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RFC 2119 keyword, line 113: '...HCP DISCOVER message, it MUST sign the...' RFC 2119 keyword, line 116: '... SHOULD cache the resulting signatur...' RFC 2119 keyword, line 119: '... The client MUST include its propose...' RFC 2119 keyword, line 122: '... The client MUST include a parameter...' RFC 2119 keyword, line 129: '... The client SHOULD prefer DHCPOFFERs...' (25 more instances...) Miscellaneous warnings: ---------------------------------------------------------------------------- == The copyright year in the RFC 3978 Section 5.4 Copyright Line does not match the current year -- The document seems to lack a disclaimer for pre-RFC5378 work, but may have content which was first submitted before 10 November 2008. If you have contacted all the original authors and they are all willing to grant the BCP78 rights to the IETF Trust, then this is fine, and you can ignore this comment. If not, you may need to add the pre-RFC5378 disclaimer. (See the Legal Provisions document at https://trustee.ietf.org/license-info for more information.) -- The document date (February 23, 2003) is 7732 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) ** Obsolete normative reference: RFC 2537 (ref. '4') (Obsoleted by RFC 3110) ** Obsolete normative reference: RFC 3447 (ref. '5') (Obsoleted by RFC 8017) == Outdated reference: A later version (-13) exists of draft-ietf-dhc-fqdn-option-05 Summary: 5 errors (**), 0 flaws (~~), 3 warnings (==), 2 comments (--). Run idnits with the --verbose option for more detailed information about the items above. -------------------------------------------------------------------------------- 2 DHC T. Lemon 3 Internet-Draft nominum 4 Expires: August 24, 2003 M. Richardson 5 SSW 6 February 23, 2003 8 Securing DHCP with DNSSEC bourne public keys 9 draft-richardson-dhc-auth-sig0-00.txt 11 Status of this Memo 13 This document is an Internet-Draft and is in full conformance with 14 all provisions of Section 10 of RFC2026. 16 Internet-Drafts are working documents of the Internet Engineering 17 Task Force (IETF), its areas, and its working groups. Note that 18 other groups may also distribute working documents as Internet- 19 Drafts. 21 Internet-Drafts are draft documents valid for a maximum of six months 22 and may be updated, replaced, or obsoleted by other documents at any 23 time. It is inappropriate to use Internet-Drafts as reference 24 material or to cite them other than as "work in progress." 26 The list of current Internet-Drafts can be accessed at http:// 27 www.ietf.org/ietf/1id-abstracts.txt. 29 The list of Internet-Draft Shadow Directories can be accessed at 30 http://www.ietf.org/shadow.html. 32 This Internet-Draft will expire on August 24, 2003. 34 Copyright Notice 36 Copyright (C) The Internet Society (2003). All Rights Reserved. 38 Abstract 40 The abstract. 42 This document is intended as a standards track document. 44 Table of Contents 46 1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . . 3 47 2. Definition of RSA authentication option for DHCP . . . . . . . 4 48 3. Definition of DSA authentication option for DHCP . . . . . . . 5 49 4. Model of operation . . . . . . . . . . . . . . . . . . . . . . 6 50 5. Samples . . . . . . . . . . . . . . . . . . . . . . . . . . . 10 51 6. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 11 52 7. Acknowledgments . . . . . . . . . . . . . . . . . . . . . . . 12 53 Normative references . . . . . . . . . . . . . . . . . . . . . 13 54 Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . 13 55 Full Copyright Statement . . . . . . . . . . . . . . . . . . . 14 57 1. Introduction 59 [1] defines a method for authenticating DHCP messages. It does 60 provide for a way to do key management for the many relationships 61 that a DHCP server may have. 63 In particular, the scaling problem of pre-shared keys fails badly in 64 open networks such as those that occur at conferences such as IETF. 65 In the context of conferences, it is not just malicious attacks that 66 are a problem to the network, but also rogue DHCP servers present due 67 to misconfiguration on the part of attendees. 69 2. Definition of RSA authentication option for DHCP 71 --------------------------------------------------------------------- 73 The new algorithm type XX for the DHCP option is defined as follows: 75 0 1 2 3 76 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 77 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 78 | Code = 90 | Length | Protocol TBD | Algorithm=1 | 79 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 80 | RDM = 1 | Replay Detection (64 bits) | 81 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 82 | Replay cont. | 83 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 84 | Replay cont. | keyid of public key | | 85 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | 86 ~ ~ 87 | RSA signature | 88 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 90 Figure 1: RSA authentication option for DHCP 92 --------------------------------------------------------------------- 94 This section defines the contents of the Authentication Information 95 field of this payload. [5] defines the RSA signature algorithm. [4] 96 provides a more consise definition. The RSA signature is defined 97 with MD5 as the hash algorithm. 99 3. Definition of DSA authentication option for DHCP 101 a diagram of the auth section for DSA, i.e. with Algorithm=2. 103 4. Model of operation 105 4.1 Additions to client side state machine 107 Section 4.4 of [2] defines the state machine for the DHCP client. 109 4.2 Client INIT state changes 111 No changes to the transitions for this state. 113 When the client sends the DHCP DISCOVER message, it MUST sign the 114 request with its private key, including an authentication option in 115 the DISCOVER message in an option as defined above. The client 116 SHOULD cache the resulting signature such that it can retransmit it. 117 (XXX - is there any value in this? The xid will change each time). 119 The client MUST include its proposed fully-qualified domain name in a 120 client FQDN, as specified in [6]. 122 The client MUST include a parameter request list option that includes 123 the DHCP authentication option, and the Server Name option. 125 4.3 Client SELECTING state changes 127 No changes to the transitions for this state. 129 The client SHOULD prefer DHCPOFFERs that include a authentication 130 option that are signed by keys that the client currently has cached. 132 If no preferred offer is seen, then the client MUST select among the 133 offers in a non-deterministic manner (ideally, random). This step is 134 important so that a client that has been deceived into binding to the 135 wrong DHCP server will have a chance to select a different server. 137 A client SHOULD NOT assume that offers that do not include valid and 138 verifiable signature options are exclusively preferred. There may be 139 no DHCP security on the network in question, and attackers could keep 140 the client from ever selecting the "real", unauthenticated server. 141 (XXX - yet, if one can remember them all, one would prefer to try the 142 offers with signatures first) 144 Note that this behaviour differs from that described in point 2 of 145 section 5.5.1 of [1]. This is because a client may not be able to 146 determine the authenticity of the offer until after it has connected 147 to the network. Should an appropriate DHCP server key be pre- 148 configured, or cached, then the behaviour is the same. 150 4.4 Client REQUESTING state changes 152 A new state called "Provisionally BOUND" MUST be added. The system 153 will transition to this new state upon receipt of a DHCP ACK that 154 contains a DHCP authentication option, and a DHCP Server name option. 156 When sending the DHCP REQUEST to the server, it MUST also be signed. 157 The DHCP REQUEST MUST also include the same client FQDN as was sent 158 in the DISCOVER message. 160 XXX - should the DHCP Decline be signed? I think so. 162 4.5 Provisionally BOUND state 164 The provisionally bound state is operationally similar to the BOUND 165 state. The timers should be recorded as with the previous state. 166 Additional DHCP offers received should be discarded. 168 The system should be sufficiently configured with the provided IP 169 address such that DNS requests to the root name server(s) may be 170 done. If the system is going to be configured with the a DNS server 171 as specified in the Domain Name Server option of [3], and this name 172 server is directly reachable, it may be reasonable to defer any 173 additional system configuration until the BOUND state. Some systems 174 may not provide such a "partially configured" state. 176 In any case, if the system has any kind of system event that 177 indicates that it is on the network, this event SHOULD be deferred 178 until the BOUND state has been reached. 180 Upon entering this state, after performing the partial configuration, 181 the client MUST authenticate the DHCP ACK. To do this, if it does 182 not already have the public key of the DHCP server, it must look it 183 up. 185 The client MUST lookup the KEY resource record (subtype DNSSEC) 186 associated with the name provided by the server in its DHCP server 187 name option. The DNS lookup SHOULD be done with DNSSEC enabled. 189 {XXX - DHCP server name option. Is there such a thing? The original 190 idea was to lookup the KEY record in the reverse map (in-addr.arpa/ 191 ip6.arpa), based upon the IP address in the server identifier. Ted 192 suggested that we wanted to use FQDN, but I'm not sure where it will 193 get stored. Do we need a new option} 195 If the DHCP ACK can not be authenticated (either because the KEY can 196 not be retrieved, the DNSSEC does not authenticate the key, or 197 integrity check on the message fails), then the lease MUST be 198 discarded. The client transitions back to INIT state, having sent a 199 DHCPNAK to the server, and then halting the network. 201 XXX - Do we go back and authenticate the DHCP OFFER? 203 4.6 Client BOUND state changes 205 There is a new transition from the Provisionally BOUND state. 207 The only change in behaviour of this state is that when lease renewal 208 occurs, the DHCP REQUEST SHOULD be signed. This is done even if the 209 lease was not originally acquired through a signature, as it MAY be 210 that the server will adopt security in the interum. 212 4.7 Client RENEWING state changes 214 There is a new transition to the Provisionally BOUND state. 216 If a DHCP ACK is received that has a DHCP Authentication option in 217 it, then the client transitions to the Provisionally BOUND state 218 rather than directly back to the BOUND state. 220 4.8 Client REBINDING state changes 222 The system will transition to Provisionally BOUND upon receipt of a 223 DHCP ACK that contains a DHCP authentication option, and a DHCP 224 Server name option. 226 The broadcast DHCP REQUEST SHOULD contain an authentication option, 227 as with the one sent by state SELECTING. 229 4.9 Additions to server side state machine 231 Section 4.4 of [2] defines the state machine for the DHCP client. 233 4.9.1 DHCP DISCOVER processing changes 235 Upon receipt of a DHCP DISCOVER that includes an Authentication 236 option of the type defined in this document, then it MUST verify that 237 there is a provided client FQDN option, and that it is fully 238 qualified. 240 The server MUST then do a DNSSEC lookup on the provided FQDN, looking 241 for a KEY resource record (sub-type DNSSEC). The server SHOULD cache 242 this result for at least as long as the DHCP OFFER that will be made 243 would be valid for. The server MAY cache it for as long as the DNS 244 time to live value. 246 Having found a valid KEY (with the matching keyid), the server MAY 247 verify the signature at this point. If the server feels that it is 248 overloaded or under denial of service attack, it may defer 249 authentication at this step. 251 If appropriate authentication material is not found, then the request 252 SHOULD be treated as if none were present. If authentication 253 material was found, but the signature check fails, then the message 254 MUST be discarded. Audit entries SHOULD be made, including the keyid 255 that was used, and the computed vs actual MD5 checks. 257 4.9.2 DHCP REQUEST processing changes 259 Upon receipt of a DHCP REQUEST that includes an Authentication option 260 of the type defined in this document, then it MUST verify that there 261 is a provided client FQDN option, and that it is fully qualified. 263 The server MAY have already cached the KEY record associated with 264 this FQDN. If it has not, then it MUST lookup the record again, as 265 described above. 267 The signature MUST be authenticated in this step. 269 The server MAY then insert the provided FQDN into the reverse map 270 using dynamic update, as described in [6]. 272 If the client has requested it, via the DHCP IPSECKEY option, then 273 the server should also insert the public key taken from the FQDN into 274 the reverse map. 276 4.9.3 DHCP DECLINE processing changes 278 XXX - unclear yet. 280 4.9.4 Annotated exchange between client and server 281 5. Samples 283 5.1 Sample RSA keys and signature options for client 285 Using a private key of: XXXX, having a public key value of: YYYY. We 286 produced the following authentication option: 288 5.2 Sample DSA keys and signature options for client 290 Using a private key of: XXXX, having a public key value of: YYYY. We 291 produced the following authentication option: 293 5.3 Sample DSA keys and signature options for server 295 Using a private key of: XXXX, having a public key value of: YYYY. We 296 produced the following authentication option: 298 5.4 Sample DSA keys and signature options for server 300 Using a private key of: XXXX, having a public key value of: YYYY. We 301 produced the following authentication option: 303 6. IANA Considerations 305 IANA will need to assign X. 307 7. Acknowledgments 309 Original ideas due to Randy Bush, ... 311 Normative references 313 [1] Droms, R., Editor, Arbaugh, W. and Editor, "Authentication for 314 DHCP Messages", RFC 3118, June 2001. 316 [2] Droms, R., "Dynamic Host Configuration Protocol", RFC 2131, 317 March 1997. 319 [3] Alexander, S. and R. Droms, "DHCP Options and BOOTP Vendor 320 Extensions", RFC 2132, March 1997. 322 [4] Eastlake, D., "RSA/MD5 KEYs and SIGs in the Domain Name System 323 (DNS)", RFC 2537, March 1999. 325 [5] Jonsson, J. and B. Kaliski, "Public-Key Cryptography Standards 326 (PKCS) #1: RSA Cryptography Specifications Version 2.1", RFC 327 3447, February 2003. 329 [6] Stapp, M. and Y. Rekhter, "The DHCP Client FQDN Option", ID 330 internet-draft (draft-ietf-dhc-fqdn-option-05.txt), November 331 2002. 333 Authors' Addresses 335 Ted Lemon 336 Nominum 337 Some City, AZ 338 USA 340 EMail: Ted.Lemon@nominum.com 342 Michael C. Richardson 343 Sandelman Software Works 344 470 Dawson Avenue 345 Ottawa, ON K1Z 5V7 346 CA 348 EMail: mcr@sandelman.ottawa.on.ca 349 URI: http://www.sandelman.ottawa.on.ca/ 351 Full Copyright Statement 353 Copyright (C) The Internet Society (2003). All Rights Reserved. 355 This document and translations of it may be copied and furnished to 356 others, and derivative works that comment on or otherwise explain it 357 or assist in its implementation may be prepared, copied, published 358 and distributed, in whole or in part, without restriction of any 359 kind, provided that the above copyright notice and this paragraph are 360 included on all such copies and derivative works. However, this 361 document itself may not be modified in any way, such as by removing 362 the copyright notice or references to the Internet Society or other 363 Internet organizations, except as needed for the purpose of 364 developing Internet standards in which case the procedures for 365 copyrights defined in the Internet Standards process must be 366 followed, or as required to translate it into languages other than 367 English. 369 The limited permissions granted above are perpetual and will not be 370 revoked by the Internet Society or its successors or assigns. 372 This document and the information contained herein is provided on an 373 "AS IS" basis and THE INTERNET SOCIETY AND THE INTERNET ENGINEERING 374 TASK FORCE DISCLAIMS ALL WARRANTIES, EXPRESS OR IMPLIED, INCLUDING 375 BUT NOT LIMITED TO ANY WARRANTY THAT THE USE OF THE INFORMATION 376 HEREIN WILL NOT INFRINGE ANY RIGHTS OR ANY IMPLIED WARRANTIES OF 377 MERCHANTABILITY OR FITNESS FOR A PARTICULAR PURPOSE. 379 Acknowledgement 381 Funding for the RFC Editor function is currently provided by the 382 Internet Society.