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Checking references for intended status: Experimental ---------------------------------------------------------------------------- == Missing Reference: 'RFC3339' is mentioned on line 605, but not defined == Missing Reference: 'RFC4634' is mentioned on line 775, but not defined ** Obsolete undefined reference: RFC 4634 (Obsoleted by RFC 6234) == Unused Reference: 'I-D.ietf-lisp-interworking' is defined on line 834, but no explicit reference was found in the text == Outdated reference: A later version (-24) exists of draft-ietf-lisp-23 == Outdated reference: A later version (-15) exists of draft-ietf-lisp-threats-02 ** Obsolete normative reference: RFC 5226 (Obsoleted by RFC 8126) Summary: 3 errors (**), 0 flaws (~~), 7 warnings (==), 1 comment (--). 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: April 15, 2013 A. Cabellos 6 Technical University of 7 Catalonia 8 D. Saucez 9 INRIA 10 O. Bonaventure 11 Universite Catholique de Louvain 12 October 12, 2012 14 LISP-Security (LISP-SEC) 15 draft-ietf-lisp-sec-04 17 Abstract 19 This memo specifies LISP-SEC, a set of security mechanisms that 20 provide origin authentication, integrity and anti-replay protection 21 to LISP's EID-to-RLOC mapping data conveyed via mapping lookup 22 process. LISP-SEC also enables verification of authorization on EID- 23 prefix claims in Map-Reply messages. 25 Requirements Language 27 The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT", 28 "SHOULD", "SHOULD NOT", "RECOMMENDED", "MAY", and "OPTIONAL" in this 29 document are to be interpreted as described in [RFC2119]. 31 Status of this Memo 33 This Internet-Draft is submitted in full conformance with the 34 provisions of BCP 78 and BCP 79. 36 Internet-Drafts are working documents of the Internet Engineering 37 Task Force (IETF). Note that other groups may also distribute 38 working documents as Internet-Drafts. The list of current Internet- 39 Drafts is at http://datatracker.ietf.org/drafts/current/. 41 Internet-Drafts are draft documents valid for a maximum of six months 42 and may be updated, replaced, or obsoleted by other documents at any 43 time. It is inappropriate to use Internet-Drafts as reference 44 material or to cite them other than as "work in progress." 46 This Internet-Draft will expire on April 15, 2013. 48 Copyright Notice 49 Copyright (c) 2012 IETF Trust and the persons identified as the 50 document authors. All rights reserved. 52 This document is subject to BCP 78 and the IETF Trust's Legal 53 Provisions Relating to IETF Documents 54 (http://trustee.ietf.org/license-info) in effect on the date of 55 publication of this document. Please review these documents 56 carefully, as they describe your rights and restrictions with respect 57 to this document. Code Components extracted from this document must 58 include Simplified BSD License text as described in Section 4.e of 59 the Trust Legal Provisions and are provided without warranty as 60 described in the Simplified BSD License. 62 Table of Contents 64 1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . . 3 65 2. Definition of Terms . . . . . . . . . . . . . . . . . . . . . 3 66 3. LISP-SEC Threat Model . . . . . . . . . . . . . . . . . . . . 4 67 4. Protocol Operations . . . . . . . . . . . . . . . . . . . . . 4 68 5. LISP-SEC Control Messages Details . . . . . . . . . . . . . . 7 69 5.1. Encapsulated Control Message LISP-SEC Extensions . . . . . 7 70 5.2. Map-Reply LISP-SEC Extensions . . . . . . . . . . . . . . 9 71 5.3. Map-Register LISP-SEC Extentions . . . . . . . . . . . . . 10 72 5.4. ITR Processing . . . . . . . . . . . . . . . . . . . . . . 10 73 5.4.1. Map-Reply Record Validation . . . . . . . . . . . . . 12 74 5.4.2. PITR Processing . . . . . . . . . . . . . . . . . . . 13 75 5.5. Encrypting and Decrypting an OTK . . . . . . . . . . . . . 13 76 5.6. Map-Resolver Processing . . . . . . . . . . . . . . . . . 14 77 5.7. Map-Server Processing . . . . . . . . . . . . . . . . . . 14 78 5.7.1. Map-Server Processing in Proxy mode . . . . . . . . . 15 79 5.8. ETR Processing . . . . . . . . . . . . . . . . . . . . . . 15 80 6. Security Considerations . . . . . . . . . . . . . . . . . . . 16 81 6.1. Mapping System Security . . . . . . . . . . . . . . . . . 16 82 6.2. Random Number Generation . . . . . . . . . . . . . . . . . 16 83 6.3. Map-Server and ETR Colocation . . . . . . . . . . . . . . 17 84 7. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 17 85 7.1. HMAC functions . . . . . . . . . . . . . . . . . . . . . . 17 86 7.2. Key Wrap Functions . . . . . . . . . . . . . . . . . . . . 17 87 7.3. Key Derivation Functions . . . . . . . . . . . . . . . . . 18 88 8. Acknowledgements . . . . . . . . . . . . . . . . . . . . . . . 18 89 9. Normative References . . . . . . . . . . . . . . . . . . . . . 18 90 Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . . 19 92 1. Introduction 94 The Locator/ID Separation Protocol [I-D.ietf-lisp] defines a set of 95 functions for routers to exchange information used to map from non- 96 routable Endpoint Identifiers (EIDs) to routable Routing Locators 97 (RLOCs). If these EID-to-RLOC mappings, carried through Map-Reply 98 messages, are transmitted without integrity protection, an adversary 99 can manipulate them and hijack the communication, impersonate the 100 requested EID or mount Denial of Service or Distributed Denial of 101 Service attacks. Also, if the Map-Reply message is transported 102 unauthenticated, an adversarial LISP entity can overclaim an EID- 103 prefix and maliciously redirect traffic directed to a large number of 104 hosts. A detailed description of "overclaiming" attack is provided 105 in [I-D.ietf-lisp-threats]. 107 This memo specifies LISP-SEC, a set of security mechanisms that 108 provide origin authentication, integrity and anti-replay protection 109 to LISP's EID-to-RLOC mapping data conveyed via mapping lookup 110 process. LISP-SEC also enables verification of authorization on EID- 111 prefix claims in Map-Reply messages, ensuring that the sender of a 112 Map-Reply that provides the location for a given EID-prefix is 113 entitled to do so according to the EID prefix registered in the 114 associated Map Server. Map-Register security, including the right 115 for a LISP entity to register an EID-prefix or to claim presence at 116 an RLOC, is out of the scope of LISP-SEC. Additional security 117 considerations are described in Section 6. 119 2. Definition of Terms 121 One-Time Key (OTK): An ephemeral randomly generated key that must 122 be used for a single Map-Request/Map-Reply exchange. 124 ITR-OTK: The One-Time Key generated at the ITR. 126 MS-OTK: The One-Time Key generated at the Map-Server. 128 Encapsulated Control Message (ECM): A LISP control message that is 129 prepended with an additional LISP header. ECM is used by ITRs to 130 send LISP control messages to a Map-Resolver, by Map-Resolvers to 131 forward LISP control messages to a Map-Server, and by Map- 132 Resolvers to forward LISP control messages to an ETR. 134 Authentication Data (AD): Metadata that is included either in a 135 LISP ECM header or in a Map-Reply message to support 136 confidentiality, integrity protection, and verification of EID- 137 prefix authorization. 139 OTK-AD: The portion of ECM Authentication Data that contains a 140 One-Time Key. 142 EID-AD: The portion of ECM and Map-Reply Authentication Data 143 used for verification of EID-prefix authorization. 145 PKT-AD: The portion of Map-Reply Authentication Data used to 146 protect the integrity of the Map-Reply message. 148 For definitions of other terms, notably Map-Request, Map-Reply, 149 Ingress Tunnel Router (ITR), Egress Tunnel Router (ETR), Map-Server 150 (MS) and Map-Resolver (MR) please consult the LISP specification 151 [I-D.ietf-lisp]. 153 3. LISP-SEC Threat Model 155 LISP-SEC addresses the control plane threats, described in 156 [I-D.ietf-lisp-threats], that target EID-to-RLOC mappings, including 157 manipulations of Map-Request and Map-Reply messages, and malicious 158 ETR EID prefix overclaiming. However LISP-SEC makes two main 159 assumptions that are not part of [I-D.ietf-lisp-threats]. First, the 160 LISP mapping system is expected to deliver a Map-Request message to 161 its intended destination ETR as identified by the EID. Second, no 162 man-in-the-middle attack can be mounted within the LISP Mapping 163 System. Furthermore, while LISP-SEC enables detection of EID prefix 164 overclaiming attacks, it assumes that Map Servers can verify the EID 165 prefix authorization at time of registration. 167 According to the threat model described in [I-D.ietf-lisp-threats] 168 LISP-SEC assumes that any kind of attack, including MITM attacks, can 169 be mounted in the access network, outside of the boundaries of the 170 LISP mapping system. An on-path attacker, outside of the LISP 171 mapping system can, for example, hijack Map-Request and Map-Reply 172 messages, spoofing the identity of a LISP node. Another example of 173 on-path attack, called over claiming attack, can be mounted by a 174 malicious Egress Tunnel Router (ETR), by overclaiming the EID- 175 prefixes for which it is authoritative. In this way the ETR can 176 maliciously redirect traffic directed to a large number of hosts. 178 4. Protocol Operations 180 The goal of the security mechanisms defined in [I-D.ietf-lisp] is to 181 prevent unauthorized insertion of mapping data by providing origin 182 authentication and integrity protection for the Map-Registration, and 183 by using the nonce to detect unsolicited Map-Reply sent by off-path 184 attackers. 186 LISP-SEC builds on top of the security mechanisms defined in 187 [I-D.ietf-lisp] to address the threats described in Section 3 by 188 leveraging the trust relationships existing among the LISP entities 189 participating to the exchange of the Map-Request/Map-Reply messages. 190 Those trust relationships are used to securely distribute a One-Time 191 Key (OTK) that provides origin authentication, integrity and anti- 192 replay protection to mapping data conveyed via the mapping lookup 193 process, and that effectively prevent over claiming attacks. The 194 processing of security parameters during the Map-Request/Map-Reply 195 exchange is as follows: 197 o The ITR-OTK is generated and stored at the ITR, and securely 198 transported to the Map-Server. 200 o The Map-Server uses the ITR-OTK to compute an HMAC that protects 201 the integrity of the mapping data known to the Map-Server to 202 prevent overclaiming attacks. The Map-Server also derives a new 203 OTK, the MS-OTK, that is passed to the ETR, by applying a Key 204 Derivation Function (KDF) to the ITR-OTK. 206 o The ETR uses the MS-OTK to compute an HMAC that protects the 207 integrity of the Map-Reply sent to the ITR. 209 o Finally, the ITR uses the stored ITR-OTK to verify the integrity 210 of the mapping data provided by both the Map-Server and the ETR, 211 and to verify that no overclaiming attacks were mounted along the 212 path between the Map-Server and the ITR. 214 Section 5 provides the detailed description of the LISP-SEC control 215 messages and their processing, while the rest of this section 216 describes the flow of protocol operations at each entity involved in 217 the Map-Request/Map-Reply exchange: 219 o The ITR, upon needing to transmit a Map-Request message, generates 220 and stores an OTK (ITR-OTK). This ITR-OTK is included into the 221 Encapsulated Control Message (ECM) that contains the Map-Request 222 sent to the Map-Resolver. To provide confidentiality to the ITR- 223 OTK over the path between the ITR and its Map-Resolver, the ITR- 224 OTK SHOULD be encrypted using a preconfigured key shared between 225 the ITR and the Map-Resolver, similar to the key shared between 226 the ETR and the Map-Server in order to secure ETR registration 227 [I-D.ietf-lisp-ms]. 229 o The Map-Resolver decapsulates the ECM message, decrypts the ITR- 230 OTK, if needed, and forwards through the Mapping System the 231 received Map-Request and the ITR-OTK, as part of a new ECM 232 message. As described in Section 5.6, the LISP Mapping System 233 delivers the ECM to the appropriate Map-Server, as identified by 234 the EID destination address of the Map-Request. 236 o The Map-Server is configured with the location mappings and policy 237 information for the ETR responsible for the EID destination 238 address. Using this preconfigured information, the Map-Server, 239 after the decapsulation of the ECM message, finds the longest 240 match EID-prefix that covers the requested EID in the received 241 Map-Request. The Map-Server adds this EID-prefix, together with 242 an HMAC computed using the ITR-OTK, to a new Encapsulated Control 243 Message that contains the received Map-Request. 245 o The Map-Server derives a new OTK, the MS-OTK, by applying a Key 246 Derivation Function (KDF) to the ITR-OTK. This MS-OTK is included 247 in the Encapsulated Control Message that the Map Server uses to 248 forward the Map-Request to the ETR. To provide MS-OTK 249 confidentiality over the path between the Map-Server and the ETR, 250 the MS-OTK should be encrypted using the key shared between the 251 ETR and the Map-Server in order to secure ETR registration 252 [I-D.ietf-lisp-ms]. 254 o If the Map-Server is acting in proxy mode, as specified in 255 [I-D.ietf-lisp], the ETR is not involved in the generation of the 256 Map-Reply. In this case the Map-Server generates the Map-Reply on 257 behalf of the ETR as described below. 259 o The ETR, upon receiving the ECM encapsulated Map-Request from the 260 Map-Server, decrypts the MS-OTK, if needed, and originates a 261 standard Map-Reply that contains the EID-to-RLOC mapping 262 information as specified in [I-D.ietf-lisp]. 264 o The ETR computes an HMAC over this standard Map-Reply, keyed with 265 MS-OTK to protect the integrity of the whole Map-Reply. The ETR 266 also copies the EID-prefix authorization data that the Map-Server 267 included in the ECM encapsulated Map-Request into the Map-Reply 268 message. The ETR then sends this complete Map-Reply message to 269 the requesting ITR. 271 o The ITR, upon receiving the Map-Reply, uses the locally stored 272 ITR-OTK to verify the integrity of the EID-prefix authorization 273 data included in the Map-Reply by the Map-Server. The ITR 274 computes the MS-OTK by applying the same KDF used by the Map- 275 Server, and verifies the integrity of the Map-Reply. If the 276 integrity checks fail, the Map-Reply MUST be discarded. Also, if 277 the EID-prefixes claimed by the ETR in the Map-Reply are not equal 278 to or more specific than the EID-prefix authorization data 279 inserted by the Map-Server, the ITR MUST discard the Map-Reply. 281 5. LISP-SEC Control Messages Details 283 LISP-SEC metadata associated with a Map-Request is transported within 284 the Encapsulated Control Message that contains the Map-Request. 286 LISP-SEC metadata associated with the Map-Reply is transported within 287 the Map-Reply itself. 289 5.1. Encapsulated Control Message LISP-SEC Extensions 291 LISP-SEC uses the ECM (Encapsulated Control Message) defined in 292 [I-D.ietf-lisp] with Type set to 8, and S bit set to 1 to indicate 293 that the LISP header includes Authentication Data (AD). The format 294 of the LISP-SEC ECM Authentication Data is defined in the following 295 figure. OTK-AD stands for One-Time Key Authentication Data and 296 EID-AD stands for EID Authentication Data. 298 0 1 2 3 299 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 1 300 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 301 | AD Type |V| Reserved | Requested HMAC ID | 302 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+\ 303 | OTK Length | OTK Encryption ID | | 304 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | 305 | One-Time-Key Preamble ... | | 306 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ OTK-AD 307 | ... One-Time-Key Preamble | | 308 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | 309 ~ One-Time Key (128 bits) ~/ 310 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ <---+ 311 | EID-AD Length | KDF ID | | 312 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | 313 | Record Count | Reserved | EID HMAC ID | EID-AD 314 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+\ | 315 | Reserved | EID mask-len | EID-AFI | | | 316 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ Rec | 317 ~ EID-prefix ... ~ | | 318 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+/ | 319 ~ EID HMAC ~ | 320 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ <---+ 322 LISP-SEC ECM Authentication Data 324 AD Type: 1 (LISP-SEC Authentication Data) 326 V: Key Version bit. This bit is toggled when the sender switches 327 to a new OTK wrapping key 329 Reserved: Set to 0 on transmission and ignored on receipt. 331 Requested HMAC ID: The HMAC algorithm requested by the ITR. See 332 Section 5.4 for details. 334 OTK Length: The length (in bytes) of the OTK Authentication Data 335 (OTK-AD), that contains the OTK Preamble and the OTK. 337 OTK Encryption ID: The identifier of the key wrapping algorithm 338 used to encrypt the One-Time-Key. When a 128-bit OTK is sent 339 unencrypted by the Map-Resolver, the OTK Encryption ID is set to 340 NULL_KEY_WRAP_128. See Section 5.5 for more details. 342 One-Time-Key Preamble: set to 0 if the OTK is not encrypted. When 343 the OTK is encrypted, this field may carry additional metadata 344 resulting from the key wrapping operation. When a 128-bit OTK is 345 sent unencrypted by Map-Resolver, the OTK Preamble is set to 346 0x0000000000000000 (64 bits). See Section 5.5 for details. 348 One-Time-Key: the OTK encrypted (or not) as specified by OTK 349 Encryption ID. See Section 5.5 for details. 351 EID-AD Length: length (in bytes) of the EID Authentication Data 352 (EID-AD). The ITR MUST set EID-AD Length to 4 bytes, as it only 353 fills the KDF ID field, and all the remaining fields part of the 354 EID-AD are not present. An EID-AD MAY contain multiple EID- 355 records. Each EID-record is 4-byte long plus the length of the 356 AFI-encoded EID-prefix. 358 KDF ID: Identifier of the Key Derivation Function used to derive 359 the MS-OTK. The ITR SHOULD use this field to indicate the 360 recommended KDF algorithm, according to local policy. The Map- 361 Server can overwrite the KDF ID if it does not support the KDF ID 362 recommended by the ITR. See Section 5.4 for more details. 364 Record Count: The number of records in this Map-Request message. 365 A record is comprised of the portion of the packet that is labeled 366 'Rec' above and occurs the number of times equal to Record Count. 368 Reserved: Set to 0 on transmission and ignored on receipt. 370 EID HMAC ID: Identifier of the HMAC algorithm used to protect the 371 integrity of the EID-AD. This field is filled by Map-Server that 372 computed the EID-prefix HMAC. See Section 5.4 for more details. 374 EID mask-len: Mask length for EID-prefix. 376 EID-AFI: Address family of EID-prefix according to [RFC5226] 378 EID-prefix: The Map-Server uses this field to specify the EID- 379 prefix that the destination ETR is authoritative for, and is the 380 longest match for the requested EID. 382 EID HMAC: HMAC of the EID-AD computed and inserted by Map-Server. 383 Before computing the HMAC operation the EID HMAC field MUST be set 384 to 0. The HMAC covers the entire EID-AD. 386 5.2. Map-Reply LISP-SEC Extensions 388 LISP-SEC uses the Map-Reply defined in [I-D.ietf-lisp], with Type set 389 to 2, and S bit set to 1 to indicate that the Map-Reply message 390 includes Authentication Data (AD). The format of the LISP-SEC Map- 391 Reply Authentication Data is defined in the following figure. PKT-AD 392 is the Packet Authentication Data that covers the Map-Reply payload. 393 0 1 2 3 394 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 1 395 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 396 | AD Type | Reserved | 397 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ <---+ 398 | EID-AD Length | KDF ID | | 399 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | 400 | Record Count | Reserved | EID HMAC ID | EID-AD 401 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+\ | 402 | Reserved | EID mask-len | EID-AFI | | | 403 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ Rec | 404 ~ EID-prefix ... ~ | | 405 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+/ | 406 ~ EID HMAC ~ | 407 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ <---+ 408 | PKT-AD Length | PKT HMAC ID |\ 409 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | 410 ~ PKT HMAC ~ PKT-AD 411 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+/ 413 LISP-SEC Map-Reply Authentication Data 415 AD Type: 1 (LISP-SEC Authentication Data) 417 EID-AD Length: length (in bytes) of the EID-AD. An EID-AD MAY 418 contain multiple EID-records. Each EID-record is 4-byte long plus 419 the length of the AFI-encoded EID-prefix. 421 KDF ID: Identifier of the Key Derivation Function used to derive 422 MS-OTK. See Section 5.7 for more details. 424 Record Count: The number of records in this Map-Reply message. A 425 record is comprised of the portion of the packet that is labeled 426 'Rec' above and occurs the number of times equal to Record Count. 428 Reserved: Set to 0 on transmission and ignored on receipt. 430 EID HMAC ID: Identifier of the HMAC algorithm used to protect the 431 integrity of the EID-AD. See Section 5.7 for more details. 433 EID mask-len: Mask length for EID-prefix. 435 EID-AFI: Address family of EID-prefix according to [RFC5226]. 437 EID-prefix: This field contains an EID-prefix that the destination 438 ETR is authoritative for, and is the longest match for the 439 requested EID. 441 EID HMAC: HMAC of the EID-AD, as computed by the Map-Server. 442 Before computing the HMAC operation the EID HMAC field MUST be set 443 to 0. The HMAC covers the entire EID-AD. 445 PKT-AD Length: length (in bytes) of the Packet Authentication Data 446 (PKT-AD). 448 PKT HMAC ID: Identifier of the HMAC algorithm used to protect the 449 integrity of the Map-reply Location Data. 451 PKT HMAC: HMAC of the whole Map-Reply packet, including the LISP- 452 SEC Authentication Data. The scope of the authentication goes 453 from the Map-Reply Type field to the PKT HMAC field included. 454 Before computing the HMAC operation the PKT HMAC field MUST be set 455 to 0. See Section 5.8 for more details. 457 5.3. Map-Register LISP-SEC Extentions 459 The second bit after the Type field in a Map-Register message is 460 allocated as the S bit. The S bit indicates to the Map-Server that 461 the registering ETR is LISP-SEC enabled. An ETR that supports LISP- 462 SEC MUST set the S bit in its Map-Register messages. 464 5.4. ITR Processing 466 Upon creating a Map-Request, the ITR generates a random ITR-OTK that 467 is stored locally, together with the nonce generated as specified in 468 [I-D.ietf-lisp]. 470 The Map-Request MUST be encapsulated in an ECM, with the S-bit set to 471 1, to indicate the presence of Authentication Data. If the ITR and 472 the Map-Resolver are configured with a shared key, the ITR-OTK 473 confidentiality SHOULD be protected by wrapping the ITR-OTK with the 474 algorithm specified by the OTK Encryption ID field. See Section 5.5 475 for further details on OTK encryption. 477 The Requested HMAC ID field contains the suggested HMAC algorithm to 478 be used by the Map-Server and the ETR to protect the integrity of the 479 ECM Authentication data and of the Map-Reply. 481 The KDF ID field, specifies the suggested key derivation function to 482 be used by the Map-Server to derive the MS-OTK. 484 The EID-AD length is set to 4 bytes, since the Authentication Data 485 does not contain EID-prefix Authentication Data, and the EID-AD 486 contains only the KDF ID field. 488 In response to an encapsulated Map-Request that has the S-bit set, an 489 ITR MUST receive a Map-Reply with the S-bit set, that includes an 490 EID-AD and a PKT-AD. If the Map-Reply does not include both ADs, the 491 ITR MUST discard it. In response to an encapsulated Map-Request with 492 S-bit set to 0, the ITR expects a Map-Reply with S-bit set to 0, and 493 the ITR SHOULD discard the Map-Reply if the S-bit is set. 495 Upon receiving a Map-Reply, the ITR must verify the integrity of both 496 the EID-AD and the PKT-AD, and MUST discard the Map-Reply if one of 497 the integrity checks fails. 499 The integrity of the EID-AD is verified using the locally stored ITR- 500 OTK to re-compute the HMAC of the EID-AD using the algorithm 501 specified in the EID HMAC ID field. If the EID HMAC ID field does 502 not match the Requested HMAC ID the ITR SHOULD discard the Map-Reply 503 and send, at the first opportunity it needs to, a new Map-Request 504 with a different Requested HMAC ID field, according to ITR's local 505 policy. The ITR MUST set the EID HMAC ID field to 0 before computing 506 the HMAC. 508 To verify the integrity of the PKT-AD, first the MS-OTK is derived 509 from the locally stored ITR-OTK using the algorithm specified in the 510 KDF ID field. This is because the PKT-AD is generated by the ETR 511 using the MS-OTK. If the KDF ID in the Map-Reply does not match the 512 KDF ID requested in the Map-Request, the ITR SHOULD discard the Map- 513 Reply and send, at the first opportunity it needs to, a new Map- 514 Request with a different KDF ID, according to ITR's local policy. 515 The derived MS-OTK is then used to re-compute the HMAC of the PKT-AD 516 using the Algorithm specified in the PKT HMAC ID field. If the PKT 517 HMAC ID field does not match the Requested HMAC ID the ITR SHOULD 518 discard the Map-Reply and send, at the first opportunity it needs to, 519 a new Map-Request with a different Requested HMAC ID according to 520 ITR's local policy. 522 Each individual Map-Reply EID-record is considered valid only if: (1) 523 both EID-AD and PKT-AD are valid, and (2) the intersection of the 524 EID-prefix in the Map-Reply EID-record with one of the EID-prefixes 525 contained in the EID-AD is not empty. After identifying the Map- 526 Reply record as valid, the ITR sets the EID-prefix in the Map-Reply 527 record to the value of the intersection set computed before, and adds 528 the Map-Reply EID-record to its EID-to-RLOC cache, as described in 529 [I-D.ietf-lisp]. An example of Map-Reply record validation is 530 provided in Section 5.4.1. 532 The ITR SHOULD send SMR triggered Map Requests over the mapping 533 system in order to receive a secure Map-Reply. If an ITR accepts 534 piggybacked Map-Replies, it SHOULD also send a Map-Request over the 535 mapping system in order to securely verify the piggybacked Map-Reply. 537 5.4.1. Map-Reply Record Validation 539 The payload of a Map-Reply may contain multiple EID-records. The 540 whole Map-Reply is signed by the ETR, with the PKT HMAC, to provide 541 integrity protection and origin authentication to the EID-prefix 542 records claimed by the ETR. The Authentication Data field of a Map- 543 Reply may contain multiple EID-records in the EID-AD. The EID-AD is 544 signed by the Map-Server, with the EID HMAC, to provide integrity 545 protection and origin authentication to the EID-prefix records 546 inserted by the Map-Server. 548 Upon receiving a Map-Reply with the S-bit set, the ITR first checks 549 the validity of both the EID HMAC and of the PKT-AD HMAC. If either 550 one of the HMACs is not valid, a log message is issued and the Map- 551 Reply is not processed any further. If both HMACs are valid, the ITR 552 proceeds with validating each individual EID-record claimed by the 553 ETR by computing the intersection of each one of the EID-prefix 554 contained in the payload of the Map-Reply with each one of the EID- 555 prefixes contained in the EID-AD. An EID-record is valid only if at 556 least one of the intersections is not the empty set. 558 For instance, the Map-Reply payload contains 3 mapping record EID- 559 prefixes: 561 1.1.1.0/24 563 1.1.2.0/24 564 1.2.0.0/16 566 The EID-AD contains two EID-prefixes: 568 1.1.2.0/24 570 1.2.3.0/24 572 The EID-record with EID-prefix 1.1.1.0/24 is not processed since it 573 is not included in any of the EID-ADs signed by the Map-Server. A 574 log message is issued. 576 The EID-record with EID-prefix 1.1.2.0/24 is stored in the map-cache 577 because it matches the second EID-prefix contained in the EID-AD. 579 The EID-record with EID-prefix 1.2.0.0/16 is not processed since it 580 is not included in any of the EID-ADs signed by the Map-Server. A 581 log message is issued. In this last example the ETR is trying to 582 over claim the EID-prefix 1.2.0.0/16, but the Map-Server authorized 583 only 1.2.3.0/24, hence the EID-record is discarded. 585 5.4.2. PITR Processing 587 The processing performed by a PITR is equivalent to the processing of 588 an ITR. However, if the PITR is directly connected to the ALT, the 589 PITR performs the functions of both the ITR and the Map-Resolver 590 forwarding the Map-Request encapsulated in an ECM header that 591 includes the Authentication Data fields as described in Section 5.6. 593 5.5. Encrypting and Decrypting an OTK 595 MS-OTK confidentiality is required in the path between the Map-Server 596 and the ETR, the MS-OTK SHOULD be encrypted using the preconfigured 597 key shared between the Map-Server and the ETR for the purpose of 598 securing ETR registration [I-D.ietf-lisp-ms]. Similarly, if ITR-OTK 599 confidentiality is required in the path between the ITR and the Map- 600 Resolver, the ITR-OTK SHOULD be encrypted with a key shared between 601 the ITR and the Map-Resolver. 603 The OTK is encrypted using the algorithm specified in the OTK 604 Encryption ID field. When the AES Key Wrap algorithm is used to 605 encrypt a 128-bit OTK, according to [RFC3339], the AES Key Wrap 606 Initialization Value MUST be set to 0xA6A6A6A6A6A6A6A6 (64 bits). 607 The output of the AES Key Wrap operation is 192-bit long. The most 608 significant 64-bit are copied in the One-Time Key Preamble field, 609 while the 128 less significant bits are copied in the One-Time Key 610 field of the LISP-SEC Authentication Data. 612 When decrypting an encrypted OTK the receiver MUST verify that the 613 Initialization Value resulting from the AES Key Wrap decryption 614 operation is equal to 0xA6A6A6A6A6A6A6A6. If this verification fails 615 the receiver MUST discard the entire message. 617 When a 128-bit OTK is sent unencrypted the OTK Encryption ID is set 618 to NULL_KEY_WRAP_128, and the OTK Preamble is set to 619 0x0000000000000000 (64 bits). 621 5.6. Map-Resolver Processing 623 Upon receiving an encapsulated Map-Request with the S-bit set, the 624 Map-Resolver decapsulates the ECM message. The ITR-OTK, if 625 encrypted, is decrypted as specified in Section 5.5. 627 The Map-Resolver, as specified in [I-D.ietf-lisp-ms], originates a 628 new ECM header with the S-bit set, that contains the unencrypted ITR- 629 OTK, as specified in Section 5.5, and the other data derived from the 630 ECM Authentication Data of the received encapsulated Map-Request. 632 The Map-Resolver then forwards the received Map-Request, encapsulated 633 in the new ECM header that includes the newly computed Authentication 634 Data fields. 636 5.7. Map-Server Processing 638 Upon receiving an ECM encapsulated Map-Request with the S-bit set, 639 the Map-Server process the Map-Request according to the value of the 640 S-bit contained in the Map-Register sent by the ETR during 641 registration. 643 If the S-bit contained in the Map-Register was clear the Map-Server 644 decapsulates the ECM and generates a new ECM encapsulated Map-Request 645 that does not contain an ECM Authentication Data, as specified in 646 [I-D.ietf-lisp]. The Map-Server does not perform any further LISP- 647 SEC processing. 649 If the S-bit contained in the Map-Register was set the Map-Server 650 decapsulates the ECM and generates a new ECM Authentication Data. 651 The Authentication Data includes the OTK-AD and the EID-AD, that 652 contains EID-prefix authorization information, that are ultimately 653 sent to the requesting ITR. 655 The Map-Server updates the OTK-AD by deriving a new OTK (MS-OTK) from 656 the ITR-OTK received with the Map-Request. MS-OTK is derived 657 applying the key derivation function specified in the KDF ID field. 658 If the algorithm specified in the KDF ID field is not supported, the 659 Map-Server uses a different algorithm to derive the key and updates 660 the KDF ID field accordingly. 662 The Map-Server and the ETR MUST be configured with a shared key for 663 mapping registration according to [I-D.ietf-lisp-ms]. If MS-OTK 664 confidentiality is required, then the MS-OTK SHOULD be encrypted, by 665 wrapping the MS-OTK with the algorithm specified by the OTK 666 Encryption ID field as specified in Section 5.5. 668 The Map-Server includes in the EID-AD the longest match registered 669 EID-prefix for the destination EID, and an HMAC of this EID-prefix. 670 The HMAC is keyed with the ITR-OTK contained in the received ECM 671 Authentication Data, and the HMAC algorithm is chosen according to 672 the Requested HMAC ID field. If The Map-Server does not support this 673 algorithm, the Map-Server uses a different algorithm and specifies it 674 in the EID HMAC ID field. The scope of the HMAC operation covers the 675 entire EID-AD, from the EID-AD Length field to the EID HMAC field, 676 which must be set to 0 before the computation. 678 The Map-Server then forwards the updated ECM encapsulated Map- 679 Request, that contains the OTK-AD, the EID-AD, and the received Map- 680 Request to an authoritative ETR as specified in [I-D.ietf-lisp]. 682 5.7.1. Map-Server Processing in Proxy mode 684 If the Map-Server is in proxy mode, it generates a Map-Reply, as 685 specified in [I-D.ietf-lisp], with the S-bit set to 1. The Map-Reply 686 includes the Authentication Data that contains the EID-AD, computed 687 as specified in Section 5.7, as well as the PKT-AD computed as 688 specified in Section 5.8. 690 5.8. ETR Processing 692 Upon receiving an ECM encapsulated Map-Request with the S-bit set, 693 the ETR decapsulates the ECM message. The OTK field, if encrypted, 694 is decrypted as specified in Section 5.5 to obtain the unencrypted 695 MS-OTK. 697 The ETR then generates a Map-Reply as specified in [I-D.ietf-lisp] 698 and includes the Authentication Data that contains the EID-AD, as 699 received in the encapsulated Map-Request, as well as the PKT-AD. 701 The EID-AD is copied from the Authentication Data of the received 702 encapsulated Map-Request. 704 The PKT-AD contains the HMAC of the whole Map-Reply packet, keyed 705 with the MS-OTK and computed using the HMAC algorithm specified in 706 the Requested HMAC ID field of the received encapsulated Map-Request. 707 If the ETR does not support the Requested HMAC ID, it uses a 708 different algorithm and updates the PKT HMAC ID field accordingly. 709 The scope of the HMAC operation covers the entire PKT-AD, from the 710 Map-Reply Type field to the PKT HMAC field, which must be set to 0 711 before the computation. 713 Finally the ETR sends the Map-Reply to the requesting ITR as 714 specified in [I-D.ietf-lisp]. 716 6. Security Considerations 718 6.1. Mapping System Security 720 The LISP-SEC threat model described in Section 3, assumes that the 721 LISP Mapping System is working properly and eventually delivers Map- 722 Request messages to a Map-Server that is authoritative for the 723 requested EID. 725 Security is not yet embedded in LISP+ALT but BGP route filtering 726 SHOULD be deployed in the ALT infrastructure to enforce proper 727 routing in the mapping system. The SIDR working group is currently 728 addressing prefix and route advertisement authorization and 729 authentication for BGP. While following SIDR recommendations in the 730 global Internet will take time, applying these recommendations to the 731 ALT, which relies on BGP, should be less complex, as ALT is currently 732 small and with a limited number of operators. Ultimately, deploying 733 the SIDR recommendations in ALT further ensures that the fore 734 mentioned assumption is true. 736 It is also assumed that no man-in-the-middle attack can be carried 737 out against the ALT router to ALT router tunnels, and that the 738 information included into the Map-Requests, in particular the OTK, 739 cannot be read by third-party entities. It should be noted that the 740 integrity of the Map-Request in the ALT is protected by BGP 741 authentication, and that in order to provide OTK confidentiality in 742 the ALT mapping system the ALT router to ALT router tunnels MAY be 743 deployed using IPsec (ESP). 745 Map-Register security, including the right for a LISP entity to 746 register an EID-prefix or to claim presence at an RLOC, is out of the 747 scope of LISP-SEC. 749 6.2. Random Number Generation 751 The ITR-OTK MUST be generated by a properly seeded pseudo-random (or 752 strong random) source. See [RFC4086] for advice on generating 753 security-sensitive random data 755 6.3. Map-Server and ETR Colocation 757 If the Map-Server and the ETR are colocated, LISP-SEC does not 758 provide protection from overclaiming attacks mounted by the ETR. 759 However, in this particular case, since the ETR is within the trust 760 boundaries of the Map-Server, ETR's overclaiming attacks are not 761 included in the threat model. 763 7. IANA Considerations 765 7.1. HMAC functions 767 The following HMAC ID values are defined by this memo for use as 768 Requested HMAC ID, EID HMAC ID, and PKT HMAC ID in the LISP-SEC 769 Authentication Data: 771 Name Number Defined In 772 ------------------------------------------------- 773 NONE 0 774 AUTH-HMAC-SHA-1-96 1 [RFC2104] 775 AUTH-HMAC-SHA-256-128 2 [RFC4634] 777 values 2-65535 are reserved to IANA. 779 HMAC Functions 781 AUTH-HMAC-SHA-1-96 MUST be supported, AUTH-HMAC-SHA-256-128 should be 782 supported. 784 7.2. Key Wrap Functions 786 The following OTK Encryption ID values are defined by this memo for 787 use as OTK key wrap algorithms ID in the LISP-SEC Authentication 788 Data: 790 Name Number Defined In 791 ------------------------------------------------- 792 NULL-KEY-WRAP-128 1 793 AES-KEY-WRAP-128 2 [RFC3394] 795 values 0 and 3-65535 are reserved to IANA. 797 Key Wrap Functions 799 NULL-KEY-WRAP-128, and AES-KEY-WRAP-128 MUST be supported. 801 NULL-KEY-WRAP-128 is used to carry an unencrypted 128-bit OTK, with a 802 64-bit preamble set to 0x0000000000000000 (64 bits). 804 7.3. Key Derivation Functions 806 The following KDF ID values are defined by this memo for use as KDF 807 ID in the LISP-SEC Authentication Data: 809 Name Number Defined In 810 ------------------------------------------------- 811 NONE 0 812 HKDF-SHA1-128 1 [RFC5869] 814 values 2-65535 are reserved to IANA. 816 Key Derivation Functions 818 HKDF-SHA1-128 MUST be supported 820 8. Acknowledgements 822 The authors would like to acknowledge Pere Monclus, Dave Meyer, Dino 823 Farinacci, Brian Weis, David McGrew, Darrel Lewis and Landon Curt 824 Noll for their valuable suggestions provided during the preparation 825 of this document. 827 9. Normative References 829 [I-D.ietf-lisp] 830 Farinacci, D., Fuller, V., Meyer, D., and D. Lewis, 831 "Locator/ID Separation Protocol (LISP)", 832 draft-ietf-lisp-23 (work in progress), May 2012. 834 [I-D.ietf-lisp-interworking] 835 Lewis, D., Meyer, D., Farinacci, D., and V. Fuller, 836 "Interworking LISP with IPv4 and IPv6", 837 draft-ietf-lisp-interworking-06 (work in progress), 838 March 2012. 840 [I-D.ietf-lisp-ms] 841 Fuller, V. and D. Farinacci, "LISP Map Server Interface", 842 draft-ietf-lisp-ms-16 (work in progress), March 2012. 844 [I-D.ietf-lisp-threats] 845 Saucez, D., Iannone, L., and O. Bonaventure, "LISP Threats 846 Analysis", draft-ietf-lisp-threats-02 (work in progress), 847 September 2012. 849 [RFC2104] Krawczyk, H., Bellare, M., and R. Canetti, "HMAC: Keyed- 850 Hashing for Message Authentication", RFC 2104, 851 February 1997. 853 [RFC2119] Bradner, S., "Key words for use in RFCs to Indicate 854 Requirement Levels", BCP 14, RFC 2119, March 1997. 856 [RFC3394] Schaad, J. and R. Housley, "Advanced Encryption Standard 857 (AES) Key Wrap Algorithm", RFC 3394, September 2002. 859 [RFC4086] Eastlake, D., Schiller, J., and S. Crocker, "Randomness 860 Requirements for Security", BCP 106, RFC 4086, June 2005. 862 [RFC5226] Narten, T. and H. Alvestrand, "Guidelines for Writing an 863 IANA Considerations Section in RFCs", BCP 26, RFC 5226, 864 May 2008. 866 [RFC5869] Krawczyk, H. and P. Eronen, "HMAC-based Extract-and-Expand 867 Key Derivation Function (HKDF)", RFC 5869, May 2010. 869 Authors' Addresses 871 Fabio Maino 872 Cisco Systems 873 170 Tasman Drive 874 San Jose, California 95134 875 USA 877 Email: fmaino@cisco.com 879 Vina Ermagan 880 Cisco Systems 881 170 Tasman Drive 882 San Jose, California 95134 883 USA 885 Email: vermagan@cisco.com 886 Albert Cabellos 887 Technical University of Catalonia 888 c/ Jordi Girona s/n 889 Barcelona, 08034 890 Spain 892 Email: acabello@ac.upc.edu 894 Damien Saucez 895 INRIA 896 2004 route des Lucioles - BP 93 897 Sophia Antipolis, 898 France 900 Email: damien.saucez@inria.fr 902 Olivier Bonaventure 903 Universite Catholique de Louvain 904 Place St. Barbe 2 905 Louvain-la-Neuve, 906 Belgium 908 Email: olivier.bonaventure@uclouvain.be