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Versions: (draft-maino-lisp-sec) 00 01 02 03 04 05 06

Network Working Group                                           F. Maino
Internet-Draft                                                V. Ermagan
Intended status: Experimental                              Cisco Systems
Expires: April 24, 2014                                      A. Cabellos
                                       Technical University of Catalonia
                                                               D. Saucez
                                                                   INRIA
                                                          O. Bonaventure
                                        Universite Catholique de Louvain
                                                        October 21, 2013


                        LISP-Security (LISP-SEC)
                         draft-ietf-lisp-sec-05

Abstract

   This memo specifies LISP-SEC, a set of security mechanisms that
   provide 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].

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 24, 2014.

Copyright Notice




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   Copyright (c) 2013 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.

Table of Contents

   1.  Introduction  . . . . . . . . . . . . . . . . . . . . . . . .   3
   2.  Definition of Terms . . . . . . . . . . . . . . . . . . . . .   3
   3.  LISP-SEC Threat Model . . . . . . . . . . . . . . . . . . . .   4
   4.  Protocol Operations . . . . . . . . . . . . . . . . . . . . .   4
   5.  LISP-SEC Control Messages Details . . . . . . . . . . . . . .   7
     5.1.  Encapsulated Control Message LISP-SEC Extensions  . . . .   7
     5.2.  Map-Reply LISP-SEC Extensions . . . . . . . . . . . . . .   9
     5.3.  Map-Register LISP-SEC Extentions  . . . . . . . . . . . .  10
     5.4.  ITR Processing  . . . . . . . . . . . . . . . . . . . . .  11
       5.4.1.  Map-Reply Record Validation . . . . . . . . . . . . .  12
       5.4.2.  PITR Processing . . . . . . . . . . . . . . . . . . .  13
     5.5.  Encrypting and Decrypting an OTK  . . . . . . . . . . . .  13
     5.6.  Map-Resolver Processing . . . . . . . . . . . . . . . . .  14
     5.7.  Map-Server Processing . . . . . . . . . . . . . . . . . .  14
       5.7.1.  Map-Server Processing in Proxy mode . . . . . . . . .  15
     5.8.  ETR Processing  . . . . . . . . . . . . . . . . . . . . .  15
   6.  Security Considerations . . . . . . . . . . . . . . . . . . .  16
     6.1.  Mapping System Security . . . . . . . . . . . . . . . . .  16
     6.2.  Random Number Generation  . . . . . . . . . . . . . . . .  16
     6.3.  Map-Server and ETR Colocation . . . . . . . . . . . . . .  17
   7.  IANA Considerations . . . . . . . . . . . . . . . . . . . . .  17
     7.1.  HMAC functions  . . . . . . . . . . . . . . . . . . . . .  17
     7.2.  Key Wrap Functions  . . . . . . . . . . . . . . . . . . .  17
     7.3.  Key Derivation Functions  . . . . . . . . . . . . . . . .  18
   8.  Acknowledgements  . . . . . . . . . . . . . . . . . . . . . .  18
   9.  Normative References  . . . . . . . . . . . . . . . . . . . .  18
   Authors' Addresses  . . . . . . . . . . . . . . . . . . . . . . .  19









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1.  Introduction

   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).  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.  A detailed description of "overclaiming" attack is provided
   in [I-D.ietf-lisp-threats].

   This memo specifies LISP-SEC, a set of security mechanisms that
   provide 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 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.  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-OTK: The One-Time Key generated at the ITR.

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

      Encapsulated Control Message (ECM): A LISP control message that is
      prepended with an additional LISP header.  ECM is used by ITRs to
      send LISP control messages to a Map-Resolver, by Map-Resolvers to
      forward LISP control messages to a Map-Server, and by Map-
      Resolvers to forward LISP control messages to an ETR.

      Authentication Data (AD): Metadata that is included either in a
      LISP ECM header or in a Map-Reply message to support
      confidentiality, integrity protection, and verification of EID-
      prefix authorization.



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

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

         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
   [RFC6830].

3.  LISP-SEC Threat Model

   LISP-SEC addresses the control plane threats, described in
   [I-D.ietf-lisp-threats], that target EID-to-RLOC mappings, including
   manipulations of Map-Request and Map-Reply messages, and malicious
   ETR EID prefix overclaiming.  However LISP-SEC makes two main
   assumptions that are not part of [I-D.ietf-lisp-threats].  First, the
   LISP mapping system is expected to deliver a Map-Request message to
   their intended destination ETR as identified by the EID.  Second, no
   man-in-the-middle attack can be mounted within the LISP Mapping
   System.  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 [I-D.ietf-lisp-threats]
   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 over claiming 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 [RFC6830] is to
   prevent unauthorized insertion of mapping data by providing origin
   authentication and integrity protection for the Map-Registration, and
   by using the nonce to detect unsolicited Map-Reply sent by off-path
   attackers.





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   LISP-SEC builds on top of the security mechanisms defined in
   [RFC6830] 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 a 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 over claiming attacks.  The
   processing of security parameters during the Map-Request/Map-Reply
   exchange is as follows:

   o  The 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 an HMAC 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) 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 protocol operations at each entity involved in
   the Map-Request/Map-Reply exchange:

   o  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 confidentiality to the ITR-
      OTK over the path between the ITR and its Map-Resolver, the ITR-
      OTK SHOULD be encrypted using a preconfigured key shared between
      the ITR and the Map-Resolver, similar to the key shared between
      the ETR and the Map-Server in order to secure ETR registration
      [RFC6833].









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   o  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 LISP Mapping System
      delivers the ECM to the appropriate Map-Server, as identified by
      the EID destination address of the Map-Request.

   o  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  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 the path between the Map-Server and the ETR,
      the MS-OTK should be encrypted using the key shared between the
      ETR and the Map-Server in order to secure ETR registration
      [RFC6833].

   o  If the Map-Server is acting in proxy mode, as specified in
      [RFC6830], the ETR is not involved in the generation of the Map-
      Reply.  In this case the Map-Server generates the Map-Reply on
      behalf of the ETR as described below.

   o  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 that contains the EID-to-RLOC mapping
      information as specified in [RFC6830].

   o  The ETR computes an HMAC over this standard 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 complete Map-Reply message to
      the requesting ITR.

   o  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 used by the Map-
      Server, and verifies the integrity of the Map-Reply.  If the
      integrity checks fail, the Map-Reply MUST be discarded.  Also, if



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      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
   [RFC6830] 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.
   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
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |     AD Type   |V|  Reserved   |        Requested HMAC ID      |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+\
   |              OTK Length       |       OTK Encryption ID       | |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ |
   |                       One-Time-Key Preamble ...               | |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ OTK-AD
   |                   ... One-Time-Key Preamble                   | |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ |
   ~                      One-Time Key (128 bits)                  ~/
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ <---+
   |           EID-AD Length       |           KDF ID              |     |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+     |
   | Record Count  |    Reserved   |         EID HMAC ID           |     EID-AD
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+\    |
   |   Reserved    | EID mask-len  |           EID-AFI             | |   |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ Rec |
   ~                          EID-prefix ...                       ~ |   |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+/    |
   ~                            EID HMAC                           ~     |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ <---+

                     LISP-SEC ECM Authentication Data

      AD Type: 1 (LISP-SEC Authentication Data)



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

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

      Requested HMAC ID: The HMAC algorithm requested by the ITR.  See
      Section 5.4 for details.

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

      OTK Encryption ID: The identifier of the key wrapping algorithm
      used to encrypt the One-Time-Key. When a 128-bit OTK is sent
      unencrypted by the Map-Resolver, the OTK Encryption ID is set to
      NULL_KEY_WRAP_128.  See Section 5.5 for more details.

      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 for details.

      One-Time-Key: the OTK encrypted (or not) as specified by OTK
      Encryption 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 SHOULD 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.

      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: 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.




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      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 the entire EID-AD.

5.2.  Map-Reply LISP-SEC Extensions

   LISP-SEC uses the Map-Reply defined in [RFC6830], with Type set to 2,
   and 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.  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
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |    AD Type    |                 Reserved                      |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ <---+
   |           EID-AD Length       |           KDF ID              |     |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+     |
   | Record Count  |    Reserved   |         EID HMAC ID           |     EID-AD
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+\    |
   |   Reserved    | EID mask-len  |           EID-AFI             | |   |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ Rec |
   ~                          EID-prefix ...                       ~ |   |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+/    |
   ~                            EID HMAC                           ~     |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ <---+
   |         PKT-AD Length         |         PKT HMAC ID           |\
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ |
   ~                            PKT HMAC                           ~ PKT-AD
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+/

                  LISP-SEC Map-Reply Authentication Data

      AD Type: 1 (LISP-SEC Authentication Data)

      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.




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      KDF ID: Identifier of the Key Derivation Function used to derive
      MS-OTK.  See Section 5.7 for more details.

      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: 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.

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

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

      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 Location Data.

      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

   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 that
   the registering ETR is LISP-SEC enabled.  An ETR that supports LISP-
   SEC MUST set the S bit in its Map-Register messages.









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5.4.  ITR Processing

   Upon creating a Map-Request, the ITR generates a random ITR-OTK that
   is stored locally, together with the nonce generated as specified in
   [RFC6830].

   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 with the
   algorithm specified by the OTK Encryption ID field.  See Section 5.5
   for further details on OTK encryption.

   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.

   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 to an encapsulated Map-Request that has the S-bit set, an
   ITR MUST receive a Map-Reply with the S-bit set, that includes an
   EID-AD and a PKT-AD.  If the Map-Reply does not include both ADs, the
   ITR MUST discard it.  In response to an encapsulated Map-Request with
   S-bit set to 0, the ITR expects a Map-Reply with S-bit set to 0, and
   the ITR SHOULD discard the Map-Reply if the S-bit is set.

   Upon receiving a Map-Reply, the ITR must verify the integrity of both
   the EID-AD and the PKT-AD, and MUST discard the Map-Reply if one of
   the integrity checks fails.

   The integrity of the EID-AD is verified using the locally stored ITR-
   OTK to re-compute the HMAC of the EID-AD using the algorithm
   specified in the EID HMAC ID field.  If the EID HMAC ID field does
   not match the Requested HMAC ID the ITR SHOULD discard the Map-Reply
   and send, at the first opportunity it needs to, a new Map-Request
   with a different Requested HMAC ID field, according to ITR's local
   policy.  The 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
   KDF ID field.  This is because the PKT-AD is generated by the ETR
   using the MS-OTK.  If the KDF ID in the Map-Reply does not match the



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   KDF ID requested in the Map-Request, the ITR SHOULD discard the Map-
   Reply and send, at 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 is then used to re-compute the HMAC of the PKT-AD
   using the Algorithm specified in the PKT HMAC ID field.  If the PKT
   HMAC ID field does not match the Requested HMAC ID the ITR SHOULD
   discard the Map-Reply and send, at the first opportunity it needs to,
   a new Map-Request with a different Requested HMAC ID according to
   ITR's local policy.

   Each individual Map-Reply EID-record is considered valid only if: (1)
   both EID-AD and PKT-AD are valid, and (2) the intersection of the
   EID-prefix in the Map-Reply EID-record with one of the EID-prefixes
   contained in the EID-AD is not empty.  After identifying the Map-
   Reply record as valid, the ITR sets the EID-prefix in the Map-Reply
   record to the value of the intersection set computed before, and adds
   the Map-Reply EID-record to its EID-to-RLOC cache, as described in
   [RFC6830].  An example of Map-Reply record validation is provided in
   Section 5.4.1.

   The ITR SHOULD send SMR triggered Map Requests over the mapping
   system in order 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 to securely verify the piggybacked Map-Reply.

5.4.1.  Map-Reply Record Validation

   The payload of a Map-Reply may contain multiple EID-records.  The
   whole Map-Reply is signed by the ETR, with the PKT HMAC, to provide
   integrity protection and origin authentication to the EID-prefix
   records claimed by the ETR.  The Authentication Data field of a Map-
   Reply may contain multiple EID-records in the EID-AD.  The EID-AD is
   signed by the Map-Server, with the EID HMAC, to provide integrity
   protection and origin authentication to the EID-prefix records
   inserted by the Map-Server.

   Upon receiving a Map-Reply with the S-bit set, the ITR first checks
   the validity of both the EID HMAC and of the PKT-AD HMAC.  If either
   one of the HMACs is not valid, a log message is issued and the Map-
   Reply is not 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 the payload of the Map-Reply with each one of the EID-
   prefixes contained in the EID-AD.  An EID-record is valid only if at
   least one of the intersections is not the empty set.

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



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      1.1.1.0/24

      1.1.2.0/24

      1.2.0.0/16

   The EID-AD contains two EID-prefixes:

      1.1.2.0/24

      1.2.3.0/24

   The EID-record with EID-prefix 1.1.1.0/24 is not processed since it
   is not included in any of the EID-ADs signed by the Map-Server.  A
   log message is issued.

   The EID-record with EID-prefix 1.1.2.0/24 is stored in the map-cache
   because it matches the second EID-prefix contained in the EID-AD.

   The EID-record with EID-prefix 1.2.0.0/16 is not processed since it
   is not included in any of the EID-ADs signed by the Map-Server.  A
   log message is issued.  In this last example the ETR is trying to
   over claim the EID-prefix 1.2.0.0/16, but the Map-Server authorized
   only 1.2.3.0/24, hence the EID-record is discarded.

5.4.2.  PITR Processing

   The processing performed by a PITR is equivalent to the processing of
   an ITR.  However, if the PITR is directly connected to the ALT, the
   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 OTK

   MS-OTK confidentiality is required in the path between the Map-Server
   and the ETR, the MS-OTK SHOULD be encrypted using the preconfigured
   key shared between the Map-Server and the ETR for the purpose of
   securing ETR registration [RFC6833].  Similarly, if ITR-OTK
   confidentiality is required in the path between the ITR and the Map-
   Resolver, the ITR-OTK SHOULD be encrypted with a key shared between
   the ITR and the Map-Resolver.

   The OTK is encrypted using the algorithm specified in the OTK
   Encryption ID field.  When the AES Key Wrap algorithm is used to
   encrypt a 128-bit OTK, according to [RFC3339], 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



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   significant 64-bit are copied in the One-Time Key Preamble field,
   while the 128 less significant bits are copied in the One-Time Key
   field of the LISP-SEC Authentication Data.

   When decrypting an encrypted OTK the receiver MUST verify that the
   Initialization Value resulting from the AES Key Wrap decryption
   operation is equal to 0xA6A6A6A6A6A6A6A6.  If this verification fails
   the receiver MUST discard the entire message.

   When a 128-bit OTK is sent unencrypted the OTK Encryption ID is set
   to NULL_KEY_WRAP_128, and the OTK Preamble is set to
   0x0000000000000000 (64 bits).

5.6.  Map-Resolver Processing

   Upon receiving an encapsulated Map-Request with the S-bit set, the
   Map-Resolver decapsulates the ECM message.  The ITR-OTK, if
   encrypted, is decrypted as specified in Section 5.5.

   The Map-Resolver, as specified in [RFC6833], originates a new ECM
   header with the S-bit set, that contains the unencrypted ITR-OTK, as
   specified in Section 5.5, and the other data derived from the ECM
   Authentication Data of the received encapsulated Map-Request.

   The Map-Resolver then forwards the received Map-Request, encapsulated
   in the new ECM header that includes the newly computed Authentication
   Data fields.

5.7.  Map-Server Processing

   Upon receiving an ECM encapsulated Map-Request with the S-bit set,
   the Map-Server process the Map-Request according to the value of the
   S-bit contained in the Map-Register sent by the ETR during
   registration.

   If the S-bit contained in the Map-Register was clear the Map-Server
   decapsulates the ECM and generates a new ECM encapsulated Map-Request
   that does not contain an ECM Authentication Data, as specified in
   [RFC6830].  The Map-Server does not perform any further LISP-SEC
   processing.

   If the S-bit contained in the Map-Register was set 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 authorization information, that are ultimately
   sent to the requesting ITR.





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   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 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.

   The Map-Server and the ETR MUST be configured with a shared key for
   mapping registration according to [RFC6833].  If MS-OTK
   confidentiality is required, then the MS-OTK SHOULD be encrypted, by
   wrapping the MS-OTK with the algorithm specified by the OTK
   Encryption ID field as specified in Section 5.5.

   The Map-Server includes in the EID-AD the longest match registered
   EID-prefix for the destination EID, and an HMAC of this EID-prefix.
   The HMAC is keyed with the ITR-OTK contained in the received ECM
   Authentication Data, and the HMAC algorithm is chosen according to
   the Requested HMAC ID field.  If The Map-Server does not support this
   algorithm, the Map-Server uses a different algorithm and specifies it
   in the EID HMAC ID field.  The scope of the HMAC operation covers the
   entire EID-AD, from the EID-AD Length field to the EID HMAC field,
   which must be set 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 the received Map-
   Request to an authoritative ETR as specified in [RFC6830].

5.7.1.  Map-Server Processing in Proxy mode

   If the Map-Server is in proxy mode, it generates a Map-Reply, as
   specified in [RFC6830], with the S-bit set to 1.  The Map-Reply
   includes the Authentication Data that contains the EID-AD, computed
   as specified in Section 5.7, as well as the PKT-AD computed as
   specified in Section 5.8.

5.8.  ETR Processing

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

   The ETR then generates a Map-Reply as specified in [RFC6830] and
   includes the Authentication Data that contains the EID-AD, as
   received in the encapsulated Map-Request, as well as the PKT-AD.

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



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   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 Requested HMAC ID field of the received encapsulated Map-Request.
   If the ETR does not support the Requested HMAC ID, it uses a
   different algorithm and updates the PKT HMAC ID field accordingly.
   The scope of the HMAC operation covers the entire PKT-AD, from the
   Map-Reply Type field to the PKT HMAC field, which must be set to 0
   before the computation.

   Finally the ETR sends the Map-Reply to the requesting ITR as
   specified in [RFC6830].

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.

   Security is not yet embedded in LISP+ALT but BGP route filtering
   SHOULD be deployed in the ALT infrastructure to enforce proper
   routing in the mapping system.  The SIDR working group is currently
   addressing prefix and route advertisement authorization and
   authentication for BGP.  While following SIDR recommendations in the
   global Internet will take time, applying these recommendations to the
   ALT, which relies on BGP, should be less complex, as ALT is currently
   small and with a limited number of operators.  Ultimately, deploying
   the SIDR recommendations in ALT further ensures that the fore
   mentioned assumption is true.

   It is also assumed that no man-in-the-middle attack can be carried
   out against the ALT router to ALT router tunnels, and that the
   information included into the Map-Requests, in particular the OTK,
   cannot be read by third-party entities.  It should be noted that the
   integrity of the Map-Request in the ALT is protected by BGP
   authentication, and that in order to provide OTK confidentiality in
   the ALT mapping system the ALT router to ALT router tunnels MAY be
   deployed using IPsec (ESP).

   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





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   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.

7.  IANA Considerations

7.1.  HMAC functions

   The following HMAC ID values are defined by this memo 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
             AUTH-HMAC-SHA-1-96       1             [RFC2104]
             AUTH-HMAC-SHA-256-128    2             [RFC4634]

             values 2-65535 are reserved to IANA.

                              HMAC Functions

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

7.2.  Key Wrap Functions

   The following OTK Encryption ID values are defined by this memo for
   use as OTK key wrap algorithms ID in the LISP-SEC Authentication
   Data:

             Name                     Number        Defined In
             -------------------------------------------------
             NULL-KEY-WRAP-128        1
             AES-KEY-WRAP-128         2             [RFC3394]

             values 0 and 3-65535 are reserved to IANA.

                            Key Wrap Functions




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   NULL-KEY-WRAP-128, and AES-KEY-WRAP-128 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).

7.3.  Key Derivation Functions

   The following KDF ID values are defined by this memo for use as KDF
   ID in the LISP-SEC Authentication Data:

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

             values 2-65535 are reserved to IANA.

                         Key Derivation Functions

   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.  Normative References

   [I-D.ietf-lisp-threats]
              Saucez, D., Iannone, L., and O. Bonaventure, "LISP Threats
              Analysis", draft-ietf-lisp-threats-08 (work in progress),
              October 2013.

   [RFC2104]  Krawczyk, H., Bellare, M., and R. Canetti, "HMAC: Keyed-
              Hashing for Message Authentication", RFC 2104, February
              1997.

   [RFC2119]  Bradner, S., "Key words for use in RFCs to Indicate
              Requirement Levels", BCP 14, RFC 2119, March 1997.

   [RFC3394]  Schaad, J. and R. Housley, "Advanced Encryption Standard
              (AES) Key Wrap Algorithm", RFC 3394, September 2002.

   [RFC4086]  Eastlake, D., Schiller, J., and S. Crocker, "Randomness
              Requirements for Security", BCP 106, RFC 4086, June 2005.




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   [RFC5226]  Narten, T. and H. Alvestrand, "Guidelines for Writing an
              IANA Considerations Section in RFCs", BCP 26, RFC 5226,
              May 2008.

   [RFC5869]  Krawczyk, H. and P. Eronen, "HMAC-based Extract-and-Expand
              Key Derivation Function (HKDF)", RFC 5869, May 2010.

   [RFC6830]  Farinacci, D., Fuller, V., Meyer, D., and D. Lewis, "The
              Locator/ID Separation Protocol (LISP)", RFC 6830, January
              2013.

   [RFC6833]  Fuller, V. and D. Farinacci, "Locator/ID Separation
              Protocol (LISP) Map-Server Interface", RFC 6833, January
              2013.

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, California  95134
   USA

   Email: vermagan@cisco.com


   Albert Cabellos
   Technical University of Catalonia
   c/ Jordi Girona s/n
   Barcelona  08034
   Spain

   Email: acabello@ac.upc.edu









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

   Email: damien.saucez@inria.fr


   Olivier Bonaventure
   Universite Catholique de Louvain
   Place St. Barbe 2
   Louvain-la-Neuve
   Belgium

   Email: olivier.bonaventure@uclouvain.be



































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