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: [email protected]


  Randy Bush
  IIJ Research Lab & Arrcus, Inc.
  5147 Crystal Springs
  Bainbridge Island, Washington 98110
  United States of America
  Email: [email protected]


  Guanggang Geng
  Jinan University
  No.601, West Huangpu Avenue
  Guangzhou
  510632
  China
  Email: [email protected]


  Ties de Kock
  RIPE NCC
  Stationsplein 11
  Amsterdam
  Netherlands
  Email: [email protected]


  Jiankang Yao
  CNNIC
  No.4 South 4th Street, Zhongguancun
  Beijing
  100190
  China
  Email: [email protected]

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