One document matched: draft-maino-lisp-sec-00.xml
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<rfc category="exp" docName="draft-maino-lisp-sec-00.txt" ipr="trust200902">
<front>
<title abbrev="LISP-SEC">LISP-Security (LISP-SEC)</title>
<author fullname="Fabio Maino" initials="F.M" surname="Maino">
<organization>Cisco Systems</organization>
<address>
<postal>
<street>170 Tasman Drive</street>
<city>San Jose</city>
<code>95134</code>
<region>California</region>
<country>USA</country>
</postal>
<email>fmaino@cisco.com</email>
</address>
</author>
<author fullname="Vina Ermagan" initials="V.E" surname="Ermagan">
<organization>Cisco Systems</organization>
<address>
<postal>
<street>170 Tasman Drive</street>
<city>San Jose</city>
<code>95134</code>
<region>California</region>
<country>USA</country>
</postal>
<email>vermagan@cisco.com</email>
</address>
</author>
<author fullname="Albert Cabellos" initials="A.C" surname="Cabellos">
<organization>Technical University of Catalonia</organization>
<address>
<postal>
<street>c/ Jordi Girona s/n</street>
<city>Barcelona</city>
<code>08034</code>
<region></region>
<country>Spain</country>
</postal>
<email>acabello@ac.upc.edu</email>
</address>
</author>
<author fullname="Damien Saucez" initials="D.S" surname="Saucez">
<organization>Universite catholique de Louvain</organization>
<address>
<postal>
<street>Place St. Barbe 2</street>
<city>Louvain-la-Neuve</city>
<code></code>
<region></region>
<country>Belgium</country>
</postal>
<email>damien.saucez@uclouvain.be</email>
</address>
</author>
<author fullname="Olivier Bonaventure" initials="O.B"
surname="Bonaventure">
<organization>Universite catholique de Louvain</organization>
<address>
<postal>
<street>Place St. Barbe 2</street>
<city>Louvain-la-Neuve</city>
<code></code>
<region></region>
<country>Belgium</country>
</postal>
<email>olivier.bonaventure@uclouvain.be</email>
</address>
</author>
<date day="4" month="March" year="2011" />
<area>Internet</area>
<workgroup>Network Working Group</workgroup>
<keyword>LISP; deployment</keyword>
<abstract>
<t>This memo specifies LISP-SEC, a set of security mechanisms that
provide origin authentication, integrity and anti-replay protection to
LISP's EID-to-RLOC mapping data. LISP-SEC also enables verification of
authorization on EID prefix claims.</t>
</abstract>
<note title="Requirements Language">
<t>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 <xref
target="RFC2119"></xref>.</t>
</note>
</front>
<middle>
<section anchor="intro" title="Introduction">
<t>The Locator/ID Separation Protocol <xref
target="I-D.ietf-lisp"></xref> defines a set of functions for routers to
exchange information used to map from non-routable Endpoint Identifiers
(EIDs) to routable Routing Locators (RLOCs). If these EID-to-RLOC
mappings, carried through Map-Reply messages, are transmitted without
integrity protection, an adversary can manipulate them and hijack the
communication, impersonate the requested EID or mount Denial of Service
or Distributed Denial of Service attacks. Also, if the Map-Reply message
is transported unauthenticated, an adversarial LISP entity can overclaim
an EID-prefix and maliciously redirect traffic directed to a large
number of hosts. A detailed description of "overclaiming" attack is
provided in <xref target="I-D.saucez-lisp-security"></xref>.</t>
<t>This memo specifies LISP-SEC, a set of sceurity mechanisms that
provide origin authentication, integrity and anti-replay protection to
LISP's EID-to-RLOC mapping data. LISP-SEC also enables verification of
authorization on EID prefix claims, ensuring that the entity that
provides the location for a given EID prefix is entitled to do so.</t>
</section>
<section anchor="terms" title="Definition of Terms">
<t><list style="empty">
<t>One-Time Key (OTK): An ephemeral randomly generated key that must
be used for a single Map-Request/Map-Reply exchange.</t>
<t>Encapsulated Control Message (ECM): A LISP control message that
is prepended with an additional LISP header. ECM is used by ITRs to
send LISP control messages to a Map-Resolver, by Map-Resolvers to
forward LISP control messages to a Map-Server, and by Map-Resolvers
to forward LISP control messages to an ETR.</t>
<t>Authentication Data (AD): Metadata that is included either in a
LISP ECM header or in a Map-Reply message to support
confidentiality, integrity protection, and verification of EID
prefix authorization.</t>
</list> 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 <xref target="I-D.ietf-lisp"></xref>.</t>
</section>
<section anchor="threat-model" title="LISP-SEC Threat Model">
<t>LISP-SEC addresses the control plane threats, described in <xref
target="I-D.saucez-lisp-security"></xref>, that target EID-to-RLOC
mappings, including manipulations of Map-Request and Map-Reply messages,
and malicious xTR EID overclaiming. However LISP-SEC makes two main
assumptions that are not part of <xref
target="I-D.saucez-lisp-security"></xref>. First, the LISP Mapping
System is expected to deliver Map-Request messages to their intended
destinations as identified by the EID. Second, no Man-in-the-Middle
(MiM) attack can be mounted within the LISP Mapping System.</t>
<t>Accordingly to the threat model described in <xref
target="I-D.saucez-lisp-security"></xref> LISP-SEC assumes that any kind
of attack, including MiM 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 service system can, for instance,
hijack mapping requests and replies, spoofing the identity of a LISP
node. Another example of on-path attack, called over claiming attack,
can be mounted by a malicious Egress Tunnel Router (ETR), by over
claiming the EID prefixes for which it is authoritative. In this way the
ETR can maliciously redirect traffic directed to a large number of
hosts.</t>
</section>
<section anchor="operations" title="Protocol Operations">
<t>The goal of the security mechanisms defined in <xref
target="I-D.ietf-lisp"></xref> 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.</t>
<t>LISP-SEC builds on top of the security mechanisms defined in <xref
target="I-D.ietf-lisp"></xref> to address the threats described in <xref
target="threat-model"></xref> 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 protocol
data, and that effectively prevent over claiming attacks. The processing
of security parameters during the Map-Request/Map-Reply exchange is as
follows:</t>
<t><list style="symbols">
<t>The OTK is generated and stored at the ITR, and securely
transported to the Map-Server.</t>
<t>The Map-Server uses the OTK to compute an HMAC that protects the
integrity of the mapping data provided by the Map-Server to prevent
overclaiming attacks. The Map-Server also derives a new OTK
(OTK-ETR), by applying a Key Derivation Function (KDF) to the
original OTK, that is passed to the ETR.</t>
<t>The ETR uses the new OTK to compute an HMAC that protects the
integrity of the Map-Reply sent to the ITR.</t>
<t>Finally, the ITR uses the stored 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.</t>
</list></t>
<t><xref target="encap"></xref> 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:</t>
<t><list style="symbols">
<t>The ITR, upon transmitting a Map-Request message, generates and
stores an OTK. This key is included into the Encapsulated Control
Message (ECM) that contains the Map-Request sent to the
Map-Resolver. To provide OTK confidentiality over the path between
the ITR and its Map-Resolver, the OTK SHOULD be encrypted using a
preconfigured key shared between the ITR and the Map-Resolver,
similar to the key shared between the ETR and the Map-Server in
order to secure ETR registration <xref
target="I-D.ietf-lisp-ms"></xref>.</t>
<t>The Map-Resolver decapsulates the ECM message, decrypts the OTK,
if needed, and forwards through the Mapping System the received
Map-Request and the OTK, as part of a new ECM message. As described
in <xref target="map-resolver"></xref>, the LISP Mapping System
delivers the ECM to the appropriate Map-Server, as identified by the
EID destination address of the Map-Request.</t>
<t>The Map-Server is configured with the location mappings and
policy information for the ETR responsible for the destination EID
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 OTK, to a new Encapsulated Control Message that contains
the received Map-Request.</t>
<t>The Map-Server derives a new OTK (OTK-ETR) by applying a Key
Derivation Function (KDF) to the OTK. This new OTK is included in
the Encapsulated Control Message sent to the ETR. To provide OTK
confidentiality over the path between the Map-Server and the ETR,
the new OTK should be encrypted using the key shared between the ETR
and the Map-Server in order to secure ETR registration <xref
target="I-D.ietf-lisp-ms"></xref>.</t>
<t>If the Map-Server is acting in proxy mode, as specified in <xref
target="I-D.ietf-lisp"></xref>, the ETR is not involved in the
origination of the Map-Reply. In this case the Map-Server originates
the Map-Reply on behalf of the ETR as described below.</t>
<t>The ETR, upon receiving the Encapsulated Map-Request from the
Map-Server, decrypts the OTK-ETR, if needed, and originates a
Map-Reply that contains the EID-to-RLOC mapping information as
specified in <xref target="I-D.ietf-lisp"></xref>.</t>
<t>The ETR computes an HMAC over the original LISP Map-Reply, keyed
with OTK-ETR 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 Encapsulated Map-Request into the
Map-Reply message.</t>
<t>The ITR, upon receiving the Map-Reply, uses the locally stored
OTK to verify the integrity of the EID prefix authorization data
included in the Map-Reply by the Map-Server. The ITR computes
OTK-ETR 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 prefix
claimed by the ETR in the Map-Reply is less specific than the EID
prefix authorization data inserted by the Map-Server, the ITR MUST
discard the Map-Reply.</t>
</list></t>
</section>
<section anchor="encap" title="LISP-SEC Control Messages Details">
<t>LISP-SEC metadata associated with a Map-Request is transported within
the Encapsulated Control Message that contains the Map-Request.</t>
<t>LISP-SEC metadata associated with the Map-Reply is transported within
the Map-Reply itself.</t>
<section title="Encapsulated Control Message LISP-SEC Extensions">
<t>LISP-SEC uses the ECM (Encapsulated Control Message) defined in
<xref target="I-D.ietf-lisp"></xref> 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.</t>
<figure align="center" title="LISP-SEC ECM Authentication Data">
<artwork align="center"><![CDATA[
0 1 2 3
0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| AD Type |V| Reserved | Requested HMAC ID |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+\
| OTK Length | OTK Encryption ID | |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ |
| One-Time-Key Preamble ... | |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ OTK-AD
| ... One-Time-Key Preamble | |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ |
~ One-Time Key (128 bits) ~/
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+\
| EID AD Length | KDF ID | |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ |
| Reserved | EID HMAC ID | |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ |
| Reserved | EID mask-len | EID-AFI | EID-AD
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ |
~ EID prefix ... ~ |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ |
~ EID HMAC (160 bits) ~ |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+/ ]]></artwork>
</figure>
<t><list style="empty">
<t>AD Type: 1 (LISP-SEC Authentication Data)</t>
<t>V: Key Version bit. This bit is toggled when the sender
switches to a new OTK wrapping key</t>
<t>Reserved: Set to 0 on transmission and ignored on receipt.</t>
<t>Requested HMAC ID: the HMAC algorithm requested by the ITR. See
<xref target="itr"></xref> for details.</t>
<t>OTK Length: The length (in bytes) of the OTK Authentication
Data (OTK-AD), that contains the OTK Preamble and the OTK.</t>
<t>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 <xref target="encryption"></xref> for more
details.</t>
<t>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 <xref
target="encryption"></xref> for details.</t>
<t>One-Time-Key: the OTK encrypted (or not) as specified by OTK
Encryption ID. See <xref target="encryption"></xref> for
details.</t>
<t>EID AD Length: length (in bytes) of the EID Authentication Data
(EID-AD). The ITR MUST set EID AD Length to 32, as it only fills
the KDF ID field, and all the remaining fields part of the EID-AD
are not present.</t>
<t>KDF ID: Identifier of the Key Derivation Function used to
derive OTK-ETR. The ITR SHOULD use this field to indicate the
recommended KDF algorithm, according to local policy. The
Map-Server can overwrite the KDF ID if it does not support the KDF
ID recommended by the ITR. See Section 5.4 for more details.</t>
<t>Reserved: Set to 0 on transmission and ignored on receipt.</t>
<t>EID HMAC ID: Identifier of the HMAC algorithm used to protect
the integrity of the EID prefix authorization fields. This field
is filled by Map-Server that computed the EID prefix HMAC. See
Section 5.4 for more details.</t>
<t>EID mask-len: Mask length for EID prefix.</t>
<t>EID-AFI: Address family of EID-prefix according to <xref
target="RFC5226"></xref></t>
<t>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.</t>
<t>EID HMAC: HMAC of the EID prefix authorization fields that is
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.</t>
</list></t>
</section>
<section anchor="map-reply" title="Map-Reply LISP-SEC Extensions">
<t>LISP-SEC uses the Map-Reply defined in <xref
target="I-D.ietf-lisp"></xref>, 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. LOC-AD stands for LOC Authentication
Data.</t>
<figure align="center" title="LISP-SEC Map-Reply Authentication Data">
<artwork align="center"><![CDATA[ 0 1 2 3
0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| AD Type | Reserved |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+\
| EID AD Length | KDF ID | |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ |
| Reserved | EID HMAC ID | |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ |
| Reserved | EID mask-len | EID-AFI | EID-AD
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ |
~ EID prefix ... ~ |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ |
~ EID HMAC (160 bits) ~ |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+/
| LOC AD Length | LOC HMAC ID |\
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ |
~ LOC HMAC (160 bits) ~ LOC-AD
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+/ ]]></artwork>
</figure>
<t><list style="empty">
<t>AD Type: 1 (LISP-SEC Authentication Data)</t>
<t>EID AD Length: length (in bytes) of the EID-AD.</t>
<t>KDF ID: Identifier of the Key Derivation Function used to
derive OTK-ETR. See <xref target="map-server"></xref> for more
details.</t>
<t>Reserved: Set to 0 on transmission and ignored on receipt.</t>
<t>EID HMAC ID: Identifier of the HMAC algorithm used to protect
the integrity of the EID prefix authorization fields. See <xref
target="map-server"></xref> for more details.</t>
<t>EID mask-len: Mask length for EID prefix.</t>
<t>EID-AFI: Address family of EID-prefix according to <xref
target="RFC5226"></xref>.</t>
<t>EID prefix: This field contains the EID prefix that the
destination ETR is authoritative for, and is the longest match for
the requested EID.</t>
<t>EID HMAC: HMAC of the EID prefix authorization fields. Before
computing the HMAC operation the EID HMAC field MUST be set to
0.</t>
<t>LOC AD Length: length (in bytes) of the Map-Reply Location
Authentication Data (LOC-AD).</t>
<t>LOC HMAC ID: Identifier of the HMAC algorithm used to protect
the integrity of the Map-reply Location Data.</t>
<t>LOC HMAC: HMAC of the Map-reply Location Data. The scope of the
authentication covers the whole Map-Reply Payload (from Type to
Mapping Protocol Data fields included). See <xref
target="etr"></xref> for more details.</t>
</list></t>
</section>
<section anchor="itr" title="ITR Processing">
<t>Upon creating a Map-Request, the ITR generates a random OTK that is
stored locally, together with the nonce generated as specified in
<xref target="I-D.ietf-lisp"></xref>.</t>
<t>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 OTK
confidentiality SHOULD be protected by wrapping the OTK with the
algorithm specified by the OTK Encryption ID field. See <xref
target="encryption"></xref> for further details on OTK encryption.</t>
<t>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.</t>
<t>The KDF ID field, specifies the suggested key derivation function
to be used by the Map-Server to derive the OTK-ETR.</t>
<t>The EID AD length is set to 32, since the Authentication Data does
not contain EID prefix Authentication Data, and the EID-AD contains
only the KDF ID field.</t>
<t>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 LOC 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.</t>
<t>Upon receiving a Map-Reply, the ITR must verify the integrity of
both the EID-AD and the LOC-AD, and MUST discard the Map-Reply if one
of the integrity checks fails.</t>
<t>The integrity of the EID-AD is verified using the locally stored
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 a new
Map-Request with a different Requested HMAC ID field, according to
ITR's local policy. The ITR MUST set the EID HMAC ID field to 0 before
computing the HMAC.</t>
<t>To verify the integrity of the LOC-AD, first the OTK-ETR is derived
from the locally stored OTK using the algorithm specified in the KDF
ID field. This is because the LOC AD is generated by the ETR using the
OTK-ETR. 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 a new Map-Request with a different KDF ID, according to ITR's
local policy. The derived OTK-ETR is then used to re-compute the HMAC
of the LOC-AD using the Algorithm specified in the LOC HMAC ID field.
If the LOC HMAC ID field does not match the Requested HMAC ID the ITR
SHOULD discard the Map-Reply, and send a new Map-Request with a new
Required HMAC ID according to ITR's local policy.</t>
<t>The Map-Reply is considered a valid Map-Reply only if: (1) both
EID-AD and LOC-AD are valid, and (2) the EID prefixes in the Map-Reply
records are equal to or more specific than the EID prefix in the
EID-AD. After identifying the Map-Reply as valid, the ITR proceeds to
adding the Map-Reply records to its EID-to-RLOC cache, as described in
<xref target="I-D.ietf-lisp"></xref>.</t>
<t>The ITR SHOULD send SMR triggered Map Requests over the mapping
system in order to receive a secure Map-Reply. If an ITR accepts
piggybacked Map-Replies, it SHOULD also send a Map-Request over the
mapping system in order to securely verify the piggybacked
Map-Reply.</t>
</section>
<section anchor="encryption" title="Encrypting and Decrypting an OTK ">
<t>If OTK confidentiality is required in the path between the
Map-Server and the ETR, the OTK SHOULD be encrypted using the
preconfigured key shared between the Map-Server and the ETR for the
purpose of securing ETR registration <xref
target="I-D.ietf-lisp-ms"></xref>. Similarly, if OTK confidentiality
is required in the path between the ITR and the Map-Resolver, the OTK
SHOULD be encrypted with a key shared between the ITR and the
Map-Resolver.</t>
<t>The OTK is encrypted using the algorithm specified in the OTK
Encryption ID field. When the AES Key Wrap algorithm is used to
encrypt a 128-bit OTK, according to [RFC3339], the AES Key Wrap
Initialization Value MUST be set to 0xA6A6A6A6A6A6A6A6 (64 bits). The
output of the AES Key Wrap operation is 192-bit long. The most
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.</t>
<t>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.</t>
<t>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).</t>
</section>
<section anchor="map-resolver" title="Map-Resolver Processing">
<t>Upon receiving an encapsulated Map-Request with the S-bit set, the
Map-Resolver decapsulates the ECM message. The OTK, if encrypted, is
decrypted as specified in <xref target="encryption"></xref>.</t>
<t>The Map-Resolver, as specified in <xref
target="I-D.ietf-lisp-ms"></xref>, originates a new ECM header with
the S-bit set, that contains the unencrypted OTK, as specified in
<xref target="encryption"></xref>, and the other data derived from the
ECM Authentication Data of the received encapsulated Map-Request.</t>
<t>The Map-Resolver then forwards the received Map-Request,
encapsulated in the new ECM header that includes the newly computed
Authentication Data fields.</t>
</section>
<section anchor="map-server" title="Map-Server Processing">
<t>Upon receiving an encapsulated Map-Request with the S-bit 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.</t>
<t>The Map-Server updates the OTK-AD by deriving a new OTK (OTK-ETR)
from the OTK received with the Map-Request. OTK-ETR is derived
applying the key derivation function specified in the KDF ID field. If
the algorithm specified in the KDF ID field is not supported, the
Map-Server uses a different algorithm to derive the key and updates
the KDF ID field accordingly.</t>
<t>The Map-Server and the ETR MUST be configured with a shared key for
mapping registration according to <xref
target="I-D.ietf-lisp-ms"></xref>. If OTK confidentiality is required,
then the OTK-ETR SHOULD be encrypted, by wrapping the OTK-ETR with the
algorithm specified by the OTK Encryption ID field as specified in
<xref target="encryption"></xref>.</t>
<t>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 OTK in the ECM Authentication Data that is
received from ITR, 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.</t>
<t>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 <xref
target="I-D.ietf-lisp"></xref>.</t>
<section anchor="proxy" title="Map-Server Processing in Proxy mode">
<t>If the Map-Server is in proxy mode, it generates a Map-Reply, as
specified in <xref target="I-D.ietf-lisp"></xref>, with the S-bit
set to 1. The Map-Reply includes the Authentication Data that
contains the EID AD, computed as specified in <xref
target="map-server"></xref>, as well as the LOC-AD computed as
specified in <xref target="etr"></xref>.</t>
</section>
</section>
<section anchor="etr" title="ETR Processing">
<t>Upon receiving an encapsulated Map-Request with the S-bit set, the
ETR decapsulates the ECM message. The OTK field, if encrypted, is
decrypted as specified in <xref target="encryption"></xref> to obtain
the unencrypted OTK-ETR.</t>
<t>The ETR then generates a Map-Reply as specified in <xref
target="I-D.ietf-lisp"></xref> and includes an Authentication Data
that contains the EID-AD, as received in the encapsulated Map-Request,
as well as the LOC-AD.</t>
<t>The EID-AD is copied from the Authentication Data of the received
encapsulated Map-Request.</t>
<t>The LOC-AD contains the HMAC of the whole Map-Reply message, keyed
with the OTK-ETR and computed using the HMAC algorithm specified in
the Requested HMAC ID field of the received encapsulated Map-Request.
If the ETR does not support the Requested HMAC ID, it uses a different
algorithm and updates the LOC HMAC ID field accordingly. Finally the
ETR sends the Map-Reply to the requesting ITR as specified in <xref
target="I-D.ietf-lisp"></xref>.</t>
</section>
</section>
<section anchor="security" title="Security Considerations">
<t></t>
<section anchor="mapping-system" title="Mapping System Security">
<t>The LISP-SEC threat model described in <xref
target="threat-model"></xref>, 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.</t>
<t>Security is not yet embedded in LISP+ALT but BGP route filtering
SHOULD be deployed in the ALT infrastructure to enforce proper routing
in the mapping system. The SIDR working group is currently addressing
prefix and route advertisement authorization and authentication for
BGP. While following SIDR recommendations in the global Internet will
take time, applying these recommendations to the ALT, which relies on
BGP, should be less complex, as ALT is currently small and with a
limited number of operators. Ultimately, deploying the SIDR
recommendations in ALT further ensures that the fore mentioned
assumption is true.</t>
<t>It is also assumed that no man-in-the-middle attack can be carried
out against the ALT router to ALT router tunnels, and that the
information included into the Map-Requests, in particular the OTK,
cannot be read by third-party entities. It should be noted that the
integrity of the Map-Request in the ALT is protected by BGP
authentication, and that in order to provide OTK confidentiality in
the ALT mapping system the ALT router to ALT router tunnels MAY be
deployed using GRE+IPSec.</t>
</section>
<section anchor="random" title="Random Number Generation">
<t>The OTK MUST be generated by a properly seeded pseudo-random (or
strong random) source. See <xref target="RFC4086"></xref> for advice
on generating security-sensitive random data</t>
</section>
</section>
<section anchor="IANA" title="IANA Considerations">
<t></t>
<section anchor="HMAC" title="HMAC functions">
<t>The following HMAC ID values are defined by this memo for use as
Requested HMAC ID, EID HMAC ID, and LOC HMAC ID in the LISP-SEC
Authentication Data:</t>
<t><figure align="center" suppress-title="true" title="HMAC Functions">
<artwork align="center"><![CDATA[
Name Number Defined In
-------------------------------------------------
NONE 0
AUTH-HMAC-SHA-1-160 1 [RFC2104]
AUTH-HMAC-SHA-256-128 2 [RFC4634]
values 2-65535 are reserved to IANA.]]></artwork>
</figure></t>
<t>AUTH-HMAC-SHA-1-160 MUST be supported, AUTH-HMAC-SHA-256-128 should
be supported.</t>
</section>
<section anchor="wrap" title="Key Wrap Functions">
<t>The following OTK Encryption ID values are defined by this memo for
use as OTK key wrap algorithms ID in the LISP-SEC Authentication
Data:</t>
<figure align="center" suppress-title="true"
title="Key Wrap Functions">
<artwork align="center"><![CDATA[
Name Number Defined In
-------------------------------------------------
NULL-KEY-WRAP-128 1
AES-KEY-WRAP-128 2 [RFC3394]
values 0 and 3-65535 are reserved to IANA.]]></artwork>
</figure>
<t>NULL-KEY-WRAP-128, and AES-KEY-WRAP-128 MUST be supported.</t>
<t>NULL-KEY-WRAP-128 is used to carry an unencrypted 128-bit OTK, with
a 64-bit preamble set to 0x0000000000000000 (64 bits).</t>
</section>
<section anchor="kdf" title="Key Derivation Functions">
<t>The following KDF ID values are defined by this memo for use as KDF
ID in the LISP-SEC Authentication Data:</t>
<figure align="center" suppress-title="true"
title="Key Derivation Functions">
<artwork align="center"><![CDATA[
Name Number Defined In
-------------------------------------------------
NONE 0
HKDF-SHA1-128 1 [RFC5869]
values 2-65535 are reserved to IANA.]]></artwork>
</figure>
<t>HKDF-SHA1-128 MUST be supported</t>
</section>
</section>
<section anchor="Acknowledgements" title="Acknowledgements">
<t>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.</t>
</section>
</middle>
<back>
<references title="Normative References">
<?rfc include="http://xml.resource.org/public/rfc/bibxml3/reference.I-D.draft-ietf-lisp-10.xml"?>
<?rfc include="http://xml.resource.org/public/rfc/bibxml3/reference.I-D.draft-ietf-lisp-interworking-01.xml"?>
<?rfc include="http://xml.resource.org/public/rfc/bibxml3/reference.I-D.draft-ietf-lisp-ms-06.xml"?>
<?rfc include="http://xml.resource.org/public/rfc/bibxml3/reference.I-D.saucez-lisp-security.xml"?>
<?rfc include="reference.RFC.2119"?>
<?rfc include="reference.RFC.5226"?>
<?rfc include="reference.RFC.4086"?>
<?rfc include="reference.RFC.2104"?>
<?rfc include="reference.RFC.3394"?>
<?rfc include="reference.RFC.5869"?>
</references>
</back>
</rfc>
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