Network Working Group R. Bush Internet-Draft Internet Initiative Japan Intended status: Best Current Practice January 5, 2017 Expires: July 9, 2017 BGPsec Operational Considerations draft-ietf-sidr-bgpsec-ops-16 Abstract Deployment of the BGPsec architecture and protocols has many operational considerations. This document attempts to collect and present the most critical and universal. It is expected to evolve as BGPsec is formalized and initially deployed. Requirements Language The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT", "SHOULD", "SHOULD NOT", "RECOMMENDED", "MAY", and "OPTIONAL" are to be interpreted as described in RFC 2119 [RFC2119] only when they appear in all upper case. They may also appear in lower or mixed case as English words, without normative meaning. Status of This Memo This Internet-Draft is submitted in full conformance with the provisions of BCP 78 and BCP 79. Internet-Drafts are working documents of the Internet Engineering Task Force (IETF). Note that other groups may also distribute working documents as Internet-Drafts. The list of current Internet- Drafts is at http://datatracker.ietf.org/drafts/current/. Internet-Drafts are draft documents valid for a maximum of six months and may be updated, replaced, or obsoleted by other documents at any time. It is inappropriate to use Internet-Drafts as reference material or to cite them other than as "work in progress." This Internet-Draft will expire on July 9, 2017. Copyright Notice Copyright (c) 2017 IETF Trust and the persons identified as the document authors. All rights reserved. This document is subject to BCP 78 and the IETF Trust's Legal Provisions Relating to IETF Documents Bush Expires July 9, 2017 [Page 1] Internet-Draft BGPsec Operational Considerations January 2017 (http://trustee.ietf.org/license-info) in effect on the date of publication of this document. Please review these documents carefully, as they describe your rights and restrictions with respect to this document. Code Components extracted from this document must include Simplified BSD License text as described in Section 4.e of the Trust Legal Provisions and are provided without warranty as described in the Simplified BSD License. Table of Contents 1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . 2 2. Suggested Reading . . . . . . . . . . . . . . . . . . . . . . 3 3. RPKI Distribution and Maintenance . . . . . . . . . . . . . . 3 4. AS/Router Certificates . . . . . . . . . . . . . . . . . . . 3 5. Within a Network . . . . . . . . . . . . . . . . . . . . . . 3 6. Considerations for Edge Sites . . . . . . . . . . . . . . . . 4 7. Routing Policy . . . . . . . . . . . . . . . . . . . . . . . 5 8. Notes . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6 9. Security Considerations . . . . . . . . . . . . . . . . . . . 7 10. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 7 11. Acknowledgments . . . . . . . . . . . . . . . . . . . . . . . 7 12. References . . . . . . . . . . . . . . . . . . . . . . . . . 7 12.1. Normative References . . . . . . . . . . . . . . . . . . 7 12.2. Informative References . . . . . . . . . . . . . . . . . 8 Author's Address . . . . . . . . . . . . . . . . . . . . . . . . 9 1. Introduction Origin Validation based on the Resource Public Key Infrastructure (RPKI), [RFC6811], is in its early phases. As BGPsec, [I-D.ietf-sidr-bgpsec-protocol] may require larger memory and/or more modern CPUs, it expected to be deployed incrementally over a longer time span. BGPsec is a new protocol with many operational considerations which this document attempts to describe. As with most operational practices, this document will likely evolve. BGPsec relies on widespread propagation of the RPKI [RFC6480]. How the RPKI is distributed and maintained globally and within an operator's infrastructure may be different for BGPsec than for origin validation. BGPsec needs to be spoken only by an AS's eBGP-speaking border routers. It is designed so that it can be used to protect announcements which are originated by resource constrained edge routers. This has special operational considerations, see Section 6. Different prefixes may have different timing and replay protection considerations. Bush Expires July 9, 2017 [Page 2] Internet-Draft BGPsec Operational Considerations January 2017 2. Suggested Reading It is assumed that the reader understands BGP, see [RFC4271], BGPsec, [I-D.ietf-sidr-bgpsec-protocol], the RPKI, see [RFC6480], the RPKI Repository Structure, see [RFC6481], and Route Origin Authorizations (ROAs), see [RFC6482]. 3. RPKI Distribution and Maintenance The considerations for RPKI objects (Certificates, Certificate Revocation Lists (CRLs), manifests, Ghostbusters Records [RFC6481]), Trust Anchor Locators (TALs) [RFC7730], cache behaviours of synchronisation and validation from the section on RPKI Distribution and Maintenance of [RFC7115] apply. Specific considerations relating to ROA objects do not apply to this document. 4. AS/Router Certificates As described in [I-D.ietf-sidr-rtr-keying] BGPsec-speaking routers are capable of generating their own public/private key-pairs and having their certificates signed and published in the RPKI by the RPKI CA system, and/or are given public/private key-pairs by the operator. A site/operator may use a single certificate/key in all their routers, one certificate/key per router, or any granularity in between. A large operator, concerned that a compromise of one router's key would make other routers vulnerable, may deploy a more complex certificate/key distribution burden to reduce this exposure. At the other end of the spectrum, an edge site with one or two routers may choose to use a single certificate/key. In anticipation of possible key compromise, a prudent operator SHOULD pre-provision each router's 'next' key in the RPKI so there is no propagation delay for provisioning the new key. 5. Within a Network BGPsec is spoken by edge routers in a network, those which border other networks/ASs. In an AS where edge routers speak BGPsec and therefore inject BGPsec paths into the iBGP, Route Reflectors MUST have BGPsec enabled if and only if there are eBGP speakers in their client cone, i.e. an RR client or the transitive closure of a client's customers. Bush Expires July 9, 2017 [Page 3] Internet-Draft BGPsec Operational Considerations January 2017 A BGPsec capable router MAY use the data it receives to influence local policy within its network, see Section 7. In deployment this policy should fit into the AS's existing policy, preferences, etc. This allows a network to incrementally deploy BGPsec enabled border routers. eBGP speakers which face more critical peers or up/downstreams would be candidates for early deployment. Both securing one's own announcements and validating received announcements should be considered in partial deployment. An operator should be aware that BGPsec, as any other policy change, can cause traffic shifts in their network. And, as with normal policy shift practice, a prudent operator has tools and methods to predict, measure, modify, etc. On the other hand, an operator wanting to monitor router loading, shifts in traffic, etc. might deploy incrementally while watching those and similar effects. BGPsec does not sign over communities, so they are not formally trustable. Additionally, outsourcing verification is not prudent security practice. Therefore an eBGP listener SHOULD NOT strongly trust unsigned security signaling, such as communities, received across a trust boundary. 6. Considerations for Edge Sites An edge site which does not provide transit and trusts its upstream(s) may only originate a signed prefix announcement and not validate received announcements. An Operator might need to use hardware with limited resources. In such cases, BGPsec protocol capability negotiation allows for a resource constrained edge router to hold only its own signing key(s) and sign its announcements, but not receive signed announcements. Therefore, the router would not have to deal with the majority of the RPKI, potentially saving the need for additional hardware. As the vast majority of ASs are stubs, and they announce the majority of prefixes, this allows for simpler and less expensive incremental deployment. It may also mean that edge sites concerned with routing security will be attracted to upstreams which support BGPsec. Bush Expires July 9, 2017 [Page 4] Internet-Draft BGPsec Operational Considerations January 2017 7. Routing Policy Unlike origin validation based on the RPKI, BGPsec marks a received announcement as Valid or Not Valid, there is no explicit NotFound state. In some sense, an unsigned BGP4 path is the equivalent of NotFound. How this is used in routing is up to the operator's local policy, similar to origin validation as in [RFC6811]. As BGPsec will be rolled out over years and does not allow for intermediate non-signing edge routers, coverage will be spotty for a long time. This presents a dilemma; should a router evaluating an inbound BGPsec_Path as Not Valid be very strict and discard it? On the other hand, it might be the only path to that prefix, and a very low local-preference would cause it to be used and propagated only if there was no alternative. Either choice is reasonable, but we recommend dropping because of the next point. Operators should be aware that accepting Not Valid announcements, no matter the local preference, will often be the equivalent of treating them as fully Valid. Local preference affects only routes to the same set of destinations. Consider having a Valid announcement from neighbor V for prefix 10.0.0.0/16 and an Not Valid announcement for 10.0.666.0/24 from neighbor I. If local policy on the router is not configured to discard the Not Valid announcement from I, then longest match forwarding will send packets to neighbor I no matter the value of local preference. Validation of signed paths is usually deployed at the eBGP edge. Local policy on the eBGP edge MAY convey the validation state of a BGP signed path through normal local policy mechanisms, e.g. setting a BGP community for internal use, or modifying a metric value such as local-preference or multi-exit discriminator (MED). Some may choose to use the large Local-Pref hammer. Others may choose to let AS-Path rule and set their internal metric, which comes after AS-Path in the BGP decision process. As the mildly stochastic timing of RPKI propagation may cause version skew across routers, an AS Path which does not validate at router R0 might validate at R1. Therefore, signed paths that are Not Valid and yet propagated (because they are chosen as best path) MUST NOT have signatures stripped and MUST be signed if sent to external BGPsec speakers. This implies that updates which a speaker judges to be Not Valid MAY be propagated to iBGP peers. Therefore, unless local policy ensures otherwise, a signed path learned via iBGP may be Not Valid. If Bush Expires July 9, 2017 [Page 5] Internet-Draft BGPsec Operational Considerations January 2017 needed, the validation state should be signaled by normal local policy mechanisms such as communities or metrics. On the other hand, local policy on the eBGP edge might preclude iBGP or eBGP announcement of signed AS Paths which are Not Valid. A BGPsec speaker receiving a path SHOULD perform origin validation per [RFC6811] and [RFC7115]. A route server is usually 'transparent', i.e. does not insert an AS into the path so as not to increase the AS hop count and thereby affect downstream path choices. But, with BGPsec, a client router R needs to be able to validate paths which are forward signed to R. But the sending router can not generate signatures to all the possible clients. Therefore a BGPsec-aware route server needs to validate the incoming BGPsec_Path, and to forward updates which can be validated by clients which must therefore know the route server's AS. This implies that the route server creates signatures per client including its own AS in the BGPsec_Path, forward signing to each client AS, see [I-D.ietf-sidr-bgpsec-protocol]. The route server uses pCount of zero to not increase the effective AS hop count, thereby retaining the intent of 'transparency'. If it is known that a BGPsec neighbor is not a transparent route server, or is otherwise validly using pCount=0 (e,g, see [I-D.ietf-sidr-as-migration]), and the router provides a knob to disallow a received pCount (of zero, that knob SHOULD be applied. Routers should disallow pCount 0 by default. To prevent exposure of the internals of BGP Confederations [RFC5065], a BGPsec speaker exporting to a non-member removes all intra- confederation Secure_Path segments. Therefore signing within the confederation will not cause external confusion even if non-unique private ASs are used. 8. Notes For protection from attacks replaying BGP data on the order of a day or longer old, re-keying routers with new keys (previously) provisioned in the RPKI is sufficient. For one approach, see [I-D.ietf-sidr-bgpsec-rollover] A router that once negotiated (and/or sent) BGPsec should not be expected to always do so. Like the DNS, the global RPKI presents only a loosely consistent view, depending on timing, updating, fetching, etc. Thus, one cache or router may have different data about a particular prefix or router Bush Expires July 9, 2017 [Page 6] Internet-Draft BGPsec Operational Considerations January 2017 than another cache or router. There is no 'fix' for this, it is the nature of distributed data with distributed caches. Operators who manage certificates SHOULD have RPKI GhostBuster Records (see [RFC6493]), signed indirectly by End Entity certificates, for those certificates on which others' routing depends for certificate and/or ROA validation. Operators should be aware of impending algorithm transitions, which will be rare and slow-paced, see [RFC6916]. They should work with their vendors to ensure support for new algorithms. As a router must evaluate certificates and ROAs which are time dependent, routers' clocks MUST be correct to a tolerance of approximately an hour. The common approach is for operators to deploy servers that provide time service, such as [RFC5905], to client routers. If a router has reason to believe its clock is seriously incorrect, e.g. it has a time earlier than 2011, it SHOULD NOT attempt to validate incoming updates. It SHOULD defer validation until it believes it is within reasonable time tolerance. 9. Security Considerations This document describes operational considerations for the deployment of BGPsec. The security considerations for BGPsec are described in [I-D.ietf-sidr-bgpsec-protocol]. 10. IANA Considerations This document has no IANA Considerations. 11. Acknowledgments The author wishes to thank Thomas King, Arnold Nipper, and Alvaro Retana, and the BGPsec design group. 12. References 12.1. Normative References [I-D.ietf-sidr-bgpsec-protocol] Lepinski, M., "BGPSEC Protocol Specification", draft-ietf- sidr-bgpsec-protocol-07 (work in progress), February 2013. [RFC2119] Bradner, S., "Key words for use in RFCs to Indicate Requirement Levels", BCP 14, RFC 2119, March 1997. Bush Expires July 9, 2017 [Page 7] Internet-Draft BGPsec Operational Considerations January 2017 [RFC6493] Bush, R., "The Resource Public Key Infrastructure (RPKI) Ghostbusters Record", RFC 6493, February 2012. [RFC6811] Mohapatra, P., Scudder, J., Ward, D., Bush, R., and R. Austein, "BGP Prefix Origin Validation", RFC 6811, January 2013. [RFC7115] Bush, R., "Origin Validation Operation Based on the Resource Public Key Infrastructure (RPKI)", BCP 185, RFC 7115, DOI 10.17487/RFC7115, January 2014, . [RFC7730] Huston, G., Weiler, S., Michaelson, G., and S. Kent, "Resource Public Key Infrastructure (RPKI) Trust Anchor Locator", RFC 7730, DOI 10.17487/RFC7730, January 2016, . 12.2. Informative References [I-D.ietf-sidr-as-migration] George, W. and S. Murphy, "BGPSec Considerations for AS Migration", draft-ietf-sidr-as-migration-06 (work in progress), December 2016. [I-D.ietf-sidr-bgpsec-rollover] Gagliano, R., Patel, K., and B. Weis, "BGPSEC router key rollover as an alternative to beaconing", draft-ietf-sidr- bgpsec-rollover-01 (work in progress), October 2012. [I-D.ietf-sidr-rtr-keying] Turner, S., Patel, K., and R. Bush, "Router Keying for BGPsec", draft-ietf-sidr-rtr-keying-01 (work in progress), February 2013. [RFC4271] Rekhter, Y., Li, T., and S. Hares, "A Border Gateway Protocol 4 (BGP-4)", RFC 4271, January 2006. [RFC5065] Traina, P., McPherson, D., and J. Scudder, "Autonomous System Confederations for BGP", RFC 5065, August 2007. [RFC5905] Mills, D., Martin, J., Burbank, J., and W. Kasch, "Network Time Protocol Version 4: Protocol and Algorithms Specification", RFC 5905, June 2010. [RFC6480] Lepinski, M. and S. Kent, "An Infrastructure to Support Secure Internet Routing", RFC 6480, February 2012. Bush Expires July 9, 2017 [Page 8] Internet-Draft BGPsec Operational Considerations January 2017 [RFC6481] Huston, G., Loomans, R., and G. Michaelson, "A Profile for Resource Certificate Repository Structure", RFC 6481, February 2012. [RFC6482] Lepinski, M., Kent, S., and D. Kong, "A Profile for Route Origin Authorizations (ROAs)", RFC 6482, February 2012. [RFC6916] Gagliano, R., Kent, S., and S. Turner, "Algorithm Agility Procedure for the Resource Public Key Infrastructure (RPKI)", BCP 182, RFC 6916, DOI 10.17487/RFC6916, April 2013, . Author's Address Randy Bush Internet Initiative Japan 5147 Crystal Springs Bainbridge Island, Washington 98110 US Email: randy@psg.com Bush Expires July 9, 2017 [Page 9]