RRDP Same-Origin Policy: Same-Origin Policy for the RPKI Repository Delta Protocol (RRDP)
RRDP references and redirects must stay on the Update Notification file's origin.
Snijders, J., "Same-Origin Policy for the RPKI Repository Delta Protocol (RRDP)", RFC 9674, DOI 10.17487/RFC9674, December 2024, <https://www.rfc-editor.org/info/rfc9674>.
@misc{rfc9674,
series = {Request for Comments},
number = 9674,
howpublished = {RFC 9674},
publisher = {RFC Editor},
doi = {10.17487/RFC9674},
url = {https://www.rfc-editor.org/info/rfc9674},
author = {J. Snijders},
title = {{Same-Origin Policy for the RPKI Repository Delta Protocol (RRDP)}},
pagetotal = 5,
year = 2024,
month = dec,
} RFC text
Contents
Internet Engineering Task Force (IETF) J. Snijders
Request for Comments: 9674 Fastly
Updates: 8182 December 2024
Category: Standards Track
ISSN: 2070-1721
Same-Origin Policy for the RPKI Repository Delta Protocol (RRDP)
Abstract
This document describes a Same-Origin Policy (SOP) requirement for
Resource Public Key Infrastructure (RPKI) Repository Delta Protocol
(RRDP) servers and clients. Application of a SOP in RRDP client/
server communication isolates resources such as Delta and Snapshot
files from different Repository Servers, reducing possible attack
vectors. This document updates RFC 8182.
Status of This Memo
This is an Internet Standards Track document.
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
Internet Standards 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/rfc9674.
Copyright Notice
Copyright (c) 2024 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
1.1. Requirements Language
2. Implications of Cross-Origin Resource Requests in RRDP
3. Changes to RFC 8182
3.1. New Requirements for RRDP Repository Servers
3.2. New Requirements for Relying Parties Using RRDP
4. Deployability in the Internet's Current RPKI
5. Security Considerations
6. IANA Considerations
7. References
7.1. Normative References
7.2. Informative References
Acknowledgements
Author's Address
1. Introduction
This document specifies a Same-Origin Policy (SOP) requirement for
RPKI Repository Delta Protocol (RRDP) servers and clients. The SOP
concept is a security mechanism to restrict how a document loaded
from one origin can cause interaction with resources from another
origin. See [RFC6454] for an overview of the concept of an "origin".
Application of a SOP in RRDP client/server communication isolates
resources such as Delta and Snapshot files from different Repository
Servers, reducing possible attack vectors. Another way to avoid
undesirable implications (as described in Section 2) would be for a
future version of RRDP to use relative URIs instead of absolute URIs.
This document updates [RFC8182].
1.1. Requirements Language
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.
2. Implications of Cross-Origin Resource Requests in RRDP
The first RRDP specification did not explicitly disallow 'cross-
origin' URI references from the Update Notification file
(Section 3.5.1 of [RFC8182]) towards Delta (Section 3.5.3 of
[RFC8182]) and Snapshot (Section 3.5.2 of [RFC8182]) files, and it
was silent on the topic of HTTP Redirection (Section 15.4 of
[RFC9110]).
The implication of cross-origin references in Update Notification
files is that one Repository Server can reference RRDP resources on
another Repository Server and in doing so inappropriately increase
the resource consumption for both RRDP clients and the referenced
Repository Server. An adversary could also employ cross-origin HTTP
Redirects towards other Repository Servers, causing similar
undesirable behavior.
3. Changes to RFC 8182
To overcome the issue described in Section 2, RRDP Repository Servers
and Clients MUST apply a Same-Origin Policy to both the URIs
referenced in an Update Notification File and any HTTP Redirects.
3.1. New Requirements for RRDP Repository Servers
The following checklist items are added to Section 3.5.1.3 of
[RFC8182]:
NEW
| * The "uri" attribute in the snapshot element and optional delta
| elements MUST be part of the same origin (i.e., represent the
| same principal), meaning referenced URIs MUST have the same
| scheme, host, and port as the URI for the Update Notification
| File specified in the referring RRDP SIA AccessDescription.
|
| * The Repository Server MUST NOT respond with HTTP Redirects
| towards locations with an origin different from the origin of
| the Update Notification File specified in the referring RRDP
| SIA AccessDescription.
3.2. New Requirements for Relying Parties Using RRDP
The following adds to Section 3.4.1 of [RFC8182]:
NEW
| * The Relying Party MUST verify whether the "uri" attributes in
| the Update Notification File are of the same origin as the
| Update Notification File itself. If this verification fails,
| the file MUST be rejected and RRDP cannot be used; see
| Section 3.4.5 for considerations. Implementations SHOULD log a
| message when cross-origin referrals are detected.
|
| * The Relying Party MUST NOT follow HTTP Redirection that results
| from attempts to download Update Notification, Delta, and
| Snapshot files if the target origin is different from the
| origin of the Update Notification File specified in the
| referring RRDP SIA AccessDescription. If this verification
| fails, the RRDP session MUST be rejected and RRDP cannot be
| used; see Section 3.4.5 for considerations. Implementations
| SHOULD log a message when cross-origin redirects are detected.
4. Deployability in the Internet's Current RPKI
Analyzing the [rpkiviews] archives for the period from April to
September 2024, only one RRDP server (reached following the Trust
Anchor Locators (TALs) of the five Regional Internet Registries)
employed a same-origin HTTP redirect. In the period October 2021 -
October 2024 no RRDP Repository Servers were observed that employed
cross-origin URIs in Update Notification Files.
This means that imposing a requirement for the application of a Same-
Origin Policy does not cause any existing commonly used RRDP
Repository Server operations to become non-compliant.
5. Security Considerations
This document addresses an oversight in the original RRDP
specification: Cross-origin requests are detrimental as they allow
one repository operator to increase resource consumption for other
repository operators and RRDP clients.
6. IANA Considerations
This document has no IANA actions.
7. References
7.1. 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>.
[RFC6454] Barth, A., "The Web Origin Concept", RFC 6454,
DOI 10.17487/RFC6454, December 2011,
<https://www.rfc-editor.org/info/rfc6454>.
[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>.
[RFC8182] Bruijnzeels, T., Muravskiy, O., Weber, B., and R. Austein,
"The RPKI Repository Delta Protocol (RRDP)", RFC 8182,
DOI 10.17487/RFC8182, July 2017,
<https://www.rfc-editor.org/info/rfc8182>.
[RFC9110] Fielding, R., Ed., Nottingham, M., Ed., and J. Reschke,
Ed., "HTTP Semantics", STD 97, RFC 9110,
DOI 10.17487/RFC9110, June 2022,
<https://www.rfc-editor.org/info/rfc9110>.
7.2. Informative References
[rpkiviews]
Snijders, J., "rpkiviews", <https://www.rpkiviews.org>.
Acknowledgements
The author wishes to thank Theo Buehler, Claudio Jeker, Alberto
Leiva, Tim Bruijnzeels, Ties de Kock, Martin Hoffmann, and Mikhail
Puzanov for their helpful feedback, comments, and implementation
work. The author wishes to thank Keyur Patel, Meral Shirazipour,
Niclas Comstedt, Dan Harkins, Erik Kline, Roman Danyliw, and Éric
Vyncke for their review.
Author's Address
Job Snijders
Fastly
Amsterdam
Netherlands
Email: job@fastly.com
ISO Plain Language
On this page
§2The Cross-Origin Risk
The original RRDP specification did not explicitly forbid a cross-origin URI in an Update Notification file from pointing to a Delta or Snapshot file. It also did not specify how HTTP redirection should be handled.
One repository could therefore reference resources on another repository, raising resource use for clients and the referenced server. Cross-origin redirects could cause similar effects.
A repository could send clients to fetch files from another repository. That could make both the clients and the other repository do extra work.
§3.1Requirements for Repository Servers
Repository Servers MUST ensure that snapshot and optional delta URI attributes have the same origin as the Update Notification file's URI. Same origin means the same scheme, host, and port.
A Repository Server MUST NOT redirect a client to a location with a different origin from that Update Notification file.
A server must keep its snapshot and delta addresses on the same scheme, host, and port as its notification file. It must not redirect clients to a different origin.
§3.2Requirements for Relying Parties
A relying party MUST check that URI attributes in the Update Notification file have the same origin as the file itself. If not, it MUST reject the file and RRDP cannot be used; implementations SHOULD log the cross-origin referral.
A relying party MUST NOT follow a redirect to a different origin while downloading notification, delta, or snapshot files. If the check fails, the RRDP session MUST be rejected and RRDP cannot be used. Implementations SHOULD log cross-origin redirects.
A relying party checks each address and redirect before using it. If one leads to another origin, it rejects the file or session and should record the reason.
§4Deployment and Security
The RFC reports that its review of rpkiviews archives found one RRDP server using a same-origin HTTP redirect during April to September 2024. It observed no RRDP servers using cross-origin URIs in Update Notification files from October 2021 through October 2024.
The RFC concludes that the policy does not make commonly used RRDP operations non-compliant. It addresses an oversight that could let one repository operator increase resource use for others and their clients.
The RFC's review found no observed cross-origin notification references in the period it examined. The rule addresses the extra resource use those references could cause.