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Internet Draft                                           RJ Atkinson
draft-rja-ilnp-nonce-11.txt                               Consultant
Expires: 27 JAN 2012                                    27 July 2011
Category: Experimental

                     ILNP Nonce Destination Option
                      draft-rja-ilnp-nonce-11.txt


Status of this Memo

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   Internet-Drafts are working documents of the Internet
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   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 has had extensive review within the IRTF Routing
   Research Group, and is part of the ILNP document set.  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

   This document describes an experimental Nonce Destination Option
   that is part of the Identifier-Locator Network Protocol (ILNP).
   This option is used with the ILNP variant that is based upon
   IPv6.  This 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
   9. References .................................................9





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1. Introduction

   Some in the research and development community are examining
   different approaches to evolving the Internet Architecture.
   Several different classes of evolution are being considered.
   One class is often called "Map and Encapsulate", where traffic
   would be mapped and then tunnelled through the inter-domain
   core of the Internet.  Another class being considered is
   sometimes known as "Identifier/Locator Split".[GSE] [8+8]

   This document is part of a proposal that is in the latter class
   of evolutionary approaches.  This particular approach, the
   Identifier-Locator Network Protocol (ILNP), described in this
   document and in related Internet-Drafts, is based upon IPv6.
   [ILNP-Intro] [ILNP-DNS] [ILNP-ICMP] [RFC 2460]

   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 an
   Identifier/Locator split is in use.  Second, it provides a
   signal during initial IP session creation that the Identifier/
   Locator Split operating mode is proposed for use with this
   session.  This last function is particularly important for
   ensuring that the new Identifier/Locator Split operating mode is
   both incrementally deployable and backwards compatible with IPv6.
   Consequently, this option must not be used except by a node
   operating in the I/L Split (ILNP) mode.

   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.

   Before reading this draft, readers should read the related
   Internet-Draft titled "ILNP Concept of Operations", as that
   document will help the reader understand the overall context
   for this option.[ILNP-Intro]

1.1 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. [RFC 2119]



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2. Syntax

   The Nonce Option is carried within an IPv6 Destination Option
   Header.  Section 4 of [RFC 2460] provides much more information
   on the various options and optional headers used with IPv6.  Note
   well that the IP Authentication Header is neither an IPv6
   Destination Option nor an IPv6 Hop-by-Hop Option because it is
   instead its own header type.[RFC 4302]

   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 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.

   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 [RFC 1700 et seq.].

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

   Option Type:       This contains the value XXX, which is used



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                      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. [RFC 4086]
                      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, the Identifier/Locator Split operating mode
   is in use for that IP session.

   When an IPv6 session is in the Identifier/Locator Split operating
   mode, the transport-layer pseudo-header calculations 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 when the Identifier/Locator
   Split operating mode is in use.

4.  Location Changes

   When a node has an unexpected 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.

   In the deployed Internet, packets sometimes arrive at a
   destination out of order.  A receiving node MUST drop a packet



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   arriving from a correspondent if the Source Locator of the
   received packet is not in the receiving node's ILNP Correspondent
   Cache'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 unexpectedly 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
   in this case.  Because IP Security for ILNP binds only to the
   Identifiers, and not to the Locators in the packet, changes in
   Locator value have no impact on IP Security sessions.

   As mobility and multi-homing are functionally equivalent,
   this section applies equally to either situation.

5.  Implementation Considerations

   Implementers may use any internal implementation they wish,
   provided that the external appearance is the same as this
   implementation approach.

5.1  ILNP Correspondent Cache

   When in the Identifier/Locator Split mode, nodes maintain an
   ILNP Correspondent Cache containing several variables for each
   correspondent.  This cache is described in more detail in
   [ILNP-Intro].  The ILNP Nonce value is an important part of
   that cache.

5.2 Mode Indicator

   To support the Identifier/Locator Split operating mode, and
   retain the incremental deployability and backwards compatibility
   needed, the network layer needs a mode bit in the Transport
   Control Block (or equivalent for one's implementation) to track
   which IP sessions are using the classic IPv6 mode, and which IP



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   sessions are using the Identifier/Locator Split mode.

   If a given transport-layer session is in the I/L Split Mode,
   then an entry corresponding to that session will exist in the
   ILNP Correspondent Cache.  Note that multiple transport-layer
   sessions between a given pair of nodes normally share a single
   entry in the Correspondent Cache.

5.3  IP Security

   Whether or not the I/L-Split Mode is in use, the IPsec subsystem
   is required to maintain an IPsec Security Association Database
   (SAD) and also information about which IPsec Selectors apply
   to traffic received by or sent from the local node. [RFC 4301]
   By combining the information in the IPsec SAD, of what IPsec
   Selectors apply, and the ILNP Correspondent Cache, an
   implementation has sufficient knowledge to apply IPsec
   properly to both received and transmitted packets.

6.  Backwards Compatibility

   If a node has been enhanced to support the Identifier/Locator
   Split operating mode, 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 normally will look for Identifier ("ID") and
   Locator ("L64") records in any received DNS replies.  DNS servers
   that support ID and Locator (i.e., L64 or LP) records SHOULD
   include them (when they exist) as additional data in all DNS
   replies to queries for DNS AAAA records.

   If the initiator supports the I/L Split mode and from DNS data
   learns that the responder also supports the I/L Split mode, then
   the initiator MUST generate an unpredictable nonce value, MUST
   store that value in the local correspondent cache, and MUST
   include the 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.
   [RFC 4086]

   If the responder supports the I/L Split mode and receives initial
   packet(s) containing the Nonce Destination Option, the responder
   will thereby learn that the initiator supports the I/L Split mode



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   and the responder will also operate in I/L Split mode for this
   new IP session.

   If the responder supports the I/L Split mode and receives initial
   packet(s) NOT containing the Nonce Destination Option, the
   responder will thereby learn that the initiator does NOT support
   the I/L Split mode and the responder will operate in classic IPv6
   mode for this new IP session.

   If the responder does not support the I/L Split mode and receives
   initial packet(s) containing the Nonce Destination Option, the
   responder MUST drop the packet and MUST send an ICMP "Parameter
   Problem" error message back to the initiator.[RFC 4443]

   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 the I/L Split Operating mode.
   In this case, the initiator should try again to create the
   new IP session, but this time use classic IPv6 mode and
   hence MUST NOT include the Nonce Destination Option.

7. Security Considerations

   The Nonce Destination Option is used ONLY for IPv6 sessions using
   Identifier/Locator split mode, because this option is part of the
   backwards-compatibility and incremental-deployment approach for
   the Identifier-Locator Network Protocol (ILNP).

   The 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 the IP Authentication Header
   or IP Encapsulating Security Payload are in use.  This option
   exists to provide equivalent protection for non-IPsec traffic
   when the Identifier/Locator Split mode is in use for an IP
   session.

   When the Identifier/Locator (I/L) split mode is in use for an
   existing IP session, the Nonce Destination Option MUST be
   included in any ICMP control messages (e.g. ICMP Unreachable,
   ICMP Locator Update) sent with regard to that ILNPv6 session,
   even if IP Security is also in use for that session.

   When in the I/L Split operating mode for an existing IPv6
   session, any ICMP control messages received without a Nonce



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   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).

   When in the I/L Split operating mode for an existing IPv6
   session, ICMP control messages received without a 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, ID/Locator Split
   mode sessions operating in higher risk environments should use
   the cryptographic authentication provided by IP Authentication
   Header.  Note that the Nonce Option MUST be present -- even if
   the IP Authentication Header is in use for a given session.

   As a performance optimisation, it is suggested that when both the
   Nonce Option and IP Security are present in a packet, and the
   Nonce Option has not been encrypted (e.g. ESP is not in use),
   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 receipient 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 is
   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.[RFC 5570]
   It is further recommended that multi-level secure systems use
   different nonce values for sessions with different Sensitivity
   Levels.[RFC 5570]

   In all cases, the Nonce Value MUST be unpredictable and
   cryptographically random.  RFC 4086 provides concrete advice
   on how to generate a suitable nonce value.[RFC 4086]

   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



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   happens to travel.  Further, many 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.

8. IANA Considerations

   IANA is requested to assign a new Destination Option Type value
   (replacing XXX, in Section 2 above).

   The Nonce Option MUST NOT change in transit and MUST
   be included 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 drops
   the received packet and if and only if the Destination Address
   was NOT an IPv6 multicast address the receiving end system sends
   an ICMP Parameter Problem, Code 2, message to the packet's Source
   Address, pointing to the unrecognised Option Type.


9.  References

9.1.  Normative References

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

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

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

   [RFC 4302] S. Kent, "IP Authentication Header", RFC 4302,
              December 2005.

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

9.2.  Informative References




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   [8+8]        M. O'Dell, "8+8 - An Alternate Addressing
                Architecture for IPv6", Internet-Draft,
                October 1996.

   [GSE]        M. O'Dell, "GSE - An Alternate Addressing
                Architecture for IPv6", Internet-Draft,
                February 1997.

   [ILNP-Intro]  Atkinson, R, "ILNP Concept of Operations",
                 draft-rja-ilnp-intro-10.txt, February 2011.

   [ILNP-DNS]    Atkinson, R, "DNS Resource Records for
                 ILNP", draft-rja-ilnp-dns-10.txt, February 2011.

   [ILNP-ICMP]   Atkinson, R, "ICMP Locator Update message"
                 draft-rja-ilnp-icmp-10.txt, February 2011.

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

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

ACKNOWLEDGEMENTS

   Steve Blake, Saleem Bhatti, Noel Chiappa, Steve Hailes, Joel
   Halpern, Mark Handley, Volker Hilt, Tony Li, and Yakov Rehkter
   (in alphabetical order) provided review and feedback on earlier
   versions of this document.  Steve Blake provided an especially
   thorough review of the entire ILNP document set, which led to
   significant improvements in this document.

Author's Address:

   RJ Atkinson
   Consultant
   McLean, VA
   22102 USA

   rja.lists@gmail.com

   Expires: 27 JAN 2012







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