idnits 2.17.1 draft-ietf-sidr-bgpsec-overview-07.txt: Checking boilerplate required by RFC 5378 and the IETF Trust (see https://trustee.ietf.org/license-info): ---------------------------------------------------------------------------- No issues found here. Checking nits according to https://www.ietf.org/id-info/1id-guidelines.txt: ---------------------------------------------------------------------------- No issues found here. Checking nits according to https://www.ietf.org/id-info/checklist : ---------------------------------------------------------------------------- No issues found here. Miscellaneous warnings: ---------------------------------------------------------------------------- == The copyright year in the IETF Trust and authors Copyright Line does not match the current year -- The document date (June 15, 2015) is 3231 days in the past. Is this intentional? Checking references for intended status: Informational ---------------------------------------------------------------------------- No issues found here. Summary: 0 errors (**), 0 flaws (~~), 1 warning (==), 1 comment (--). Run idnits with the --verbose option for more detailed information about the items above. -------------------------------------------------------------------------------- 2 Network Working Group M. Lepinski 3 Internet Draft BBN Technologies 4 Intended status: Informational S. Turner 5 Expires: December 17, 2015 IECA 6 June 15, 2015 8 An Overview of BGPsec 9 draft-ietf-sidr-bgpsec-overview-07 11 Abstract 13 This document provides an overview of a security extension to the 14 Border Gateway Protocol (BGP) referred to as BGPsec. BGPsec improves 15 security for BGP routing. 17 Status of this Memo 19 This Internet-Draft is submitted in full conformance with the 20 provisions of BCP 78 and BCP 79. 22 Internet-Drafts are working documents of the Internet Engineering 23 Task Force (IETF), its areas, and its working groups. Note that 24 other groups may also distribute working documents as Internet- 25 Drafts. 27 Internet-Drafts are draft documents valid for a maximum of six months 28 and may be updated, replaced, or obsoleted by other documents at any 29 time. It is inappropriate to use Internet-Drafts as reference 30 material or to cite them other than as "work in progress." 32 The list of current Internet-Drafts can be accessed at 33 http://www.ietf.org/ietf/1id-abstracts.txt 35 The list of Internet-Draft Shadow Directories can be accessed at 36 http://www.ietf.org/shadow.html 38 This Internet-Draft will expire on December 17, 2015. 40 Copyright Notice 42 Copyright (c) 2015 IETF Trust and the persons identified as the 43 document authors. All rights reserved. 45 This document is subject to BCP 78 and the IETF Trust's Legal 46 Provisions Relating to IETF Documents 47 (http://trustee.ietf.org/license-info) in effect on the date of 48 publication of this document. Please review these documents 49 carefully, as they describe your rights and restrictions with respect 50 to this document. Code Components extracted from this document must 51 include Simplified BSD License text as described in Section 4.e of 52 the Trust Legal Provisions and are provided without warranty as 53 described in the Simplified BSD License. 55 Table of Contents 57 1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . . 2 58 2. Background . . . . . . . . . . . . . . . . . . . . . . . . . . 3 59 3. BGPsec Operation . . . . . . . . . . . . . . . . . . . . . . . 4 60 3.1. Negotiation of BGPsec . . . . . . . . . . . . . . . . . . . 4 61 3.2. Update signing and validation . . . . . . . . . . . . . . . 5 62 4. Design and Deployment Considerations . . . . . . . . . . . . . 6 63 4.1. Disclosure of topology information . . . . . . . . . . . . 6 64 4.2. BGPsec router assumptions . . . . . . . . . . . . . . . . . 7 65 4.3. BGPsec and consistency of externally visible data . . . . . 7 66 5. Security Considerations . . . . . . . . . . . . . . . . . . . . 8 67 6. IANA Considerations . . . . . . . . . . . . . . . . . . . . . . 8 68 7.1. Normative References . . . . . . . . . . . . . . . . . . . 8 69 7.2. Informative References . . . . . . . . . . . . . . . . . . 9 70 Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . . 10 72 1. Introduction 74 BGPsec (Border Gateway Protocol Security) is an extension to the 75 Border Gateway Protocol (BGP) that provides improved security for BGP 76 routing [RFC4271]. This document contains a brief overview of BGPsec 77 and its envisioned usage. 79 A more detailed discussion of BGPsec is provided in the following set 80 of documents: 82 . [RFC7132]: 84 A threat model describing the security context in which BGPsec 85 is intended to operate. 87 . [RFC7353]: 89 A set of requirements for BGP path security, which BGPsec is 90 intended to satisfy. 92 . [I-D.sidr-bgpsec-protocol]: 94 A standards track document specifying the BGPsec extension to 95 BGP. 97 . [I-D.sidr-as-migration]: 99 A standards track document describing how to implement an AS 100 Number migration while using BGPsec. 102 . [I-D.sidr-bgpsec-ops]: 104 An informational document describing operational considerations. 106 . [I-D.sidr-bgpsec-pki-profiles]: 108 A standards track document specifying a profile for X.509 109 certificates that bind keys used in BGPsec to Autonomous System 110 numbers, as well as associated Certificate Revocation Lists 111 (CRLs), and certificate requests. 113 . [I-D.sidr-bgpsec-algs] 115 A standards track document specifying suites of signature and 116 digest algorithms for use in BGPsec. 118 In addition to this document set, some readers might be interested in 119 [I-D.sriram-bgpsec-design-choices], an informational document 120 describing the choices that were made the by the author team prior to 121 the publication of the -00 version of draft-ietf-sidr-bgpsec- 122 protocol. Discussion of design choices made since the publication of 123 the -00 can be found in the archives of the SIDR working group 124 mailing list. 126 2. Background 128 The motivation for developing BGPsec is that BGP does not include 129 mechanisms that allow an Autonomous System (AS) to verify the 130 legitimacy and authenticity of BGP route advertisements (see for 131 example, [RFC4272]). 133 The Resource Public Key Infrastructure (RPKI), described in 134 [RFC6480], provides a first step towards addressing the validation of 135 BGP routing data. RPKI resource certificates are issued to the 136 holders of AS number and IP address resources, providing a binding 137 between these resources and cryptographic keys that can be used to 138 verify digital signatures. Additionally, the RPKI architecture 139 specifies a digitally signed object, a Route Origination 140 Authorization (ROA), that allows holders of IP address resources to 141 authorize specific ASes to originate routes (in BGP) to these 142 resources. Data extracted from valid ROAs can be used by BGP speakers 143 to determine whether a received route was actually originated by an 144 AS authorized to originate that route (see [RFC6483] and [RFC7115]). 146 By instituting a local policy that prefers routes with origins 147 validated using RPKI data (versus routes to the same prefix that 148 cannot be so validated) an AS can protect itself from certain mis- 149 origination attacks. However, use of RPKI data alone provides little 150 or no protection against a sophisticated attacker. Such an attacker 151 could, for example, conduct a route hijacking attack by appending an 152 authorized origin AS to an otherwise illegitimate AS path. (See 153 [RFC7132] for a detailed discussion of the BGPsec threat model.) 155 BGPsec extends the RPKI by adding an additional type of certificate, 156 referred to as a BGPsec router certificate, that binds an AS number 157 to a public signature verification key, the corresponding private key 158 of which is held by one or more BGP speakers within this AS. Private 159 keys corresponding to public keys in such certificates can then be 160 used within BGPsec to enable BGP speakers to sign on behalf of their 161 AS. The certificates thus allow a relying party to verify that a 162 BGPsec signature was produced by a BGP speaker belonging to a given 163 AS. The goal of BGPsec is to use such signatures to protect the AS 164 path data in BGP update messages so that a BGP speaker can assess the 165 validity of the AS path data in update messages that it receives. 167 3. BGPsec Operation 169 The core of BGPsec is a new optional (non-transitive) attribute, 170 called BGPsec_Path. This attribute includes both AS Path data as well 171 as a sequence of digital signatures, one for each AS in the path. 172 (The use of this new attribute is formally specified in [I-D.sidr- 173 bgpsec-protocol].) A new signature is added to this sequence each 174 time an update message leaves an AS. The signature is constructed so 175 that any tampering with the AS path data or Network Layer 176 Reachability Information (NLRI) in the BGPsec update message can be 177 detected by the recipient of the message. 179 3.1. Negotiation of BGPsec 181 The use of BGPsec is negotiated using BGP capability advertisements 182 [RFC5492]. Upon opening a BGP session with a peer, BGP speakers who 183 support (and wish to use) BGPsec include a newly-defined capability 184 in the OPEN message. 186 The use of BGPsec is negotiated separately for each address family. 187 This means that a BGP speaker could, for example, elect to use BGPsec 188 for IPv6, but not for IPv4 (or vice versa). Additionally, the use of 189 BGPsec is negotiated separately in the send and receive directions. 190 This means that a BGP speaker could, for example, indicate support 191 for sending BGPsec update messages but require that messages it 192 receives be traditional (non-BGPsec) update message. (To see why such 193 a feature might be useful, see Section 4.2.) 195 If the use of BGPsec is negotiated in a BGP session (in a given 196 direction, for a given address family) then both BGPsec update 197 messages (ones that contain the BGPsec_Path_Signature attribute) and 198 traditional BGP update messages (that do not contain this attribute) 199 can be sent within the session. 201 If a BGPsec-capable BGP speaker finds that its peer does not support 202 receiving BGPsec update messages, then the BGP speaker must remove 203 existing BGPsec_Path attribute from any update messages it sends to 204 this peer. 206 3.2. Update signing and validation 208 When a BGP speaker originates a BGPsec update message, it creates a 209 BGPsec_Path attribute containing a single signature. The signature 210 protects the Network Layer Reachability Information (NLRI), the AS 211 number of the originating AS, and the AS number of the peer AS to 212 whom the update message is being sent. Note that the NLRI in a BGPsec 213 update message is restricted to contain only a single prefix. 215 When a BGP speaker receives a BGPsec update message and wishes to 216 propagate the route advertisement contained in the update to an 217 external peer, it adds a new signature to the BGPsec_Path attribute. 218 This signature protects everything protected by the previous 219 signature, plus the AS number of the new peer to whom the update 220 message is being sent. 222 Each BGP speaker also adds a reference, called a Subject Key 223 Identifier (SKI), to its BGPsec Router certificate. The SKI is used 224 by a recipient to select the public key (and associated router 225 certificate data) needed for validation. 227 As an example, consider the following case in which an advertisement 228 for 192.0.2/24 is originated by AS 1, which sends the route to AS 2, 229 which sends it to AS 3, which sends it to AS 4. When AS 4 receives a 230 BGPsec update message for this route, it will contain the following 231 data: 233 . NLRI : 192.0.2/24 235 . AS path data: 3 2 1 237 . BGPsec_Path contains 3 signatures : 238 o Signature from AS 1 protecting 239 192.0.2/24, AS 1 and AS 2 241 o Signature from AS 2 protecting 243 Everything AS 1's signature protected, and AS 3 245 o Signature from AS 3 protecting 247 Everything AS 2's signature protected, and AS 4 249 When a BGPsec update message is received by a BGP speaker, the BGP 250 speaker can validate the message as follows. For each signature, the 251 BGP speaker first needs to determine if there is a valid RPKI Router 252 certificate matching the SKI and containing the appropriate AS 253 number. (This would typically be done by looking up the SKI in a 254 cache of data extracted from valid RPKI objects. A cache allows 255 certificate validation to be handled via an asynchronous process, 256 which might execute on another device.) 258 The BGP speaker then verifies the signature using the public key from 259 this BGPsec router certificate. If all the signatures can be verified 260 in this fashion, the BGP speaker is assured that the update message 261 it received actually came via the AS path specified in the update 262 message. 264 In the above example, upon receiving the BGPsec update message, a BGP 265 speaker for AS 4 would do the following. First, it would look at the 266 SKI for the first signature and see if this corresponds to a valid 267 BGPsec Router certificate for AS 1. Next, it would verify the first 268 signature using the key found in this valid certificate. Finally, it 269 would repeat this process for the second and third signatures, 270 checking to see that there are valid BGPsec router certificates for 271 AS 2 and AS 3 (respectively) and that the signatures can be verified 272 with the keys found in these certificates. Note that the BGPsec 273 speaker for AS 4 should additionally perform origin validation as per 274 RFC 6483 [RFC6483]. However, such origin validation is independent of 275 BGPsec. 277 4. Design and Deployment Considerations 279 In this section we provide a brief overview of several additional 280 topics that commonly arise in the discussion of BGPsec. 282 4.1. Disclosure of topology information 284 A key requirement in the design of BGPsec was that BGPsec not 285 disclose any new information about BGP peering topology. Since many 286 ISPs feel peering topology data is proprietary, further disclosure of 287 it would inhibit BGPsec adoption. 289 In particular, the topology information that can be inferred from 290 BGPsec update messages is exactly the same as that which can be 291 inferred from equivalent (non-BGPsec) BGP update messages. 293 4.2. BGPsec router assumptions 295 In order to achieve its security goals, BGPsec assumes additional 296 capabilities in routers. In particular, BGPsec involves adding 297 digital signatures to BGP update messages, which will significantly 298 increase the size of these messages. Therefore, an AS that wishes to 299 receive BGPsec update messages will require additional memory in its 300 routers to store (e.g., in ADJ RIBs) the data conveyed in these 301 larger update messages. Additionally, the design of BGPsec assumes 302 that an AS that elects to receive BGPsec update messages will do some 303 cryptographic signature verification at its edge router. This 304 verification may require additional capability in these edge routers. 306 Additionally, BGPsec requires that all BGPsec speakers will support 307 4-byte AS Numbers [RFC6793]. This is because the co-existence 308 strategy for 4-byte AS numbers and legacy 2-byte AS speakers that 309 gives special meaning to AS 23456 is incompatible with the security 310 the security properties that BGPsec seeks to provide. 312 For this initial version of BGPsec, optimizations to minimize the 313 size of BGPsec updates or the processing required in edge routers 314 have not been considered. Such optimizations may be considered in the 315 future. 317 Note also that the design of BGPsec allows an AS to send BGPsec 318 update messages (thus obtaining protection for routes it originates) 319 without receiving BGPsec update messages. An AS that only sends, and 320 does not receive, BGPsec update messages will require much less 321 capability in its edge routers to deploy BGPsec. In particular, a 322 router that only sends BGPsec update messages does not need 323 additional memory to store larger updates and requires only minimal 324 cryptographic capability (as generating one signature per outgoing 325 update requires less computation than verifying multiple signatures 326 on each incoming update message). See [I-D.sidr-bgpsec-ops] for 327 further discussion related to Edge ASes that do not provide transit. 329 4.3. BGPsec and consistency of externally visible data 331 Finally note that, by design, BGPsec prevents parties that propagate 332 route advertisements from including inconsistent or erroneous 333 information within the AS-Path (without detection). In particular, 334 this means that any deployed scenarios in which a BGP speaker 335 constructs such an inconsistent or erroneous AS Path attribute will 336 break when BGPsec is used. 338 For example, when BGPsec is not used, it is possible for a single 339 autonomous system to have one peering session where it identifies 340 itself as AS 111 and a second peering session where it identifies 341 itself as AS 222. In such a case, it might receive route 342 advertisements from the first peering session (as AS 111) and then 343 add AS 222 (but not AS 111) to the AS-Path and propagate them within 344 the second peering session. 346 Such behavior may very well be innocent and performed with the 347 consent of the legitimate holder of both AS 111 and 222. However, it 348 is indistinguishable from the following man-in-the-middle attack 349 performed by a malicious AS 222. First, the malicious AS 222 350 impersonates AS 111 in the first peering session (essentially 351 stealing a route advertisement intended for AS 111). The malicious AS 352 222 then inserts itself into the AS path and propagates the update to 353 its peers. 355 Therefore, when BGPsec is used, such an autonomous system would 356 either need to assert a consistent AS number in all external peering 357 sessions, or else it would need to add both AS 111 and AS 222 to the 358 AS-Path (along with appropriate signatures) for route advertisements 359 that it receives from the first peering session and propagates within 360 the second peering session. See [I-D.sidr-as-migration] for a 361 detailed discussion of how to reasonably manage AS number migrations 362 while using BGPsec. 364 5. Security Considerations 366 This document provides an overview of BPSEC; it does not define the 367 BGPsec extension to BGP. The BGPsec extension is defined in [I- 368 D.sidr-bgpsec-protocol]. The threat model for the BGPsec is 369 described in [RFC7132]. 371 6. IANA Considerations 373 None. 375 7.1. Normative References 377 [RFC4271] Rekhter, Y., Li, T., and S. Hares, Eds., "A Border Gateway 378 Protocol 4 (BGP-4)", RFC 4271, January 2006. 380 [RFC6793] Vohra, Q. and E. Chen, "BGP Support for Four-octet AS 381 Numbers", RFC 6793, December 2012. 383 [RFC5492] Scudder, J. and R. Chandra, "Capabilities Advertisement 384 with BGP-4", RFC 5492, February 2009. 386 [RFC6480] Lepinski, M. and S. Kent, "An Infrastructure to Support 387 Secure Internet Routing", February 2012. 389 [RFC6483] Huston, G., and G. Michaelson, "Validation of Route 390 Origination using the Resource Certificate PKI and ROAs", February 391 2012. 393 [RFC7132] Kent, S., and A. Chi, "Threat Model for BGP Path Security", 394 RFC 7132, February 2014. 396 [RFC7115] Bush, R., "RPKI-Based Origin Validation Operation", RFC 397 7115, January 2014. 399 [I-D.sidr-bgpsec-protocol] Lepinski, M., Ed., "BPSEC Protocol 400 Specification", draft-ietf-sidr-bgpsec-protocol, work-in-progress. 402 [I-D.sidr-bgpsec-ops] Bush, R., "BGPsec Operational Considerations", 403 draft-ietf-sidr-bgpsec-ops, work-in-progress. 405 [I-D.sidr-bgpsec-algs] Turner, S., "BGP Algorithms, Key Formats, & 406 Signature Formats", draft-ietf-sidr-bgpsec-algs, work-in-progress. 408 [I-D.sidr-bgpsec-pki-profiles] Reynolds, M. and S. Turner, "A Profile 409 for BGPsec Router Certificates, Certificate Revocation Lists, and 410 Certification Requests", draft-ietf-sidr-bgpsec-pki-profiles, work- 411 in- progress. 413 [I-D.sidr-as-migration] George, W. and S. Murphy, "BGPSec 414 Considerations for AS Migration", draft-ietf-sidr-as-migration, work- 415 in-progress. 417 7.2. Informative References 419 [RFC4272] Murphy, S., "BGP Security Vulnerabilities Analysis", RFC 420 4272, January 2006 422 [I-D.sriram-bgpsec-design-choices] Sriram, K., "BGPsec Design Choices 423 and Summary of Supporting Discussions", draft-sriram-bgpsec-design- 424 choices, work-in-progress. 426 [RFC7353] Bellovin, S., R. Bush, and D. Ward, "Security Requirements 427 for BGP Path Validation", RFC 7353, August 2014. 429 Authors' Addresses 431 Matt Lepinski 432 BBN Technologies 433 10 Moulton Street 434 Cambridge MA 02138 436 Email: mlepinski.ietf@gmail.com 438 Sean Turner 439 IECA, Inc. 440 3057 Nutley Street, Suite 106 441 Fairfax, VA 22031 443 Email: turners@ieca.com