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Versions: (draft-farinacci-lisp-crypto) 00 01 02 03 04 05 06 07 08 09 10 RFC 8061

Internet Engineering Task Force                             D. Farinacci
Internet-Draft                                               lispers.net
Intended status: Experimental                                    B. Weis
Expires: April 17, 2017                                    cisco Systems
                                                        October 14, 2016


                    LISP Data-Plane Confidentiality
                       draft-ietf-lisp-crypto-10

Abstract

   This document describes a mechanism for encrypting LISP encapsulated
   traffic.  The design describes how key exchange is achieved using
   existing LISP control-plane mechanisms as well as how to secure the
   LISP data-plane from third-party surveillance attacks.

Status of This Memo

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

   Internet-Drafts are working documents of the Internet Engineering
   Task Force (IETF).  Note that other groups may also distribute
   working documents as Internet-Drafts.  The list of current Internet-
   Drafts is at http://datatracker.ietf.org/drafts/current/.

   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."

   This Internet-Draft will expire on April 17, 2017.

Copyright Notice

   Copyright (c) 2016 IETF Trust and the persons identified as the
   document authors.  All rights reserved.

   This document is subject to BCP 78 and the IETF Trust's Legal
   Provisions Relating to IETF Documents
   (http://trustee.ietf.org/license-info) in effect on the date of
   publication of this document.  Please review these documents
   carefully, as they describe your rights and restrictions with respect
   to this document.  Code Components extracted from this document must
   include Simplified BSD License text as described in Section 4.e of
   the Trust Legal Provisions and are provided without warranty as
   described in the Simplified BSD License.



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Table of Contents

   1.  Introduction  . . . . . . . . . . . . . . . . . . . . . . . .   2
   2.  Requirements Notation . . . . . . . . . . . . . . . . . . . .   4
   3.  Definition of Terms . . . . . . . . . . . . . . . . . . . . .   4
   4.  Overview  . . . . . . . . . . . . . . . . . . . . . . . . . .   4
   5.  Diffie-Hellman Key Exchange . . . . . . . . . . . . . . . . .   4
   6.  Encoding and Transmitting Key Material  . . . . . . . . . . .   5
   7.  Shared Keys used for the Data-Plane . . . . . . . . . . . . .   8
   8.  Data-Plane Operation  . . . . . . . . . . . . . . . . . . . .  10
   9.  Procedures for Encryption and Decryption  . . . . . . . . . .  11
   10. Dynamic Rekeying  . . . . . . . . . . . . . . . . . . . . . .  12
   11. Future Work . . . . . . . . . . . . . . . . . . . . . . . . .  13
   12. Security Considerations . . . . . . . . . . . . . . . . . . .  13
     12.1.  SAAG Support . . . . . . . . . . . . . . . . . . . . . .  13
     12.2.  LISP-Crypto Security Threats . . . . . . . . . . . . . .  14
   13. IANA Considerations . . . . . . . . . . . . . . . . . . . . .  14
   14. References  . . . . . . . . . . . . . . . . . . . . . . . . .  15
     14.1.  Normative References . . . . . . . . . . . . . . . . . .  15
     14.2.  Informative References . . . . . . . . . . . . . . . . .  16
   Appendix A.  Acknowledgments  . . . . . . . . . . . . . . . . . .  17
   Appendix B.  Document Change Log  . . . . . . . . . . . . . . . .  17
     B.1.  Changes to draft-ietf-lisp-crypto-10.txt  . . . . . . . .  17
     B.2.  Changes to draft-ietf-lisp-crypto-09.txt  . . . . . . . .  18
     B.3.  Changes to draft-ietf-lisp-crypto-08.txt  . . . . . . . .  18
     B.4.  Changes to draft-ietf-lisp-crypto-07.txt  . . . . . . . .  18
     B.5.  Changes to draft-ietf-lisp-crypto-06.txt  . . . . . . . .  18
     B.6.  Changes to draft-ietf-lisp-crypto-05.txt  . . . . . . . .  18
     B.7.  Changes to draft-ietf-lisp-crypto-04.txt  . . . . . . . .  18
     B.8.  Changes to draft-ietf-lisp-crypto-03.txt  . . . . . . . .  18
     B.9.  Changes to draft-ietf-lisp-crypto-02.txt  . . . . . . . .  19
     B.10. Changes to draft-ietf-lisp-crypto-01.txt  . . . . . . . .  19
     B.11. Changes to draft-ietf-lisp-crypto-00.txt  . . . . . . . .  19
     B.12. Changes to draft-farinacci-lisp-crypto-01.txt . . . . . .  20
     B.13. Changes to draft-farinacci-lisp-crypto-00.txt . . . . . .  20
   Authors' Addresses  . . . . . . . . . . . . . . . . . . . . . . .  20

1.  Introduction

   This document describes a mechanism for encrypting LISP encapsulated
   traffic.  The design describes how key exchange is achieved using
   existing LISP control-plane mechanisms as well as how to secure the
   LISP data-plane from third-party surveillance attacks.

   The Locator/ID Separation Protocol [RFC6830] defines a set of
   functions for routers to exchange information used to map from non-
   routable Endpoint Identifiers (EIDs) to routable Routing Locators
   (RLOCs).  LISP Ingress Tunnel Routers (ITRs) and Proxy Ingress Tunnel



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   Routers (PITRs) encapsulate packets to Egress Tunnel Routers (ETRs)
   and Reencapsulating Tunnel Routers (RTRs).  Packets that arrive at
   the ITR or PITR may not be encrypted, which means no protection or
   privacy of the data is added.  When the source host encrypts the data
   stream, encapsulated packets do not need to be encrypted by LISP.
   However, when plaintext packets are sent by hosts, this design can
   encrypt the user payload to maintain privacy on the path between the
   encapsulator (the ITR or PITR) to a decapsulator (ETR or RTR).  The
   encrypted payload is unidirectional.  However, return traffic uses
   the same procedures but with different key values by the same xTRs or
   potentially different xTRs when the paths between LISP sites are
   asymmetric.

   This document has the following requirements (as well as the general
   requirements from [RFC6973]) for the solution space:

   o  Do not require a separate Public Key Infrastructure (PKI) that is
      out of scope of the LISP control-plane architecture.

   o  The budget for key exchange MUST be one round-trip time.  That is,
      only a two packet exchange can occur.

   o  Use symmetric keying so faster cryptography can be performed in
      the LISP data plane.

   o  Avoid a third-party trust anchor if possible.

   o  Provide for rekeying when secret keys are compromised.

   o  Support Authenticated Encryption with packet integrity checks.

   o  Support multiple cipher suites so new crypto algorithms can be
      easily introduced.

   Satisfying the above requirements provides the following benefits:

   o  Avoiding a PKI reduces the operational cost of managing a secure
      network.  Key management is distributed and independent from any
      other infrastructure.

   o  Packet transport is optimized due to less packet headers.  Packet
      loss is reduced by a more efficient key exchange.

   o  Authentication and privacy are provided with a single mechanism
      thereby providing less per packet overhead and therefore more
      resource efficiency.





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2.  Requirements Notation

   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 [RFC2119].

3.  Definition of Terms

   AEAD: Authenticated Encryption with Additional Data [RFC5116].

   ICV: Integrity Check Value.

   LCAF: LISP Canonical Address Format ([LCAF]).

   xTR: A general reference to ITRs, ETRs, RTRs, and PxTRs.

4.  Overview

   The approach proposed in this document is to NOT rely on the LISP
   mapping system (or any other key infrastructure system) to store
   security keys.  This will provide for a simpler and more secure
   mechanism.  Secret shared keys will be negotiated between the ITR and
   the ETR in Map-Request and Map-Reply messages.  Therefore, when an
   ITR needs to obtain the RLOC of an ETR, it will get security material
   to compute a shared secret with the ETR.

   The ITR can compute 3 shared-secrets per ETR the ITR is encapsulating
   to.  When the ITR encrypts a packet before encapsulation, it will
   identify the key it used for the crypto calculation so the ETR knows
   which key to use for decrypting the packet after decapsulation.  By
   using key-ids in the LISP header, we can also get fast rekeying
   functionality.

   The key management described in this documemnt is unidirectional from
   the ITR (the encapsulator) to the ETR (the decapsultor).

5.  Diffie-Hellman Key Exchange

   LISP will use a Diffie-Hellman [RFC2631] key exchange sequence and
   computation for computing a shared secret.  The Diffie-Hellman
   parameters will be passed via Cipher Suite code-points in Map-Request
   and Map-Reply messages.

   Here is a brief description how Diff-Hellman works:







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   +----------------------------+---------+----------------------------+
   |              ITR           |         |           ETR              |
   +------+--------+------------+---------+------------+---------------+
   |Secret| Public | Calculates |  Sends  | Calculates | Public |Secret|
   +------|--------|------------|---------|------------|--------|------+
   |  i   |  p,g   |            | p,g --> |            |        |  e   |
   +------|--------|------------|---------|------------|--------|------+
   |  i   | p,g,I  |g^i mod p=I |  I -->  |            | p,g,I  |  e   |
   +------|--------|------------|---------|------------|--------|------+
   |  i   | p,g,I  |            |  <-- E  |g^e mod p=E |  p,g   |  e   |
   +------|--------|------------|---------|------------|--------|------+
   | i,s  |p,g,I,E |E^i mod p=s |         |I^e mod p=s |p,g,I,E | e,s  |
   +------|--------|------------|---------|------------|--------|------+

        Public-key exchange for computing a shared private key [DH]

   Diffie-Hellman parameters 'p' and 'g' must be the same values used by
   the ITR and ETR.  The ITR computes public-key 'I' and transmits 'I'
   in a Map-Request packet.  When the ETR receives the Map-Request, it
   uses parameters 'p' and 'g' to compute the ETR's public key 'E'.  The
   ETR transmits 'E' in a Map-Reply message.  At this point, the ETR has
   enough information to compute 's', the shared secret, by using 'I' as
   the base and the ETR's private key 'e' as the exponent.  When the ITR
   receives the Map-Reply, it uses the ETR's public-key 'E' with the
   ITR's private key 'i' to compute the same 's' shared secret the ETR
   computed.  The value 'p' is used as a modulus to create the width of
   the shared secret 's' (see Section 6).

6.  Encoding and Transmitting Key Material

   The Diffie-Hellman key material is transmitted in Map-Request and
   Map-Reply messages.  Diffie-Hellman parameters are encoded in the
   LISP Security Type LCAF [LCAF].


















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     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
    +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
    |           AFI = 16387         |     Rsvd1     |     Flags     |
    +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
    |   Type = 11   |      Rsvd2    |             6 + n             |
    +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
    |   Key Count   |      Rsvd3    | Cipher Suite  |   Rsvd4     |R|
    +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
    |           Key Length          |     Public Key Material ...   |
    +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
    |                    ... Public Key Material                    |
    +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
    |              AFI = x          |       Locator Address ...     |
    +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+

   Cipher Suite field contains DH Key Exchange and Cipher/Hash Functions

   The 'Key Count' field encodes the number of {'Key-Length', 'Key-
   Material'} fields included in the encoded LCAF.  The maximum number
   of keys that can be encoded are 3, each identified by key-id 1,
   followed by key-id 2, and finally key-id 3.

   The 'R' bit is not used for this use-case of the Security Type LCAF
   but is reserved for [LISP-DDT] security.  Therefore, the R bit SHOULD
   be transmitted as 0 and MUST be ignored on receipt.

























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 Cipher Suite 0:
    Reserved

 Cipher Suite 1:
    Diffie-Hellman Group: 2048-bit MODP [RFC3526]
    Encryption:  AES with 128-bit keys in CBC mode [AES-CBC]
    Integrity:   Integrated with [AES-CBC] AEAD_AES_128_CBC_HMAC_SHA_256
    IV length:   16 bytes
    KDF:         HMAC-SHA-256

 Cipher Suite 2:
    Diffie-Hellman Group: 256-bit Elliptic-Curve 25519 [CURVE25519]
    Encryption:  AES with 128-bit keys in CBC mode [AES-CBC]
    Integrity:   Integrated with [AES-CBC] AEAD_AES_128_CBC_HMAC_SHA_256
    IV length:   16 bytes
    KDF:         HMAC-SHA-256

 Cipher Suite 3:
    Diffie-Hellman Group: 2048-bit MODP [RFC3526]
    Encryption:  AES with 128-bit keys in GCM mode [RFC5116]
    Integrity:   Integrated with [RFC5116] AEAD_AES_128_GCM
    IV length:   12 bytes
    KDF:         HMAC-SHA-256

 Cipher Suite 4:
    Diffie-Hellman Group: 3072-bit MODP [RFC3526]
    Encryption:  AES with 128-bit keys in GCM mode [RFC5116]
    Integrity:   Integrated with [RFC5116] AEAD_AES_128_GCM
    IV length:   12 bytes
    KDF:         HMAC-SHA-256

 Cipher Suite 5:
    Diffie-Hellman Group: 256-bit Elliptic-Curve 25519 [CURVE25519]
    Encryption:  AES with 128-bit keys in GCM mode [RFC5116]
    Integrity:   Integrated with [RFC5116] AEAD_AES_128_GCM
    IV length:   12 bytes
    KDF:         HMAC-SHA-256

 Cipher Suite 6:
    Diffie-Hellman Group: 256-bit Elliptic-Curve 25519 [CURVE25519]
    Encryption: Chacha20-Poly1305 [CHACHA-POLY] [RFC7539]
    Integrity:  Integrated with [CHACHA-POLY] AEAD_CHACHA20_POLY1305
    IV length:  8 bytes
    KDF:        HMAC-SHA-256







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   The "Public Key Material" field contains the public key generated by
   one of the Cipher Suites defined above.  The length of the key in
   octets is encoded in the "Key Length" field.

   When an ITR, PITR, or RTR sends a Map-Request, they will encode their
   own RLOC in the Security Type LCAF format within the ITR-RLOCs field.
   When a ETR or RTR sends a Map-Reply, they will encode their RLOCs in
   Security Type LCAF format within the RLOC-record field of each EID-
   record supplied.

   If an ITR, PITR, or RTR sends a Map-Request with the Security Type
   LCAF included and the ETR or RTR does not want to have encapsulated
   traffic encrypted, they will return a Map-Reply with no RLOC records
   encoded with the Security Type LCAF.  This signals to the ITR, PITR
   or RTR not to encrypt traffic (it cannot encrypt traffic anyways
   since no ETR public-key was returned).

   Likewise, if an ITR or PITR wish to include multiple key-ids in the
   Map-Request but the ETR or RTR wish to use some but not all of the
   key-ids, they return a Map-Reply only for those key-ids they wish to
   use.

7.  Shared Keys used for the Data-Plane

   When an ITR or PITR receives a Map-Reply accepting the Cipher Suite
   sent in the Map-Request, it is ready to create data plane keys.  The
   same process is followed by the ETR or RTR returning the Map-Reply.

   The first step is to create a shared secret, using the peer's shared
   Diffie-Hellman Public Key Material combined with device's own private
   keying material as described in Section 5.  The Diffie-Hellman
   parameters used is defined in the cipher suite sent in the Map-
   Request and copied into the Map-Reply.

   The resulting shared secret is used to compute an AEAD-key for the
   algorithms specified in the cipher suite.  A Key Derivation Function
   (KDF) in counter mode as specified by [NIST-SP800-108] is used to
   generate the data-plane keys.  The amount of keying material that is
   derived depends on the algorithms in the cipher suite.

   The inputs to the KDF are as follows:

   o  KDF function.  This is HMAC-SHA-256 in this document but generally
      specified in each Cipher Suite definition.

   o  A key for the KDF function.  This is the computed Diffie-Hellman
      shared secret.




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   o  Context that binds the use of the data-plane keys to this session.
      The context is made up of the following fields, which are
      concatenated and provided as the data to be acted upon by the KDF
      function.

   Context:

   o  A counter, represented as a two-octet value in network byte order.

   o  The null-terminated string "lisp-crypto".

   o  The ITR's nonce from the Map-Request the cipher suite was included
      in.

   o  The number of bits of keying material required (L), represented as
      a two-octet value in network byte order.

   The counter value in the context is first set to 1.  When the amount
   of keying material exceeds the number of bits returned by the KDF
   function, then the KDF function is called again with the same inputs
   except that the counter increments for each call.  When enough keying
   material is returned, it is concatenated and used to create keys.

   For example, AES with 128-bit keys requires 16 octets (128 bits) of
   keying material, and HMAC-SHA1-96 requires another 16 octets (128
   bits) of keying material in order to maintain a consistent 128-bits
   of security.  Since 32 octets (256 bits) of keying material are
   required, and the KDF function HMAC-SHA-256 outputs 256 bits, only
   one call is required.  The inputs are as follows:

   key-material = HMAC-SHA-256(dh-shared-secret, context)

       where: context = 0x0001 || "lisp-crypto" || <itr-nonce> || 0x0100

   In contrast, a cipher suite specifying AES with 256-bit keys requires
   32 octets (256 bits) of keying material, and HMAC-SHA256-128 requires
   another 32 octets (256 bits) of keying material in order to maintain
   a consistent 256-bits of security.  Since 64 octets (512 bits) of
   keying material are required, and the KDF function HMAC-SHA-256
   outputs 256 bits, two calls are required.











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   key-material-1 = HMAC-SHA-256(dh-shared-secret, context)

       where: context = 0x0001 || "lisp-crypto" || <itr-nonce> || 0x0200

   key-material-2 = HMAC-SHA-256(dh-shared-secret, context)

       where: context = 0x0002 || "lisp-crypto" || <itr-nonce> || 0x0200

   key-material = key-material-1 || key-material-2

   If the key-material is longer than the required number of bits (L),
   then only the most significant L bits are used.

   From the derived key-material, the most significant 256 bits are used
   for the AEAD-key by AEAD ciphers.  The 256-bit AEAD-key is divided
   into a 128-bit encryption key and a 128-bit integrity check key
   internal to the cipher used by the ITR.

8.  Data-Plane Operation

   The LISP encapsulation header [RFC6830] requires changes to encode
   the key-id for the key being used for encryption.

     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
    +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
  / |       Source Port = xxxx      |       Dest Port = 4341        |
UDP +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
  \ |           UDP Length          |        UDP Checksum           |
    +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
L / |N|L|E|V|I|R|K|K|            Nonce/Map-Version                  |\ \
I   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ |A
S \ |                 Instance ID/Locator-Status-Bits               | |D
P   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ |/
    |                   Initialization Vector (IV)                  | I
E   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ C
n / |                                                               | V
c   |                                                               | |
r   |                Packet Payload with EID Header ...             | |
y   |                                                               | |
p \ |                                                               |/
t   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+

        K-bits indicate when packet is encrypted and which key used

   When the KK bits are 00, the encapsulated packet is not encrypted.
   When the value of the KK bits are 1, 2, or 3, it encodes the key-id
   of the secret keys computed during the Diffie-Hellman Map-Request/



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   Map-Reply exchange.  When the KK bits are not 0, the payload is
   prepended with an Initialization Vector (IV).  The length of the IV
   field is based on the cipher suite used.  Since all cipher suites
   defined in this document do Authenticated Encryption (AEAD), an ICV
   field does not need to be present in the packet since it is included
   in the ciphertext.  The Additional Data (AD) used for the ICV is
   shown above and includes the LISP header, the IV field and the packet
   payload.

   When an ITR or PITR receives a packet to be encapsulated, the device
   will first decide what key to use, encode the key-id into the LISP
   header, and use that key to encrypt all packet data that follows the
   LISP header.  Therefore, the outer header, UDP header, and LISP
   header travel as plaintext.

   There is an open working group item to discuss if the data
   encapsulation header needs change for encryption or any new
   applications.  This document proposes changes to the existing header
   so experimentation can continue without making large changes to the
   data-plane at this time.  This document allocates 2 bits of the
   previously unused 3 flag bits (note the R-bit above is still a
   reserved flag bit as documented in [RFC6830]) for the KK bits.

9.  Procedures for Encryption and Decryption

   When an ITR, PITR, or RTR encapsulate a packet and have already
   computed an AEAD-key (detailed in section Section 7) that is
   associated with a destination RLOC, the following encryption and
   encapsulation procedures are performed:

   1.  The encapsulator creates an IV and prepends the IV value to the
       packet being encapsulated.  For GCM and Chacha cipher suites, the
       IV is incremented for every packet (beginning with a value of 1
       in the first packet) and sent to the destination RLOC.  For CBC
       cipher suites, the IV is a new random number for every packet
       sent to the destination RLOC.  For the Chacha cipher suite, the
       IV is an 8-byte random value that is appended to a 4-byte counter
       that is incremented for every packet (beginning with a value of 1
       in the first packet).

   2.  Next encrypt with cipher function AES or Chacha20 using the AEAD-
       key over the packet payload following the AEAD specification
       referenced in the cipher suite definition.  This does not include
       the IV.  The IV must be transmitted as plaintext so the decrypter
       can use it as input to the decryption cipher.  The payload should
       be padded to an integral number of bytes a block cipher may
       require.  The result of the AEAD operation may contain an ICV,
       the size of which is defined by the referenced AEAD



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       specification.  Note that the AD (i.e. the LISP header exactly as
       will be prepended in the next step and the IV) must be given to
       the AEAD encryption function as the "associated data" argument.

   3.  Prepend the LISP header.  The key-id field of the LISP header is
       set to the key-id value that corresponds to key-pair used for the
       encryption cipher.

   4.  Lastly, prepend the UDP header and outer IP header onto the
       encrypted packet and send packet to destination RLOC.

   When an ETR, PETR, or RTR receive an encapsulated packet, the
   following decapsulation and decryption procedures are performed:

   1.  The outer IP header, UDP header, LISP header, and IV field are
       stripped from the start of the packet.  The LISP header and IV
       are retained and given to the AEAD decryption operation as the
       "associated data" argument.

   2.  The packet is decrypted using the AEAD-key and the IV from the
       packet.  The AEAD-key is obtained from a local-cache associated
       with the key-id value from the LISP header.  The result of the
       decryption function is a plaintext packet payload if the cipher
       returned a verified ICV.  Otherwise, the packet is invalid and is
       discarded.  If the AEAD specification included an ICV, the AEAD
       decryption function will locate the ICV in the ciphertext and
       compare it to a version of the ICV that the AEAD decryption
       function computes.  If the computed ICV is different than the ICV
       located in the ciphertext, then it will be considered tampered.

   3.  If the packet was not tampered with, the decrypted packet is
       forwarded to the destination EID.

10.  Dynamic Rekeying

   Since multiple keys can be encoded in both control and data messages,
   an ITR can encapsulate and encrypt with a specific key while it is
   negotiating other keys with the same ETR.  As soon as an ETR or RTR
   returns a Map-Reply, it should be prepared to decapsulate and decrypt
   using the new keys computed with the new Diffie-Hellman parameters
   received in the Map-Request and returned in the Map-Reply.

   RLOC-probing can be used to change keys or cipher suites by the ITR
   at any time.  And when an initial Map-Request is sent to populate the
   ITR's map-cache, the Map-Request flows across the mapping system
   where a single ETR from the Map-Reply RLOC-set will respond.  If the
   ITR decides to use the other RLOCs in the RLOC-set, it MUST send a
   Map-Request directly to negotiate security parameters with the ETR.



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   This process may be used to test reachability from an ITR to an ETR
   initially when a map-cache entry is added for the first time, so an
   ITR can get both reachability status and keys negotiated with one
   Map-Request/Map-Reply exchange.

   A rekeying event is defined to be when an ITR or PITR changes the
   cipher suite or public-key in the Map-Request.  The ETR or RTR
   compares the cipher suite and public-key it last received from the
   ITR for the key-id, and if any value has changed, it computes a new
   public-key and cipher suite requested by the ITR from the Map-Request
   and returns it in the Map-Reply.  Now a new shared secret is computed
   and can be used for the key-id for encryption by the ITR and
   decryption by the ETR.  When the ITR or PITR starts this process of
   negotiating a new key, it must not use the corresponding key-id in
   encapsulated packets until it receives a Map-Reply from the ETR with
   the same cipher suite value it expects (the values it sent in a Map-
   Request).

   Note when RLOC-probing continues to maintain RLOC reachability and
   rekeying is not desirable, the ITR or RTR can either not include the
   Security Type LCAF in the Map-Request or supply the same key material
   as it received from the last Map-Reply from the ETR or RTR.  This
   approach signals to the ETR or RTR that no rekeying event is
   requested.

11.  Future Work

   For performance considerations, newer Elliptic-Curve Diffie-Hellman
   (ECDH) groups can be used as specified in [RFC4492] and [RFC6090] to
   reduce CPU cycles required to compute shared secret keys.

   For better security considerations as well as to be able to build
   faster software implementations, newer approaches to ciphers and
   authentication methods will be researched and tested.  Some examples
   are Chacha20 and Poly1305 [CHACHA-POLY] [RFC7539].

12.  Security Considerations

12.1.  SAAG Support

   The LISP working group received security advice and guidance from the
   Security Area Advisory Group (SAAG).  The SAAG has been involved
   early in the design process and their input and reviews have been
   included in this document.

   Comments from the SAAG included:

   1.  Do not use asymmetric ciphers in the data-plane.



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   2.  Consider adding ECDH early in the design.

   3.  Add cipher suites because ciphers are created more frequently
       than protocols that use them.

   4.  Consider the newer AEAD technology so authentication comes with
       doing encryption.

12.2.  LISP-Crypto Security Threats

   Since ITRs and ETRs participate in key exchange over a public non-
   secure network, a man-in-the-middle (MITM) could circumvent the key
   exchange and compromise data-plane confidentiality.  This can happen
   when the MITM is acting as a Map-Replier, provides its own public key
   so the ITR and the MITM generate a shared secret key among each
   other.  If the MITM is in the data path between the ITR and ETR, it
   can use the shared secret key to decrypt traffic from the ITR.

   Since LISP can secure Map-Replies by the authentication process
   specified in [LISP-SEC], the ITR can detect when a MITM has signed a
   Map-Reply for an EID-prefix it is not authoritative for.  When an ITR
   determines the signature verification fails, it discards and does not
   reuse the key exchange parameters, avoids using the ETR for
   encapsulation, and issues a severe log message to the network
   administrator.  Optionally, the ITR can send RLOC-probes to the
   compromised RLOC to determine if can reach the authoritative ETR.
   And when the ITR validates the signature of a Map-Reply, it can begin
   encrypting and encapsulating packets to the RLOC of ETR.

13.  IANA Considerations

   This document describes a mechanism for encrypting LISP encapsulated
   packets based on Diffie-Hellman key exchange procedures.  During the
   exchange the devices have to agree on a Cipher Suite used (i.e. the
   cipher and hash functions used to encrypt/decrypt and to sign/verify
   packets).  The 8-bit Cipher Suite field is reserved for such purpose
   in the security material section of the Map-Request and Map-Reply
   messages.

   This document requests IANA to create and maintain a new registry (as
   outlined in [RFC5226]) entitled "LISP Crypto Cipher Suite".  Initial
   values for the registry are provided below.  Future assignments are
   to be made on a First Come First Served Basis.








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   +-----+--------------------------------------------+------------+
   |Value| Suite                                      | Definition |
   +-----+--------------------------------------------+------------+
   |  0  | Reserved                                   | Section 6  |
   +-----+--------------------------------------------+------------+
   |  1  | LISP_2048MODP_AES128_CBC_SHA256            | Section 6  |
   +-----+--------------------------------------------+------------+
   |  2  | LISP_EC25519_AES128_CBC_SHA256             | Section 6  |
   +-----+--------------------------------------------+------------+
   |  3  | LISP_2048MODP_AES128_GCM                   | Section 6  |
   +-----+--------------------------------------------+------------+
   |  4  | LISP_3072MODP_AES128_GCM M-3072            | Section 6  |
   +-----+--------------------------------------------+------------+
   |  5  | LISP_256_EC25519_AES128_GCM                | Section 6  |
   +-----+--------------------------------------------+------------+
   |  6  | LISP_256_EC25519_CHACHA20_POLY1305         | Section 6  |
   +-----+--------------------------------------------+------------+

                         LISP Crypto Cipher Suites

14.  References

14.1.  Normative References

   [LCAF]     Farinacci, D., Meyer, D., and J. Snijders, "LISP Canonical
              Address Format", draft-ietf-lisp-lcaf-13.txt (work in
              progress).

   [NIST-SP800-108]
              "National Institute of Standards and Technology,
              "Recommendation for Key Derivation Using Pseudorandom
              Functions NIST SP800-108"", NIST SP 800-108, October 2009.

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

   [RFC2631]  Rescorla, E., "Diffie-Hellman Key Agreement Method",
              RFC 2631, DOI 10.17487/RFC2631, June 1999,
              <http://www.rfc-editor.org/info/rfc2631>.

   [RFC3526]  Kivinen, T. and M. Kojo, "More Modular Exponential (MODP)
              Diffie-Hellman groups for Internet Key Exchange (IKE)",
              RFC 3526, DOI 10.17487/RFC3526, May 2003,
              <http://www.rfc-editor.org/info/rfc3526>.





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   [RFC4492]  Blake-Wilson, S., Bolyard, N., Gupta, V., Hawk, C., and B.
              Moeller, "Elliptic Curve Cryptography (ECC) Cipher Suites
              for Transport Layer Security (TLS)", RFC 4492,
              DOI 10.17487/RFC4492, May 2006,
              <http://www.rfc-editor.org/info/rfc4492>.

   [RFC5116]  McGrew, D., "An Interface and Algorithms for Authenticated
              Encryption", RFC 5116, DOI 10.17487/RFC5116, January 2008,
              <http://www.rfc-editor.org/info/rfc5116>.

   [RFC5226]  Narten, T. and H. Alvestrand, "Guidelines for Writing an
              IANA Considerations Section in RFCs", BCP 26, RFC 5226,
              DOI 10.17487/RFC5226, May 2008,
              <http://www.rfc-editor.org/info/rfc5226>.

   [RFC6090]  McGrew, D., Igoe, K., and M. Salter, "Fundamental Elliptic
              Curve Cryptography Algorithms", RFC 6090,
              DOI 10.17487/RFC6090, February 2011,
              <http://www.rfc-editor.org/info/rfc6090>.

   [RFC6830]  Farinacci, D., Fuller, V., Meyer, D., and D. Lewis, "The
              Locator/ID Separation Protocol (LISP)", RFC 6830,
              DOI 10.17487/RFC6830, January 2013,
              <http://www.rfc-editor.org/info/rfc6830>.

   [RFC6973]  Cooper, A., Tschofenig, H., Aboba, B., Peterson, J.,
              Morris, J., Hansen, M., and R. Smith, "Privacy
              Considerations for Internet Protocols", RFC 6973,
              DOI 10.17487/RFC6973, July 2013,
              <http://www.rfc-editor.org/info/rfc6973>.

   [RFC7539]  Nir, Y. and A. Langley, "ChaCha20 and Poly1305 for IETF
              Protocols", RFC 7539, DOI 10.17487/RFC7539, May 2015,
              <http://www.rfc-editor.org/info/rfc7539>.

14.2.  Informative References

   [AES-CBC]  McGrew, D., Foley, J., and K. Paterson, "Authenticated
              Encryption with AES-CBC and HMAC-SHA", draft-mcgrew-aead-
              aes-cbc-hmac-sha2-05.txt (work in progress).

   [CHACHA-POLY]
              Langley, A., "ChaCha20 and Poly1305 based Cipher Suites
              for TLS", draft-agl-tls-chacha20poly1305-04 (work in
              progress).






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   [CURVE25519]
              Bernstein, D., "Curve25519: new Diffie-Hellman speed
              records", Publication
              http://www.iacr.org/cryptodb/archive/2006/
              PKC/3351/3351.pdf.

   [DH]       "Diffie-Hellman key exchange", Wikipedia
              http://en.wikipedia.org/wiki/Diffie-Hellman_key_exchange.

   [LISP-DDT]
              Fuller, V., Lewis, D., Ermaagan, V., and A. Jain, "LISP
              Delegated Database Tree", draft-fuller-lisp-ddt-04 (work
              in progress).

   [LISP-SEC]
              Maino, F., Ermagan, V., Cabellos, A., and D. Saucez,
              "LISP-Secuirty (LISP-SEC)", draft-ietf-lisp-sec-10 (work
              in progress).

Appendix A.  Acknowledgments

   The authors would like to thank Dan Harkins, Joel Halpern, Fabio
   Maino, Ed Lopez, Roger Jorgensen, and Watson Ladd for their interest,
   suggestions, and discussions about LISP data-plane security.  An
   individual thank you to LISP WG chair Luigi Iannone for shepherding
   this document as well as contributing to the IANA Considerations
   section.

   The authors would like to give a special thank you to Ilari Liusvaara
   for his extensive commentary and discussion.  He has contributed his
   security expertise to make lisp-crypto as secure as the state of the
   art in cryptography.

   In addition, the support and suggestions from the SAAG working group
   were helpful and appreciative.

Appendix B.  Document Change Log

   [RFC Editor: Please delete this section on publication as RFC.]

B.1.  Changes to draft-ietf-lisp-crypto-10.txt

   o  Posted October 2016 after October 13th telechat.

   o  Addressed comments from Kathleen Moriarty, Stephen Farrel, and
      Pete Resnick.





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B.2.  Changes to draft-ietf-lisp-crypto-09.txt

   o  Posted October 2016.

   o  Addressed comments from OPs Directorate reviewer Susan Hares.

B.3.  Changes to draft-ietf-lisp-crypto-08.txt

   o  Posted September 2016.

   o  Addressed comments from Security Directorate reviewer Chris
      Lonvick.

B.4.  Changes to draft-ietf-lisp-crypto-07.txt

   o  Posted September 2016.

   o  Addressed comments from Routing Directorate reviewer Danny
      McPherson.

B.5.  Changes to draft-ietf-lisp-crypto-06.txt

   o  Posted June 2016.

   o  Fixed IDnits errors.

B.6.  Changes to draft-ietf-lisp-crypto-05.txt

   o  Posted June 2016.

   o  Update document which reflects comments Luigi provided as document
      shepherd.

B.7.  Changes to draft-ietf-lisp-crypto-04.txt

   o  Posted May 2016.

   o  Update document timer from expiration.

B.8.  Changes to draft-ietf-lisp-crypto-03.txt

   o  Posted December 2015.

   o  Changed cipher suite allocations.  We now have 2 AES-CBC cipher
      suites for compatibility, 3 AES-GCM cipher suites that are faster
      ciphers that include AE and a Chacha20-Poly1305 cipher suite which
      is the fastest but not totally proven/accepted..




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   o  Remove 1024-bit DH keys for key exchange.

   o  Make clear that AES and chacha20 ciphers use AEAD so part of
      encrytion/decryption does authentication.

   o  Make it more clear that separate key pairs are used in each
      direction between xTRs.

   o  Indicate that the IV length is different per cipher suite.

   o  Use a counter based IV for every packet for AEAD ciphers.
      Previously text said to use a random number.  But CBC ciphers, use
      a random number.

   o  Indicate that key material is sent in network byte order (big
      endian).

   o  Remove A-bit from Security Type LCAF.  No need to do
      authentication only with the introduction of AEAD ciphers.  These
      ciphers can do authentication.  So you get ciphertext for free.

   o  Remove language that refers to "encryption-key" and "integrity-
      key".  Used term "AEAD-key" that is used by the AEAD cipher suites
      that do encryption and authenticaiton internal to the cipher.

B.9.  Changes to draft-ietf-lisp-crypto-02.txt

   o  Posted September 2015.

   o  Add cipher suite for Elliptic Curve 25519 DH exchange.

   o  Add cipher suite for Chacha20/Poly1305 ciphers.

B.10.  Changes to draft-ietf-lisp-crypto-01.txt

   o  Posted May 2015.

   o  Create cipher suites and encode them in the Security LCAF.

   o  Add IV to beginning of packet header and ICV to end of packet.

   o  AEAD procedures are now part of encrpytion process.

B.11.  Changes to draft-ietf-lisp-crypto-00.txt

   o  Posted January 2015.





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   o  Changing draft-farinacci-lisp-crypto-01 to draft-ietf-lisp-crypto-
      00.  This draft has become a working group document

   o  Add text to indicate the working group may work on a new data
      encapsulation header format for data-plane encryption.

B.12.  Changes to draft-farinacci-lisp-crypto-01.txt

   o  Posted July 2014.

   o  Add Group-ID to the encoding format of Key Material in a Security
      Type LCAF and modify the IANA Considerations so this draft can use
      key exchange parameters from the IANA registry.

   o  Indicate that the R-bit in the Security Type LCAF is not used by
      lisp-crypto.

   o  Add text to indicate that ETRs/RTRs can negotiate less number of
      keys from which the ITR/PITR sent in a Map-Request.

   o  Add text explaining how LISP-SEC solves the problem when a man-in-
      the-middle becomes part of the Map-Request/Map-Reply key exchange
      process.

   o  Add text indicating that when RLOC-probing is used for RLOC
      reachability purposes and rekeying is not desired, that the same
      key exchange parameters should be used so a reallocation of a
      pubic key does not happen at the ETR.

   o  Add text to indicate that ECDH can be used to reduce CPU
      requirements for computing shared secret-keys.

B.13.  Changes to draft-farinacci-lisp-crypto-00.txt

   o  Initial draft posted February 2014.

Authors' Addresses

   Dino Farinacci
   lispers.net
   San Jose, California  95120
   USA

   Phone: 408-718-2001
   Email: farinacci@gmail.com






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   Brian Weis
   cisco Systems
   170 West Tasman Drive
   San Jose, California  95124-1706
   USA

   Phone: 408-526-4796
   Email: bew@cisco.com











































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