Analysis of Possible DHCPv6 and CGA Interactions
draft-ietf-csi-dhcpv6-cga-ps-09

[Ballot discuss]

So since the authors clarified in -09 that this is not a problem statement
(seems late in the day but whatever) I re-read the document and re-wrote
my discuss points. However, the overall thrust of the discuss remains: I
don't see that this document is useful or needed.

But to the details:

#0 I agree with other discussing ADs.

#1 CGA's have privacy benefits, and the idea of "registering" those with a dhcp
server would entirely remove that feature.  I fail to see why a client would
*ever* want to register its CGA, and the document makes only one incidental
mention of privacy. That seems entirely insufficient to me. This echoes Russ'
discuss with which I fully agree. You could resolve this discuss point by for
example stating that, for privacy preserving reasons, there is no known
use-case where it would make sense for a DHCP client to use a CGA. Additional
changes would flow from that I would expect, if you were happy to take that
approach. (But then that leaves *very* little text.)

#2 Related to #1, but I don't get this bit:

  "However, after CGA has been defined, as an independent security
  property, many other CGA usages have been proposed and defined, such
  as SHIM6 [RFC5533], Enhanced Route Optimization for Mobile IPv6
  [RFC4866], etc. In these scenarios, CGAs may be used in DHCPv6-
  managed networks."

*Exactly* what use-cases exist for this involving a DHCP client?  You need to
explain, if you don't accept the approach suggested in #1.

#3 I agree that it might, in principle, be interesting to use CGAs for DHCP
servers or relays. However, I fail to see why section 4 (with DHCP client text
removed) justifies this document and only section 4 (<1 page) seems to
remain, if you accept #1. There are sometimes reasons why an RFC might
be worthwhile with only one page of real content but this is not one of
those cases IMO. You can just include that page in the relevant DHC WG
document.

I'm sorry, but I just don't think this is a useful document to produce.

[Ballot comment]
Updated for revision -09-

This  comment is about the inadequacies of security considerations. I think more would would be needed to assess whether the proposals contained in the document are viable in an Internet environment. To a large degree, these comments mirror those from other ADs, so I will simplify my discuss to save I support the discusses raised by Tim and Russ and Stephen and Sean.

[Ballot discuss]
Updated for revision -07-

This  discuss is about the lack of security considerations that would be needed to assess whether the proposals contained in the document are viable in an Internet environment. To a large degree, these comments mirror those from Tim and Russ.

1) This document includes multiple proposals for combining DHCPv6 and CGA; it might be better to write each one as a separate document, since the security implications of each of these proposals differs. The security considerations should discuss the threats associated with each proposal.

An alternative would be to include text with each proposal to discuss the security considerations related to that proposal. Some of the questions that deserve to be answered:

Do we need to worry about man-in-the-middle attacks, and if so, what impact would it have, and how do we mitigate that threat?
Do we need to worry about DoS attacks?
Do we need to worry about  integrity checking? replay?

[Ballot comment]
1) The change log has been modifed to reflect what changes have been made. That is much more useful than the chnage log in -05-. Thank you.

2) The English is rough. This document really needs review by a proficient English-speaker. In some cases the English is difficult to understand.

[Ballot discuss]
This  discuss is about the lack of security considerations that would be needed to assess whether the proposals contained in the document are viable in an Internet environment. To a large degree, these comments mirror those from Tim and Russ.

1) This document includes multiple proposals for combining DHCPv6 and CGA; it might be better to write each one as a separate document, since the security implications of each of these proposals differs. The security considerations should discuss the threats associated with each proposal.

An alternative would be to include text with each proposal to discuss the security considerations related to that proposal. Some of the questions that deserve to be answered:

Do we need to worry about man-in-the-middle attacks, and if so, what impact would it have, and how do we mitigate that threat?
Do we need to worry about DoS attacks?
Do we need to worry about  integrity checking? replay?

[Ballot comment]
#1) abstract and s1: Having trouble parsing the following:

OLD:

This document analyzes the possible interactions between DHCPv6 and
Cryptographically Generated Addresses (CGAs), and gives
recommendations and reasons whether these possibilities should be
developed as solutions or be declined in the future.

NEW:

This document analyzes the possible interactions between DHCPv6 and
Cryptographically Generated Addresses (CGAs), and gives
recommendations on whether or not these interactions should be
developed as solutions.

#2) s1:

OLD:

Then, configuring CGA-relevant parameters using DHCPv6 is
also discussed per parameters

NEW:

Then, configuring CGA-relevant parameters using DHCPv6 is
discussed.

#3) s2: The use of "should" here is throwing me off.  I think what you want to say is that for DHCP managed networks hosts get their addressed form DHCPv6 servers.

OLD:

However, in a DHCPv6-managed network, hosts should get their
addresses from DHCPv6 servers. This may result that a DHCPv6-managed
network declines the network access requests from CGA owners.

NEW:

However, hosts in DHCPv6-managed network get their
addresses from DHCPv6 servers. For a DHCPv6-managed
network, CGA owners could be declined network access.

#4) s2:

OLD:

There is no existing operation to
allow DHCPv6 servers to decline the requested CGA and reply
suggestion in order to generate a new address accordingly.

New DHCPv6 options may be defined to support DHCPv6 servers to
decline the requested CGA, notify the hosts the reason and give
suggestion information in order to generate a new CGA accordingly.

NEW:

There is no existing operation to
allow DHCPv6 servers to decline the host-requested address
and to reply with information to generate a a new address.

New DHCPv6 options could be defined to allow DHCPv6 servers to
decline requested-CGAs, to inform the host about why the address
has been declined, and to give
information needed to construct an acceptable CGA.

#5) s2:

OLD:

Specifically, a node can request that a DHCPv6 server grants the use
of a self-generated CGA by sending a DHCPv6 Request message.

NEW:

Specifically, a node could request that a DHCPv6 server grant the use
of a self-generated CGA by sending a DHCPv6 Request message.

#6) s3: r/it is not possible that network/it is not possible for network

and I think you could leave this bit off:

Hosts may generate such CGA in order to get access or use
network services.

You already made that point earlier.

r/Central managed/generated key/Centrally managed/generated keys

Again, maybe I'm over-reacting but this draft doesn't provide requirements:

r/Therefore, there are no requirements for network to
      configure/suggest it./
Therefore, a mechanism to configure/suggest a value is
not analyzed.

Actually do this one 3 times (public key/modifier/collision count).

#7) s4:

A
CGA option with an address ownership proof mechanism and a signature
option with a corresponding verification mechanism may be introduced
into DHCPv6 protocol. With these two new options, the receiver

NEW:

A
CGA option with an address ownership proof mechanism and a signature
option with a corresponding verification mechanism would allow the receiver

#8) s4:

OLD:

Then, hosts may decline the DHCPv6 messages
from other servers, which may be fake servers.

NEW:

Then, hosts can decline the DHCPv6 messages
from other servers.

They might be fake they might be real it's just not needed.

#9) s5:

r/computationally powerful to take such heavy burden, too.
/computationally powerful enough to also generate CGAs
for all of its hosts.

#10) s6:

OLD:

  A few interactions has been declined by the analysis, including

NEW:

  The analysis has determined that a few interactions
  are not worth pursuing including:

OLD:

  This document suggests a few possible interactions may be defined in
  the future:

  - allowing DHCPv6 servers to decline the requested CGA and reply
      suggestion in order to generate a new CGA accordingly,

  - using DHCPv6 to propagate prefix to hosts,

  - propagate the suggested Sec value to hosts,

  - DHCPv6 servers, relays or clients use CGA addresses as source
    addresses, also in DHCPv6 message exchanging.

NEW (lets have just one bullet for declining and replying and be specific about what can be replied, making it parallel too):

  This document suggests a few possible interactions be investigated:

  - allowing DHCPv6 servers to decline requested-CGAs and reply
    with Prefix or Sec values to generate an
    appropriate CGAs,

  - using CGA addresses for interactions between DHCPv6
    servers/relays and clients

#11) s7:

OLD:

  By allowing DHCPv6 servers to decline the requested CGA and reply
  suggestion in order to generate a new CGA accordingly, is actually
  increase the network access flexibility. This may also benefit the
  network security too.

NEW:

  Allowing DHCPv6 servers to decline the requested-CGA and reply
  with information to generate an appropriate CGA might actually
  increase network access flexibility. This might also benefit the
  network security too.

OLD (there's no mechanism yet and I don't think you're making recommendation hence may/can switch):

  Prefix is information that should be advertised. However, the new
  mechanism using DHCPv6 to propagate prefix to hosts gives attackers
  another way to propagate bogus prefixes, which may waste hosts
  resources.

NEW:

  Prefix is information that can be advertised. However, if
  DHCPv6 propagates the prefix to hosts, then attackers have
  another way to propagate bogus prefixes.  This can waste hosts'
  resources.

OLD:

  The suggested Sec value is only replied to the host when requested
  CGA is declined by the DHCPv6 server. For security reasons, networks
  should NOT enforce any CGA parameters. Otherwise, malicious attackers
  may use this enforcement to attack hosts. Networks may suggest
  certain CGA parameters, but host does not have to follow. However, if
  the hosts not follow, they may not be able to access part or full
  network services.

NEW (not sure I got this all right):

  When propagating the Sec value from the DHCPv6 server to host, it is
  only returned if the DHCPv6 declines the requested-CGA. For security
  reasons, networks SHOULD NOT enforce any CGA parameters.
  Enforcing CGA parameters could allow malicious attackers to attack
  hosts by forcing them to perform computationally intensive operations.
  Networks can suggest the Sec value, but hosts need not heed the
  suggestion. However, if the hosts do not follow the suggestion, then
  DHCPv6 servers might deny network services.

[Ballot discuss]
This is an updated position based on -07.

1) I share the concerns raised by others.

2) s1:  Using CGA to protect DHCPv6 is
  recommended though the concrete protocol is not defined in this
  document.

In s2 it say: also using the CGA for DHCPv6 security purpose, analyzed
  in section 4 this document, etc.

I didn't think this document was providing recommendations on analyzing possible solutions.  Maybe just delete this sentence?

3) s4: I'll have to think some more about this one:

  The usage of CGAs can also avoid DHCPv6's dependence on
  IPsec [RFC3315] in relay scenarios.

How do CGAs provide replay protection?

4) s4: contains the following about pre-configured a CGA-enabled DHCPv6 server:

But in this case the
address will be fixed. It may increase the vulnerability to, e.g.,
brute force attacks.

Brute force attacks against?

5) I think this is a typo but I want to be sure:

However, DHCPv6 servers are suitable to serve such computational
delegation requests from thousands clients.

Shouldn't this be "not suitable"

6) s7 contains the following:

  Without other pre-configured security mechanism, like pre-notified
  DHCPv6 server address, using host-based CGA by DHCPv6 servers could
  not prevent attacks claiming to be a DHCPv6 server.

I think you're talking about spoofing here.  Is this really true?  What happens when they use IPsec?

7) s7: One thing I think you also need to talk about is when the DHCPv6 server says no to the address based on a Sec value and then the DHCPv6 server says use a value one that is weaker.

[Ballot comment]
I reluctantly ballot "No objection" to this document, but given the other DISCUSSes, I think it's not an issue. Essentially, I agree with Stephen's first DISCUSS: I don't know why the publication of this document is necessary. In particular, I note that the writeup says:

  The document is an informational problem statement. The WG
  expressed no interest in working in the solutions to the problem
  though.

If the WG has no interest in addressing the issues here (indeed, there isn't a WG working on this problem anymore), and there are a list of questions not sufficiently addressed by this draft, it should probably be shelved until there is such a group. But it is only informational, so I won't object if it ends up going forward.

[Ballot discuss]
- I agree with the thrust of discusses from the previous IESG review.
Its hard to see why this document is useful.  If there are problems
with e.g. DHCP server authentication that can be solved in better
ways, then write about that. If there are networks that prefer some
CGA parameters over others then write about that Trying to mix these
things seems counter productive at best and is not explained in the
document that I can see.

- For the 1st problem (DHCPv6 server address checking) I don't see
that this describes a problem with a CGA related solution. There may
be some tailored solution for this problem that is tractable that
looks a bit like CGA but the argument as presented is backwards,
you're saying "DHCP server auth is hard, CGA exists, therefore
describing how CGA might be used for DHCP server auth is an
interesting problem statement." That really is backwards esp. in
the absence of an actual solution. (If you did have a clever scheme
I'd forgive the lack of problem-statement purity;-)

- For the 2nd "problem," is there evidence that its really a problem?
If so, why not quote that?

- The "computation delegation" seems to depend on the 2nd problem
actually being a problem. Even if it were, what's that got to do with
DHCP? CGA may depend on the prefix but that same prefix is used for
hosts that don't use DHCP at all. And the significant computations
don't depend on the prefix so can be done offline prior to any DHCP
exchanges so again I don't that a real problem exists here related
to DHCP.

In summary - where's the evidence there are real problems? And
if there is, what's the compelling argument for handling them in one
document?

State changed to In Last Call from Last Call Requested.

The following Last Call Announcement was sent out:

From: The IESG
To: IETF-Announce
CC:
Reply-To: ietf@ietf.org
Subject: Last Call:  (DHCPv6 and CGA Interaction: Problem Statement) to Informational RFC


The IESG has received a request from the CGA & SEND MaIntenance WG
(csi) to consider the following document:
- 'DHCPv6 and CGA Interaction: Problem Statement'
  as an 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
ietf@ietf.org mailing lists by 2011-11-04. 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 analyzes the possible interactions between DHCPv6 and
  Cryptographically Generated Addresses (CGAs), and gives
  recommendations and reasons whether these possibilities should be
  developed as solutions or be declined in the future. This document
  itself does NOT define any concrete solutions.

Note that this is a second IETF Last Call for this document.
draft-ietf-csi-dhcpv6-cga-ps-07.txt addresses points raised during the
first IESG review of the document.

The file can be obtained via
http://datatracker.ietf.org/doc/draft-ietf-csi-dhcpv6-cga-ps/

IESG discussion can be tracked via
http://datatracker.ietf.org/doc/draft-ietf-csi-dhcpv6-cga-ps/


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

[Ballot discuss]
This is an updated position.

I believe that using CGAs with DHCP will be harmful to the Internet because it defeats one of the two primary purpose for CGAs, namely privacy.

1)  When doing an analysis it's okay to state that a particular solution can be done but shouldn't be done.  I think DHCPv6 combined with CGA is one of those.

I share Russ' concerns and I think there are a number of other issues with the draft:

2) Sec 2: States:

The public key system associated with the CGA address provides
message origin validation and integrity protection without the need
for negotiation and transportation of key materials.

There's two problems with this statement: 1) There is no public key system with CGAs. It's just one public key, the whole point was there's no PKI (aka public key system).  2) CGAs include the public key so there is a need to transport key material.

3) Sec 2: States:

The current CGA specifications do not mandate which device generates
a CGA address.

I thought the CGA specification was pretty clear on this: it's the address holder [RFC3972], the sender [RFC3971], or the mobile node [RFC4866].

4) Sec 2: States:

In many cases, a CGA address is generated by the
associated key pair owner, which normally is also the host that will
use the CGA address

Actually, isn't this done in all cases except for the case suggested by this document.

5) Sec 2: States:

However, in a DHCPv6-managed network, hosts
should use IPv6 global addresses only from a DHCPv6 server.

This is confusing to me because I'd define a DHCPv6-managed network where a clients get their addresses from DHCPv6 servers.

6) Sec 2: The last two paragraphs seem to be explaining the rationale for co-existence.  I can see that DHCP might support this, but like Russ indicated I don't see the justification for this change.

7)  Sec 3: States:

  In the current CGA specifications there is a lack of procedures
to enable central management of CGA generation."

Umm, isn't this one of the main points of CGAs?!

8)  Sec 3: States:

  Administrators should be
  able to configure parameters used to generate CGAs...

I think this statement is only true if you've bought the DHCPv6-CGA combination.

9) Sec 4: The second paragraph states:

The receiver can
verify both the CGA and signature, then process the payload of the
DHCPv6 message only if the validation is successful. A CGA option
with an address ownership proof mechanism and a signature option
with a corresponding verification mechanism may be introduced into
DHCPv6 protocol.

Absent of some other configuration data, the receiver isn't going to know anything other than the sender owns the address.

10) Sec 5: The second paragraph compares DCHP with CGA to DHCP, but says nothing DHCP with CGA as compared to just using CGAs.  There's also the throw away part about ACLs that is unexplained.

[Ballot comment]
1) This is a comment meant to educate the editors. The change log is not very useful as written, and since it will be removed on publication, it would not be helpful to modify it now. Typically, a change log discusses the major technical changes that occur between revisions. This can help reviewers, such as the IESG, understand whether certain design discussions have taken place during the life of the document, and what design decisions were made. But the change log here only has information that exposes the timing of the revisions, e.g., after ietf73, and that is not useful.

[Ballot discuss]
This is a wordy discuss, with the goal of explaining the myriad of things I think would need to be discussed before I could even consider approving this for publication. Ultimately, the discuss is about the lack of security considerations that would be needed to assess whether the proposals contained in the document are viable in an Internet environment. To a large degree, these comments mirror those from Tim and Russ.

1) The security considerations section basically says this document has not considered the security implications of the designs proposed here. Well, that's exactly why we have a security considerations section - to include the considerations of the security implications.

This document includes multiple proposals for combining DHCPv6 and CGA; it might be better to write each one as a separate document, since the security implications of each of these proposals differs. The security considerations should discuss the threats associated with each proposal.

Do we need to worry about man-in-the-middle attacks, and if so, how do we mitigate that threat?
Do we need to worry about DoS attacks?
Do we need to worry about  integrity checking? replay?
Do we need to worry about authentication? The document does discuss this by proposing an extenral authentication/authorization mechanism, but using an external certification mechanism to authenticate/authorize CGA generators is itself a proposal that would require its own security considerations. It might be possible to use a specific existing standard, such as IBE, but even that would need to consider security issues of combining the security assumptions of IBE and CGA and DHCPv6. And what about the overhead of having to support CGA plus an authentication/authorization mechanism? I think the real benefit of CGA is not needing an external CA; but if you need an external CA to authenticate/authorize the CGA generator, what have you gained?
2) I question whether disclosure of CGA parameters (apparently described in the document as privacy) is not problematic. If the information is available though the network management interface, what types of precautions must the network management interface provide, and what would be the effect of not providing those protections? Is there a cascading vulnerability issue - if somebody can access the parameters through a network management interface, can they use those parameters to spoof the DHCP server. to give themselves access to the network? What happens if they can change the DHCPv6 CGA parameters via the network management interface? Can they manipulate that to give themselves a back door to byoass the security of other protocols that depend on the CGA?

[Ballot discuss]
This is a good document, even if the actual message is quite short
and simple, and at times the draft struggles a bit to explain its
conclusions clearly. FWIW, I disagree with some of the discusses that
I have seen. I do have a few concerns (one shared with Russ), however:

Section 3 claims without good justification that CGA parameters should
be managed by a central entity. I think a reasonable case can be made
for some parameters (like algorithms, Sec) but maybe not all. I can
see also good reasons why central administration would be a bad idea
(e.g., prefix is a local network matter and comes from the RAs). In any
case, the document is silent about all this.

Section 3 also suggests that with Sec>0 the generation of the hashes
is something that should be centralized. Again, I can see also some
reasons not to. In particular, Sec was not designed as a way to burden
current machines but to enable higher cost searches when machines get
faster. That is, if generating a Sec>0 value is a big burden for our
computers, we should probably still use Sec=0. (I think there is a better
argument than the one used in the draft. A very low-power host might
want to delegate its key and hash generation to a more general purpose
computer.)

Section 4 should expand on what the implications for using CGAs by
DHCPv6 servers. I believe that might actually be useful, as you could
tie different transactions with the same DHCPv6 server together, ensuring
that it is still the same node. But you could not prevent someone
claiming to be a DHCPv6 server.

I agree with other ADs that the draft should handwave less when it
describes the security implications of some new design. The idea of
the draft should be to describe what CGA can bring to DHCP security,
and the security implications cannot be skipped. One example where
you could easily write some more specific analysis is the above issue
on using unauthorized CGAs by DHCPv6 servers and what the security
impacts of that are.

[Ballot discuss]
I am submitting these issues as a discuss position, but please note that I expect to move from Discuss to Abstain
since I have significant issues with the overall direction.  My issues include one "discuss-discuss" and a number
of specific issues.

Discuss-discuss:
The document implies that centrally managed CGAs were envisioned in the original specs ("The current CGA
specifications do not mandate which device generates a CGA address.")  However, I see no evidence in RFC 3972
that centrally generated CGAs were envisioned.  My reading assumes locally generated CGAs.  Is there any
evidence that the wg really thought CGAs would be generated centrally?

Specific Issues:

In my opinion, this document fails to establish that a problem exists. The current DHCPv6-CGA coexistence model
is dismissed without a clear explanation, and the impact of centrally generated key pairs and modifiers on the
security assumptions for protocols that employ CGAs is not explored at all. [sections 1 and 2]

I believe that sections 3 and 4 should be addressed in separate documents, unless the authors believe that DHCPv6
only benefits from centrally managed CGAs.  Putting both concepts in one document is confusing. [global]

Increasing the security of a CGA against a brute force attack while weakening the base security assumptions
may not be a good compromise.  [section 3, glaringly absent from section 5]

The rationale for centrally generated key pairs is very weak, since a node (e.g. a cell phone) can reuse the same
key pair each time it joins a subnet and generates a new CGA.  [section 3]

It is unclear whether the concepts proposed in Section 4 ("What CGA can do for DHCPv6") rely on centrally
managed CGAs or not.  From what I can tell, traditional CGAs might be very useful for DHCPv6 deployments,
but I am unsure about that.

The document states that when DHCPv6 is used to manage CGAs "it does not increase privacy risks".  Relative
to what?  IMHO, centrally generated CGAs have to increase privacy risks in comparison to CGAs generated by the
host itself. [section 5]

As stated in the security consideration, "This work does not include a complete security analysis".  In my opinion,
such an analysis is crucial to determining whether this "problem" should be solved. As alluded to above, that
analysis needs to review the impact on current protocols that use CGAs.  If those protocols assume local
generation, what is the impact of the mechanisms described here? [section 5]

[Ballot comment]
Updating with additional issues I raised in an email to Marcelo.

I am abstaining from this document.  I believe that using CGAs with DHCP will be harmful to the Internet because it defeats one of the two primary purpose for CGAs, namely privacy.

Update follows:

Marcelo,

I am unlikely to change my position.  When doing an analysis it's okay to state that a particular solution can be done but shouldn't be done.  I think DHCPv6+CGA is one of those.

I share Russ' concerns and I think there are a number of other issues with the draft:

1) Sec 2: States:

The public key system associated with the CGA address provides
message origin validation and integrity protection without the need
for negotiation and transportation of key materials.

There's two problems with this statement: 1) There is no public key system with CGAs. It's just one public key, the whole point was there's no PKI (aka public key system).  2) CGAs include the public key so there is a need to transport key material.

3) Sec 2: States:

The current CGA specifications do not mandate which device generates
a CGA address.

I thought the CGA specification was pretty clear on this: it's the address holder [RFC3972], the sender [RFC3971], or the mobile node [RFC4866].

4) Sec 2: States:

In many cases, a CGA address is generated by the
associated key pair owner, which normally is also the host that will
use the CGA address

Actually, isn't this done in all cases except for the case suggested by this document.

5) Sec 2: States:

However, in a DHCPv6-managed network, hosts
should use IPv6 global addresses only from a DHCPv6 server.

This is confusing to me because I'd define a DHCPv6-managed network where a clients get their addresses from DHCPv6 servers.

6) Sec 2: The last two paragraphs seem to be explaining the rationale for co-existence.  I can see that DHCP might support this, but like Russ indicated I don't see the justification for this change.

7)  Sec 3: States:

  In the current CGA specifications there is a lack of procedures
to enable central management of CGA generation."

Umm, isn't this one of the main points of CGAs?!

8)  Sec 3: States:

  Administrators should be
  able to configure parameters used to generate CGAs...

I think this statement is only true if you've bought the DHCPv6-CGA combination.

9) Sec 4: The second paragraph states:

The receiver can
verify both the CGA and signature, then process the payload of the
DHCPv6 message only if the validation is successful. A CGA option
with an address ownership proof mechanism and a signature option
with a corresponding verification mechanism may be introduced into
DHCPv6 protocol.

Absent of some other configuration data, the receiver isn't going to know anything other than the sender owns the address.

10) Sec 5: The second paragraph compares DCHP+CGA to DHCP, but says nothing DHCP+CGA as compared to just using CGAs.  There's also the throw away part about ACLs that is unexplained.

[Ballot comment]
I am abstaining from this document.  I believe that using CGAs with DHCP will be harmful to the Internet because it defeats one of the two primary purpose for CGAs, namely privacy.

[Ballot discuss]
The direction suggested by this document will undermine the privacy
  features associated with host-generated CGAs.  In general, CGAs are
  not used in the same environment as a DHCP server, and I do not see
  a justification for this to change.

  Without providing a reason, this document asserts that local a
  administrator ought to manage CGA generation parameters.  I am
  guessing that the concern is the computation burden, but this is not
  compelling.  Further, RFC 3315 already allows a DHCPv6 server to
  reject a CGA generated with unacceptable parameters.

  This document discusses the use of DHCPv6 to assign certificates to
  CGA address owners.  CGA 'ownership' can already be validated with
  the private key, so the need for a certificate is unclear.

  This document states: "... the generation of the Modifier field of a
  CGA address is computationally intensive."  RFC 3972 seems indicate
  otherwise for most key sizes.  In general, RSA key pair generation is
  not a big concern on modern processors.  It might be a mild concern
  on mobile devices, but some detailed explanation is required.

Document Shepherd Write-up for draft-ietf-csi-dhcpv6-cga-ps-04

  (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 Marcelo Bagnulo who has reviewed
          this version of the document and believes that us ready for
          forwarding to the IESG 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 been discussed and reviewed by the WG and a few
          external reviewers.
          We issued 1 WGLC and nobody objected the publication.

  (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.

  (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.

          No special concerns or issues. The document is an informational
          document describing the problem and the solution space.

  (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?

          The WG was not very energetic on this document. The document
          describes possible applications of CGAs and DHCP interaction
          and when the WG was asked whether there was enough interest to
          work on solutions, the reply was silence. As such, the consensus
          is based on most of the WG being indifferent.

  (1.f)  Has anyone threatened an appeal or otherwise indicated extreme
          discontent?  If so, please summarize 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 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?  If the document
          does not already indicate its intended status at the top of
          the first page, please indicate the intended status here.

          I have verified the ID nits and found no issues.

          No MIB Doctor, media type nor UR type reviews are needed for
          this document.

          The document intended status is informational.

  (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].

          The references are split into normative and informative.
          All normative references are in RFC state. The is no
          downward dependency, since this is an informational document.

  (1.i)  Has the Document Shepherd verified that the document's IANA
          Considerations 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 the Document
          Shepherd conferred with the Responsible Area Director so that
          the IESG can appoint the needed Expert during IESG Evaluation?

          The document has a IANA considerations section, but there is no
          IANA action required. No protocol extensions are required
          No new registry is created.

  (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?

          The document does no contain any section written in a formal
          language.
 
  (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 potential issues in the interaction between
  DHCPv6 and Cryptographically Generated Addresses (CGAs). Firstly, the
  scenario of using CGAs in DHCPv6 environments is discussed. Some
  operations are clarified for the interaction of DHCPv6 servers and
  CGA-associated hosts. We then also discuss how CGAs and DHCPv6 may
  have mutual benefits for each other, including using CGAs in DHCPv6
  operations to enhance its security features and using DHCPv6 to
  provide the CGA generation function.


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

          Nothing special that worth noting. Not a controversial document.

          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?

          The document is an informational problem statement. The WG expressed
          no interest in working in the solutions to the problem though.
          The document had through reviews, including reviews from
          Alberto Garcia Martinez, Tony Cheneau and their comments were addressed.

          Personnel
            Who is the Document Shepherd for this document?  Who is the
            Responsible Area Director?  If the document requires IANA
            experts(s), insert 'The IANA Expert(s) for the registries
            in this document are .'

        Document shepherd: Marcelo Bagnulo
        Area Director: Ralph Droms