



Internet Engineering Task Force (IETF)                            Z. Yan
Request for Comments: 9455                                         CNNIC
BCP: 238                                                         R. Bush
Category: Best Current Practice          IIJ Research Lab & Arrcus, Inc.
ISSN: 2070-1721                                                  G. Geng
                                                        Jinan University
                                                              T. de Kock
                                                                RIPE NCC
                                                                  J. Yao
                                                                   CNNIC
                                                             August 2023


   Avoiding Route Origin Authorizations (ROAs) Containing Multiple IP
                                Prefixes

Abstract

   When using the Resource Public Key Infrastructure (RPKI), address
   space holders need to issue Route Origin Authorization (ROA)
   object(s) to authorize one or more Autonomous Systems (ASes) to
   originate BGP routes to IP address prefix(es).  This memo discusses
   operational problems that may arise from ROAs containing multiple IP
   prefixes and recommends that each ROA contain a single IP prefix.

Status of This Memo

   This memo documents an Internet Best Current Practice.

   This document is a product of the Internet Engineering Task Force
   (IETF).  It represents the consensus of the IETF community.  It has
   received public review and has been approved for publication by the
   Internet Engineering Steering Group (IESG).  Further information on
   BCPs is available in Section 2 of RFC 7841.

   Information about the current status of this document, any errata,
   and how to provide feedback on it may be obtained at
   https://www.rfc-editor.org/info/rfc9455.

Copyright Notice

   Copyright (c) 2023 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
   (https://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 Revised BSD License text as described in Section 4.e of the
   Trust Legal Provisions and are provided without warranty as described
   in the Revised BSD License.

Table of Contents

   1.  Introduction
   2.  Terminology
   3.  Problem Statement
   4.  Recommendations
   5.  Security Considerations
   6.  IANA Considerations
   7.  Normative References
   Acknowledgements
   Authors' Addresses

1.  Introduction

   In the RPKI, a ROA, which is a digitally signed object, identifies
   that a single AS has been authorized by the address space holder to
   originate BGP routes to one or more IP prefixes within the related
   address space [RFC6482].

   Each ROA contains an asID field and an ipAddrBlocks field.  The asID
   field contains a single AS number that is authorized to originate
   routes to the given IP address prefix(es).  The ipAddrBlocks field
   contains one or more IP address prefixes to which the AS is
   authorized to originate the routes.

   If the address space holder needs to authorize more than one AS to
   advertise the same set of IP prefixes, multiple ROAs must be issued
   (one for each AS number [RFC6480]).  Prior to this document, there
   was no guidance recommending the issuance of a separate ROA for each
   IP prefix or a single ROA containing multiple IP prefixes.

2.  Terminology

   The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT",
   "SHOULD", "SHOULD NOT", "RECOMMENDED", "NOT RECOMMENDED", "MAY", and
   "OPTIONAL" in this document are to be interpreted as described in
   BCP 14 [RFC2119] [RFC8174] when, and only when, they appear in all
   capitals, as shown here.

3.  Problem Statement

   An address space holder can issue a separate ROA for each of its
   routing announcements.  Alternatively, for a given asID, it can issue
   a single ROA for multiple routing announcements, or even for all of
   its routing announcements.  Since a given ROA is either valid or
   invalid, the routing announcements for which that ROA was issued will
   "share fate" when it comes to RPKI validation.  Currently, no
   existing RFCs provide recommendations about what kinds of ROAs to
   issue: one per prefix or one for multiple routing announcements.  The
   problem of fate-sharing was not discussed or addressed.

   In the RPKI trust chain, the Certification Authority (CA) certificate
   issued by a parent CA to a delegatee of some resources may be revoked
   by the parent at any time, which would result in changes to resources
   specified in the certificate extensions defined in [RFC3779].  Any
   ROA object that includes resources that are a) no longer entirely
   contained in the new CA certificate or b) contained in a new CA
   certificate that has not yet been discovered by Relying Party (RP)
   software will be rejected as invalid.  Since ROA invalidity affects
   all routes specified in that ROA, unchanged resources with associated
   routes via that asID cannot be separated from those affected by the
   change in CA certificate validity.  They will fall under this invalid
   ROA even though there was no intent to change their validity.  Had
   these resources been in a separate ROA, there would be no change to
   the issuing CA certificate and therefore no subsequent invalidity.

   CAs have to carefully coordinate ROA updates with updates to a
   resource certificate.  This process may be automated if a single
   entity manages both the parent CA and the CA issuing the ROAs
   (Scenario D in [RFC8211], Section 3.4).  However, in other deployment
   scenarios, this coordination becomes more complex.

   As there is a single expiration time for the entire ROA, expiration
   will affect all prefixes in the ROA.  Thus, changes to the ROA for
   any of the prefixes must be synchronized with changes to other
   prefixes, especially when authorization for a prefix is time bounded.
   Had these prefixes been in separately issued ROAs, the validity
   interval would be unique to each ROA, and invalidity would only be
   affected by reissuance of the specific issuing parent CA certificate.

   A prefix could be allowed to originate from an AS only for a specific
   period of time, for example, if the IP prefix was leased out
   temporarily.  If a ROA with multiple IP prefixes was used, this would
   be more difficult to manage, and potentially be more error-prone.
   Similarly, more complex routing may require changes in asID or routes
   for a subset of prefixes.  Reissuance of a ROA might result in
   changes to the validity of previously received BGP routes covered by
   the ROA's prefixes.  There will be no change to the validity of
   unaffected routes if a) the time-limited resources are in separate
   ROAs, or b) for more complex routing, each change in asID or a change
   in routes for a given prefix is reflected in a change to a discrete
   ROA.

   The use of ROA with a single IP prefix can minimize these side
   effects.  It avoids fate-sharing irrespective of the cause, where the
   parent CA issuing each ROA remains valid and where each ROA itself
   remains valid.

4.  Recommendations

   Unless the CA has good reasons to the contrary, an issued ROA SHOULD
   contain a single IP prefix.

5.  Security Considerations

   Issuing separate ROAs for independent IP prefixes may increase the
   file-fetch burden on the RP during validation.

6.  IANA Considerations

   This document has no IANA actions.

7.  Normative References

   [RFC2119]  Bradner, S., "Key words for use in RFCs to Indicate
              Requirement Levels", BCP 14, RFC 2119,
              DOI 10.17487/RFC2119, March 1997,
              <https://www.rfc-editor.org/info/rfc2119>.

   [RFC3779]  Lynn, C., Kent, S., and K. Seo, "X.509 Extensions for IP
              Addresses and AS Identifiers", RFC 3779,
              DOI 10.17487/RFC3779, June 2004,
              <https://www.rfc-editor.org/info/rfc3779>.

   [RFC6480]  Lepinski, M. and S. Kent, "An Infrastructure to Support
              Secure Internet Routing", RFC 6480, DOI 10.17487/RFC6480,
              February 2012, <https://www.rfc-editor.org/info/rfc6480>.

   [RFC6482]  Lepinski, M., Kent, S., and D. Kong, "A Profile for Route
              Origin Authorizations (ROAs)", RFC 6482,
              DOI 10.17487/RFC6482, February 2012,
              <https://www.rfc-editor.org/info/rfc6482>.

   [RFC8174]  Leiba, B., "Ambiguity of Uppercase vs Lowercase in RFC
              2119 Key Words", BCP 14, RFC 8174, DOI 10.17487/RFC8174,
              May 2017, <https://www.rfc-editor.org/info/rfc8174>.

   [RFC8211]  Kent, S. and D. Ma, "Adverse Actions by a Certification
              Authority (CA) or Repository Manager in the Resource
              Public Key Infrastructure (RPKI)", RFC 8211,
              DOI 10.17487/RFC8211, September 2017,
              <https://www.rfc-editor.org/info/rfc8211>.

Acknowledgements

   The authors wish to thank the following people for their reviews and
   contributions to this document: George Michaelson, Tim Bruijnzeels,
   Job Snijders, Di Ma, Geoff Huston, Tom Harrison, Rob Austein, Stephen
   Kent, Christopher Morrow, Russ Housley, Ching-Heng Ku, Keyur Patel,
   Cuiling Zhang, and Kejun Dong.  Thanks are also due to Sean Turner
   for the Security Area Directorate review.

   This work was supported by the Beijing Nova Program of Science and
   Technology under grant Z191100001119113.

Authors' Addresses

   Zhiwei Yan
   CNNIC
   No.4 South 4th Street, Zhongguancun
   Beijing
   100190
   China
   Email: yanzhiwei@cnnic.cn


   Randy Bush
   IIJ Research Lab & Arrcus, Inc.
   5147 Crystal Springs
   Bainbridge Island, Washington 98110
   United States of America
   Email: randy@psg.com


   Guanggang Geng
   Jinan University
   No.601, West Huangpu Avenue
   Guangzhou
   510632
   China
   Email: gggeng@jnu.edu.cn


   Ties de Kock
   RIPE NCC
   Stationsplein 11
   Amsterdam
   Netherlands
   Email: tdekock@ripe.net


   Jiankang Yao
   CNNIC
   No.4 South 4th Street, Zhongguancun
   Beijing
   100190
   China
   Email: yaojk@cnnic.cn
