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(The document does seem to have the reference to RFC 2119 which the ID-Checklist requires). -- The document date (July 3, 2017) is 2488 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(See RFCs 3967 and 4897 for information about using normative references to lower-maturity documents in RFCs) == Outdated reference: A later version (-11) exists of draft-ietf-idr-route-leak-detection-mitigation-03 == Outdated reference: A later version (-23) exists of draft-ietf-sidr-bgpsec-protocol-15 -- Obsolete informational reference (is this intentional?): RFC 5226 (Obsoleted by RFC 8126) Summary: 0 errors (**), 0 flaws (~~), 4 warnings (==), 2 comments (--). Run idnits with the --verbose option for more detailed information about the items above. -------------------------------------------------------------------------------- 2 Network Working Group A. Azimov 3 Internet-Draft E. Bogomazov 4 Intended status: Standards Track Qrator Labs 5 Expires: January 4, 2018 R. Bush 6 Internet Initiative Japan 7 K. Patel 8 Arrcus, Inc. 9 K. Sriram 10 US NIST 11 July 3, 2017 13 Route Leak Prevention using Roles in Update and Open messages 14 draft-ietf-idr-bgp-open-policy-01 16 Abstract 18 Route Leaks are the propagation of BGP prefixes which violate 19 assumptions of BGP topology relationships; e.g. passing a route 20 learned from one peer to another peer or to a transit provider, 21 passing a route learned from one transit provider to another transit 22 provider or to a peer. Today, approaches to leak prevention rely on 23 marking routes according to operator configuration options without 24 any check that the configuration corresponds to that of the BGP 25 neighbor, or enforcement that the two BGP speakers agree on the 26 relationship. This document enhances BGP Open to establish agreement 27 of the (peer, customer, provider, internal) relationship of two 28 neighboring BGP speakers to enforce appropriate configuration on both 29 sides. Propagated routes are then marked with an iOTC attribute 30 according to agreed relationship allowing prevention of route leaks. 32 Requirements Language 34 The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT", 35 "SHOULD", "SHOULD NOT", "RECOMMENDED", "MAY", and "OPTIONAL" are to 36 be interpreted as described in RFC 2119 [RFC2119] only when they 37 appear in all upper case. They may also appear in lower or mixed 38 case as English words, without normative meaning. 40 Status of This Memo 42 This Internet-Draft is submitted in full conformance with the 43 provisions of BCP 78 and BCP 79. 45 Internet-Drafts are working documents of the Internet Engineering 46 Task Force (IETF). Note that other groups may also distribute 47 working documents as Internet-Drafts. The list of current Internet- 48 Drafts is at http://datatracker.ietf.org/drafts/current/. 50 Internet-Drafts are draft documents valid for a maximum of six months 51 and may be updated, replaced, or obsoleted by other documents at any 52 time. It is inappropriate to use Internet-Drafts as reference 53 material or to cite them other than as "work in progress." 55 This Internet-Draft will expire on January 4, 2018. 57 Copyright Notice 59 Copyright (c) 2017 IETF Trust and the persons identified as the 60 document authors. All rights reserved. 62 This document is subject to BCP 78 and the IETF Trust's Legal 63 Provisions Relating to IETF Documents 64 (http://trustee.ietf.org/license-info) in effect on the date of 65 publication of this document. Please review these documents 66 carefully, as they describe your rights and restrictions with respect 67 to this document. Code Components extracted from this document must 68 include Simplified BSD License text as described in Section 4.e of 69 the Trust Legal Provisions and are provided without warranty as 70 described in the Simplified BSD License. 72 Table of Contents 74 1. Preamble . . . . . . . . . . . . . . . . . . . . . . . . . . 3 75 1.1. Peering Relationships . . . . . . . . . . . . . . . . . . 3 76 2. Introduction . . . . . . . . . . . . . . . . . . . . . . . . 3 77 3. Role Definitions . . . . . . . . . . . . . . . . . . . . . . 3 78 4. BGP Role . . . . . . . . . . . . . . . . . . . . . . . . . . 4 79 5. Role capability . . . . . . . . . . . . . . . . . . . . . . . 4 80 6. Role correctness . . . . . . . . . . . . . . . . . . . . . . 5 81 6.1. Strict mode . . . . . . . . . . . . . . . . . . . . . . . 5 82 7. BGP Internal Only To Customer attribute . . . . . . . . . . . 6 83 8. Attribute or Community . . . . . . . . . . . . . . . . . . . 6 84 9. Compatibility with BGPsec . . . . . . . . . . . . . . . . . . 7 85 10. Additional Considerations . . . . . . . . . . . . . . . . . . 7 86 11. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 7 87 12. Security Considerations . . . . . . . . . . . . . . . . . . . 8 88 13. Acknowledgments . . . . . . . . . . . . . . . . . . . . . . . 8 89 14. References . . . . . . . . . . . . . . . . . . . . . . . . . 8 90 14.1. Normative References . . . . . . . . . . . . . . . . . . 8 91 14.2. Informative References . . . . . . . . . . . . . . . . . 8 92 Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . 9 94 1. Preamble 96 1.1. Peering Relationships 98 Despite uses of words such as "Customer," "Peer." etc. the intent is 99 not business relationships, who pays whom, etc. These are common 100 terms to represent restrictions on BGP route propagation, sometimes 101 known as Gao-Rexford model. E.g. if A is a "peer" of B and C, A does 102 not propagate B's prefixes to C. If D is a "customer" of E and F, D 103 does not propagate prefixes learned from E to F. 105 As the whole point of route leak detection and prevention is to 106 prevent vioation of these relationships, they are inescapable. 108 2. Introduction 110 This document specifies a new BGP Capability Code, [RFC5492] Sec 4, 111 which two BGP speakers MAY use to ensure that they MUST agree on 112 their relationship; i.e. customer and provider or peers. Either or 113 both may optionally be configured to require that this option be 114 exchanged for the BGP Open to succeed. 116 Also this document specifies a way to mark routes according to BGP 117 Roles established in OPEN message and a way to create double-boundary 118 filters for prevention of route leaks via new BGP Path Attribute. 120 For the purpose of this document, BGP route leaks are when a BGP 121 route was learned from transit provider or peer and is announced to 122 another provider or peer. See 123 [I-D.ietf-grow-route-leak-problem-definition]. These are usually the 124 result of misconfigured or absent BGP route filtering or lack of 125 coordination between two BGP speakers. 127 [I-D.ietf-idr-route-leak-detection-mitigation] The mechanism proposed 128 in that draft provides the opportunity to detect route leaks made by 129 third parties but provides no support to strongly prevent route leak 130 creation. 132 Also, route tagging which relies on operator maintained policy 133 configuration is too easily and too often misconfigured. 135 3. Role Definitions 137 As many of these terms are used differently in various contexts, it 138 is worth being explicit. 140 A Provider: sends their own routes and (possibly) a subset of routes 141 learned from their other customers, peers, and transit providers 142 to their customer. 144 A Customer: accepts 'transit routes' from its provider(s) and 145 announces their own routes and the routes they have learned from 146 the transitive closure of their customers (AKA their 'customer 147 cone') to their provider(s). 149 A Peer: announces their routes and the routes from their customer 150 cone to other Peers. 152 An Internal: announces all routes, accepts all routes. 154 Of course, any BGP speaker may apply policy to reduce what is 155 announced, and a recipient may apply policy to reduce the set of 156 routes they accept. 158 4. BGP Role 160 BGP Role is new configuration option that SHOULD be configured at 161 each BGP session. It reflects the real-world agreement between two 162 BGP speakers about their peering relationship. 164 Allowed Role values for eBGP sessions are: 166 o Provider - sender is a transit provider to neighbor; 168 o Customer - sender is customer of neighbor; 170 o Peer - sender and neighbor are peers; 172 o Internal - sender and neighbor is part of same organization. 174 For iBGP sessions only Internal role MAY be configured. 176 Since BGP Role reflects the relationship between two BGP speakers, it 177 could also be used for more than route leak mitigation. 179 5. Role capability 181 The TLV (type, length, value) of the BGP Role capability are: 183 o Type - ; 185 o Length - 1 (octet); 187 o Value - integer corresponding to speaker' BGP Role. 189 +--------+----------------------+ 190 | Value | Role name | 191 +--------+----------------------+ 192 | 0 | Undefined | 193 | 1 | Sender is Peer | 194 | 2 | Sender is Provider | 195 | 3 | Sender is Customer | 196 | 4 | Sender is Internal | 197 +--------+----------------------+ 199 Table 1: Predefined BGP Role Values 201 6. Role correctness 203 Section 4 described how BGP Role is a reflection of the relationship 204 between two BGP speakers. But the mere presence of BGP Role doesn't 205 automatically guarantee role agreement between two BGP peers. 207 To enforce correctness, the BGP Role check is used with a set of 208 constrains on how speakers' BGP Roles MUST corresponded. Of course, 209 each speaker MUST announce and accept the BGP Role capability in the 210 BGP OPEN message exchange. 212 If a speaker receives a BGP Role capability, it MUST check value of 213 the received capability with its own BGP Role (if it is set). The 214 allowed pairings are (first a sender's Role, second the receiver's 215 Role): 217 +--------------+----------------+ 218 | Sender Role | Receiver Role | 219 +--------------+----------------+ 220 | Peer | Peer | 221 | Provider | Customer | 222 | Customer | Provider | 223 | Internal | Internal | 224 +--------------+----------------+ 226 Table 2: Allowed Role Capabilities 228 In all other cases speaker MUST send a Role Mismatch Notification 229 (code 2, sub-code ). 231 6.1. Strict mode 233 A new BGP configuration option "strict mode" is defined with values 234 of true or false. If set to true, then the speaker MUST refuse to 235 establish a BGP session with peers which do not announce the BGP Role 236 capability in their OPEN message. If a speaker rejects a connection, 237 it MUST send a Connection Rejected Notification [RFC4486] 238 (Notification with error code 6, subcode 5). By default strict mode 239 SHOULD be set to false for backward compatibility with BGP speakers, 240 that do not yet support this mechanism. 242 7. BGP Internal Only To Customer attribute 244 The Internal Only To Customer (iOTC) attribute is a new optional, 245 non-transitive BGP Path attribute with the Type Code . This 246 attribute has zero length as it is used only as a flag. 248 There are three rules of iOTC attribute usage: 250 1. The iOTC attribute MUST be added to all incoming routes if the 251 receiver's Role is Customer or Peer; 253 2. Routes with the iOTC attribute set MUST NOT be announced by a 254 sender whose Role is Customer or Peer; 256 3. A sender MUST NOT include this attribute in UPDATE messages if 257 its Role is Customer, Provider or Peer. If it is contained in an 258 UPDATE message from eBGP speaker and receiver's Role is Customer, 259 Provider, Peer or unspecified, then this attribute MUST be 260 removed. 262 These three rules provide mechanism that strongly prevents route leak 263 creation by an AS. 265 8. Attribute or Community 267 Having the relationship hard set by agreement between the two peers 268 in BGP OPEN is critical; the routers enforce the relationship 269 irrespective of operator configuration errors. 271 Similarly, it is critical that the application of that relationship 272 on prefix propagation using iOTC is enforced by the router(s), and 273 minimally exposed to user misconfiguration. There is a question 274 whether the iOTC marking should be an attribute or a well-known 275 community. 277 There is a long and sordid history of mis-configurations inserting 278 incorrect communities, deleting communities, ignoring well-known 279 community markings etc. In this mechanism's case, an operator could, 280 for example, accidentally strip the well-known community on receipt. 282 As opposed to communities, BGP attributes may not be generally 283 modified or filtered by the operator. The router(s) enforce them. 285 This is the desired property for the iOTC marking. Hence, this 286 document specifies iOTC as an attribute. 288 9. Compatibility with BGPsec 290 As the iOTC field is non-transitive, it is not seen by or signed by 291 BGPsec [I-D.ietf-sidr-bgpsec-protocol]. 293 10. Additional Considerations 295 As the BGP Role reflects the relationship between neighbors, it can 296 also have other uses. As an example, BGP Role might affect route 297 priority, or be used to distinguish borders of a network if a network 298 consists of multiple AS. 300 Though such uses may be worthwhile, they are not the goal of this 301 document. Note that such uses would require local policy control. 303 As BGP role configuration results in automatic creation of inbound/ 304 outbound filters, existence of roles should be treated as existence 305 of Import and Export policy. [I-D.ietf-grow-bgp-reject] 307 This document doesn't provide any security measures to check 308 correctness of iOTC usage if role isn't configured. 310 11. IANA Considerations 312 This document defines a new Capability Codes option [to be removed 313 upon publication: http://www.iana.org/assignments/capability-codes/ 314 capability-codes.xhtml] [RFC5492], named "BGP Role", assigned value 315 . The length of this capability is 1. 317 The BGP Role capability includes a Value field, for which IANA is 318 requested to create and maintain a new sub-registry called "BGP Role 319 Value". Assignments consist of Value and corresponding Role name. 320 Initially this registry is to be populated with the data in Table 1. 321 Future assignments may be made by a standard action procedure 322 [RFC5226]. 324 This document defines new subcode, "Role Mismatch", assigned value 325 in the OPEN Message Error subcodes registry [to be removed 326 upon publication: http://www.iana.org/assignments/bgp-parameters/bgp- 327 parameters.xhtml#bgp-parameters-6] [RFC4271]. 329 This document defines a new optional, non-transitive BGP Path 330 Attributes option, named "Internal Only To Customer", assigned value 331 [To be removed upon publication: 332 http://www.iana.org/assignments/bgp-parameters/bgp- 333 parameters.xhtml#bgp-parameters-2] [RFC4271]. The length of this 334 attribute is 0. 336 12. Security Considerations 338 This document proposes a mechanism for prevention of route leaks that 339 are the result of BGP policy misconfiguration. 341 Deliberate sending of a known conflicting BGP Role could be used to 342 sabotage a BGP connection. This is easily detectable. 344 BGP Role is disclosed only to an immediate BGP neighbor, so it will 345 not itself reveal any sensitive information to third parties. 347 13. Acknowledgments 349 The authors wish to thank Douglas Montgomery, Brian Dickson, Andrei 350 Robachevsky and Daniel Ginsburg for their contributions to a variant 351 of this work. 353 14. References 355 14.1. Normative References 357 [RFC2119] Bradner, S., "Key words for use in RFCs to Indicate 358 Requirement Levels", BCP 14, RFC 2119, 359 DOI 10.17487/RFC2119, March 1997, 360 . 362 [RFC4271] Rekhter, Y., Ed., Li, T., Ed., and S. Hares, Ed., "A 363 Border Gateway Protocol 4 (BGP-4)", RFC 4271, 364 DOI 10.17487/RFC4271, January 2006, 365 . 367 [RFC4486] Chen, E. and V. Gillet, "Subcodes for BGP Cease 368 Notification Message", RFC 4486, DOI 10.17487/RFC4486, 369 April 2006, . 371 [RFC5492] Scudder, J. and R. Chandra, "Capabilities Advertisement 372 with BGP-4", RFC 5492, DOI 10.17487/RFC5492, February 373 2009, . 375 14.2. Informative References 377 [I-D.ietf-grow-bgp-reject] 378 Mauch, J., Snijders, J., and G. Hankins, "Default EBGP 379 Route Propagation Behavior Without Policies", draft-ietf- 380 grow-bgp-reject-08 (work in progress), May 2017. 382 [I-D.ietf-grow-route-leak-problem-definition] 383 Sriram, K., Montgomery, D., McPherson, D., Osterweil, E., 384 and B. Dickson, "Problem Definition and Classification of 385 BGP Route Leaks", draft-ietf-grow-route-leak-problem- 386 definition-06 (work in progress), May 2016. 388 [I-D.ietf-idr-route-leak-detection-mitigation] 389 Sriram, K., Montgomery, D., Dickson, B., Patel, K., and A. 390 Robachevsky, "Methods for Detection and Mitigation of BGP 391 Route Leaks", draft-ietf-idr-route-leak-detection- 392 mitigation-03 (work in progress), May 2016. 394 [I-D.ietf-sidr-bgpsec-protocol] 395 Lepinski, M. and K. Sriram, "BGPsec Protocol 396 Specification", draft-ietf-sidr-bgpsec-protocol-15 (work 397 in progress), March 2016. 399 [RFC5226] Narten, T. and H. Alvestrand, "Guidelines for Writing an 400 IANA Considerations Section in RFCs", RFC 5226, 401 DOI 10.17487/RFC5226, May 2008, 402 . 404 Authors' Addresses 406 Alexander Azimov 407 Qrator Labs 409 Email: aa@qrator.net 411 Eugene Bogomazov 412 Qrator Labs 414 Email: eb@qrator.net 416 Randy Bush 417 Internet Initiative Japan 419 Email: randy@psg.com 421 Keyur Patel 422 Arrcus, Inc. 424 Email: keyur@arrcus.com 425 Kotikalapudi Sriram 426 US NIST 428 Email: ksriram@nist.gov