\
IPSECME Working Group                                         S. Kampati
Internet-Draft                                                    W. Pan
Intended status: Standards Track                                  Huawei
Expires: 14 August 2022                                       P. Wouters
                                                                   Aiven
                                                              M. Bharath
                                                                 Mavenir
                                                                 M. Chen
                                                                    CMCC
                                                      M. Richardson, Ed.
                                                Sandelman Software Works
                                                        10 February 2022


            IKEv2 Optional SA&TS Payloads in Child Exchange
           draft-kampati-ipsecme-ikev2-sa-ts-payloads-opt-08

Abstract

   This document describes a method for reducing the size of the
   Internet Key Exchange version 2 (IKEv2) CREATE_CHILD_SA exchanges
   used for rekeying of the IKE or Child SA by replacing the SA and TS
   payloads with a Notify Message payload.  Reducing size and complexity
   of IKEv2 exchanges is especially useful for low power consumption
   battery powered devices.

About This Document

   This note is to be removed before publishing as an RFC.

   Status information for this document may be found at
   https://datatracker.ietf.org/doc/draft-kampati-ipsecme-ikev2-sa-ts-
   payloads-opt/.

   Discussion of this document takes place on the ipsec Working Group
   mailing list (mailto:ipsec@ietf.org), which is archived at
   https://mailarchive.ietf.org/arch/browse/ipsec/.

   Source for this draft and an issue tracker can be found at
   https://github.com/mcr/ipsecme-ikev2-sa-ts-payloads.git.

Status of This Memo

   This Internet-Draft is submitted in full conformance with the
   provisions of BCP 78 and BCP 79.






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Table of Contents

   1.  Introduction  . . . . . . . . . . . . . . . . . . . . . . . .   3
   2.  Conventions Used in This Document . . . . . . . . . . . . . .   4
     2.1.  Requirements Language . . . . . . . . . . . . . . . . . .   4
   3.  Negotiation of Support for OPTIMIZED REKEY  . . . . . . . . .   4
   4.  Optimized Rekey of the IKE SA . . . . . . . . . . . . . . . .   5
   5.  Optimized Rekey of Child SAs  . . . . . . . . . . . . . . . .   5
   6.  Payload Formats . . . . . . . . . . . . . . . . . . . . . . .   6
     6.1.  OPTIMIZED_REKEY_SUPPORTED Notify  . . . . . . . . . . . .   6
     6.2.  OPTIMIZED_REKEY Notify  . . . . . . . . . . . . . . . . .   7
   7.  IANA Considerations . . . . . . . . . . . . . . . . . . . . .   7
   8.  Operational Considerations  . . . . . . . . . . . . . . . . .   8
   9.  Security Considerations . . . . . . . . . . . . . . . . . . .   8
   10. Acknowledgments . . . . . . . . . . . . . . . . . . . . . . .   8
   11. Normative References  . . . . . . . . . . . . . . . . . . . .   8
   Authors' Addresses  . . . . . . . . . . . . . . . . . . . . . . .   8








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1.  Introduction

   The Internet Key Exchange protocol version 2 (IKEv2) [RFC7296] is
   used to negotiate Security Association (SA) parameters for the IKE SA
   and the Child SAs.  Cryptographic key material for these SAs have a
   limited lifetime before it needs to be refreshed, a process referred
   to as "rekeying".  IKEv2 uses the CREATE_CHILD_SA exchange to rekey
   either the IKE SA or the Child SAs.

   When rekeying, a full set of negotiation parameters are exchanged.
   However, most of these parameters will be the same as before, and
   some of these parameters MUST not change.

   For example, the Traffic Selector (TS) negotiated for the new Child
   SA MUST cover the Traffic Selectors negotiated for the old Child SA.
   And in practically all cases, a new Child SA does not need to cover a
   wider set of Traffic.  In the rare case where this would be needed,
   either a standard rekey could be used or a new Child SA could be
   negotiated followed by a deletion of the replaced Child SA.

   Similarly, IKEv2 states that the cryptographic parameters negotiated
   for rekeying SHOULD NOT be different.  This means that the security
   properties of the IKE or Child SA in practise do not change during a
   typical rekey.

   This document specifies a method to omit these parameters and replace
   them with a single Notify Message declaring that all these parameters
   are identical to the originally negotiated parameters.

   Large scale IKEv2 gateways such as Evolved Packet Data Gateway (ePDG)
   in 4G networks or Centralized Radio Access Network (cRAN/Cloud)
   gateways in 5G networks typically support more than 100,000 IKE/IPsec
   connections.  At any point in time, there will be hundreds or
   thousands of IKE SAs and Child SAs that are being rekeyed.  This
   takes a large amount of bandwidth and CPU power and any protocol
   simplification or bandwidth reducing would result in a significant
   resource saving.

   For Internet of Things (IoT) devices which utilize low power
   consumption technology, reducing the size of the CREATE_CHILD_SA
   exchange for rekeying reduces its power consumption, as sending bytes
   over the air is usually the most power consuming operation of such a
   device.  Reducing the CPU operations required to verify the rekey
   exchanges parameters will also save power and extend the lifetime for
   these devices.






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   When using identical parameters for the IKE SA or Child SA rekey, the
   SA and TS payloads can be omitted thanks to the optimization defined
   in this document.  For an IKE SA rekey, instead of the (large) SA
   payload, only a Key Exchange (KE) payload and a new Notify Type
   payload with the new SPI are required.  For a Child SA payload,
   instead of the SA or TS payloads, only an optional nonce payload
   (when using PFS) and a new Notify Type payload with the new SPI are
   needed.  This makes the rekey exchange packets much smaller and the
   peers do not need to verify that the SA or TS parameters are
   compatible with the old SA parameters.

2.  Conventions Used in This Document

2.1.  Requirements Language

   The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT",
   "SHOULD", "SHOULD NOT", "RECOMMENDED", "NOT RECOMMENDED", "MAY", and
   "OPTIONAL" in this document are to be interpreted as described in
   BCP 14 [RFC2119] [RFC8174] when, and only when, they appear in all
   capitals, as shown here.

3.  Negotiation of Support for OPTIMIZED REKEY

   To indicate support for the optimized rekey negotiation, the
   initiator includes the OPTIMIZED_REKEY_SUPPORTED notify payload in
   the IKE_AUTH exchange request.  During this initial key request, the
   entire SA and TA payloads are included as normal.  A responder that
   supports the optimized rekey exchange includes the
   OPTIMIZED_REKEY_SUPPORTED notify payload in its response.  Note that
   the notify indicates support for optimized rekey for both IKE and
   Child SAs.

   A responder that does not support the optimized rekey exchange
   processes the SA and TA payloads as normal, and does not include the
   new Notify.  As per regular IKEv2 processing, a responder that does
   not recognize this new Notify, MUST ignore the notify.  Responders
   may have been administratively configured with the optimization
   turned off for local reasons.  The absense of the Notify indicates to
   the initiator that the optimization is not available, and normal,
   full rekey should be done.

   When a peer wishes to rekey an IKE SA or Child SA, it MAY use the
   optimized rekey method during the CREATE_CHILD_SA exchange.  If both
   peers have exchanged OPTIMIZED_REKEY_SUPPORTED notifies, peers SHOULD
   use the optimized rekey method for rekeys.  Non-optimized, regular
   rekey requests MUST always be accepted.

   The IKE_AUTH message exchange in this case is shown below:



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   Initiator                       Responder
   --------------------------------------------------------------------
   HDR, SK {IDi, [CERT,] [CERTREQ,]
       [IDr,] AUTH, SAi2, TSi, TSr,
       N(OPTIMIZED_REKEY_SUPPORTED)} -->
                               <-- HDR, SK {IDr, [CERT,] AUTH,
                                       SAr2, TSi, TSr,
                                       N(OPTIMIZED_REKEY_SUPPORTED)}

4.  Optimized Rekey of the IKE SA

   The initiator of an optimized rekey request sends a CREATE_CHILD_SA
   payload with the OPTIMIZED_REKEY notify payload containing the new
   Security Parameter Index (SPI) for the new IKE SA.  It omits the SA
   payload.

   The responder of an optimized rekey request replies with an included
   OPTIMIZED_REKEY notify with its new IKE SPI and also omits the SA
   payload.

   Both parties send their nonce and KE payloads just as they would do
   for a regular IKE SA rekey.

   Using the old SPI from the IKE header and the two new SPIs
   respectively from the initiator and responder's OPTIMIZED_REKEY
   payloads, both parties can perform the IKE SA rekey operation.

   The CREATE_CHILD_SA message exchange in this case is shown below:

   Initiator                       Responder
   --------------------------------------------------------------------
   HDR, SK {N(OPTIMIZED_REKEY,newSPIi),
            Ni, KEi} -->
                               <-- HDR, SK {N(OPTIMIZED_REKEY,newSPIr),
                                            Nr, KEr}

5.  Optimized Rekey of Child SAs

   The initiator of an optimized rekey request sends a CREATE_CHILD_SA
   payload with the OPTIMIZED_REKEY notify payload containing the new
   Security Parameter Index (SPI) for the new Child SA.  It omits the SA
   and TS payloads.  If the current Child SA was negotiated with Perfect
   Forward Secrecy (PFS), a KEi payload MUST be included as well.  If no
   PFS was negotiated for the current Child SA, a KEi payload MUST NOT
   be included.






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   The responder of an optimized rekey request performs the same
   process.  It includes the OPTIMIZED_REKEY notify with its new IKE SPI
   and omits the SA and TS payloads.  Depending on the PFS negotiation
   of the current Child SA, the responder includes a KEr payload.

   Both parties send their nonce payloads just as they would do for a
   regular Child SA rekey.

   Using the old SPI from the REKEY_SA payload and the two new SPIs
   respectively from the initiator and responder's OPTIMIZED_REKEY
   payloads, both parties can perform the Child SA rekey operation.

   The CREATE_CHILD_SA message exchange in this case is shown below:

   Initiator                       Responder
   --------------------------------------------------------------------
   HDR, SK {N(REKEY_SA,oldSPI), N(OPTIMIZED_REKEY,newSPIi),
            Ni, [KEi,]} -->
                               <-- HDR, SK {N(OPTIMIZED_REKEY,newSPIr),
                                            Nr, [KEr,]}

6.  Payload Formats

6.1.  OPTIMIZED_REKEY_SUPPORTED Notify

   The OPTIMIZED_REKEY_SUPPORTED Notify Message type notification is
   used by the initiator and responder to indicate their support for the
   optimized rekey negotiation.

                        1                   2                   3
    0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
   +---------------+-+-------------+-------------------------------+
   | Next Payload  |C|  RESERVED   |         Payload Length        |
   +---------------+-+-------------+-------------------------------+
   |Protocol ID(=0)| SPI Size (=0) |      Notify Message Type      |
   +---------------+---------------+-------------------------------+

   *  Protocol ID (1 octet) - MUST be 0.

   *  SPI Size (1 octet) - MUST be 0, meaning no SPI is present.

   *  Notify Message Type (2 octets) - MUST be set to the value TBD1.

   This Notify Message type contains no data.

   The Critical bit MUST be 0.  A non-zero value MUST be ignored.





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6.2.  OPTIMIZED_REKEY Notify

   The OPTIMIZED_REKEY Notify Message type is used to perform an
   optimized IKE SA or Child SA rekey.

    0                 1                   2                   3
    0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
   +---------------+-+-------------+-------------------------------+
   | Next Payload  |C|  RESERVED   |         Payload Length        |
   +---------------+-+-------------+-------------------------------+
   |Protocol ID    | SPI Size (=8) |      Notify Message Type      |
   +---------------+---------------+-------------------------------+
   |                Security Parameter Index (SPI)                 |
   |                                                               |
   +---------------------------------------------------------------+

   *  Protocol ID (1 octet) - For an IKE SA rekey, this field MUST
      contain (1).  For Child SAs, this field MUST contain either (2) to
      indicate AH or (3) to indicate ESP.

   *  SPI Size (1 octet) - MUST be 8 when rekeying an IKE SA.  MUST be 4
      when rekeying a Child SA.

   *  Notify Message Type (2 octets) - MUST be set to the value TBD2.

   *  SPI (4 octets or 8 octets) - Security Parameter Index.  The new
      SPI.

   The Critical bit MUST be 1.  A value of 0 MUST be ignored.

7.  IANA Considerations

   This document defines two new Notify Message Types in the "IKEv2
   Notify Message Types - Status Types" registry.  IANA is requested to
   assign codepoints in this registry.

   NOTIFY messages: status types            Value
   ----------------------------------------------------------
   OPTIMIZED_REKEY_SUPPORTED                TBD1
   OPTIMIZED_REKEY                          TBD2











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8.  Operational Considerations

   Some implementations allow sending rekey messages with a different
   set of Traffic Selectors or cryptographic parameters in response to a
   configuration update.  IKEv2 states this SHOULD NOT be done.  Whether
   or not optimized rekeying is used, a configuration change that
   changes the Traffic Selectors or cryptographic parameters MUST NOT
   use the optimized rekey method.  It SHOULD also not use a regular
   rekey method but instead start an entire new IKE and Child SA
   negotiation with the new parameters.

9.  Security Considerations

   The optimized rekey removes sending unnecessary new parameters that
   originally would have to be validated against the original
   parameters.  In that sense, this optimization enhances the security
   of the rekey process by reducing the complexity and code required.

10.  Acknowledgments

   Special thanks to Valery Smyslov and Antony Antony.

11.  Normative References

   [RFC2119]  Bradner, S., "Key words for use in RFCs to Indicate
              Requirement Levels", BCP 14, RFC 2119,
              DOI 10.17487/RFC2119, March 1997,
              <https://www.rfc-editor.org/rfc/rfc2119>.

   [RFC7296]  Kaufman, C., Hoffman, P., Nir, Y., Eronen, P., and T.
              Kivinen, "Internet Key Exchange Protocol Version 2
              (IKEv2)", STD 79, RFC 7296, DOI 10.17487/RFC7296, October
              2014, <https://www.rfc-editor.org/rfc/rfc7296>.

   [RFC8174]  Leiba, B., "Ambiguity of Uppercase vs Lowercase in RFC
              2119 Key Words", BCP 14, RFC 8174, DOI 10.17487/RFC8174,
              May 2017, <https://www.rfc-editor.org/rfc/rfc8174>.

Authors' Addresses

   Sandeep Kampati
   Huawei Technologies
   Divyashree Techno Park, Whitefield
   Bangalore 560066
   Karnataka
   India

   Email: sandeepkampati@huawei.com



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   Wei Pan
   Huawei Technologies
   101 Software Avenue, Yuhuatai District
   Nanjing
   Jiangsu,
   China

   Email: william.panwei@huawei.com


   Paul Wouters
   Aiven

   Email: paul.wouters@aiven.io


   Meduri S S Bharath
   Mavenir Systems Pvt Ltd
   Manyata Tech Park
   Bangalore
   Karnataka
   India

   Email: bharath.meduri@mavenir.com


   Meiling Chen
   China Mobile
   32 Xuanwumen West Street, West District
   Beijing
   100053
   China

   Email: chenmeiling@chinamobile.com


   Michael Richardson (editor)
   Sandelman Software Works

   Email: mcr+ietf@sandelman.ca











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