Same-Origin Policy for the RPKI Repository Delta Protocol (RRDP) Fastly
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OPS sidrops same-origin RPKI RRDP 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 .
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Table of Contents
  • .  Introduction
    • .  Requirements Language
  • .  Implications of Cross-Origin Resource Requests in RRDP
  • .  Changes to RFC 8182
    • .  New Requirements for RRDP Repository Servers
    • .  New Requirements for Relying Parties Using RRDP
  • .  Deployability in the Internet's Current RPKI
  • .  Security Considerations
  • .  IANA Considerations
  • .  References
    • .  Normative References
    • .  Informative References
  • Acknowledgements
  • Author's Address
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 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 ) would be for a future version of RRDP to use relative URIs instead of absolute URIs. This document updates .
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 when, and only when, they appear in all capitals, as shown here.
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 () towards Delta () and Snapshot () files, and it was silent on the topic of HTTP Redirection (). 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.
Changes to RFC 8182 To overcome the issue described in , 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.
New Requirements for RRDP Repository Servers The following checklist items are added to : 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.
New Requirements for Relying Parties Using RRDP The following adds to : 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 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 for considerations. Implementations SHOULD log a message when cross-origin redirects are detected.
Deployability in the Internet's Current RPKI Analyzing the 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.
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.
IANA Considerations This document has no IANA actions.
References Normative References Key words for use in RFCs to Indicate Requirement Levels In many standards track documents several words are used to signify the requirements in the specification. These words are often capitalized. This document defines these words as they should be interpreted in IETF documents. This document specifies an Internet Best Current Practices for the Internet Community, and requests discussion and suggestions for improvements. The Web Origin Concept This document defines the concept of an "origin", which is often used as the scope of authority or privilege by user agents. Typically, user agents isolate content retrieved from different origins to prevent malicious web site operators from interfering with the operation of benign web sites. In addition to outlining the principles that underlie the concept of origin, this document details how to determine the origin of a URI and how to serialize an origin into a string. It also defines an HTTP header field, named "Origin", that indicates which origins are associated with an HTTP request. [STANDARDS-TRACK] Ambiguity of Uppercase vs Lowercase in RFC 2119 Key Words RFC 2119 specifies common key words that may be used in protocol specifications. This document aims to reduce the ambiguity by clarifying that only UPPERCASE usage of the key words have the defined special meanings. The RPKI Repository Delta Protocol (RRDP) In the Resource Public Key Infrastructure (RPKI), Certificate Authorities (CAs) publish certificates, including end-entity certificates, Certificate Revocation Lists (CRLs), and RPKI signed objects to repositories. Relying Parties retrieve the published information from those repositories. This document specifies a new RPKI Repository Delta Protocol (RRDP) for this purpose. RRDP was specifically designed for scaling. It relies on an Update Notification File which lists the current Snapshot and Delta Files that can be retrieved using HTTPS (HTTP over Transport Layer Security (TLS)), and it enables the use of Content Distribution Networks (CDNs) or other caching infrastructures for the retrieval of these files. HTTP Semantics The Hypertext Transfer Protocol (HTTP) is a stateless application-level protocol for distributed, collaborative, hypertext information systems. This document describes the overall architecture of HTTP, establishes common terminology, and defines aspects of the protocol that are shared by all versions. In this definition are core protocol elements, extensibility mechanisms, and the "http" and "https" Uniform Resource Identifier (URI) schemes. This document updates RFC 3864 and obsoletes RFCs 2818, 7231, 7232, 7233, 7235, 7538, 7615, 7694, and portions of 7230. Informative References rpkiviews
Acknowledgements The author wishes to thank , , , , , , and for their helpful feedback, comments, and implementation work. The author wishes to thank , , , , , , and for their review.
Author's Address Fastly
Amsterdam Netherlands job@fastly.com