| Network Working Group | F.M. Maino |
| Internet-Draft | V.E. Ermagan |
| Intended status: Experimental Protocol | Cisco Systems |
| Expires: September 06, 2011 | A.C. Cabellos |
| Technical University of Catalonia | |
| D.S. Saucez | |
| O.B. Bonaventure | |
| Universite catholique de Louvain | |
| March 05, 2011 |
LISP-Security (LISP-SEC)
draft-maino-lisp-sec-00.txt
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.
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].
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/.
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This Internet-Draft will expire on September 06, 2011.
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The Locator/ID Separation Protocol [I-D.ietf-lisp] defines a set of functions for routers to exchange information used to map from non-routable Endpoint Identifiers (EIDs) to routable Routing Locators (RLOCs). If these EID-to-RLOC mappings, carried through Map-Reply messages, are transmitted without integrity protection, an adversary can manipulate them and hijack the communication, impersonate the requested EID or mount Denial of Service or Distributed Denial of Service attacks. Also, if the Map-Reply message is transported unauthenticated, an adversarial LISP entity can overclaim an EID-prefix and maliciously redirect traffic directed to a large number of hosts. A detailed description of "overclaiming" attack is provided in [I-D.saucez-lisp-security].
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.
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 [I-D.saucez-lisp-security], 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 [I-D.saucez-lisp-security]. 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.
Accordingly to the threat model described in [I-D.saucez-lisp-security] 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.
The goal of the security mechanisms defined in [I-D.ietf-lisp] is to prevent unauthorized insertion of mapping data, by providing origin authentication and integrity protection for the Map-Registration, and by using the nonce to detect unsolicited Map-Reply sent by off-path attackers.
LISP-SEC builds on top of the security mechanisms defined in [I-D.ietf-lisp] to address the threats described in Section 3 by leveraging the trust relationships existing among the LISP entities participating to the exchange of the Map-Request/Map-Reply messages. Those trust relationships are used to securely distribute a One-Time Key (OTK) that provides origin authentication, integrity and anti-replay protection to mapping protocol data, and that effectively prevent over claiming attacks. The processing of security parameters during the Map-Request/Map-Reply exchange is as follows:
Section 5 provides the detailed description of the LISP-SEC control messages and their processing, while the rest of this section describes the flow of protocol operations at each entity involved in the Map-Request/Map-Reply exchange:
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 (Encapsulated Control Message) defined in [I-D.ietf-lisp] with Type set to 8, and S bit set to 1 to indicate that the LISP header includes Authentication Data (AD). The format of the LISP-SEC ECM Authentication Data is defined in the following figure. OTK-AD stands for One-Time Key Authentication Data and EID-AD stands for EID Authentication Data.
0 1 2 3 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | AD Type |V| Reserved | Requested HMAC ID | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+\ | OTK Length | OTK Encryption ID | | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | | One-Time-Key Preamble ... | | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ OTK-AD | ... One-Time-Key Preamble | | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | ~ One-Time Key (128 bits) ~/ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+\ | EID AD Length | KDF ID | | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | | Reserved | EID HMAC ID | | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | | Reserved | EID mask-len | EID-AFI | EID-AD +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | ~ EID prefix ... ~ | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | ~ EID HMAC (160 bits) ~ | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+/
LISP-SEC uses the Map-Reply defined in [I-D.ietf-lisp], 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.
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 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+/
Upon creating a Map-Request, the ITR generates a random OTK that is stored locally, together with the nonce generated as specified in [I-D.ietf-lisp].
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 Section 5.4 for further details on OTK encryption.
The Requested HMAC ID field contains the suggested HMAC algorithm to be used by the Map-Server and the ETR to protect the integrity of the ECM Authentication data and of the Map-Reply.
The KDF ID field, specifies the suggested key derivation function to be used by the Map-Server to derive the OTK-ETR.
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.
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.
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.
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.
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.
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 [I-D.ietf-lisp].
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.
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 [I-D.ietf-lisp-ms]. 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.
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.
When decrypting an encrypted OTK the receiver MUST verify that the Initialization Value resulting from the AES Key Wrap decryption operation is equal to 0xA6A6A6A6A6A6A6A6. If this verification fails the receiver MUST discard the entire message.
When a 128-bit OTK is sent unencrypted the OTK Encryption ID is set to NULL_KEY_WRAP_128, and the OTK Preamble is set to 0x0000000000000000 (64 bits).
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 Section 5.4.
The Map-Resolver, as specified in [I-D.ietf-lisp-ms], originates a new ECM header with the S-bit set, that contains the unencrypted OTK, as specified in Section 5.4, and the other data derived from the ECM Authentication Data of the received encapsulated Map-Request.
The Map-Resolver then forwards the received Map-Request, encapsulated in the new ECM header that includes the newly computed Authentication Data fields.
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.
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.
The Map-Server and the ETR MUST be configured with a shared key for mapping registration according to [I-D.ietf-lisp-ms]. 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 Section 5.4.
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.
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 [I-D.ietf-lisp].
If the Map-Server is in proxy mode, it generates a Map-Reply, as specified in [I-D.ietf-lisp], with the S-bit set to 1. The Map-Reply includes the Authentication Data that contains the EID AD, computed as specified in Section 5.6, as well as the LOC-AD computed as specified in Section 5.7.
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 Section 5.4 to obtain the unencrypted OTK-ETR.
The ETR then generates a Map-Reply as specified in [I-D.ietf-lisp] and includes an Authentication Data that contains the EID-AD, as received in the encapsulated Map-Request, as well as the LOC-AD.
The EID-AD is copied from the Authentication Data of the received encapsulated Map-Request.
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 [I-D.ietf-lisp].
The LISP-SEC threat model described in Section 3, assumes that the LISP Mapping System is working properly and eventually delivers Map-Request messages to a Map-Server that is authoritative for the requested EID.
Security is not yet embedded in LISP+ALT but BGP route filtering SHOULD be deployed in the ALT infrastructure to enforce proper routing in the mapping system. The SIDR working group is currently addressing prefix and route advertisement authorization and authentication for BGP. While following SIDR recommendations in the global Internet will take time, applying these recommendations to the ALT, which relies on BGP, should be less complex, as ALT is currently small and with a limited number of operators. Ultimately, deploying the SIDR recommendations in ALT further ensures that the fore mentioned assumption is true.
It is also assumed that no man-in-the-middle attack can be carried out against the ALT router to ALT router tunnels, and that the information included into the Map-Requests, in particular the OTK, cannot be read by third-party entities. It should be noted that the integrity of the Map-Request in the ALT is protected by BGP authentication, and that in order to provide OTK confidentiality in the ALT mapping system the ALT router to ALT router tunnels MAY be deployed using GRE+IPSec.
The OTK MUST be generated by a properly seeded pseudo-random (or strong random) source. See [RFC4086] for advice on generating security-sensitive random data
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:
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.
AUTH-HMAC-SHA-1-160 MUST be supported, AUTH-HMAC-SHA-256-128 should be supported.
The following OTK Encryption ID values are defined by this memo for use as OTK key wrap algorithms ID in the LISP-SEC Authentication Data:
Name Number Defined In ------------------------------------------------- NULL-KEY-WRAP-128 1 AES-KEY-WRAP-128 2 [RFC3394] values 0 and 3-65535 are reserved to IANA.
NULL-KEY-WRAP-128, and AES-KEY-WRAP-128 MUST be supported.
NULL-KEY-WRAP-128 is used to carry an unencrypted 128-bit OTK, with a 64-bit preamble set to 0x0000000000000000 (64 bits).
The following KDF ID values are defined by this memo for use as KDF ID in the LISP-SEC Authentication Data:
Name Number Defined In ------------------------------------------------- NONE 0 HKDF-SHA1-128 1 [RFC5869] values 2-65535 are reserved to IANA.
HKDF-SHA1-128 MUST be supported
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.