
      uint8 minor;
  } TB_ProtocolVersion;

I think naming them "major" and "minor" is misleading, because it doesn't actually mean anything.

Lack of description of how versionning is to be used makes me sad, but I understand that this was discussed in the WG.

[Ballot comment]
I agree with Adam and Warren's comments.

The point already made about version negotiation has a corollary
that if the client sends a dense list of versions, then the server
will know decisively that a specific version has (or has not) been
negotiated, and can rely on that at the application layer.  When the
client can receive an unsupported version back from the server, the
client will not use token binding and the server has to infer from
the client's application-layer traffic whether token binding is
expected to be in use.  (Whether or not this is a desired or useful
property to have is not necessarily clear.)


Section 4

  the client advertises, then the server MUST NOT include
  "token_binding" extension in the server hello.

Nit: """the "token_binding" extension"""


Section 6.1

  The Token Binding protocol version and key parameters are negotiated
  via "token_binding" extension within the TLS handshake. [...]

Nit: """the "token_binding" extension".  (Also at the end of this
paragraph.)

  [...] TLS prevents
  active attackers from modifying the messages of the TLS handshake,
  therefore it is not possible for the attacker to remove or modify the
  "token_binding" extension.

I wonder if we want to explicitly say *successful* TLS handshakes,
but given the context in the main protocol document it's probably
not necessary.

[Ballot comment]
Thanks for this document. I am balloting "yes", but have a few comments:

- I support Alexey's DISCUSS. Additionally, do I understand the version negotiation to require the client to support all previous version from the one it initially advertises? If so, how would you deprecate a version at some time in the future?

- I shared some of the confusion about this being limited to TLS 1.2 and earlier. In particular, there is repeating language that to the effect of "For TLS 1.2 and earlier...", which seems strange for a draft that only supports 1.2 in the first place.

§1.1: Please consider using the 8174 boilerplate across the cluster. While I did not find lower case keywords in this draft, I did in the other two and it would be best to be consistent across all three.

§2: "[I-D.ietf-tokbind-protocol] describes version {1, 0} of the protocol.": While one might infer that version to be {1,0} give the name "Token Binding 1.0", I never saw it explicitly mentioned.

Editorial Comments:

§2: "Please note that the server MAY select any lower protocol version, see Section 3": comma splice

[Ballot comment]
Please also see Will LIU's OpsDir review here: https://datatracker.ietf.org/doc/review-ietf-tokbind-negotiation-10-opsdir-lc-liu-2017-12-04/
It suggests a simple change which will remove confusion/ambiguity.

The document says (in the Introduction):
"The negotiation of the Token Binding protocol and key parameters in combination with TLS 1.3 and later versions is beyond the scope of this document."

How hard would it be to make it work with TLS 1.3? Actually, what part of it doesn't already? (I'm guessing I'm missing something super-obvious)...

[Ballot comment]
Addendum: the ARTART review raises a point that I believe should be fixed or clarified in the document: https://datatracker.ietf.org/doc/review-ietf-tokbind-negotiation-12-artart-telechat-miller-2018-05-08/

Original Comments:

I would really like to see a non-normative mention of draft-ietf-tokbind-tls13
in here, to let readers know that a TLS 1.3 solution is in progress rather than
merely being excluded from scope.

I also think the Abstract is incomplete without mentioning the limitation of
this document's mechanism to TLS 1.2 and lower.

[Ballot comment]
I would really like to see a non-normative mention of draft-ietf-tokbind-tls13
in here, to let readers know that a TLS 1.3 solution is in progress rather than
merely being excluded from scope.

I also think the Abstract is incomplete without mentioning the limitation of
this document's mechanism to TLS 1.2 and lower.

[Ballot discuss]
I will be switching to "Yes" once one issue mentioned below is discussed:

I would like to have a quick discussion about your versionning model:

  struct {
      uint8 major;
      uint8 minor;
  } TB_ProtocolVersion;

What is the significance of "major" and "minor" versions?
Any rules on what kind of changed would require increment of the "major" version.
Any restrictions on what must remain the same when the "major" (or "minor") version gets incremented?
Any requirements on backward compatibility when only the "minor" version is incremented?

[Ballot comment]
In Section 2:

  "key_parameters_list" contains the list of identifiers of the Token
  Binding key parameters supported by the client, in descending order
  of preference.  [I-D.ietf-tokbind-protocol] defines an initial set of
  identifiers for Token Binding key parameters.

Wouldn't be better to point to the IANA registry established by [I-D.ietf-tokbind-protocol]?
My concern is that you might be misleading implementors into not looking there.

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

The IANA Services Operator has completed its review of draft-ietf-tokbind-negotiation-10. If any part of this review is inaccurate, please let us know.

The IANA Services Operator understands that, upon approval of this document, there is a single action which we must complete.

In the ExtensionType Values registry located on the Transport Layer Security (TLS) Extensions registry page located at:

https://www.iana.org/assignments/tls-extensiontype-values/

the existing temporary registration

Value: 24
Extension name: token_binding

will be made permanent and its reference changed to [ RFC-to-be ].

We understand that this is the only action required of the IANA Services Operator upon approval of this document.

Thank you,

Amanda Baber
Lead IANA Services Specialist

The following Last Call announcement was sent out (ends 2017-11-27):

From: The IESG
To: IETF-Announce
CC: ekr@rtfm.com, John Bradley , unbearable@ietf.org, tokbind-chairs@ietf.org, ve7jtb@ve7jtb.com, draft-ietf-tokbind-negotiation@ietf.org
Reply-To: ietf@ietf.org
Sender:
Subject: Last Call:  (Transport Layer Security (TLS) Extension for Token Binding Protocol Negotiation) to Proposed Standard


The IESG has received a request from the Token Binding WG (tokbind) to
consider the following document: - 'Transport Layer Security (TLS) Extension
for Token Binding Protocol
  Negotiation'
  as Proposed Standard

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
ietf@ietf.org mailing lists by 2017-11-27. 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 specifies a Transport Layer Security (TLS) extension
  for the negotiation of Token Binding protocol version and key
  parameters.




The file can be obtained via
https://datatracker.ietf.org/doc/draft-ietf-tokbind-negotiation/

IESG discussion can be tracked via
https://datatracker.ietf.org/doc/draft-ietf-tokbind-negotiation/ballot/


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

Shepherd Write-Up for "Transport Layer Security (TLS) Extension for Token Binding Protocol Negotiation"


(1) What type of RFC is being requested (BCP, Proposed Standard,
Internet Standard, Informational, Experimental, or Historic)?  Why
is this the proper type of RFC?  Is this type of RFC indicated in the
title page header?

This specification is proposed as a 'Proposed Standard' document. The
type of RFC is indicated. This document specifies a Transport Layer Security (TLS) [RFC5246] extension for the negotiation of Token Binding protocol [I-D.ietf-tokbind-protocol] version and key parameters.


(2) The IESG approval announcement includes a Document Announcement
Write-Up. Please provide such a Document Announcement Write-Up. Recent
examples can be found in the "Action" announcements for approved
documents. The approval announcement contains the following sections:


Technical Summary

In order to use the Token Binding protocol [I-D.ietf-tokbind-protocol], the client and server need to agree on the Token Binding protocol version and the parameters (signature algorithm, length) of the Token Binding key.  This document specifies a new TLS [RFC5246] extension to accomplish this negotiation without introducing additional network round-trips in TLS 1.2 and earlier versions.  The negotiation of the Token Binding protocol and key parameters in combination with TLS 1.3 and later versions is beyond the scope of this document.

Working Group Summary

This document achieved WG consensus and had no objections.

Document Quality

Multiple Implementations of Token Binding exist and have undergone informal interoperability testing.
Google has token binding behind a feature flag in Chrome that is currently defaulted off.  They have also implemented it in their reverse proxy infrastructure. They have also added support to the boringssl open source project.
Microsoft added support in Windows 10 RS2 at the beginning of 2017 (later back ported to RS1) .  Edge and IE use that platform support.  It is also available to other applications via system API.  There is also support in ADFS. https://docs.microsoft.com/en-us/windows-server/security/token-binding/introducing-token-binding
NGINX has an open source module https://github.com/google/ngx_token_binding
Token Binding support for Apache https://github.com/google/ngx_token_binding
Openssl patches in opensource https://github.com/google/token_bind
Ping Identity has tested patches to Java and set up a test environment. https://www.ietf.org/mail-archive/web/unbearable/current/msg01332.html
A useful slide share overview https://www.slideshare.net/Identiverse/beyond-bearer-token-binding-as-the-foundation-for-a-more-secure-web-cis-2017
Drafts using token binding exist in the OAuth work group and for OpenID Connect.

Personnel

John Bradley is the document shepherd and the responsible area
director is Eric Rescorla.

(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.

The document shepherd was involved in the working group review process
and verified the document for correctness.

(4) Does the document Shepherd have any concerns about the depth or
breadth of the reviews that have been performed? 

There are no concerns regarding the document reviews.

(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.

No

(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.

The document shepherd has no concerns with the document.

(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.

The authors have confirmed full conformance with the provisions of BCP 78
and BCP 79:

A. Popov: https://mailarchive.ietf.org/arch/msg/unbearable/m4tDDn5jgZRUV1ODjKloTv7oQkA

M. Nystroem: https://mailarchive.ietf.org/arch/msg/unbearable/Gg0i1hTdnZ85Uu3MBNnCqwtwxoE

D. Balfanz: https://mailarchive.ietf.org/arch/msg/unbearable/Pxnj-Oo39hoaufrgMuuT-8Ulh98
A. Langley: https://mailarchive.ietf.org/arch/msg/unbearable/iCQdNsZaT3Z2cLSY_eQsSjaiJD4



(8) Has an IPR disclosure been filed that references this document?
If so, summarize any WG discussion and conclusion regarding the IPR
disclosures.

No IPR disclosures have been filed for this document.

(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 is solid consensus in the working group for publishing this
document.

(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.)

Nobody threatened an appeal or expressed extreme discontent.

(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.

The shepherd checked the document.

(12) Describe how the document meets any required formal review
criteria, such as the MIB Doctor, media type, and URI type reviews.

No formal review is needed.

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

Yes. The references are split into normative and informative references.

(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?

I-D.ietf-tokbind-protocol is part of this cluster of specs being submitted.


All other normative references are published RFCs.

(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 no downward normative references.

(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.

This document does not change the status of an existing RFC.

(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 5226).

This document does not request any actions by IANA.

(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.

None.

(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, etc.

There is no text in formal languages in the document.