Network Working Group                                           F. Maino
Internet-Draft                                                V. Ermagan                                             Cisco Systems
Intended status: Standards Track                           Cisco Systems                              V. Ermagan
Expires: June 2, December 4, 2019                                         Google
                                                             A. Cabellos
                                    Universitat Politecnica de Catalunya
                                                               D. Saucez
                                                                   INRIA
                                                       November 29, 2018
                                                            June 2, 2019

                        LISP-Security (LISP-SEC)
                         draft-ietf-lisp-sec-17
                         draft-ietf-lisp-sec-18

Abstract

   This memo specifies LISP-SEC, a set of security mechanisms that
   provides origin authentication, integrity and anti-replay protection
   to LISP's EID-to-RLOC mapping data conveyed via mapping lookup
   process.  LISP-SEC also enables verification of authorization on EID-
   prefix claims in Map-Reply messages.

Requirements Language

   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]. BCP14 [RFC2119]
   [RFC8174] when, and only when, they appear in all capitals, as shown
   here.

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
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   This Internet-Draft will expire on June 2, December 4, 2019.

Copyright Notice

   Copyright (c) 2018 2019 IETF Trust and the persons identified as the
   document authors.  All rights reserved.

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Table of Contents

   1.  Introduction  . . . . . . . . . . . . . . . . . . . . . . . .   3
   2.  Definition of Terms . . . . . . . . . . . . . . . . . . . . .   3   4
   3.  LISP-SEC Threat Model . . . . . . . . . . . . . . . . . . . .   4
   4.  Protocol Operations . . . . . . . . . . . . . . . . . . . . .   5
   5.  LISP-SEC Control Messages Details . . . . . . . . . . . . . .   7
     5.1.  Encapsulated Control Message LISP-SEC Extensions  . . . .   7
     5.2.  Map-Reply LISP-SEC Extensions . . . . . . . . . . . . . .   9  10
     5.3.  Map-Register LISP-SEC Extentions  . . . . . . . . . . . .  11
     5.4.  ITR Processing Processing: Generating a Map-Request  . . . . . . . .  12
       5.4.1.  PITR Processing . . . . . . . . . . . . . .  11
       5.4.1.  Map-Reply Record Validation . . . . .  12
     5.5.  Encrypting and Decrypting an OTK  . . . . . . . .  13
       5.4.2.  PITR Processing . . . .  12
       5.5.1.  Unencrypted OTK . . . . . . . . . . . . . . . . . . .  14
     5.5.  Encrypting and Decrypting an OTK
     5.6.  Map-Resolver Processing . . . . . . . . . . . . . . . . .  14
     5.6.  Map-Resolver
     5.7.  Map-Server Processing . . . . . . . . . . . . . . . . . .  15
     5.7.  Map-Server Processing
       5.7.1.  Generating a LISP-SEC Protected Encapsulated Map-
               Request . . . . . . . . . . . . . . . . . .  15
       5.7.1.  Map-Server Processing in . . . . .  17
       5.7.2.  Generating a Proxy mode Map-Reply  . . . . . . . . . . .  16 .  18
     5.8.  ETR Processing  . . . . . . . . . . . . . . . . . . . . .  16  18
     5.9.  ITR Processing: Receiving a Map-Reply . . . . . . . . . .  18
       5.9.1.  Map-Reply Record Validation . . . . . . . . . . . . .  20
   6.  Security Considerations . . . . . . . . . . . . . . . . . . .  17  21
     6.1.  Mapping System Security . . . . . . . . . . . . . . . . .  17  21
     6.2.  Random Number Generation  . . . . . . . . . . . . . . . .  17  21
     6.3.  Map-Server and ETR Colocation . . . . . . . . . . . . . .  17  21
     6.4.  Deploying LISP-SEC  . . . . . . . . . . . . . . . . . . .  18  21
     6.5.  Shared Keys Provisioning  . . . . . . . . . . . . . . . .  18  22
     6.6.  Replay Attacks  . . . . . . . . . . . . . . . . . . . . .  18  22
     6.7.  Message Privacy . . . . . . . . . . . . . . . . . . . . .  19  22
     6.8.  Denial of Service and Distributed Denial of Service
           Attacks . . . . . . . . . . . . . . . . . . . . . . . . .  19  23
   7.  IANA Considerations . . . . . . . . . . . . . . . . . . . . .  19  23
     7.1.  ECM AD Type Registry  . . . . . . . . . . . . . . . . . .  19  23
     7.2.  Map-Reply AD Type Registry  . . . . . . . . . . . . . . .  19  23
     7.3.  HMAC Functions  . . . . . . . . . . . . . . . . . . . . .  20  24
     7.4.  Key Wrap Functions  . . . . . . . . . . . . . . . . . . .  20  24
     7.5.  Key Derivation Functions  . . . . . . . . . . . . . . . .  21  25
   8.  Acknowledgements  . . . . . . . . . . . . . . . . . . . . . .  21  25
   9.  References  . . . . . . . . . . . . . . . . . . . . . . . . .  25
     9.1.  Normative References  . . . . . . . . . . . . . . . . . .  25
     9.2.  Informative References  . .  21 . . . . . . . . . . . . . . .  27
   Authors' Addresses  . . . . . . . . . . . . . . . . . . . . . . .  23  27

1.  Introduction

   The Locator/ID Separation Protocol
   [I-D.ietf-lisp-rfc6830bis],[I-D.ietf-lisp-rfc6833bis] is a network-
   layer-based protocol that enables separation of IP addresses into two
   new numbering spaces: Endpoint Identifiers (EIDs) and Routing
   Locators (RLOCs).  EID-to-RLOC mappings are stored in a database, the
   LISP Mapping System, and made available via the Map-Request/Map-Reply
   lookup process.  If these EID-to-RLOC mappings, carried through Map-
   Reply messages, are transmitted without integrity protection, an
   adversary can manipulate them and hijack the communication,
   impersonate the requested EID, or mount Denial of Service or
   Distributed Denial of Service attacks.  Also, if the Map-Reply
   message is transported unauthenticated, an adversarial LISP entity
   can overclaim an EID-prefix and maliciously redirect traffic directed
   to a large number of hosts.  The LISP-SEC threat model, described in
   Section 3, is built on top of the LISP threat model defined in
   [RFC7835], that includes a detailed description of "overclaiming"
   attack.

   This memo specifies LISP-SEC, a set of security mechanisms that
   provides origin authentication, integrity and anti-replay protection
   to LISP's EID-to-RLOC mapping data conveyed via mapping lookup
   process.  LISP-SEC also enables verification of authorization on EID-
   prefix claims in Map-Reply messages, ensuring that the sender of a
   Map-Reply that provides the location for a given EID-prefix is
   entitled to do so according to the EID prefix registered in the
   associated Map-Server.  Map-Register  Map-Register/Map-Notify security, including
   the right for a LISP entity to register an EID-prefix or to claim
   presence at an RLOC, is out of the scope of LISP-SEC. LISP-SEC as those
   protocols are protected by the security mechanisms specified in
   [I-D.ietf-lisp-rfc6833bis].  However, LISP-SEC extends the Map-
   Register message to allow an ITR to securely downgrade to non LISP-
   SEC Map-Requests.  Additional security considerations are described
   in Section 6.

2.  Definition of Terms

      One-Time Key (OTK): An ephemeral randomly generated key that must
      be used for a single Map-Request/Map-Reply exchange.

      ITR One-Time Key (ITR-OTK): The One-Time Key generated at the ITR.
      Ingress Tunnel Router (ITR).

      MS One-Time Key (MS-OTK): The One-Time Key generated at the Map-
      Server.

      Authentication Data (AD): Metadata that is included either in a
      LISP Encapsulated Control Message (ECM) header, as defined in
      Section 6.1.8 of
      [I-D.ietf-lisp-rfc6833bis], or in a Map-Reply message to support
      confidentiality, integrity protection, and verification of EID-prefix EID-
      prefix authorization.

      OTK Authentication Data (OTK-AD): The portion of ECM
      Authentication Data that contains a One-Time Key.

      EID Authentication Data (EID-AD): The portion of ECM and Map-Reply
      Authentication Data used for verification of EID-prefix
      authorization.

      Packet Authentication Data (PKT-AD): The portion of Map-Reply
      Authentication Data used to protect the integrity of the Map-Reply
      message.

   For definitions of other terms, notably Map-Request, Map-Reply,
   Ingress Tunnel Router (ITR), Egress Tunnel Router (ETR), Map-Server
   (MS), and Map-Resolver (MR) please consult the LISP specification
   [I-D.ietf-lisp-rfc6833bis].

3.  LISP-SEC Threat Model

   LISP-SEC addresses the control plane threats, described in section
   3.7 and 3.8 of [RFC7835], that target EID-to-RLOC mappings, including
   manipulations of Map-Request and Map-Reply messages, and malicious
   ETR EID prefix overclaiming.  LISP-SEC makes two main assumptions:
   (1) the LISP mapping system is expected to deliver a Map-Request
   message to their intended destination ETR as identified by the EID,
   and (2) no man-in-the-middle (MITM) attack can be mounted within the
   LISP Mapping System.  How the Mapping System is protected from MITM
   attacks depends from the particular Mapping Systems used, and is out
   of the scope of this memo.  Furthermore, while LISP-SEC enables
   detection of EID prefix overclaiming attacks, it assumes that Map-
   Servers can verify the EID prefix authorization at time of
   registration.

   According to the threat model described in [RFC7835] LISP-SEC assumes
   that any kind of attack, including MITM attacks, can be mounted in
   the access network,
   outside of the boundaries of the LISP mapping system.  An on-path
   attacker, outside of the LISP mapping system can, for example, hijack
   Map-Request and Map-Reply messages, spoofing the identity of a LISP
   node.  Another example of on-path attack, called overclaiming attack,
   can be mounted by a malicious Egress Tunnel Router (ETR), by
   overclaiming the EID-prefixes for which it is authoritative.  In this
   way the ETR can maliciously redirect traffic directed to a large
   number of hosts.

4.  Protocol Operations

   The goal of the security mechanisms defined in
   [I-D.ietf-lisp-rfc6833bis] is to prevent unauthorized insertion of
   mapping data by providing origin authentication and integrity
   protection for the Map-Registration, Map-Register, and by using the nonce to detect
   unsolicited Map-Reply sent by off-path attackers.

   LISP-SEC builds on top of the security mechanisms defined in
   [I-D.ietf-lisp-rfc6833bis] to address the threats described in
   Section 3 by leveraging the trust relationships existing among the
   LISP entities participating to the exchange of the Map-Request/Map-
   Reply messages.  Those trust relationships are used to securely
   distribute
   distribute, as described in Section 7.4, a per-message One-Time Key
   (OTK) that provides origin authentication, integrity and anti-replay
   protection to mapping data conveyed via the mapping lookup process,
   and that effectively prevent overclaiming attacks.  The processing of
   security parameters during the Map-
   Request/Map-Reply Map-Request/Map-Reply exchange is as
   follows:

   o  The  Per each Map-Request message a new ITR-OTK is generated and stored
      at the ITR, and securely transported to the Map-Server.

   o  The Map-Server uses the ITR-OTK to compute a Keyed-Hashing for
      Message Authentication (HMAC) [RFC2104] that protects the
      integrity of the mapping data known to the Map-Server to prevent
      overclaiming attacks.  The Map-Server also derives a new OTK, the
      MS-OTK, that is passed to the ETR, by applying a Key Derivation
      Function (KDF) (e.g.  [RFC5869]) to the ITR-OTK.

   o  The ETR uses the MS-OTK to compute an HMAC that protects the
      integrity of the Map-Reply sent to the ITR.

   o  Finally, the ITR uses the stored ITR-OTK to verify the integrity
      of the mapping data provided by both the Map-Server and the ETR,
      and to verify that no overclaiming attacks were mounted along the
      path between the Map-Server and the ITR.

   Section 5 provides the detailed description of the LISP-SEC control
   messages and their processing, while the rest of this section
   describes the flow of LISP protocol operations at each entity
   involved in the Map-Request/Map-Reply exchange:

   o

   1.  The ITR, upon needing to transmit a Map-Request message,
       generates and stores an OTK (ITR-OTK).  This ITR-OTK is included
       into the Encapsulated Control Message (ECM) that contains the
       Map-Request sent to the Map-Resolver.  To provide  ITR-OTK confidentiality to the ITR-
      OTK over
       and integrity protection MUST be provided in the path between the
       ITR and its Map-Resolver, the ITR-
      OTK SHOULD Map-Resolver.  This can be encrypted using a preconfigured key shared between achieved either by
       encrypting the ITR and ITR-OTK with the Map-Resolver, similar pre-shared secret known to the key shared
       ITR and the Map-Resolver (as specified in Section 5.5), or by
       enabling DTLS between the ETR ITR and the Map-Server in order to secure ETR registration
      [I-D.ietf-lisp-rfc6833bis].

   o Map-Resolver.

   2.  The Map-Resolver decapsulates the ECM message, decrypts the ITR-
       OTK, if needed, and forwards through the Mapping System the
       received Map-Request and the ITR-OTK, as part of a new ECM
       message.  As described in Section 5.6, the  The LISP Mapping System delivers the ECM to the
       appropriate Map-Server, as identified by the EID destination
       address of the Map-Request.

   o  As mentioned in Section 3, how the
       Mapping System is protected from MITM attacks depends from the
       particular Mapping Systems used, and is out of the scope of this
       memo.

   3.  The Map-Server is configured with the location mappings and
       policy information for the ETR responsible for the EID
       destination address.  Using this preconfigured information, the
       Map-Server, after the decapsulation of the ECM message, finds the
       longest match EID-prefix that covers the requested EID in the
       received Map-Request.  The Map-Server adds this EID-prefix,
       together with an HMAC computed using the ITR-OTK, to a new
       Encapsulated Control Message that contains the received Map-Request.

   o Map-
       Request.

   4.  The Map-Server derives a new OTK, the MS-OTK, by applying a Key
       Derivation Function (KDF) to the ITR-OTK.  This MS-OTK is
       included in the Encapsulated Control Message that the Map-Server
       uses to forward the Map-Request to the ETR.  To provide  MS-OTK
       confidentiality over and integrity protection MUST be provided in the
       path between the Map-Server and the ETR, ETR.  This can be achieved
       either by encrypting the MS-OTK SHOULD be encrypted using with the key shared between pre-shared secret known
       to the
      ETR Map-Server and the Map-Server in order to secure ETR registration
      [I-D.ietf-lisp-rfc6833bis].

   o (as specified in Section 5.5), or
       by enabling DTLS between the Map-Server and the ETR.

   5.  If the Map-Server is acting in proxy mode, as specified in
       [I-D.ietf-lisp-rfc6833bis], the ETR is not involved in the
       generation of the Map-Reply. Map-Reply and steps 6 and 7 are skipped.  In
       this case the Map-Server generates the Map-Reply on behalf of the
       ETR as described below.

   o in Section 5.7.2.

   6.  The ETR, upon receiving the ECM encapsulated Map-Request from the
       Map-Server, decrypts the MS-OTK, if needed, and originates a
      standard Map-Reply Map-
       Reply that contains the EID-to-RLOC mapping information as
       specified in [I-D.ietf-lisp-rfc6833bis].

   o

   7.  The ETR computes an HMAC over this standard the Map-Reply, keyed with MS-OTK to
       protect the integrity of the whole Map-Reply.  The ETR also
       copies the EID-prefix authorization data that the Map-Server
       included in the ECM encapsulated Map-Request into the Map-Reply
       message.  The ETR then sends this the complete Map-Reply message to
       the requesting ITR.

   o

   8.  The ITR, upon receiving the Map-Reply, uses the locally stored
       ITR-OTK to verify the integrity of the EID-prefix authorization
       data included in the Map-Reply by the Map-Server.  The ITR
       computes the MS-OTK by applying the same KDF (as specified in the
       ECM encapsulated Map-Reply) used by the Map-
      Server, Map-Server, and verifies
       the integrity of the Map-Reply.  If the integrity checks fail,
       the Map-Reply MUST be discarded.  Also, if the EID-prefixes
       claimed by the ETR in the Map-Reply are not equal or more
       specific than the EID-prefix authorization data inserted by the
       Map-Server, the ITR MUST discard the Map-Reply.

5.  LISP-SEC Control Messages Details

   LISP-SEC metadata associated with a Map-Request is transported within
   the Encapsulated Control Message that contains the Map-Request.

   LISP-SEC metadata associated with the Map-Reply is transported within
   the Map-Reply itself.

5.1.  Encapsulated Control Message LISP-SEC Extensions

   LISP-SEC uses the ECM (Encapsulated Control Message) defined in [I-D.ietf-lisp-rfc6833bis] with Type set to 8, and S
   bit set to 1 to indicate that the LISP header includes Authentication
   Data (AD).  The format of the LISP-SEC ECM Authentication Data is
   defined in the
   following figure. Figure 1 . OTK-AD stands for One-Time Key Authentication
   Data and EID-AD stands for EID Authentication Data.

  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
 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
 |  ECM AD Type  |V|  Reserved  Unassigned |        Requested HMAC ID      |
 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+\
 |              OTK Length       |     Key ID    | OTK Encryption Wrap. ID  | |
 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ |
 |                       One-Time-Key Preamble ...               | |
 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+OTK-AD
 |                   ... One-Time-Key Preamble                   | |
 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ |
 ~                      One-Time Key (128 bits)                  ~/
 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ <---+
 |           EID-AD Length       |           KDF ID              |     |
 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+     |
 | Record Count  |    Reserved  |E| Unassigned  |         EID HMAC ID           |EID-AD
 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+\    |
 |   Reserved  Unassigned   | EID mask-len  |           EID-AFI             | |   |
 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ Rec |
 ~                          EID-prefix ...                       ~ |   |
 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+/    |
 ~                            EID HMAC                           ~     |
 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ <---+

                Figure 1: LISP-SEC ECM Authentication Data

      ECM AD Type: 1 (LISP-SEC Authentication Data).  See Section 7.

      V: Key Version bit.  This bit is toggled when the sender switches
      to a new OTK wrapping key

      Reserved:

      Unassigned: Set to 0 on transmission and ignored on receipt.

      Requested HMAC ID: The HMAC algorithm algorithm, that will be used to
      protect the mappings, requested by the ITR.  See Section 5.4 for details.
      details, and Section 7.3 for HMAC IDs that MUST be supported.

      OTK Length: The length (in bytes) of the OTK Authentication Data
      (OTK-AD), that contains the OTK Preamble and the OTK.

      OTK Encryption

      Key ID: The identifier of the key wrapping algorithm
      used to encrypt the One-Time-Key. When a 128-bit OTK is sent
      unencrypted pre-shared secret shared by an ITR
      and the Map-Resolver, and by the OTK Encryption ID is set Map-Server and an ETR.  Per-
      message keys are derived from the pre-shared secret to
      NULL_KEY_WRAP_128.  See Section 5.5 for more details.

      One-Time-Key Preamble: encrypt,
      authenticate the origin and protect the integrity of the OTK.  The
      Key ID allows to rotate between multiple pre-shared secrets in a
      non disruptive way.

      OTK Wrapping ID: The identifier of the key derivation function and
      of the key wrapping algorithm used to encrypt the One-Time-Key.
      See Section 5.5 for more details, and Section 7.4 for Wrapping IDs
      that MUST be supported.

      One-Time-Key Preamble: set to 0 if the OTK is not encrypted.  When
      the OTK is encrypted, this field MAY carry additional metadata
      resulting from the key wrapping operation.  When a 128-bit OTK is
      sent unencrypted by Map-Resolver, the OTK Preamble is set to
      0x0000000000000000 (64 bits).  See Section 5.5 5.5.1 for details.

      One-Time-Key: the OTK encrypted (or not) wrapped as specified by OTK
      Encryption Wrapping ID.
      See Section 5.5 for details.

      EID-AD Length: length (in bytes) of the EID Authentication Data
      (EID-AD).  The ITR MUST set EID-AD Length to 4 bytes, as it only
      fills the KDF ID field, and all the remaining fields part of the
      EID-AD are not present.  An EID-AD MAY contain multiple EID-
      records.  Each EID-record is 4-byte long plus the length of the
      AFI-encoded EID-prefix.

      KDF ID: Identifier of the Key Derivation Function used to derive
      the MS-OTK.  The ITR MAY use this field to indicate the
      recommended KDF algorithm, according to local policy.  The Map-
      Server can overwrite the KDF ID if it does not support the KDF ID
      recommended by the ITR.  See Section 5.4 for more details. details, and
      Section 7.5 for KDF IDs that MUST be supported.

      Record Count: The number of records in this Map-Request message.
      A record is comprised of the portion of the packet that is labeled
      'Rec' above and occurs the number of times equal to Record Count.

      Reserved:

      E: ETR-Cant-Sign bit.  This bit is set to 1 to signal to the ITR
      that at least one of the ETRs authoritative for the EID prefixes
      of this Map-Reply has not enabled LISP-SEC.  This allows the ITR
      to securely downgrade to non LISP-SEC requests, as specified in
      Section 5.7, if so desired.

      Unassigned: Set to 0 on transmission and ignored on receipt.

      EID HMAC ID: Identifier of the HMAC algorithm used to protect the
      integrity of the EID-AD.  This field is filled by Map-Server that
      computed the EID-prefix HMAC.  See Section 5.4 for more details. details,
      and Section 7.3 for HMAC IDs that MUST be supported.

      EID mask-len: Mask length for EID-prefix.

      EID-AFI: Address family of EID-prefix according to [RFC5226]
      EID-prefix: The Map-Server uses this field to specify the EID-
      prefix that the destination ETR is authoritative for, and is the
      longest match for the requested EID.

      EID HMAC: HMAC of the EID-AD computed and inserted by Map-Server.
      Before computing the HMAC operation the EID HMAC field MUST be set
      to 0.  The HMAC covers MUST cover the entire EID-AD.

5.2.  Map-Reply LISP-SEC Extensions

   LISP-SEC uses the Map-Reply defined in [I-D.ietf-lisp-rfc6833bis],
   with Type set to 2, and S bit S-bit set to 1 to indicate that the Map-Reply
   message includes Authentication Data (AD).  The format of the LISP-
   SEC Map-Reply Authentication Data is defined in the following figure. Figure 2.  PKT-AD is
   the Packet Authentication Data that covers the Map-Reply payload.

  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
 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
 |  MR AD Type   |                 Reserved                Unassigned                     |
 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ <---+
 |           EID-AD Length       |           KDF ID              |     |
 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+     |
 | Record Count  |    Reserved   Unassigned  |         EID HMAC ID           |EID-AD
 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+\    |
 |   Reserved  Unassigned   | EID mask-len  |           EID-AFI             | |   |
 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ Rec |
 ~                          EID-prefix ...                       ~ |   |
 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+/    |
 ~                            EID HMAC                           ~     |
 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ <---+
 |         PKT-AD Length         |         PKT HMAC ID           |\
 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ |
 ~                            PKT HMAC                           ~PKT-AD
 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+/

             Figure 2: LISP-SEC Map-Reply Authentication Data

      MR AD Type: 1 (LISP-SEC Authentication Data).  See Section 7.

      EID-AD Length: length (in bytes) of the EID-AD.  An EID-AD MAY
      contain multiple EID-records.  Each EID-record is 4-byte long plus
      the length of the AFI-encoded EID-prefix.

      KDF ID: Identifier of the Key Derivation Function used to derive
      MS-OTK.  See Section 5.7 for more details. details, and Section 7.5 for KDF
      IDs that MUST be supported.

      Record Count: The number of records in this Map-Reply message.  A
      record is comprised of the portion of the packet that is labeled
      'Rec' above and occurs the number of times equal to Record Count.

      Reserved:

      Unassigned: Set to 0 on transmission and ignored on receipt.

      EID HMAC ID: Identifier of the HMAC algorithm used to protect the
      integrity of the EID-AD.  See Section 5.7 for more details. details, and
      Section 7.3 for HMAC IDs that MUST be supported.

      EID mask-len: Mask length for EID-prefix.

      EID-AFI: Address family of EID-prefix according to [RFC5226]. [RFC8060].

      EID-prefix: This field contains an EID-prefix that the destination
      ETR is authoritative for, and is the longest match for the
      requested EID.

      EID HMAC: HMAC of the EID-AD, as computed by the Map-Server.
      Before computing the HMAC operation the EID HMAC field MUST be set
      to 0.  The HMAC covers the entire EID-AD.

      PKT-AD Length: length (in bytes) of the Packet Authentication Data
      (PKT-AD).

      PKT HMAC ID: Identifier of the HMAC algorithm used to protect the
      integrity of the Map-reply. Map-Reply.  See Section 7.3 for HMAC IDs that
      MUST be supported.

      PKT HMAC: HMAC of the whole Map-Reply packet, including the LISP-
      SEC Authentication Data.  The scope of the authentication goes
      from the Map-Reply Type field to the PKT HMAC field included.
      Before computing the HMAC operation the PKT HMAC field MUST be set
      to 0.  See Section 5.8 for more details.

5.3.  Map-Register LISP-SEC Extentions

   This memo is allocating one of the bits marked as Reserved Unassigned in the
   Map-Register message defined in Section 6.1.6 of [I-D.ietf-lisp-rfc6833bis].  More
   precisely, the second bit after the Type field in a Map-Register
   message is allocated as the S bit.  The S bit indicates to the Map-Server Map-
   Server that the registering ETR is LISP-
   SEC LISP-SEC enabled.  An ETR that
   supports LISP-SEC MUST set the S bit in its Map-Register messages.

5.4.  ITR Processing Processing: Generating a Map-Request

   Upon creating a Map-Request, the ITR generates a random ITR-OTK that
   is stored locally, locally (until the corresponding Map-Reply is received),
   together with the nonce generated as specified in
   [I-D.ietf-lisp-rfc6833bis].

   ITR-OTK confidentiality and integrity protection MUST be provided in
   the path between the ITR and the Map-Resolver.  This can be achieved
   either by encrypting the ITR-OTK with the pre-shared secret known to
   the ITR and the Map-Resolver (see Section 5.5), or by enabling DTLS
   between the ITR and the Map-Resolver.

   The Map-Request MUST be encapsulated in an ECM, with the S-bit set to
   1, to indicate the presence of Authentication Data.  If the ITR and
   the Map-Resolver are configured with a shared key, the ITR-OTK
   confidentiality SHOULD be protected by wrapping the

   ITR-OTK is wrapped with the algorithm specified by the OTK Encryption Wrapping
   ID field.  See Section 5.5 for further details on OTK encryption.

   The Requested HMAC ID field contains  If
   the suggested HMAC NULL-KEY-WRAP-128 algorithm to
   be used by the Map-Server is selected and DTLS is not enabled
   in the path between the ITR and the Map-Resolver, the Map-Request
   MUST be dropped and an appropiate log action SHOULD be taken.

   The Requested HMAC ID field contains the suggested HMAC algorithm to
   be used by the Map-Server and the ETR to protect the integrity of the
   ECM Authentication data and of the Map-Reply.

   The KDF ID field specifies the suggested key derivation function to
   be used by the Map-Server to derive the MS-OTK.  A KDF Value of NONE
   (0), MAY be used to specify that the ITR has no preferred KDF ID.

   The EID-AD length is set to 4 bytes, since the Authentication Data
   does not contain EID-prefix Authentication Data, and the EID-AD
   contains only the KDF ID field.

   In response

5.4.1.  PITR Processing

   The processing performed by a PITR is equivalent to an encapsulated Map-Request that has the S-bit set, processing of
   an
   ITR MUST receive ITR.  However, if the PITR is directly connected to a Map-Reply with Mapping
   System such as LISP+ALT [RFC6836], the S-bit set, PITR performs the functions of
   both the ITR and the Map-Resolver forwarding the Map-Request
   encapsulated in an ECM header that includes the Authentication Data
   fields as described in Section 5.6.

5.5.  Encrypting and Decrypting an
   EID-AD OTK

   MS-OTK confidentiality and a PKT-AD.  If integrity protection MUST be provided in
   the Map-Reply does not include both ADs, path between the
   ITR MUST discard it.  In response to an encapsulated Map-Request with
   S-bit set to 0, Map-Server and the ITR expects a Map-Reply with S-bit set to 0, ETR.  This can be achieved
   either by enabling DTLS between the Map-Server and the ITR SHOULD discard or by
   encrypting the Map-Reply if MS-OTK with the S-bit is set.

   Upon receiving a Map-Reply, pre-shared secret known to the ITR must verify Map-
   Server and the ETR [I-D.ietf-lisp-rfc6833bis].

   Similarly, ITR-OTK confidentiality and integrity of both protection MUST be
   provided in the EID-AD path between the ITR and the PKT-AD, Map-Resolver.  This can
   be achieved either by enabling DTLS between the Map-Server and MUST discard the Map-Reply if one of
   ITR, or by encrypting the integrity checks fails.  After processing ITR-OTK with the Map-Reply, pre-shared secret known to
   the ITR
   must discard and the <nonce,ITK-OTK> pair associated Map-Resolver.  The ITR/Map-Resolver pre-shared key is
   similar to the Map-Reply

   The integrity of Map-Server/ETR pre-shared key.  However, to prevent
   ETR's overclaiming attacks, the EID-AD is verified using ITR/Map-Resolver pre-shared secret
   MUST have a different value than the locally stored ITR- Map-Server/ETR pre-shared
   secret.

   This section describes OTK processing in the ITR/Map-Resolver path,
   as well as in the Map-Server/ETR path.

   It's important to re-compute note that, to prevent ETR's overclaiming attacks,
   the HMAC of ITR/Map-Resolver pre-shared secret MUST be different from the EID-AD
   Map-Server/ETR pre-shared secret.

   The OTK is wrapped using the algorithm specified in the EID HMAC OTK Wrapping
   ID field.  If the EID HMAC ID  This field does
   not match identifies both the:

   o  Key Encryption Algorithm used to encrypt the Requested HMAC ID wrapped OTK, as well
      as the ITR SHOULD discard

   o  Key Derivation Function used to derive a per-message encryption
      key.

   Implementations of this specification MUST support OTK Wrapping ID
   AES-KEY-WRAP-128+HKDF-SHA256 that specifies the Map-Reply
   and send, at use of the first opportunity it needs to, HKDF-
   SHA256 Key Derivation Function specified in[RFC4868] to derive a new Map-Request
   with per-
   message encryption key (per-msg-key), as well as the AES-KEY-WRAP-128
   Key Wrap algorithm used to encrypt a different Requested HMAC ID field, 128-bit OTK, according to ITR's local
   policy.
   [RFC3394].

   The scope of key wrapping process for OTK Wrapping ID AES-KEY-WRAP-128+HKDF-
   SHA256 is described below:

   1.  The KDF algorithm is identified by the HMAC operation covers field 'OTK Wrapping ID'
       according to the entire EID-AD,
   from table in Section Section 7.4.

   2.  The Key Wrap algorithm is identified by the EID-AD Length field 'OTK Wrapping
       ID' according to the EID HMAC field, which must be set
   to 0 before table in Section Section 7.4.

   3.  If the computation of NULL-KEY-WRAP-128 algorithm (defined in (Section 7.4)) is
       selected and DTLS is not enabled, the HMAC.

   ITR Map-Request MUST set the EID HMAC ID field be dropped
       and an appropiate log action SHOULD be taken.

   4.  The pre-shared secret used to 0 before computing derive the HMAC.

   To verify per-msg-key is
       represented by PSK[Key ID], that is the integrity of pre-shared secret
       identified by the PKT-AD, first 'Key ID'.

   5.  The per-message encryption key key is computed as:

       *  per-msg-key = KDF( nonce + s + PSK[Key ID] )

       *  where the MS-OTK nonce is derived
   from the locally stored ITR-OTK using the algorithm specified value in the
   KDF ID field.  This is because Nonce field of the PKT-AD Map-
          Request, and

       *  's' is generated by the ETR
   using string "OTK-Key-Wrap"

   6.  According to [RFC3394] the MS-OTK.  If per-msg-key is used to wrap the KDF ID OTK
       with AES-KEY-WRAP-128.  The AES Key Wrap Initialization Value
       MUST be set to 0xA6A6A6A6A6A6A6A6 (64 bits).  The output of the
       AES Key Wrap operation is 192-bit long.  The most significant
       64-bit are copied in the Map-Reply does not match One-Time Key Preamble field, while the
   KDF ID requested
       128 less significant bits are copied in the Map-Request, One-Time Key field of
       the ITR SHOULD discard LISP-SEC Authentication Data.

   When decrypting an encrypted OTK the Map-
   Reply and send, at receiver MUST verify that the first opportunity it needs to, a new Map-
   Request with a different KDF ID, according to ITR's local policy.

   The derived MS-OTK
   Initialization Value resulting from the AES Key Wrap decryption
   operation is then used equal to re-compute the HMAC of 0xA6A6A6A6A6A6A6A6.  If this verification fails
   the PKT-AD
   using receiver MUST discard the Algorithm specified entire message.

5.5.1.  Unencrypted OTK

   MS-OTK confidentiality and integrity protection MUST be provided in
   the PKT HMAC ID field.  If path between the PKT
   HMAC ID field does not match Map-Server and the Requested HMAC ID ETR.  Similarly, ITR-OTK
   confidentiality and integrity protection MUST be provided in the ITR SHOULD
   discard path
   between the Map-Reply ITR and send, at the first opportunity it needs to,
   a new Map-Request with Map-Resolver.

   However, when DTLS is enabled the OTK MAY be sent unencrypted as
   transport layer security is providing confidentiality and integrity
   protection.

   When a different Requested HMAC 128-bit OTK is sent unencrypted the OTK Wrapping ID according is set to
   ITR's local policy or until all HMAC IDs supported by the ITR have
   been attempted.

   Each individual Map-Reply EID-record is considered valid only if: (1)
   both EID-AD and PKT-AD are valid,
   NULL_KEY_WRAP_128, and (2) the intersection of the
   EID-prefix in the Map-Reply EID-record OTK Preamble is set to 0x0000000000000000
   (64 bits).

5.6.  Map-Resolver Processing

   Upon receiving an encapsulated Map-Request with one of the EID-prefixes
   contained in S-bit set, the EID-AD is not empty.  After identifying
   Map-Resolver decapsulates the Map-
   Reply record ECM message.  The ITR-OTK, if
   encrypted, is decrypted as valid, the ITR sets the EID-prefix specified in Section 5.5.

   Protecting the Map-Reply
   record to the value confidentiality of the intersection set computed before, and adds
   the Map-Reply EID-record to its EID-to-RLOC cache, as described ITR-OTK and, in
   [I-D.ietf-lisp-rfc6833bis].  An example general, the
   security of Map-Reply record
   validation how the Map-Request is provided in Section 5.4.1.

   The ITR SHOULD send SMR triggered Map-Requests over handed by the mapping
   system in order Map-Resolver to receive a secure Map-Reply.  If an ITR accepts
   piggybacked Map-Replies, it SHOULD also send a Map-Request over the
   mapping system in order
   Map-Server, is specific to verify the piggybacked Map-Reply with a
   secure Map-Reply.

5.4.1.  Map-Reply Record Validation

   The payload particular Mapping System used, and
   outside of a Map-Reply may contain multiple EID-records.  The
   whole Map-Reply the scope of this memo.

   In Mapping Systems where the Map-Server is signed by compliant with
   [I-D.ietf-lisp-rfc6833bis], the ETR, Map-Resolver originates a new ECM
   header with the PKT HMAC, to provide
   integrity protection S-bit set, that contains the unencrypted ITR-OTK, as
   specified in Section 5.5, and origin authentication to the EID-prefix
   records claimed by other data derived from the ETR.  The ECM
   Authentication Data field of a Map-
   Reply may contain multiple EID-records in the EID-AD. received encapsulated Map-Request.

   The EID-AD is
   signed by Map-Resolver then forwards to the Map-Server, with Map-Server the EID HMAC, to provide integrity
   protection and origin authentication to received Map-
   Request, encapsulated in the EID-prefix records
   inserted by new ECM header that includes the Map-Server. newly
   computed Authentication Data fields.

5.7.  Map-Server Processing

   Upon receiving a Map-Reply an ECM encapsulated Map-Request with the S-bit set, the ITR first checks set to
   1, the validity of both Map-Server process the EID HMAC and of Map-Request according to the PKT-AD HMAC.  If either
   one value of
   the HMACs is not valid, a log action MUST be taken security-capable S-bit and of the
   Map-Reply MUST NOT be processed any further.  If both HMACs are
   valid, the ITR proceeds with validating each individual EID-record
   claimed by proxy map-reply P-bit contained
   in the ETR Map-Register sent by computing the intersection of each one ETRs authoritative for that prefix
   during registration.

   Processing of the
   EID-prefix contained Map-Request MUST proceed in the payload of order described in
   the Map-Reply with each one of table below, applying the EID-prefixes contained processing corresponding to the first
   rule that matches the conditions indicated in the EID-AD.  An EID-record is valid
   only if at first column:

   +----------------+--------------------------------------------------+
   | Matching       | Processing                                       |
   | Condition      |                                                  |
   +----------------+--------------------------------------------------+
   | 1. At least    | The Map-Server MUST generate a LISP-SEC          |
   | one of the intersections is not the empty set.

   For instance, the     | protected Map-Reply payload contains 3 mapping record EID-
   prefixes:

      2001:db8:0102::/48

      2001:db8:0103::/48

      2001:db8:0200::/40

   The EID-AD contains two EID-prefixes:

      2001:db8:0103::/48

      2001:db8:0203::/48 as specified in Section      |
   | ETRs           | 5.7.2. The EID-record with EID-prefix 2001:db8:0102::/48 is not eligible to
   be used by the ITR since it is not included ETR-Cant-Sign E-bit in any of the EID-ADs
   signed by the Map-Server.  A log action EID        |
   | authoritative  | Authentication Data (EID-AD) MUST be taken.

   The EID-record with set to 0.   |
   | for the EID    |                                                  |
   | prefix         |                                                  |
   | included in    |                                                  |
   | the Map-       |                                                  |
   | Request        |                                                  |
   | registered     |                                                  |
   | with the P-bit |                                                  |
   | set to 1       |                                                  |
   |                |                                                  |
   | 2. At least    | The Map-Server MUST generate a LISP-SEC          |
   | one of the     | protected Encapsulated Map-Request (as specified |
   | ETRs           | in Section 5.7.1), to be sent to one of the      |
   | authoritative  | authoritative ETRs that registered with the      |
   | for the EID    | S-bit set to 1 (and the P-bit set to 0). If      |
   | prefix         | there is at least one ETR that registered with   |
   | included in    | the S-bit set to 0, the ETR-Cant-Sign E-bit of   |
   | the Map-       | the EID-AD MUST be set to 1 to signal the ITR    |
   | Request        | that a non LISP-SEC Map-Request might reach      |
   | registered     | additional ETRs that have LISP-SEC disabled.     |
   | with the S-bit |                                                  |
   | set to 1       |                                                  |
   |                |                                                  |
   | 3. All the     | The Map-Server MUST send a Negative Map-Reply    |
   | ETRs           | protected with LISP-SEC, as described in Section |
   | authoritative  | 5.7.2. The ETR-Cant-Sign E-bit MUST be set to 1  |
   | for the EID    | to signal the ITR that a non LISP-SEC Map-       |
   | prefix         | Request might reach additional ETRs that have    |
   | included in    | LISP-SEC disabled.                               |
   | the Map-       |                                                  |
   | Request        |                                                  |
   | registered     |                                                  |
   | with the S-bit |                                                  |
   | set to 0       |                                                  |
   +----------------+--------------------------------------------------+

   In this way the ITR that sent a LISP-SEC protected Map-Request always
   receives a LISP-SEC protected Map-Reply.  However, the ETR-Cant-Sign
   E-bit set to 1 specifies that a non LISP-SEC Map-Request might reach
   additional ETRs that have LISP-SEC disabled.  This mechanism allows
   the ITR to securely downgrade to non LISP-SEC requests, if so
   desired.

5.7.1.  Generating a LISP-SEC Protected Encapsulated Map-Request

   The Map-Server decapsulates the ECM and generates a new ECM
   Authentication Data.  The Authentication Data includes the OTK-AD and
   the EID-AD, that contains EID-prefix 2001:db8:0103::/48 authorization information, that
   are eventually received by the requesting ITR.

   The Map-Server updates the OTK-AD by deriving a new OTK (MS-OTK) from
   the ITR-OTK received with the Map-Request.  MS-OTK is eligible derived
   applying the key derivation function specified in the KDF ID field.
   If the algorithm specified in the KDF ID field is not supported, the
   Map-Server uses a different algorithm to derive the key and updates
   the KDF ID field accordingly.

   MS-OTK confidentiality and integrity protection MUST be
   used provided in
   the path between the Map-Server and the ETR.  This can be achieved
   either by enabling DTLS between the ITR because it matches Map-Server and the second EID-prefix contained in ETR, or by
   encrypting the EID-AD.

   The EID-record MS-OTK with EID-prefix 2001:db8:0200::/40 is not eligible the pre-shared secret known to the Map-
   Server and the ETR.

   The Map-Request MUST be used encapsulated in an ECM, with the S-bit set to
   1, to indicate the presence of Authentication Data.

   MS-OTK is wrapped with the algorithm specified by the ITR since it OTK Wrapping ID
   field.  See Section 5.5 for further details on OTK encryption.  If
   the NULL-KEY-WRAP-128 algorithm is selected and DTLS is not included enabled
   in any of the EID-ADs
   signed by path between the Map-Server.  A Map-Server and the ETR, the Map-Request MUST
   be dropped and an appropiate log action MUST SHOULD be taken.  In this last
   example

   The Map-Server includes in the ETR is trying to over claim EID-AD the longest match registered
   EID-prefix
   2001:db8:0200::/40, but for the Map-Server authorized only
   2001:db8:0203::/48, hence destination EID, and an HMAC of this EID-prefix.
   The HMAC is keyed with the EID-record ITR-OTK contained in the received ECM
   Authentication Data, and the HMAC algorithm is discarded.

5.4.2.  PITR Processing chosen according to
   the Requested HMAC ID field.  If The processing performed by Map-Server does not support this
   algorithm, the Map-Server uses a PITR is equivalent to different algorithm and specifies it
   in the processing EID HMAC ID field.  The scope of
   an ITR.  However, if the PITR is directly connected to a Mapping
   System such as LISP+ALT [RFC6836], HMAC operation covers the PITR performs
   entire EID-AD, from the functions of
   both EID-AD Length field to the ITR and EID HMAC field,
   which must be set to 0 before the Map-Resolver forwarding computation.

   The Map-Server then forwards the Map-Request
   encapsulated in an updated ECM header encapsulated Map-
   Request, that includes contains the Authentication Data
   fields as described in Section 5.6.

5.5.  Encrypting OTK-AD, the EID-AD, and Decrypting the received Map-
   Request to an OTK

   MS-OTK confidentiality is required authoritative ETR as specified in
   [I-D.ietf-lisp-rfc6833bis].

5.7.2.  Generating a Proxy Map-Reply

   LISP-SEC proxy Map-Reply are generated according to
   [I-D.ietf-lisp-rfc6833bis], with the path between the Map-Server
   and Map-Replay S-bit set to 1.  The
   Map-Reply includes the ETR, Authentication Data that contains the MS-OTK SHOULD be encrypted using EID-AD,
   computed as specified in Section 5.7.1, as well as the preconfigured
   key shared between PKT-AD
   computed as specified in Section 5.8.

5.8.  ETR Processing

   Upon receiving an ECM encapsulated Map-Request with the Map-Server and S-bit set,
   the ETR for decapsulates the purpose of
   securing ETR registration [I-D.ietf-lisp-rfc6833bis].  Similarly, ECM message.  The OTK field, if
   ITR-OTK confidentiality encrypted,
   is required decrypted as specified in Section 5.5 to obtain the path between the ITR unencrypted
   MS-OTK.

   The ETR then generates a Map-Reply as specified in
   [I-D.ietf-lisp-rfc6833bis] and includes the Map-Resolver, Authentication Data that
   contains the ITR-OTK SHOULD be encrypted with a key shared
   between EID-AD, as received in the ITR and encapsulated Map-Request, as
   well as the Map-Resolver. PKT-AD.

   The OTK EID-AD is encrypted copied from the Authentication Data of the received
   encapsulated Map-Request.

   The PKT-AD contains the HMAC of the whole Map-Reply packet, keyed
   with the MS-OTK and computed using the HMAC algorithm specified in
   the OTK
   Encryption Requested HMAC ID field.  When field of the AES Key Wrap algorithm is used to
   encrypt received encapsulated Map-Request.
   If the ETR does not support the Requested HMAC ID, it uses a 128-bit OTK, according to [RFC3394],
   different algorithm and updates the AES Key Wrap
   Initialization Value MUST be set to 0xA6A6A6A6A6A6A6A6 (64 bits). PKT HMAC ID field accordingly.
   The output scope of the AES Key Wrap HMAC operation is 192-bit long.  The most
   significant 64-bit are copied in the One-Time Key Preamble field,
   while covers the 128 less significant bits are copied in entire PKT-AD, from the One-Time Key
   Map-Reply Type field of to the LISP-SEC Authentication Data.

   When decrypting an encrypted OTK PKT HMAC field, which must be set to 0
   bendlfore the receiver MUST verify that computation.

   Finally the
   Initialization Value resulting from ETR sends the AES Key Wrap decryption
   operation is equal Map-Reply to 0xA6A6A6A6A6A6A6A6.  If this verification fails the receiver MUST discard requesting ITR as
   specified in [I-D.ietf-lisp-rfc6833bis].

5.9.  ITR Processing: Receiving a Map-Reply

   In response to an encapsulated Map-Request that has the entire message.

   When S-bit set, an
   ITR MUST receive a 128-bit OTK is sent unencrypted Map-Reply with the OTK Encryption ID is set
   to NULL_KEY_WRAP_128, S-bit set, that includes an
   EID-AD and a PKT-AD.  If the OTK Preamble is set Map-Reply does not include both ADs, the
   ITR MUST discard it.  In response to
   0x0000000000000000 (64 bits).

5.6.  Map-Resolver Processing

   Upon receiving an encapsulated Map-Request with
   S-bit set to 0, the ITR expects a Map-Reply with S-bit set, set to 0, and
   the
   Map-Resolver decapsulates ITR SHOULD discard the ECM message.  The ITR-OTK, Map-Reply if
   encrypted, the S-bit is decrypted as specified in Section 5.5.

   Protecting set.

   Upon receiving a Map-Reply, the confidentiality ITR must verify the integrity of both
   the ITR-OTK and, in general, EID-AD and the
   security PKT-AD, and MUST discard the Map-Reply if one of how
   the Map-Request is handed by integrity checks fails.  After processing the Map-Resolver to Map-Reply, the
   Map-Server, is specific ITR
   must discard the <nonce,ITK-OTK> pair associated to the particular Mapping System used, and
   outside Map-Reply
   The integrity of the scope EID-AD is verified using the ITR-OTK (stored
   locally for the duration of this memo.

   In Mapping Systems where the Map-Server is compliant with
   [I-D.ietf-lisp-rfc6833bis], exchange) to re-compute the Map-Resolver originates a new ECM
   header with HMAC of
   the S-bit set, that contains EID-AD using the unencrypted ITR-OTK, as algorithm specified in Section 5.5, and the other data derived from EID HMAC ID field.
   If the ECM
   Authentication Data of EID HMAC ID field does not match the received encapsulated Map-Request.

   The Map-Resolver then forwards to Requested HMAC ID the Map-Server ITR
   SHOULD discard the received Map-
   Request, encapsulated in Map-Reply and send, at the first opportunity it
   needs to, a new ECM header that includes the newly
   computed Authentication Data fields.

5.7.  Map-Server Processing

   Upon receiving an ECM encapsulated Map-Request with a different Requested HMAC ID field,
   according to ITR's local policy.  The scope of the S-bit set, HMAC operation
   covers the Map-Server process entire EID-AD, from the Map-Request according EID-AD Length field to the value EID
   HMAC field, which must be set to 0 before the computation of the
   S-bit contained
   HMAC.

   ITR MUST set the EID HMAC ID field to 0 before computing the HMAC.

   To verify the integrity of the PKT-AD, first the MS-OTK is derived
   from the locally stored ITR-OTK using the algorithm specified in the Map-Register sent
   KDF ID field.  This is because the PKT-AD is generated by the ETR during
   registration.

   If the S-bit contained in the Map-Register was clear
   using the Map-Server
   decapsulates MS-OTK.  If the ECM and generates a new ECM encapsulated Map-Request
   that does not contain an ECM Authentication Data, as specified KDF ID in
   [I-D.ietf-lisp-rfc6833bis].  The Map-Server does not perform any
   further LISP-SEC processing, and the Map-Reply will does not be protected.

   If match the S-bit contained
   KDF ID requested in the Map-Register was set the Map-Server
   decapsulates Map-Request, the ECM and generates a new ECM Authentication Data.
   The Authentication Data includes ITR SHOULD discard the OTK-AD Map-
   Reply and send, at the EID-AD, that
   contains EID-prefix authorization information, that are ultimately
   sent to the requesting ITR.

   The Map-Server updates the OTK-AD by deriving first opportunity it needs to, a new OTK (MS-OTK) from
   the ITR-OTK received Map-
   Request with a different KDF ID, according to ITR's local policy.
   Without consistent configuration of involved entities, extra delays
   may be experienced.  However, since HKDF-SHA1-128 is specified as
   mandatory to implement in Section 7.5, the Map-Request. process will eventually
   converge.

   The derived MS-OTK is derived
   applying then used to re-compute the key derivation function HMAC of the PKT-AD
   using the Algorithm specified in the KDF PKT HMAC ID field.  If the algorithm specified in the KDF PKT
   HMAC ID field is does not supported, match the
   Map-Server uses a different algorithm to derive Requested HMAC ID the key and updates ITR SHOULD
   discard the KDF ID field accordingly.

   The Map-Server Map-Reply and send, at the ETR MUST be configured first opportunity it needs to,
   a new Map-Request with a shared key for
   mapping registration different Requested HMAC ID according to [I-D.ietf-lisp-rfc6833bis].  If MS-
   OTK confidentiality
   ITR's local policy or until all HMAC IDs supported by the ITR have
   been attempted.

   Each individual Map-Reply EID-record is required, then considered valid only if: (1)
   both EID-AD and PKT-AD are valid, and (2) the MS-OTK SHOULD be encrypted,
   by wrapping intersection of the MS-OTK with
   EID-prefix in the algorithm specified by Map-Reply EID-record with one of the OTK
   Encryption ID field as specified in Section 5.5.

   The Map-Server includes EID-prefixes
   contained in the EID-AD is not empty.  After identifying the longest match registered
   EID-prefix for Map-
   Reply record as valid, the destination EID, and an HMAC of this EID-prefix.
   The HMAC is keyed with ITR sets the ITR-OTK contained EID-prefix in the received ECM
   Authentication Data, Map-Reply
   record to the value of the intersection set computed before, and adds
   the HMAC algorithm is chosen according Map-Reply EID-record to
   the Requested HMAC ID field.  If its EID-to-RLOC cache, as described in
   [I-D.ietf-lisp-rfc6833bis].  An example of Map-Reply record
   validation is provided in Section 5.9.1.

   The Map-Server does not support this
   algorithm, ITR SHOULD send SMR triggered Map-Requests over the Map-Server uses mapping
   system in order to receive a different algorithm and specifies secure Map-Reply.  If an ITR accepts
   piggybacked Map-Replies, it SHOULD also send a Map-Request over the
   mapping system in order to verify the EID HMAC ID field. piggybacked Map-Reply with a
   secure Map-Reply.

5.9.1.  Map-Reply Record Validation

   The scope payload of a Map-Reply may contain multiple EID-records.  The
   whole Map-Reply is signed by the HMAC operation covers the
   entire EID-AD, from ETR, with the EID-AD Length field PKT HMAC, to the EID HMAC field,
   which must be set provide
   integrity protection and origin authentication to 0 before the computation.

   The Map-Server then forwards the updated ECM encapsulated Map-
   Request, that contains the OTK-AD, the EID-AD, and EID-prefix
   records claimed by the received Map-
   Request to an authoritative ETR as specified in
   [I-D.ietf-lisp-rfc6833bis].

5.7.1.  Map-Server Processing ETR.  The Authentication Data field of a Map-
   Reply may contain multiple EID-records in Proxy mode

   If the Map-Server EID-AD.  The EID-AD is in proxy mode, it generates a Map-Reply, as
   specified in [I-D.ietf-lisp-rfc6833bis],
   signed by the Map-Server, with the S-bit set EID HMAC, to provide integrity
   protection and origin authentication to 1.
   The Map-Reply includes the Authentication Data that contains the EID-
   AD, computed as specified in Section 5.7, as well as EID-prefix records
   inserted by the PKT-AD
   computed as specified in Section 5.8.

5.8.  ETR Processing Map-Server.

   Upon receiving an ECM encapsulated Map-Request a Map-Reply with the S-bit set, the ETR decapsulates ITR first checks
   the ECM message.  The OTK field, if encrypted,
   is decrypted as specified in Section 5.5 to obtain validity of both the unencrypted
   MS-OTK.

   The ETR then generates EID HMAC and of the PKT-AD HMAC.  If either
   one of the HMACs is not valid, a log action MUST be taken and the
   Map-Reply as specified MUST NOT be processed any further.  If both HMACs are
   valid, the ITR proceeds with validating each individual EID-record
   claimed by the ETR by computing the intersection of each one of the
   EID-prefix contained in
   [I-D.ietf-lisp-rfc6833bis] and includes the Authentication Data that
   contains payload of the EID-AD, as received Map-Reply with each one of
   the EID-prefixes contained in the encapsulated Map-Request, as
   well as EID-AD.  An EID-record is valid
   only if at least one of the PKT-AD.

   The EID-AD intersections is copied from not the Authentication Data of empty set.

   For instance, the received
   encapsulated Map-Request. Map-Reply payload contains 3 mapping record EID-
   prefixes:

      2001:db8:102::/48

      2001:db8:103::/48

      2001:db8:200::/40

   The PKT-AD EID-AD contains two EID-prefixes:

      2001:db8:103::/48

      2001:db8:203::/48

   The EID-record with EID-prefix 2001:db8:102::/48 is not eligible to
   be used by the HMAC ITR since it is not included in any of the whole Map-Reply packet, keyed EID-ADs
   signed by the Map-Server.  A log action MUST be taken.

   The EID-record with EID-prefix 2001:db8:103::/48 is eligible to be
   used by the MS-OTK and computed using ITR because it matches the HMAC algorithm specified second EID-prefix contained in
   the Requested HMAC ID field of the received encapsulated Map-Request.
   If the ETR does EID-AD.

   The EID-record with EID-prefix 2001:db8:200::/40 is not support eligible to
   be used by the Requested HMAC ID, ITR since it uses a
   different algorithm and updates the PKT HMAC ID field accordingly.
   The scope is not included in any of the HMAC operation covers the entire PKT-AD, from the
   Map-Reply Type field to EID-ADs
   signed by the PKT HMAC field, which must Map-Server.  A log action MUST be set to 0
   before the computation.

   Finally taken.  In this last
   example the ETR sends the Map-Reply is trying to over claim the requesting ITR as
   specified in [I-D.ietf-lisp-rfc6833bis]. EID-prefix
   2001:db8:200::/40, but the Map-Server authorized only
   2001:db8:203::/48, hence the EID-record is discarded.

6.  Security Considerations

6.1.  Mapping System Security

   The LISP-SEC threat model described in Section 3, assumes that the
   LISP Mapping System is working properly and eventually delivers Map-
   Request messages to a Map-Server that is authoritative for the
   requested EID.

   It is assumed that the Mapping System ensures the confidentiality of
   the OTK, and the integrity of the Map-Reply data.  However, how the
   LISP Mapping System is secured is out of the scope of this document.

   Similarly, Map-Register security, including the right for a LISP
   entity to register an EID-prefix or to claim presence at an RLOC, is
   out of the scope of LISP-SEC.

6.2.  Random Number Generation

   The ITR-OTK MUST be generated by a properly seeded pseudo-random (or
   strong random) source.  See [RFC4086] for advice on generating
   security-sensitive random data

6.3.  Map-Server and ETR Colocation

   If the Map-Server and the ETR are colocated, LISP-SEC does not
   provide protection from overclaiming attacks mounted by the ETR.
   However, in this particular case, since the ETR is within the trust
   boundaries of the Map-Server, ETR's overclaiming attacks are not
   included in the threat model.

6.4.  Deploying LISP-SEC

   This memo is written according to [RFC2119].  Specifically, the use
   of the key word SHOULD "or the adjective 'RECOMMENDED', mean that
   there may exist valid reasons in particular circumstances to ignore a
   particular item, but the full implications must be understood and
   carefully weighed before choosing a different course".

   Those deploying LISP-SEC according to this memo, should carefully
   weight how the LISP-SEC threat model applies to their particular use
   case or deployment.  If they decide to ignore a particular
   recommendation, they should make sure the risk associated with the
   corresponding threats is well understood.

   As an example, in certain closed and controlled deployments, it is
   possible that the threat associated with a MiTM between the xTR and
   the Mapping System is very low, and after carfeul consideration it
   may be decided to allow a NULL key wrapping algorithm while carrying
   the OTKs between the xTR and the Mapping System.

   As an example at the other end of the spectrum, in certain other
   deployments, attackers may be very sophisticated, and force the
   deployers to enforce very strict policies in term of HMAC algorithms
   accepted by an ITR.

   Similar considerations apply to the entire LISP-SEC threat model, and
   should guide the deployers and implementors whenever they encounter
   the key word SHOULD across this memo.

6.5.  Shared Keys Provisioning

   Provisioning of the keys shared between the ITR and the Map-Resolver
   as well as between the ETR and the Map-Server should be performed via
   an orchestration infrastructure and it is out of the scope of this
   draft.  It is recommended that both shared keys are refreshed at
   periodical intervals to address key aging or attackers gaining
   unauthorized access to the shared keys.  Shared keys should be
   unpredictable random values.

6.6.  Replay Attacks

   An attacker can capture a valid Map-Request and/or Map-Reply and
   replay it, however once the ITR receives the original Map-Reply the
   <nonce,ITR-OTK> pair stored at the ITR will be discarded.  If a
   replayed Map-Reply arrives at the ITR, there is no <nonce,ITR-OTK>
   that matches the incoming Map-Reply and will be discarded.

   In case of replayed Map-Request, the Map-Server, Map-Resolver and ETR
   will have to do a LISP-SEC computation.  This is equivalent to a
   valid LISP-SEC computation and an attacker does not obtain any
   benefit.

6.7.  Message Privacy

   DTLS [RFC6347] SHOULD be used to provide communication privacy and to
   prevent eavesdropping, tampering, or message forgery to the messages
   exchanged between the ITR, Map-Resolver, Map-Server, and ETR.

6.8.  Denial of Service and Distributed Denial of Service Attacks

   LISP-SEC mitigates the risks of Denial of Service and Distributed
   Denial of Service attacks by protecting the integrity and
   authenticating the origin of the Map-Request/Map-Reply messages, and
   by preventing malicious ETRs from overclaiming EID prefixes that
   could re-direct traffic directed to a potentially large number of
   hosts.

7.  IANA Considerations

7.1.  ECM AD Type Registry

   IANA is requested to create the "ECM Authentication Data Type"
   registry with values 0-255, for use in the ECM LISP-SEC Extensions
   Section 5.1.  The registry MUST be initially populated with the
   following values:

             Name                     Value        Defined In
             -------------------------------------------------
             Reserved
             Unassigned               0             This memo
             LISP-SEC-ECM-EXT         1             This memo

                              HMAC Functions

   Values 2-255 are unassigned.  They are to be assigned according to
   the "Specification Required" policy defined in [RFC5226].

7.2.  Map-Reply AD Type Registry

   IANA is requested to create the "Map-Reply Authentication Data Type"
   registry with values 0-255, for use in the Map-Reply LISP-SEC
   Extensions Section 5.2.  The registry MUST be initially populated
   with the following values:

             Name                     Value        Defined In
             -------------------------------------------------
             Reserved
             Unassigned               0             This memo
             LISP-SEC-MR-EXT          1             This memo

                              HMAC Functions

   Values 2-255 are unassigned.  They are to be assigned according to
   the "Specification Required" policy defined in [RFC5226].

7.3.  HMAC Functions

   IANA is requested to create the "LISP-SEC Authentication Data HMAC
   ID" registry with values 0-65535 for use as Requested HMAC ID, EID
   HMAC ID, and PKT HMAC ID in the LISP-SEC Authentication Data:

             Name                     Number        Defined In
             -------------------------------------------------
             NONE                     0             This memo
             AUTH-HMAC-SHA-1-96       1             [RFC2104]
             AUTH-HMAC-SHA-256-128    2             [RFC6234]

                              HMAC Functions

   Values 3-65535 are unassigned.  They are to be assigned according to
   the "Specification Required" policy defined in [RFC5226].

   AUTH-HMAC-SHA-1-96 MUST be supported, AUTH-HMAC-SHA-256-128 SHOULD be
   supported.

7.4.  Key Wrap Functions

   IANA is requested to create the "LISP-SEC Authentication Data Key
   Wrap ID" registry with values 0-65535 for use as OTK key wrap
   algorithms ID in the LISP-SEC Authentication Data:

     Name                        Number        Defined In
             -------------------------------------------------
             Reserved     KEY WRAP       KDF
     -----------------------------------------------------------------
     Unassigned                     0             This memo       None           None
     NULL-KEY-WRAP-128              1       This memo
             AES-KEY-WRAP-128      None
     AES-KEY-WRAP-128+HKDF-SHA256   2       [RFC3394]      [RFC4868]

                            Key Wrap Functions

   Values 3-65535 are unassigned.  They are to be assigned according to
   the "Specification Required" policy defined in [RFC5226].

   NULL-KEY-WRAP-128, and AES-KEY-WRAP-128 AES-KEY-WRAP-128+HKDF-SHA256 MUST be
   supported.

   NULL-KEY-WRAP-128 is used to carry an unencrypted 128-bit OTK, with a
   64-bit preamble set to 0x0000000000000000 (64 bits).

7.5.  Key Derivation Functions

   IANA is requested to create the "LISP-SEC Authentication Data Key
   Derivation Function ID" registry with values 0-65535 for use as KDF
   ID in the LISP-SEC Authentication Data:

             Name                     Number        Defined In
             -------------------------------------------------
             NONE                     0             This memo
             HKDF-SHA1-128            1             [RFC5869]

                         Key Derivation Functions

   Values 2-65535 are unassigned.  They are to be assigned according to
   the "Specification Required" policy defined in [RFC5226].

   HKDF-SHA1-128 MUST be supported

8.  Acknowledgements

   The authors would like to acknowledge Pere Monclus, Dave Meyer, Dino
   Farinacci, Brian Weis, David McGrew, Darrel Lewis and Landon Curt
   Noll for their valuable suggestions provided during the preparation
   of this document.

9.  References

9.1.  Normative References

   [I-D.ietf-lisp-rfc6830bis]
              Farinacci, D., Fuller, V., Meyer, D., Lewis, D., and A.
              Cabellos-Aparicio, "The Locator/ID Separation Protocol
              (LISP)", draft-ietf-lisp-rfc6830bis-26 (work in progress),
              November 2018.

   [I-D.ietf-lisp-rfc6833bis]
              Fuller, V., Farinacci, D., and A. Cabellos-Aparicio,
              "Locator/ID Separation Protocol (LISP) Control-Plane",
              draft-ietf-lisp-rfc6833bis-22
              draft-ietf-lisp-rfc6833bis-24 (work in progress), November
              2018. February
              2019.

   [RFC2104]  Krawczyk, H., Bellare, M., and R. Canetti, "HMAC: Keyed-
              Hashing for Message Authentication", RFC 2104,
              DOI 10.17487/RFC2104, February 1997, <https://www.rfc-
              editor.org/info/rfc2104>.

   [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>.

   [RFC3394]  Schaad, J. and R. Housley, "Advanced Encryption Standard
              (AES) Key Wrap Algorithm", RFC 3394, DOI 10.17487/RFC3394,
              September 2002, <https://www.rfc-editor.org/info/rfc3394>.

   [RFC4086]  Eastlake 3rd, D., Schiller, J., and S. Crocker,
              "Randomness Requirements for Security", BCP 106, RFC 4086,
              DOI 10.17487/RFC4086, June 2005, <https://www.rfc-
              editor.org/info/rfc4086>.

   [RFC4868]  Kelly, S. and S. Frankel, "Using HMAC-SHA-256, HMAC-SHA-
              384, and HMAC-SHA-512 with IPsec", RFC 4868,
              DOI 10.17487/RFC4868, May 2007, <https://www.rfc-
              editor.org/info/rfc4868>.

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

   [RFC5869]  Krawczyk, H. and P. Eronen, "HMAC-based Extract-and-Expand
              Key Derivation Function (HKDF)", RFC 5869,
              DOI 10.17487/RFC5869, May 2010, <https://www.rfc-
              editor.org/info/rfc5869>.

   [RFC6234]  Eastlake 3rd, D. and T. Hansen, "US Secure Hash Algorithms
              (SHA and SHA-based HMAC and HKDF)", RFC 6234,
              DOI 10.17487/RFC6234, May 2011, <https://www.rfc-
              editor.org/info/rfc6234>.

   [RFC6347]  Rescorla, E. and N. Modadugu, "Datagram Transport Layer
              Security Version 1.2", RFC 6347, DOI 10.17487/RFC6347,
              January 2012, <https://www.rfc-editor.org/info/rfc6347>.

   [RFC6836]  Fuller, V., Farinacci, D., Meyer, D., and D. Lewis,
              "Locator/ID Separation Protocol Alternative Logical
              Topology (LISP+ALT)", RFC 6836, DOI 10.17487/RFC6836,
              January 2013, <https://www.rfc-editor.org/info/rfc6836>.

   [RFC7835]  Saucez, D., Iannone, L., and O. Bonaventure, "Locator/ID
              Separation Protocol (LISP) Threat Analysis", RFC 7835,
              DOI 10.17487/RFC7835, April 2016, <https://www.rfc-
              editor.org/info/rfc7835>.

   [RFC8060]  Farinacci, D., Meyer, D., and J. Snijders, "LISP Canonical
              Address Format (LCAF)", RFC 8060, DOI 10.17487/RFC8060,
              February 2017, <https://www.rfc-editor.org/info/rfc8060>.

   [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>.

9.2.  Informative References

   [I-D.ietf-lisp-rfc6830bis]
              Farinacci, D., Fuller, V., Meyer, D., Lewis, D., and A.
              Cabellos-Aparicio, "The Locator/ID Separation Protocol
              (LISP)", draft-ietf-lisp-rfc6830bis-26 (work in progress),
              November 2018.

Authors' Addresses

   Fabio Maino
   Cisco Systems
   170 Tasman Drive
   San Jose, California  95134
   USA

   Email: fmaino@cisco.com

   Vina Ermagan
   Cisco Systems
   170 Tasman Drive
   San Jose,
   Google
   California  95134
   USA

   Email: vermagan@cisco.com ermagan@gmail.com

   Albert Cabellos
   Universitat Politecnica de Catalunya
   c/ Jordi Girona s/n
   Barcelona  08034
   Spain

   Email: acabello@ac.upc.edu

   Damien Saucez
   INRIA
   2004 route des Lucioles - BP 93
   Sophia Antipolis
   France

   Email: damien.saucez@inria.fr