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Checking references for intended status: Informational ---------------------------------------------------------------------------- == Outdated reference: A later version (-10) exists of draft-ietf-sidr-pfx-validate-00 Summary: 1 error (**), 0 flaws (~~), 3 warnings (==), 2 comments (--). Run idnits with the --verbose option for more detailed information about the items above. -------------------------------------------------------------------------------- 2 Secure Inter-Domain Routing (SIDR) G. Huston 3 Internet-Draft G. Michaelson 4 Intended status: Informational APNIC 5 Expires: April 13, 2011 October 10, 2010 7 Validation of Route Origination using the Resource Certificate PKI and 8 ROAs 9 draft-ietf-sidr-roa-validation-07.txt 11 Abstract 13 This document defines the semantics of a Route Origin Authorization 14 (ROA) in terms of the context of an application of the Resource 15 Public Key Infrastructure to validate the origination of routes 16 advertised in the Border Gateway Protocol. 18 Status of this Memo 20 This Internet-Draft is submitted in full conformance with the 21 provisions of BCP 78 and BCP 79. 23 Internet-Drafts are working documents of the Internet Engineering 24 Task Force (IETF). Note that other groups may also distribute 25 working documents as Internet-Drafts. The list of current Internet- 26 Drafts is at http://datatracker.ietf.org/drafts/current/. 28 Internet-Drafts are draft documents valid for a maximum of six months 29 and may be updated, replaced, or obsoleted by other documents at any 30 time. It is inappropriate to use Internet-Drafts as reference 31 material or to cite them other than as "work in progress." 33 This Internet-Draft will expire on April 13, 2011. 35 Copyright Notice 37 Copyright (c) 2010 IETF Trust and the persons identified as the 38 document authors. All rights reserved. 40 This document is subject to BCP 78 and the IETF Trust's Legal 41 Provisions Relating to IETF Documents 42 (http://trustee.ietf.org/license-info) in effect on the date of 43 publication of this document. Please review these documents 44 carefully, as they describe your rights and restrictions with respect 45 to this document. Code Components extracted from this document must 46 include Simplified BSD License text as described in Section 4.e of 47 the Trust Legal Provisions and are provided without warranty as 48 described in the Simplified BSD License. 50 Table of Contents 52 1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . . 3 53 2. ROA Validation Outcomes for a Route . . . . . . . . . . . . . . 3 54 3. Applying Validation Outcomes to Route Selection . . . . . . . . 6 55 4. Disavowal of Routing Origination . . . . . . . . . . . . . . . 7 56 5. Route Validation Lifetime . . . . . . . . . . . . . . . . . . . 7 57 6. Security Considerations . . . . . . . . . . . . . . . . . . . . 8 58 7. IANA Considerations . . . . . . . . . . . . . . . . . . . . . . 8 59 8. Acknowledgements . . . . . . . . . . . . . . . . . . . . . . . 8 60 9. References . . . . . . . . . . . . . . . . . . . . . . . . . . 9 61 9.1. Normative References . . . . . . . . . . . . . . . . . . . 9 62 9.2. Informative References . . . . . . . . . . . . . . . . . . 9 63 Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . . 9 65 1. Introduction 67 This document defines the semantics of a Route Origin Authorization 68 (ROA) in terms of the context of an application of the Resource 69 Public Key Infrastructure (RPKI) [I-D.ietf-sidr-arch] to validate the 70 origination of routes advertised in the Border Gateway Protocol (BGP) 71 [RFC4271]. 73 The RPKI is based on a hierarchy of Resource Certificates that are 74 aligned to the Internet number resource allocation structure. 75 Resource Certificates are X.509 certificates that conform to the PKIX 76 profile [RFC5280], and to the extensions for IP addresses and AS 77 identifiers [RFC3779]. A Resource Certificate describes an action by 78 an issuer that binds a list of IP address blocks and Autonomous 79 System (AS) numbers to the Subject of a certificate, identified by 80 the unique association of the Subject's private key with the public 81 key contained in the Resource Certificate. The RPKI is structured 82 such that each current Resource Certificate matches a current 83 resource allocation or assignment. This is further described in 84 [I-D.ietf-sidr-arch]. 86 ROAs are digitally signed objects that bind an address to an AS 87 number, signed by the address holder. A ROA provides a means of 88 verifying that an IP address block holder has authorized a particular 89 AS to originate routes in the inter-domain routing environment for 90 that address block. ROAs are described in 91 [I-D.ietf-sidr-roa-format]. ROAs are intended to fit within the 92 requirements for adding security to inter-domain routing. 94 This document describes the semantic interpretation of a ROA, with 95 particular reference to application in inter-domain routing relating 96 to the origination of routes, and the intended scope of the authority 97 that is conveyed in the ROA. 99 2. ROA Validation Outcomes for a Route 101 A "route" is unit of information that associates a set of 102 destinations described by an IP address prefix with a set of 103 attributes of a path to those destinations, as defined in section 1.1 104 of [RFC4271]. 106 A route's "origin AS" is defined as follows: If the final path 107 segment of the AS_PATH is of type AS_SEQUENCE, the "origin AS" is the 108 first element of the sequence (i.e. the AS in the rightmost position 109 with respect to the position of octets in the protocol message). If 110 the final path segment of the AS_PATH is of type AS_SET, indicating 111 that the route is an aggregate, then the origin AS is taken as the AS 112 component of the AGGREGATOR attribute [RFC4271], if present. 113 Otherwise the route's origin AS cannot be determined. 115 In terms of validation of a route in the context of a routing 116 environment, the address prefix value and the origin AS are used in 117 the ROA validation operation. 119 It is assumed here that a Relying Party (RP) has access to a local 120 cache of the complete set of valid ROAs when performing validation of 121 a route. (Valid ROAs are defined as ROAs that are determined to be 122 syntactically correct and are signed using a signature that can be 123 verified using the RPKI, as described in [I-D.ietf-sidr-roa-format].) 124 The RP needs to match a route to one or more candidate valid ROAs in 125 order to determine a validation outcome, which, in turn, can be used 126 to determine the appropriate local actions to perform on the route. 128 This approach to route origination validation uses a generic model of 129 "positive" attestation that has an associated inference that routes 130 that cannot be validated within the RPKI framework would 131 conventionally be interpreted by a RP as "invalid". However, the 132 considerations of accommodating environments of partial adoption of 133 the use of ROAs, where only a subset of validly advertised address 134 prefixes have associated published ROAs within the structure of the 135 RPKI, imply some modification to this model of positive attestation. 136 In the context of route validation it is assumed that once an address 137 prefix is described in a ROA, then this ROA specifically encompasses 138 all address prefixes that are more specific than that described in 139 the ROA. Thus, any route for a more specific address prefix than 140 that described by any valid ROA that does not itself have a matching 141 valid ROA can be considered to be "invalid". However, routes objects 142 for address prefixes that are not fully described by any single ROA, 143 i.e., those route objects whose address prefixes may be an aggregate 144 of address prefixes described in a valid ROA, or have address 145 prefixes where there is no intersection with any ROA, and are not 146 matched by any ROA and are not a more specific of any ROA, cannot be 147 reliably classified as "invalid" in a partial deployment scenario. 148 Such routes have a validation outcome of "unknown". 150 An abstract attribute of a route can be determined as the outcome of 151 this validation procedure, namely a "validity state" 152 [I-D.ietf-sidr-pfx-validate]. The "validity state" of a route, with 153 a prefix and an origin AS as defined above, when using single ROA for 154 determining this validity state is summarized in the following table: 156 Route matching non-matching 157 Prefix AS-> AS AS 158 V +---------+---------+ 159 Non- | unknown | unknown | 160 Intersecting | | | 161 +---------+---------+ 162 Covering | unknown | unknown | 163 Aggregate | | | 164 +---------+---------+ 165 match ROA | valid | invalid | 166 prefix | | | 167 +---------+---------+ 168 More | | | 169 Specific | invalid | invalid | 170 than ROA | | | 171 +---------+---------+ 173 Route's Validity State 175 In an environment of a collection of valid ROAs, a route's validity 176 state is considered to be "valid" if any ROA provides a "valid" 177 outcome. It's validity state is considered to be "invalid" if one 178 (or more) ROAs provide an "invalid" outcome and no ROAs provide a 179 "valid" outcome. Its validity state is considered to be "unknown" 180 (or, synonymously, "not found" [I-D.ietf-sidr-pfx-validate] when no 181 valid ROA can produce either a "valid" or an "invalid" validity state 182 outcome. 184 A route validity state is defined by the following procedure: 186 1. Select all valid ROAs that include a ROAIPAddress value that 187 either matches, or is a covering aggregate of, the address 188 prefix in the route. This selection forms the set of 189 "candidate ROAs." 191 2. If the set of candidate ROAs is empty, then the procedure 192 stops with an outcome of "unknown" (or, synonymously, "not 193 found", as used in [I-D.ietf-sidr-pfx-validate]). 195 3. If the route's origin AS can be determined and any of the set 196 of candidate ROAs has an asID value that matches the origin AS 197 in the route, and the route's address prefix matches a 198 ROAIPAddress in the ROA (where "match" is defined as where the 199 route's address precisely matches the ROAIPAddress, or where 200 the ROAIPAddress includes a maxLength element, and the route's 201 address prefix is a more specific prefix of the ROAIPAddress, 202 and the route's address prefix length value is less than or 203 equal to the ROAIPAddress maxLength value) then the procedure 204 halts with an outcome of "valid". 206 4. Otherwise, the procedure halts with an outcome of "invalid". 208 3. Applying Validation Outcomes to Route Selection 210 Within the framework of the abstract model of the operation of inter- 211 domain routing using BGP [RFC4271], a received prefix announcement 212 from a routing peer is compared to all announcements for this prefix 213 received from other routing peers and a route selection procedure is 214 used to select the "best" route from this candidate set. 216 The route's validity state, described in Section 2, of "valid", 217 "invalid" or "unknown" may be used as part of the determination of 218 the local degree of preference, in which case the local order of 219 preference is as follows: 220 "valid" is to be preferred over 221 "unknown", which is to be preferred over 222 "invalid". 224 It is a matter of local routing policy as to the actions to be 225 undertaken by a routing entity in processing those routes with 226 "unknown" validity states. Due to considerations of partial use of 227 ROAs in heterogeneous environments, such as in the public Internet, 228 it is advised that local policy settings should not result in 229 "unknown" validity state outcomes being considered as sufficient 230 grounds to reject a route outright from further consideration as a 231 local "best" route. 233 It is a matter of local routing policy as to whether routes with an 234 "invalid" validity state are considered to be ineligible for further 235 consideration in a route selection process. A possible consideration 236 here is one of potential circularity of dependence: If the 237 authoritative publication point of the repository of ROAs, or that of 238 any certificate used in relation to an address prefix, is located at 239 an address that lies within the address prefix described in a ROA, 240 then the repository can only be accessed by the RP once a route for 241 the prefix has been accepted by the RP's local routing domain. It is 242 also noted that the propagation time of RPKI objects may be different 243 to the propagation time of routes, and that routes may be learned by 244 an RP's routing system before the RP's local RPKI repository cache 245 picks up the associated ROAs and recognises them as having a validity 246 state of "valid" within the RPKI. 248 4. Disavowal of Routing Origination 250 A ROA is a positive attestation that a prefix holder has authorized 251 an AS to originate a route for this prefix into the inter-domain 252 routing system. It is possible for a prefix holder to construct an 253 authorization where no valid AS has been granted any such authority 254 to originate a route for an address prefix. This is achieved by 255 using a ROA where the ROA's subject AS is one that must not be used 256 in any routing context. Specifically, AS 0 is reserved by the IANA 257 such that it may be used to identify non-routed networks 258 [IANA.AS-Registry]. 260 A ROA with a subject of AS 0 (AS0-ROA) is an attestation by the 261 holder of a prefix that the prefix described in the ROA, and any more 262 specific prefix, should not be used in a routing context. 264 The route validation procedure, described in Section 2, will provide 265 a "valid" outcome if any ROA matches the address prefix and origin 266 AS, even if other valid ROAs would provide an "invalid" validation 267 outcome if used in isolation. Consequently, an AS0-ROA has a lower 268 relative preference than any other ROA that has a routable AS as its 269 subject. This allows a prefix holder to use an AS0-ROA to declare a 270 default condition that any route that is equal to, or more specific 271 than the prefix to be considered to be invalid, while also allowing 272 other concurrently issued ROAs to describe valid origination 273 authorizations for more specific prefixes. 275 By convention, an AS0-ROA should have a maxLength value of 32 for 276 IPv4 addresses and a maxlength value of 128 for IPv6 addresses, 277 although in terms of route validation the same outcome would be 278 achieved with any valid maxLength value, or even if the maxLength 279 element were to be omitted from the ROA. 281 Also by convention, an AS0-ROA should be the only ROA issued for a 282 given address prefix, although again this is not a strict 283 requirement. An AS0-ROA MAY coexist with ROAs that have different 284 subject AS values, although in such cases the presence or otherwise 285 of the AS0-ROA does not alter the route's validity state in any way. 287 5. Route Validation Lifetime 289 The "lifetime" of a validation outcome refers to the time period 290 during which the original validation outcome can be still applied. 291 The implicit assumption here is that when the validation lifetime 292 expires the routing object should be re-tested for validity. 294 The validation lifetime for a ROA is controlled by the Valid times 295 specified in the End Entity (EE) Certificate used to sign the ROA, 296 and the valid times of those certificates in the certification path 297 used to validate the EE Certificate. A ROA validation "expires" at 298 the Validity To field of the signing EE certificate, or at such a 299 time when there is no certification path that can validate the ROA. 300 A ROA issuer may elect to prematurely invalidate a ROA by revoking 301 the EE certificate that was used to sign the ROA. 303 6. Security Considerations 305 ROA issuers should be aware of the validation implication in issuing 306 a ROA, in that a ROA implicitly invalidates all routes that have more 307 specific prefixes with a prefix length greater than maxLength, and 308 all originating AS's other than the AS listed in the collection of 309 ROAs for this prefix. 311 A conservative operational practice would be to ensure the issuing of 312 ROAs for all more specific prefixes with distinct origination AS's 313 prior to the issuing of ROAs for larger encompassing address blocks, 314 in order to avoid inadvertent invalidation of valid routes during ROA 315 generation. 317 ROA issuers should also be aware that if they generate a ROA for one 318 origin AS, then if the address prefix holder authorises multiple AS's 319 to originate routes for a given address prefix, then is necessary for 320 a ROA be generated for every such authorized AS. 322 7. IANA Considerations 324 [There are no IANA Considerations.] 326 8. Acknowledgements 328 The authors would like to acknowledge the helpful contributions of 329 John Scudder and Stephen Kent in preparing this document, and also 330 the contributions of many members of the SIDR Working Group in 331 response to presentations of this material in SIDR WG sessions. The 332 authors also acknowledge prior work undertaken by Tony Bates, Randy 333 Bush, Tony Li, and Yakov Rekhter as the validation outcomes described 334 here reflect the authentication outcomes and semantics of origin AS 335 verification described in [exI-D.bates]. A number of validation 336 concepts relating to a route's "validity state" presented in 337 [I-D.ietf-sidr-pfx-validate], edited by Pradosh Mohapatra et al, have 338 be used in this document. 340 9. References 342 9.1. Normative References 344 [I-D.ietf-sidr-arch] 345 Lepinski, M. and S. Kent, "An Infrastructure to Support 346 Secure Internet Routing", draft-ietf-sidr-arch (work in 347 progress), October 2009. 349 [I-D.ietf-sidr-roa-format] 350 Lepinski, M., Kent, S., and D. Kong, "An Infrastructure to 351 Support Secure Internet Routing", 352 draft-ietf-sidr-roa-format (work in progress), 353 October 2009. 355 [RFC3779] Lynn, C., Kent, S., and K. Seo, "X.509 Extensions for IP 356 Addresses and AS Identifiers", RFC 3779, June 2004. 358 [RFC4271] Rekhter, Y., Li, T., and S. Hares, "A Border Gateway 359 Protocol 4 (BGP-4)", RFC 4271, January 2006. 361 [RFC5280] Cooper, D., Santesson, S., Farrell, S., Boeyen, S., 362 Housley, R., and W. Polk, "Internet X.509 Public Key 363 Infrastructure Certificate and Certificate Revocation List 364 (CRL) Profile", RFC 5280, May 2008. 366 9.2. Informative References 368 [I-D.ietf-sidr-pfx-validate] 369 Mohapatra, P., Scudder, J., Ward, D., Bush, R., and R. 370 Austein, "BGP Prefix Origin Validation", 371 draft-ietf-sidr-pfx-validate-00 (work in progress), 372 July 2010. 374 [IANA.AS-Registry] 375 IANA, "IANA Autonomous System Number Registry", 376 March 2010. 378 [exI-D.bates] 379 Bates, T., Bush, R., Li, T., and Y. Rekhter, "DNS-based 380 NLRI origin AS verification in BGP", 381 draft-bates-bgp4-nlri-orig-verif-00.txt (work in 382 progress), January 1998. 384 Authors' Addresses 386 Geoff Huston 387 Asia Pacific Network Information Centre 389 Email: gih@apnic.net 391 George Michaelson 392 Asia Pacific Network Information Centre 394 Email: ggm@apnic.net