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Versions: 00 01 02 03 04 05 06 RFC 6744

Internet Draft                                           RJ Atkinson
draft-irtf-rrg-ilnp-noncev6-02.txt                        Consultant
Expires: 16 OCT 2012                                        S Bhatti
Category: Experimental                                 U. St Andrews
                                                      April 16, 2012

                IPv6 Nonce Destination Option for ILNPv6
                   draft-irtf-rrg-ilnp-noncev6-02.txt


Status of this Memo

   Distribution of this memo is unlimited.

   Copyright (c) 2012 IETF Trust and the persons identified as the
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   works of it may not be created, except to publish it as an RFC or
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   Internet-Drafts are working documents of the Internet
   Engineering Task Force (IETF), its areas, and its working
   groups. Note that other groups may also distribute working



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   documents as Internet-Drafts.

   Internet-Drafts are draft documents valid for a maximum of six
   months and may be updated, replaced, or obsoleted by other
   documents at any time. It is inappropriate to use
   Internet-Drafts as reference material or to cite them other
   than as "work in progress."

   The list of current Internet-Drafts can be accessed at
   http://www.ietf.org/1id-abstracts.html

   The list of Internet-Draft Shadow Directories can be accessed at
   http://www.ietf.org/shadow.html

   This document is not on the IETF standards-track and does not
   specify any level of standard.  This document merely provides
   information for the Internet community.

   This document is part of the ILNP document set, which has had
   extensive review within the IRTF Routing Research Group.  ILNP is
   one of the recommendations made by the RG Chairs.  Separately,
   various refereed research papers on ILNP have also been published
   during this decade.  So the ideas contained herein have had much
   broader review than the IRTF Routing RG.  The views in this
   document were considered controversial by the Routing RG, but the
   RG reached a consensus that the document still should be
   published.  The Routing RG has had remarkably little consensus on
   anything, so virtually all Routing RG outputs are considered
   controversial.

Abstract

   The Identifier-Locator Network Protocol (ILNP) is an
   experimental, evolutionary enhancement to IP.  ILNP has multiple
   instantiations.  This document describes an experimental Nonce
   Destination Option used only with ILNP for IPv6 (ILNPv6).  This
   document is a product of the IRTF Routing RG.

Table of Contents

   1. Introduction ...............................................2
   2. Syntax......................................................3
   3. Transport Protocol Effects..................................5
   4. Location Changes............................................5
   5. Implementation Considerations...............................6
   6. Backwards Compatibility.....................................6
   7. Security Considerations ....................................8
   8. IANA Considerations ........................................9



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   9. References .................................................9


1. Introduction

   This document describes a new option for the IPv6 Destination
   Options header that is used with the Identifier Locator Network
   Protocol for IPv6 (ILNPv6).  ILNPv6 is an experimental protocol
   that is backwards compatible with, and incrementally upgradable
   from, IPv6.  This option is ONLY used in ILNPv6 sessions and is
   never used with classic IPv6 sessions.

   The Nonce option for the IPv6 Destination Options Header that is
   described in this document provides two functions.  First, it
   provides protection against off-path attacks for packets when
   ILNPv6 is in use.  Second, it provides a signal during initial IP
   session creation that ILNPv6 is proposed for use with this
   session, rather than classic IPv6.  This last function is
   particularly important for ensuring that ILNP is both
   incrementally deployable and backwards compatible with IPv6.
   Consequently, this option MUST NOT be used except by an
   ILNPv6-capable node.

   Further, each Nonce value is unidirectional.  Since packets often
   travel asymmetric paths between two correspondents, having
   separate Nonces for each direction limits the number of on-path
   nodes that can easily learn a session's nonce.  So a typical TCP
   session will have 2 different nonce values in use: one nonce is
   used from Local Node to the Correspondent Node and a different
   nonce is used from the Correspondent Node to the Local Node.

1.1  ILNP Document Roadmap

   The Identifier-Locator Network Protocol (ILNP), is described in
   the ILNP Architecture [ILNP-ARCH] document, which should be read
   first.  ILNP can have multiple instantiations.  [ILNP-ENG]
   discusses engineering and implementation aspects common to all
   ILNP instantiations.  [ILNP-DNS] defines new Domain Name System
   (DNS) resource records for ILNP.  [ILNP-ICMPv6] defines a new
   ICMPv6 Locator Update message for use with ILNPv6.  Other
   documents describe ILNP for IPv4 (ILNPv4).

1.2 Terminology

   The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL
   NOT", "SHOULD", "SHOULD NOT", "RECOMMENDED", "MAY", and
   "OPTIONAL" in this document are to be interpreted as described
   in RFC 2119. [RFC2119]



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2. Syntax

   The Nonce Option is carried within an IPv6 Destination Option
   Header.  Section 4 of [RFC2460] provides much more information
   on the various options and optional headers used with IPv6.

   More than one option might be inside the IPv6 Destination Option
   Header, however at most 1 Nonce Option exists in a given IPv6
   packet.

   A system that receives a packet containing more than one Nonce
   option SHOULD discard the packet as "Authentication Failed"
   (instead of passing the packet up to the appropriate
   transport-layer protocol or to ICMP) and SHOULD log the event,
   including the Source Locator, Source Identifier, Destination
   Locator, Destination Identifier, upper-layer protocol (e.g. OSPF,
   TCP, UDP) if any, and transport-layer port numbers (if any),
   as a security fault in accordance with local logging policies.

   As of this writing, IPv6 Destination Option Headers, and the
   options carried by such headers, are extremely uncommon in the
   deployed Internet.  So, it is expected that this Nonce Option
   commonly would be the only IPv6 Destination Option present in a
   given IPv6 packet.  If a CALIPSO label option [RFC5570] is also
   present in the same IPv6 Destination Option Header, the CALIPSO
   option SHOULD precede the Nonce option. The Nonce option SHOULD
   precede other possible options in the same IPv6 Destination
   Option Header.

   In the diagram below, we show not only the Nonce Option, but also
   the IPv6 Destination Option Header that carries the Nonce Option.

   ------------------------------------------------------------
   | Next Header | Hdr Ext Len   | Option Type | Option Length|
   +-------------+---------------+-------------+--------------+
   /                        Nonce Value                       /
   +-------------+---------------+-------------+--------------+


   Next Header:       8-bit selector.  Identifies the type of header
                      immediately following the Destination Options
                      header.  Uses the same values as the IPv4
                      Protocol field [RFC2460].

   Hdr Ext Len:       8-bit unsigned integer.  Length of the
                      Destination Options header in 8-octet units,
                      not including the first 8 octets.




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   Option Type:       This contains the value XXX, which is used
                      to indicate the start of the Nonce Option.

   Option Length:     This indicates the length in 8-bit octets of
                      the Nonce Value field of the Nonce Option.
                      This value must be selected so that the
                      enveloping IPv6 Destination Option complies
                      with the IPv6 header alignment rules.  Common
                      values are 4 (when the Nonce Value is
                      32-bits), and 12 (when the Nonce value is
                      96-bits).

   Nonce Value:       An unpredictable cryptographically random value
                      used to prevent off-path attacks on an ILNP
                      session [RFC4086]. This field has variable
                      length, with the length indicated by the
                      Option Length field preceding it.  Note that
                      the overall IPv6 IPv6 Destination Option MUST
                      comply with IPv6 header alignment rules.
                      Implementations MUST support sending and
                      receiving 32-bit and 96-bit Nonce values.

3.  Transport Protocol Effects

   When the initial packet(s) of an IPv6 session contain this Nonce
   Destination Option, then ILNPv6 is in use for that communications
   session.  (NOTE: Backwards compatibility and incremental
   deployment are discussed in more detail in Section 6 below.)

   When a communications session is using ILNPv6, then the
   transport-layer pseudo-header calculations MUST set to zero the
   high-order 64-bits ("Locator" or "Routing Prefix") of each IPv6
   address.  This has the effect that the transport-layer is no
   longer aware of the topological network location of either node
   in the session.

   The preceding rule applies not only to unicast sessions, but also
   to multicast or anycast sessions that use ILNPv6.

4.  Location Changes

   When a node has a change in its Locator set that causes all
   previously valid Locators to become invalid, the node MUST send
   an ICMP Locator Update message (containing the Nonce Option with
   the appropriate nonce value) to each of its correspondents
   []ILNP-ARCH] [ILNP-ICMPv6].

   In the deployed Internet, packets sometimes arrive at a



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   destination out of order.  A receiving node MUST drop a packet
   arriving from a correspondent if the Source Locator of the
   received packet is not in the receiving node's Identifier Locator
   Communication Cache's (ILCC's) Set of Correspondent Locator(s)
   UNLESS that packet contains a Nonce Option with the appropriate
   nonce value for that Source Identifier and Destination Identifier
   pair. This is done to reduce the risk of session hijacking or
   session interference attacks.

   Hence, the node that has had all previously valid Locators become
   invalid MUST include the Nonce Option with the appropriate nonce
   value in all packets (data or otherwise) to all correspondents
   for at least 3 round-trip times for each correspondent.  (NB: An
   implementation need not actually calculate RTT values; it could
   just use a fixed timer with a time long enough to cover the
   longest RTT path, such as 1 minute.) This 'gratuitous
   authentication' ensures that the correspondent can authenticate
   any received packet, even if the ICMP Locator Update control
   message arrives and is processed AFTER some other packet using
   the new Source Locator(s).  If a session is using IP Security,
   then, of course, IP Security SHOULD continue to be used.  Because
   IP Security for ILNP [ILNP-ENG] binds only to the Identifiers,
   and not to the Locators in the packet, changes in Locator value
   have no impact on IP Security for ILNP sessions.

   As mobility and multi-homing are functionally equivalent for
   ILNP, this section applies equally to either situation, and also
   to any other situation in which a node's set of Locators might
   change over time.

5.  Implementation Considerations

   Implementers may use any internal implementation they wish,
   PROVIDED that the externally visible behaviour is the same as
   this implementation approach.

5.1  ILNP Communication Cache

   As described in [ILNP-ENG], ILNP nodes maintain an Identifier-Locator
   Communication Cache (ILCC) that contains several variables for
   each correspondent.  The ILNP Nonce value is an important part of
   that cache.

5.2 Mode Indicator

   To support ILNP, and to retain needed incremental deployability
   and backwards compatibility, the network layer needs a (logical)
   mode bit in the Transport Control Block (or equivalent for one's



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   implementation) to track which IP sessions are using traditional
   IPv6 and which IP sessions are using ILNPv6.

   If a given transport-layer session is using ILNP, then an entry
   corresponding to that session also will exist in the ILNP
   Communication Cache.  Multiple transport-layer sessions between a
   given pair of nodes MAY share a single entry in the ILNP
   Communication Cache if they are identical other than in the
   details above the network-layer.

5.3  IP Security

   Whether or not ILNP is in use, the IPsec subsystem MUST maintain
   an IPsec Security Association Database (SAD) and also MUST
   maintain information about which IPsec Selectors apply to traffic
   received by or sent from the local node [RFC4301]. By combining
   the information in the IPsec SAD, of what IPsec Selectors apply,
   and information in the ILCC, an implementation has sufficient
   knowledge to apply IPsec properly to both received and
   transmitted packets.

6.  Backwards Compatibility

   This option MUST NOT be present in an IPv6 packet unless the
   packet is part of an ILNPv6 session.  As is explained below in
   more detail, the presence or absence of this option from the
   initial packets of a new IPv6 session is an important indication
   of whether the session is using classic IPv6 or ILNPv6.

   ILNPv6 nodes MUST include this option in the first few packets
   of each ILNPv6 session, MUST include this option in all ICMP
   messages generated by endpoints participating in an ILNPv6
   session, and MAY include this option in any and all packets of an
   ILNPv6 session.  It is recommended that this option be included
   in all packets of the ILNPv6 session if the packet loss for that
   session is known to be much higher than normal.

   If a node supports ILNP and the node wishes to be able to receive
   incoming new ILNP sessions, then that node's fully-qualified
   domain name SHOULD have one or more ID records and also one or
   more Locator (i.e. L64 or LP) records associated with it in the
   DNS.

   When a host ("initiator") initiates a new IP session with a
   correspondent ("responder"), it normally will perform a DNS
   lookup to determine the address(es) of the responder.  A host
   that has been enhanced to support the Identifier/Locator Split
   operating mode SHOULD look for Identifier ("ID") and Locator



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   ("L64") records in any received DNS replies.  DNS servers that
   support Identifier and Locator (i.e., L64 or LP) records SHOULD
   include them (when they exist) as additional data in all DNS
   replies to DNS queries for DNS A or AAAA records associated with
   a specified DNS Fully-Qualified Domain Name (FQDN).

   If the initiator supports ILNP, and from DNS data learns that the
   responder also supports ILNP, then the initiator SHOULD attempt
   to use ILNP for new sessions with that responder.  In such cases,
   the initiator MUST generate an unpredictable nonce value, MUST
   store that value in the local ILCC, and MUST include the ILNP
   Nonce Destination Option in its initial packet(s) to the
   responder. The IETF has provided advice on generating
   cryptographically random numbers, such as this nonce value
   [RFC4086].

   If the responder supports ILNP and receives initial packet(s)
   containing the ILNP Nonce Destination Option, the responder will
   thereby learn that the initiator supports ILNP and the responder
   also will use ILNP for this new IP session.

   If the responder supports ILNP and receives initial IP packet(s)
   NOT containing the Nonce Destination Option, the responder will
   thereby learn that the initiator does NOT support ILNP and the
   responder will use classic IPv6 for this new IP session.

   If the responder does not support ILNP and receives initial
   packet(s) containing the ILNP Nonce Destination Option, the
   responder MUST drop the packet and MUST send an ICMP "Parameter
   Problem" error message back to the initiator [RFC4443]. Indeed,
   it is not expected that this behaviour will need to be coded into
   non-ILNP nodes, as this is the normal behaviour for nodes
   receiving unknown option headers.

   If the initiator EITHER does not receive a response from the
   responder in a timely manner (e.g. within the applicable TCP
   timeout for a TCP session), and also does not receive an ICMP
   Unreachable error message for that packet, OR if the initiator
   receives an ICMP Parameter Problem error message for that packet,
   then the initiator infers that the responder is not able to
   support ILNP.  In this case, the initiator should try again to
   create the new IP session, but this time use classic IPv6 and
   hence MUST NOT include the ILNP Nonce Destination Option.

7. Security Considerations

   The ILNPv6 Nonce Destination Option is used ONLY for ILNPv6
   sessions, because this option is part of the backwards-



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   compatibility and incremental-deployment approach for the
   Identifier-Locator Network Protocol (ILNP).  This option
   MUST NOT be used with classic IPv6 sessions.

   The ILNPv6 Nonce Destination Option only seeks to provide
   protection against off-path attacks on an IP session.  Ordinary
   IPv6 is vulnerable to on-path attacks unless IP Security is in
   use [CA-1995-01] [RFC4301]. This option exists to provide non-
   cryptographic protection for ILNP sessions, protection equivalent
   to the security of IP sessions that do NOT use IPsec.

   When ILNPv6 is in use for a communications session, the ILNP
   Nonce Destination Option MUST be included in any ICMP control
   messages (e.g. ICMP Unreachable, ICMP Locator Update) sent by
   participants in that ILNPv6 session, even if IP Security also is
   in use for that session.  Note that certain ICMP messages, for
   example a "Path Too Big" message, might be generated by transit
   devices that are not aware of the ILNP Nonce in use for that
   session and hence are not able to include the ILNP Nonce. Again,
   this also is true of classic IPv6 in the same operational
   situations, so this does not create a new security issue.

   For ILNPv6 sessions, any ICMP control messages received from a
   participant in that ILNPv6 session that lack a Nonce Destination
   Option MUST be discarded as forgeries.  This security event
   SHOULD be logged in accordance with local security logging
   policies, including details of the received packet (i.e. Source
   Locator, Source Identifier, Destination Locator, Destination
   Identifier, upper-layer protocol (e.g. TCP, UDP, OSPF) if any,
   transport-layer port numbers if any, and the date and time the
   packet was received).

   For ILNPv6 sessions, ICMP control messages received from a
   participant in that ILNPv6 session that have a Nonce Destination
   Option, but do NOT have the correct nonce value inside the Nonce
   Destination Option, MUST be discarded as forgeries.  This
   security event SHOULD be logged as described above.

   Of course, longer nonce values provide greater resistance to
   random guessing of the nonce value.  However, ILNPv6 sessions
   operating in higher risk environments SHOULD also use the
   cryptographic authentication provided by IP Security for ILNP
   [ILNP-ENG] [RFC4301]. Use of IP Security for ILNP for an ILNPv6
   session does not eliminate the need for the ILNPv6 Nonce Option
   to be included as described here or as described in [ILNP-
   ICMPv6].

   As a performance optimisation, it is suggested that when both the



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   Nonce Option and IP Security are present in a packet and the
   Nonce Option has not been encrypted, that the Nonce Option value
   be checked for validity before beginning IP Security processing.
   This minimises the ability of an off-path attacker to force the
   recipient to perform expensive cryptographic computations on
   received control packets.

   For environments with data at differing Sensitivity Levels
   operating over common infrastructure (e.g. when the IPv6 CALIPSO
   is deployed), it is recommended that the Nonce Option be
   encrypted by using ESP Transport-Mode or ESP Tunnel-Mode in order
   to reduce the covert channel bandwidth potential created by the
   Nonce Option, and to prevent a node at one sensitivity level from
   attacking a session at a different sensitivity level [RFC5570].
   Further, multi-level secure systems SHOULD use different nonce
   values for sessions with different Sensitivity Levels [RFC5570].
   When the Nonce option and the CALIPSO option are present in the
   same IPv6 Destination Options Header, the CALIPSO option SHOULD
   appear before the Nonce option.

   In all cases, the Nonce Value MUST be unpredictable and
   cryptographically random.  [RFC4086] provides concrete advice on
   how to generate a suitable nonce value.

   As this is an option within the IPv6 Destination Option Header,
   rather than an option within the IPv6 Hop-by-Hop Option Header,
   the presence of this option in an IPv6 packet ought not disturb
   routers along the path an IP packet containing this option
   happens to travel.  Further, many deployed modern IP routers
   (both IPv4 and IPv6) have been explicitly configured to ignore
   all IP options, even including the "Router Alert" option, when
   forwarding packets not addressed to the router itself.  Reports
   indicate this has been done to preclude use of IP options as a
   (Distributed) Denial-of-Service (D)DOS attack vector on backbone
   routers.

   As the Nonce is used in the checksum of all AH protected packets,
   as an implementation hint, it would seem sensible to include the
   Nonce value from the ILCC for that session.


8. IANA Considerations

   Subject to IESG Approval, and consistent with the procedures of
   [RFC2780], IANA is requested to assign a new IPv6 Destination
   Option Type value (replacing XXX, in Section 2 above).

   The Nonce Option MUST NOT change in transit and MUST be included



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   in IP Authentication Header calculations.

   Further, if an end system receives a packet containing this
   option, but does not recognise the option, the end system MUST
   drop the received packet.

9.  References

9.1.  Normative References

   [ILNP-ARCH]  R. Atkinson and S. Bhatti, "ILNP Architecture",
                draft-irtf-rrg-ilnp-arch, January 2012.

   [ILNP-ENG]   R. Atkinson and S. Bhatti, "ILNP Engineering
                and Implementation Considerations",
                draft-irtf-rrg-ilnp-eng, January 2012.

   [ILNP-DNS]   R. Atkinson and S. Bhatti,  "DNS Resource Records
                for ILNP", draft-irtf-rrg-ilnp-dns, January 2012.

   [ILNP-ICMPv6]  R. Atkinson & S. Bhatti, "ICMP Locator Update
                message for ILNPv6", draft-irtf-rrg-ilnp-icmpv6,
                January 2012.

   [RFC2119]  Bradner, S., "Key words for use in RFCs to
               Indicate Requirement Levels", BCP 14, RFC 2119,
               March 1997.

   [RFC2460]  S. Deering & R. Hinden, "Internet Protocol
               Version 6 Specification", RFC 2460,
               December 1998.

   [RFC4301]  S. Kent & K. Seo, "Security Architecture for
               the Internet Protocol", RFC 4301, December 2005.

   [RFC4443] A. Conta, S. Deering, M.  Gupta, Ed.,
           "Internet Control Message Protocol (ICMPv6)
           for IPv6 Specification", RFC 4443, March 2006.

9.2.  Informative References

   [CA-1995-01]  US CERT, "CERT Advisory 1995-01", Pittsburgh,
                 PA, USA, 1995.

   [RFC4086]    D. Eastlake 3rd, J. Schiller, & S. Crocker,
                 "Randomness Requirements for Security",
                 RFC 4086, June 2005.




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   [RFC5570]    M. StJohns, R. Atkinson, and G. Thomas, "Common
              Architecture Label IPv6 Security Option (CALIPSO)",
              RFC 5570, July 2009.

ACKNOWLEDGEMENTS

   Steve Blake, Stephane Bortzmeyer, Mohamed Boucadair, Noel
   Chiappa, Wes George, Steve Hailes, Joel Halpern, Mark Handley,
   Volker Hilt, Paul Jakma, Dae-Young Kim, Tony Li, Yakov Rehkter,
   Bruce Simpson, Robin Whittle and John Wroclawski (in alphabetical
   order) provided review and feedback on earlier versions of this
   document. Steve Blake provided an especially thorough review of
   an early version of the entire ILNP document set, which was
   extremely helpful. We also wish to thank the anonymous reviewers
   of the various ILNP papers for their feedback.

RFC EDITOR NOTE

   This section is to be removed prior to publication.

   This document is written in English, not American.  So English
   spelling is used throughout, rather than American spelling.
   This is consistent with existing practice in several other RFCs,
   for example RFC-5887.

   This document tries to be very careful with history, in the
   interest of correctly crediting ideas to their earliest
   identifiable author(s).  So in several places the first published
   RFC about a topic is cited rather than the most recent published
   RFC about that topic.

Authors' Addresses:

   RJ Atkinson
   Consultant
   San Jose, CA
   95125 USA

   rja.lists@gmail.com

   SN Bhatti
   School of Computer Science
   University of St Andrews
   North Haugh, St Andrews
   Fife, Scotland, UK
   KY16 9SX

   Expires: 16 OCT 2012



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