Network Working Group                                           F. MainoInternet-Draft                                                V. ErmaganIntended status: Experimental                              Cisco SystemsExpires: May 20, 2017                                        A. Cabellos                                       Technical University of Catalonia                                                               D. Saucez                                                                   INRIA                                                       November 16, 2016                        LISP-Security (LISP-SEC)                         draft-ietf-lisp-sec-12Abstract   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].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 May 20, 2017.Maino, et al.             Expires May 20, 2017                  [Page 1]Internet-Draft                  LISP-SEC                   November 2016Copyright Notice   Copyright (c) 2016 IETF Trust and the persons identified as the   document authors.  All rights reserved.   This document is subject to BCP 78 and the IETF Trust's Legal   Provisions Relating to IETF Documents   (http://trustee.ietf.org/license-info) in effect on the date of   publication of this document.  Please review these documents   carefully, as they describe your rights and restrictions with respect   to this document.  Code Components extracted from this document must   include Simplified BSD License text as described in Section 4.e of   the Trust Legal Provisions and are provided without warranty as   described in the Simplified BSD License.Table of Contents   1.  Introduction  . . . . . . . . . . . . . . . . . . . . . . . .   3   2.  Definition of Terms . . . . . . . . . . . . . . . . . . . . .   3   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     5.3.  Map-Register LISP-SEC Extentions  . . . . . . . . . . . .  11     5.4.  ITR Processing  . . . . . . . . . . . . . . . . . . . . .  11       5.4.1.  Map-Reply Record Validation . . . . . . . . . . . . .  13       5.4.2.  PITR Processing . . . . . . . . . . . . . . . . . . .  14     5.5.  Encrypting and Decrypting an OTK  . . . . . . . . . . . .  14     5.6.  Map-Resolver Processing . . . . . . . . . . . . . . . . .  15     5.7.  Map-Server Processing . . . . . . . . . . . . . . . . . .  15       5.7.1.  Map-Server Processing in Proxy mode . . . . . . . . .  16     5.8.  ETR Processing  . . . . . . . . . . . . . . . . . . . . .  16   6.  Security Considerations . . . . . . . . . . . . . . . . . . .  17     6.1.  Mapping System Security . . . . . . . . . . . . . . . . .  17     6.2.  Random Number Generation  . . . . . . . . . . . . . . . .  17     6.3.  Map-Server and ETR Colocation . . . . . . . . . . . . . .  17     6.4.  Deploying LISP-SEC  . . . . . . . . . . . . . . . . . . .  17   7.  IANA Considerations . . . . . . . . . . . . . . . . . . . . .  18     7.1.  ECM AD Type Registry  . . . . . . . . . . . . . . . . . .  18     7.2.  Map-Reply AD Type Registry  . . . . . . . . . . . . . . .  18     7.3.  HMAC Functions  . . . . . . . . . . . . . . . . . . . . .  19     7.4.  Key Wrap Functions  . . . . . . . . . . . . . . . . . . .  19     7.5.  Key Derivation Functions  . . . . . . . . . . . . . . . .  20   8.  Acknowledgements  . . . . . . . . . . . . . . . . . . . . . .  20   9.  Normative References  . . . . . . . . . . . . . . . . . . . .  20   Authors' Addresses  . . . . . . . . . . . . . . . . . . . . . . .  22Maino, et al.             Expires May 20, 2017                  [Page 2]Internet-Draft                  LISP-SEC                   November 20161.  Introduction   The Locator/ID Separation Protocol [RFC6830] 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 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 One-Time Key (ITR-OTK): The One-Time Key generated at the 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 [RFC6830], or in a Map-Reply message to support      confidentiality, integrity protection, and verification of EID-      prefix authorization.Maino, et al.             Expires May 20, 2017                  [Page 3]Internet-Draft                  LISP-SEC                   November 2016      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   [RFC6830].3.  LISP-SEC Threat Model   LISP-SEC addresses the control plane threats, described in [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.Maino, et al.             Expires May 20, 2017                  [Page 4]Internet-Draft                  LISP-SEC                   November 20164.  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.   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 overclaiming 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 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) 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 betweenMaino, et al.             Expires May 20, 2017                  [Page 5]Internet-Draft                  LISP-SEC                   November 2016      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].   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 authorizationMaino, et al.             Expires May 20, 2017                  [Page 6]Internet-Draft                  LISP-SEC                   November 2016      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      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.Maino, et al.             Expires May 20, 2017                  [Page 7]Internet-Draft                  LISP-SEC                   November 2016  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   |        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      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: 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 isMaino, et al.             Expires May 20, 2017                  [Page 8]Internet-Draft                  LISP-SEC                   November 2016      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 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.      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.      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.Maino, et al.             Expires May 20, 2017                  [Page 9]Internet-Draft                  LISP-SEC                   November 2016  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                      | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ <---+ |           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      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.      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.Maino, et al.             Expires May 20, 2017                 [Page 10]Internet-Draft                  LISP-SEC                   November 2016      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.      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 in the   Map-Register message defined in Section 6.1.6 of [RFC6830].  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 that the registering ETR is LISP-SEC enabled.  An ETR that   supports LISP-SEC MUST set the S bit in its Map-Register messages.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.  A KDF Value of NONE   (0), MAY be used to specify that the ITR has no preferred KDF ID.Maino, et al.             Expires May 20, 2017                 [Page 11]Internet-Draft                  LISP-SEC                   November 2016   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 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 of the 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   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   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 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, 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-ReplyMaino, et al.             Expires May 20, 2017                 [Page 12]Internet-Draft                  LISP-SEC                   November 2016   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 verify the piggybacked Map-Reply with a   secure 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 action MUST be taken and 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 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:      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::/48Maino, et al.             Expires May 20, 2017                 [Page 13]Internet-Draft                  LISP-SEC                   November 2016   The EID-record with EID-prefix 2001:db8:0102::/48 is not eligible to   be used by the ITR since it is not included in any of the EID-ADs   signed by the Map-Server.  A log action MUST be taken.   The EID-record with EID-prefix 2001:db8:0103::/48 is eligible to be   used by the ITR because it matches the second EID-prefix contained in   the EID-AD.   The EID-record with EID-prefix 2001:db8:0200::/40 is not eligible to   be used by the ITR since it is not included in any of the EID-ADs   signed by the Map-Server.  A log action MUST be taken.  In this last   example the ETR is trying to over claim the EID-prefix   2001:db8:0200::/40, but the Map-Server authorized only   2001:db8:0203::/48, 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 a Mapping   System such as LISP+ALT [RFC6836], 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 [RFC3394], 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 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.Maino, et al.             Expires May 20, 2017                 [Page 14]Internet-Draft                  LISP-SEC                   November 2016   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.   Protecting the confidentiality of the ITR-OTK and, in general, the   security of how the Map-Request is handed by the Map-Resolver to the   Map-Server, is specific to the particular Mapping System used, and   outside of the scope of this memo.   In Mapping Systems where the Map-Server is compliant with [RFC6833],   the Map-Resolver 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 to the Map-Server 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, and the Map-Reply will not be protected.   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.   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, theMaino, et al.             Expires May 20, 2017                 [Page 15]Internet-Draft                  LISP-SEC                   November 2016   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.   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.Maino, et al.             Expires May 20, 2017                 [Page 16]Internet-Draft                  LISP-SEC                   November 2016   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 Considerations6.1.  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 data6.3.  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".Maino, et al.             Expires May 20, 2017                 [Page 17]Internet-Draft                  LISP-SEC                   November 2016   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.7.  IANA Considerations7.1.  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                 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:Maino, et al.             Expires May 20, 2017                 [Page 18]Internet-Draft                  LISP-SEC                   November 2016             Name                     Value        Defined In             -------------------------------------------------             Reserved                 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                 0             This memo             NULL-KEY-WRAP-128        1             This memo             AES-KEY-WRAP-128         2             [RFC3394]                            Key Wrap FunctionsMaino, et al.             Expires May 20, 2017                 [Page 19]Internet-Draft                  LISP-SEC                   November 2016   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 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 supported8.  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   [RFC2104]  Krawczyk, H., Bellare, M., and R. Canetti, "HMAC: Keyed-              Hashing for Message Authentication", RFC 2104,              DOI 10.17487/RFC2104, February 1997,              <http://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,              <http://www.rfc-editor.org/info/rfc2119>.Maino, et al.             Expires May 20, 2017                 [Page 20]Internet-Draft                  LISP-SEC                   November 2016   [RFC3394]  Schaad, J. and R. Housley, "Advanced Encryption Standard              (AES) Key Wrap Algorithm", RFC 3394, DOI 10.17487/RFC3394,              September 2002, <http://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,              <http://www.rfc-editor.org/info/rfc4086>.   [RFC5226]  Narten, T. and H. Alvestrand, "Guidelines for Writing an              IANA Considerations Section in RFCs", BCP 26, RFC 5226,              DOI 10.17487/RFC5226, May 2008,              <http://www.rfc-editor.org/info/rfc5226>.   [RFC5869]  Krawczyk, H. and P. Eronen, "HMAC-based Extract-and-Expand              Key Derivation Function (HKDF)", RFC 5869,              DOI 10.17487/RFC5869, May 2010,              <http://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,              <http://www.rfc-editor.org/info/rfc6234>.   [RFC6830]  Farinacci, D., Fuller, V., Meyer, D., and D. Lewis, "The              Locator/ID Separation Protocol (LISP)", RFC 6830,              DOI 10.17487/RFC6830, January 2013,              <http://www.rfc-editor.org/info/rfc6830>.   [RFC6833]  Fuller, V. and D. Farinacci, "Locator/ID Separation              Protocol (LISP) Map-Server Interface", RFC 6833,              DOI 10.17487/RFC6833, January 2013,              <http://www.rfc-editor.org/info/rfc6833>.   [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, <http://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,              <http://www.rfc-editor.org/info/rfc7835>.Maino, et al.             Expires May 20, 2017                 [Page 21]Internet-Draft                  LISP-SEC                   November 2016Authors' 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   Damien Saucez   INRIA   2004 route des Lucioles - BP 93   Sophia Antipolis   France   Email: damien.saucez@inria.frMaino, et al.             Expires May 20, 2017                 [Page 22]