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
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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
