Problem Statement on the Cross-Realm Operation of Kerberos
RFC 5868

Received changes through RFC Editor sync (changed abstract to 'This document provides background information regarding large-scale Kerberos deployments in the industrial sector, with the aim of identifying issues in the current Kerberos cross-realm authentication model as defined in RFC 4120.

This document describes some examples of actual large-scale industrial systems, and lists requirements and restrictions regarding authentication operations in such environments. It also identifies a number of requirements derived from the industrial automation field. Although they are found in the field of industrial automation, these requirements are general enough and are applicable to the problem of Kerberos cross-realm operations. This document is not an Internet Standards Track specification; it is published for informational purposes.')

[Ballot discuss]
Brian Carpenter provided a Gen-ART review of -04.  There where substantial
  changes to create -05.  Brian was not able to review all of the changes,
  but he does report that hes concerns with sections 5.5 and 5.6 were not
  resolved.  Brian's summary of his concerns is below.  These concerns
  deserve discussion.

  Section 5.5 makes a general assumption that a TGS exchange taking ~200ms
  is okay, but several times this is not. That may be true for the particular
  type of control system the authors consider, but may be wildly wrong (in
  either direction) for other controls applications. Also, the associated
  recommendations R-6 and R-7 are written as generalisations that I don't
  think offer any useful engineering guidance for protocol design.

  Section 5.6 describes a chicken-and-egg problem in authentication for
  roaming users but all it really does is transfer that chicken-and-egg
  problem into requirements R-3 and R-4. It's very circular, and the
  correct conclusion might be quite different: don't even try to solve
  this using Kerberos; use an IPsec (or TLS or SSH) session to connect
  into the home Kerberos domain.

This is a request to the IESG to approve publication of
"Problem statement on the cross-realm operation of Kerberos",
draft-ietf-krb-wg-cross-problem-statement-03.txt, as an Informational
RFC. This document is a product of the Kerberos Working Group.

(1.a) Who is the Document Shepherd for this document? Has the
Document Shepherd personally reviewed this version of the
document and, in particular, does he or she believe this
version is ready for forwarding to the IESG for publication?

>> The Document Shepherd for this document is Jeffrey Hutzelman,
>> . I have reviewed this document, and I believe
>> it is ready for IETF-wide review and publication as a
>> Proposed Standard.

(1.b) Has the document had adequate review both from key WG members
and from key non-WG members? Does the Document Shepherd have
any concerns about the depth or breadth of the reviews that
have been performed?

>> This document has received review both within the working group
>> and from key experts outside the working group. Any issues raised
>> have been resolved.

(1.c) Does the Document Shepherd have concerns that the document
needs more review from a particular or broader perspective,
e.g., security, operational complexity, someone familiar with
AAA, internationalization or XML?

>> I don't believe any particular outside review is required.
>> Of course, more review is always welcome.

(1.d) Does the Document Shepherd have any specific concerns or
issues 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. Has an IPR disclosure related to this document
been filed? If so, please include a reference to the
disclosure and summarize the WG discussion and conclusion on
this issue.

>> I have no concerns.
>> No IPR disclosures related to this document have been filed.

(1.e) 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 concensus within the working group to publish this
>> document. There is also consensus that standardized
>> solutions are desirable for some, but not necessarily all,
>> of the problems described in this document.

(1.f) 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
entered into the ID Tracker.)

>> There have been no expressions of discontent.

(1.g) Has the Document Shepherd personally verified that the
document satisfies all ID nits? (See
http://www.ietf.org/ID-Checklist.html and
http://tools.ietf.org/tools/idnits/). Boilerplate checks are
not enough; this check needs to be thorough. Has the document
met all formal review criteria it needs to, such as the MIB
Doctor, media type and URI type reviews?

>> This document has been run through the idnits tool, and was
>> reviewed manually for compliance with requirements not checked
>> by the automatic tool. No additional formal review criteria
>> apply to this document.

(1.h) Has the document split its references into normative and
informative? 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
strategy for their completion? Are there normative references
that are downward references, as described in [RFC3967]? If
so, list these downward references to support the Area
Director in the Last Call procedure for them [RFC3967].

>> References have been split appropriately. There are no
>> normative downward references or normative references to
>> documents that are not ready for advancement. Several
>> informative references are to URL's which may or may not
>> be stable; however, as these are provided for background
>> on companies, projects, and processor products, they are
>> relatively unimportant and no more stable reference is
>> likely to be available.

(1.i) Has the Document Shepherd verified that the document IANA
consideration section exists and is consistent with the body
of the document? If the document specifies protocol
extensions, are reservations requested in appropriate IANA
registries? Are the IANA registries clearly identified? If
the document creates a new registry, does it define the
proposed initial contents of the registry and an allocation
procedure for future registrations? Does it suggest a
reasonable name for the new registry? See [RFC2434]. If the
document describes an Expert Review process has Shepherd
conferred with the Responsible Area Director so that the IESG
can appoint the needed Expert during the IESG Evaluation?

>> This is an informational document describing various
>> problems related to cross-realm Kerberos operation. It is
>> descriptive in nature and as such, requires no action by
>> IANA.

(1.j) Has the Document Shepherd verified that sections of the
document that are written in a formal language, such as XML
code, BNF rules, MIB definitions, etc., validate correctly in
an automated checker?

>> No part of this document is written in a formal language
>> requiring such verification.

(1.k) 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

There are some issues when the cross-realm operation of the Kerberos
Version 5 [RFC4120] is employed into actual specific systems. This
document describes some examples of actual systems, and lists
requirements and restriction of the operation in such system. Then
it describes issues when we apply the cross-realm operation to such
system.


Working Group Summary

This document represents the consensus of the Kerberos Working Group.


Document Quality

This document does not specify a protocol; rather, it analyzes the
use of Kerberos cross-realm authentication and discusses a number
of issues which may impede some deployments. Solutions to some of
these problems are under active development.


Personnel

The Document Shepherd for this document is Jeffrey Hutzelman.
The responsible Area Director is Tim Polk.