idnits 2.17.1 draft-ietf-6lo-ap-nd-01.txt: Checking boilerplate required by RFC 5378 and the IETF Trust (see https://trustee.ietf.org/license-info): ---------------------------------------------------------------------------- No issues found here. Checking nits according to https://www.ietf.org/id-info/1id-guidelines.txt: ---------------------------------------------------------------------------- No issues found here. Checking nits according to https://www.ietf.org/id-info/checklist : ---------------------------------------------------------------------------- -- The draft header indicates that this document updates RFC6775, but the abstract doesn't seem to directly say this. It does mention RFC6775 though, so this could be OK. Miscellaneous warnings: ---------------------------------------------------------------------------- == The copyright year in the IETF Trust and authors Copyright Line does not match the current year -- The document date (May 15, 2017) is 2531 days in the past. Is this intentional? Checking references for intended status: Proposed Standard ---------------------------------------------------------------------------- (See RFCs 3967 and 4897 for information about using normative references to lower-maturity documents in RFCs) ** Downref: Normative reference to an Informational RFC: RFC 4903 ** Downref: Normative reference to an Informational RFC: RFC 4919 ** Downref: Normative reference to an Informational RFC: RFC 5889 ** Downref: Normative reference to an Informational RFC: RFC 6234 ** Downref: Normative reference to an Informational RFC: RFC 7102 ** Downref: Normative reference to an Informational RFC: RFC 7039 ** Downref: Normative reference to an Informational RFC: RFC 7748 == Outdated reference: A later version (-20) exists of draft-ietf-6lo-backbone-router-03 == Outdated reference: A later version (-30) exists of draft-ietf-6tisch-architecture-11 Summary: 7 errors (**), 0 flaws (~~), 3 warnings (==), 2 comments (--). Run idnits with the --verbose option for more detailed information about the items above. -------------------------------------------------------------------------------- 2 6lo B. Sarikaya, Ed. 3 Internet-Draft Huawei USA 4 Updates: 6775 (if approved) P. Thubert 5 Intended status: Standards Track Cisco 6 Expires: November 16, 2017 M. Sethi, Ed. 7 Ericsson 8 May 15, 2017 10 Address Protected Neighbor Discovery for Low-power and Lossy Networks 11 draft-ietf-6lo-ap-nd-01 13 Abstract 15 This document defines an extension to 6LoWPAN Neighbor Discovery. 16 This extension is designed for low-power and lossy network 17 environments and it supports multi-hop operation. Nodes supporting 18 this extension compute a Cryptographically Unique Interface ID and 19 associate it with one or more of their Registered Addresses. The 20 Cryptographic ID (Crypto-ID) uniquely identifies the owner of the 21 Registered Address. It is used in place of the EUI-64 address that 22 is specified in RFC 6775. Once an address is registered with a 23 Cryptographic ID, only the owner of that ID can modify the state 24 information of the Registered Address in the 6LR and 6LBR. 26 Status of This Memo 28 This Internet-Draft is submitted in full conformance with the 29 provisions of BCP 78 and BCP 79. 31 Internet-Drafts are working documents of the Internet Engineering 32 Task Force (IETF). Note that other groups may also distribute 33 working documents as Internet-Drafts. The list of current Internet- 34 Drafts is at http://datatracker.ietf.org/drafts/current/. 36 Internet-Drafts are draft documents valid for a maximum of six months 37 and may be updated, replaced, or obsoleted by other documents at any 38 time. It is inappropriate to use Internet-Drafts as reference 39 material or to cite them other than as "work in progress." 41 This Internet-Draft will expire on November 16, 2017. 43 Copyright Notice 45 Copyright (c) 2017 IETF Trust and the persons identified as the 46 document authors. All rights reserved. 48 This document is subject to BCP 78 and the IETF Trust's Legal 49 Provisions Relating to IETF Documents 50 (http://trustee.ietf.org/license-info) in effect on the date of 51 publication of this document. Please review these documents 52 carefully, as they describe your rights and restrictions with respect 53 to this document. Code Components extracted from this document must 54 include Simplified BSD License text as described in Section 4.e of 55 the Trust Legal Provisions and are provided without warranty as 56 described in the Simplified BSD License. 58 Table of Contents 60 1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . 2 61 2. Terminology . . . . . . . . . . . . . . . . . . . . . . . . . 4 62 3. Requirements . . . . . . . . . . . . . . . . . . . . . . . . 4 63 4. Protocol Interactions . . . . . . . . . . . . . . . . . . . . 5 64 4.1. Overview . . . . . . . . . . . . . . . . . . . . . . . . 5 65 4.2. Updating RFC 6775 . . . . . . . . . . . . . . . . . . . . 7 66 4.2.1. Crypto-ID Calculation . . . . . . . . . . . . . . . . 10 67 4.3. Multihop Operation . . . . . . . . . . . . . . . . . . . 13 68 5. Security Considerations . . . . . . . . . . . . . . . . . . . 14 69 6. IANA considerations . . . . . . . . . . . . . . . . . . . . . 14 70 7. Acknowledgements . . . . . . . . . . . . . . . . . . . . . . 14 71 8. Change Log . . . . . . . . . . . . . . . . . . . . . . . . . 14 72 9. References . . . . . . . . . . . . . . . . . . . . . . . . . 15 73 9.1. Normative References . . . . . . . . . . . . . . . . . . 15 74 9.2. Informative references . . . . . . . . . . . . . . . . . 16 75 Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . 17 77 1. Introduction 79 Neighbor discovery for IPv6 [RFC4861] and stateless address 80 autoconfiguration [RFC4862] are together referred to as neighbor 81 discovery protocols (NDP). They are defined for regular hosts that 82 have sufficient memory and computation capabilities. These protocols 83 are however not suitable for resource-constrained devices. 84 Therefore, they require adaptation to work on resource-constrained 85 hosts operating over a low-power and lossy network (LLN). Neighbor 86 Discovery optimizations for 6LoWPAN networks include simple 87 optimizations such as a host address registration feature. This 88 feature uses the address registration option (ARO) which is sent in 89 the unicast Neighbor Solicitation (NS) and Neighbor Advertisement 90 (NA) messages [RFC6775]. 92 With 6LoWPAN ND [RFC6775], the ARO option includes a EUI-64 interface 93 ID to uniquely identify the interface of the Registered Address on 94 the registering device, so as to correlate further registrations for 95 the same address and avoid address duplication. The EUI-64 interface 96 ID is not secure and its ownership cannot be verified. Consequently, 97 any device claiming the same EUI-64 interface ID may take over an 98 existing registration and attract the traffic for that address. The 99 address registration mechanism in [RFC6775] is limited as it does not 100 require a node to prove its ownership of the EUI-64 Interface ID. 101 Therefore, any node connected to the subnet and aware of the 102 registered address to EUI-64 interface ID mapping may effectively 103 fake the same interface ID and steal an address. 105 In this document, we extend 6LoWPAN ND to protect the address 106 ownership with cryptographic material, but as opposed to Secure 107 Neighbor Discovery (SEND) [RFC3971] and Cryptographically Generated 108 Addresses (CGAs) [RFC3972], the cryptographic material generated is 109 not embedded in the Interface ID (IID) as an IPv6 address. Instead, 110 the generated cryptographic ID is used as a correlator associated 111 with the registration of the IP address. This approach is made 112 possible with 6LoWPAN ND [RFC6775], where the 6LR and the 6LBR 113 maintain state information for each Registered Address. If a 114 cryptographic ID is associated with the first 6LoWPAN ND 115 registration, then it can be used to validate any future updates to 116 the registration. 118 In order to achieve this ownership verification, in this extension 119 specification, the EUI-64 interface ID used in 6LoWPAN ND is replaced 120 with cryptographic material whose ownership can be verified. The 121 extension also provides new means for the 6LR to validate ownership 122 of the registration, and thus, the ownership of registered address. 123 The resulting protocol is called Protected Address Registration 124 protocol (ND-PAR). 126 In ND-PAR, a node typically generates one 64-bit cryptographic ID 127 (Crypto-ID) and uses it as Unique Interface ID in the registration of 128 one (or more) of its addresses with the 6LR, which it attaches to and 129 uses as default router. The 6LR validates ownership of the 130 cryptographic ID typically upon creation or update of a registration 131 state, for instance following an apparent movement from one point of 132 attachment to another. The ARO option is modified to carry the 133 Unique Interface ID, and through the DAR/DAC exchange. 135 Compared with SeND, this specification saves ~1Kbyte in every NS/NA 136 message. Also SeND requires one cryptographic address per IPv6 137 address. This specification separates the cryptographic identifier 138 from the IPv6 address so that a node can have more than one IPv6 139 address protected by the same cryptographic identifier. SeND forces 140 the IPv6 address to be cryptographic since it integrates the CGA as 141 an IID. 6LoWPAN derives the IPv6 address from other things like a 142 short address in 802.15.4 to enable a better compression. 144 2. Terminology 146 The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT", 147 "SHOULD", "SHOULD NOT", "RECOMMENDED", "MAY", and "OPTIONAL" in this 148 document are to be interpreted as described in [RFC2119]. 150 Readers are expected to be familiar with all the terms and concepts 151 that are discussed in [RFC3971], [RFC3972], [RFC4861], [RFC4919], 152 [RFC6775], and [I-D.ietf-6lo-backbone-router] which proposes an 153 evolution of [RFC6775] for wider applicability. 155 This document defines Crypto-ID as an identifier of variable size 156 which in most cases is 64 bits long. It is generated using 157 cryptographic means explained later in this document. 159 The document also conforms to the terms and models described in 160 [RFC5889] and uses the vocabulary and the concepts defined in 161 [RFC4291] for the IPv6 Architecture. 163 This document uses [RFC7102] for Terminology in Low power And Lossy 164 Networks. 166 3. Requirements 168 In this section we state requirements of a secure neighbor discovery 169 protocol for low-power and lossy networks. 171 o The protocol MUST be based on the Neighbor Discovery Optimization 172 for Low-power and Lossy Networks protocol defined in [RFC6775]. 173 RFC6775 utilizes optimizations such as host-initiated interactions 174 for sleeping resource-constrained hosts and elimination of 175 multicast address resolution. 177 o New options to be added to Neighbor Solicitation messages MUST 178 lead to small packet sizes, especially compared with existing 179 protocols such as SEcure Neighbor Discovery (SEND). Smaller 180 packet sizes facilitate low-power transmission by resource- 181 constrained nodes on lossy links. 183 o The support for this registration mechanism SHOULD be extensible 184 to more LLN links than IEEE 802.15.4 only. Support for at least 185 the LLN links for which a 6lo "IPv6 over foo" specification 186 exists, as well as Low-Power Wi-Fi SHOULD be possible. 188 o As part of this extension, a mechanism to compute a unique 189 Identifier should be provided with the capability to form a Link 190 Local Address that SHOULD be unique at least within the LLN 191 connected to a 6LBR. 193 o The Address Registration Option used in the ND registration SHOULD 194 be extended to carry the relevant forms of Unique Interface 195 IDentifier. 197 o The Neighbour Discovery should specify the formation of a site- 198 local address that follows the security recommendations from 199 [RFC7217]. 201 4. Protocol Interactions 203 Protected address and registration neighbor discovery protocol (ND- 204 PAR) modifies Neighbor Discovery Optimization for Low-power and Lossy 205 Networks [RFC6775] as explained in this section. 207 4.1. Overview 209 The scope of the present work is a 6LoWPAN Low Power Lossy Network 210 (LLN), typically a stub network connected to a larger IP network via 211 a Border Router called a 6LBR per [RFC6775]. 213 ---+-------- ............ 214 | External Network 215 | 216 +-----+ 217 | | LLN Border 218 | | router 219 +-----+ 220 o o o 221 o o o o 222 o o LLN o o o 223 o o o o 224 o 226 Figure 1: Basic Configuration 228 The 6LBR maintains a registration state for all devices in the 229 attached LLN, and, in conjunction with the first-hop router (the 230 6LR), is in a position to validate uniqueness and grant ownership of 231 an IPv6 address before it can be used in the LLN. This is a 232 fundamental difference with a classical network that relies on IPv6 233 address auto-configuration [RFC4862], where there is no guarantee of 234 ownership from the network, and any IPv6 Neighbor Discovery packet 235 must be individually secured [RFC3971]. 237 In a mesh network, the 6LR is directly connected to the host device. 238 This specification expects that the peer-wise layer-2 security is 239 deployed so that all the packets from a particular host are securely 240 identifiable by the 6LR. The 6LR may be multiple hops away from the 241 6LBR. Packets are routed between the 6LR and the 6LBR via other 242 6LRs. This specification expects that a chain of trust is 243 established so that a packet that was validated by the first 6LR can 244 be safely routed by the next 6LRs to the 6LBR. 246 [I-D.ietf-6tisch-architecture] suggests to use of RPL [RFC6550] as 247 the routing protocol between the 6LRs and the 6LBR, and leveraging a 248 backbone router [I-D.ietf-6lo-backbone-router] to extend the LLN in a 249 larger multilink subnet [RFC4903]. In that model, a registration 250 flow happens as shown in Figure 2. Note that network beyond the 6LBR 251 is out of scope for this document. 253 6LoWPAN Node 6LR 6LBR 254 (RPL leaf) (router) (root) 255 | | | 256 | 6LoWPAN ND |6LoWPAN ND+RPL | Efficient ND 257 | LLN link |Route-Over mesh| IPv6 link 258 | | | 259 | NS(ARO) | | 260 |-------------->| | 261 | 6LoWPAN ND | DAR (then DAO)| 262 | |-------------->| 263 | | | 264 | | | 265 | | | 266 | | | 267 | | | 268 | | | 269 | | | 270 | | DAC | 271 | |<--------------| 272 | NA(ARO) | | 273 |<--------------| | 275 Figure 2: (Re-)Registration Flow over Multi-Link Subnet 277 A new device that joins the network auto-configures an address and 278 performs an initial registration to an on-link 6LR with an NS message 279 that carries a new Address Registration Option (ARO) [RFC6775]. The 280 6LR validates the address with the central 6LBR using a DAR/DAC 281 exchange, and the 6LR confirms (or denies) the address ownership with 282 an NA message that also carries an Address Registration Option. 284 The registration mechanism in [RFC6775] was created for the original 285 purpose of Duplicate Address Detection (DAD), whereby use of an 286 address would be granted as long as the address is not already 287 present in the subnet. But [RFC6775] does not require that the 6LR 288 use the registration for source address validation (SAVI) [RFC7039]. 290 Protected address registration protocol proposed in this document 291 enforces SAVI. With this we ensure that only the correct owner uses 292 the registered address in the source address field. Therefore a 293 destination node can trust that the source is the real owner without 294 using SeND. All packets destined for a node go through the 6LR to 295 which it is attached. The 6LR maintains state information for the 296 registered addressed along with the MAC address, and link-layer 297 cryptographic key associated with that node. The 6LR therefore only 298 delivers packets to the real owner based on its state information. 300 In order to validate address ownership, the registration mechanism 301 (that goes all the way to the 6LBR with the DAR/DAC) enables the 6LBR 302 to correlate further claims for a registered address from the device 303 to which it is granted, based on a Unique Interface IDentifier (UID). 304 This UID is derived from the MAC address of the device (EUI-64). 306 This document uses a randomly generated value as an alternate UID for 307 the registration. Proof of ownership of the UID is passed with the 308 first registration to a given 6LR, and enforced at the 6LR, which 309 validates the proof. With this new operation, the 6LR allows only 310 packets from a connected host if the connected host owns the 311 registration of the source address of the packet. 313 In a multihop 6LoWPAN, the registration with Crypto-ID is propagated 314 to 6LBR as described in Section 4.3. If a chain of trust is present 315 between the 6LR and the 6LBR, then there is no need to propagate the 316 proof of ownership to the 6LBR. All the 6LBR needs to know is that 317 this particular UID is randomly generated, so as to enforce that any 318 update via a different 6LR is also random. 320 4.2. Updating RFC 6775 322 Protocol interactions are as defined in Figure 2. The Crypto-ID is 323 calculated as described in Section 4.2.1. 325 The Target Address field in NS message is set to the prefix 326 concatenated with the node's address. This address does not need 327 duplicate address detection as Crypto-ID is globally unique. So a 328 host cannot steal an address that is already registered unless it has 329 the key used for generating the Crypto-ID. The same Crypto-ID can 330 thus be used to protect multiple addresses e.g. when the node 331 receives a different prefix. 333 Local or on-link protocol interactions are shown in Figure 3. 334 Crypto-ID and ARO are passed to and stored by the 6LR/6LBR on the 335 first NS and not sent again in the next NS. The operation starts 336 with 6LR sending a Router Advertisement (RA) message to 6LN. 338 The 6LR/6LBR ensures first-come/first-serve by storing the ARO and 339 the Crypto-ID correlated to the node being registered. The node is 340 free to claim any address it likes as long as it is the first to make 341 such a claim. The node becomes owner of that address and the address 342 is bound to the Crypto-ID in the 6LR/6LBR registry. This procedure 343 avoids the constrained device to compute multiple keys for multiple 344 addresses. The registration process allows the node to tie all the 345 addresses to the same Crypto-ID and have the 6LR/6LBR enforce first- 346 come first-serve after that. 348 A condition where a 6LN uses multiple IPv6 addresses may happen when 349 the node moves at a different place and receives a different prefix. 350 In this scenario, the node uses the same Crypto-ID to protect its new 351 IPv6 address. This prevents other nodes from stealing the address 352 and trying to use it as their source address. 354 Note that if the device that moves always forms new MAC and IP 355 address [RFC6775], then this new address can be used for 356 registration. In case of a collision of the new MAC and therefore IP 357 address, the node can easily form a new IPv6 address. This is one 358 case where the use of Crypto-ID would not be needed. Crypto-ID or 359 ND-PAR should be activated when the IP address is claimed at another 360 place, or for a different MAC address at the same place, e.g. for MAC 361 address privacy [I-D.ietf-6man-ipv6-address-generation-privacy]. 363 6LN 6LR 364 | | 365 |<------------------- RA --------------------------| 366 | | 367 |----------- NS with ARO and Crypto-ID ----------->| 368 | | 369 |<---------- NA with ARO (status=req-proof) -------| 370 | | 371 |----------- NS with ARO and Crypto-ID ----------->| 372 | | 373 |<---------------- NA with ARO --------------------| 374 | | 375 ... ... 376 | | 377 |------------ NS with ARO and Crypto-ID ---------->| 378 | | 379 | | 380 |<---------------- NA with ARO --------------------| 381 ... ... 382 | | 383 |----------- NS with ARO and Crypto-ID ----------->| 384 | | 385 | | 386 |<---------------- NA with ARO --------------------| 388 Figure 3: On-link Protocol Operation 390 Elliptic Curve Cryptography (ECC) is used in the calculation of 391 cryptographic identifier (Crypto-ID). The digital signature is 392 constructed by using the 6LN's private key over its EUI-64 (MAC) 393 address. The signature value is computed using the ECDSA signature 394 algorithm and the hash function used is SHA-256 [RFC6234]. Public 395 Key is the most important parameter in CGA Parameters (sent by 6LN in 396 an NS message). ECC Public Key could be in uncompressed form or in 397 compressed form where the first octet of the OCTET STRING is 0x04 and 398 0x02 or 0x03, respectively. Point compression can further reduce the 399 key size by about 32 octets. 401 After calculating its Crypto-ID, a 6LN sends it along with the CGA 402 parameters in the first NS message, see Figure 3. In order to send 403 Crypto-ID, a modified address registration option called Enhanced 404 Address Registration Option (EARO) is defined in Figure 4. As 405 defined in the figure this ID is variable length, varying between 64 406 to 128 bits. This ID is 128 bits long only if it is used as IPv6 407 address. This may happen when some application uses one IP address 408 of the device as device ID. It would make sense in that case to 409 build a real CGA IPv6 address. The prefix of the address would be 410 obtained from prefix information option (PIO in RA) [RFC4861]. 412 6LN also sends some other parameters to enable 6LR or 6LBR to verify 413 the Crypto-ID. The option shown in Figure 5 can be used. In the 414 figure, CGA Parameters field contains the public key, prefix and some 415 other values. It is a simplified form of CGA Option defined in 416 [RFC3971]. 418 4.2.1. Crypto-ID Calculation 420 First, the modifier is set to a random or pseudo-random 128-bit 421 value. Next, concatenate from left to right the modifier, 9 zero 422 octets and the ECC public key. SHA-256 algorithm is applied on the 423 concatenation. The 112 leftmost bits of the hash value is taken. 424 Concatenate from left to right the modifier value, the subnet prefix 425 and the encoded public key. NIST P-256 is executed on the 426 concatenation. The leftmost bits of the result is used as the 427 Crypto-ID. The length is normally 64 bits, however it could be 128 428 bits. 430 In respecting the cryptographical algorithm agility [RFC7696], Curve 431 25519 [RFC7748] can also be used instead of NIST P-256. This is 432 indicated by 6LN by setting the Crypto Type field in CGA Parameters 433 Option to a value of 1. If 6LBR does not support Curve 25519, it 434 will set Crypto Type field to zero. This means that the default 435 algorithm (NIST P-256) will be used. 437 0 1 2 3 438 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 1 439 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 440 | Type | Length | Status | Reserved | 441 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 442 | Reserved |C|T| TID | Registration Lifetime | 443 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 444 | | 445 + Owner Unique ID (EUI-64 or equivalent) + 446 | | 447 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 449 Figure 4: Enhanced Address Registration Option 451 Type: 453 TBA1 455 Length: 457 8-bit unsigned integer. The length of the option (including the 458 type and length fields) in units of 8 bytes. The value 0 is 459 invalid. A value of 3 with the C flag set indicates a Crypto-ID 460 of 128 bits. 462 Status: 464 8-bit unsigned integer. Indicates the status of a registration in 465 the NA response. MUST be set to 0 in NS messages. See below. 467 Reserved: 469 This field is unused. It MUST be initialized to zero by the 470 sender and MUST be ignored by the receiver. 472 C: 474 C bit when set is used to indicate that Owner Unique ID fields 475 contains Crypto-ID. 477 T and TID: 479 Defined in [I-D.ietf-6lo-backbone-router]. 481 Owner Unique ID: 483 In this specification, this field contains Crypto-ID, a variable 484 length field to carry the Crypto-ID or random UID. This field is 485 normally 64 bits long. It could be 128 bits long if IPv6 address 486 is used as the Crypto-ID. 488 0 1 2 3 489 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 1 490 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 491 | Type | Length | Pad Length | Crypto Type | 492 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 493 | | 494 + + 495 | | 496 + Modifier (16 octets) + 497 | | 498 + + 499 | | 500 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 501 | | 502 + Subnet Prefix (8 octets) + 503 | | 504 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 505 | | 506 | | 507 + Public Key (variable length) + 508 | | 509 | | 510 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 511 | | 512 . . 513 . Padding . 514 . . 515 | | 516 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 518 Figure 5: CGA Parameters Option 520 Type: 522 TBA2 524 Length: 526 The length of the option in units of 8 octets. 528 Pad Length: 530 The length of the Padding field. 532 Crypto Type: 534 The type of cryptographic algorithm used in calculation Crypto-ID. 535 Default value of all zeros indicate NIST P-256. A value of 1 is 536 assigned for Curve 25519. New values may be defined later. 538 Modifier: 540 128 bit random value. 542 Subnet Prefix: 544 64 bit subnet prefix. 546 Public Key: 548 ECC public key of 6LN. 550 Padding: 552 A variable-length field making the option length a multiple of 8, 553 containing as many octets as specified in the Pad Length field. 555 4.3. Multihop Operation 557 In multihop 6LoWPAN, 6LBR sends RAs with prefixes downstream and it 558 is the 6LR that receives and relays them to the nodes. 6LR and 6LBR 559 communicate with the ICMPv6 Duplicate Address Request (DAR) and the 560 Duplicate Address Confirmation (DAC) messages. The DAR and DAC use 561 the same message format as NS and NA with different ICMPv6 type 562 values. 564 In ND-PAR we extend DAR/DAC messages to carry cryptographically 565 generated UID. In a multihop 6LoWPAN, the node exchanges the 566 messages shown in Figure 2. The 6LBR must be aware of who owns an 567 address (EUI-64) to defend the first node if there is an attacker on 568 another 6LR. Because of this the content that the source signs and 569 the signature needs to be propagated to the 6LBR in DAR message. For 570 this purpose the DAR message sent by 6LR to 6LBR MUST contain CGA 571 Parameters and Digital Signature Option carrying the CGA that the 572 node calculates and its public key. DAR message also contains ARO. 574 It is possible that occasionally, 6LR may miss the node's UID (that 575 it received in ARO). 6LR should be able to ask for it again. This is 576 done by restarting the exchanges shown in Figure 3. The result 577 enables 6LR to refresh the information that was lost. 6LR MUST send 578 DAR message with ARO to 6LBR. 6LBR as a reply forms a DAC message 579 with the information copied from the DAR and the Status field is set 580 to zero. With this exchange, the 6LBR can (re)validate and store the 581 information to make sure that the 6LR is not a fake. 583 In some cases 6LBR may use DAC message to signal to 6LR that it 584 expects Crypto-ID from 6LR also asks 6LR to verify the EUI-64 6LR 585 received from 6LN. This may happen when a 6LN node is compromised 586 and a fake node is sending the Crypto-ID as if it is the node's EUI- 587 64. Note that the detection in this case can only be done by 6LBR 588 not by 6LR. 590 5. Security Considerations 592 The same considerations regarding the threats to the Local Link 593 Network covered in [RFC3971] apply. 595 The threats discussed in Section 9.2 of [RFC3971] are countered by 596 the protocol described in this document as well. 598 Collisions of Crypto-ID is a possibility that needs to be considered. 599 The formula for calculating probability of a collision is 1 - 600 e^{-k^2/(2n)}. If the Crypto-ID is 64-bit long, then the chance of 601 finding a collision is 0.01% when the network contains 66 million 602 nodes. It is important to note that the collision is only relevant 603 when this happens within one stub network (6LBR). A collision of ID 604 in ND-PAR is a rare event. However, when such a collision does 605 happen, the protocol operation is not affected, although it opens a 606 window for a node to hijack an address from another. The link-layer 607 security ensures that the nodes would normally not be aware of a 608 collision on the subnet. If a malicious node is able to gain 609 knowledge of a collision through other means, the only thing that it 610 could do is to steal addresses from the other honest node. This 611 would be no different from what is already possible in a 6lo network 612 today. 614 6. IANA considerations 616 IANA is requested to assign two new option type values, TBA1 and TBA2 617 under the subregistry "IPv6 Neighbor Discovery Option Formats". 619 7. Acknowledgements 621 We are grateful to Rene Struik and Robert Moskowitz for their 622 comments that lead to many improvements to this document. 624 8. Change Log 626 o submitted version -00 as a working group draft after adoption, and 627 corrected the order of authors 629 o submitted version -01 with no changes 631 9. References 633 9.1. Normative References 635 [RFC2119] Bradner, S., "Key words for use in RFCs to Indicate 636 Requirement Levels", BCP 14, RFC 2119, 637 DOI 10.17487/RFC2119, March 1997, 638 . 640 [RFC3971] Arkko, J., Ed., Kempf, J., Zill, B., and P. Nikander, 641 "SEcure Neighbor Discovery (SEND)", RFC 3971, 642 DOI 10.17487/RFC3971, March 2005, 643 . 645 [RFC3972] Aura, T., "Cryptographically Generated Addresses (CGA)", 646 RFC 3972, DOI 10.17487/RFC3972, March 2005, 647 . 649 [RFC4291] Hinden, R. and S. Deering, "IP Version 6 Addressing 650 Architecture", RFC 4291, DOI 10.17487/RFC4291, February 651 2006, . 653 [RFC4861] Narten, T., Nordmark, E., Simpson, W., and H. Soliman, 654 "Neighbor Discovery for IP version 6 (IPv6)", RFC 4861, 655 DOI 10.17487/RFC4861, September 2007, 656 . 658 [RFC4862] Thomson, S., Narten, T., and T. Jinmei, "IPv6 Stateless 659 Address Autoconfiguration", RFC 4862, 660 DOI 10.17487/RFC4862, September 2007, 661 . 663 [RFC4903] Thaler, D., "Multi-Link Subnet Issues", RFC 4903, 664 DOI 10.17487/RFC4903, June 2007, 665 . 667 [RFC4919] Kushalnagar, N., Montenegro, G., and C. Schumacher, "IPv6 668 over Low-Power Wireless Personal Area Networks (6LoWPANs): 669 Overview, Assumptions, Problem Statement, and Goals", 670 RFC 4919, DOI 10.17487/RFC4919, August 2007, 671 . 673 [RFC5889] Baccelli, E., Ed. and M. Townsley, Ed., "IP Addressing 674 Model in Ad Hoc Networks", RFC 5889, DOI 10.17487/RFC5889, 675 September 2010, . 677 [RFC6234] Eastlake 3rd, D. and T. Hansen, "US Secure Hash Algorithms 678 (SHA and SHA-based HMAC and HKDF)", RFC 6234, 679 DOI 10.17487/RFC6234, May 2011, 680 . 682 [RFC6550] Winter, T., Ed., Thubert, P., Ed., Brandt, A., Hui, J., 683 Kelsey, R., Levis, P., Pister, K., Struik, R., Vasseur, 684 JP., and R. Alexander, "RPL: IPv6 Routing Protocol for 685 Low-Power and Lossy Networks", RFC 6550, 686 DOI 10.17487/RFC6550, March 2012, 687 . 689 [RFC6775] Shelby, Z., Ed., Chakrabarti, S., Nordmark, E., and C. 690 Bormann, "Neighbor Discovery Optimization for IPv6 over 691 Low-Power Wireless Personal Area Networks (6LoWPANs)", 692 RFC 6775, DOI 10.17487/RFC6775, November 2012, 693 . 695 [RFC7102] Vasseur, JP., "Terms Used in Routing for Low-Power and 696 Lossy Networks", RFC 7102, DOI 10.17487/RFC7102, January 697 2014, . 699 [RFC7039] Wu, J., Bi, J., Bagnulo, M., Baker, F., and C. Vogt, Ed., 700 "Source Address Validation Improvement (SAVI) Framework", 701 RFC 7039, DOI 10.17487/RFC7039, October 2013, 702 . 704 [RFC7217] Gont, F., "A Method for Generating Semantically Opaque 705 Interface Identifiers with IPv6 Stateless Address 706 Autoconfiguration (SLAAC)", RFC 7217, 707 DOI 10.17487/RFC7217, April 2014, 708 . 710 [RFC7696] Housley, R., "Guidelines for Cryptographic Algorithm 711 Agility and Selecting Mandatory-to-Implement Algorithms", 712 BCP 201, RFC 7696, DOI 10.17487/RFC7696, November 2015, 713 . 715 [RFC7748] Langley, A., Hamburg, M., and S. Turner, "Elliptic Curves 716 for Security", RFC 7748, DOI 10.17487/RFC7748, January 717 2016, . 719 9.2. Informative references 721 [I-D.ietf-6lo-backbone-router] 722 Thubert, P., "IPv6 Backbone Router", draft-ietf-6lo- 723 backbone-router-03 (work in progress), January 2017. 725 [I-D.ietf-6tisch-architecture] 726 Thubert, P., "An Architecture for IPv6 over the TSCH mode 727 of IEEE 802.15.4", draft-ietf-6tisch-architecture-11 (work 728 in progress), January 2017. 730 [I-D.ietf-6man-ipv6-address-generation-privacy] 731 Cooper, A., Gont, F., and D. Thaler, "Privacy 732 Considerations for IPv6 Address Generation Mechanisms", 733 draft-ietf-6man-ipv6-address-generation-privacy-08 (work 734 in progress), September 2015. 736 Authors' Addresses 738 Behcet Sarikaya (editor) 739 Huawei USA 740 5340 Legacy Dr. Building 3 741 Plano, TX 75024 743 Email: sarikaya@ieee.org 745 Pascal Thubert 746 Cisco Systems, Inc 747 Building D 748 45 Allee des Ormes - BP1200 749 MOUGINS - Sophia Antipolis 06254 750 FRANCE 752 Phone: +33 497 23 26 34 753 Email: pthubert@cisco.com 755 Mohit Sethi (editor) 756 Ericsson 757 Hirsalantie 758 Jorvas 02420 760 Email: mohit@piuha.net