Network Working Group S. Bellovin Internet-Draft Columbia University Intended status: Standards Track R. Bush Expires: August 2, 2011 Internet Initiative Japan, Inc. D. Ward Juniper Networks January 29, 2011 Security Requirements for BGP Path Validation draft-ymbk-bgpsec-reqs-00 Abstract This document describes requirements for a future BGP security protocol design to provide cryptographic assurance that the origin AS had the right to announce the prefix and to provide assurance of the AS Path of the announcement. Requirements Language The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT", "SHOULD", "SHOULD NOT", "RECOMMENDED", "MAY", and "OPTIONAL" in this document are to be interpreted as described in RFC 2119 [RFC2119]. Status of this Memo This Internet-Draft is submitted in full conformance with the provisions of BCP 78 and BCP 79. This document may not be modified, and derivative works of it may not be created, and it may not be published except as an Internet-Draft. 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 August 2, 2011. Copyright Notice Copyright (c) 2011 IETF Trust and the persons identified as the document authors. All rights reserved. Bellovin, et al. Expires August 2, 2011 [Page 1] Internet-Draft Requirements for BGP Path Validation January 2011 This document is subject to BCP 78 and the IETF Trust's Legal Provisions Relating to IETF Documents (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 . . . . . . . . . . . . . . . . . . . . . . . . . 3 2. Recommended Reading . . . . . . . . . . . . . . . . . . . . . . 3 3. General Requirements . . . . . . . . . . . . . . . . . . . . . 3 4. BGP UPDATE Security Requirements . . . . . . . . . . . . . . . 5 5. IANA Considerations . . . . . . . . . . . . . . . . . . . . . . 5 6. Security Considerations . . . . . . . . . . . . . . . . . . . . 6 7. Acknowledgments . . . . . . . . . . . . . . . . . . . . . . . . 6 8. References . . . . . . . . . . . . . . . . . . . . . . . . . . 6 8.1. Normative References . . . . . . . . . . . . . . . . . . . 6 8.2. Informative References . . . . . . . . . . . . . . . . . . 6 Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . . 7 Bellovin, et al. Expires August 2, 2011 [Page 2] Internet-Draft Requirements for BGP Path Validation January 2011 1. Introduction RPKI-based Origin Validation ([I-D.ietf-sidr-pfx-validate]) provides a measure of resilience to accidental mis-origination of prefixes. But it provides neither cryptographic assurance (announcements are not signed), nor assurance of the AS Path of the announcement. This document describes requirements to be placed on a future BGP security protocol, herein termed BGPsec, intended to satisfy these gaps. The threat model assumed here is documented in [RFC4593] and [I-D.kent-bgpsec-threats]. The output of a router applying BGPsec to a received signed announcement is either Valid or Unverified. There are no shades of grey. 2. Recommended Reading This document assumes knowledge of the RPKI see [I-D.ietf-sidr-arch], the RPKI Repository Structure, see [I-D.ietf-sidr-repos-struct]. This document assumes ongoing incremental deployment of ROAs, see [I-D.ietf-sidr-roa-format], the RPKI to Router Protocol, see [I-D.ietf-sidr-rpki-rtr], and RPKI-based Prefix Validation, see [I-D.ietf-sidr-pfx-validate]. 3. General Requirements The following are general requirements for a BGPsec protocol: 3.1 A BGPsec design MUST be able to be incrementally deployed on today's Internet. 3.2 A BGPsec design proposal MUST provide analysis of the operational considerations for deployment and particularly of incremental deployment, e.g, contiguous islands, non-contiguous islands, universal deployment, etc.. 3.3 As cryptographic payloads and loading on routers are likely to seriously increase, a BGPsec design may require use of new hardware. It must be possible to build routers that do BGPsec with within acceptable (to operators) bounds of cost and performance. Bellovin, et al. Expires August 2, 2011 [Page 3] Internet-Draft Requirements for BGP Path Validation January 2011 3.4 A BGPsec design need not prevent attacks on data plane traffic. It need not assure that the data plane even follows the control plane. 3.5 A BGPsec design MUST resist attacks by an enemy who has access to the link layer, per Section 3.1.1.2 of [RFC4593]. In particular, such a design must provide mechanisms for authentication of all data, including protecting against message insertion, deletion, modification, or replay. Mechanisms that suffice include TCP sessions authenticated with IPsec [RFC4301] or TLS [RFC5246]. 3.6 A BGPsec design MAY make use of a security infrastructure (e.g., a PKI) to distribute authenticated data used as input to routing decisions. Such data include information about holdings of address space and ASNs, and assertions about binding of address space to ASNs. 3.7 If message signing increases message size, the 4096 byte limit on BGP PDU size MAY be removed. 3.8 It is entirely OPTIONAL to secure AS SETs and prefix aggregation. The long range solution to this is the deprecation of AS-SETs, see [I-D.wkumari-deprecate-as-sets]. 3.9 If a BGPsec design uses signed NLRIs, it need NOT handle multiple NLRIs in a single UPDATE, given the impossibility of splitting a signed message while preserving the signature. 3.10 A BGPsec design MUST enable each BGPsec speaker to configure use of the security mechanism on a per-peer basis. 3.11 A BGPsec design MUST provide backward compatibility in the message formatting, transmission, and processing of routing information carried through a mixed security environment. Message formatting in a fully secured environment MAY be handled in a non-backward compatible manner. 3.12 A BGPsec design MUST allow local policy to determine the trust level for a specific route so that routing preference and policy can be applied to its inclusion in the RIB. Such mechanisms MUST conform with [I-D.ietf-sidr-ltamgmt]. 3.13 If a BGPsec design makes use of a security infrastructure, that infrastructure SHOULD enable each network operator to select the entities it will trust when authenticating data in the security infrastructure. See, for example, [I-D.ietf-sidr-ltamgmt]. Bellovin, et al. Expires August 2, 2011 [Page 4] Internet-Draft Requirements for BGP Path Validation January 2011 3.14 A BGPsec design MUST NOT require operators to reveal proprietary data. This includes peering, customer, and provider relationships, an ISP's internal infrastructure, etc. Though it is understood that some data are revealed to the savvy seeker by BGP, traceroute, etc. today. 3.15 A BGPsec design document SHOULD note security events that are significant enough that they should be logged. The specific data to be logged are an implementation matter. 4. BGP UPDATE Security Requirements The following requirements must be met in the processing of BGP UPDATE messages: 4.1 A BGPsec design MUST enable each recipient of an UPDATE to formally validate that the origin AS in the message is authorized to originate a route to the prefix(es) in the UPDATE. 4.2 A BGPsec design MUST enable the recipient of an UPDATE to formally determine that the UPDATE has traversed the AS path indicated in the UPADTE. Note that this is more stringent than showing that the path is merely not impossible. 4.3 Replay of BGP UPDATE messages need not be completely prevented, but a BGPsec design MUST provide a mechanism to control the window of exposure to replay attacks. 4.4 Contents of the UPDATE message SHOULD be able to be authenticated in real-time as the message is processed. 4.5 The routing information base MAY also be re-authenticated periodically or in an event-driven manner, especially in response to events such as, for example. PKI updates. 4.6 Normal sanity checks of received announcements MUST be done, e.g. verification that the first element of the AS_PATH list corresponds to the locally configured AS of the peer from which an UPDATE was received. 5. IANA Considerations This document asks nothing of the IANA. Bellovin, et al. Expires August 2, 2011 [Page 5] Internet-Draft Requirements for BGP Path Validation January 2011 6. Security Considerations The data plane may not follow the control plane. Security for subscriber traffic is outside the scope of this document, and of BGP security in general. IETF standards for payload data security should be employed. While adoption of BGP security measures may ameliorate some classes of attacks on traffic, these measures are not a substitute for use of subscriber-based security. 7. Acknowledgments The author wishes to thank the authors of [I-D.ietf-rpsec-bgpsecrec], from whom we liberally stole, Russ Housley, Steve Kent, Sandy Murphy, John Scudder, and a number of others. 8. References 8.1. Normative References [I-D.kent-bgpsec-threats] Kent, S., "Threat Model for BGP Path Security", draft-kent-bgpsec-threats-00 (work in progress), January 2011. [RFC2119] Bradner, S., "Key words for use in RFCs to Indicate Requirement Levels", BCP 14, RFC 2119, March 1997. [RFC4593] Barbir, A., Murphy, S., and Y. Yang, "Generic Threats to Routing Protocols", RFC 4593, October 2006. 8.2. Informative References [I-D.ietf-rpsec-bgpsecrec] Christian, B. and T. Tauber, "BGP Security Requirements", draft-ietf-rpsec-bgpsecrec-10 (work in progress), November 2008. [I-D.ietf-sidr-arch] Lepinski, M. and S. Kent, "An Infrastructure to Support Secure Internet Routing", draft-ietf-sidr-arch-11 (work in progress), September 2010. [I-D.ietf-sidr-ltamgmt] Kent, S. and M. Reynolds, "Local Trust Anchor Management for the Resource Public Key Infrastructure", Bellovin, et al. Expires August 2, 2011 [Page 6] Internet-Draft Requirements for BGP Path Validation January 2011 draft-ietf-sidr-ltamgmt-00 (work in progress), November 2010. [I-D.ietf-sidr-pfx-validate] Mohapatra, P., Scudder, J., Ward, D., Bush, R., and R. Austein, "BGP Prefix Origin Validation", draft-ietf-sidr-pfx-validate-00 (work in progress), July 2010. [I-D.ietf-sidr-repos-struct] Huston, G., Loomans, R., and G. Michaelson, "A Profile for Resource Certificate Repository Structure", draft-ietf-sidr-repos-struct-06 (work in progress), November 2010. [I-D.ietf-sidr-roa-format] Lepinski, M., Kent, S., and D. Kong, "A Profile for Route Origin Authorizations (ROAs)", draft-ietf-sidr-roa-format-09 (work in progress), November 2010. [I-D.ietf-sidr-rpki-rtr] Bush, R. and R. Austein, "The RPKI/Router Protocol", draft-ietf-sidr-rpki-rtr-07 (work in progress), January 2011. [I-D.wkumari-deprecate-as-sets] Kumari, W., "Deprecation of BGP AS_SET, AS_CONFED_SET.", draft-wkumari-deprecate-as-sets-01 (work in progress), September 2010. [RFC4301] Kent, S. and K. Seo, "Security Architecture for the Internet Protocol", RFC 4301, December 2005. [RFC5246] Dierks, T. and E. Rescorla, "The Transport Layer Security (TLS) Protocol Version 1.2", RFC 5246, August 2008. Bellovin, et al. Expires August 2, 2011 [Page 7] Internet-Draft Requirements for BGP Path Validation January 2011 Authors' Addresses Steven M. Bellovin Columbia University 1214 Amsterdam Avenue, MC 0401 New York, New York 10027 US Phone: +1 212 939 7149 Email: bellovin@acm.org Randy Bush Internet Initiative Japan, Inc. 5147 Crystal Springs Bainbridge Island, Washington 98110 US Phone: +1 206 780 0431 x1 Email: randy@psg.com Dave Ward Juniper Networks 1194 N. Mathilda Ave. Sunnyvale, California 94089-1206 US Phone: +1-408-745-2000 Email: dward@juniper.net Bellovin, et al. Expires August 2, 2011 [Page 8]