RPKI-Based Origin Validation Operation
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This is an older version of an Internet-Draft that was ultimately published as RFC 7115.
|Last updated||2013-10-01 (Latest revision 2013-09-05)|
|RFC stream||Internet Engineering Task Force (IETF)|
SECDIR Last Call review by Taylor Yu Has nits
|Additional resources||Mailing list discussion|
|Stream||WG state||Submitted to IESG for Publication|
|Document shepherd||Chris Morrow|
|Shepherd write-up||Show Last changed 2013-09-16|
|IESG||IESG state||Waiting for Writeup|
|Responsible AD||Stewart Bryant|
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|IANA||IANA review state||IANA OK - No Actions Needed|
Network Working Group R. Bush Internet-Draft Internet Initiative Japan Intended status: Best Current Practice September 06, 2013 Expires: March 10, 2014 RPKI-Based Origin Validation Operation draft-ietf-sidr-origin-ops-21 Abstract Deployment of RPKI-based BGP origin validation has many operational considerations. This document attempts to collect and present those which are most critical. It is expected to evolve as RPKI-based origin validation continues to be deployed and the dynamics are better understood. 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 March 10, 2014. Copyright Notice Copyright (c) 2013 IETF Trust and the persons identified as the document authors. All rights reserved. Bush Expires March 10, 2014 [Page 1] Internet-Draft RPKI-Based Origin Validation Operation September 2013 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 . . . . . . . . . . . . . . . . . . . . . . . . 2 2. Suggested Reading . . . . . . . . . . . . . . . . . . . . . . 3 3. RPKI Distribution and Maintenance . . . . . . . . . . . . . . 3 4. Within a Network . . . . . . . . . . . . . . . . . . . . . . 6 5. Routing Policy . . . . . . . . . . . . . . . . . . . . . . . 6 6. Notes . . . . . . . . . . . . . . . . . . . . . . . . . . . . 8 7. Security Considerations . . . . . . . . . . . . . . . . . . . 9 8. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 9 9. Acknowledgments . . . . . . . . . . . . . . . . . . . . . . . 9 10. References . . . . . . . . . . . . . . . . . . . . . . . . . 9 10.1. Normative References . . . . . . . . . . . . . . . . . . 9 10.2. Informative References . . . . . . . . . . . . . . . . . 10 Author's Address . . . . . . . . . . . . . . . . . . . . . . . . 11 1. Introduction RPKI-based origin validation relies on widespread deployment of the Resource Public Key Infrastructure (RPKI) [RFC6480]. How the RPKI is distributed and maintained globally is a serious concern from many aspects. While the global RPKI is in the early stages of deployment, there is no single root trust anchor, initial testing is being done by the RIRs, and there are technical testbeds. It is thought that origin validation based on the RPKI will continue to be deployed incrementally over the next few years. It is assumed that eventually there must be a single root trust anchor for the public address space. Origin validation needs to be done only by an AS's border routers and is designed so that it can be used to protect announcements which are originated by any network participating in Internet BGP routing: large providers, upstreams and down-streams, and by small stub/ enterprise/edge routers. Bush Expires March 10, 2014 [Page 2] Internet-Draft RPKI-Based Origin Validation Operation September 2013 Origin validation has been designed to be deployed on current routers without significant hardware upgrade. It should be used in border routers by operators from large backbones to small stub/entetprise/ edge networks. RPKI-based origin validation has been designed so that, with prudent local routing policies, there is little risk that what is seen as today's normal Internet routing is threatened by imprudent deployment of the global RPKI, see Section 5. 2. Suggested Reading It is assumed that the reader understands BGP, [RFC4271], the RPKI, see [RFC6480], the RPKI Repository Structure, see [RFC6481], Route Origin Authorizations (ROAs), see [RFC6482], the RPKI to Router Protocol, see [RFC6810], RPKI-based Prefix Validation, see [RFC6811], and Ghostbusters Records, see [RFC6493]. 3. RPKI Distribution and Maintenance The RPKI is a distributed database containing certificates, CRLs, manifests, ROAs, and Ghostbusters Records as described in [RFC6481]. Policies and considerations for RPKI object generation and maintenance are discussed elsewhere. The RPKI repository design [RFC6481] anticipated an hierarchic organization of repositories, as this seriously affects the performance of relying parties gathering data. Publishing parties SHOULD implement hierarchic directory structures. A local relying party valid cache containing all RPKI data may be gathered from the global distributed database using the rsync protocol, [RFC5781], and a validation tool such as rcynic [rcynic]. Validated caches may also be created and maintained from other validated caches. Network operators SHOULD take maximum advantage of this feature to minimize load on the global distributed RPKI database. Of course, the recipient relying parties SHOULD re- validate the data. As Trust Anchor Locators (TALs), see [RFC6490], are critical to the RPKI trust model, operators should be very careful in their initial selection and vigilant in their maintenance. Bush Expires March 10, 2014 [Page 3] Internet-Draft RPKI-Based Origin Validation Operation September 2013 Timing of inter-cache synchronization, and synchronization between caches and the global RPKI, is outside the scope of this document, and depends on things such as how often routers feed from the caches, how often the operator feels the global RPKI changes significantly, etc. As inter-cache synchronization within an operator's network does not impact global RPKI resources, an operator MAY choose to synchronize quite frequently. As RPKI-based origin validation relies on the availability of RPKI data, operators SHOULD locate caches close to routers that require these data and services. 'Close' is, of course, complex. One should consider trust boundaries, routing bootstrap reachability, latency, etc. If insecure transports are used between an operator's cache and their router(s), the Transport Security recommendations in [RFC6810] SHOULD be followed. In particular, operators MUST NOT use insecure transports between their routers and RPKI caches located in other Autonomous Systems. For redundancy, a router SHOULD peer with more than one cache at the same time. Peering with two or more, at least one local and others remote, is recommended. If an operator trusts upstreams to carry their traffic, they MAY also trust the RPKI data those upstreams cache, and SHOULD peer with caches made available to them by those upstreams. Note that this places an obligation on those upstreams to maintain fresh and reliable caches, and to make them available to their customers. And, as usual, the recipient SHOULD re-validate the data. A transit provider or a network with peers SHOULD validate origins in announcements made by upstreams, down-streams, and peers. They still SHOULD trust the caches provided by their upstreams. Before issuing a ROA for a super-block, an operator MUST ensure that all sub-allocations from that block which are announced by other ASs, e.g. customers, have correct ROAs in the RPKI. Otherwise, issuing a ROA for the super-block will cause the announcements of sub- allocations with no ROAs to be viewed as Invalid, see [RFC6811]. Use of RPKI-based origin validation removes any need to originate more specifics into BGP to protect against mis-origination of a less specific prefix. Having a ROA for the covering prefix will protect it. Bush Expires March 10, 2014 [Page 4] Internet-Draft RPKI-Based Origin Validation Operation September 2013 To aid translation of ROAs into efficient search algorithms in routers, ROAs SHOULD be as precise as possible, i.e. match prefixes as announced in BGP. E.g. software and operators SHOULD avoid use of excessive max length values in ROAs unless operationally necessary. One advantage of minimal ROA length is that the forged origin attack does not work for sub-prefixes that are not covered by overly long max length. E.g. if, instead of 10.0.0.0/16-24, one issues 10.0.0.0/ 16 and 10.0.42.0/24, a forged origin attack can not succeed against 10.0.66.0/24. They must attack the whole /16, which is more likely to be noticed because of its size. Therefore, ROA generation software MUST use the prefix length as the max length if the user does not specify a max length. RFC EDITOR PLEASE REMOVE THIS PARAGRAPH: The above example does not use a standard documentation prefix as it needs a /16 so that a /24 can hole punch. As anything longer than a /24 is not globally routed, a /24 with a /25 (or whatever) hole would not be realistic and the ops reader would spend their energy on that anomaly instead of the example. Operators SHOULD be conservative in use of max length in ROAs. E.g., if a prefix will have only a few sub-prefixes announced, multiple ROAs for the specific announcements SHOULD be used as opposed to one ROA with a long max length. Operators owning prefix P should issue ROAs for all ASs which may announce P. If a prefix is legitimately announced by more than one AS, ROAs for all of the ASs SHOULD be issued so that all are considered Valid. An environment where private address space is announced in eBGP the operator MAY have private RPKI objects which cover these private spaces. This will require a trust anchor created and owned by that environment, see [I-D.ietf-sidr-ltamgmt]. Operators issuing ROAs may have customers which announce their own prefixes and ASs into global eBGP but who do not wish to go though the work to manage the relevant certificates and ROAs. Operators SHOULD offer to provision the RPKI data for these customers just as they provision many other things for them. While an operator using RPKI data MAY choose any polling frequency they wish for ensuring they have a fresh RPKI cache. However, if they use RPKI data as an input to operational routing decisions, they SHOULD ensure local caches inside their AS are synchronized with each other at least every four to six hours. Bush Expires March 10, 2014 [Page 5] Internet-Draft RPKI-Based Origin Validation Operation September 2013 Operators should use tools which warn them of any impending ROA or certificate expiry which could affect the validity of their own data. Ghostbuster Records, see [RFC6493], can be used to facilitate contact with upstream CAs to effect repair. 4. Within a Network Origin validation need only be done by edge routers in a network, those which border other networks/ASs. A validating router will use the result of origin validation to influence local policy within its network, see Section 5. In deployment this policy should fit into the AS's existing policy, preferences, etc. This allows a network to incrementally deploy validation-capable border routers. The operator should be aware that RPKI-based origin validation, 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. 5. Routing Policy Origin validation based on the RPKI marks a received announcement as having an origin which is Valid, NotFound, or Invalid, see [RFC6811]. How this is used in routing SHOULD be specified by the operator's local policy. Local policy using relative preference is suggested to manage the uncertainty associated with a system in early deployment, applying local policy to eliminate the threat of unreachability of prefixes due to ill-advised certification policies and/or incorrect certification data. E.g. until the community feels comfortable relying on RPKI data, routing on Invalid origin validity, though at a low preference, MAY occur. Operators should be aware that accepting Invalid announcements, no matter how de-preffed, will often be the equivalent of treating them as fully Valid. Consider having a ROA for AS 42 for prefix 10.0.0.0/ 16-24. A BGP announcement for 10.0.666.0/24 from AS 666 would be Invalid. But if policy is not configured to discard it, then longest match forwarding will send packets toward AS 666 no matter the value of local preference. As origin validation will be rolled out incrementally, coverage will be incomplete for a long time. Therefore, routing on NotFound validity state SHOULD be done for a long time. As the transition moves forward, the number of BGP announcements with validation state Bush Expires March 10, 2014 [Page 6] Internet-Draft RPKI-Based Origin Validation Operation September 2013 NotFound should decrease. Hence an operator's policy SHOULD NOT be overly strict, and should prefer Valid announcements, attaching a lower preference to, but still using, NotFound announcements, and dropping or giving a very low preference to Invalid announcements. Merely de-preffing Invalids is ill-advised, see previous paragraph. Some providers may choose to set Local-Preference based on the RPKI validation result. Other providers may not want the RPKI validation result to be more important than AS-path length -- these providers would need to map RPKI validation result to some BGP attribute that is evaluated in BGP's path selection process after AS-path is evaluated. Routers implementing RPKI-based origin validation MUST provide such options to operators. Local-Preference may be used to carry both the validity state of a prefix along with it's traffic engineering characteristic(s). It is likely that an operator already using Local-Preference will have to change policy so they can encode these two separate characteristics in the same BGP attribute without negatively impact or opening privilege escalation attacks. When using a metric which is also influenced by other local policy, an operator should be careful not to create privilege upgrade vulnerabilities. E.g. if Local Pref is set depending on validity state, be careful that peer community signaling SHOULD NOT upgrade an Invalid announcement to Valid or better. Announcements with Valid origins SHOULD be preferred over those with NotFound or Invalid origins, if the latter are accepted at all. Announcements with NotFound origins SHOULD be preferred over those with Invalid origins. Announcements with Invalid origins SHOULD NOT be used, but MAY be used to meet special operational needs. In such circumstances, the announcement SHOULD have a lower preference than that given to Valid or NotFound. When first deploying origin validation, it may be prudent to not drop announcements with Invalid orgins until inspection of logs, SNMP, or other data indicate that the correct result would be obtained. Validity state signaling SHOULD NOT be accepted from a neighbor AS. The validity state of a received announcement has only local scope due to issues such as scope of trust, RPKI synchrony, and [I-D.ietf-sidr-ltamgmt]. Bush Expires March 10, 2014 [Page 7] Internet-Draft RPKI-Based Origin Validation Operation September 2013 6. Notes 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 than another cache or router. There is no 'fix' for this, it is the nature of distributed data with distributed caches. Operators should beware that RPKI caches are loosely synchronized, even within a single AS. Thus, changes to the validity state of prefixes could be different within an operator's network. In addition, there is no guaranteed interval from when an RPKI cache is updated to when that new information may be pushed or pulled into a set of routers via this protocol. This may result in sudden shifts of traffic in the operator's network, until all of the routers in the AS have reached equilibrium with the validity state of prefixes reflected in all of the RPKI caches. It is hoped that testing and deployment will produce advice on relying party cache loading and timing. There is some uncertainty about the origin AS of aggregates and what, if any, ROA can be used. The long range solution to this is the deprecation of AS-SETs, see [RFC6472]. As reliable access to the global RPKI and an operator's caches (and possibly other hosts, e.g. DNS root servers) is important, an operator SHOULD take advantage of relying party tools which report changes in BGP or RPKI data which would negatively affect validation of such prefixes. Operators should be aware that there is a trade-off in placement of an RPKI repository in address space for which the repository's content is authoritative. On one hand, an operator will wish to maximize control over the repository. On the other hand, if there are reachability problems to the address space, changes in the repository to correct them may not be easily accessed by others. Operators who manage certificates SHOULD associate RPKI Ghostbusters Records (see [RFC6493]) with each publication point they control. These are publication points holding the CRL, ROAs, and other signed objects issued by the operator, and made available to other ASs in support of routing on the public Internet. Routers which perform RPKI-based origin validation must support Four- octet AS Numbers (see [RFC6793]), as, among other things, it is not reasonable to generate ROAs for AS 23456. Bush Expires March 10, 2014 [Page 8] Internet-Draft RPKI-Based Origin Validation Operation September 2013 Software which produces filter lists or other control forms for routers where the target router does not support Four-octet AS Numbers (see [RFC6793]) must be prepared to accept Four-octet AS Numbers and generate the appropriate two-octet output. As a router must evaluate certificates and ROAs which are time dependent, routers' clocks MUST be correct to a tolerance of approximately an hour. Servers should provide time service, such as [RFC5905], to client routers. 7. Security Considerations As the BGP origin AS of an update is not signed, origin validation is open to malicious spoofing. Therefore, RPKI-based origin validation is expected to deal only with inadvertent mis-advertisement. Origin validation does not address the problem of AS-Path validation. Therefore paths are open to manipulation, either malicious or accidental. As BGP does not ensure that traffic will flow via the paths it advertises, the data plane may not follow the control plane. Be aware of the class of privilege escalation issues discussed in Section 5 above. 8. IANA Considerations This document has no IANA Considerations. 9. Acknowledgments The author wishes to thank Shane Amante, Rob Austein, Steve Bellovin, Jay Borkenhagen, Wes George, Seiichi Kawamura, Steve Kent, Pradosh Mohapatra, Chris Morrow, Sandy Murphy, Eric Osterweil, Keyur Patel, Heather and Jason Schiller, John Scudder, Kotikalapudi Sriram, Maureen Stillman, and Dave Ward. 10. References 10.1. Normative References [RFC2119] Bradner, S., "Key words for use in RFCs to Indicate Requirement Levels", BCP 14, RFC 2119, March 1997. Bush Expires March 10, 2014 [Page 9] Internet-Draft RPKI-Based Origin Validation Operation September 2013 [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. [RFC6490] Huston, G., Weiler, S., Michaelson, G., and S. Kent, "Resource Public Key Infrastructure (RPKI) Trust Anchor Locator", RFC 6490, February 2012. [RFC6493] Bush, R., "The Resource Public Key Infrastructure (RPKI) Ghostbusters Record", RFC 6493, February 2012. [RFC6793] Vohra, Q. and E. Chen, "BGP Support for Four-Octet Autonomous System (AS) Number Space", RFC 6793, December 2012. [RFC6810] Bush, R. and R. Austein, "The Resource Public Key Infrastructure (RPKI) to Router Protocol", RFC 6810, January 2013. [RFC6811] Mohapatra, P., Scudder, J., Ward, D., Bush, R., and R. Austein, "BGP Prefix Origin Validation", RFC 6811, January 2013. 10.2. Informative References [I-D.ietf-sidr-ltamgmt] Reynolds, M., Kent, S., and M. Lepinski, "Local Trust Anchor Management for the Resource Public Key Infrastructure", draft-ietf-sidr-ltamgmt-08 (work in progress), April 2013. [RFC4271] Rekhter, Y., Li, T., and S. Hares, "A Border Gateway Protocol 4 (BGP-4)", RFC 4271, January 2006. [RFC5781] Weiler, S., Ward, D., and R. Housley, "The rsync URI Scheme", RFC 5781, February 2010. [RFC5905] Mills, D., Martin, J., Burbank, J., and W. Kasch, "Network Time Protocol Version 4: Protocol and Algorithms Specification", RFC 5905, June 2010. [RFC6472] Kumari, W. and K. Sriram, "Recommendation for Not Using AS_SET and AS_CONFED_SET in BGP", BCP 172, RFC 6472, December 2011. Bush Expires March 10, 2014 [Page 10] Internet-Draft RPKI-Based Origin Validation Operation September 2013 [RFC6480] Lepinski, M. and S. Kent, "An Infrastructure to Support Secure Internet Routing", RFC 6480, February 2012. [rcynic] , "rcynic read-me", , <http://subvert-rpki.hactrn.net/rcynic/README>. Author's Address Randy Bush Internet Initiative Japan 5147 Crystal Springs Bainbridge Island, Washington 98110 US Email: firstname.lastname@example.org Bush Expires March 10, 2014 [Page 11]