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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for intended status: Informational ---------------------------------------------------------------------------- == Outdated reference: A later version (-10) exists of draft-ietf-sidr-pfx-validate-00 Summary: 1 error (**), 0 flaws (~~), 3 warnings (==), 2 comments (--).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: May 15, 2011 November 11, 2010 7 Validation of Route Origination using the Resource Certificate PKI and 8 ROAs 9 draft-ietf-sidr-roa-validation-10.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 May 15, 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 AS_PATH contains a path segment of type AS_SET, indicating that 111 the route is an aggregate, then the "origin AS" cannot be determined. 113 In terms of validation of a route in the context of a routing 114 environment, the address prefix value and the origin AS are used in 115 the ROA validation operation. 117 It is assumed here that a Relying Party (RP) has access to a local 118 cache of the complete set of valid ROAs when performing validation of 119 a route. (Valid ROAs are defined as ROAs that are determined to be 120 syntactically correct and are signed using a signature that can be 121 verified using the RPKI, as described in [I-D.ietf-sidr-roa-format].) 122 The RP needs to match a route to one or more candidate valid ROAs in 123 order to determine a validation outcome, which, in turn, can be used 124 to determine the appropriate local actions to perform on the route. 126 This approach to route origination validation uses a generic model of 127 "positive" attestation that has an associated inference that routes 128 that cannot be validated within the RPKI framework would 129 conventionally be interpreted by an RP as "invalid". However, the 130 considerations of accommodating environments of partial adoption of 131 the use of ROAs, where only a subset of validly advertised address 132 prefixes have associated published ROAs within the structure of the 133 RPKI, imply some modification to this model of positive attestation. 134 In the context of route validation it is assumed that once an address 135 prefix is described in a ROA, then this ROA specifically encompasses 136 all address prefixes that are more specific than that described in 137 the ROA. Thus, any route for a more specific address prefix than 138 that described by any valid ROA that does not itself have a matching 139 valid ROA can be considered to be "invalid". However, routes objects 140 for address prefixes that are not fully described by any single ROA, 141 i.e., those route objects whose address prefixes may be an aggregate 142 of address prefixes described in a valid ROA, or have address 143 prefixes where there is no intersection with any ROA, and are not 144 matched by any ROA and are not a more specific of any ROA, cannot be 145 reliably classified as "invalid" in a partial deployment scenario. 146 Such routes have a validation outcome of "unknown". 148 An abstract attribute of a route can be determined as the outcome of 149 this validation procedure, namely a "validity state" 150 [I-D.ietf-sidr-pfx-validate]. The "validity state" of a route, with 151 a prefix and an origin AS as defined above, when using single ROA for 152 determining this validity state is summarized in the following table: 154 Route matching non-matching 155 Prefix AS-> AS AS 156 V +---------+---------+ 157 Non- | unknown | unknown | 158 Intersecting | | | 159 +---------+---------+ 160 Covering | unknown | unknown | 161 Aggregate | | | 162 +---------+---------+ 163 match ROA | valid | invalid | 164 prefix | | | 165 +---------+---------+ 166 More | | | 167 Specific | invalid | invalid | 168 than ROA | | | 169 +---------+---------+ 171 Route's Validity State 173 In an environment of a collection of valid ROAs, a route's validity 174 state is considered to be "valid" if any ROA provides a "valid" 175 outcome. It's validity state is considered to be "invalid" if one 176 (or more) ROAs provide an "invalid" outcome and no ROAs provide a 177 "valid" outcome. Its validity state is considered to be "unknown" 178 (or, synonymously, "not found" [I-D.ietf-sidr-pfx-validate] when no 179 valid ROA can produce either a "valid" or an "invalid" validity state 180 outcome. 182 A route validity state is defined by the following procedure: 184 1. Select all valid ROAs that include a ROAIPAddress value that 185 either matches, or is a covering aggregate of, the address 186 prefix in the route. This selection forms the set of 187 "candidate ROAs." 189 2. If the set of candidate ROAs is empty, then the procedure 190 stops with an outcome of "unknown" (or, synonymously, "not 191 found", as used in [I-D.ietf-sidr-pfx-validate]). 193 3. If the route's origin AS can be determined and any of the set 194 of candidate ROAs has an asID value that matches the origin AS 195 in the route, and the route's address prefix matches a 196 ROAIPAddress in the ROA (where "match" is defined as where the 197 route's address precisely matches the ROAIPAddress, or where 198 the ROAIPAddress includes a maxLength element, and the route's 199 address prefix is a more specific prefix of the ROAIPAddress, 200 and the route's address prefix length value is less than or 201 equal to the ROAIPAddress maxLength value) then the procedure 202 halts with an outcome of "valid". 204 4. Otherwise, the procedure halts with an outcome of "invalid". 206 3. Applying Validation Outcomes to Route Selection 208 Within the framework of the abstract model of the operation of inter- 209 domain routing using BGP [RFC4271], a received prefix announcement 210 from a routing peer is compared to all announcements for this prefix 211 received from other routing peers and a route selection procedure is 212 used to select the "best" route from this candidate set. 214 The route's validity state, described in Section 2, of "valid", 215 "invalid" or "unknown" may be used as part of the determination of 216 the local degree of preference, in which case the local order of 217 preference is as follows: 218 "valid" is to be preferred over 219 "unknown", which is to be preferred over 220 "invalid". 222 It is a matter of local routing policy as to the actions to be 223 undertaken by a routing entity in processing those routes with 224 "unknown" validity states. Due to considerations of partial use of 225 ROAs in heterogeneous environments, such as in the public Internet, 226 it is advised that local policy settings should not result in 227 "unknown" validity state outcomes being considered as sufficient 228 grounds to reject a route outright from further consideration as a 229 local "best" route. 231 It is a matter of local routing policy as to whether routes with an 232 "invalid" validity state are considered to be ineligible for further 233 consideration in a route selection process. A possible consideration 234 here is one of potential circularity of dependence: If the 235 authoritative publication point of the repository of ROAs, or that of 236 any certificate used in relation to an address prefix, is located at 237 an address that lies within the address prefix described in a ROA, 238 then the repository can only be accessed by the RP once a route for 239 the prefix has been accepted by the RP's local routing domain. It is 240 also noted that the propagation time of RPKI objects may be different 241 to the propagation time of routes, and that routes may be learned by 242 an RP's routing system before the RP's local RPKI repository cache 243 picks up the associated ROAs and recognises them as having a validity 244 state of "valid" within the RPKI. 246 4. Disavowal of Routing Origination 248 A ROA is a positive attestation that a prefix holder has authorized 249 an AS to originate a route for this prefix into the inter-domain 250 routing system. It is possible for a prefix holder to construct an 251 authorization where no valid AS has been granted any such authority 252 to originate a route for an address prefix. This is achieved by 253 using a ROA where the ROA's subject AS is one that must not be used 254 in any routing context. Specifically, AS 0 is reserved by the IANA 255 such that it may be used to identify non-routed networks 256 [IANA.AS-Registry]. 258 A ROA with a subject of AS 0 (AS0-ROA) is an attestation by the 259 holder of a prefix that the prefix described in the ROA, and any more 260 specific prefix, should not be used in a routing context. 262 The route validation procedure, described in Section 2, will provide 263 a "valid" outcome if any ROA matches the address prefix and origin 264 AS, even if other valid ROAs would provide an "invalid" validation 265 outcome if used in isolation. Consequently, an AS0-ROA has a lower 266 relative preference than any other ROA that has a routable AS as its 267 subject. This allows a prefix holder to use an AS0-ROA to declare a 268 default condition that any route that is equal to, or more specific 269 than the prefix to be considered to be invalid, while also allowing 270 other concurrently issued ROAs to describe valid origination 271 authorizations for more specific prefixes. 273 By convention, an AS0-ROA should have a maxLength value of 32 for 274 IPv4 addresses and a maxlength value of 128 for IPv6 addresses, 275 although in terms of route validation the same outcome would be 276 achieved with any valid maxLength value, or even if the maxLength 277 element were to be omitted from the ROA. 279 Also by convention, an AS0-ROA should be the only ROA issued for a 280 given address prefix, although again this is not a strict 281 requirement. An AS0-ROA MAY coexist with ROAs that have different 282 subject AS values, although in such cases the presence or otherwise 283 of the AS0-ROA does not alter the route's validity state in any way. 285 5. Route Validation Lifetime 287 The "lifetime" of a validation outcome refers to the time period 288 during which the original validation outcome can be still applied. 289 The implicit assumption here is that when the validation lifetime 290 expires the routing object should be re-tested for validity. 292 The validation lifetime for a ROA is controlled by the Valid times 293 specified in the End Entity (EE) Certificate used to sign the ROA, 294 and the valid times of those certificates in the certification path 295 used to validate the EE Certificate. A ROA validation "expires" at 296 the Validity To field of the signing EE certificate, or at such a 297 time when there is no certification path that can validate the ROA. 298 A ROA issuer may elect to prematurely invalidate a ROA by revoking 299 the EE certificate that was used to sign the ROA. 301 6. Security Considerations 303 ROA issuers should be aware of the validation implication in issuing 304 a ROA, in that a ROA implicitly invalidates all routes that have more 305 specific prefixes with a prefix length greater than maxLength, and 306 all originating AS's other than the AS listed in the collection of 307 ROAs for this prefix. 309 A conservative operational practice would be to ensure the issuing of 310 ROAs for all more specific prefixes with distinct origination AS's 311 prior to the issuing of ROAs for larger encompassing address blocks, 312 in order to avoid inadvertent invalidation of valid routes during ROA 313 generation. 315 ROA issuers should also be aware that if they generate a ROA for one 316 origin AS, then if the address prefix holder authorises multiple AS's 317 to originate routes for a given address prefix, then is necessary for 318 a ROA be generated for every such authorized AS. 320 7. IANA Considerations 322 [There are no IANA Considerations.] 324 8. Acknowledgements 326 The authors would like to acknowledge the helpful contributions of 327 John Scudder and Stephen Kent in preparing this document, and also 328 the contributions of many members of the SIDR Working Group in 329 response to presentations of this material in SIDR WG sessions. The 330 authors also acknowledge prior work undertaken by Tony Bates, Randy 331 Bush, Tony Li, and Yakov Rekhter as the validation outcomes described 332 here reflect the authentication outcomes and semantics of origin AS 333 verification described in [exI-D.bates]. A number of validation 334 concepts relating to a route's "validity state" presented in 335 [I-D.ietf-sidr-pfx-validate], edited by Pradosh Mohapatra et al, have 336 be used in this document. 338 9. References 340 9.1. Normative References 342 [I-D.ietf-sidr-arch] 343 Lepinski, M. and S. Kent, "An Infrastructure to Support 344 Secure Internet Routing", draft-ietf-sidr-arch (work in 345 progress), October 2009. 347 [I-D.ietf-sidr-roa-format] 348 Lepinski, M., Kent, S., and D. Kong, "An Infrastructure to 349 Support Secure Internet Routing", 350 draft-ietf-sidr-roa-format (work in progress), 351 October 2009. 353 [RFC3779] Lynn, C., Kent, S., and K. Seo, "X.509 Extensions for IP 354 Addresses and AS Identifiers", RFC 3779, June 2004. 356 [RFC4271] Rekhter, Y., Li, T., and S. Hares, "A Border Gateway 357 Protocol 4 (BGP-4)", RFC 4271, January 2006. 359 [RFC5280] Cooper, D., Santesson, S., Farrell, S., Boeyen, S., 360 Housley, R., and W. Polk, "Internet X.509 Public Key 361 Infrastructure Certificate and Certificate Revocation List 362 (CRL) Profile", RFC 5280, May 2008. 364 9.2. Informative References 366 [I-D.ietf-sidr-pfx-validate] 367 Mohapatra, P., Scudder, J., Ward, D., Bush, R., and R. 368 Austein, "BGP Prefix Origin Validation", 369 draft-ietf-sidr-pfx-validate-00 (work in progress), 370 July 2010. 372 [IANA.AS-Registry] 373 IANA, "IANA Autonomous System Number Registry", 374 March 2010. 376 [exI-D.bates] 377 Bates, T., Bush, R., Li, T., and Y. Rekhter, "DNS-based 378 NLRI origin AS verification in BGP", 379 draft-bates-bgp4-nlri-orig-verif-00.txt (work in 380 progress), January 1998. 382 Authors' Addresses 384 Geoff Huston 385 Asia Pacific Network Information Centre 387 Email: gih@apnic.net 389 George Michaelson 390 Asia Pacific Network Information Centre 392 Email: ggm@apnic.net