SIDROPS J. Snijders Internet-Draft Fastly Updates: RFC8182 (if approved) 6 June 2024 Intended status: Standards Track Expires: 8 December 2024 Same-Origin Policy for the RPKI Repository Delta Protocol (RRDP) draft-ietf-sidrops-rrdp-same-origin-00 Abstract This document describes a Same-origin policy (SOP) requirement for RPKI Repository Delta Protocol (RRDP) servers and clients. The same- origin policy concept is a security mechanism to restrict how a document loaded from one origin can cause interaction with resources from another origin. Application of a same-origin policy 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 Internet-Draft is submitted in full conformance with the provisions of BCP 78 and BCP 79. Internet-Drafts are working documents of the Internet Engineering Task Force (IETF). Note that other groups may also distribute working documents as Internet-Drafts. The list of current Internet- Drafts is at https://datatracker.ietf.org/drafts/current/. Internet-Drafts are draft documents valid for a maximum of six months and may be updated, replaced, or obsoleted by other documents at any time. It is inappropriate to use Internet-Drafts as reference material or to cite them other than as "work in progress." This Internet-Draft will expire on 8 December 2024. 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 Snijders Expires 8 December 2024 [Page 1] Internet-Draft RRDP Same-Origin Policy June 2024 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 1.1. Requirements Language . . . . . . . . . . . . . . . . . . 2 2. Implications of cross-origin resource requests in RRDP . . . 3 3. Proposed Solution . . . . . . . . . . . . . . . . . . . . . . 4 3.1. New Requirements for RRDP Repository Servers . . . . . . 4 3.2. New Requirements for Relying Parties using RRDP . . . . . 4 4. Deployability in the Internet's current RPKI . . . . . . . . 4 5. Security Considerations . . . . . . . . . . . . . . . . . . . 5 6. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 5 7. References . . . . . . . . . . . . . . . . . . . . . . . . . 5 7.1. Normative References . . . . . . . . . . . . . . . . . . 5 7.2. Informative References . . . . . . . . . . . . . . . . . 6 Appendix A. Acknowledgements . . . . . . . . . . . . . . . . . . 6 Appendix B. Implementation status . . . . . . . . . . . . . . . 6 Author's Address . . . . . . . . . . . . . . . . . . . . . . . . 7 1. Introduction This document specifies a Same-origin policy (SOP) requirement for RPKI Repository Delta Protocol (RRDP) servers and clients. The same- origin policy 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 same-origin policy in RRDP client/ server communication isolates resources such as Delta and Snapshot files from different Repository Servers, reducing possible attack vectors. 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. Snijders Expires 8 December 2024 [Page 2] Internet-Draft RRDP Same-Origin Policy June 2024 2. Implications of cross-origin resource requests in RRDP The first RRDP protocol 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 was silent on the topic of HTTP Redirection (Section 6.4 of [RFC7231]). 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. Consider the following example served up by *https://badhost.example.net/notification.xml*: Note that in the above Update Notification File the _badhost_ operator is mimicking RIPE NCC's current RRDP session_id and serial and attaching a random query parameter to the snapshot URI. Based on the above Update Notification File, all Relying Parties that reached _badhost_ following SIA AccessDescriptions, would download a large file from the RIPE CDN, wasting bandwidth on both client and server- side. RPs cannot avoid scheduling a new download per Section 3.4.1 of [RFC8182] because Delta file, Snapshot file, session_id and serial are significant only in scope of the referring SIA AccessDescription. In other words, SIAs are globally unique and can be deduplicated before scheduling fetches, but RRDP session_ids are not globally unique, contrary to what Section 3.1 of [RFC8182] suggests. If the adversary increments the serial in tandem with RIPE NCC incrementing their RRDP serial, every next request to _https://badhost/notification.xml_ causes another large file download on the RIPE NCC servers, exacerbating the issue. An adversary could also employ cross-origin HTTP Redirects towards other Repository Servers, causing similar undesirable behavior. To summarize, cross-origin requests in RRDP can enable one Repository Server operator to increase resource consumption on another Repository Server exploiting Relying Party instances. Snijders Expires 8 December 2024 [Page 3] Internet-Draft RRDP Same-Origin Policy June 2024 3. Proposed Solution To overcome the aforementioned 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]: * 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]: * 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 of [RFC8182] for considerations. * The Relying Party MUST NOT follow HTTP Redirection following 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 of [RFC8182] for considerations. 4. Deployability in the Internet's current RPKI In the past 2.5 years no RRDP Repository Servers have employed cross- origin URIs in Update Notification Files. Snijders Expires 8 December 2024 [Page 4] Internet-Draft RRDP Same-Origin Policy June 2024 At the moment of writing only one RRDP server (reached following the TALs of the five Regional Internet Registies) employs a same-origin HTTP redirect. 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 internet-draft patches an oversight in the original RRDP protocol specification: cross-origin requests allow one repository operator to increase resource consumption for another repository operator. Another way to avoid this undesirable implication would've been for the original RRDP specification to have used relative URIs instead of absolute URIs. 6. IANA Considerations No IANA actions required. 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, . [RFC6454] Barth, A., "The Web Origin Concept", RFC 6454, DOI 10.17487/RFC6454, December 2011, . [RFC7231] Fielding, R., Ed. and J. Reschke, Ed., "Hypertext Transfer Protocol (HTTP/1.1): Semantics and Content", RFC 7231, DOI 10.17487/RFC7231, June 2014, . [RFC8174] Leiba, B., "Ambiguity of Uppercase vs Lowercase in RFC 2119 Key Words", BCP 14, RFC 8174, DOI 10.17487/RFC8174, May 2017, . [RFC8182] Bruijnzeels, T., Muravskiy, O., Weber, B., and R. Austein, "The RPKI Repository Delta Protocol (RRDP)", RFC 8182, DOI 10.17487/RFC8182, July 2017, . Snijders Expires 8 December 2024 [Page 5] Internet-Draft RRDP Same-Origin Policy June 2024 7.2. Informative References [FORT-validator] Leiva, A., "FORT validator", . [Routinator] NLNet Labs, "Routinator", . [rpki-client] Jeker, C., Snijders, J., Dzonsons, K., and T. Buehler, "rpki-client", . [rpki-prover] Puzanov, M., "rpki-prover", . Appendix A. 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. Appendix B. Implementation status This section is to be removed before publishing as an RFC. This section records the status of known implementations of the protocol defined by this specification at the time of posting of this Internet-Draft, and is based on a proposal described in RFC 7942. The description of implementations in this section is intended to assist the IETF in its decision processes in progressing drafts to RFCs. Please note that the listing of any individual implementation here does not imply endorsement by the IETF. Furthermore, no effort has been spent to verify the information presented here that was supplied by IETF contributors. This is not intended as, and must not be construed to be, a catalog of available implementations or their features. Readers are advised to note that other implementations may exist. According to RFC 7942, "this will allow reviewers and working groups to assign due consideration to documents that have the benefit of running code, which may serve as evidence of valuable experimentation and feedback that have made the implemented protocols more mature. It is up to the individual working groups to use this information as they see fit". Snijders Expires 8 December 2024 [Page 6] Internet-Draft RRDP Same-Origin Policy June 2024 * OpenBSD's [rpki-client] * Mikhail Puzanov's [rpki-prover] * FORT project's [FORT-validator] * NLNet Labs' [Routinator] Author's Address Job Snijders Fastly Amsterdam Netherlands Email: job@fastly.com Snijders Expires 8 December 2024 [Page 7]