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(The document does seem to have the reference to RFC 2119 which the ID-Checklist requires). -- The document date (January 1, 2018) is 2306 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(See RFCs 3967 and 4897 for information about using normative references to lower-maturity documents in RFCs) == Outdated reference: A later version (-11) exists of draft-ietf-idr-route-leak-detection-mitigation-03 == Outdated reference: A later version (-23) exists of draft-ietf-sidr-bgpsec-protocol-15 -- Obsolete informational reference (is this intentional?): RFC 5226 (Obsoleted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: July 5, 2018 R. Bush 6 Internet Initiative Japan 7 K. Patel 8 Arrcus, Inc. 9 K. Sriram 10 US NIST 11 January 1, 2018 13 Route Leak Prevention using Roles in Update and Open messages 14 draft-ietf-idr-bgp-open-policy-02 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 July 5, 2018. 57 Copyright Notice 59 Copyright (c) 2018 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 | Sender is Peer | 193 | 1 | Sender is Provider | 194 | 2 | Sender is Customer | 195 | 3 | Sender is Internal | 196 +--------+----------------------+ 198 Table 1: Predefined BGP Role Values 200 6. Role correctness 202 Section 4 described how BGP Role is a reflection of the relationship 203 between two BGP speakers. But the mere presence of BGP Role doesn't 204 automatically guarantee role agreement between two BGP peers. 206 To enforce correctness, the BGP Role check is used with a set of 207 constrains on how speakers' BGP Roles MUST corresponded. Of course, 208 each speaker MUST announce and accept the BGP Role capability in the 209 BGP OPEN message exchange. 211 If a speaker receives a BGP Role capability, it MUST check value of 212 the received capability with its own BGP Role (if it is set). The 213 allowed pairings are (first a sender's Role, second the receiver's 214 Role): 216 +--------------+----------------+ 217 | Sender Role | Receiver Role | 218 +--------------+----------------+ 219 | Peer | Peer | 220 | Provider | Customer | 221 | Customer | Provider | 222 | Internal | Internal | 223 +--------------+----------------+ 225 Table 2: Allowed Role Capabilities 227 In case of any other pair of roles, speaker MUST send a Role Mismatch 228 Notification (code 2, sub-code ). 230 6.1. Strict mode 232 A new BGP configuration option "strict mode" is defined with values 233 of true or false. If set to true, then the speaker MUST refuse to 234 establish a BGP session with peers which do not announce the BGP Role 235 capability in their OPEN message. If a speaker rejects a connection, 236 it MUST send a Connection Rejected Notification [RFC4486] 237 (Notification with error code 6, subcode 5). By default strict mode 238 SHOULD be set to false for backward compatibility with BGP speakers, 239 that do not yet support this mechanism. 241 7. BGP Internal Only To Customer attribute 243 The Internal Only To Customer (iOTC) attribute is a new optional, 244 non-transitive BGP Path attribute with the Type Code . This 245 attribute has zero length as it is used only as a flag. 247 There are three rules of iOTC attribute usage: 249 1. The iOTC attribute MUST be added to all incoming routes if the 250 receiver's Role is Customer or Peer; 252 2. Routes with the iOTC attribute set MUST NOT be announced by a 253 sender whose Role is Customer or Peer; 255 3. A sender MUST NOT include this attribute in UPDATE messages if 256 its Role is Customer, Provider or Peer. If it is contained in an 257 UPDATE message from eBGP speaker and receiver's Role is Customer, 258 Provider, Peer or unspecified, then this attribute MUST be 259 removed. 261 These three rules provide mechanism that strongly prevents route leak 262 creation by an AS. 264 8. Attribute or Community 266 Having the relationship hard set by agreement between the two peers 267 in BGP OPEN is critical; the routers enforce the relationship 268 irrespective of operator configuration errors. 270 Similarly, it is critical that the application of that relationship 271 on prefix propagation using iOTC is enforced by the router(s), and 272 minimally exposed to user misconfiguration. There is a question 273 whether the iOTC marking should be an attribute or a well-known 274 community. 276 There is a long and sordid history of mis-configurations inserting 277 incorrect communities, deleting communities, ignoring well-known 278 community markings etc. In this mechanism's case, an operator could, 279 for example, accidentally strip the well-known community on receipt. 281 As opposed to communities, BGP attributes may not be generally 282 modified or filtered by the operator. The router(s) enforce them. 283 This is the desired property for the iOTC marking. Hence, this 284 document specifies iOTC as an attribute. 286 9. Compatibility with BGPsec 288 As the iOTC field is non-transitive, it is not seen by or signed by 289 BGPsec [I-D.ietf-sidr-bgpsec-protocol]. 291 10. Additional Considerations 293 As the BGP Role reflects the relationship between neighbors, it can 294 also have other uses. As an example, BGP Role might affect route 295 priority, or be used to distinguish borders of a network if a network 296 consists of multiple AS. 298 Though such uses may be worthwhile, they are not the goal of this 299 document. Note that such uses would require local policy control. 301 As BGP role configuration results in automatic creation of inbound/ 302 outbound filters, existence of roles should be treated as existence 303 of Import and Export policy. [I-D.ietf-grow-bgp-reject] 305 This document doesn't provide any security measures to check 306 correctness of iOTC usage if role isn't configured. 308 11. IANA Considerations 310 This document defines a new Capability Codes option [to be removed 311 upon publication: http://www.iana.org/assignments/capability-codes/ 312 capability-codes.xhtml] [RFC5492], named "BGP Role", assigned value 313 . The length of this capability is 1. 315 The BGP Role capability includes a Value field, for which IANA is 316 requested to create and maintain a new sub-registry called "BGP Role 317 Value". Assignments consist of Value and corresponding Role name. 318 Initially this registry is to be populated with the data in Table 1. 319 Future assignments may be made by a standard action procedure 320 [RFC5226]. 322 This document defines new subcode, "Role Mismatch", assigned value 323 in the OPEN Message Error subcodes registry [to be removed 324 upon publication: http://www.iana.org/assignments/bgp-parameters/bgp- 325 parameters.xhtml#bgp-parameters-6] [RFC4271]. 327 This document defines a new optional, non-transitive BGP Path 328 Attributes option, named "Internal Only To Customer", assigned value 329 [To be removed upon publication: 330 http://www.iana.org/assignments/bgp-parameters/bgp- 331 parameters.xhtml#bgp-parameters-2] [RFC4271]. The length of this 332 attribute is 0. 334 12. Security Considerations 336 This document proposes a mechanism for prevention of route leaks that 337 are the result of BGP policy misconfiguration. 339 Deliberate sending of a known conflicting BGP Role could be used to 340 sabotage a BGP connection. This is easily detectable. 342 BGP Role is disclosed only to an immediate BGP neighbor, so it will 343 not itself reveal any sensitive information to third parties. 345 13. Acknowledgments 347 The authors wish to thank Douglas Montgomery, Brian Dickson, Andrei 348 Robachevsky and Daniel Ginsburg for their contributions to a variant 349 of this work. 351 14. References 353 14.1. Normative References 355 [RFC2119] Bradner, S., "Key words for use in RFCs to Indicate 356 Requirement Levels", BCP 14, RFC 2119, 357 DOI 10.17487/RFC2119, March 1997, . 360 [RFC4271] Rekhter, Y., Ed., Li, T., Ed., and S. Hares, Ed., "A 361 Border Gateway Protocol 4 (BGP-4)", RFC 4271, 362 DOI 10.17487/RFC4271, January 2006, . 365 [RFC4486] Chen, E. and V. Gillet, "Subcodes for BGP Cease 366 Notification Message", RFC 4486, DOI 10.17487/RFC4486, 367 April 2006, . 369 [RFC5492] Scudder, J. and R. Chandra, "Capabilities Advertisement 370 with BGP-4", RFC 5492, DOI 10.17487/RFC5492, February 371 2009, . 373 14.2. Informative References 375 [I-D.ietf-grow-bgp-reject] 376 Mauch, J., Snijders, J., and G. Hankins, "Default EBGP 377 Route Propagation Behavior Without Policies", draft-ietf- 378 grow-bgp-reject-08 (work in progress), May 2017. 380 [I-D.ietf-grow-route-leak-problem-definition] 381 Sriram, K., Montgomery, D., McPherson, D., Osterweil, E., 382 and B. Dickson, "Problem Definition and Classification of 383 BGP Route Leaks", draft-ietf-grow-route-leak-problem- 384 definition-06 (work in progress), May 2016. 386 [I-D.ietf-idr-route-leak-detection-mitigation] 387 Sriram, K., Montgomery, D., Dickson, B., Patel, K., and A. 388 Robachevsky, "Methods for Detection and Mitigation of BGP 389 Route Leaks", draft-ietf-idr-route-leak-detection- 390 mitigation-03 (work in progress), May 2016. 392 [I-D.ietf-sidr-bgpsec-protocol] 393 Lepinski, M. and K. Sriram, "BGPsec Protocol 394 Specification", draft-ietf-sidr-bgpsec-protocol-15 (work 395 in progress), March 2016. 397 [RFC5226] Narten, T. and H. Alvestrand, "Guidelines for Writing an 398 IANA Considerations Section in RFCs", RFC 5226, 399 DOI 10.17487/RFC5226, May 2008, . 402 Authors' Addresses 404 Alexander Azimov 405 Qrator Labs 407 Email: aa@qrator.net 409 Eugene Bogomazov 410 Qrator Labs 412 Email: eb@qrator.net 414 Randy Bush 415 Internet Initiative Japan 417 Email: randy@psg.com 419 Keyur Patel 420 Arrcus, Inc. 422 Email: keyur@arrcus.com 423 Kotikalapudi Sriram 424 US NIST 426 Email: ksriram@nist.gov