| RFC 9674 | RRDP Same-Origin Policy | December 2024 |
| Snijders | Standards Track | [Page] |
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.¶
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 athttps://www.rfc-editor.org/info/rfc9674.¶
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.¶
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 inSection 2) would be for a future version of RRDP to use relative URIs instead of absolute URIs. This document updates[RFC8182].¶
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.¶
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.¶
To overcome the issue described inSection 2, RRDP Repository Servers and ClientsMUST apply a Same-Origin Policy to both the URIs referenced in an Update Notification File and any HTTP Redirects.¶
The following checklist items are added toSection 3.5.1.3 of [RFC8182]:¶
NEW¶
- The "uri" attribute in the snapshot element and optional delta elementsMUST be part of the same origin (i.e., represent the same principal), meaning referenced URIsMUST have the same scheme, host, and port as the URI for the Update Notification File specified in the referring RRDP SIA AccessDescription.¶
- The Repository ServerMUST 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.¶
The following adds toSection 3.4.1 of [RFC8182]:¶
NEW¶
- The Relying PartyMUST 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 fileMUST be rejected and RRDP cannot be used; see Section3.4.5 for considerations. ImplementationsSHOULD log a message when cross-origin referrals are detected.¶
- The Relying PartyMUST 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 sessionMUST be rejected and RRDP cannot be used; see Section3.4.5 for considerations. ImplementationsSHOULD log a message when cross-origin redirects are detected.¶
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.¶
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.¶
This document has no IANA actions.¶
The author wishes to thankTheo Buehler,Claudio Jeker,Alberto Leiva,Tim Bruijnzeels,Ties de Kock,Martin Hoffmann, andMikhail Puzanov for their helpful feedback, comments, and implementation work. The author wishes to thankKeyur Patel,Meral Shirazipour,Niclas Comstedt,Dan Harkins,Erik Kline,Roman Danyliw, andÉric Vyncke for their review.¶