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Checking references for intended status: Proposed Standard ---------------------------------------------------------------------------- (See RFCs 3967 and 4897 for information about using normative references to lower-maturity documents in RFCs) == Outdated reference: A later version (-21) exists of draft-ietf-6lowpan-nd-13 Summary: 0 errors (**), 0 flaws (~~), 2 warnings (==), 1 comment (--). Run idnits with the --verbose option for more detailed information about the items above. -------------------------------------------------------------------------------- 2 Network Working Group B. Sarikaya 3 Internet-Draft F. Xia 4 Intended status: Standards Track Huawei USA 5 Expires: April 7, 2011 October 4, 2010 7 Lightweight Secure Neighbor Discovery for Low-power and Lossy Networks 8 draft-sarikaya-lwip-cgand-00 10 Abstract 12 This document defines lightweight secure neighbor discovery for low- 13 power and lossy networks. The nodes generate a Cryptographically 14 Generated Address using an Elliptic Curve Cryptography public key, 15 register the Cryptographically Generated Address with a default 16 router and periodically refresh the registration. Modifications to 17 6lowpan Neighbor Discovery protocol are described for secure neighbor 18 discovery for low-power and lossy networks. Cryptographically 19 generated address and digital signature are calculated using elliptic 20 curve cryptography public key of the node. 22 Status of this Memo 24 This Internet-Draft is submitted in full conformance with the 25 provisions of BCP 78 and BCP 79. 27 Internet-Drafts are working documents of the Internet Engineering 28 Task Force (IETF). Note that other groups may also distribute 29 working documents as Internet-Drafts. The list of current Internet- 30 Drafts is at http://datatracker.ietf.org/drafts/current/. 32 Internet-Drafts are draft documents valid for a maximum of six months 33 and may be updated, replaced, or obsoleted by other documents at any 34 time. It is inappropriate to use Internet-Drafts as reference 35 material or to cite them other than as "work in progress." 37 This Internet-Draft will expire on April 7, 2011. 39 Copyright Notice 41 Copyright (c) 2010 IETF Trust and the persons identified as the 42 document authors. All rights reserved. 44 This document is subject to BCP 78 and the IETF Trust's Legal 45 Provisions Relating to IETF Documents 46 (http://trustee.ietf.org/license-info) in effect on the date of 47 publication of this document. Please review these documents 48 carefully, as they describe your rights and restrictions with respect 49 to this document. Code Components extracted from this document must 50 include Simplified BSD License text as described in Section 4.e of 51 the Trust Legal Provisions and are provided without warranty as 52 described in the Simplified BSD License. 54 Table of Contents 56 1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . . 3 57 2. Terminology . . . . . . . . . . . . . . . . . . . . . . . . . 3 58 3. Problem Statement . . . . . . . . . . . . . . . . . . . . . . 4 59 4. New Options . . . . . . . . . . . . . . . . . . . . . . . . . 4 60 4.1. CGA Parameters and Digital Signature Option . . . . . . . 4 61 4.2. Digital Signature Option . . . . . . . . . . . . . . . . . 6 62 4.3. Calculation of Digital Signature and CGA Using ECC . . . . 7 63 5. Protocol Interactions . . . . . . . . . . . . . . . . . . . . 7 64 5.1. Packet Sizes . . . . . . . . . . . . . . . . . . . . . . . 9 65 6. Security Considerations . . . . . . . . . . . . . . . . . . . 10 66 7. IANA considerations . . . . . . . . . . . . . . . . . . . . . 10 67 8. Acknowledgements . . . . . . . . . . . . . . . . . . . . . . . 10 68 9. References . . . . . . . . . . . . . . . . . . . . . . . . . . 10 69 9.1. Normative References . . . . . . . . . . . . . . . . . . . 10 70 9.2. Informative references . . . . . . . . . . . . . . . . . . 11 71 Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . . 11 73 1. Introduction 75 Neighbor discovery for IPv6 [RFC4861] and stateless address 76 autoconfiguration [RFC4862] together referred to as neighbor 77 discovery protocols (NDP) are defined for regular hosts operating in 78 wired/wireless links. These protocols are not suitable and require 79 optimizations for resource constrained, low power hosts operating in 80 lossy wireless links. Neighbor discovery optimizations for 6lowpan 81 networks include simple optimizations such as host address 82 registration feature using the address registration option which is 83 sent in unicast Neighbor Solicitation (NS) and Neighbor Advertisement 84 (NA) messages [I-D.ietf-6lowpan-nd]. 86 Neighbor discovery protocols (NDP) are not secure especially when 87 physical security on the link is not assured and vulnerable to 88 attacks. Secure neighbor discovery protocol (SEND) is defined to 89 secure NDP [RFC3971]. Cryptographically generated addresses (CGA) 90 are used in SEND [RFC3972]. SEND mandates the use of RSA signature 91 algorithm which is computationally heavy and not suitable to use for 92 low-power and resource constrained nodes 93 [I-D.cheneau-csi-send-sig-agility]. The use of RSA public key and 94 signature leads to long message sizes not suitable to use in low-bit 95 rate, short range, asymmetric and non-transitive links such as IEEE 96 802.15.4. 98 In this document we extend 6lowpan neighbor discovery protocol with 99 cryptographically generated addresses. The nodes generate CGAs and 100 register them with the default router. CGA generation is based on 101 elliptic curve cryptography (ECC)and signature is calculated using 102 elliptic curve digital signature algorithm (ECDSA) known to be 103 lightweight and lead to much smaller packet sizes. The resulting 104 protocol is called Lightweight Secure Neighbor Discovery Protocol 105 (LSEND). 107 2. Terminology 109 The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT", 110 "SHOULD", "SHOULD NOT", "RECOMMENDED", "MAY", and "OPTIONAL" in this 111 document are to be interpreted as described in [RFC2119]. 113 The terminology in this document is based on the definitions in 114 [RFC3971], [RFC3972] in addition to the ones specified in 115 [I-D.ietf-6lowpan-nd]. 117 3. Problem Statement 119 In this section we state requirements on secure neighbor discovery 120 protocol for low-power and lossy networks. 122 The protocol MUST be based on Neighbor Discovery Optimization for 123 Low-power and Lossy Networks protocol defined in 124 [I-D.ietf-6lowpan-nd] due to the host-initiated interactions to allow 125 for sleeping hosts, elimination of multicast-based address resolution 126 for hosts, etc. 128 New options to be added to neighbor solicitation messages MUST lead 129 to minimal packet sizes. Such packet sizes facilitate low-power 130 transmission by resource constrained nodes on lossy links. 132 CGA generation, signature and key hash calculation MUST avoid the use 133 of SHA-1 which is known to have security flaws. In this document, we 134 use SHA-2 instead of SHA-1 and thus avoid SHA-1's flaws. 136 Public key and signature sizes MUST be minimized and signature 137 calculation MUST be lightweight. In this document we adopt ECC and 138 ECDSA with P-256 curve in order to meet this requirement. 140 4. New Options 142 4.1. CGA Parameters and Digital Signature Option 144 This option contains both CGA parameters and the digital signature. 146 A summary of the CGA Parameters and Digital Signature Option format 147 is shown below. 149 0 1 2 3 150 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 1 151 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 152 | Type | Length | Pad Length | Sig. Length | 153 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 154 | | 155 . . 156 . CGA Parameters . 157 . . 158 | | 159 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 160 | | 161 . . 162 . Digital Signature . 163 . . 164 | | 165 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 166 | | 167 . . 168 . Padding . 169 . . 170 | | 171 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 173 Type 175 TBA1 for CGA Parameters and Digital Signature 176 Length 178 The length of the option (including the Type, Length, Pad Length, 179 Signature Length, CGA Parameters, Digital Signature and Padding 180 fields) in units of 8 octets. 181 Pad Length 183 The length of the Padding field. 184 Sig Length 186 The length of the Digital Signature field. 187 CGA Parameters 189 The CGA Parameters field is variable-length containing the CGA 190 Parameters data structure described in Section 4 of [RFC3972]. 191 Digital Signature 193 The Digital Signature field is a variable length field containing 194 a Elliptic Curve Digital Signature Algorithm (ECDSA) signature 195 (with SHA-256 and P-256 curve of [FIPS-186-3]). Digital signature 196 is constructed as explained in Section 4.3. 198 Padding 200 The Padding field contains a variable-length field making the CGA 201 Parameters and Digital Signature Option length a multiple of 8. 203 4.2. Digital Signature Option 205 This option contains the digital signature. 207 A summary of the Digital Signature Option format is shown below. 208 Note that this option has the same format as RSA Signature Option 209 defined in [RFC3971]. The differences are that Digital Signature 210 field carries Ellictic Curve Cryptography signature not RSA signature 211 and in calculating Key Hash field SHA-2 is used not SHA-1. 213 0 1 2 3 214 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 1 215 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 216 | Type | Length | Reserved | 217 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 218 | | 219 | Key Hash | 220 | | 221 | | 222 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 223 | | 224 . . 225 . Digital Signature . 226 . . 227 | | 228 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 229 | | 230 . . 231 . Padding . 232 . . 233 | | 234 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 236 Type 238 TBA2 for Digital Signature 239 Length 241 The length of the option (including the Type, Length, Reserved, 242 Key Hash, Digital Signature and Padding fields) in units of 8 243 octets. 245 Key Hash 247 The Key Hash field is a 128-bit field containing the most 248 significant (leftmost) 128 bits of a SHA-2 hash of the public key 249 used for constructing the signature. This is the same as in 250 [RFC3971] except for SHA-1 which has been proved to be flawed in 251 the light of recent attacks [NIST-ST]. 252 Digital Signature 254 Same as in Section 4.1. 255 Padding 257 The Padding field contains a variable-length field containing as 258 many bytes long as remain after the end of the signature. 260 4.3. Calculation of Digital Signature and CGA Using ECC 262 Due to the use of Elliptic Curve Cryptography, the following 263 modifications are needed to [RFC3971] and [RFC3972]. 265 Digital signature is constructed by using the sender's private key 266 over the same sequence of octets specified in Section 5.2 of 267 [RFC3971] up to all neighbor discovery protocol options preceding the 268 Digital Signature option containing Elliptic Curve Cryptography 269 digital signature. The signature value is computed using the ECDSA 270 signature algorithm as defined in [SEC1] and hash function SHA-256. 272 Public Key is the most important parameter in CGA Parameters defined 273 in Section 4.1. Public Key MUST be DER-encoded ASN.1 structure of 274 the type SubjectPublicKeyInfo formatted as ECC Public Key. The 275 AlgorithmIdentifier, contained in ASN.1 structure of type 276 SubjectPublicKeyInfo, MUST be the (unrestricted) id- ecPublicKey 277 algorithm identifier, which is OID 1.2.840.10045.2.1, and the 278 subjectPublicKey MUST be formatted as an ECC Public Key, specified in 279 Section 2.2 of [RFC5480]. 281 Note that the ECC key lengths are determined by the namedCurves 282 parameter stored in ECParameters field of the AlgorithmIdentifier. 283 The named curve to use is secp256r1 corresponding to P-256 which is 284 OID 1.2.840.10045.3.1.7. 286 5. Protocol Interactions 288 Lightweight Secure Neighbor Discovery for Low-power and Lossy 289 Networks (LSEND for LLN) modifies Neighbor Discovery Optimization for 290 Low-power and Lossy Networks [I-D.ietf-6lowpan-nd] as explained in 291 this section. Protocol interactions are shown in Figure 1. 293 6LoWPAN Border Routers (6LBR) send router advertisements (RA). 294 6LoWPAN Nodes (6LN) or nodes in short receive these RAs and generate 295 their own cryptographically generated addresses using elliptic curve 296 cryptography as explained in Section 4.3. The node sends a neighbor 297 solicitation (NS) message with address registration option (ARO) to 298 6LBR. Such a NS is called an address registration NS. 300 A LSEND for LLN node MUST send an address registration NS message 301 after adding CGA Parameters and Digital Signature Option defined in 302 Section 4.1. Source address MUST be set to its crypotographically 303 generated address. A LSEND for LLN node MUST set the Owner Interface 304 Identifier field (EUI-64) in ARO to the rightmost 64 bits of its 305 crypotographically generated address. Subnet Prefix field of CGA 306 Parameters MUST be set to the leftmost 64 bits of its 307 crypotographically generated address. Public Key field of CGA 308 Parameters MUST be set to the node's ECC Public Key. 310 6LBR receives the address registration NS. 6LBR verifies the source 311 address as described in Section 5.1.2. of [RFC3971] using the claimed 312 source address and CGA Parameters field in the message. After 313 successfully verifying the address 6LBR next does a cryptographic 314 check of the signature included in Digital Signature field in the 315 message. If all checks succeed then 6LBR performs a duplicate 316 address detection procedure first on the address. If that also 317 succeeds 6LBR registers CGA in the neighbor cache. 6LBR also caches 318 the node's public key. 320 6LBR sends an address registration neighbor advertisement (NA) as a 321 reply to confirm the node's registration. Status is set to 0 to 322 indicate success. This completes initial address registration. The 323 address registration needs to be refreshed after the neighbor cache 324 entry times out. 326 6LN 6LBR 327 | | 328 |<-----------------------RA-------------------------------| 329 | | 330 |---------------NS with ARO and CGA Option--------------->| 331 | | 332 |<-----------------------NA with ARO----------------------| 333 | | 334 |---------------NS with ARO and Digital Signature Option->| 335 | | 336 |<-----------------------NA with ARO----------------------| 337 | | 338 |---------------NS with ARO and Digital Signature Option->| 339 | | 340 |<-----------------------NA with ARO----------------------| 342 Figure 1: Lightweight SEND for LLA Protocol 344 In order to refresh the neighbor cache entry, a LSEND for LLN node 345 MUST send an address registration NS message after adding Digital 346 Signature Option defined in Section 4.2. Key hash field is a hash of 347 the node's public key and MUST be set as described in Section 4.2. 348 Digital Signature field MUST be set as described in Section 4.2. 350 6LBR receives the address registration refresh NS. 6LBR uses the key 351 hash field in Digital Signature Option to find the node's public key 352 from the neighbor cache. 6LBR verifies the digital signature in the 353 NS. In case of successful verification, 6LBR sends back an address 354 registration neighbor advertisement (NA) to the node and sets the 355 status to 0 indicating successful refreshment of the CGA of the node. 356 Similar refresh NS and NA exchanges happen afterwards as shown in 357 Figure 1 359 5.1. Packet Sizes 361 Original address registration NS message contains 40 byte header and 362 ARO is 16 octets. DER-encoded ECC Public Key for P-256 curve is 88 363 octets long. Digital Signature field when using ECDSA for P-256 364 curve is 71 octets long without padding 365 [I-D.cheneau-csi-ecc-sig-agility]. 367 CGA Parameters and Digital Signature Option's CGA Parameters include 368 16 octet modifier, 8 octet prefix obtained from the router 369 advertisement message sent from 6LBR, 1 octet collision count and 88 370 octet Public Key. Digital Signature is 71 octets. The option is 184 371 octets with Padding 0 octets. The total message size of an original 372 LSEND address registration NS message is 240 octets and such a 373 message can be encapsulated into three 802.15.4 frames. 375 An address registration refresh NS message contains an ARO which is 376 16 octets and digital signature option containing 16 octet key hash 377 and 71 octet signature and 5 octet Padding. The message is 152 378 octets long with the header. Such a message could be encapsulated in 379 two 802.15.4 frames. 381 6. Security Considerations 383 Same considerations regarding the threats to the Local Link Not 384 Covered as in [RFC3971] apply. 386 The threats discussed in Section 9.2 of [RFC3971] are countered by 387 the protocol described in this document as well. 389 As to the attacks to the protocol itself, denial of service attacks 390 that involve producing a very high number of packets are deemed 391 unlikely because of the assumptions on the node capabilities in low- 392 power and lossy networks. 394 7. IANA considerations 396 This document defines two new options to be used in neighbor 397 discovery protocol messages and new type values for CGA Parameters 398 and Digital Signature Option (TBA1) and Digital Signature Option 399 (TBA2) need to be assigned by IANA. 401 8. Acknowledgements 403 TBD. 405 9. References 407 9.1. Normative References 409 [RFC2119] Bradner, S., "Key words for use in RFCs to Indicate 410 Requirement Levels", BCP 14, RFC 2119, March 1997. 412 [RFC3971] Arkko, J., Kempf, J., Zill, B., and P. Nikander, "SEcure 413 Neighbor Discovery (SEND)", RFC 3971, March 2005. 415 [RFC3972] Aura, T., "Cryptographically Generated Addresses (CGA)", 416 RFC 3972, March 2005. 418 [RFC4861] Narten, T., Nordmark, E., Simpson, W., and H. Soliman, 419 "Neighbor Discovery for IP version 6 (IPv6)", RFC 4861, 420 September 2007. 422 [RFC4862] Thomson, S., Narten, T., and T. Jinmei, "IPv6 Stateless 423 Address Autoconfiguration", RFC 4862, September 2007. 425 [RFC5480] Turner, S., Brown, D., Yiu, K., Housley, R., and T. Polk, 426 "Elliptic Curve Cryptography Subject Public Key 427 Information", RFC 5480, March 2009. 429 [I-D.ietf-6lowpan-nd] 430 Shelby, Z., Chakrabarti, S., and E. Nordmark, "Neighbor 431 Discovery Optimization for Low-power and Lossy Networks", 432 draft-ietf-6lowpan-nd-13 (work in progress), 433 September 2010. 435 9.2. Informative references 437 [SEC1] "Standards for Efficient Crtptography Group. SEC 1: 438 Elliptic Curve Cryptography", September 2000. 440 [FIPS-186-3] 441 "National Institute of Standards and Technology, "Digital 442 Signature Standard"", June 2009. 444 [NIST-ST] "National Institute of Standards and Technology, "NIST 445 Comments on Cryptanalytic Attackts on SHA-1"", 446 January 2009, 447 . 449 [I-D.cheneau-csi-ecc-sig-agility] 450 Cheneau, T., Laurent, M., Shen, S., and M. Vanderveen, 451 "ECC public key and signature support in Cryptographically 452 Generated Addresses (CGA) and in the Secure Neighbor 453 Discovery (SEND)", draft-cheneau-csi-ecc-sig-agility-02 454 (work in progress), June 2010. 456 [I-D.cheneau-csi-send-sig-agility] 457 Cheneau, T., Laurent, M., Shen, S., and M. Vanderveen, 458 "Signature Algorithm Agility in the Secure Neighbor 459 Discovery (SEND) Protocol", 460 draft-cheneau-csi-send-sig-agility-02 (work in progress), 461 June 2010. 463 Authors' Addresses 465 Behcet Sarikaya 466 Huawei USA 467 1700 Alma Dr. Suite 500 468 Plano, TX 75075 470 Phone: +1 972-509-5599 471 Email: sarikaya@ieee.org 473 Frank Xia 474 Huawei USA 475 1700 Alma Dr. Suite 500 476 Plano, TX 75075 478 Phone: +1 972-509-5599 479 Email: xiayangsong@huawei.com