Heuristics for Detecting ESP-NULL Packets
draft-ietf-ipsecme-esp-null-heuristics-07

[Ballot discuss]
Its good that we have this document. However, I had a few
issues that we should atleast discuss before shipping the
document to the RFC Editor. First, the document says:

  In both IPv4 and IPv6 the heuristics can also check the IP addresses
  either to be in the known range (for example check that both IPv6
  source and destination have same prefix etc), or checking addresses
  across more than one packet.

I do not understand what you mean by the same prefix here. Obviously
in IPv6 the source and destination do not have to have the same
prefix.

Second, the document says:

  One way to enforce deep inspection for
  all traffic, is to forbid encrypted ESP completely, in which case
  ESP-NULL detection is easier, as all packets must be ESP-NULL based
  on the policy, and further restrictions can eliminate ambiguities in
  ICV and IV sizes.

Is this a circular argument? If per policy everything is ESP-NULL, why
do you have to check to begin with? And if there's someone who might
be sending encrypted ESP, then you don't appear to be able to assume
anything special about the packets.

Perhaps you wanted to say that if there are some servers that are in
control of the network's owner, they can require ESP-NULL and hence
everyone who talks with those servers is forced to do ESP-NULL. But
I'm not sure what it has to do with the topic of this document.

Finally, I think the document should be clearer about the failure
modes and implications of those failures. Even if the probability
of misclassification is small, if it causes the packet to be dropped
per policy this can have significant negative effects. Its not even
clear that retransmission would always help. (Or would it, if there
was a new IV and the packet would look randomly different?) Does
the document recommend dropping all encrypted packets as one mode
of operation? Please describe what is the effect of classification
failures is in this case (false positive for detecting encrypted packet).
Does the document recommend dropping packets that match a certain
pattern? Please describe what the effect of failures is in this case
(false negative for detecting encrypted packet).

[Ballot discuss]
The document says:

  In both IPv4 and IPv6 the heuristics can also check the IP addresses
  either to be in the known range (for example check that both IPv6
  source and destination have same prefix etc), or checking addresses
  across more than one packet.

I do not understand what you mean by the same prefix here. Obviously
in IPv6 the source and destination do not have to have the same
prefix.

[Ballot comment]
The heuristics seem too weak to recommend for UDP. The misclassification of UDP such as RTP as IPSEC seems like it will do more harm than good. DPI devices will misclassify then fail to apply the right policy. It will be extremely hard to debug in the network as it will only happen to some of the RTP stream.

[Ballot comment]
A thorough piece of work. Thanks.

I think the Abstract may be a little terse.

  to quickly decide whether given packet flow is interesting
  or not

This phrase doesn't make anything clear. I would prefer you say what you
are attempting to determine and why.

Document name: Heuristics for Detecting ESP-NULL packets,
draft-ietf-ipsecme-esp-null-heuristics-03.txt

(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 is Yaron Sheffer, co-chair of the ipsecme WG. I have
reviewed it and believe it is ready for publication.

(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?

The document has had in-depth review within the ipsecme WG. It took a bit of prodding, but we finally got a sufficient number of in-depth reviews. I am not aware of any non-WG reviews. I do not have any concerns about these reviews.

(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?

No concerns, the document lies fully within the ipsecme WG's area of
expertise.

(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 such concerns. There have been no IPR disclosures.

(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 wide WG consensus.

(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.)

No, there were no such conflicts.

(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?

Yes, I have personally verified that. No formal review criteria are
applicable.

(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].

No issues identified.

(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 [RFC5226]. 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?

The documents requires no IANA actions.

(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?

There are no such sections. A large portion of the document is written in pseudocode, which unfortunately is not amenable to automatic verification, even at the syntactic level.

(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
Relevant content can frequently be found in the abstract
and/or introduction of the document. If not, this may be
an indication that there are deficiencies in the abstract
or introduction.

This document describes a set of heuristics for distinguishing IPsec ESP-null (Encapsulating Security Payload without encryption) packets from encrypted ESP packets. These heuristics can be used on intermediate devices, such as traffic analyzers and deep inspection engines, to quickly decide whether given packet flow is interesting or not. Use of these heuristics does not require any changes made on existing RFC 4303 compliant IPsec hosts.

Working Group Summary
Was there anything in WG process that is worth noting? For
example, was there controversy about particular points or
were there decisions where the consensus was particularly
rough?

Early on there was prolonged WG discussion about the relative merits of the Wrapped ESP solution for identifying ESP-null traffic, compared to heuristic methods for traffic inspection. Eventually the WG reached consensus on the usefulness of having both solutions published, with the heuristics solution targeted for the interim period until WESP is widely deployed. This consensus is documented in both protocol documents.

Document Quality
Are there existing implementations of the protocol? Have a
significant number of vendors indicated their plan to
implement the specification? Are there any reviewers that
merit special mention as having done a thorough review,
e.g., one that resulted in important changes or a
conclusion that the document had no substantive issues? If
there was a MIB Doctor, Media Type or other expert review,
what was its course (briefly)? In the case of a Media Type
review, on what date was the request posted?

We are not aware of any implementations. Neither do we know of any concrete
vendor plans to implement this specification.