Network Reconnaissance in IPv6 Networks
draft-ietf-opsec-ipv6-host-scanning-08

[Ballot comment]
Thanks for your work pulling together a summary of reconnaissance techniques for IPv6.  I think this is a useful document, that will be helpful to operators and security professionals.  I don't have any comments to add that have not already been mentioned.

[Ballot comment]

- general: @Fernando: thank you for writing a document that does
not recommend turning off IPv6:-)

- general: shouldn't you recommend a honeynet approach as another
way of spotting scans when there ought be none? That might fit in
3.5 I guess.

- intro: what evidence is there that the number of hosts per
subnet is likely to stay the same? (And what do you consider an
IPv4 subnet here? a /16 is it? Maybe worth saying.) The density
point still applies though, but good to not assume things that
aren't needed.

- 3.1.1 - I would recommend you check with Christian Huitema
about Windows10 which has some new features related to MAC
addresses. I don't know if there is new IPv6 handling associated
with those changes.

- 3.4.1 s/patters/patterns/

[Ballot comment]
Interesting work, thanks.

On the VMWare ESX example given in Sec. 3.1.1.1, the OUI given for automatically-generated MAC addresses (00:05:59) does not seem correct. In the linked documentation, it is listed as 00:0C:29. In the IEEE OUI list, 00:0C:29 is registered to VMWare but 00:05:59 is registered to some other company.

In Sec. 3.1.1.3 and 3.1.1.4, I wonder if you might want to re-use the terminology from draft-ietf-6man-ipv6-address-generation-privacy in the section headings, in particular to differentiate "Constant" IIDs from "Stable" IIDs. I think this would be better than using "Privacy-Enhanced" as the term "privacy" is now overloaded when it comes to different types of v6 addresses.

I think the tables in 3.1.5 would be a lot more useful if the table captions noted the total number of addresses investigated (N).

In Section 3.5, wouldn't using RFC 4941 addresses count as a mitigation as well (first bullet)?

Sections 5-13 seem like they belong as subsections of an overarching section about "Other Network Reconnaissance Techniques" or some such. It might also help to provide some indication of how resource-intensive these techniques might be relative to each other. There are other application-specific ways of gathering information about active IP addresses that aren't listed here (the example that comes to mind is an attacker standing up a TURN server) but are probably also more trouble than they're worth for most attackers, which is presumably why they are not included in the list.

[Ballot comment]
Just a couple of nits: 

1. If this document obsoletes rfc5157, then it can’t really update it, can it?  You mention it updates and obsoletes 5157 in the Abstract and Introduction.

2. Introduction.  I think you meant:  s/[van-Dijk] describes a technique for leveraging DNS reverse mappings for discovering IPv6 nodes./Section 4 describes a technique for leveraging DNS reverse mappings for discovering IPv6 nodes [van-Dijk]

[Ballot comment]
I echo Barry's "nice document", and would support the changes he suggested.

I did notice what I believe is a repeated "not" in "it is not not only the lowest-order byte".

In this text:

3.4.1.  Remote IPv6 Network Scanners

  Many address scanning tools such as nmap [nmap2012] do not even
  support sweeping an IPv6 address range.
                          ^
does this mean "sweeping an IPv6 address range in a remote IPv6 network"? I think that's implicit from the section title, but what nmap supports is clearer in the corresponding text in the next section:

3.4.2.  Local IPv6 Network Scanners

  There are a variety of publicly-available local IPv6 network
  scanners:

  o  Current versions of nmap [nmap2012] implement this functionality.

[Ballot comment]
Nice document you have here.  Just two really small comments, neither of which needs any response, and both of which you can ignore if you prefer.

An observation: Three times, you say that something is "obvious", and this can come across as condescending -- and can be frustrating to a reader for whom it isn't obvious.  I suggest omitting that, so

- In Section 3.1.1.1, change "Firstly, as it should be obvious from the algorithm described above" to "Firstly, as shown by the algorithm described above".

- In Section 3.1.3.2, change "For obvious reasons, the search space for addresses following" to "The search space for addresses following".

- In Section 3.3, change "Obviously, a number of other network reconnaissance vectors" to "A number of other network reconnaissance vectors".

-- Section 3.1.1.1 --

An observation, for which the response is probably "everyone knows this, so no change is needed," but please think about it for a fleeting moment:

  1.  The "Universal" bit (bit 6, from left to right) of the address is
      set to 1

Bit 6, starting from 0, or from 1?  The answer (which I can see from the example) is "starting from 0."

  Firstly, as it should be obvious from the algorithm described above,
  two bytes (bytes 4-5) of the resulting address always have a fixed
  value (0xff, 0xfe)

Bytes 4-5, starting from 0 or from 1?  The answer (which I can see from the example) is "starting from 1."

The fact that the origins differ makes me think that it'd be nice if that were made clear.  Please give it a thought, to say that bits are numbered from left to right starting at 0, and bytes are numbered from left to right starting at 1.

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

IANA has reviewed draft-ietf-opsec-ipv6-host-scanning-07, which is currently in Last Call, and has the following comments:

We understand that, upon approval of this document, there are no IANA Actions that need completion. 

While it is helpful for the IANA Considerations section of the document to remain in place upon publication, if the authors prefer to remove it, IANA doesn't object.

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

The following Last Call announcement was sent out:

From: The IESG
To: IETF-Announce
CC:
Reply-To: ietf@ietf.org
Sender:
Subject: Last Call:  (Network Reconnaissance in IPv6 Networks) to Informational RFC


The IESG has received a request from the Operational Security
Capabilities for IP Network Infrastructure WG (opsec) to consider the
following document:
- 'Network Reconnaissance in IPv6 Networks'
  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
ietf@ietf.org mailing lists by 2015-07-08. 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


  IPv6 offers a much larger address space than that of its IPv4
  counterpart.  An IPv6 subnet of size /64 can (in theory) accommodate
  approximately 1.844 * 10^19 hosts, thus resulting in a much lower
  host density (#hosts/#addresses) than is typical in IPv4 networks,
  where a site typically has 65,000 or less unique addresses.  As a
  result, it is widely assumed that it would take a tremendous effort
  to perform address scanning attacks against IPv6 networks, and
  therefore brute-force IPv6 address scanning attacks have been
  considered unfeasible.  This document updates RFC 5157, which first
  discussed this assumption, by providing further analysis on how
  traditional address scanning techniques apply to IPv6 networks, and
  exploring some additional techniques that can be employed for IPv6
  network reconnaissance.  In doing so, this document formally
  obsoletes RFC 5157.




The file can be obtained via
https://datatracker.ietf.org/doc/draft-ietf-opsec-ipv6-host-scanning/

IESG discussion can be tracked via
https://datatracker.ietf.org/doc/draft-ietf-opsec-ipv6-host-scanning/ballot/


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

As required by RFC 4858, this is the current template for the Document
Shepherd Write-Up.

Changes are expected over time. This version is dated 24 February 2012.

(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?

<>Shepherd comment<>
Informational
<>/Shepherd comment<>

(2) The IESG approval announcement includes a Document Announcement
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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.

<>Shepherd comment<>
IPv6 offers a much larger address space than that of its IPv4 counterpart.  An IPv6 subnet of size /64 can (in theory) accommodate approximately 1.844 * 10^19 hosts, thus resulting in a much lower host density (#hosts/#addresses) than is typical in IPv4 networks, where a site typically has 65,000 or less unique addresses.  As a result, it is widely assumed that it would take a tremendous effort to perform address scanning attacks against IPv6 networks, and therefore brute-force IPv6 address scanning attacks have been considered unfeasible.  This document updates RFC 5157, which first discussed this assumption, by providing further analysis on how traditional address scanning techniques apply to IPv6 networks, and exploring some additional techniques that can be employed for IPv6 network reconnaissance.  In doing so, this document formally obsoletes RFC 5157.
<>/Shepherd comment<>

Working Group Summary

  Was there anything in WG process that is worth noting? For
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  were there decisions where the consensus was particularly
  rough?

<>Shepherd comment<>
No controversy. Document went pretty smooth in the WG
<>/Shepherd comment<>



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<>Shepherd comment<>
The content is Informational experience and hence require no vendor implementation.
<>/Shepherd comment<>



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<>Shepherd comment<>
Document Shepherd: Gunter Van de Velde
Responsible Area AD: Joel Jaeggli
<>/Shepherd comment<>


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<>Shepherd comment<>
Document Shepherd followed the document through its creation and this document is ready for publication. A final 1 week sanity check was requested on 21 April and WG consensus was voiced on document value to the list.
<>/Shepherd comment<>


(4) Does the document Shepherd have any concerns about the depth or
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<>Shepherd comment<>
Depth and technical details are satisfactory
<>/Shepherd comment<>


(5) Do portions of the document need review from a particular or from
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<>Shepherd comment<>
This document does not need broader review due to the nature of the document.
<>/Shepherd comment<>


(6) Describe any specific concerns or issues that the Document Shepherd
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<>Shepherd comment<>
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<>/Shepherd comment<>


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<>Shepherd comment<>
Fernando Gont: confirmed on list no awareness IPR.
Tim Chown: Confirmed to OPSEC chair through direct email that he is not aware of any IPR
<>/Shepherd comment<>


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<>Shepherd comment<>
No
<>/Shepherd comment<>


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<>Shepherd comment<>
The WG agrees that this is a good document providing fine information.
<>/Shepherd comment<>


(10) Has anyone threatened an appeal or otherwise indicated extreme
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<>Shepherd comment<>
No particular negative emotions were expressed during the creation of this document
<>/Shepherd comment<>


(11) Identify any ID nits the Document Shepherd has found in this
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<>Shepherd comment<>
idnits were checked on 20 April and sent to authors for verification. Fernando commented that all idnits have been fully checked.
<>/Shepherd comment<>


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<>Shepherd comment<>
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<>Shepherd comment<>
Yes
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<>Shepherd comment<>
All Normative references are ready
<>/Shepherd comment<>



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<>Shepherd comment<>
No
<>/Shepherd comment<>


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<>Shepherd comment<>
This document intends to obsolete RFC 5157. This is indicated
<>/Shepherd comment<>


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<>Shepherd comment<>
This document makes no particular IANA considerations
<>/Shepherd comment<>


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<>Shepherd comment<>
IETF idnits tool
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