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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: January 2, 2012 A. Cabellos 6 Technical University of 7 Catalonia 8 D. Saucez 9 O. Bonaventure 10 Universite catholique de Louvain 11 July 1, 2011 13 LISP-Security (LISP-SEC) 14 draft-ietf-lisp-sec-00.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 January 2, 2012. 47 Copyright Notice 48 Copyright (c) 2011 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 . . . . . . . . . . . . . . . . . . . . . 5 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.saucez-lisp-security]. 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.saucez-lisp-security], that target EID-to-RLOC mappings, 155 including manipulations of Map-Request and Map-Reply messages, and 156 malicious xTR EID overclaiming. However LISP-SEC makes two main 157 assumptions that are not part of [I-D.saucez-lisp-security]. First, 158 the LISP Mapping System is expected to deliver Map-Request messages 159 to their intended destinations as identified by the EID. Second, no 160 man-in-the-middle attack can be mounted within the LISP Mapping 161 System. Furthermore, while LISP-SEC enables detection of EID prefix 162 over 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 166 [I-D.saucez-lisp-security] LISP-SEC assumes that any kind of attack, 167 including MITM attacks, can be mounted in the access network, outside 168 of the boundaries of the LISP mapping system. An on-path attacker, 169 outside of the LISP mapping service system can, for instance, hijack 170 mapping requests and replies, spoofing the identity of a LISP node. 171 Another example of on-path attack, called over claiming attack, can 172 be mounted by a malicious Egress Tunnel Router (ETR), by over 173 claiming the EID-prefixes for which it is authoritative. In this way 174 the ETR can maliciously redirect traffic directed to a large number 175 of hosts. 177 4. Protocol Operations 179 The goal of the security mechanisms defined in [I-D.ietf-lisp] is to 180 prevent unauthorized insertion of mapping data, by providing origin 181 authentication and integrity protection for the Map-Registration, and 182 by using the nonce to detect unsolicited Map-Reply sent by off-path 183 attackers. 185 LISP-SEC builds on top of the security mechanisms defined in 186 [I-D.ietf-lisp] to address the threats described in Section 3 by 187 leveraging the trust relationships existing among the LISP entities 188 participating to the exchange of the Map-Request/Map-Reply messages. 189 Those trust relationships are used to securely distribute a One-Time 190 Key (OTK) that provides origin authentication, integrity and anti- 191 replay protection to mapping data conveyed via the mapping lookup 192 process, and that effectively prevent over claiming attacks. The 193 processing of security parameters during the Map-Request/Map-Reply 194 exchange is as follows: 196 o The ITR-OTK is generated and stored at the ITR, and securely 197 transported to the Map-Server. 199 o The Map-Server uses the ITR-OTK to compute an HMAC that protects 200 the integrity of the mapping data provided by the Map-Server to 201 prevent overclaiming attacks. The Map-Server also derives a new 202 OTK (MS-OTK) that is passed to the ETR, by applying a Key 203 Derivation Function (KDF) to the ITR-OTK. 205 o The ETR uses the MS-OTK to compute an HMAC that protects the 206 integrity of the Map-Reply sent to the ITR. 208 o Finally, the ITR uses the stored ITR-OTK to verify the integrity 209 of the mapping data provided by both the Map-Server and the ETR, 210 and to verify that no overclaiming attacks were mounted along the 211 path between the Map-Server and the ITR. 213 Section 5 provides the detailed description of the LISP-SEC control 214 messages and their processing, while the rest of this section 215 describes the flow of protocol operations at each entity involved in 216 the Map-Request/Map-Reply exchange: 218 o The ITR, upon transmitting a Map-Request message, generates and 219 stores an OTK (ITR-OTK). This key is included into the 220 Encapsulated Control Message (ECM) that contains the Map-Request 221 sent to the Map-Resolver. To provide confidentiality to the ITR- 222 OTK over the path between the ITR and its Map-Resolver, the ITR- 223 OTK SHOULD be encrypted using a preconfigured key shared between 224 the ITR and the Map-Resolver, similar to the key shared between 225 the ETR and the Map-Server in order to secure ETR registration 226 [I-D.ietf-lisp-ms]. 228 o The Map-Resolver decapsulates the ECM message, decrypts the ITR- 229 OTK, if needed, and forwards through the Mapping System the 230 received Map-Request and the ITR-OTK, as part of a new ECM 231 message. As described in Section 5.5, the LISP Mapping System 232 delivers the ECM to the appropriate Map-Server, as identified by 233 the EID destination address of the Map-Request. 235 o The Map-Server is configured with the location mappings and policy 236 information for the ETR responsible for the destination EID 237 address. Using this preconfigured information the Map-Server, 238 after the decapsulation of the ECM message, finds the longest 239 match EID-prefix that covers the requested EID in the received 240 Map-Request. The Map-Server adds this EID-prefix, together with 241 an HMAC computed using the ITR-OTK, to a new Encapsulated Control 242 Message that contains the received Map-Request. 244 o The Map-Server derives a new OTK (MS-OTK) by applying a Key 245 Derivation Function (KDF) to the ITR-OTK. MS-OTK is included in 246 the Encapsulated Control Message sent to the ETR. To provide MS- 247 OTK confidentiality over the path between the Map-Server and the 248 ETR, the MS-OTK should be encrypted using the key shared between 249 the ETR and the Map-Server in order to secure ETR registration 250 [I-D.ietf-lisp-ms]. 252 o If the Map-Server is acting in proxy mode, as specified in 253 [I-D.ietf-lisp], the ETR is not involved in the generation of the 254 Map-Reply. In this case the Map-Server generates the Map-Reply on 255 behalf of the ETR as described below. 257 o The ETR, upon receiving the Encapsulated Map-Request from the Map- 258 Server, decrypts the MS-OTK, if needed, and originates a Map-Reply 259 that contains the EID-to-RLOC mapping information as specified in 260 [I-D.ietf-lisp]. 262 o The ETR computes an HMAC over the original LISP Map-Reply, keyed 263 with MS-OTK to protect the integrity of the whole Map-Reply. The 264 ETR also copies the EID-prefix authorization data that the Map- 265 Server included in the Encapsulated Map-Request into the Map-Reply 266 message. 268 o The ITR, upon receiving the Map-Reply, uses the locally stored 269 ITR-OTK to verify the integrity of the EID-prefix authorization 270 data included in the Map-Reply by the Map-Server. The ITR 271 computes the MS-OTK by applying the same KDF used by the Map- 272 Server, and verifies the integrity of the Map-Reply. If the 273 integrity checks fail, the Map-Reply MUST be discarded. Also, if 274 the EID-prefixes claimed by the ETR in the Map-Reply are not equal 275 or less specific than the EID-prefix authorization data inserted 276 by the Map-Server, the ITR MUST discard the Map-Reply. 278 5. LISP-SEC Control Messages Details 280 LISP-SEC metadata associated with a Map-Request is transported within 281 the Encapsulated Control Message that contains the Map-Request. 283 LISP-SEC metadata associated with the Map-Reply is transported within 284 the Map-Reply itself. 286 5.1. Encapsulated Control Message LISP-SEC Extensions 288 LISP-SEC uses the ECM (Encapsulated Control Message) defined in 289 [I-D.ietf-lisp] with Type set to 8, and S bit set to 1 to indicate 290 that the LISP header includes Authentication Data (AD). The format 291 of the LISP-SEC ECM Authentication Data is defined in the following 292 figure. OTK-AD stands for One-Time Key Authentication Data and 293 EID-AD stands for EID Authentication Data. 295 0 1 2 3 296 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 1 297 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 298 | AD Type |V| Reserved | Requested HMAC ID | 299 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+\ 300 | OTK Length | OTK Encryption ID | | 301 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | 302 | One-Time-Key Preamble ... | | 303 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ OTK-AD 304 | ... One-Time-Key Preamble | | 305 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | 306 ~ One-Time Key (128 bits) ~/ 307 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ <---+ 308 | EID-AD Length | KDF ID | | 309 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | 310 | Record Count | Reserved | EID HMAC ID | EID-AD 311 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+\ | 312 | Reserved | EID mask-len | EID-AFI | | | 313 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ Rec | 314 ~ EID-prefix ... ~ | | 315 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+/ | 316 ~ EID HMAC ~ | 317 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ <---+ 319 LISP-SEC ECM Authentication Data 321 AD Type: 1 (LISP-SEC Authentication Data) 323 V: Key Version bit. This bit is toggled when the sender switches 324 to a new OTK wrapping key 326 Reserved: Set to 0 on transmission and ignored on receipt. 328 Requested HMAC ID: The HMAC algorithm requested by the ITR. See 329 Section 5.3 for details. 331 OTK Length: The length (in bytes) of the OTK Authentication Data 332 (OTK-AD), that contains the OTK Preamble and the OTK. 334 OTK Encryption ID: The identifier of the key wrapping algorithm 335 used to encrypt the One-Time-Key. When a 128-bit OTK is sent 336 unencrypted by the Map-Resolver, the OTK Encryption ID is set to 337 NULL_KEY_WRAP_128. See Section 5.4 for more details. 339 One-Time-Key Preamble: set to 0 if the OTK is not encrypted. When 340 the OTK is encrypted, this field may carry additional metadata 341 resulting from the key wrapping operation. When a 128-bit OTK is 342 sent unencrypted by Map-Resolver, the OTK Preamble is set to 343 0x0000000000000000 (64 bits). See Section 5.4 for details. 345 One-Time-Key: the OTK encrypted (or not) as specified by OTK 346 Encryption ID. See Section 5.4 for details. 348 EID-AD Length: length (in bytes) of the EID Authentication Data 349 (EID-AD). The ITR MUST set EID-AD Length to 4 bytes, as it only 350 fills the KDF ID field, and all the remaining fields part of the 351 EID-AD are not present. An EID-AD MAY contain multiple EID- 352 records. Each EID-record is 4-byte long plus the length of the 353 AFI-encoded EID-prefix. 355 KDF ID: Identifier of the Key Derivation Function used to derive 356 the MS-OTK. The ITR SHOULD use this field to indicate the 357 recommended KDF algorithm, according to local policy. The Map- 358 Server can overwrite the KDF ID if it does not support the KDF ID 359 recommended by the ITR. See Section 5.4 for more details. 361 Record Count: The number of records in this Map-Request message. 362 A record is comprised of the portion of the packet that is labeled 363 'Rec' above and occurs the number of times equal to Record Count. 365 Reserved: Set to 0 on transmission and ignored on receipt. 367 EID HMAC ID: Identifier of the HMAC algorithm used to protect the 368 integrity of the EID-AD. This field is filled by Map-Server that 369 computed the EID-prefix HMAC. See Section 5.4 for more details. 371 EID mask-len: Mask length for EID-prefix. 373 EID-AFI: Address family of EID-prefix according to [RFC5226] 375 EID-prefix: The Map-Server uses this field to specify the EID- 376 prefix that the destination ETR is authoritative for, and is the 377 longest match for the requested EID. 379 EID HMAC: HMAC of the EID-AD computed and inserted by Map-Server. 380 Before computing the HMAC operation the EID HMAC field MUST be set 381 to 0. The HMAC covers the entire EID-AD. 383 5.2. Map-Reply LISP-SEC Extensions 385 LISP-SEC uses the Map-Reply defined in [I-D.ietf-lisp], with Type set 386 to 2, and S bit set to 1 to indicate that the Map-Reply message 387 includes Authentication Data (AD). The format of the LISP-SEC Map- 388 Reply Authentication Data is defined in the following figure. PKT-AD 389 is the Packet Authentication Data that covers the Map-Reply payload. 390 0 1 2 3 391 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 1 392 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 393 | AD Type | Reserved | 394 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ <---+ 395 | EID-AD Length | KDF ID | | 396 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | 397 | Record Count | Reserved | EID HMAC ID | EID-AD 398 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+\ | 399 | Reserved | EID mask-len | EID-AFI | | | 400 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ Rec | 401 ~ EID-prefix ... ~ | | 402 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+/ | 403 ~ EID HMAC ~ | 404 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ <---+ 405 | PKT-AD Length | PKT HMAC ID |\ 406 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | 407 ~ PKT HMAC ~ PKT-AD 408 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+/ 410 LISP-SEC Map-Reply Authentication Data 412 AD Type: 1 (LISP-SEC Authentication Data) 414 EID-AD Length: length (in bytes) of the EID-AD. An EID-AD MAY 415 contain multiple EID-records. Each EID-record is 4-byte long plus 416 the length of the AFI-encoded EID-prefix. 418 KDF ID: Identifier of the Key Derivation Function used to derive 419 MS-OTK. See Section 5.6 for more details. 421 Record Count: The number of records in this Map-Reply message. A 422 record is comprised of the portion of the packet that is labeled 423 'Rec' above and occurs the number of times equal to Record Count. 425 Reserved: Set to 0 on transmission and ignored on receipt. 427 EID HMAC ID: Identifier of the HMAC algorithm used to protect the 428 integrity of the EID-AD. See Section 5.6 for more details. 430 EID mask-len: Mask length for EID-prefix. 432 EID-AFI: Address family of EID-prefix according to [RFC5226]. 434 EID-prefix: This field contains an EID-prefix that the destination 435 ETR is authoritative for, and is the longest match for the 436 requested EID. 438 EID HMAC: HMAC of the EID-AD, as computed by the Map-Server. 439 Before computing the HMAC operation the EID HMAC field MUST be set 440 to 0. The HMAC covers the entire EID-AD. 442 PKT-AD Length: length (in bytes) of the Packet Authentication Data 443 (PKT-AD). 445 PKT HMAC ID: Identifier of the HMAC algorithm used to protect the 446 integrity of the Map-reply Location Data. 448 PKT HMAC: HMAC of the whole Map-Reply packet, including the LISP- 449 SEC Authentication Data. The scope of the authentication goes 450 from the Map-Reply Type field to the PKT HMAC field included. 451 Before computing the HMAC operation the PKT HMAC field MUST be set 452 to 0. See Section 5.7 for more details. 454 5.3. ITR Processing 456 Upon creating a Map-Request, the ITR generates a random ITR-OTK that 457 is stored locally, together with the nonce generated as specified in 458 [I-D.ietf-lisp]. 460 The Map-Request MUST be encapsulated in an ECM, with the S-bit set to 461 1, to indicate the presence of Authentication Data. If the ITR and 462 the Map-Resolver are configured with a shared key, the ITR-OTK 463 confidentiality SHOULD be protected by wrapping the ITR-OTK with the 464 algorithm specified by the OTK Encryption ID field. See Section 5.4 465 for further details on OTK encryption. 467 The Requested HMAC ID field contains the suggested HMAC algorithm to 468 be used by the Map-Server and the ETR to protect the integrity of the 469 ECM Authentication data and of the Map-Reply. 471 The KDF ID field, specifies the suggested key derivation function to 472 be used by the Map-Server to derive the MS-OTK. 474 The EID-AD length is set to 4 bytes, since the Authentication Data 475 does not contain EID-prefix Authentication Data, and the EID-AD 476 contains only the KDF ID field. 478 In response to an encapsulated Map-Request that has the S-bit set, an 479 ITR MUST receive a Map-Reply with the S-bit set, that includes an 480 EID-AD and a PKT-AD. If the Map-Reply does not include both ADs, the 481 ITR MUST discard it. In response to an encapsulated Map-Request with 482 S-bit set to 0, the ITR expects a Map-Reply with S-bit set to 0, and 483 the ITR SHOULD discard the Map-Reply if the S-bit is set. 485 Upon receiving a Map-Reply, the ITR must verify the integrity of both 486 the EID-AD and the PKT-AD, and MUST discard the Map-Reply if one of 487 the integrity checks fails. 489 The integrity of the EID-AD is verified using the locally stored ITR- 490 OTK to re-compute the HMAC of the EID-AD using the algorithm 491 specified in the EID HMAC ID field. If the EID HMAC ID field does 492 not match the Requested HMAC ID the ITR SHOULD discard the Map-Reply 493 and send, at the first opportunity it needs to, a new Map-Request 494 with a different Requested HMAC ID field, according to ITR's local 495 policy. The ITR MUST set the EID HMAC ID field to 0 before computing 496 the HMAC. 498 To verify the integrity of the PKT-AD, first the MS-OTK is derived 499 from the locally stored ITR-OTK using the algorithm specified in the 500 KDF ID field. This is because the PKT-AD is generated by the ETR 501 using the MS-OTK. If the KDF ID in the Map-Reply does not match the 502 KDF ID requested in the Map-Request, the ITR SHOULD discard the Map- 503 Reply and send, at the first opportunity it needs to, a new Map- 504 Request with a different KDF ID, according to ITR's local policy. 505 The derived MS-OTK is then used to re-compute the HMAC of the PKT-AD 506 using the Algorithm specified in the PKT HMAC ID field. If the PKT 507 HMAC ID field does not match the Requested HMAC ID the ITR SHOULD 508 discard the Map-Reply and send, at the first opportunity it needs to, 509 a new Map-Request with a different Requested HMAC ID according to 510 ITR's local policy. 512 Each individual Map-Reply EID-record is considered valid only if: (1) 513 both EID-AD and PKT-AD are valid, and (2) the intersection of the 514 EID-prefix in the Map-Reply EID-record with one of the EID-prefixes 515 contained in the EID-AD is not empty. After identifying the Map- 516 Reply record as valid, the ITR sets the EID-prefix in the Map-Reply 517 record to the value of the intersection set computed before, and adds 518 the Map-Reply EID-record to its EID-to-RLOC cache, as described in 519 [I-D.ietf-lisp]. An example of Map-Reply record validation is 520 provided in Section 5.3.1. 522 The ITR SHOULD send SMR triggered Map Requests over the mapping 523 system in order to receive a secure Map-Reply. If an ITR accepts 524 piggybacked Map-Replies, it SHOULD also send a Map-Request over the 525 mapping system in order to securely verify the piggybacked Map-Reply. 527 5.3.1. Map-Reply Record Validation 529 The payload of a Map-Reply may contain multiple EID-records. The 530 whole Map-Reply is signed by the ETR, with the PKT HMAC, to provide 531 integrity protection and origin authentication to the EID-prefix 532 records claimed by the ETR. The Authentication Data field of a Map- 533 Reply may contain multiple EID-records in the EID-AD. The EID-AD is 534 signed by the Map-Server, with the EID HMAC, to provide integrity 535 protection and origin authentication to the EID-prefix records 536 inserted by the Map-Server. 538 Upon receiving a Map-Reply with the S-bit set, the ITR first checks 539 the validity of both the EID HMAC and of the PKT-AD HMAC. If either 540 one of the HMACs is not valid, a log message is issued and the Map- 541 Reply is not processed any further. If both HMACs are valid, the ITR 542 proceeds with validating each individual EID-record claimed by the 543 ETR by computing the intersection of each one of the EID-prefix 544 contained in the payload of the Map-Reply with each one of the EID- 545 prefixes contained in the EID-AD. An EID-record is valid only if at 546 least one of the intersections is not the empty set. 548 For instance, the Map-Reply payload contains 3 mapping record EID- 549 prefixes: 551 1.1.1.0/24 553 1.1.2.0/24 555 1.2.0.0/16 557 The EID-AD contains two EID-prefixes: 559 1.1.2.0/24 561 1.2.3.0/24 563 The EID-record with EID-prefix 1.1.1.0/24 is not processed since it 564 is not included in any of the EID-ADs signed by the Map-Server. A 565 log message is issued. 567 The EID-record with EID-prefix 1.1.2.0/24 is stored in the map-cache 568 because it matches the second EID-prefix contained in the EID-AD. 570 The EID-record with EID-prefix 1.2.0.0/16 is not processed since it 571 is not included in any of the EID-ADs signed by the Map-Server. A 572 log message is issued. In this last example the ETR is trying to 573 over claim the EID-prefix 1.2.0.0/16, but the Map-Server authorized 574 only 1.2.3.0/24, hence the EID-record is discarded. 576 5.3.2. PITR Processing 578 The processing performed by a PITR is equivalent to the processing of 579 an ITR. However, if the PITR is directly connected to the ALT, the 580 PITR performs the functions of both the ITR and the Map-Resolver 581 forwarding the Map-Request encapsulated in an ECM header that 582 includes the Authentication Data fields as described in Section 5.5. 584 5.4. Encrypting and Decrypting an OTK 586 MS-OTK confidentiality is required in the path between the Map-Server 587 and the ETR, the MS-OTK SHOULD be encrypted using the preconfigured 588 key shared between the Map-Server and the ETR for the purpose of 589 securing ETR registration [I-D.ietf-lisp-ms]. Similarly, if ITR-OTK 590 confidentiality is required in the path between the ITR and the Map- 591 Resolver, the ITR-OTK SHOULD be encrypted with a key shared between 592 the ITR and the Map-Resolver. 594 The OTK is encrypted using the algorithm specified in the OTK 595 Encryption ID field. When the AES Key Wrap algorithm is used to 596 encrypt a 128-bit OTK, according to [RFC3339], the AES Key Wrap 597 Initialization Value MUST be set to 0xA6A6A6A6A6A6A6A6 (64 bits). 598 The output of the AES Key Wrap operation is 192-bit long. The most 599 significant 64-bit are copied in the One-Time Key Preamble field, 600 while the 128 less significant bits are copied in the One-Time Key 601 field of the LISP-SEC Authentication Data. 603 When decrypting an encrypted OTK the receiver MUST verify that the 604 Initialization Value resulting from the AES Key Wrap decryption 605 operation is equal to 0xA6A6A6A6A6A6A6A6. If this verification fails 606 the receiver MUST discard the entire message. 608 When a 128-bit OTK is sent unencrypted the OTK Encryption ID is set 609 to NULL_KEY_WRAP_128, and the OTK Preamble is set to 610 0x0000000000000000 (64 bits). 612 5.5. Map-Resolver Processing 614 Upon receiving an encapsulated Map-Request with the S-bit set, the 615 Map-Resolver decapsulates the ECM message. The ITR-OTK, if 616 encrypted, is decrypted as specified in Section 5.4. 618 The Map-Resolver, as specified in [I-D.ietf-lisp-ms], originates a 619 new ECM header with the S-bit set, that contains the unencrypted ITR- 620 OTK, as specified in Section 5.4, and the other data derived from the 621 ECM Authentication Data of the received encapsulated Map-Request. 623 The Map-Resolver then forwards the received Map-Request, encapsulated 624 in the new ECM header that includes the newly computed Authentication 625 Data fields. 627 5.6. Map-Server Processing 629 Upon receiving an ECM encapsulated Map-Request with the S-bit set, 630 the Map-Server process the Map-Request according to the value of the 631 S-bit contained in the Map-Register sent by the ETR during 632 registration. 634 If the S-bit contained in the Map-Register was clear the Map-Server 635 decapsulates the ECM and generates a new ECM encapsulated Map-Request 636 that does not contain an ECM Authentication Data, as specified in 637 [I-D.ietf-lisp]. The Map-Server does not perform any further LISP- 638 SEC processing. 640 If the S-bit contained in the Map-Register was set the Map-Server 641 decapsulates the ECM and generates a new ECM Authentication Data. 642 The Authentication Data includes the OTK-AD and the EID-AD, that 643 contains EID-prefix authorization information, that are ultimately 644 sent to the requesting ITR. 646 The Map-Server updates the OTK-AD by deriving a new OTK (MS-OTK) from 647 the ITR-OTK received with the Map-Request. MS-OTK is derived 648 applying the key derivation function specified in the KDF ID field. 649 If the algorithm specified in the KDF ID field is not supported, the 650 Map-Server uses a different algorithm to derive the key and updates 651 the KDF ID field accordingly. 653 The Map-Server and the ETR MUST be configured with a shared key for 654 mapping registration according to [I-D.ietf-lisp-ms]. If MS-OTK 655 confidentiality is required, then the MS-OTK SHOULD be encrypted, by 656 wrapping the MS-OTK with the algorithm specified by the OTK 657 Encryption ID field as specified in Section 5.4. 659 The Map-Server includes in the EID-AD the longest match registered 660 EID-prefix for the destination EID, and an HMAC of this EID-prefix. 661 The HMAC is keyed with the ITR-OTK contained in the received ECM 662 Authentication Data, and the HMAC algorithm is chosen according to 663 the Requested HMAC ID field. If The Map-Server does not support this 664 algorithm, the Map-Server uses a different algorithm and specifies it 665 in the EID HMAC ID field. The scope of the HMAC operation covers the 666 entire EID-AD, from the EID-AD Length field to the EID HMAC field, 667 which must be set to 0 before the computation. 669 The Map-Server then forwards the updated ECM encapsulated Map- 670 Request, that contains the OTK-AD, the EID-AD, and the received Map- 671 Request to an authoritative ETR as specified in [I-D.ietf-lisp]. 673 5.6.1. Map-Server Processing in Proxy mode 675 If the Map-Server is in proxy mode, it generates a Map-Reply, as 676 specified in [I-D.ietf-lisp], with the S-bit set to 1. The Map-Reply 677 includes the Authentication Data that contains the EID-AD, computed 678 as specified in Section 5.6, as well as the PKT-AD computed as 679 specified in Section 5.7. 681 5.7. ETR Processing 683 Upon receiving an encapsulated Map-Request with the S-bit set, the 684 ETR decapsulates the ECM message. The OTK field, if encrypted, is 685 decrypted as specified in Section 5.4 to obtain the unencrypted MS- 686 OTK. 688 The ETR then generates a Map-Reply as specified in [I-D.ietf-lisp] 689 and includes an Authentication Data that contains the EID-AD, as 690 received in the encapsulated Map-Request, as well as the PKT-AD. 692 The EID-AD is copied from the Authentication Data of the received 693 encapsulated Map-Request. 695 The PKT-AD contains the HMAC of the whole Map-Reply packet, keyed 696 with the MS-OTK and computed using the HMAC algorithm specified in 697 the Requested HMAC ID field of the received encapsulated Map-Request. 698 If the ETR does not support the Requested HMAC ID, it uses a 699 different algorithm and updates the PKT HMAC ID field accordingly. 700 The scope of the HMAC operation covers the entire PKT-AD, from the 701 Map-Reply Type field to the PKT HMAC field, which must be set to 0 702 before the computation. 704 Finally the ETR sends the Map-Reply to the requesting ITR as 705 specified in [I-D.ietf-lisp]. 707 6. Security Considerations 709 6.1. Mapping System Security 711 The LISP-SEC threat model described in Section 3, assumes that the 712 LISP Mapping System is working properly and eventually delivers Map- 713 Request messages to a Map-Server that is authoritative for the 714 requested EID. 716 Security is not yet embedded in LISP+ALT but BGP route filtering 717 SHOULD be deployed in the ALT infrastructure to enforce proper 718 routing in the mapping system. The SIDR working group is currently 719 addressing prefix and route advertisement authorization and 720 authentication for BGP. While following SIDR recommendations in the 721 global Internet will take time, applying these recommendations to the 722 ALT, which relies on BGP, should be less complex, as ALT is currently 723 small and with a limited number of operators. Ultimately, deploying 724 the SIDR recommendations in ALT further ensures that the fore 725 mentioned assumption is true. 727 It is also assumed that no man-in-the-middle attack can be carried 728 out against the ALT router to ALT router tunnels, and that the 729 information included into the Map-Requests, in particular the OTK, 730 cannot be read by third-party entities. It should be noted that the 731 integrity of the Map-Request in the ALT is protected by BGP 732 authentication, and that in order to provide OTK confidentiality in 733 the ALT mapping system the ALT router to ALT router tunnels MAY be 734 deployed using IPsec (ESP). 736 Map-Register security, including the right for a LISP entity to 737 register an EID-prefix or to claim presence at an RLOC, is out of the 738 scope of LISP-SEC. 740 6.2. Random Number Generation 742 The ITR-OTK MUST be generated by a properly seeded pseudo-random (or 743 strong random) source. See [RFC4086] for advice on generating 744 security-sensitive random data 746 6.3. Map-Server and ETR Colocation 748 If the Map-Server and the ETR are colocated, LISP-SEC does not 749 provide protection from overclaiming attacks mounted by the ETR. 750 However, in this particular case, since the ETR is within the trust 751 boundaries of the Map-Server, ETR's overclaiming attacks are not 752 included in the threat model. 754 7. IANA Considerations 756 7.1. HMAC functions 758 The following HMAC ID values are defined by this memo for use as 759 Requested HMAC ID, EID HMAC ID, and PKT HMAC ID in the LISP-SEC 760 Authentication Data: 762 Name Number Defined In 763 ------------------------------------------------- 764 NONE 0 765 AUTH-HMAC-SHA-1-160 1 [RFC2104] 766 AUTH-HMAC-SHA-256-128 2 [RFC4634] 768 values 2-65535 are reserved to IANA. 770 HMAC Functions 772 AUTH-HMAC-SHA-1-160 MUST be supported, AUTH-HMAC-SHA-256-128 should 773 be supported. 775 7.2. Key Wrap Functions 777 The following OTK Encryption ID values are defined by this memo for 778 use as OTK key wrap algorithms ID in the LISP-SEC Authentication 779 Data: 781 Name Number Defined In 782 ------------------------------------------------- 783 NULL-KEY-WRAP-128 1 784 AES-KEY-WRAP-128 2 [RFC3394] 786 values 0 and 3-65535 are reserved to IANA. 788 Key Wrap Functions 790 NULL-KEY-WRAP-128, and AES-KEY-WRAP-128 MUST be supported. 792 NULL-KEY-WRAP-128 is used to carry an unencrypted 128-bit OTK, with a 793 64-bit preamble set to 0x0000000000000000 (64 bits). 795 7.3. Key Derivation Functions 797 The following KDF ID values are defined by this memo for use as KDF 798 ID in the LISP-SEC Authentication Data: 800 Name Number Defined In 801 ------------------------------------------------- 802 NONE 0 803 HKDF-SHA1-128 1 [RFC5869] 805 values 2-65535 are reserved to IANA. 807 Key Derivation Functions 809 HKDF-SHA1-128 MUST be supported 811 8. Acknowledgements 813 The authors would like to acknowledge Pere Monclus, Dave Meyer, Dino 814 Farinacci, Brian Weis, David McGrew, Darrel Lewis and Landon Curt 815 Noll for their valuable suggestions provided during the preparation 816 of this document. 818 9. Normative References 820 [I-D.ietf-lisp] 821 Farinacci, D., Fuller, V., Meyer, D., and D. Lewis, 822 "Locator/ID Separation Protocol (LISP)", 823 draft-ietf-lisp-14 (work in progress), June 2011. 825 [I-D.ietf-lisp-interworking] 826 Lewis, D., Meyer, D., Farinacci, D., and V. Fuller, 827 "Interworking LISP with IPv4 and IPv6", 828 draft-ietf-lisp-interworking-01 (work in progress), 829 August 2010. 831 [I-D.ietf-lisp-ms] 832 Fuller, V. and D. Farinacci, "LISP Map Server", 833 draft-ietf-lisp-ms-09 (work in progress), June 2011. 835 [I-D.saucez-lisp-security] 836 Saucez, D., Iannone, L., and O. Bonaventure, "LISP 837 Security Threats", draft-saucez-lisp-security-03 (work in 838 progress), March 2011. 840 [RFC2104] Krawczyk, H., Bellare, M., and R. Canetti, "HMAC: Keyed- 841 Hashing for Message Authentication", RFC 2104, 842 February 1997. 844 [RFC2119] Bradner, S., "Key words for use in RFCs to Indicate 845 Requirement Levels", BCP 14, RFC 2119, March 1997. 847 [RFC3394] Schaad, J. and R. Housley, "Advanced Encryption Standard 848 (AES) Key Wrap Algorithm", RFC 3394, September 2002. 850 [RFC4086] Eastlake, D., Schiller, J., and S. Crocker, "Randomness 851 Requirements for Security", BCP 106, RFC 4086, June 2005. 853 [RFC5226] Narten, T. and H. Alvestrand, "Guidelines for Writing an 854 IANA Considerations Section in RFCs", BCP 26, RFC 5226, 855 May 2008. 857 [RFC5869] Krawczyk, H. and P. Eronen, "HMAC-based Extract-and-Expand 858 Key Derivation Function (HKDF)", RFC 5869, May 2010. 860 Authors' Addresses 862 Fabio Maino 863 Cisco Systems 864 170 Tasman Drive 865 San Jose, California 95134 866 USA 868 Email: fmaino@cisco.com 870 Vina Ermagan 871 Cisco Systems 872 170 Tasman Drive 873 San Jose, California 95134 874 USA 876 Email: vermagan@cisco.com 878 Albert Cabellos 879 Technical University of Catalonia 880 c/ Jordi Girona s/n 881 Barcelona, 08034 882 Spain 884 Email: acabello@ac.upc.edu 885 Damien Saucez 886 Universite catholique de Louvain 887 Place St. Barbe 2 888 Louvain-la-Neuve, 889 Belgium 891 Email: damien.saucez@uclouvain.be 893 Olivier Bonaventure 894 Universite catholique de Louvain 895 Place St. Barbe 2 896 Louvain-la-Neuve, 897 Belgium 899 Email: olivier.bonaventure@uclouvain.be