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Run idnits with the --verbose option for more detailed information about the items above. -------------------------------------------------------------------------------- 2 Network Working Group F. Maino 3 Internet-Draft V. Ermagan 4 Intended status: Experimental Cisco Systems 5 Expires: July 4, 2012 A. Cabellos 6 Technical University of 7 Catalonia 8 D. Saucez 9 O. Bonaventure 10 Universite catholique de Louvain 11 January 1, 2012 13 LISP-Security (LISP-SEC) 14 draft-ietf-lisp-sec-01.txt 16 Abstract 18 This memo specifies LISP-SEC, a set of security mechanisms that 19 provide origin authentication, integrity and anti-replay protection 20 to LISP's EID-to-RLOC mapping data conveyed via mapping lookup 21 process. LISP-SEC also enables verification of authorization on EID- 22 prefix claims in Map-Reply messages. 24 Requirements Language 26 The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT", 27 "SHOULD", "SHOULD NOT", "RECOMMENDED", "MAY", and "OPTIONAL" in this 28 document are to be interpreted as described in [RFC2119]. 30 Status of this Memo 32 This Internet-Draft is submitted in full conformance with the 33 provisions of BCP 78 and BCP 79. 35 Internet-Drafts are working documents of the Internet Engineering 36 Task Force (IETF). Note that other groups may also distribute 37 working documents as Internet-Drafts. The list of current Internet- 38 Drafts is at http://datatracker.ietf.org/drafts/current/. 40 Internet-Drafts are draft documents valid for a maximum of six months 41 and may be updated, replaced, or obsoleted by other documents at any 42 time. It is inappropriate to use Internet-Drafts as reference 43 material or to cite them other than as "work in progress." 45 This Internet-Draft will expire on July 4, 2012. 47 Copyright Notice 48 Copyright (c) 2012 IETF Trust and the persons identified as the 49 document authors. All rights reserved. 51 This document is subject to BCP 78 and the IETF Trust's Legal 52 Provisions Relating to IETF Documents 53 (http://trustee.ietf.org/license-info) in effect on the date of 54 publication of this document. Please review these documents 55 carefully, as they describe your rights and restrictions with respect 56 to this document. Code Components extracted from this document must 57 include Simplified BSD License text as described in Section 4.e of 58 the Trust Legal Provisions and are provided without warranty as 59 described in the Simplified BSD License. 61 Table of Contents 63 1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . . 3 64 2. Definition of Terms . . . . . . . . . . . . . . . . . . . . . 3 65 3. LISP-SEC Threat Model . . . . . . . . . . . . . . . . . . . . 4 66 4. Protocol Operations . . . . . . . . . . . . . . . . . . . . . 4 67 5. LISP-SEC Control Messages Details . . . . . . . . . . . . . . 7 68 5.1. Encapsulated Control Message LISP-SEC Extensions . . . . . 7 69 5.2. Map-Reply LISP-SEC Extensions . . . . . . . . . . . . . . 9 70 5.3. ITR Processing . . . . . . . . . . . . . . . . . . . . . . 10 71 5.3.1. Map-Reply Record Validation . . . . . . . . . . . . . 12 72 5.3.2. PITR Processing . . . . . . . . . . . . . . . . . . . 13 73 5.4. Encrypting and Decrypting an OTK . . . . . . . . . . . . . 13 74 5.5. Map-Resolver Processing . . . . . . . . . . . . . . . . . 14 75 5.6. Map-Server Processing . . . . . . . . . . . . . . . . . . 14 76 5.6.1. Map-Server Processing in Proxy mode . . . . . . . . . 15 77 5.7. ETR Processing . . . . . . . . . . . . . . . . . . . . . . 15 78 6. Security Considerations . . . . . . . . . . . . . . . . . . . 16 79 6.1. Mapping System Security . . . . . . . . . . . . . . . . . 16 80 6.2. Random Number Generation . . . . . . . . . . . . . . . . . 16 81 6.3. Map-Server and ETR Colocation . . . . . . . . . . . . . . 16 82 7. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 17 83 7.1. HMAC functions . . . . . . . . . . . . . . . . . . . . . . 17 84 7.2. Key Wrap Functions . . . . . . . . . . . . . . . . . . . . 17 85 7.3. Key Derivation Functions . . . . . . . . . . . . . . . . . 17 86 8. Acknowledgements . . . . . . . . . . . . . . . . . . . . . . . 18 87 9. Normative References . . . . . . . . . . . . . . . . . . . . . 18 88 Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . . 19 90 1. Introduction 92 The Locator/ID Separation Protocol [I-D.ietf-lisp] defines a set of 93 functions for routers to exchange information used to map from non- 94 routable Endpoint Identifiers (EIDs) to routable Routing Locators 95 (RLOCs). If these EID-to-RLOC mappings, carried through Map-Reply 96 messages, are transmitted without integrity protection, an adversary 97 can manipulate them and hijack the communication, impersonate the 98 requested EID or mount Denial of Service or Distributed Denial of 99 Service attacks. Also, if the Map-Reply message is transported 100 unauthenticated, an adversarial LISP entity can overclaim an EID- 101 prefix and maliciously redirect traffic directed to a large number of 102 hosts. A detailed description of "overclaiming" attack is provided 103 in [I-D.ietf-lisp-threats]. 105 This memo specifies LISP-SEC, a set of security mechanisms that 106 provide origin authentication, integrity and anti-replay protection 107 to LISP's EID-to-RLOC mapping data conveyed via mapping lookup 108 process. LISP-SEC also enables verification of authorization on EID- 109 prefix claims in Map-Reply messages, ensuring that the sender of a 110 Map-Reply that provides the location for a given EID-prefix is 111 entitled to do so according to the EID prefix registered in the 112 associated Map Server. Map-Register security, including the right 113 for a LISP entity to register an EID-prefix or to claim presence at 114 an RLOC, is out of the scope of LISP-SEC. Additional security 115 considerations are described in Section 6. 117 2. Definition of Terms 119 One-Time Key (OTK): An ephemeral randomly generated key that must 120 be used for a single Map-Request/Map-Reply exchange. 122 ITR-OTK: The One-Time Key generated at the ITR. 124 MS-OTK: The One-Time Key generated at the Map-Server. 126 Encapsulated Control Message (ECM): A LISP control message that is 127 prepended with an additional LISP header. ECM is used by ITRs to 128 send LISP control messages to a Map-Resolver, by Map-Resolvers to 129 forward LISP control messages to a Map-Server, and by Map- 130 Resolvers to forward LISP control messages to an ETR. 132 Authentication Data (AD): Metadata that is included either in a 133 LISP ECM header or in a Map-Reply message to support 134 confidentiality, integrity protection, and verification of EID- 135 prefix authorization. 137 OTK-AD: The portion of ECM Authentication Data that contains a 138 One-Time Key. 140 EID-AD: The portion of ECM and Map-Reply Authentication Data 141 used for verification of EID-prefix authorization. 143 PKT-AD: The portion of Map-Reply Authentication Data used to 144 protect the integrity of the Map-Reply message. 146 For definitions of other terms, notably Map-Request, Map-Reply, 147 Ingress Tunnel Router (ITR), Egress Tunnel Router (ETR), Map-Server 148 (MS) and Map-Resolver (MR) please consult the LISP specification 149 [I-D.ietf-lisp]. 151 3. LISP-SEC Threat Model 153 LISP-SEC addresses the control plane threats, described in 154 [I-D.ietf-lisp-threats], that target EID-to-RLOC mappings, including 155 manipulations of Map-Request and Map-Reply messages, and malicious 156 xTR EID overclaiming. However LISP-SEC makes two main assumptions 157 that are not part of [I-D.ietf-lisp-threats]. First, the LISP 158 Mapping System is expected to deliver Map-Request messages to their 159 intended destinations as identified by the EID. Second, no man-in- 160 the-middle attack can be mounted within the LISP Mapping System. 161 Furthermore, while LISP-SEC enables detection of EID prefix over 162 claiming attacks, it assumes that Map Servers can verify the EID 163 prefix authorization at time of registration. 165 Accordingly to the threat model described in [I-D.ietf-lisp-threats] 166 LISP-SEC assumes that any kind of attack, including MITM attacks, can 167 be mounted in the access network, outside of the boundaries of the 168 LISP mapping system. An on-path attacker, outside of the LISP 169 mapping service system can, for instance, hijack mapping requests and 170 replies, spoofing the identity of a LISP node. Another example of 171 on-path attack, called over claiming attack, can be mounted by a 172 malicious Egress Tunnel Router (ETR), by over claiming the EID- 173 prefixes for which it is authoritative. In this way the ETR can 174 maliciously redirect traffic directed to a large number of hosts. 176 4. Protocol Operations 178 The goal of the security mechanisms defined in [I-D.ietf-lisp] is to 179 prevent unauthorized insertion of mapping data, by providing origin 180 authentication and integrity protection for the Map-Registration, and 181 by using the nonce to detect unsolicited Map-Reply sent by off-path 182 attackers. 184 LISP-SEC builds on top of the security mechanisms defined in 185 [I-D.ietf-lisp] to address the threats described in Section 3 by 186 leveraging the trust relationships existing among the LISP entities 187 participating to the exchange of the Map-Request/Map-Reply messages. 188 Those trust relationships are used to securely distribute a One-Time 189 Key (OTK) that provides origin authentication, integrity and anti- 190 replay protection to mapping data conveyed via the mapping lookup 191 process, and that effectively prevent over claiming attacks. The 192 processing of security parameters during the Map-Request/Map-Reply 193 exchange is as follows: 195 o The ITR-OTK is generated and stored at the ITR, and securely 196 transported to the Map-Server. 198 o The Map-Server uses the ITR-OTK to compute an HMAC that protects 199 the integrity of the mapping data provided by the Map-Server to 200 prevent overclaiming attacks. The Map-Server also derives a new 201 OTK (MS-OTK) that is passed to the ETR, by applying a Key 202 Derivation Function (KDF) to the ITR-OTK. 204 o The ETR uses the MS-OTK to compute an HMAC that protects the 205 integrity of the Map-Reply sent to the ITR. 207 o Finally, the ITR uses the stored ITR-OTK to verify the integrity 208 of the mapping data provided by both the Map-Server and the ETR, 209 and to verify that no overclaiming attacks were mounted along the 210 path between the Map-Server and the ITR. 212 Section 5 provides the detailed description of the LISP-SEC control 213 messages and their processing, while the rest of this section 214 describes the flow of protocol operations at each entity involved in 215 the Map-Request/Map-Reply exchange: 217 o The ITR, upon transmitting a Map-Request message, generates and 218 stores an OTK (ITR-OTK). This key is included into the 219 Encapsulated Control Message (ECM) that contains the Map-Request 220 sent to the Map-Resolver. To provide confidentiality to the ITR- 221 OTK over the path between the ITR and its Map-Resolver, the ITR- 222 OTK SHOULD be encrypted using a preconfigured key shared between 223 the ITR and the Map-Resolver, similar to the key shared between 224 the ETR and the Map-Server in order to secure ETR registration 225 [I-D.ietf-lisp-ms]. 227 o The Map-Resolver decapsulates the ECM message, decrypts the ITR- 228 OTK, if needed, and forwards through the Mapping System the 229 received Map-Request and the ITR-OTK, as part of a new ECM 230 message. As described in Section 5.5, the LISP Mapping System 231 delivers the ECM to the appropriate Map-Server, as identified by 232 the EID destination address of the Map-Request. 234 o The Map-Server is configured with the location mappings and policy 235 information for the ETR responsible for the destination EID 236 address. Using this preconfigured information the Map-Server, 237 after the decapsulation of the ECM message, finds the longest 238 match EID-prefix that covers the requested EID in the received 239 Map-Request. The Map-Server adds this EID-prefix, together with 240 an HMAC computed using the ITR-OTK, to a new Encapsulated Control 241 Message that contains the received Map-Request. 243 o The Map-Server derives a new OTK (MS-OTK) by applying a Key 244 Derivation Function (KDF) to the ITR-OTK. MS-OTK is included in 245 the Encapsulated Control Message sent to the ETR. To provide MS- 246 OTK confidentiality over the path between the Map-Server and the 247 ETR, the MS-OTK should be encrypted using the key shared between 248 the ETR and the Map-Server in order to secure ETR registration 249 [I-D.ietf-lisp-ms]. 251 o If the Map-Server is acting in proxy mode, as specified in 252 [I-D.ietf-lisp], the ETR is not involved in the generation of the 253 Map-Reply. In this case the Map-Server generates the Map-Reply on 254 behalf of the ETR as described below. 256 o The ETR, upon receiving the Encapsulated Map-Request from the Map- 257 Server, decrypts the MS-OTK, if needed, and originates a Map-Reply 258 that contains the EID-to-RLOC mapping information as specified in 259 [I-D.ietf-lisp]. 261 o The ETR computes an HMAC over the original LISP Map-Reply, keyed 262 with MS-OTK to protect the integrity of the whole Map-Reply. The 263 ETR also copies the EID-prefix authorization data that the Map- 264 Server included in the Encapsulated Map-Request into the Map-Reply 265 message. 267 o The ITR, upon receiving the Map-Reply, uses the locally stored 268 ITR-OTK to verify the integrity of the EID-prefix authorization 269 data included in the Map-Reply by the Map-Server. The ITR 270 computes the MS-OTK by applying the same KDF used by the Map- 271 Server, and verifies the integrity of the Map-Reply. If the 272 integrity checks fail, the Map-Reply MUST be discarded. Also, if 273 the EID-prefixes claimed by the ETR in the Map-Reply are not equal 274 or less specific than the EID-prefix authorization data inserted 275 by the Map-Server, the ITR MUST discard the Map-Reply. 277 5. LISP-SEC Control Messages Details 279 LISP-SEC metadata associated with a Map-Request is transported within 280 the Encapsulated Control Message that contains the Map-Request. 282 LISP-SEC metadata associated with the Map-Reply is transported within 283 the Map-Reply itself. 285 5.1. Encapsulated Control Message LISP-SEC Extensions 287 LISP-SEC uses the ECM (Encapsulated Control Message) defined in 288 [I-D.ietf-lisp] with Type set to 8, and S bit set to 1 to indicate 289 that the LISP header includes Authentication Data (AD). The format 290 of the LISP-SEC ECM Authentication Data is defined in the following 291 figure. OTK-AD stands for One-Time Key Authentication Data and 292 EID-AD stands for EID Authentication Data. 294 0 1 2 3 295 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 1 296 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 297 | AD Type |V| Reserved | Requested HMAC ID | 298 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+\ 299 | OTK Length | OTK Encryption ID | | 300 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | 301 | One-Time-Key Preamble ... | | 302 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ OTK-AD 303 | ... One-Time-Key Preamble | | 304 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | 305 ~ One-Time Key (128 bits) ~/ 306 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ <---+ 307 | EID-AD Length | KDF ID | | 308 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | 309 | Record Count | Reserved | EID HMAC ID | EID-AD 310 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+\ | 311 | Reserved | EID mask-len | EID-AFI | | | 312 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ Rec | 313 ~ EID-prefix ... ~ | | 314 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+/ | 315 ~ EID HMAC ~ | 316 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ <---+ 318 LISP-SEC ECM Authentication Data 320 AD Type: 1 (LISP-SEC Authentication Data) 322 V: Key Version bit. This bit is toggled when the sender switches 323 to a new OTK wrapping key 325 Reserved: Set to 0 on transmission and ignored on receipt. 327 Requested HMAC ID: The HMAC algorithm requested by the ITR. See 328 Section 5.3 for details. 330 OTK Length: The length (in bytes) of the OTK Authentication Data 331 (OTK-AD), that contains the OTK Preamble and the OTK. 333 OTK Encryption ID: The identifier of the key wrapping algorithm 334 used to encrypt the One-Time-Key. When a 128-bit OTK is sent 335 unencrypted by the Map-Resolver, the OTK Encryption ID is set to 336 NULL_KEY_WRAP_128. See Section 5.4 for more details. 338 One-Time-Key Preamble: set to 0 if the OTK is not encrypted. When 339 the OTK is encrypted, this field may carry additional metadata 340 resulting from the key wrapping operation. When a 128-bit OTK is 341 sent unencrypted by Map-Resolver, the OTK Preamble is set to 342 0x0000000000000000 (64 bits). See Section 5.4 for details. 344 One-Time-Key: the OTK encrypted (or not) as specified by OTK 345 Encryption ID. See Section 5.4 for details. 347 EID-AD Length: length (in bytes) of the EID Authentication Data 348 (EID-AD). The ITR MUST set EID-AD Length to 4 bytes, as it only 349 fills the KDF ID field, and all the remaining fields part of the 350 EID-AD are not present. An EID-AD MAY contain multiple EID- 351 records. Each EID-record is 4-byte long plus the length of the 352 AFI-encoded EID-prefix. 354 KDF ID: Identifier of the Key Derivation Function used to derive 355 the MS-OTK. The ITR SHOULD use this field to indicate the 356 recommended KDF algorithm, according to local policy. The Map- 357 Server can overwrite the KDF ID if it does not support the KDF ID 358 recommended by the ITR. See Section 5.4 for more details. 360 Record Count: The number of records in this Map-Request message. 361 A record is comprised of the portion of the packet that is labeled 362 'Rec' above and occurs the number of times equal to Record Count. 364 Reserved: Set to 0 on transmission and ignored on receipt. 366 EID HMAC ID: Identifier of the HMAC algorithm used to protect the 367 integrity of the EID-AD. This field is filled by Map-Server that 368 computed the EID-prefix HMAC. See Section 5.4 for more details. 370 EID mask-len: Mask length for EID-prefix. 372 EID-AFI: Address family of EID-prefix according to [RFC5226] 374 EID-prefix: The Map-Server uses this field to specify the EID- 375 prefix that the destination ETR is authoritative for, and is the 376 longest match for the requested EID. 378 EID HMAC: HMAC of the EID-AD computed and inserted by Map-Server. 379 Before computing the HMAC operation the EID HMAC field MUST be set 380 to 0. The HMAC covers the entire EID-AD. 382 5.2. Map-Reply LISP-SEC Extensions 384 LISP-SEC uses the Map-Reply defined in [I-D.ietf-lisp], with Type set 385 to 2, and S bit set to 1 to indicate that the Map-Reply message 386 includes Authentication Data (AD). The format of the LISP-SEC Map- 387 Reply Authentication Data is defined in the following figure. PKT-AD 388 is the Packet Authentication Data that covers the Map-Reply payload. 389 0 1 2 3 390 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 1 391 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 392 | AD Type | Reserved | 393 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ <---+ 394 | EID-AD Length | KDF ID | | 395 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | 396 | Record Count | Reserved | EID HMAC ID | EID-AD 397 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+\ | 398 | Reserved | EID mask-len | EID-AFI | | | 399 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ Rec | 400 ~ EID-prefix ... ~ | | 401 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+/ | 402 ~ EID HMAC ~ | 403 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ <---+ 404 | PKT-AD Length | PKT HMAC ID |\ 405 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | 406 ~ PKT HMAC ~ PKT-AD 407 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+/ 409 LISP-SEC Map-Reply Authentication Data 411 AD Type: 1 (LISP-SEC Authentication Data) 413 EID-AD Length: length (in bytes) of the EID-AD. An EID-AD MAY 414 contain multiple EID-records. Each EID-record is 4-byte long plus 415 the length of the AFI-encoded EID-prefix. 417 KDF ID: Identifier of the Key Derivation Function used to derive 418 MS-OTK. See Section 5.6 for more details. 420 Record Count: The number of records in this Map-Reply message. A 421 record is comprised of the portion of the packet that is labeled 422 'Rec' above and occurs the number of times equal to Record Count. 424 Reserved: Set to 0 on transmission and ignored on receipt. 426 EID HMAC ID: Identifier of the HMAC algorithm used to protect the 427 integrity of the EID-AD. See Section 5.6 for more details. 429 EID mask-len: Mask length for EID-prefix. 431 EID-AFI: Address family of EID-prefix according to [RFC5226]. 433 EID-prefix: This field contains an EID-prefix that the destination 434 ETR is authoritative for, and is the longest match for the 435 requested EID. 437 EID HMAC: HMAC of the EID-AD, as computed by the Map-Server. 438 Before computing the HMAC operation the EID HMAC field MUST be set 439 to 0. The HMAC covers the entire EID-AD. 441 PKT-AD Length: length (in bytes) of the Packet Authentication Data 442 (PKT-AD). 444 PKT HMAC ID: Identifier of the HMAC algorithm used to protect the 445 integrity of the Map-reply Location Data. 447 PKT HMAC: HMAC of the whole Map-Reply packet, including the LISP- 448 SEC Authentication Data. The scope of the authentication goes 449 from the Map-Reply Type field to the PKT HMAC field included. 450 Before computing the HMAC operation the PKT HMAC field MUST be set 451 to 0. See Section 5.7 for more details. 453 5.3. ITR Processing 455 Upon creating a Map-Request, the ITR generates a random ITR-OTK that 456 is stored locally, together with the nonce generated as specified in 457 [I-D.ietf-lisp]. 459 The Map-Request MUST be encapsulated in an ECM, with the S-bit set to 460 1, to indicate the presence of Authentication Data. If the ITR and 461 the Map-Resolver are configured with a shared key, the ITR-OTK 462 confidentiality SHOULD be protected by wrapping the ITR-OTK with the 463 algorithm specified by the OTK Encryption ID field. See Section 5.4 464 for further details on OTK encryption. 466 The Requested HMAC ID field contains the suggested HMAC algorithm to 467 be used by the Map-Server and the ETR to protect the integrity of the 468 ECM Authentication data and of the Map-Reply. 470 The KDF ID field, specifies the suggested key derivation function to 471 be used by the Map-Server to derive the MS-OTK. 473 The EID-AD length is set to 4 bytes, since the Authentication Data 474 does not contain EID-prefix Authentication Data, and the EID-AD 475 contains only the KDF ID field. 477 In response to an encapsulated Map-Request that has the S-bit set, an 478 ITR MUST receive a Map-Reply with the S-bit set, that includes an 479 EID-AD and a PKT-AD. If the Map-Reply does not include both ADs, the 480 ITR MUST discard it. In response to an encapsulated Map-Request with 481 S-bit set to 0, the ITR expects a Map-Reply with S-bit set to 0, and 482 the ITR SHOULD discard the Map-Reply if the S-bit is set. 484 Upon receiving a Map-Reply, the ITR must verify the integrity of both 485 the EID-AD and the PKT-AD, and MUST discard the Map-Reply if one of 486 the integrity checks fails. 488 The integrity of the EID-AD is verified using the locally stored ITR- 489 OTK to re-compute the HMAC of the EID-AD using the algorithm 490 specified in the EID HMAC ID field. If the EID HMAC ID field does 491 not match the Requested HMAC ID the ITR SHOULD discard the Map-Reply 492 and send, at the first opportunity it needs to, a new Map-Request 493 with a different Requested HMAC ID field, according to ITR's local 494 policy. The ITR MUST set the EID HMAC ID field to 0 before computing 495 the HMAC. 497 To verify the integrity of the PKT-AD, first the MS-OTK is derived 498 from the locally stored ITR-OTK using the algorithm specified in the 499 KDF ID field. This is because the PKT-AD is generated by the ETR 500 using the MS-OTK. If the KDF ID in the Map-Reply does not match the 501 KDF ID requested in the Map-Request, the ITR SHOULD discard the Map- 502 Reply and send, at the first opportunity it needs to, a new Map- 503 Request with a different KDF ID, according to ITR's local policy. 504 The derived MS-OTK is then used to re-compute the HMAC of the PKT-AD 505 using the Algorithm specified in the PKT HMAC ID field. If the PKT 506 HMAC ID field does not match the Requested HMAC ID the ITR SHOULD 507 discard the Map-Reply and send, at the first opportunity it needs to, 508 a new Map-Request with a different Requested HMAC ID according to 509 ITR's local policy. 511 Each individual Map-Reply EID-record is considered valid only if: (1) 512 both EID-AD and PKT-AD are valid, and (2) the intersection of the 513 EID-prefix in the Map-Reply EID-record with one of the EID-prefixes 514 contained in the EID-AD is not empty. After identifying the Map- 515 Reply record as valid, the ITR sets the EID-prefix in the Map-Reply 516 record to the value of the intersection set computed before, and adds 517 the Map-Reply EID-record to its EID-to-RLOC cache, as described in 518 [I-D.ietf-lisp]. An example of Map-Reply record validation is 519 provided in Section 5.3.1. 521 The ITR SHOULD send SMR triggered Map Requests over the mapping 522 system in order to receive a secure Map-Reply. If an ITR accepts 523 piggybacked Map-Replies, it SHOULD also send a Map-Request over the 524 mapping system in order to securely verify the piggybacked Map-Reply. 526 5.3.1. Map-Reply Record Validation 528 The payload of a Map-Reply may contain multiple EID-records. The 529 whole Map-Reply is signed by the ETR, with the PKT HMAC, to provide 530 integrity protection and origin authentication to the EID-prefix 531 records claimed by the ETR. The Authentication Data field of a Map- 532 Reply may contain multiple EID-records in the EID-AD. The EID-AD is 533 signed by the Map-Server, with the EID HMAC, to provide integrity 534 protection and origin authentication to the EID-prefix records 535 inserted by the Map-Server. 537 Upon receiving a Map-Reply with the S-bit set, the ITR first checks 538 the validity of both the EID HMAC and of the PKT-AD HMAC. If either 539 one of the HMACs is not valid, a log message is issued and the Map- 540 Reply is not processed any further. If both HMACs are valid, the ITR 541 proceeds with validating each individual EID-record claimed by the 542 ETR by computing the intersection of each one of the EID-prefix 543 contained in the payload of the Map-Reply with each one of the EID- 544 prefixes contained in the EID-AD. An EID-record is valid only if at 545 least one of the intersections is not the empty set. 547 For instance, the Map-Reply payload contains 3 mapping record EID- 548 prefixes: 550 1.1.1.0/24 552 1.1.2.0/24 554 1.2.0.0/16 556 The EID-AD contains two EID-prefixes: 558 1.1.2.0/24 560 1.2.3.0/24 562 The EID-record with EID-prefix 1.1.1.0/24 is not processed since it 563 is not included in any of the EID-ADs signed by the Map-Server. A 564 log message is issued. 566 The EID-record with EID-prefix 1.1.2.0/24 is stored in the map-cache 567 because it matches the second EID-prefix contained in the EID-AD. 569 The EID-record with EID-prefix 1.2.0.0/16 is not processed since it 570 is not included in any of the EID-ADs signed by the Map-Server. A 571 log message is issued. In this last example the ETR is trying to 572 over claim the EID-prefix 1.2.0.0/16, but the Map-Server authorized 573 only 1.2.3.0/24, hence the EID-record is discarded. 575 5.3.2. PITR Processing 577 The processing performed by a PITR is equivalent to the processing of 578 an ITR. However, if the PITR is directly connected to the ALT, the 579 PITR performs the functions of both the ITR and the Map-Resolver 580 forwarding the Map-Request encapsulated in an ECM header that 581 includes the Authentication Data fields as described in Section 5.5. 583 5.4. Encrypting and Decrypting an OTK 585 MS-OTK confidentiality is required in the path between the Map-Server 586 and the ETR, the MS-OTK SHOULD be encrypted using the preconfigured 587 key shared between the Map-Server and the ETR for the purpose of 588 securing ETR registration [I-D.ietf-lisp-ms]. Similarly, if ITR-OTK 589 confidentiality is required in the path between the ITR and the Map- 590 Resolver, the ITR-OTK SHOULD be encrypted with a key shared between 591 the ITR and the Map-Resolver. 593 The OTK is encrypted using the algorithm specified in the OTK 594 Encryption ID field. When the AES Key Wrap algorithm is used to 595 encrypt a 128-bit OTK, according to [RFC3339], the AES Key Wrap 596 Initialization Value MUST be set to 0xA6A6A6A6A6A6A6A6 (64 bits). 597 The output of the AES Key Wrap operation is 192-bit long. The most 598 significant 64-bit are copied in the One-Time Key Preamble field, 599 while the 128 less significant bits are copied in the One-Time Key 600 field of the LISP-SEC Authentication Data. 602 When decrypting an encrypted OTK the receiver MUST verify that the 603 Initialization Value resulting from the AES Key Wrap decryption 604 operation is equal to 0xA6A6A6A6A6A6A6A6. If this verification fails 605 the receiver MUST discard the entire message. 607 When a 128-bit OTK is sent unencrypted the OTK Encryption ID is set 608 to NULL_KEY_WRAP_128, and the OTK Preamble is set to 609 0x0000000000000000 (64 bits). 611 5.5. Map-Resolver Processing 613 Upon receiving an encapsulated Map-Request with the S-bit set, the 614 Map-Resolver decapsulates the ECM message. The ITR-OTK, if 615 encrypted, is decrypted as specified in Section 5.4. 617 The Map-Resolver, as specified in [I-D.ietf-lisp-ms], originates a 618 new ECM header with the S-bit set, that contains the unencrypted ITR- 619 OTK, as specified in Section 5.4, and the other data derived from the 620 ECM Authentication Data of the received encapsulated Map-Request. 622 The Map-Resolver then forwards the received Map-Request, encapsulated 623 in the new ECM header that includes the newly computed Authentication 624 Data fields. 626 5.6. Map-Server Processing 628 Upon receiving an ECM encapsulated Map-Request with the S-bit set, 629 the Map-Server process the Map-Request according to the value of the 630 S-bit contained in the Map-Register sent by the ETR during 631 registration. 633 If the S-bit contained in the Map-Register was clear the Map-Server 634 decapsulates the ECM and generates a new ECM encapsulated Map-Request 635 that does not contain an ECM Authentication Data, as specified in 636 [I-D.ietf-lisp]. The Map-Server does not perform any further LISP- 637 SEC processing. 639 If the S-bit contained in the Map-Register was set the Map-Server 640 decapsulates the ECM and generates a new ECM Authentication Data. 641 The Authentication Data includes the OTK-AD and the EID-AD, that 642 contains EID-prefix authorization information, that are ultimately 643 sent to the requesting ITR. 645 The Map-Server updates the OTK-AD by deriving a new OTK (MS-OTK) from 646 the ITR-OTK received with the Map-Request. MS-OTK is derived 647 applying the key derivation function specified in the KDF ID field. 648 If the algorithm specified in the KDF ID field is not supported, the 649 Map-Server uses a different algorithm to derive the key and updates 650 the KDF ID field accordingly. 652 The Map-Server and the ETR MUST be configured with a shared key for 653 mapping registration according to [I-D.ietf-lisp-ms]. If MS-OTK 654 confidentiality is required, then the MS-OTK SHOULD be encrypted, by 655 wrapping the MS-OTK with the algorithm specified by the OTK 656 Encryption ID field as specified in Section 5.4. 658 The Map-Server includes in the EID-AD the longest match registered 659 EID-prefix for the destination EID, and an HMAC of this EID-prefix. 660 The HMAC is keyed with the ITR-OTK contained in the received ECM 661 Authentication Data, and the HMAC algorithm is chosen according to 662 the Requested HMAC ID field. If The Map-Server does not support this 663 algorithm, the Map-Server uses a different algorithm and specifies it 664 in the EID HMAC ID field. The scope of the HMAC operation covers the 665 entire EID-AD, from the EID-AD Length field to the EID HMAC field, 666 which must be set to 0 before the computation. 668 The Map-Server then forwards the updated ECM encapsulated Map- 669 Request, that contains the OTK-AD, the EID-AD, and the received Map- 670 Request to an authoritative ETR as specified in [I-D.ietf-lisp]. 672 5.6.1. Map-Server Processing in Proxy mode 674 If the Map-Server is in proxy mode, it generates a Map-Reply, as 675 specified in [I-D.ietf-lisp], with the S-bit set to 1. The Map-Reply 676 includes the Authentication Data that contains the EID-AD, computed 677 as specified in Section 5.6, as well as the PKT-AD computed as 678 specified in Section 5.7. 680 5.7. ETR Processing 682 Upon receiving an encapsulated Map-Request with the S-bit set, the 683 ETR decapsulates the ECM message. The OTK field, if encrypted, is 684 decrypted as specified in Section 5.4 to obtain the unencrypted MS- 685 OTK. 687 The ETR then generates a Map-Reply as specified in [I-D.ietf-lisp] 688 and includes an Authentication Data that contains the EID-AD, as 689 received in the encapsulated Map-Request, as well as the PKT-AD. 691 The EID-AD is copied from the Authentication Data of the received 692 encapsulated Map-Request. 694 The PKT-AD contains the HMAC of the whole Map-Reply packet, keyed 695 with the MS-OTK and computed using the HMAC algorithm specified in 696 the Requested HMAC ID field of the received encapsulated Map-Request. 697 If the ETR does not support the Requested HMAC ID, it uses a 698 different algorithm and updates the PKT HMAC ID field accordingly. 699 The scope of the HMAC operation covers the entire PKT-AD, from the 700 Map-Reply Type field to the PKT HMAC field, which must be set to 0 701 before the computation. 703 Finally the ETR sends the Map-Reply to the requesting ITR as 704 specified in [I-D.ietf-lisp]. 706 6. Security Considerations 708 6.1. Mapping System Security 710 The LISP-SEC threat model described in Section 3, assumes that the 711 LISP Mapping System is working properly and eventually delivers Map- 712 Request messages to a Map-Server that is authoritative for the 713 requested EID. 715 Security is not yet embedded in LISP+ALT but BGP route filtering 716 SHOULD be deployed in the ALT infrastructure to enforce proper 717 routing in the mapping system. The SIDR working group is currently 718 addressing prefix and route advertisement authorization and 719 authentication for BGP. While following SIDR recommendations in the 720 global Internet will take time, applying these recommendations to the 721 ALT, which relies on BGP, should be less complex, as ALT is currently 722 small and with a limited number of operators. Ultimately, deploying 723 the SIDR recommendations in ALT further ensures that the fore 724 mentioned assumption is true. 726 It is also assumed that no man-in-the-middle attack can be carried 727 out against the ALT router to ALT router tunnels, and that the 728 information included into the Map-Requests, in particular the OTK, 729 cannot be read by third-party entities. It should be noted that the 730 integrity of the Map-Request in the ALT is protected by BGP 731 authentication, and that in order to provide OTK confidentiality in 732 the ALT mapping system the ALT router to ALT router tunnels MAY be 733 deployed using IPsec (ESP). 735 Map-Register security, including the right for a LISP entity to 736 register an EID-prefix or to claim presence at an RLOC, is out of the 737 scope of LISP-SEC. 739 6.2. Random Number Generation 741 The ITR-OTK MUST be generated by a properly seeded pseudo-random (or 742 strong random) source. See [RFC4086] for advice on generating 743 security-sensitive random data 745 6.3. Map-Server and ETR Colocation 747 If the Map-Server and the ETR are colocated, LISP-SEC does not 748 provide protection from overclaiming attacks mounted by the ETR. 749 However, in this particular case, since the ETR is within the trust 750 boundaries of the Map-Server, ETR's overclaiming attacks are not 751 included in the threat model. 753 7. IANA Considerations 755 7.1. HMAC functions 757 The following HMAC ID values are defined by this memo for use as 758 Requested HMAC ID, EID HMAC ID, and PKT HMAC ID in the LISP-SEC 759 Authentication Data: 761 Name Number Defined In 762 ------------------------------------------------- 763 NONE 0 764 AUTH-HMAC-SHA-1-96 1 [RFC2104] 765 AUTH-HMAC-SHA-256-128 2 [RFC4634] 767 values 2-65535 are reserved to IANA. 769 HMAC Functions 771 AUTH-HMAC-SHA-1-96 MUST be supported, AUTH-HMAC-SHA-256-128 should be 772 supported. 774 7.2. Key Wrap Functions 776 The following OTK Encryption ID values are defined by this memo for 777 use as OTK key wrap algorithms ID in the LISP-SEC Authentication 778 Data: 780 Name Number Defined In 781 ------------------------------------------------- 782 NULL-KEY-WRAP-128 1 783 AES-KEY-WRAP-128 2 [RFC3394] 785 values 0 and 3-65535 are reserved to IANA. 787 Key Wrap Functions 789 NULL-KEY-WRAP-128, and AES-KEY-WRAP-128 MUST be supported. 791 NULL-KEY-WRAP-128 is used to carry an unencrypted 128-bit OTK, with a 792 64-bit preamble set to 0x0000000000000000 (64 bits). 794 7.3. Key Derivation Functions 796 The following KDF ID values are defined by this memo for use as KDF 797 ID in the LISP-SEC Authentication Data: 799 Name Number Defined In 800 ------------------------------------------------- 801 NONE 0 802 HKDF-SHA1-128 1 [RFC5869] 804 values 2-65535 are reserved to IANA. 806 Key Derivation Functions 808 HKDF-SHA1-128 MUST be supported 810 8. Acknowledgements 812 The authors would like to acknowledge Pere Monclus, Dave Meyer, Dino 813 Farinacci, Brian Weis, David McGrew, Darrel Lewis and Landon Curt 814 Noll for their valuable suggestions provided during the preparation 815 of this document. 817 9. Normative References 819 [I-D.ietf-lisp] 820 Farinacci, D., Fuller, V., Meyer, D., and D. Lewis, 821 "Locator/ID Separation Protocol (LISP)", 822 draft-ietf-lisp-18 (work in progress), December 2011. 824 [I-D.ietf-lisp-interworking] 825 Lewis, D., Meyer, D., Farinacci, D., and V. Fuller, 826 "Interworking LISP with IPv4 and IPv6", 827 draft-ietf-lisp-interworking-02 (work in progress), 828 June 2011. 830 [I-D.ietf-lisp-ms] 831 Fuller, V. and D. Farinacci, "LISP Map Server Interface", 832 draft-ietf-lisp-ms-14 (work in progress), December 2011. 834 [I-D.ietf-lisp-threats] 835 Saucez, D., Iannone, L., and O. Bonaventure, "LISP Threats 836 Analysis", draft-ietf-lisp-threats-00 (work in progress), 837 July 2011. 839 [RFC2104] Krawczyk, H., Bellare, M., and R. Canetti, "HMAC: Keyed- 840 Hashing for Message Authentication", RFC 2104, 841 February 1997. 843 [RFC2119] Bradner, S., "Key words for use in RFCs to Indicate 844 Requirement Levels", BCP 14, RFC 2119, March 1997. 846 [RFC3394] Schaad, J. and R. Housley, "Advanced Encryption Standard 847 (AES) Key Wrap Algorithm", RFC 3394, September 2002. 849 [RFC4086] Eastlake, D., Schiller, J., and S. Crocker, "Randomness 850 Requirements for Security", BCP 106, RFC 4086, June 2005. 852 [RFC5226] Narten, T. and H. Alvestrand, "Guidelines for Writing an 853 IANA Considerations Section in RFCs", BCP 26, RFC 5226, 854 May 2008. 856 [RFC5869] Krawczyk, H. and P. Eronen, "HMAC-based Extract-and-Expand 857 Key Derivation Function (HKDF)", RFC 5869, May 2010. 859 Authors' Addresses 861 Fabio Maino 862 Cisco Systems 863 170 Tasman Drive 864 San Jose, California 95134 865 USA 867 Email: fmaino@cisco.com 869 Vina Ermagan 870 Cisco Systems 871 170 Tasman Drive 872 San Jose, California 95134 873 USA 875 Email: vermagan@cisco.com 877 Albert Cabellos 878 Technical University of Catalonia 879 c/ Jordi Girona s/n 880 Barcelona, 08034 881 Spain 883 Email: acabello@ac.upc.edu 884 Damien Saucez 885 Universite catholique de Louvain 886 Place St. Barbe 2 887 Louvain-la-Neuve, 888 Belgium 890 Email: damien.saucez@uclouvain.be 892 Olivier Bonaventure 893 Universite catholique de Louvain 894 Place St. Barbe 2 895 Louvain-la-Neuve, 896 Belgium 898 Email: olivier.bonaventure@uclouvain.be