idnits 2.17.00 (12 Aug 2021) /tmp/idnits17336/draft-ietf-6lo-ap-nd-23.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 RFC8505, but the abstract doesn't seem to directly say this. It does mention RFC8505 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 (30 April 2020) is 744 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 6234 ** Downref: Normative reference to an Informational RFC: RFC 7748 ** Downref: Normative reference to an Informational RFC: RFC 8032 -- Possible downref: Non-RFC (?) normative reference: ref. 'FIPS186-4' -- Possible downref: Non-RFC (?) normative reference: ref. 'SEC1' == Outdated reference: draft-ietf-6lo-backbone-router has been published as RFC 8929 == Outdated reference: A later version (-23) exists of draft-ietf-lwig-curve-representations-09 Summary: 3 errors (**), 0 flaws (~~), 3 warnings (==), 4 comments (--). Run idnits with the --verbose option for more detailed information about the items above. -------------------------------------------------------------------------------- 2 6lo P. Thubert, Ed. 3 Internet-Draft Cisco 4 Updates: 8505 (if approved) B. Sarikaya 5 Intended status: Standards Track 6 Expires: 1 November 2020 M. Sethi 7 Ericsson 8 R. Struik 9 Struik Security Consultancy 10 30 April 2020 12 Address Protected Neighbor Discovery for Low-power and Lossy Networks 13 draft-ietf-6lo-ap-nd-23 15 Abstract 17 This document updates the 6LoWPAN Neighbor Discovery (ND) protocol 18 defined in RFC 6775 and RFC 8505. The new extension is called 19 Address Protected Neighbor Discovery (AP-ND) and it protects the 20 owner of an address against address theft and impersonation attacks 21 in a low-power and lossy network (LLN). Nodes supporting this 22 extension compute a cryptographic identifier (Crypto-ID) and use it 23 with one or more of their Registered Addresses. The Crypto-ID 24 identifies the owner of the Registered Address and can be used to 25 provide proof of ownership of the Registered Addresses. Once an 26 address is registered with the Crypto-ID and a proof-of-ownership is 27 provided, only the owner of that address can modify the registration 28 information, thereby enforcing Source Address Validation. 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 https://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 1 November 2020. 47 Copyright Notice 49 Copyright (c) 2020 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 (https://trustee.ietf.org/ 54 license-info) in effect on the date of publication of this document. 55 Please review these documents carefully, as they describe your rights 56 and restrictions with respect to this document. Code Components 57 extracted from this document must include Simplified BSD License text 58 as described in Section 4.e of the Trust Legal Provisions and are 59 provided without warranty as described in the Simplified BSD License. 61 Table of Contents 63 1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . 3 64 2. Terminology . . . . . . . . . . . . . . . . . . . . . . . . . 4 65 2.1. BCP 14 . . . . . . . . . . . . . . . . . . . . . . . . . 4 66 2.2. Additional References . . . . . . . . . . . . . . . . . . 4 67 2.3. Abbreviations . . . . . . . . . . . . . . . . . . . . . . 5 68 3. Updating RFC 8505 . . . . . . . . . . . . . . . . . . . . . . 5 69 4. New Fields and Options . . . . . . . . . . . . . . . . . . . 6 70 4.1. New Crypto-ID . . . . . . . . . . . . . . . . . . . . . . 6 71 4.2. Updated EARO . . . . . . . . . . . . . . . . . . . . . . 7 72 4.3. Crypto-ID Parameters Option . . . . . . . . . . . . . . . 8 73 4.4. NDP Signature Option . . . . . . . . . . . . . . . . . . 10 74 4.5. Extensions to the Capability Indication Option . . . . . 11 75 5. Protocol Scope . . . . . . . . . . . . . . . . . . . . . . . 12 76 6. Protocol Flows . . . . . . . . . . . . . . . . . . . . . . . 13 77 6.1. First Exchange with a 6LR . . . . . . . . . . . . . . . . 14 78 6.2. NDPSO generation and verification . . . . . . . . . . . . 16 79 6.3. Multihop Operation . . . . . . . . . . . . . . . . . . . 17 80 7. Security Considerations . . . . . . . . . . . . . . . . . . . 18 81 7.1. Brown Field . . . . . . . . . . . . . . . . . . . . . . . 18 82 7.2. Inheriting from RFC 3971 . . . . . . . . . . . . . . . . 18 83 7.3. Related to 6LoWPAN ND . . . . . . . . . . . . . . . . . . 19 84 7.4. Compromised 6LR . . . . . . . . . . . . . . . . . . . . . 20 85 7.5. ROVR Collisions . . . . . . . . . . . . . . . . . . . . . 20 86 7.6. Implementation Attacks . . . . . . . . . . . . . . . . . 21 87 7.7. Cross-Algorithm and Cross-Protocol Attacks . . . . . . . 21 88 7.8. Public Key Validation . . . . . . . . . . . . . . . . . . 22 89 7.9. Correlating Registrations . . . . . . . . . . . . . . . . 22 90 8. IANA considerations . . . . . . . . . . . . . . . . . . . . . 22 91 8.1. CGA Message Type . . . . . . . . . . . . . . . . . . . . 22 92 8.2. Crypto-Type Subregistry . . . . . . . . . . . . . . . . . 23 93 8.3. IPv6 ND option types . . . . . . . . . . . . . . . . . . 24 94 8.4. New 6LoWPAN Capability Bit . . . . . . . . . . . . . . . 24 96 9. Acknowledgments . . . . . . . . . . . . . . . . . . . . . . . 24 97 10. Normative References . . . . . . . . . . . . . . . . . . . . 24 98 11. Informative references . . . . . . . . . . . . . . . . . . . 26 99 Appendix A. Requirements Addressed in this Document . . . . . . 28 100 Appendix B. Representation Conventions . . . . . . . . . . . . . 28 101 B.1. Signature Schemes . . . . . . . . . . . . . . . . . . . . 28 102 B.2. Representation of ECDSA Signatures . . . . . . . . . . . 29 103 B.3. Representation of Public Keys Used with ECDSA . . . . . . 30 104 B.4. Alternative Representations of Curve25519 . . . . . . . . 30 105 Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . 32 107 1. Introduction 109 Neighbor Discovery Optimizations for 6LoWPAN networks [RFC6775] 110 (6LoWPAN ND) adapts the original IPv6 Neighbor Discovery (IPv6 ND) 111 protocols defined in [RFC4861] and [RFC4862] for constrained low- 112 power and lossy network (LLN). In particular, 6LoWPAN ND introduces 113 a unicast host Address Registration mechanism that reduces the use of 114 multicast compared to the Duplicate Address Detection (DAD) mechanism 115 defined in IPv6 ND. 6LoWPAN ND defines a new Address Registration 116 Option (ARO) that is carried in the unicast Neighbor Solicitation 117 (NS) and Neighbor Advertisement (NA) messages exchanged between a 118 6LoWPAN Node (6LN) and a 6LoWPAN Router (6LR). It also defines the 119 Duplicate Address Request (DAR) and Duplicate Address Confirmation 120 (DAC) messages between the 6LR and the 6LoWPAN Border Router (6LBR). 121 In LLN networks, the 6LBR is the central repository of all the 122 registered addresses in its domain. 124 The registration mechanism in "Neighbor Discovery Optimization for 125 Low-power and Lossy Networks" [RFC6775] (aka 6LoWPAN ND) prevents the 126 use of an address if that address is already registered in the subnet 127 (first come first serve). In order to validate address ownership, 128 the registration mechanism enables the 6LR and 6LBR to validate the 129 association between the registered address of a node, and its 130 Registration Ownership Verifier (ROVR). The ROVR is defined in 131 "Registration Extensions for 6LoWPAN Neighbor Discovery" [RFC8505] 132 and it can be derived from the MAC address of the device (using the 133 64-bit Extended Unique Identifier EUI-64 address format specified by 134 IEEE). However, the EUI-64 can be spoofed, and therefore, any node 135 connected to the subnet and aware of a registered-address-to-ROVR 136 mapping could effectively fake the ROVR. This would allow an 137 attacker to steal the address and redirect traffic for that address. 138 [RFC8505] defines an Extended Address Registration Option (EARO) 139 option that transports alternate forms of ROVRs, and is a pre- 140 requisite for this specification. 142 In this specification, a 6LN generates a cryptographic ID (Crypto-ID) 143 and places it in the ROVR field during the registration of one (or 144 more) of its addresses with the 6LR(s). Proof of ownership of the 145 Crypto-ID is passed with the first registration exchange to a new 146 6LR, and enforced at the 6LR. The 6LR validates ownership of the 147 cryptographic ID before it creates any new registration state, or 148 changes existing information. 150 The protected address registration protocol proposed in this document 151 provides the same conceptual benefit as Source Address Validation 152 (SAVI) [RFC7039] that only the owner of an IPv6 address may source 153 packets with that address. As opposed to [RFC7039], which relies on 154 snooping protocols, the protection is based on a state that is 155 installed and maintained in the network by the owner of the address. 156 With this specification, a 6LN may use a 6LR for forwarding an IPv6 157 packets if and only if it has registered the address used as source 158 of the packet with that 6LR. 160 With the 6lo adaptation layer in [RFC4944] and [RFC6282], a 6LN can 161 obtain a better compression for an IPv6 address with an Interface ID 162 (IID) that is derived from a Layer-2 address. As a side note, this 163 is incompatible with Secure Neighbor Discovery (SeND) [RFC3971] and 164 Cryptographically Generated Addresses (CGAs) [RFC3972], since they 165 derive the IID from cryptographic keys, whereas this specification 166 separates the IID and the key material. 168 2. Terminology 170 2.1. BCP 14 172 The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT", 173 "SHOULD", "SHOULD NOT", "RECOMMENDED", "NOT RECOMMENDED", "MAY", and 174 "OPTIONAL" in this document are to be interpreted as described in BCP 175 14 [RFC2119] [RFC8174] when, and only when, they appear in all 176 capitals, as shown here. 178 2.2. Additional References 180 The reader may get additional context for this specification from the 181 following references: 183 * "SEcure Neighbor Discovery (SEND)" [RFC3971], 184 * "Cryptographically Generated Addresses (CGA)" [RFC3972], 185 * "Neighbor Discovery for IP version 6" [RFC4861] , 186 * "IPv6 Stateless Address Autoconfiguration" [RFC4862], and 187 * "IPv6 over Low-Power Wireless Personal Area Networks (6LoWPANs): 188 Overview, Assumptions, Problem Statement, and Goals " [RFC4919]. 190 2.3. Abbreviations 192 This document uses the following abbreviations: 194 6BBR: 6LoWPAN Backbone Router 195 6LBR: 6LoWPAN Border Router 196 6LN: 6LoWPAN Node 197 6LR: 6LoWPAN Router 198 CGA: Cryptographically Generated Address 199 EARO: Extended Address Registration Option 200 ECDH: Elliptic curve Diffie-Hellman 201 ECDSA: Elliptic Curve Digital Signature Algorithm 202 CIPO: Crypto-ID Parameters Option 203 LLN: Low-Power and Lossy Network 204 JSON: JavaScript Object Notation 205 JOSE: JavaScript Object Signing and Encryption 206 JWK: JSON Web Key 207 JWS: JSON Web Signature 208 NA: Neighbor Advertisement 209 ND: Neighbor Discovery 210 NDP: Neighbor Discovery Protocol 211 NDPSO: Neighbor Discovery Protocol Signature Option 212 NS: Neighbor Solicitation 213 ROVR: Registration Ownership Verifier 214 RA: Router Advertisement 215 RS: Router Solicitation 216 RSAO: RSA Signature Option 217 SHA: Secure Hash Algorithm 218 SLAAC: Stateless Address Autoconfiguration 219 TID: Transaction ID 221 3. Updating RFC 8505 223 Section 5.3 of [RFC8505] introduces the ROVR that is used to detect 224 and reject duplicate registrations in the DAD process. The ROVR is a 225 generic object that is designed for both backward compatibility and 226 the capability to introduce new computation methods in the future. 227 Using a Crypto-ID per this specification is the RECOMMENDED method. 228 Section 7.5 discusses collisions when heterogeneous methods to 229 compute the ROVR field coexist inside a same network. 231 This specification introduces a new token called a cryptographic 232 identifier (Crypto-ID) that is transported in the ROVR field and used 233 to prove indirectly the ownership of an address that is being 234 registered by means of [RFC8505]. The Crypto-ID is derived from a 235 cryptographic public key and additional parameters. 237 The overall mechanism requires the support of Elliptic Curve 238 Cryptography (ECC) and of a hash function as detailed in Section 6.2. 239 To enable the verification of the proof, the registering node needs 240 to supply certain parameters including a nonce and a signature that 241 will demonstrate that the node possesses the private-key 242 corresponding to the public-key used to build the Crypto-ID. 244 The elliptic curves and the hash functions listed in Table 1 in 245 Section 8.2 can be used with this specification; more may be added in 246 the future to the IANA registry. The signature scheme that specifies 247 which combination is used (including the curve and the representation 248 conventions) is signaled by a Crypto-Type in a new IPv6 ND Crypto-ID 249 Parameters Option (CIPO, see Section 4.3) that contains the 250 parameters that are necessary for the proof, a Nonce option 251 ([RFC3971]) and a NDP Signature option (Section 4.4). The NA(EARO) 252 is modified to enable a challenge and transport a Nonce option. 254 4. New Fields and Options 256 4.1. New Crypto-ID 258 The Crypto-ID is transported in the ROVR field of the EARO option and 259 the EDAR message, and is associated with the Registered Address at 260 the 6LR and the 6LBR. The ownership of a Crypto-ID can be 261 demonstrated by cryptographic mechanisms, and by association, the 262 ownership of the Registered Address can be ascertained. 264 A node in possession of the necessary cryptographic primitives SHOULD 265 use Crypto-ID by default as ROVR in its registrations. Whether a 266 ROVR is a Crypto-ID is indicated by a new "C" flag in the NS(EARO) 267 message. 269 The Crypto-ID is derived from the public key and a modifier as 270 follows: 272 1. The hash function used internally by the signature scheme 273 indicated by the Crypto-Type (see also Table 1 in Section 8.2) is 274 applied to the CIPO. Note that all the reserved and padding bits 275 MUST be set to zero. 276 2. The leftmost bits of the resulting hash, up to the desired size, 277 are used as the Crypto-ID. 279 At the time of this writing, a minimal size for the Crypto-ID of 128 280 bits is RECOMMENDED unless backward compatibility is needed 281 [RFC8505]. This value is bound to augment in the future. 283 4.2. Updated EARO 285 This specification updates the EARO option to enable the use of the 286 ROVR field to transport the Crypto-ID. The resulting format is as 287 follows: 289 0 1 2 3 290 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 1 291 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 292 | Type | Length | Status | Opaque | 293 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 294 |Rsvd |C| I |R|T| TID | Registration Lifetime | 295 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 296 | | 297 ... Registration Ownership Verifier (ROVR) ... 298 | | 299 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 301 Figure 1: Enhanced Address Registration Option 303 Type: 33 305 Length: Defined in [RFC8505] and copied in associated CIPO. 307 Status: Defined in [RFC8505]. 309 Opaque: Defined in [RFC8505]. 311 Rsvd (Reserved): 3-bit unsigned integer. It MUST be set to zero by 312 the sender and MUST be ignored by the receiver. 314 C: This "C" flag is set to indicate that the ROVR field contains a 315 Crypto-ID and that the 6LN MAY be challenged for ownership as 316 specified in this document. 318 I, R, T: Defined in [RFC8505]. 320 TID: Defined in [RFC8505]. 322 Registration Ownership Verifier (ROVR): When the "C" flag is set, 323 this field contains a Crypto-ID. 325 This specification uses Status values "Validation Requested" and 326 "Validation Failed", which are defined in [RFC8505]. 328 this specification does not define any new Status value. 330 4.3. Crypto-ID Parameters Option 332 This specification defines the Crypto-ID Parameters Option (CIPO). 333 The CIPO carries the parameters used to form a Crypto-ID. 335 In order to provide cryptographic agility [BCP 201], this 336 specification supports different elliptic-curve based signature 337 schemes, indicated by a Crypto-Type field: 339 * The ECDSA256 signature scheme, which uses ECDSA with the NIST 340 P-256 curve [FIPS186-4] and the hash function SHA-256 [RFC6234] 341 internally, MUST be supported by all implementations. 343 * The Ed25519 signature scheme, which uses the Pure Edwards-Curve 344 Digital Signature Algorithm (PureEdDSA) [RFC8032] with the twisted 345 Edwards curve Edwards25519 [RFC7748] and the hash function SHA-512 346 [RFC6234] internally, MAY be supported as an alternative. 348 * The ECDSA25519 signature scheme, which uses ECDSA [FIPS186-4] with 349 the Weierstrass curve Wei25519 (see Appendix B.4) and the hash 350 function SHA-256 [RFC6234] internally, MAY also be supported. 352 This specification uses signature schemes that target similar 353 cryptographic strength but rely on different curves, hash functions, 354 signature algorithms, and/or representation conventions. Future 355 specification may extend this to different cryptographic algorithms 356 and key sizes, e.g., to provide better security properties or a 357 simpler implementation. 359 0 1 2 3 360 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 1 361 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 362 | Type | Length |Reserved1| Public Key Length | 363 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 364 | Crypto-Type | Modifier | EARO Length | | 365 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ + 366 | | 367 . . 368 . Public Key (variable length) . 369 . . 370 | | 371 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 372 | | 373 . Padding . 374 | | 375 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 377 Figure 2: Crypto-ID Parameters Option 379 Type: 8-bit unsigned integer. to be assigned by IANA, see Table 2. 381 Length: 8-bit unsigned integer. The length of the option in units 382 of 8 octets. 384 Reserved1: 5-bit unsigned integer. It MUST be set to zero by the 385 sender and MUST be ignored by the receiver. 387 Public Key Length: 11-bit unsigned integer. The length of the 388 Public Key field in bytes. The actual length depends on the 389 Crypto-Type value and on how the public key is represented. The 390 valid values with this document are provided in Table 1. 392 Crypto-Type: 8-bit unsigned integer. The type of cryptographic 393 algorithm used in calculation Crypto-ID indexed by IANA in the 394 "Crypto-Type Subregistry" in the "Internet Control Message 395 Protocol version 6 (ICMPv6) Parameters" (see Section 8.2). 397 Modifier: 8-bit unsigned integer. Set to an arbitrary value by the 398 creator of the Crypto-ID. The role of the modifier is to enable 399 the formation of multiple Crypto-IDs from a same key pair, which 400 reduces the traceability and thus improves the privacy of a 401 constrained node that could not maintain many key-pairs. 403 EARO Length: 8-bit unsigned integer. The option length of the EARO 404 that contains the Crypto-ID associated with the CIPO. 406 Public Key: A variable-length field, size indicated in the Public 407 Key Length field. 409 Padding: A variable-length field completing the Public Key field to 410 align to the next 8-bytes boundary. It MUST be set to zero by the 411 sender and MUST be ignored by the receiver. 413 The implementation of multiple hash functions in a constrained device 414 may consume excessive amounts of program memory. This specification 415 enables the use of the same hash function SHA-256 [RFC6234] for two 416 of the three supported ECC-based signature schemes. Some code 417 factorization is also possible for the ECC computation itself. 419 [CURVE-REPR] provides information on how to represent Montgomery 420 curves and (twisted) Edwards curves as curves in short-Weierstrass 421 form and illustrates how this can be used to implement elliptic curve 422 computations using existing implementations that already provide, 423 e.g., ECDSA and ECDH using NIST [FIPS186-4] prime curves. For more 424 details on representation conventions, we refer to Appendix B. 426 4.4. NDP Signature Option 428 This specification defines the NDP Signature Option (NDPSO). The 429 NDPSO carries the signature that proves the ownership of the Crypto- 430 ID. The format of the NDPSO is illustrated in Figure 3. 432 As opposed to the RSA Signature Option (RSAO) defined in section 5.2. 433 of SEND [RFC3971], the NDPSO does not have a key hash field. 434 Instead, the leftmost 128 bits of the ROVR field in the EARO are used 435 as hash to retrieve the CIPO that contains the key material used for 436 signature verification, left-padded if needed. 438 Another difference is that the NDPSO signs a fixed set of fields as 439 opposed to all options that appear prior to it in the ND message that 440 bears the signature. This allows to elide a CIPO that the 6LR 441 already received, at the expense of the capability to add arbitrary 442 options that would signed with a RSAO. 444 An ND message that carries an NDPSO MUST have one and only one EARO. 445 The EARO MUST contain a Crypto-ID in the ROVR field, and the Crypto- 446 ID MUST be associated with the keypair used for the Digital Signature 447 in the NDPSO. 449 The CIPO may be present in the same message as the NDPSO. If it is 450 not present, it can be found in an abstract table that was created by 451 a previous message and indexed by the hash. 453 0 1 2 3 454 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 1 455 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 456 | Type | Length |Reserved1| Signature Length | 457 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 458 | Reserved2 | 459 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 460 | | 461 . . 462 . Digital Signature (variable length) . 463 . . 464 | | 465 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 466 | | 467 . Padding . 468 | | 469 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 471 Figure 3: NDP signature Option 473 Type: to be assigned by IANA, see Table 2. 475 Length: 8-bit unsigned integer. The length of the option in units 476 of 8 octets. 478 Reserved1: 5-bit unsigned integer. It MUST be set to zero by the 479 sender and MUST be ignored by the receiver. 481 Digital Signature Length: 11-bit unsigned integer. The length of 482 the Digital Signature field in bytes. 484 Reserved2: 32-bit unsigned integer. It MUST be set to zero by the 485 sender and MUST be ignored by the receiver. 487 Digital Signature: A variable-length field containing the digital 488 signature. The length and computation of the digital signature 489 both depend on the Crypto-Type which is found in the associated 490 CIPO, see Appendix B. For the values of the Crypto-Type defined 491 in this specification, and for future values of the Crypto-Type 492 unless specified otherwise, the signature is computed as detailed 493 in Section 6.2. 495 Padding: A variable-length field completing the Digital Signature 496 field to align to the next 8-bytes boundary. It MUST be set to 497 zero by the sender and MUST be ignored by the receiver. 499 4.5. Extensions to the Capability Indication Option 501 This specification defines one new capability bits in the 6CIO, 502 defined by [RFC7400] for use by the 6LR and 6LBR in IPv6 ND RA 503 messages. 505 0 1 2 3 506 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 1 507 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 508 | Type | Length = 1 | Reserved |A|D|L|B|P|E|G| 509 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 510 | Reserved | 511 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 513 Figure 4: New Capability Bit in the 6CIO 515 New Option Field: 517 A: 1-bit flag. Set to indicate that AP-ND is globally activated in 518 the network. 520 The "A" flag is set by the 6LBR that serves the network and 521 propagated by the 6LRs. It is typically turned on when all 6LRs are 522 migrated to this specification. 524 5. Protocol Scope 526 The scope of the protocol specified here is a 6LoWPAN LLN, typically 527 a stub network connected to a larger IP network via a Border Router 528 called a 6LBR per [RFC6775]. A 6LBR has sufficient capability to 529 satisfy the needs of duplicate address detection. 531 The 6LBR maintains registration state for all devices in its attached 532 LLN. Together with the first-hop router (the 6LR), the 6LBR assures 533 uniqueness and grants ownership of an IPv6 address before it can be 534 used in the LLN. This is in contrast to a traditional network that 535 relies on IPv6 address auto-configuration [RFC4862], where there is 536 no guarantee of ownership from the network, and each IPv6 Neighbor 537 Discovery packet must be individually secured [RFC3971]. 539 ---+-------- ............ 540 | External Network 541 | 542 +-----+ 543 | | 6LBR 544 +-----+ 545 o o o 546 o o o o 547 o o LLN o o o 548 o o 549 o o o(6LR) 550 ^ 551 o o | LLN link 552 o o v 553 o(6LN) 554 o 556 Figure 5: Basic Configuration 558 In a mesh network, the 6LR is directly connected to the host device. 559 This specification mandates that the peer-wise layer-2 security is 560 deployed so that all the packets from a particular host are securely 561 identifiable by the 6LR. The 6LR may be multiple hops away from the 562 6LBR. Packets are routed between the 6LR and the 6LBR via other 563 6LRs. 565 This specification mandates that all the LLN links between the 6LR 566 and the 6LBR are protected so that a packet that was validated by the 567 first 6LR can be safely routed by other on-path 6LRs to the 6LBR. 569 6. Protocol Flows 571 The 6LR/6LBR ensures first-come/first-serve by storing the ROVR 572 associated to the address being registered upon the first 573 registration and rejecting a registration with a different ROVR 574 value. A 6LN can claim any address as long as it is the first to 575 make that claim. After a successful registration, the 6LN becomes 576 the owner of the registered address and the address is bound to the 577 ROVR value in the 6LR/6LBR registry. 579 This specification protects the ownership of the address at the first 580 hop (the edge). Its use in a network is signaled by the "A" flag in 581 the 6CIO. The flag is set by the 6LBR and propagated unchanged by 582 the 6LRs. The "A" flag enables to migrate a network with the 583 protection off and then turn it on globally. 585 The 6LN places a cryptographic token, the Crypto-ID, in the ROVR that 586 is associated with the address at the first registration, enabling 587 the 6LR to later challenge it to verify that it is the original 588 Registering Node. The challenge may happen at any time at the 589 discretion of the 6LR and the 6LBR. A valid registration in the 6LR 590 or the 6LBR MUST NOT be altered until the challenge is complete. 592 When the "A" flag is on, the 6LR MUST challenge the 6LN when it 593 creates a binding with the "C" flag set in the ROVR and when a new 594 registration attempts to change a parameter of that binding that 595 identifies the 6LN, for instance its Source Link-Layer Address. The 596 verification protects against a rogue that would steal an address and 597 attract its traffic, or use it as source address. 599 The 6LR MUST also challenge the 6LN if the 6LBR directly signals to 600 do so, using an EDAC Message with a "Validation Requested" status. 601 The EDAR is echoed by the 6LR in the NA (EARO) back to the 602 registering node. The 6LR SHOULD also challenge all its attached 603 6LNs at the time the 6LBR turns the "A" flag on in the 6CIO, to 604 detect an issue immediately. 606 If the 6LR does not support the Crypto-Type, it MUST reply with an 607 EARO Status 10 "Validation Failed" without a challenge. In that 608 case, the 6LN may try another Crypto-Type until it falls back to 609 Crypto-Type 0 that MUST be supported by all 6LRs. 611 A node may use more than one IPv6 address at the same time. The 612 separation of the address and the cryptographic material avoids the 613 need for the constrained device to compute multiple keys for multiple 614 addresses. The 6LN MAY use the same Crypto-ID to prove the ownership 615 of multiple IPv6 addresses. The 6LN MAY also derive multiple Crypto- 616 IDs from a same key. 618 6.1. First Exchange with a 6LR 620 A 6LN registers to a 6LR that is one hop away from it with the "C" 621 flag set in the EARO, indicating that the ROVR field contains a 622 Crypto-ID. The Target Address in the NS message indicates the IPv6 623 address that the 6LN is trying to register [RFC8505]. The on-link 624 (local) protocol interactions are shown in Figure 6. If the 6LR does 625 not have a state with the 6LN that is consistent with the NS(EARO), 626 then it replies with a challenge NA (EARO, status=Validation 627 Requested) that contains a Nonce Option (shown as NonceLR in 628 Figure 6). 630 6LN 6LR 631 | | 632 |<------------------------- RA -------------------------| 633 | | ^ 634 |---------------- NS with EARO (Crypto-ID) ------------>| | 635 | | option 636 |<- NA with EARO(status=Validation Requested), NonceLR | | 637 | | v 638 |------- NS with EARO, CIPO, NonceLN and NDPSO -------->| 639 | | 640 |<------------------- NA with EARO ---------------------| 641 | | 642 ... 643 | | 644 |--------------- NS with EARO (Crypto-ID) ------------->| 645 | | 646 |<------------------- NA with EARO ---------------------| 647 | | 648 ... 649 | | 650 |--------------- NS with EARO (Crypto-ID) ------------->| 651 | | 652 |<------------------- NA with EARO ---------------------| 653 | | 655 Figure 6: On-link Protocol Operation 657 The Nonce option contains a nonce value that, to the extent possible 658 for the implementation, was never employed in association with the 659 key pair used to generate the Crypto-ID. This specification inherits 660 from [RFC3971] that simply indicates that the nonce is a random 661 value. Ideally, an implementation uses an unpredictable 662 cryptographically random value [BCP 106]. But that may be 663 impractical in some LLN scenarios where the devices do not have a 664 guaranteed sense of time and for which computing complex hashes is 665 detrimental to the battery lifetime. 667 Alternatively, the device may use an always-incrementing value saved 668 in the same stable storage as the key, so they are lost together, and 669 starting at a best effort random value, either as the nonce value or 670 as a component to its computation. 672 The 6LN replies to the challenge with an NS(EARO) that includes a new 673 Nonce option (shown as NonceLN in Figure 6), the CIPO (Section 4.3), 674 and the NDPSO containing the signature. Both Nonces are included in 675 the signed material. This provides a "contributory behavior", so 676 that either party that knows it generates a good quality nonce knows 677 that the protocol will be secure. 679 The 6LR MUST store the information associated to a Crypto-ID on the 680 first NS exchange where it appears in a fashion that the CIPO 681 parameters can be retrieved from the Crypto-ID alone. 683 The steps for the registration to the 6LR are as follows: 685 Upon the first exchange with a 6LR, a 6LN will be challenged to prove 686 ownership of the Crypto-ID and the Target Address being registered in 687 the Neighbor Solicitation message. When a 6LR receives a NS(EARO) 688 registration with a new Crypto-ID as a ROVR, and unless the 689 registration is rejected for another reason, it MUST challenge by 690 responding with a NA(EARO) with a status of "Validation Requested". 692 Upon receiving a first NA(EARO) with a status of "Validation 693 Requested" from a 6LR, the registering node SHOULD retry its 694 registration with a Crypto-ID Parameters Option (CIPO) (Section 4.3) 695 that contains all the necessary material for building the Crypto-ID, 696 the NonceLN that it generated, and the NDP signature (Section 4.4) 697 option that proves its ownership of the Crypto-ID and intent of 698 registering the Target Address. In subsequent revalidation with the 699 same 6LR, the 6LN MAY try to omit the CIPO to save bandwidth, with 700 the expectation that the 6LR saved it. If the validation fails and 701 it gets challenged again, then it SHOULD add the CIPO again. 703 In order to validate the ownership, the 6LR performs the same steps 704 as the 6LN and rebuilds the Crypto-ID based on the parameters in the 705 CIPO. If the rebuilt Crypto-ID matches the ROVR, the 6LN also 706 verifies the signature contained in the NDPSO option. If at that 707 point the signature in the NDPSO option can be verified, then the 708 validation succeeds. Otherwise the validation fails. 710 If the 6LR fails to validate the signed NS(EARO), it responds with a 711 status of "Validation Failed". After receiving a NA(EARO) with a 712 status of "Validation Failed", the registering node SHOULD try and 713 alternate Crypto-Type and if even Crypto-Type 0 fails, it may try to 714 register a different address in the NS message. 716 6.2. NDPSO generation and verification 718 The signature generated by the 6LN to provide proof-of-ownership of 719 the private-key is carried in the NDP Signature Option (NDPSO). It 720 is generated by the 6LN in a fashion that depends on the Crypto-Type 721 (see Table 1 in Section 8.2) chosen by the 6LN as follows: 723 * Form the message to be signed, by concatenating the following 724 byte-strings in the order listed: 726 1. The 128-bit Message Type tag [RFC3972] (in network byte 727 order). For this specification the tag is given in 728 Section 8.1. (The tag value has been generated by the editor 729 of this specification on random.org). 730 2. the CIPO 731 3. the 16-byte Target Address (in network byte order) sent in the 732 Neighbor Solicitation (NS) message. It is the address which 733 the 6LN is registering with the 6LR and 6LBR. 734 4. NonceLR received from the 6LR (in network byte order) in the 735 Neighbor Advertisement (NA) message. The nonce is at least 6 736 bytes long as defined in [RFC3971]. 737 5. NonceLN sent from the 6LN (in network byte order). The nonce 738 is at least 6 bytes long as defined in [RFC3971]. 739 6. 1-byte Option Length of the EARO containing the Crypto-ID. 741 * Apply the signature algorithm specified by the Crypto-Type using 742 the private key. 744 The 6LR on receiving the NDPSO and CIPO options first checks that the 745 EARO Length in the CIPO matches the length of the EARO. If so it 746 regenerates the Crypto-ID based on the CIPO to make sure that the 747 leftmost bits up to the size of the ROVR match. 749 If and only if the check is successful, it tries to verify the 750 signature in the NDPSO option using the following: 752 * Form the message to be verified, by concatenating the following 753 byte-strings in the order listed: 755 1. The 128-bit Message Type tag given in Section 8.1 (in network 756 byte order) 757 2. the CIPO 758 3. the 16-byte Target Address (in network byte order) received in 759 the Neighbor Solicitation (NS) message. It is the address 760 which the 6LN is registering with the 6LR and 6LBR. 761 4. NonceLR sent in the Neighbor Advertisement (NA) message. The 762 nonce is at least 6 bytes long as defined in [RFC3971]. 764 5. NonceLN received from the 6LN (in network byte order) in the 765 NS message. The nonce is at least 6 bytes long as defined in 766 [RFC3971]. 767 6. 1-byte EARO Length received in the CIPO. 769 * Verify the signature on this message with the public-key in the 770 CIPO and the locally computed values using the signature algorithm 771 specified by the Crypto-Type. If the verification succeeds, the 772 6LR propagates the information to the 6LBR using a EDAR/EDAC flow. 774 * Due to the first-come/first-serve nature of the registration, if 775 the address is not registered to the 6LBR, then flow succeeds and 776 both the 6LR and 6LBR add the state information about the Crypto- 777 ID and Target Address being registered to their respective 778 abstract database. 780 6.3. Multihop Operation 782 A new 6LN that joins the network auto-configures an address and 783 performs an initial registration to a neighboring 6LR with an NS 784 message that carries an Address Registration Option (EARO) [RFC8505]. 786 In a multihop 6LoWPAN, the registration with Crypto-ID is propagated 787 to 6LBR as shown in Figure 7, which illustrates the registration flow 788 all the way to a 6LowPAN Backbone Router (6BBR) [BACKBONE-ROUTER]. 790 6LN 6LR 6LBR 6BBR 791 | | | | 792 | NS(EARO) | | | 793 |--------------->| | | 794 | | Extended DAR | | 795 | |-------------->| | 796 | | | proxy NS(EARO) | 797 | | |--------------->| 798 | | | | NS(DAD) 799 | | | | ------> 800 | | | | 801 | | | | 802 | | | | 803 | | | proxy NA(EARO) | 804 | | |<---------------| 805 | | Extended DAC | | 806 | |<--------------| | 807 | NA(EARO) | | | 808 |<---------------| | | 809 | | | | 811 Figure 7: (Re-)Registration Flow 813 The 6LR and the 6LBR communicate using ICMPv6 Extended Duplicate 814 Address Request (EDAR) and Extended Duplicate Address Confirmation 815 (EDAC) messages [RFC8505] as shown in Figure 7. This specification 816 extends EDAR/EDAC messages to carry cryptographically generated ROVR. 818 The assumption is that the 6LR and the 6LBR maintain a security 819 association to authenticate and protect the integrity of the EDAR and 820 EDAC messages, so there is no need to propagate the proof of 821 ownership to the 6LBR. The 6LBR implicitly trusts that the 6LR 822 performs the verification when the 6LBR requires it, and if there is 823 no further exchange from the 6LR to remove the state, that the 824 verification succeeded. 826 7. Security Considerations 828 7.1. Brown Field 830 Only 6LRs that are upgraded to this specification are capable to 831 challenge a registration and repel an attack. In a brown (mixed) 832 network, an attacker may attach to a legacy 6LR and fool the 6LBR. 833 So even if the "A" flag could be set at any time to test the protocol 834 operation, the security will only be effective when all the 6LRs are 835 upgraded. 837 7.2. Inheriting from RFC 3971 839 Observations regarding the following threats to the local network in 840 [RFC3971] also apply to this specification. 842 Neighbor Solicitation/Advertisement Spoofing: Threats in section 843 9.2.1 of RFC3971 apply. AP-ND counters the threats on NS(EARO) 844 messages by requiring that the NDP Signature and CIPO options be 845 present in these solicitations. 847 Duplicate Address Detection DoS Attack: Inside the LLN, Duplicate 848 Addresses are sorted out using the ROVR, which differentiates it 849 from a movement. A different ROVR for the same Registered address 850 entails a rejection of the second registration [RFC8505]. DAD 851 coming from the backbone are not forwarded over the LLN, which 852 provides some protection against DoS attacks inside the resource- 853 constrained part of the network. Over the backbone, the EARO 854 option is present in NS/NA messages. This protects against 855 misinterpreting a movement for a duplication, and enables the 856 backbone routers to determine which one has the freshest 857 registration [RFC8505] and is thus the best candidate to validate 858 the registration for the device attached to it [BACKBONE-ROUTER]. 859 But this specification does not guarantee that the backbone router 860 claiming an address over the backbone is not an attacker. 862 Router Solicitation and Advertisement Attacks: This specification 863 does not change the protection of RS and RA which can still be 864 protected by SEND. 866 Replay Attacks A nonce should never repeat for a single key, but 867 nonces do not need to be unpredictable for secure operation. 868 Using nonces (NonceLR and NonceLN) generated by both the 6LR and 869 6LN ensure a contributory behavior that provides an efficient 870 protection against replay attacks of the challenge/response flow. 871 The quality of the protection by a random nonce depends on the 872 random number generator and its parameters (e.g., sense of time). 874 Neighbor Discovery DoS Attack: A rogue node that managed to access 875 the L2 network may form many addresses and register them using AP- 876 ND. The perimeter of the attack is all the 6LRs in range of the 877 attacker. The 6LR MUST protect itself against overflows and 878 reject excessive registration with a status 2 "Neighbor Cache 879 Full". This effectively blocks another (honest) 6LN from 880 registering to the same 6LR, but the 6LN may register to other 881 6LRs that are in its range but not in that of the rogue. 883 7.3. Related to 6LoWPAN ND 885 The threats and mediations discussed in 6LoWPAN ND [RFC6775][RFC8505] 886 also apply here, in particular denial-of-service attacks against the 887 registry at the 6LR or 6LBR. 889 Secure ND [RFC3971] forces the IPv6 address to be cryptographic since 890 it integrates the CGA as the IID in the IPv6 address. In contrast, 891 this specification saves about 1Kbyte in every NS/NA message. Also, 892 this specification separates the cryptographic identifier from the 893 registered IPv6 address so that a node can have more than one IPv6 894 address protected by the same cryptographic identifier. 896 With this specification the 6LN can freely form its IPv6 address(es) 897 in any fashion, thereby enabling either 6LoWPAN compression for IPv6 898 addresses that are derived from Layer-2 addresses, or temporary 899 addresses, e.g., formed pseudo-randomly and released in relatively 900 short cycles for privacy reasons [RFC8064][RFC8065], that cannot be 901 compressed. 903 This specification provides added protection for addresses that are 904 obtained following due procedure [RFC8505] but does not constrain the 905 way the addresses are formed or the number of addresses that are used 906 in parallel by a same entity. A rogue may still perform denial-of- 907 service attack against the registry at the 6LR or 6LBR, or attempt to 908 deplete the pool of available addresses at Layer-2 or Layer-3. 910 7.4. Compromised 6LR 912 This specification distributes the challenge and its validation at 913 the edge of the network, between the 6LN and its 6LR. This protects 914 against DOS attacks targeted at that central 6LBR. This also saves 915 back and forth exchanges across a potentially large and constrained 916 network. 918 The downside is that the 6LBR needs to trust the 6LR for performing 919 the checking adequately, and the communication between the 6LR and 920 the 6LBR must be protected to avoid tampering with the result of the 921 test. 923 If a 6LR is compromised, and provided that it knows the ROVR field 924 used by the real owner of the address, the 6LR may pretend that the 925 owner has moved, is now attached to it and has successfully passed 926 the Crpto-ID validation. The 6LR may then attract and inject traffic 927 at will on behalf of that address or let a rogue take ownership of 928 the address. 930 7.5. ROVR Collisions 932 A collision of Registration Ownership Verifiers (ROVR) (i.e., the 933 Crypto-ID in this specification) is possible, but it is a rare event. 934 Assuming in the calculations/discussion below that the hash used for 935 calculating the Crypto-ID is a well-behaved cryptographic hash and 936 thus that random collisions are the only ones possible, the formula 937 (birthday paradox) for calculating the probability of a collision is 938 1 - e^{-p^2/(2n)} where n is the maximum population size (2^64 here, 939 1.84E19) and p is the actual population (number of nodes, assuming 940 one Crypto-ID per node). 942 If the Crypto-ID is 64-bits (the least possible size allowed), the 943 chance of a collision is 0.01% for network of 66 million nodes. 944 Moreover, the collision is only relevant when this happens within one 945 stub network (6LBR). In the case of such a collision, a third party 946 node would be able to claim the registered address of an another 947 legitimate node, provided that it wishes to use the same address. To 948 prevent address disclosure and avoid the chances of collision on both 949 the ROVR and the address, it is RECOMMENDED that nodes do not derive 950 the address being registered from the ROVR. 952 7.6. Implementation Attacks 954 The signature schemes referenced in this specification comply with 955 NIST [FIPS186-4] or Crypto Forum Research Group (CFRG) standards 956 [RFC8032] and offer strong algorithmic security at roughly 128-bit 957 security level. These signature schemes use elliptic curves that 958 were either specifically designed with exception-free and constant- 959 time arithmetic in mind [RFC7748] or where one has extensive 960 implementation experience of resistance to timing attacks 961 [FIPS186-4]. 963 However, careless implementations of the signing operations could 964 nevertheless leak information on private keys. For example, there 965 are micro-architectural side channel attacks that implementors should 966 be aware of [breaking-ed25519]. Implementors should be particularly 967 aware that a secure implementation of Ed25519 requires a protected 968 implementation of the hash function SHA-512, whereas this is not 969 required with implementations of the hash function SHA-256 used with 970 ECDSA256 and ECDSA25519. 972 7.7. Cross-Algorithm and Cross-Protocol Attacks 974 The keypair used in this specification can be self-generated and the 975 public key does not need to be exchanged, e.g., through certificates, 976 with a third party before it is used. 978 New keypairs can be formed for new registration as the node desires. 979 On the other hand, it is safer to allocate a keypair that is used 980 only for the address protection and only for one instantiation of the 981 signature scheme (which includes choice of elliptic curve domain 982 parameters, used hash function, and applicable representation 983 conventions). 985 The same private key MUST NOT be reused with more than one 986 instantiation of the signature scheme in this specification. The 987 same private key MUST NOT be used for anything other than computing 988 NDPSO signatures per this specification. 990 ECDSA shall be used strictly as specified in [FIPS186-4]. In 991 particular, each signing operation of ECDSA MUST use randomly 992 generated ephemeral private keys and MUST NOT reuse these ephemeral 993 private keys k accross signing operations. This precludes the use of 994 deterministic ECDSA without a random input for determination of k, 995 which is deemed dangerous for the intended applications this document 996 aims to serve. 998 7.8. Public Key Validation 1000 Public keys contained in the CIPO field (which are used for signature 1001 verification) shall be verified to be correctly formed, by checking 1002 that this public key is indeed a point of the elliptic curve 1003 indicated by the Crypto-Type and that this point does have the proper 1004 order. 1006 For points used with the signature scheme Ed25519, one MUST check 1007 that this point is not a point in the small subgroup (see 1008 Appendix B.1 of [CURVE-REPR]); for points used with the signature 1009 scheme ECDSA (i.e., both ECDSA256 and ECDSA25519), one MUST check 1010 that the point has the same order as the base point of the curve in 1011 question. This is commonly called full public key validation (again, 1012 see Appendix B.1 of [CURVE-REPR]). 1014 7.9. Correlating Registrations 1016 The ROVR field in the EARO introduced in [RFC8505] extends the EUI-64 1017 field of the ARO defined in [RFC6775]. One of the drawbacks of using 1018 an EUI-64 as ROVR is that an attacker that is aware of the 1019 registrations can correlate traffic for a same 6LN across multiple 1020 addresses. Section 3 of [RFC8505] indicates that the ROVR and the 1021 address being registered are decoupled. A 6LN may use a same ROVR 1022 for multiple registrations or a different ROVR per registration, and 1023 the IID must not derive from the ROVR. In theory different 6LNs 1024 could use a same ROVR as long as they do not attempt to register the 1025 same address. 1027 The Modifier used in the computation of the Crypto-ID enables a 6LN 1028 to build different Crypto-IDs for different addresses with a same 1029 keypair. Using that facility improves the privacy of the 6LN as the 1030 expense of storage in the 6LR, which will need to store multiple 1031 CIPOs that contain the same public key. Note that if the attacker is 1032 the 6LR, then the Modifier alone does not provide a protection, and 1033 the 6LN would need to use different keys and MAC addresses in an 1034 attempt to obfuscate its multiple ownership. 1036 8. IANA considerations 1038 8.1. CGA Message Type 1040 This document defines a new 128-bit value of a Message Type tag under 1041 the CGA Message Type [RFC3972] name space: 0x8701 55c8 0cca dd32 6ab7 1042 e415 f148 84d0. 1044 8.2. Crypto-Type Subregistry 1046 IANA is requested to create a new subregistry "Crypto-Type 1047 Subregistry" in the "Internet Control Message Protocol version 6 1048 (ICMPv6) Parameters". The registry is indexed by an integer in the 1049 interval 0..255 and contains an Elliptic Curve, a Hash Function, a 1050 Signature Algorithm, Representation Conventions, Public key size, and 1051 Signature size, as shown in Table 1, which together specify a 1052 signature scheme (and which are fully specified in Appendix B). 1054 The following Crypto-Type values are defined in this document: 1056 +----------------+-----------------+--------------+-----------------+ 1057 | Crypto-Type | 0 (ECDSA256) | 1 (Ed25519) | 2 (ECDSA25519) | 1058 | value | | | | 1059 +================+=================+==============+=================+ 1060 | Elliptic curve | NIST P-256 | Curve25519 | Curve25519 | 1061 | | [FIPS186-4] | [RFC7748] | [RFC7748] | 1062 +----------------+-----------------+--------------+-----------------+ 1063 | Hash function |SHA-256 [RFC6234]| SHA-512 |SHA-256 [RFC6234]| 1064 | | | [RFC6234] | | 1065 +----------------+-----------------+--------------+-----------------+ 1066 | Signature |ECDSA [FIPS186-4]| Ed25519 |ECDSA [FIPS186-4]| 1067 | algorithm | | [RFC8032] | | 1068 +----------------+-----------------+--------------+-----------------+ 1069 | Representation | Weierstrass, | Edwards, | Weierstrass, | 1070 | conventions | (un)compressed, | compressed, | (un)compressed, | 1071 | | MSB/msb first, |LSB/lsb first,| MSB/msb first, | 1072 | | [RFC7518] | [RFC8037] | [CURVE-REPR] | 1073 +----------------+-----------------+--------------+-----------------+ 1074 |Public key size | 33/65 bytes | 32 bytes | 33/65 bytes | 1075 | | (compressed/ | (compressed) | (compressed/ | 1076 | | uncompressed) | | uncompressed) | 1077 +----------------+-----------------+--------------+-----------------+ 1078 | Signature size | 64 bytes | 64 bytes | 64 bytes | 1079 +----------------+-----------------+--------------+-----------------+ 1080 | Defining | This_RFC | This_RFC | This_RFC | 1081 | specification | | | | 1082 +----------------+-----------------+--------------+-----------------+ 1084 Table 1: Crypto-Types 1086 New Crypto-Type values providing similar or better security may be 1087 defined in the future. 1089 Assignment of new values for new Crypto-Type MUST be done through 1090 IANA with either "Specification Required" or "IESG Approval" as 1091 defined in BCP 26 [RFC8126]. 1093 8.3. IPv6 ND option types 1095 This document registers two new ND option types under the subregistry 1096 "IPv6 Neighbor Discovery Option Formats": 1098 +------------------------------+-----------------+---------------+ 1099 | Option Name | Suggested Value | Reference | 1100 +==============================+=================+===============+ 1101 | NDP Signature Option (NDPSO) | 38 | This document | 1102 +------------------------------+-----------------+---------------+ 1103 | Crypto-ID Parameters Option | 39 | This document | 1104 | (CIPO) | | | 1105 +------------------------------+-----------------+---------------+ 1107 Table 2: New ND options 1109 8.4. New 6LoWPAN Capability Bit 1111 IANA is requested to make additions to the Subregistry for "6LoWPAN 1112 Capability Bits" created for [RFC7400] as follows: 1114 +----------------+-----------------------+----------+ 1115 | Capability Bit | Description | Document | 1116 +================+=======================+==========+ 1117 | 09 | AP-ND Enabled (1 bit) | This_RFC | 1118 +----------------+-----------------------+----------+ 1120 Table 3: New 6LoWPAN Capability Bit 1122 9. Acknowledgments 1124 Many thanks to Charlie Perkins for his in-depth review and 1125 constructive suggestions. The authors are also especially grateful 1126 to Robert Moskowitz and Benjamin Kaduk for their comments and 1127 discussions that led to many improvements. The authors wish to also 1128 thank Shwetha Bhandari for actively shepherding this document and 1129 Roman Danyliw, Alissa Cooper, Mirja Kuhlewind, Eric Vyncke, Vijay 1130 Gurbani, Al Morton, and Adam Montville for their constructive reviews 1131 during the IESG process. Finally Many thanks to our INT area ADs, 1132 Suresh Krishnan and then Erik Kline, who supported us along the whole 1133 process. 1135 10. Normative References 1137 [RFC2119] Bradner, S., "Key words for use in RFCs to Indicate 1138 Requirement Levels", BCP 14, RFC 2119, 1139 DOI 10.17487/RFC2119, March 1997, 1140 . 1142 [RFC3971] Arkko, J., Ed., Kempf, J., Zill, B., and P. Nikander, 1143 "SEcure Neighbor Discovery (SEND)", RFC 3971, 1144 DOI 10.17487/RFC3971, March 2005, 1145 . 1147 [RFC6234] Eastlake 3rd, D. and T. Hansen, "US Secure Hash Algorithms 1148 (SHA and SHA-based HMAC and HKDF)", RFC 6234, 1149 DOI 10.17487/RFC6234, May 2011, 1150 . 1152 [RFC6775] Shelby, Z., Ed., Chakrabarti, S., Nordmark, E., and C. 1153 Bormann, "Neighbor Discovery Optimization for IPv6 over 1154 Low-Power Wireless Personal Area Networks (6LoWPANs)", 1155 RFC 6775, DOI 10.17487/RFC6775, November 2012, 1156 . 1158 [RFC7400] Bormann, C., "6LoWPAN-GHC: Generic Header Compression for 1159 IPv6 over Low-Power Wireless Personal Area Networks 1160 (6LoWPANs)", RFC 7400, DOI 10.17487/RFC7400, November 1161 2014, . 1163 [RFC7748] Langley, A., Hamburg, M., and S. Turner, "Elliptic Curves 1164 for Security", RFC 7748, DOI 10.17487/RFC7748, January 1165 2016, . 1167 [RFC8032] Josefsson, S. and I. Liusvaara, "Edwards-Curve Digital 1168 Signature Algorithm (EdDSA)", RFC 8032, 1169 DOI 10.17487/RFC8032, January 2017, 1170 . 1172 [RFC8174] Leiba, B., "Ambiguity of Uppercase vs Lowercase in RFC 1173 2119 Key Words", BCP 14, RFC 8174, DOI 10.17487/RFC8174, 1174 May 2017, . 1176 [RFC8505] Thubert, P., Ed., Nordmark, E., Chakrabarti, S., and C. 1177 Perkins, "Registration Extensions for IPv6 over Low-Power 1178 Wireless Personal Area Network (6LoWPAN) Neighbor 1179 Discovery", RFC 8505, DOI 10.17487/RFC8505, November 2018, 1180 . 1182 [FIPS186-4] 1183 FIPS 186-4, "Digital Signature Standard (DSS), Federal 1184 Information Processing Standards Publication 186-4", US 1185 Department of Commerce/National Institute of Standards and 1186 Technology , July 2013. 1188 [SEC1] SEC1, "SEC 1: Elliptic Curve Cryptography, Version 2.0", 1189 Standards for Efficient Cryptography , June 2009. 1191 11. Informative references 1193 [RFC3972] Aura, T., "Cryptographically Generated Addresses (CGA)", 1194 RFC 3972, DOI 10.17487/RFC3972, March 2005, 1195 . 1197 [BCP 106] Eastlake 3rd, D., Schiller, J., and S. Crocker, 1198 "Randomness Requirements for Security", BCP 106, RFC 4086, 1199 DOI 10.17487/RFC4086, June 2005, 1200 . 1202 [RFC4861] Narten, T., Nordmark, E., Simpson, W., and H. Soliman, 1203 "Neighbor Discovery for IP version 6 (IPv6)", RFC 4861, 1204 DOI 10.17487/RFC4861, September 2007, 1205 . 1207 [RFC4862] Thomson, S., Narten, T., and T. Jinmei, "IPv6 Stateless 1208 Address Autoconfiguration", RFC 4862, 1209 DOI 10.17487/RFC4862, September 2007, 1210 . 1212 [RFC4919] Kushalnagar, N., Montenegro, G., and C. Schumacher, "IPv6 1213 over Low-Power Wireless Personal Area Networks (6LoWPANs): 1214 Overview, Assumptions, Problem Statement, and Goals", 1215 RFC 4919, DOI 10.17487/RFC4919, August 2007, 1216 . 1218 [RFC4944] Montenegro, G., Kushalnagar, N., Hui, J., and D. Culler, 1219 "Transmission of IPv6 Packets over IEEE 802.15.4 1220 Networks", RFC 4944, DOI 10.17487/RFC4944, September 2007, 1221 . 1223 [RFC6282] Hui, J., Ed. and P. Thubert, "Compression Format for IPv6 1224 Datagrams over IEEE 802.15.4-Based Networks", RFC 6282, 1225 DOI 10.17487/RFC6282, September 2011, 1226 . 1228 [RFC7039] Wu, J., Bi, J., Bagnulo, M., Baker, F., and C. Vogt, Ed., 1229 "Source Address Validation Improvement (SAVI) Framework", 1230 RFC 7039, DOI 10.17487/RFC7039, October 2013, 1231 . 1233 [RFC7217] Gont, F., "A Method for Generating Semantically Opaque 1234 Interface Identifiers with IPv6 Stateless Address 1235 Autoconfiguration (SLAAC)", RFC 7217, 1236 DOI 10.17487/RFC7217, April 2014, 1237 . 1239 [RFC7518] Jones, M., "JSON Web Algorithms (JWA)", RFC 7518, 1240 DOI 10.17487/RFC7518, May 2015, 1241 . 1243 [BCP 201] Housley, R., "Guidelines for Cryptographic Algorithm 1244 Agility and Selecting Mandatory-to-Implement Algorithms", 1245 BCP 201, RFC 7696, DOI 10.17487/RFC7696, November 2015, 1246 . 1248 [RFC8037] Liusvaara, I., "CFRG Elliptic Curve Diffie-Hellman (ECDH) 1249 and Signatures in JSON Object Signing and Encryption 1250 (JOSE)", RFC 8037, DOI 10.17487/RFC8037, January 2017, 1251 . 1253 [RFC8064] Gont, F., Cooper, A., Thaler, D., and W. Liu, 1254 "Recommendation on Stable IPv6 Interface Identifiers", 1255 RFC 8064, DOI 10.17487/RFC8064, February 2017, 1256 . 1258 [RFC8065] Thaler, D., "Privacy Considerations for IPv6 Adaptation- 1259 Layer Mechanisms", RFC 8065, DOI 10.17487/RFC8065, 1260 February 2017, . 1262 [RFC8126] Cotton, M., Leiba, B., and T. Narten, "Guidelines for 1263 Writing an IANA Considerations Section in RFCs", BCP 26, 1264 RFC 8126, DOI 10.17487/RFC8126, June 2017, 1265 . 1267 [BACKBONE-ROUTER] 1268 Thubert, P., Perkins, C., and E. Levy-Abegnoli, "IPv6 1269 Backbone Router", Work in Progress, Internet-Draft, draft- 1270 ietf-6lo-backbone-router-20, 23 March 2020, 1271 . 1274 [CURVE-REPR] 1275 Struik, R., "Alternative Elliptic Curve Representations", 1276 Work in Progress, Internet-Draft, draft-ietf-lwig-curve- 1277 representations-09, 9 March 2020, 1278 . 1281 [breaking-ed25519] 1282 Samwel, N., Batina, L., Bertoni, G., Daemen, J., and R. 1283 Susella, "Breaking Ed25519 in WolfSSL", Cryptographers' 1284 Track at the RSA Conference , 2018, 1285 . 1288 Appendix A. Requirements Addressed in this Document 1290 In this section we state requirements of a secure neighbor discovery 1291 protocol for low-power and lossy networks. 1293 * The protocol MUST be based on the Neighbor Discovery Optimization 1294 for Low-power and Lossy Networks protocol defined in [RFC6775]. 1295 RFC6775 utilizes optimizations such as host-initiated interactions 1296 for sleeping resource-constrained hosts and elimination of 1297 multicast address resolution. 1298 * New options to be added to Neighbor Solicitation messages MUST 1299 lead to small packet sizes, especially compared with existing 1300 protocols such as SEcure Neighbor Discovery (SEND). Smaller 1301 packet sizes facilitate low-power transmission by resource- 1302 constrained nodes on lossy links. 1303 * The support for this registration mechanism SHOULD be extensible 1304 to more LLN links than IEEE 802.15.4 only. Support for at least 1305 the LLN links for which a 6lo "IPv6 over foo" specification 1306 exists, as well as Low-Power Wi-Fi SHOULD be possible. 1307 * As part of this extension, a mechanism to compute a unique 1308 Identifier should be provided with the capability to form a Link 1309 Local Address that SHOULD be unique at least within the LLN 1310 connected to a 6LBR. 1311 * The Address Registration Option used in the ND registration SHOULD 1312 be extended to carry the relevant forms of Unique Interface 1313 Identifier. 1314 * The Neighbor Discovery should specify the formation of a site- 1315 local address that follows the security recommendations from 1316 [RFC7217]. 1318 Appendix B. Representation Conventions 1320 B.1. Signature Schemes 1322 The signature scheme ECDSA256 corresponding to Crypto-Type 0 is 1323 ECDSA, as specified in [FIPS186-4], instantiated with the NIST prime 1324 curve P-256, as specified in Appendix B of [FIPS186-4], and the hash 1325 function SHA-256, as specified in [RFC6234], where points of this 1326 NIST curve are represented as points of a short-Weierstrass curve 1327 (see [FIPS186-4]) and are encoded as octet strings in most- 1328 significant-bit first (msb) and most-significant-byte first (MSB) 1329 order. The signature itself consists of two integers (r and s), 1330 which are each encoded as fixed-size octet strings in most- 1331 significant-bit first and most-significant-byte first order. For 1332 details on ECDSA, see [FIPS186-4]; for details on the encoding of 1333 public keys, see Appendix B.3; for details on the signature encoding, 1334 see Appendix B.2. 1336 The signature scheme Ed25519 corresponding to Crypto-Type 1 is EdDSA, 1337 as specified in [RFC8032], instantiated with the Montgomery curve 1338 Curve25519, as specified in [RFC7748], and the hash function SHA-512, 1339 as specified in [RFC6234], where points of this Montgomery curve are 1340 represented as points of the corresponding twisted Edwards curve 1341 Edwards25519 (see Appendix B.4) and are encoded as octet strings in 1342 least-significant-bit first (lsb) and least-significant-byte first 1343 (LSB) order. The signature itself consists of a bit string that 1344 encodes a point of this twisted Edwards curve, in compressed format, 1345 and an integer encoded in least-significant-bit first and least- 1346 significant-byte first order. For details on EdDSA, the encoding of 1347 public keys and that of signatures, see the specification of pure 1348 Ed25519 in [RFC8032]. 1350 The signature scheme ECDSA25519 corresponding to Crypto-Type 2 is 1351 ECDSA, as specified in [FIPS186-4], instantiated with the Montgomery 1352 curve Curve25519, as specified in [RFC7748], and the hash function 1353 SHA-256, as specified in [RFC6234], where points of this Montgomery 1354 curve are represented as points of the corresponding short- 1355 Weierstrass curve Wei25519 (see Appendix B.4) and are encoded as 1356 octet strings in most-significant-bit first and most-significant-byte 1357 first order. The signature itself consists of a bit string that 1358 encodes two integers, each encoded as fixed-size octet strings in 1359 most-significant-bit first and most-significant-byte first order. 1360 For details on ECDSA, see [FIPS186-4]; for details on the encoding of 1361 public keys, see Appendix B.3; for details on the signature encoding, 1362 see Appendix B.2 1364 B.2. Representation of ECDSA Signatures 1366 With ECDSA, each signature is an ordered pair (r, s) of integers 1367 [FIPS186-4], where each integer is represented as a 32-octet string 1368 according to the Field Element to Octet String conversion rules in 1369 [SEC1] and where the ordered pair of integers is represented as the 1370 rightconcatenation of these representation values (thereby resulting 1371 in a 64-octet string). The inverse operation checks that the 1372 signature is a 64-octet string and represents the left-side and 1373 right-side halves of this string (each a 32-octet string) as the 1374 integers r and s, respectively, using the Octet String to Field 1375 Element conversion rules in [SEC1]. 1377 B.3. Representation of Public Keys Used with ECDSA 1379 ECDSA is specified to be used with elliptic curves in short- 1380 Weierstrass form. Each point of such a curve is represented as an 1381 octet string using the Elliptic Curve Point to Octet String 1382 conversion rules in [SEC1], where point compression may be enabled 1383 (which is indicated by the leftmost octet of this representation). 1384 The inverse operation converts an octet string to a point of this 1385 curve using the Octet String to Elliptic Curve Point conversion rules 1386 in [SEC1], whereby the point is rejected if this is the so-called 1387 point at infinity. (This is the case if the input to this inverse 1388 operation is an octet string of length 1.) 1390 B.4. Alternative Representations of Curve25519 1392 The elliptic curve Curve25519, as specified in [RFC7748], is a so- 1393 called Montgomery curve. Each point of this curve can also be 1394 represented as a point of a twisted Edwards curve or as a point of an 1395 elliptic curve in short-Weierstrass form, via a coordinate 1396 transformation (a so-called isomorphic mapping). The parameters of 1397 the Montgomery curve and the corresponding isomorphic curves in 1398 twisted Edwards curve and short-Weierstrass form are as indicated 1399 below. Here, the domain parameters of the Montgomery curve 1400 Curve25519 and of the twisted Edwards curve Edwards25519 are as 1401 specified in [RFC7748]; the domain parameters of the elliptic curve 1402 Wei25519 in short-Weierstrass curve comply with Section 6.1.1 of 1403 [FIPS186-4]. For further details on these curves and on the 1404 coordinate transformations referenced above, see [CURVE-REPR]. 1406 General parameters (for all curve models): 1408 p 2^{255}-19 1409 (=0x7fffffff ffffffff ffffffff ffffffff ffffffff ffffffff ffffffff 1410 ffffffed) 1411 h 8 1412 n 1413 723700557733226221397318656304299424085711635937990760600195093828 1414 5454250989 1415 (=2^{252} + 0x14def9de a2f79cd6 5812631a 5cf5d3ed) 1417 Montgomery curve-specific parameters (for Curve25519): 1419 A 486662 1420 B 1 1421 Gu 9 (=0x9) 1422 Gv 1423 147816194475895447910205935684099868872646061346164752889648818377 1424 55586237401 1425 (=0x20ae19a1 b8a086b4 e01edd2c 7748d14c 923d4d7e 6d7c61b2 29e9c5a2 1426 7eced3d9) 1428 Twisted Edwards curve-specific parameters (for Edwards25519): 1430 a -1 (-0x01) 1431 d -121665/121666 1432 (=3709570593466943934313808350875456518954211387984321901638878553 1433 3085940283555) 1434 (=0x52036cee 2b6ffe73 8cc74079 7779e898 00700a4d 4141d8ab 75eb4dca 1435 135978a3) 1436 Gx 1437 151122213495354007725011514095885315114540126930418572060461132839 1438 49847762202 1439 (=0x216936d3 cd6e53fe c0a4e231 fdd6dc5c 692cc760 9525a7b2 c9562d60 1440 8f25d51a) 1441 Gy 4/5 1442 (=4631683569492647816942839400347516314130799386625622561578303360 1443 3165251855960) 1444 (=0x66666666 66666666 66666666 66666666 66666666 66666666 66666666 1445 66666658) 1447 Weierstrass curve-specific parameters (for Wei25519): 1449 a 1450 192986815395526992372618308347813179755449974442734273399095973345 1451 73241639236 1452 (=0x2aaaaaaa aaaaaaaa aaaaaaaa aaaaaaaa aaaaaaaa aaaaaaaa aaaaaa98 1453 4914a144) 1454 b 1455 557517466698189089076452890782571408182411037279010123152944008379 1456 56729358436 1457 (=0x7b425ed0 97b425ed 097b425e d097b425 ed097b42 5ed097b4 260b5e9c 1458 7710c864) 1459 GX 1460 192986815395526992372618308347813179755449974442734273399095973346 1461 52188435546 1462 (=0x2aaaaaaa aaaaaaaa aaaaaaaa aaaaaaaa aaaaaaaa aaaaaaaa aaaaaaaa 1463 aaad245a) 1464 GY 1465 147816194475895447910205935684099868872646061346164752889648818377 1466 55586237401 1467 (=0x20ae19a1 b8a086b4 e01edd2c 7748d14c 923d4d7e 6d7c61b2 29e9c5a2 1468 7eced3d9) 1470 Authors' Addresses 1472 Pascal Thubert (editor) 1473 Cisco Systems, Inc 1474 Building D 1475 45 Allee des Ormes - BP1200 1476 06254 MOUGINS - Sophia Antipolis 1477 France 1479 Phone: +33 497 23 26 34 1480 Email: pthubert@cisco.com 1482 Behcet Sarikaya 1484 Email: sarikaya@ieee.org 1486 Mohit Sethi 1487 Ericsson 1488 FI-02420 Jorvas 1489 Finland 1491 Email: mohit@piuha.net 1493 Rene Struik 1494 Struik Security Consultancy 1496 Email: rstruik.ext@gmail.com