IPSECME                                                       D. Migault
Internet-Draft                                                  Ericsson
Intended status: Standards Track                             T. Guggemos
Expires: April 18, 20, 2020                                       LMU Munich
                                                                  Y. Nir
                                                                Dell EMC
                                                        October 16, 18, 2019

Implicit IV for Counter-based Ciphers in Encapsulating Security Payload
                                 (ESP)
                   draft-ietf-ipsecme-implicit-iv-08
                   draft-ietf-ipsecme-implicit-iv-09

Abstract

   Encapsulating Security Payload (ESP) sends an initialization vector
   (IV) in each packet.  The size of IV depends on the applied
   transform, being usually 8 or 16 octets for the transforms defined by
   the time this document is written.  Some algorithms such as AES-GCM,
   AES-CCM and ChaCha20-Poly1305 when used with IPsec, take the IV to
   generate a nonce that is used as an input parameter for encrypting
   and decrypting.  These algorithms require a unique  This IV must be unique but do not
   require an unpredictable IV. can be predictable.  As a
   result, the value provided in the ESP Sequence Number (SN) can be
   used instead to generate the nonce.  This avoids sending the IV
   itself, and saves in the case of AES-GCM, AES-CCM and
   ChaCha20-Poly1305 8 octets per packet.  This document describes how
   to do this.

Status of This Memo

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Table of Contents

   1.  Requirements notation . . . . . . . . . . . . . . . . . . . .   2
   2.  Introduction  . . . . . . . . . . . . . . . . . . . . . . . .   2
   3.  Terminology . . . . . . . . . . . . . . . . . . . . . . . . .   3
   4.  Implicit IV . . . . . . . . . . . . . . . . . . . . . . . . .   3
   5.  IKEv2 Initiator Behavior  . . . . . . . . . . . . . . . . . .   4
   6.  IKEv2 Responder Behavior  . . . . . . . . . . . . . . . . . .   5
   7.  Security Considerations . . . . . . . . . . . . . . . . . . .   5
   8.  IANA Considerations . . . . . . . . . . . . . . . . . . . . .   5
   9.  Acknowledgements  . . . . . . . . . . . . . . . . . . . . . .   6
   10. References  . . . . . . . . . . . . . . . . . . . . . . . . .   6
     10.1.  Normative References . . . . . . . . . . . . . . . . . .   6
     10.2.  Informational References . . . . . . . . . . . . . . . .   8
   Authors' Addresses  . . . . . . . . . . . . . . . . . . . . . . .   8

1.  Requirements notation

   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 BCP 14
   [RFC2119], [RFC8174] when, and only when, they appear in all
   capitals, as shown here.

2.  Introduction

   Counter-based AES modes of operation such as AES-CCM ([RFC4309]), and
   AES-GCM ([RFC4106]) require the specification of an nonce for each
   ESP packet.  The same applies for ChaCha20-Poly1305 ([RFC7634]).
   Currently this nonce is generated thanks to the Initialize Initialization Vector
   (IV) provided in each ESP packet ([RFC4303]).  This practice is
   designated in this document as "explicit IV".

   In some contexts, such as IoT, it may be preferable to avoid carrying
   the extra bytes associated to the IV and instead generate it locally
   on each peer.  The local generation of the IV is designated in this
   document as "implicit IV".

   The size of this IV depends on the specific algorithm, but all of the
   algorithms mentioned above take an 8-octet IV.

   This document defines how to compute the IV locally when it is
   implicit.  It also specifies how peers agree with the Internet Key
   Exchange version 2 (IKEv2 - [RFC7296]) on using an implicit IV versus
   an explicit IV.

   This document limits its scope to the algorithms mentioned above.
   Other algorithms with similar properties may later be defined to use
   similar mechanism. mechanisms.

   This document does not consider AES-CBC ([RFC3602]) as AES-CBC
   requires the IV to be unpredictable.  Deriving it directly from the
   packet counter as described below is insecure as mentioned in
   Security Consideration of [RFC3602] and has led to real world chosen
   plain-text attack such as BEAST [BEAST].

   This document does not consider AES-CTR [RFC3686] as it focuses on
   the recommended AEAD suites provided in [RFC8221].

3.  Terminology

   o  IoT: Internet of Things.

   o  IV: Initialization Vector.

   o  IIV: Implicit Initialization Vector.

   o  Nonce: a fixed-size octet string used only once.  In our case, the
      nonce takes the IV as input and is provided as an input parameter
      for encryption/decryption.

4.  Implicit IV

   With the algorithms listed in Section 2, the 8-byte IV MUST NOT
   repeat for a given key.  The binding between an ESP packet and its IV
   is provided using the Sequence Number or the Extended Sequence
   Number.  Figure 1 and Figure 2 represent the IV with a regular 4-byte
   Sequence Number and with an 8-byte Extended Sequence Number
   respectively.

   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
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |                              Zero                             |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |                      Sequence Number                          |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+

            Figure 1: Implicit IV with a 4 byte Sequence Number

   o  Sequence Number: the 4 byte Sequence Number carried in the ESP
      packet.

   o  Zero: a 4 byte array with all bits set to zero.

   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
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |                         Extended                              |
   |                      Sequence Number                          |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+

       Figure 2: Implicit IV with an 8-byte Extended Sequence Number

   o  Extended Sequence Number: the 8-byte Extended Sequence Number of
      the Security Association.  The 4 byte low order bytes are carried
      in the ESP packet.

   This document solely defines the IV generation of the algorithms
   defined in [RFC4106] for AES-GCM, [RFC4309] for AES-CCM and [RFC7634]
   for ChaCha20-Poly1305.  All other aspects and parameters of those
   algorithms are unchanged, and are used as defined in their respective
   specifications.

5.  IKEv2 Initiator Behavior

   An initiator supporting this feature SHOULD propose implicit IV (IIV)
   algorithms in the Transform Type 1 (Encryption Algorithm)
   Substructure of the Proposal Substructure inside the Security
   Association Payload (SA Payload) in the IKEv2 Exchange.  To
   facilitate backward compatibility with non-supporting peers the
   initiator SHOULD also include those same algorithms with explicit IV
   as separate transforms.

6.  IKEv2 Responder Behavior

   The rules of SA Payload processing require that responder picks its
   algorithms from the proposal sent by the initiator, thus this will
   ensure that the responder will never send an SA payload containing
   the IIV transform to an initiator that did not propose it.

7.  Security Considerations

   Nonce generation for these algorithms has not been explicitly
   defined.  It has been left to the implementation as long as certain
   security requirements are met.  Typically, for AES-GCM, AES-CCM and
   ChaCha20-Poly1305, the IV is not allowed to be repeated for one
   particular key.  This document provides an explicit and normative way
   to generate IVs.  The mechanism described in this document meets the
   IV security requirements of all relevant algorithms.

   As the IV must not repeat for one SA when Counter-Mode ciphers are
   used, implicit IV as described in this document MUST NOT be used in
   setups with the chance that the Sequence Number overlaps for one SA.
   The sender's counter and the receiver's counter MUST be reset (by
   establishing a new SA and thus a new key) prior to the transmission
   of the 2^32nd packet for an SA that uses a non extended Sequence
   Number (respectively the 2^64nd packet for an SA that uses an
   Extended Sequence Number).  This prevents sequence number overlaps
   for the mundane point-to-point case.  Multicast as described in
   [RFC5374], [RFC6407] and [I-D.yeung-g-ikev2] is a prominent example,
   where many senders share one secret and thus one SA.  As such,
   Implicit IV may only be used with Multicast if some mechanisms are
   employed that prevent Sequence Number to overlap for one SA,
   otherwise Implicit IV MUST NOT be used with Multicast.

   This document defines three new encryption transforms that use
   implicit IV.  Unlike most encryption transforms defined to date,
   which can be used for both ESP and IKEv2, these transforms are
   defined for ESP only and cannot be used in IKEv2.  The reason is that
   IKEv2 messages don't contain a unique per-message value that can be
   used for IV generation.  The Message-ID field in IKEv2 header is
   similar to the SN field in ESP header, but recent IKEv2 extensions
   ([RFC6311], [RFC7383]) do allow it to repeat, so there is not an easy
   way to derive unique IV from IKEv2 header fields.

8.  IANA Considerations

   The IANA has assigned the following code points:

   -  ENCR_AES_CCM_8_IIV: 29
   -  ENCR_AES_GCM_16_IIV: 30

   -  ENCR_CHACHA20_POLY1305_IIV: 31

   These algorithms should be added with this document as ESP Reference
   and "Not Allowed" for IKEv2 Reference.

9.  Acknowledgements

   We would like to thank Valery Smyslov, Eric Vyncke, Magnus Nystrom
   (security directorate), as well as our three ADs Eric Rescorla,
   Benjamin Kaduk and Roman Danyliw for their valuable comments.  We
   also would like to thank David Schinazi for its implementation, as
   well as the ipseceme chairs Tero Kivinen and David Waltermire for
   moving this work forward.

   NOTE TO THE EDITOR Eric has a accent on E and Magnus has double
   points on o.

10.  References

10.1.  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/info/rfc2119>.

   [RFC3602]  Frankel, S., Glenn, R., and S. Kelly, "The AES-CBC Cipher
              Algorithm and Its Use with IPsec", RFC 3602,
              DOI 10.17487/RFC3602, September 2003,
              <https://www.rfc-editor.org/info/rfc3602>.

   [RFC3686]  Housley, R., "Using Advanced Encryption Standard (AES)
              Counter Mode With IPsec Encapsulating Security Payload
              (ESP)", RFC 3686, DOI 10.17487/RFC3686, January 2004,
              <https://www.rfc-editor.org/info/rfc3686>.

   [RFC4106]  Viega, J. and D. McGrew, "The Use of Galois/Counter Mode
              (GCM) in IPsec Encapsulating Security Payload (ESP)",
              RFC 4106, DOI 10.17487/RFC4106, June 2005,
              <https://www.rfc-editor.org/info/rfc4106>.

   [RFC4303]  Kent, S., "IP Encapsulating Security Payload (ESP)",
              RFC 4303, DOI 10.17487/RFC4303, December 2005,
              <https://www.rfc-editor.org/info/rfc4303>.

   [RFC4309]  Housley, R., "Using Advanced Encryption Standard (AES) CCM
              Mode with IPsec Encapsulating Security Payload (ESP)",
              RFC 4309, DOI 10.17487/RFC4309, December 2005,
              <https://www.rfc-editor.org/info/rfc4309>.

   [RFC5374]  Weis, B., Gross, G., and D. Ignjatic, "Multicast
              Extensions to the Security Architecture for the Internet
              Protocol", RFC 5374, DOI 10.17487/RFC5374, November 2008,
              <https://www.rfc-editor.org/info/rfc5374>.

   [RFC6311]  Singh, R., Ed., Kalyani, G., Nir, Y., Sheffer, Y., and D.
              Zhang, "Protocol Support for High Availability of IKEv2/
              IPsec", RFC 6311, DOI 10.17487/RFC6311, July 2011,
              <https://www.rfc-editor.org/info/rfc6311>.

   [RFC6407]  Weis, B., Rowles, S., and T. Hardjono, "The Group Domain
              of Interpretation", RFC 6407, DOI 10.17487/RFC6407,
              October 2011, <https://www.rfc-editor.org/info/rfc6407>.

   [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/info/rfc7296>.

   [RFC7383]  Smyslov, V., "Internet Key Exchange Protocol Version 2
              (IKEv2) Message Fragmentation", RFC 7383,
              DOI 10.17487/RFC7383, November 2014,
              <https://www.rfc-editor.org/info/rfc7383>.

   [RFC7634]  Nir, Y., "ChaCha20, Poly1305, and Their Use in the
              Internet Key Exchange Protocol (IKE) and IPsec", RFC 7634,
              DOI 10.17487/RFC7634, August 2015,
              <https://www.rfc-editor.org/info/rfc7634>.

   [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/info/rfc8174>.

   [RFC8221]  Wouters, P., Migault, D., Mattsson, J., Nir, Y., and T.
              Kivinen, "Cryptographic Algorithm Implementation
              Requirements and Usage Guidance for Encapsulating Security
              Payload (ESP) and Authentication Header (AH)", RFC 8221,
              DOI 10.17487/RFC8221, October 2017,
              <https://www.rfc-editor.org/info/rfc8221>.

10.2.  Informational References

   [BEAST]    Thai, T. and J. Juliano, "Here Come The xor Ninjas",  ,
              May 2011, <https://www.researchgate.net/
              publication/266529975_Here_Come_The_Ninjas>.

   [I-D.yeung-g-ikev2]
              Weis, B. and V. Smyslov, "Group Key Management using
              IKEv2", draft-yeung-g-ikev2-16 (work in progress), July
              2019.

   [IANA]     "IANA IKEv2 Parameter - Type 1 - Encryption Algorithm
              Transform IDs", <https://www.iana.org/assignments/ikev2-
              parameters/ikev2-parameters.xhtml#ikev2-parameters-5>.

Authors' Addresses

   Daniel Migault
   Ericsson
   8275 Trans Canada Route
   Saint Laurent, QC H4S 0B6
   Canada

   Email: daniel.migault@ericsson.com

   Tobias Guggemos
   LMU Munich
   Oettingenstr. 67
   80538 Munich, Bavaria
   Germany

   Email: guggemos@mnm-team.org
   URI:   http://mnm-team.org/~guggemos

   Yoav Nir
   Dell EMC
   9 Andrei Sakharov St
   Haifa  3190500
   Israel

   Email: ynir.ietf@gmail.com