wdiff draft-ietf-lisp-sec-17.txt draft-ietf-lisp-sec-18.txt

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

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

Abstract

Requirements Language

The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT",
"SHOULD", "SHOULD NOT", "RECOMMENDED", "MAY", and "OPTIONAL" in this
document are to be interpreted as described in [RFC2119]. BCP14 [RFC2119]
[RFC8174] when, and only when, they appear in all capitals, as shown
here.

Status of This Memo

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

Internet-Drafts are working documents of the Internet Engineering
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 June 2, December 4, 2019.

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
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described in the Simplified BSD License.

Table of Contents

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

1. Introduction

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

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

2. Definition of Terms

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

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

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

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

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

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

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

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

3. LISP-SEC Threat Model

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

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

4. Protocol Operations

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

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

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

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

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

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

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

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

o Map-Resolver.

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

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

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

o Map-
Request.

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

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

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

o in Section 5.7.2.

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

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

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

5. LISP-SEC Control Messages Details

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

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

5.1. Encapsulated Control Message LISP-SEC Extensions

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

Figure 1: LISP-SEC ECM Authentication Data

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

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

Reserved:

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

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

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

OTK Encryption

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

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

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

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

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

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

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

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

Reserved:

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

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

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

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

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

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

5.2. Map-Reply LISP-SEC Extensions

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

Figure 2: LISP-SEC Map-Reply Authentication Data

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

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

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

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

Reserved:

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

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

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

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

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

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

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

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

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

5.3. Map-Register LISP-SEC Extentions

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

5.4. ITR Processing Processing: Generating a Map-Request

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

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

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

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

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

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

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

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

In response

5.4.1. PITR Processing

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

5.5. Encrypting and Decrypting an
EID-AD OTK

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

5.5.1. Unencrypted OTK

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

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

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

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

5.6. Map-Resolver Processing

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

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

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

5.4.1. Map-Reply Record Validation

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

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

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

5.7. Map-Server Processing

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

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

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

2001:db8:0102::/48

2001:db8:0103::/48

2001:db8:0200::/40

The EID-AD contains two EID-prefixes:

2001:db8:0103::/48

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

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

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

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

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

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

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

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

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

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

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

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

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

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

5.7.2. Generating a Proxy Map-Reply

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

5.8. ETR Processing

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

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

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

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

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

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

5.9. ITR Processing: Receiving a Map-Reply

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

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

5.6. Map-Resolver Processing

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

Protecting set.

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

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

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

5.7. Map-Server Processing

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

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

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

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

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

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

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

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

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

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

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

5.9.1. Map-Reply Record Validation

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

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

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

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

5.8. ETR Processing Map-Server.

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

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

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

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

2001:db8:102::/48

2001:db8:103::/48

2001:db8:200::/40

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

2001:db8:103::/48

2001:db8:203::/48

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

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

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

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

6. Security Considerations

6.1. Mapping System Security

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

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

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

6.2. Random Number Generation

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

6.3. Map-Server and ETR Colocation

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

6.4. Deploying LISP-SEC

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

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

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

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

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

6.5. Shared Keys Provisioning

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

6.6. Replay Attacks

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

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

6.7. Message Privacy

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

6.8. Denial of Service and Distributed Denial of Service Attacks

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

7. IANA Considerations

7.1. ECM AD Type Registry

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

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

HMAC Functions

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

7.2. Map-Reply AD Type Registry

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

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

HMAC Functions

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

7.3. HMAC Functions

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

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

HMAC Functions

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

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

7.4. Key Wrap Functions

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

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

Key Wrap Functions

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

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

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

7.5. Key Derivation Functions

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

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

Key Derivation Functions

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

HKDF-SHA1-128 MUST be supported

8. Acknowledgements

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

9. References

9.1. Normative References

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

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

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

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

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

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

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

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

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

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

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

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

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

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

[RFC8174] Leiba, B., "Ambiguity of Uppercase vs Lowercase in RFC
2119 Key Words", BCP 14, RFC 8174, DOI 10.17487/RFC8174,
May 2017, <https://www.rfc-editor.org/info/rfc8174>.

9.2. Informative References

Authors' Addresses

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

Email: fmaino@cisco.com

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

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

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

Email: acabello@ac.upc.edu

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

Email: damien.saucez@inria.fr