Internet Draft R. Atkinson
draft-rja-ilnp-nonce-01.txt Extreme Networks
Expires: 10 June 2009 10 December 2008
Category: Experimental
Nonce Destination Option
draft-rja-ilnp-nonce-01.txt
Status of this Memo
Distribution of this memo is unlimited.
By submitting this Internet-Draft, each author represents
that any applicable patent or other IPR claims of which he
or she is aware have been or will be disclosed, and any of
which he or she becomes aware will be disclosed, in
accordance with Section 6 of BCP 79.
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
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 a contribution to the IRTF Routing
Research Group. It is neither a contribution to the IETF,
nor to any IETF Working Group, nor to any IETF Area.
Abstract
This document describes an experimental Nonce Destination
Option that could be used as part of an Identifier Locator
Network Protocol (ILNP) that is based upon IPv6.
Atkinson Expires in 6 Months [Page 1]
Internet Draft ILNP Nonce 10 DEC 2009
Table of Contents
1. Introduction ...............................................2
2. Syntax......................................................3
3. Transport Protocol Effects..................................4
4. Location Changes............................................4
5. Implementation Considerations...............................5
6. Backwards Compatibility.....................................6
7. Security Considerations ....................................8
8. IANA Considerations ........................................9
9. References .................................................9
1. Introduction
At present, the IRTF Routing Research Group is studying several
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 relates to a
proposal that is in the latter class of evoluationary approaches.
This particular approach, the Identifier Locator Network Protocol
(ILNP), described in this document and in related Internet-Drafts,
is a possible evolutionary direction for IPv6.[ILNP-Intro]
[ILNP-DNS][ILNP-ICMP][RFC-2460]
The Nonce Destination Option 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 classical IPv6.
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
Atkinson Expires in 6 Months [Page 2]
Internet Draft ILNP Nonce 10 DEC 2009
Internet-Draft titled "ILNP Concept of Operations", as that document
will help the reader understand the overall context for this option.
2. Syntax
The Nonce Option is an IPv6 Destination Option.
In the diagram below, we show not only the Nonce Option,
but also the 2-byte header for the IPv6 Destination Option.
More than one option might be inside the IPv6 Destination Option,
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).
As of this writing, IPv6 Destination Options are extremely
uncommon in the deployed Internet. So, it is expected that
most commonly Nonce Option would be the only IPv6 Destination
Option present in a given IPv6 packet.
------------------------------------------------------------
| 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 0x1e, which is used
(for now) 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),
Atkinson Expires in 6 Months [Page 3]
Internet Draft ILNP Nonce 10 DEC 2009
and 12 (when the Nonce value is 96-bits).
Nonce Value: This is an unpredictable cryptographically
random value used to prevent off-path
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 cognizant 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 will drop a packet arriving from a
correspondent if the Source Locator of the received packet is not
in the receiving node's ILNP Correspondents Cache's Correspondent
Locator Set 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
Atkinson Expires in 6 Months [Page 4]
Internet Draft ILNP Nonce 10 DEC 2009
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 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 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 Correspondent
Cache. Note that multiple transport-layer sessions between a given
pair of nodes normally share a single entry in the Correspondent
Cache.
5.2 Correspondent Cache
Further, when in the Identifier/Locator Split mode, nodes will need to
retain a Correspondent cache containing several variables for each
correspondent. This cache is per-correspondent, rather than per-flow
or per-session so that if there are multiple sessions with a single
correspondent, Locator changes for all sessions with that
correspondent are handled with a single Locator Update message.
Conceptually, and architecturally, this Correspondents Cache is at the
top of the network-layer since it contains network-layer information
(e.g. Locators) that ought not be made visible to the transport-layer.
Atkinson Expires in 6 Months [Page 5]
Internet Draft ILNP Nonce 10 DEC 2009
The Correspondent Cache contains, for each correspondent, at least:
- Local Identifier(s) in use
- Local Locator(s) in use
- Correspondent's Identifier(s) in use
- Correspondent's Locator(s) in use
- Session Nonce value used Local Node to Correspondent
- Session Nonce value used Correspondent to Local Node
- Information about whether IPsec is being used with
this correspondent.
5.3 IP Security
Note that (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 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 will normally
have one or more I records and one or more L 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 ("I") and Locator ("L") records
in any received DNS replies. DNS servers that support I and L
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 will generate an unpredictable
nonce value, store that value in a local session cache, and
will include the Nonce Destination Option in its initial
packet(s) to the responder. [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 know that the initiator supports
the I/L Split mode and the responder will also operate in
Atkinson Expires in 6 Months [Page 6]
Internet Draft ILNP Nonce 10 DEC 2009
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 know 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 will drop the packet and send an ICMP
Parameter Problem error message back to the initiator.
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 knows 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 using classic IPv6 mode and hence
OMITTING the Nonce Destination Option.
Atkinson Expires in 6 Months [Page 7]
Internet Draft ILNP Nonce 10 DEC 2009
6. 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 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 IPv6 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 Destination
Option must be discarded as forgeries. This security event
should be logged.
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.
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 an implementation optimisation,
it is suggested that when both the Nonce Option and IP Security are
present in a packet, that the Nonce Option value be checked for
validity before beginning IP Security processing.
For environments with data at differing sensitivity levels operating
over common infrastructure, 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.
In all cases, the Nonce Value must be unpredictable and
Atkinson Expires in 6 Months [Page 8]
Internet Draft ILNP Nonce 10 DEC 2009
cryptographically random. RFC-4086 provides concrete advice
on how to generate a suitable nonce value.[RFC-4086]
This option could be designed to optionally carry a 64-bit unsigned
Identifier for the sender as well, if that were considered important.
7. IANA Considerations
A new option number will need to be assigned by IANA to the
Nonce Option described in this note.
Temporarily, for early experimentation, the value 0x1e is
used to mark the Nonce Option.
8. References
8.1. 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.
8.2. Informative References
[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, "Identifier/Locator Concept of
Operations", draft-rja-ilnp-intro-01.txt,
June 2008.
[ILNP-DNS] Atkinson, R, "DNS Resource Records for
Identifier/Locator Use",
draft-rja-ilnp-dns-00.txt, June 2008.
[ILNP-ICMP] Atkinson, R, "ICMP Locator Update message"
draft-rja-ilnp-icmp-00.txt, June 2008.
[RFC-4086] D. Eastlake 3rd, J. Schiller, & S. Crocker,
Atkinson Expires in 6 Months [Page 9]
Internet Draft ILNP Nonce 10 DEC 2009
"Randomness Requirements for Security",
RFC-4086, June 2005.
(Additional references to be added later.)
Author's Address
R. Atkinson
Extreme Networks
3585 Monroe Street
Santa Clara, CA
95051 USA
+1 (408)579-2800
rja@extremenetworks.com
Atkinson Expires in 6 Months [Page 10]
Internet Draft ILNP Nonce 10 DEC 2009
Full Copyright Statement
Copyright (C) The IETF Trust (2008).
This document is subject to the rights, licenses and restrictions
contained in BCP 78, and except as set forth therein, the authors
retain all their rights.
This document and the information contained herein are provided
on an "AS IS" basis and THE CONTRIBUTOR, THE ORGANIZATION HE/SHE
REPRESENTS OR IS SPONSORED BY (IF ANY), THE INTERNET SOCIETY,
THE IETF TRUST AND THE INTERNET ENGINEERING TASK FORCE DISCLAIM
ALL WARRANTIES, EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED TO
ANY WARRANTY THAT THE USE OF THE INFORMATION HEREIN WILL NOT
INFRINGE ANY RIGHTS OR ANY IMPLIED WARRANTIES OF MERCHANTABILITY
OR FITNESS FOR A PARTICULAR PURPOSE.
Intellectual Property
The IETF takes no position regarding the validity or scope of any
Intellectual Property Rights or other rights that might be claimed
to pertain to the implementation or use of the technology
described in this document or the extent to which any license
under such rights might or might not be available; nor does it
represent that it has made any independent effort to identify any
such rights. Information on the procedures with respect to
rights in RFC documents can be found in BCP 78 and BCP 79.
Copies of IPR disclosures made to the IETF Secretariat and any
assurances of licenses to be made available, or the result of an
attempt made to obtain a general license or permission for the use
of such proprietary rights by implementers or users of this
specification can be obtained from the IETF on-line IPR repository
at http://www.ietf.org/ipr.
The IETF invites any interested party to bring to its attention
any copyrights, patents or patent applications, or other
proprietary rights that may cover technology that may be required
to implement this standard. Please address the information to the
IETF at ietf-ipr@ietf.org.
This document may not be modified, and derivative works of it
may not be created.
This document may only be posted in an Internet-Draft.
Expires: 10 June 2009
Atkinson Expires in 6 Months [Page 11]
Internet Draft ILNP Nonce 10 DEC 2009
Atkinson Expires in 6 Months [Page 12]