LISP-Security (LISP-SEC)Cisco Systems170 Tasman DriveSan Jose95134CaliforniaUSAfmaino@cisco.comGoogleCaliforniaUSAermagan@gmail.comUniversitat Politecnica de Catalunyac/ Jordi Girona s/nBarcelona08034Spainacabello@ac.upc.eduINRIA2004 route des Lucioles - BP 93Sophia AntipolisFrancedamien.saucez@inria.fr
Internet
Network Working GroupLISP; deploymentThis 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.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 BCP14 when, and only when, they
appear in all capitals, as shown here.The Locator/ID Separation Protocol , 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 , is built on top of the LISP
threat model defined in , 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-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 as those protocols are protected by the security
mechanisms specified in .
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.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
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 , or in a Map-Reply message to
support confidentiality, integrity protection, and verification of
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 .LISP-SEC addresses the control plane threats, described in section
3.7 and 3.8 of , 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
LISP-SEC assumes that any kind of attack, including MITM attacks, can be
mounted 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.The goal of the security mechanisms defined in is to prevent unauthorized insertion
of mapping data by providing origin authentication and integrity
protection for the 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 to address the threats described in
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, as described in , 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 exchange is as follows:Per each Map-Request message a new ITR-OTK is generated and
stored at the ITR, and securely transported to the Map-Server.The Map-Server uses the ITR-OTK to compute a Keyed-Hashing for
Message Authentication (HMAC) that protects
the integrity of the mapping data known to the Map-Server to prevent
overclaiming attacks. The Map-Server also derives a new OTK, the
MS-OTK, that is passed to the ETR, by applying a Key Derivation
Function (KDF) (e.g. ) to the ITR-OTK.The ETR uses the MS-OTK to compute an HMAC that protects the
integrity of the Map-Reply sent to the ITR.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. 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: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. 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 (as
specified in ), or by enabling DTLS
between the ITR and the Map-Resolver.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.
The LISP Mapping System delivers the ECM to the appropriate
Map-Server, as identified by the EID destination address of the
Map-Request. As mentioned in , 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.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.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. MS-OTK confidentiality and integrity
protection MUST be provided in the path between the Map-Server and
the ETR. This can be achieved either by encrypting the MS-OTK with
the pre-shared secret known to the Map-Server and the ETR (as
specified in ), or by enabling DTLS
between the Map-Server and the ETR.If the Map-Server is acting in proxy mode, as specified in , the ETR is not involved in the
generation of the 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 in .The ETR, upon receiving the ECM encapsulated Map-Request from the
Map-Server, decrypts the MS-OTK, if needed, and originates a
Map-Reply that contains the EID-to-RLOC mapping information as
specified in .The ETR computes an HMAC over 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 the complete Map-Reply message to the requesting ITR.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, 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.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.LISP-SEC uses the ECM defined in with 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 . OTK-AD stands for One-Time Key Authentication Data
and EID-AD stands for EID Authentication Data.ECM AD Type: 1 (LISP-SEC Authentication Data). See .V: Key Version bit. This bit is toggled when the sender
switches to a new OTK wrapping keyUnassigned: Set to 0 on transmission and ignored on
receipt.Requested HMAC ID: The HMAC algorithm, that will be used to
protect the mappings, requested by the ITR. See for details, and 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.Key ID: The identifier of the pre-shared secret shared by an
ITR and the Map-Resolver, and by the Map-Server and an ETR.
Per-message keys are derived from the pre-shared secret to
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 for more details,
and 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 for
details.One-Time-Key: the OTK wrapped as specified by OTK Wrapping ID.
See 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, and
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.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 , 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, and for HMAC IDs that MUST be
supported.EID mask-len: Mask length for EID-prefix.EID-AFI: Address family of EID-prefix according to 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 MUST cover the entire EID-AD.LISP-SEC uses the Map-Reply defined in , 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 . PKT-AD is the Packet
Authentication Data that covers the Map-Reply payload.MR AD Type: 1 (LISP-SEC Authentication Data). See .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 for more details,
and 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.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 for
more details, and for HMAC IDs that MUST be
supported.EID mask-len: Mask length for EID-prefix.EID-AFI: Address family of EID-prefix according to .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. See 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 for more details.This memo is allocating one of the bits marked as Unassigned in the
Map-Register message defined in . More precisely, the second bit
after the Type field in a Map-Register message is allocated as the S
bit. The S bit indicates to the Map-Server that the registering ETR is
LISP-SEC enabled. An ETR that supports LISP-SEC MUST set the S bit in
its Map-Register messages.Upon creating a Map-Request, the ITR generates a random ITR-OTK
that is stored locally (until the corresponding Map-Reply is
received), together with the nonce generated as specified in .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 ), 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.ITR-OTK is wrapped with the algorithm specified by the OTK Wrapping
ID field. See for further details on OTK
encryption. If the NULL-KEY-WRAP-128 algorithm 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.The processing performed by a PITR is equivalent to the
processing of an ITR. However, if the PITR is directly connected to
a Mapping System such as LISP+ALT , the PITR
performs the functions of both the ITR and the Map-Resolver
forwarding the Map-Request encapsulated in an ECM header that
includes the Authentication Data fields as described in .MS-OTK confidentiality and integrity protection MUST be provided in
the path between the Map-Server and the ETR. This can be achieved
either by enabling DTLS between the Map-Server and the ITR or by
encrypting the MS-OTK with the pre-shared secret known to the
Map-Server and the ETR .Similarly, 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 enabling DTLS between the Map-Server and the ITR,
or by encrypting the ITR-OTK with the pre-shared secret known to the
ITR and the Map-Resolver. The ITR/Map-Resolver pre-shared key is
similar to the Map-Server/ETR pre-shared key. However, to prevent
ETR's overclaiming attacks, the ITR/Map-Resolver pre-shared secret
MUST have a different value than the 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 note that, to prevent ETR's overclaiming attacks,
the ITR/Map-Resolver pre-shared secret MUST be different from the
Map-Server/ETR pre-shared secret.The OTK is wrapped using the algorithm specified in the OTK
Wrapping ID field. This field identifies both the:Key Encryption Algorithm used to encrypt the wrapped OTK, as
well as theKey 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 use of the
HKDF-SHA256 Key Derivation Function specified in to derive a per-message encryption key
(per-msg-key), as well as the AES-KEY-WRAP-128 Key Wrap algorithm used
to encrypt a 128-bit OTK, according to .The key wrapping process for OTK Wrapping ID
AES-KEY-WRAP-128+HKDF-SHA256 is described below:The KDF algorithm is identified by the field 'OTK Wrapping ID'
according to the table in Section .The Key Wrap algorithm is identified by the field 'OTK Wrapping
ID' according to the table in Section .If the NULL-KEY-WRAP-128 algorithm (defined
in ) is selected and DTLS is not enabled, the Map-Request
MUST be dropped and an appropiate log action SHOULD be taken.The pre-shared secret used to derive the per-msg-key is
represented by PSK[Key ID], that is the pre-shared secret
identified by the 'Key ID'.The per-message encryption key key is computed as: per-msg-key = KDF( nonce + s + PSK[Key ID] )where the nonce is the value in the Nonce field of the
Map-Request, and's' is the string "OTK-Key-Wrap"According to the per-msg-key is used
to wrap the 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 One-Time Key Preamble field,
while the 128 less significant bits are copied in the One-Time Key
field of the LISP-SEC Authentication Data.When decrypting an encrypted OTK the receiver MUST verify that the
Initialization Value resulting from the AES Key Wrap decryption
operation is equal to 0xA6A6A6A6A6A6A6A6. If this verification fails
the receiver MUST discard the entire message.MS-OTK confidentiality and integrity protection MUST be provided
in the path between the Map-Server and the ETR. Similarly, ITR-OTK
confidentiality and integrity protection MUST be provided in the
path between the ITR and the 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 128-bit OTK is sent unencrypted the OTK Wrapping ID is set
to NULL_KEY_WRAP_128, and the OTK Preamble is set to
0x0000000000000000 (64 bits).Upon receiving an encapsulated Map-Request with the S-bit set, the
Map-Resolver decapsulates the ECM message. The ITR-OTK, if encrypted,
is decrypted as specified in .Protecting the confidentiality of the ITR-OTK and, in general, the
security of how the Map-Request is handed by the Map-Resolver to the
Map-Server, is specific to the particular Mapping System used, and
outside of the scope of this memo.In Mapping Systems where the Map-Server is compliant with , the Map-Resolver originates a new
ECM header with the S-bit set, that contains the unencrypted ITR-OTK,
as specified in , and the other data
derived from the ECM Authentication Data of the received encapsulated
Map-Request.The Map-Resolver then forwards to the Map-Server the received
Map-Request, encapsulated in the new ECM header that includes the
newly computed Authentication Data fields.Upon receiving an ECM encapsulated Map-Request with the S-bit set
to 1, the Map-Server process the Map-Request according to the value of
the security-capable S-bit and of the proxy map-reply P-bit contained
in the Map-Register sent by the ETRs authoritative for that prefix
during registration.Processing of the Map-Request MUST proceed in the order described
in the table below, applying the processing corresponding to the first
rule that matches the conditions indicated in the first column:Matching ConditionProcessing1. At least one of the ETRs authoritative for the EID prefix
included in the Map-Request registered with the P-bit set to 1The Map-Server MUST generate a LISP-SEC protected Map-Reply as
specified in . The ETR-Cant-Sign E-bit in the
EID Authentication Data (EID-AD) MUST be set to 0.2. At least one of the ETRs authoritative for the EID prefix
included in the Map-Request registered with the S-bit set to 1The Map-Server MUST generate a LISP-SEC protected Encapsulated
Map-Request (as specified in ), to be sent to
one of the authoritative ETRs that registered with the S-bit set to
1 (and the P-bit set to 0). If there is at least one ETR that
registered with the S-bit set to 0, the ETR-Cant-Sign E-bit of the
EID-AD MUST be set to 1 to signal the ITR that a non LISP-SEC
Map-Request might reach additional ETRs that have LISP-SEC
disabled.3. All the ETRs authoritative for the EID prefix included in the
Map-Request registered with the S-bit set to 0The Map-Server MUST send a Negative Map-Reply protected with
LISP-SEC, as described in . The ETR-Cant-Sign
E-bit MUST be set to 1 to signal the ITR that a non LISP-SEC
Map-Request might reach additional ETRs that have LISP-SEC
disabled.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.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 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 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 provided
in the path between the Map-Server and the ETR. This can be achieved
either by enabling DTLS between the Map-Server and the ETR, or by
encrypting the MS-OTK with the pre-shared secret known to the
Map-Server and the ETR.The Map-Request MUST be 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 OTK
Wrapping ID field. See for further
details on OTK encryption. If the NULL-KEY-WRAP-128 algorithm is
selected and DTLS is not enabled in the path between the Map-Server
and the ETR, the Map-Request MUST be dropped and an appropiate log
action SHOULD be taken.The Map-Server includes in the EID-AD the longest match
registered EID-prefix for the destination EID, and an HMAC of this
EID-prefix. The HMAC is keyed with the ITR-OTK contained in the
received ECM Authentication Data, and the HMAC algorithm is chosen
according to the Requested HMAC ID field. If The Map-Server does not
support this algorithm, the Map-Server uses a different algorithm
and specifies it in the EID HMAC ID field. The scope of the HMAC
operation covers the entire EID-AD, from the EID-AD Length field to
the EID HMAC field, which must be set to 0 before the
computation.The Map-Server then forwards the updated ECM encapsulated
Map-Request, that contains the OTK-AD, the EID-AD, and the received
Map-Request to an authoritative ETR as specified in .LISP-SEC proxy Map-Reply are generated according to , with the Map-Replay S-bit set
to 1. The Map-Reply includes the Authentication Data that contains
the EID-AD, computed as specified in , as
well as the PKT-AD computed as specified in .Upon receiving an ECM encapsulated Map-Request with the S-bit set,
the ETR decapsulates the ECM message. The OTK field, if encrypted, is
decrypted as specified in to obtain the
unencrypted MS-OTK.The ETR then generates a Map-Reply as specified in and includes the Authentication
Data that contains the EID-AD, as received in the encapsulated
Map-Request, as well as the PKT-AD.The EID-AD is copied from the Authentication Data of the received
encapsulated Map-Request.The PKT-AD contains the HMAC of the whole Map-Reply packet, keyed
with the MS-OTK and computed using the HMAC algorithm specified in the
Requested HMAC ID field of the received encapsulated Map-Request. If
the ETR does not support the Requested HMAC ID, it uses a different
algorithm and updates the PKT HMAC ID field accordingly. The scope of
the HMAC operation covers the entire PKT-AD, from the Map-Reply Type
field to the PKT HMAC field, which must be set to 0 bendlfore the
computation.Finally the ETR sends the Map-Reply to the requesting ITR as
specified in .In response to an encapsulated Map-Request that has the S-bit set,
an ITR MUST receive a Map-Reply with the S-bit set, that includes an
EID-AD and a PKT-AD. If the Map-Reply does not include both ADs, the
ITR MUST discard it. In response to an encapsulated Map-Request with
S-bit set to 0, the ITR expects a Map-Reply with S-bit set to 0, and
the ITR SHOULD discard the Map-Reply if the S-bit is set.Upon receiving a Map-Reply, the ITR must verify the integrity of
both the EID-AD and the PKT-AD, and MUST discard the Map-Reply if one
of the integrity checks fails. After processing the Map-Reply, the ITR
must discard the <nonce,ITK-OTK> pair associated to the
Map-ReplyThe integrity of the EID-AD is verified using the ITR-OTK (stored
locally for the duration of this exchange) to re-compute the HMAC of
the EID-AD using the algorithm specified in the EID HMAC ID field. If
the EID HMAC ID field does not match the Requested HMAC ID the ITR
SHOULD discard the Map-Reply and send, at the first opportunity it
needs to, a new Map-Request with a different Requested HMAC ID field,
according to ITR's local policy. The scope of the HMAC operation
covers the entire EID-AD, from the EID-AD Length field to the EID HMAC
field, which must be set to 0 before the computation of the HMAC.ITR MUST set the EID HMAC ID field to 0 before computing the
HMAC.To verify the integrity of the PKT-AD, first the MS-OTK is derived
from the locally stored ITR-OTK using the algorithm specified in the
KDF ID field. This is because the PKT-AD is generated by the ETR using
the MS-OTK. If the KDF ID in the Map-Reply does not match the KDF ID
requested in the Map-Request, the ITR SHOULD discard the Map-Reply and
send, at the first opportunity it needs to, a new Map-Request with a
different KDF ID, according to ITR's local policy. Without consistent
configuration of involved entities, extra delays may be experienced.
However, since HKDF-SHA1-128 is specified as mandatory to implement in
, the process will eventually converge.The derived MS-OTK is then used to re-compute the HMAC of the
PKT-AD using the Algorithm specified in the PKT HMAC ID field. If the
PKT HMAC ID field does not match the Requested HMAC ID the ITR SHOULD
discard the Map-Reply and send, at the first opportunity it needs to,
a new Map-Request with a different Requested HMAC ID according to
ITR's local policy or until all HMAC IDs supported by the ITR have
been attempted.Each individual Map-Reply EID-record is considered valid only if:
(1) both EID-AD and PKT-AD are valid, and (2) the intersection of the
EID-prefix in the Map-Reply EID-record with one of the EID-prefixes
contained in the EID-AD is not empty. After identifying the Map-Reply
record as valid, the ITR sets the EID-prefix in the Map-Reply record
to the value of the intersection set computed before, and adds the
Map-Reply EID-record to its EID-to-RLOC cache, as described in . An example of Map-Reply record
validation is provided in .The ITR SHOULD send SMR triggered Map-Requests over the mapping
system in order to receive a secure Map-Reply. If an ITR accepts
piggybacked Map-Replies, it SHOULD also send a Map-Request over the
mapping system in order to verify the piggybacked Map-Reply with a
secure Map-Reply.The payload of a Map-Reply may contain multiple EID-records. The
whole Map-Reply is signed by the ETR, with the PKT HMAC, to provide
integrity protection and origin authentication to the EID-prefix
records claimed by the ETR. The Authentication Data field of a
Map-Reply may contain multiple EID-records in the EID-AD. The EID-AD
is signed by the Map-Server, with the EID HMAC, to provide integrity
protection and origin authentication to the EID-prefix records
inserted by the Map-Server.Upon receiving a Map-Reply with the S-bit set, the ITR first
checks the validity of both the EID HMAC and of the PKT-AD HMAC. If
either one of the HMACs is not valid, a log action MUST be taken and
the Map-Reply MUST NOT be processed any further. If both HMACs are
valid, the ITR proceeds with validating each individual EID-record
claimed by the ETR by computing the intersection of each one of the
EID-prefix contained in the payload of the Map-Reply with each one
of the EID-prefixes contained in the EID-AD. An EID-record is valid
only if at least one of the intersections is not the empty set.For instance, the Map-Reply payload contains 3 mapping record
EID-prefixes:2001:db8:102::/482001:db8:103::/482001:db8:200::/40The EID-AD contains two EID-prefixes: 2001:db8:103::/482001:db8:203::/48The EID-record with EID-prefix 2001:db8:102::/48 is not
eligible to be used by the ITR since it is not included in any of
the EID-ADs signed by the Map-Server. A log action MUST be
taken.The EID-record with EID-prefix 2001:db8:103::/48 is eligible to
be used by the ITR because it matches the second EID-prefix
contained in the EID-AD.The EID-record with EID-prefix 2001:db8:200::/40 is not eligible
to be used by the ITR since it is not included in any of the EID-ADs
signed by the Map-Server. A log action MUST be taken. In this last
example the ETR is trying to over claim the EID-prefix
2001:db8:200::/40, but the Map-Server authorized only
2001:db8:203::/48, hence the EID-record is discarded.The LISP-SEC threat model described in , 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.The ITR-OTK MUST be generated by a properly seeded pseudo-random
(or strong random) source. See for advice on
generating security-sensitive random dataIf 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.This memo is written according to .
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.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.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.DTLS 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.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.IANA is requested to create the "ECM Authentication Data Type"
registry with values 0-255, for use in the ECM LISP-SEC Extensions
. The registry MUST be initially
populated with the following values:Values 2-255 are unassigned. They are to be assigned according to
the "Specification Required" policy defined in .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 . The registry MUST be
initially populated with the following values:Values 2-255 are unassigned. They are to be assigned according to
the "Specification Required" policy defined in .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:Values 3-65535 are unassigned. They are to be assigned according to
the "Specification Required" policy defined in .AUTH-HMAC-SHA-1-96 MUST be supported, AUTH-HMAC-SHA-256-128 SHOULD
be supported.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:Values 3-65535 are unassigned. They are to be assigned according to
the "Specification Required" policy defined in .NULL-KEY-WRAP-128, and 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).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:Values 2-65535 are unassigned. They are to be assigned according to
the "Specification Required" policy defined in .HKDF-SHA1-128 MUST be supportedThe 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.