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'8') (Obsoleted by RFC 4033, RFC 4034, RFC 4035) -- Obsolete informational reference (is this intentional?): RFC 3445 (ref. '11') (Obsoleted by RFC 4033, RFC 4034, RFC 4035) Summary: 3 errors (**), 0 flaws (~~), 9 warnings (==), 6 comments (--). Run idnits with the --verbose option for more detailed information about the items above. -------------------------------------------------------------------------------- 2 IPSECKEY WG M. Richardson 3 Internet-Draft SSW 4 Expires: November 26, 2003 May 28, 2003 6 A method for storing IPsec keying material in DNS. 7 draft-ietf-ipseckey-rr-03.txt 9 Status of this Memo 11 This document is an Internet-Draft and is in full conformance with 12 all provisions of Section 10 of RFC2026. 14 Internet-Drafts are working documents of the Internet Engineering 15 Task Force (IETF), its areas, and its working groups. Note that 16 other groups may also distribute working documents as Internet- 17 Drafts. 19 Internet-Drafts are draft documents valid for a maximum of six months 20 and may be updated, replaced, or obsoleted by other documents at any 21 time. It is inappropriate to use Internet-Drafts as reference 22 material or to cite them other than as "work in progress." 24 The list of current Internet-Drafts can be accessed at http:// 25 www.ietf.org/ietf/1id-abstracts.txt. 27 The list of Internet-Draft Shadow Directories can be accessed at 28 http://www.ietf.org/shadow.html. 30 This Internet-Draft will expire on November 26, 2003. 32 Copyright Notice 34 Copyright (C) The Internet Society (2003). All Rights Reserved. 36 Abstract 38 This document describes a new resource record for DNS. This record 39 may be used to store public keys for use in IPsec systems. 41 This record replaces the functionality of the sub-type #1 of the KEY 42 Resource Record, which has been obsoleted by RFC3445. 44 Table of Contents 46 1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . . 3 47 1.1 Overview . . . . . . . . . . . . . . . . . . . . . . . . . . . 3 48 2. Storage formats . . . . . . . . . . . . . . . . . . . . . . . 4 49 2.1 IPSECKEY RDATA format . . . . . . . . . . . . . . . . . . . . 4 50 2.2 RDATA format - precedence . . . . . . . . . . . . . . . . . . 4 51 2.3 RDATA format - algorithm type . . . . . . . . . . . . . . . . 4 52 2.4 RDATA format - gateway type . . . . . . . . . . . . . . . . . 5 53 2.5 RDATA format - gateway . . . . . . . . . . . . . . . . . . . . 5 54 2.6 RDATA format - RSA public key . . . . . . . . . . . . . . . . 5 55 2.7 RDATA format - DSA public key . . . . . . . . . . . . . . . . 6 56 3. Presentation formats . . . . . . . . . . . . . . . . . . . . . 7 57 3.1 Representation of IPSECKEY RRs . . . . . . . . . . . . . . . . 7 58 3.2 Examples . . . . . . . . . . . . . . . . . . . . . . . . . . . 7 59 4. Security Considerations . . . . . . . . . . . . . . . . . . . 9 60 4.1 Active attacks against unsecured IPSECKEY resource records . . 9 61 5. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 11 62 6. Acknowledgments . . . . . . . . . . . . . . . . . . . . . . . 12 63 Normative references . . . . . . . . . . . . . . . . . . . . . 13 64 Non-normative references . . . . . . . . . . . . . . . . . . . 14 65 Author's Address . . . . . . . . . . . . . . . . . . . . . . . 14 66 Full Copyright Statement . . . . . . . . . . . . . . . . . . . 15 68 1. Introduction 70 The type number for the IPSECKEY RR is TBD. 72 1.1 Overview 74 The IPSECKEY resource record (RR) is used to publish a public key 75 that is to be associated with a Domain Name System (DNS) name for use 76 with the IPsec protocol suite. This can be the public key of a 77 host, network, or application (in the case of per-port keying). 79 The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT", 80 "SHOULD", "SHOULD NOT", "RECOMMENDED", "MAY", and "OPTIONAL" in this 81 document are to be interpreted as described in RFC2119 [6]. 83 An IPSECKEY resource record SHOULD be used in combination with DNSSEC 84 unless some other means of authenticating the IPSECKEY resource 85 record is available. 87 It is expected that there will often be multiple IPSECKEY resource 88 records at the same node. This will be due to the presence of 89 multiple gateways and the need to rollover keys. 91 This resource record is class independent. 93 2. Storage formats 95 2.1 IPSECKEY RDATA format 97 The RDATA for an IPSECKEY RR consists of a precedence value, a public 98 key, algorithm type, and an optional gateway address. 100 0 1 2 3 101 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 1 102 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 103 | precedence | gateway type | algorithm | gateway | 104 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-------------+ + 105 ~ gateway ~ 106 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 107 | / 108 / public key / 109 / / 110 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-| 112 2.2 RDATA format - precedence 114 This is an 8-bit precedence for this record. This is interpreted in 115 the same way as the PREFERENCE field described in section 3.3.9 of 116 RFC1035 [2]. 118 Gateways listed in IPSECKEY records records with lower precedence 119 are to be attempted first. Where there is a tie in precedence, they 120 order should be non-deterministic. 122 2.3 RDATA format - algorithm type 124 The algorithm field indicates the type of key that is present in the 125 public key field. A positive number larger than 0 identifies an 126 algorithm type. The following values, which have been previously 127 defined by IANA, are useful (see RFC2535 [8]). 129 A value of 0 indicates that no key is present. 131 The following values defined by IANA are useful: 133 3 A DSA key is present, in the format defined in RFC2536 [9] 135 5 A RSA key is present, in the format defined in RFC3110 [10] 137 2.4 RDATA format - gateway type 139 The gateway type field indicates the format of the information that 140 is stored in the gateway field. 142 The following values are defined: 144 0 No gateway is present 146 1 A 4-byte IPv4 address is present 148 2 A 16-byte IPv6 address is present 150 3 A wire-encoded domain name is present. The wire-encoded format is 151 self-describing, so the length is implicit. The domain name MUST 152 NOT be compressed. 154 2.5 RDATA format - gateway 156 The gateway field indicates a gateway to which an IPsec tunnel may be 157 created in order to reach the entity named by this resource record. 159 There are three formats: 161 A 32-bit IPv4 address is present in the gateway field. The data 162 portion is an IPv4 address as described in section 3.4.1 of RFC1035 163 [2]. This is a 32-bit number in network byte order. 165 A 128-bit IPv6 address is present in the gateway field. The data 166 portion is an IPv6 address as described in section 3.2 of RFC1886 167 [5]. This is a 128-bit number in network byte order. 169 The gateway field is a normal wire-encoded domain name, as described 170 in section 3.3 of RFC1035 [2]. 172 2.6 RDATA format - RSA public key 174 If the algorithm type has the value 5, then public key portion 175 contains an RSA public key, encoded as described in section 2 of 176 RFC3110 [10]. 178 RFC2065 limited the exponent and modulus to 2552 bits in length, and 179 RFC3110 limits them to 4096 bits. No such limit is specified here 180 for the purposes of encoding and decoding. 182 The length in octets of the public exponent length is represented as 183 one octet if it is in the range of 1 to 255, and by a zero octet 184 followed by a two octet unsigned length if it is longer than 255 185 bytes. The public key modulus field is a multiprecision unsigned 186 integer. The length of the modulus can be determined from the 187 RDLENGTH and the preceding RDATA fields including the exponent. 189 Leading zero bytes are prohibited in the exponent and modulus. 191 2.7 RDATA format - DSA public key 193 If the algorithm type has the value 3, then public key portion 194 contains an DSA public key, encoded as described in RFC2536 [9]. 196 3. Presentation formats 198 3.1 Representation of IPSECKEY RRs 200 IPSECKEY RRs may appears in a zone data master file. The precedence, 201 gateway type and algorithm and gateway fields are REQUIRED. There 202 base64 encoded public key block is OPTIONAL; if not present, then the 203 public key field of the resource record MUST be contrued being zero 204 octets in length. 206 If no gateway is to be indicated, then the gateway type field MUST be 207 zero, and the gateway field MUST be "." 209 IN IPSECKEY ( precedence gateway-type algorithm 210 gateway base64-encoded-public-key ) 212 3.2 Examples 214 An example of a node 192.0.2.38 that will accept IPsec tunnels on its 215 own behalf. 217 38.2.0.192.in-addr.arpa. 7200 IN IPSECKEY ( 10 1 5 218 192.0.2.38 219 AQOrXJxB56Q28iOO43Va36elIFFKc/QB2orIeL94BdC5X4idFQZjSpsZ 220 Th48wKVXUE9xjwUkwR4R4/+1vjNN7KFp9fcqa2OxgjsoGqCn+3OPR8La 221 9uyvZg0OBuSTj3qkbh/2HacAUJ7vqvjQ3W8Wj6sMXtTueR8NNcdSzJh1 222 49ch3zqfiXrxxna8+8UEDQaRR9KOPiSvXb2KjnuDan6hDKOT4qTZRRRC 223 MWwnNQ9zPIMNbLBp0rNcZ+ZGFg2ckWtWh5yhv1iXYLV2vmd9DB6d4Dv8 224 cW7scc3rPmDXpYR6APqPBRHlcbenfHCt+oCkEWse8OQhMM56KODIVQq3 225 fejrfi1H ) 227 An example of a node, 192.0.2.38 that has published its key only. 229 38.2.0.192.in-addr.arpa. 7200 IN IPSECKEY ( 10 0 5 230 . 231 AQOrXJxB56Q28iOO43Va36elIFFKc/QB2orIeL94BdC5X4idFQZjSpsZ 232 Th48wKVXUE9xjwUkwR4R4/+1vjNN7KFp9fcqa2OxgjsoGqCn+3OPR8La 233 9uyvZg0OBuSTj3qkbh/2HacAUJ7vqvjQ3W8Wj6sMXtTueR8NNcdSzJh1 234 49ch3zqfiXrxxna8+8UEDQaRR9KOPiSvXb2KjnuDan6hDKOT4qTZRRRC 235 MWwnNQ9zPIMNbLBp0rNcZ+ZGFg2ckWtWh5yhv1iXYLV2vmd9DB6d4Dv8 236 cW7scc3rPmDXpYR6APqPBRHlcbenfHCt+oCkEWse8OQhMM56KODIVQq3 237 fejrfi1H ) 239 An example of a node, 192.0.2.38 that has delegated authority to the 240 node 192.0.2.3. 242 38.2.0.192.in-addr.arpa. 7200 IN IPSECKEY ( 10 1 5 243 192.0.2.3 244 AQOrXJxB56Q28iOO43Va36elIFFKc/QB2orIeL94BdC5X4idFQZjSpsZ 245 Th48wKVXUE9xjwUkwR4R4/+1vjNN7KFp9fcqa2OxgjsoGqCn+3OPR8La 246 9uyvZg0OBuSTj3qkbh/2HacAUJ7vqvjQ3W8Wj6sMXtTueR8NNcdSzJh1 247 49ch3zqfiXrxxna8+8UEDQaRR9KOPiSvXb2KjnuDan6hDKOT4qTZRRRC 248 MWwnNQ9zPIMNbLBp0rNcZ+ZGFg2ckWtWh5yhv1iXYLV2vmd9DB6d4Dv8 249 cW7scc3rPmDXpYR6APqPBRHlcbenfHCt+oCkEWse8OQhMM56KODIVQq3 250 fejrfi1H ) 252 An example of a node, 192.0.1.38 that has delegated authority to the 253 node with the identity "mygateway.example.com". 255 38.1.0.192.in-addr.arpa. 7200 IN IPSECKEY ( 10 3 5 256 mygateway.example.com. 257 AQOrXJxB56Q28iOO43Va36elIFFKc/QB2orIeL94BdC5X4idFQZjSpsZ 258 Th48wKVXUE9xjwUkwR4R4/+1vjNN7KFp9fcqa2OxgjsoGqCn+3OPR8La 259 9uyvZg0OBuSTj3qkbh/2HacAUJ7vqvjQ3W8Wj6sMXtTueR8NNcdSzJh1 260 49ch3zqfiXrxxna8+8UEDQaRR9KOPiSvXb2KjnuDan6hDKOT4qTZRRRC 261 MWwnNQ9zPIMNbLBp0rNcZ+ZGFg2ckWtWh5yhv1iXYLV2vmd9DB6d4Dv8 262 cW7scc3rPmDXpYR6APqPBRHlcbenfHCt+oCkEWse8OQhMM56KODIVQq3 263 fejrfi1H ) 265 An example of a node, 2001:0DB8:0200:1:210:f3ff:fe03:4d0 that has 266 delegated authority to the node 2001:0DB8:c000:0200:2::1 268 $ORIGIN 1.0.0.0.0.0.2.8.B.D.0.1.0.0.2.ip6.int. 269 0.d.4.0.3.0.e.f.f.f.3.f.0.1.2.0 7200 IN IPSECKEY ( 10 2 5 270 2001:0DB8:0:8002::2000:1 271 AQOrXJxB56Q28iOO43Va36elIFFKc/QB2orIeL94BdC5X4idFQZjSpsZ 272 Th48wKVXUE9xjwUkwR4R4/+1vjNN7KFp9fcqa2OxgjsoGqCn+3OPR8La 273 9uyvZg0OBuSTj3qkbh/2HacAUJ7vqvjQ3W8Wj6sMXtTueR8NNcdSzJh1 274 49ch3zqfiXrxxna8+8UEDQaRR9KOPiSvXb2KjnuDan6hDKOT4qTZRRRC 275 MWwnNQ9zPIMNbLBp0rNcZ+ZGFg2ckWtWh5yhv1iXYLV2vmd9DB6d4Dv8 276 cW7scc3rPmDXpYR6APqPBRHlcbenfHCt+oCkEWse8OQhMM56KODIVQq3 277 fejrfi1H ) 279 4. Security Considerations 281 This entire memo pertains to the provision of public keying material 282 for use by key management protocols such as ISAKMP/IKE (RFC2407) [7]. 284 The IPSECKEY resource record contains information that SHOULD be 285 communicated to the end client in an integral fashion - i.e. free 286 from modification. The form of this channel is up to the consumer of 287 the data - there must be a trust relationship between the end 288 consumer of this resource record and the server. This relationship 289 may be end-to-end DNSSEC validation, a TSIG or SIG(0) channel to 290 another secure source, a secure local channel on the host, or some 291 combination of the above. 293 The keying material provided by the IPSECKEY resource record is not 294 sensitive to passive attacks. The keying material may be freely 295 disclosed to any party without any impact on the security properties 296 of the resulting IPsec session: IPsec and IKE provide for defense 297 against both active and passive attacks. 299 Any use of this resource record MUST carefully document their trust 300 model, and why the trust model of DNSSEC is appropriate, if that is 301 the secure channel used. 303 4.1 Active attacks against unsecured IPSECKEY resource records 305 This section deals with active attacks against the DNS. These 306 attacks require that DNS requests and responses be intercepted and 307 changed. DNSSEC is designed to defend against attacks of this kind. 309 The first kind of active attack is when the attacker replaces the 310 keying material with either a key under its control, or with garbage. 312 If the attacker is not able to mount a subsequent man-in-the-middle 313 attack on the IKE negotiation after replacing the public key, then 314 this will result in a denial of service, as the authenticator used by 315 IKE would fail. 317 If the attacker is able to both to mount active attacks against DNS 318 and is also in a position to perform a man-in-the-middle attack on 319 IKE and IPsec negotiations, then the attacker will be in a position 320 to compromise the resulting IPsec channel. Note that an attacker 321 must be able to perform active DNS attacks on both sides of the IKE 322 negotiation in order for this to succeed. 324 The second kind of active attack is one in which the attacker 325 replaces the the gateway address to point to a node under the 326 attacker's control. The attacker can then either replace the public 327 key or remove it, thus providing an IPSECKEY record of its own to 328 match the gateway address. 330 This later form creates a simple man-in-the-middle since the attacker 331 can then create a second tunnel to the real destination. Note that, 332 as before, this requires that the attacker also mount an active 333 attack against the responder. 335 Note that the man-in-the-middle can not just forward cleartext 336 packets to the original destination. While the destination may be 337 willing to speak in the clear, replying to the original sender, the 338 sender will have already created a policy expecting ciphertext. 339 Thus, the attacker will need to intercept traffic from both sides. 341 Note that the danger here only applies to cases where the gateway 342 field of the IPSECKEY RR indicates a different entity than the owner 343 name of the IPSECKEY RR. In cases where the end-to-end integrity of 344 the IPSECKEY RR is suspect, the end client MUST restrict its use of 345 the IPSECKEY RR to cases where the RR owner name matches the content 346 of the gateway field. 348 5. IANA Considerations 350 IANA is asked to assign a resource record type number from the normal 351 resource record number space. 353 The algorithm field does not require any IANA action, as it is 354 inherited from DNS KEY algorithm values. 356 6. Acknowledgments 358 My thanks to Paul Hoffman, Sam Weiler, Jean-Jacques Puig, and Olafur 359 Gurmundsson who reviewed this document carefully. Additional thanks 360 to Olafur Gurmundsson for a reference implementation. 362 Normative references 364 [1] Mockapetris, P., "Domain names - concepts and facilities", STD 365 13, RFC 1034, November 1987. 367 [2] Mockapetris, P., "Domain names - implementation and 368 specification", STD 13, RFC 1035, November 1987. 370 [3] Bradner, S., "The Internet Standards Process -- Revision 3", BCP 371 9, RFC 2026, October 1996. 373 [4] Eastlake, D. and C. Kaufman, "Domain Name System Security 374 Extensions", RFC 2065, January 1997. 376 Non-normative references 378 [5] Thomson, S. and C. Huitema, "DNS Extensions to support IP 379 version 6", RFC 1886, December 1995. 381 [6] Bradner, S., "Key words for use in RFCs to Indicate Requirement 382 Levels", BCP 14, RFC 2119, March 1997. 384 [7] Piper, D., "The Internet IP Security Domain of Interpretation 385 for ISAKMP", RFC 2407, November 1998. 387 [8] Eastlake, D., "Domain Name System Security Extensions", RFC 388 2535, March 1999. 390 [9] Eastlake, D., "DSA KEYs and SIGs in the Domain Name System 391 (DNS)", RFC 2536, March 1999. 393 [10] Eastlake, D., "RSA/SHA-1 SIGs and RSA KEYs in the Domain Name 394 System (DNS)", RFC 3110, May 2001. 396 [11] Massey, D. and S. Rose, "Limiting the Scope of the KEY Resource 397 Record (RR)", RFC 3445, December 2002. 399 Author's Address 401 Michael C. Richardson 402 Sandelman Software Works 403 470 Dawson Avenue 404 Ottawa, ON K1Z 5V7 405 CA 407 EMail: mcr@sandelman.ottawa.on.ca 408 URI: http://www.sandelman.ottawa.on.ca/ 410 Full Copyright Statement 412 Copyright (C) The Internet Society (2003). All Rights Reserved. 414 This document and translations of it may be copied and furnished to 415 others, and derivative works that comment on or otherwise explain it 416 or assist in its implementation may be prepared, copied, published 417 and distributed, in whole or in part, without restriction of any 418 kind, provided that the above copyright notice and this paragraph are 419 included on all such copies and derivative works. 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