Internet Engineering Task Force (IETF)                           R. Bush
Request for Comments: 9255                         Arrcus & IIJ Research
Category: Standards Track                                     R. Housley
ISSN: 2070-1721                                           Vigil Security
                                                               June 2022


              The 'I' in RPKI Does Not Stand for Identity

Abstract

   There is a false notion that Internet Number Resources (INRs) in the
   RPKI can be associated with the real-world identity of the 'holder'
   of an INR.  This document specifies that RPKI does not associate to
   the INR holder.

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/rfc9255.

Copyright Notice

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   document authors.  All rights reserved.

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Table of Contents

   1.  Introduction
     1.1.  Requirements Language
   2.  The RPKI is for Authorization
   3.  Discussion
   4.  Security Considerations
   5.  IANA Considerations
   6.  References
     6.1.  Normative References
     6.2.  Informative References
   Acknowledgments
   Authors' Addresses

1.  Introduction

   The Resource Public Key Infrastructure (RPKI), see [RFC6480],
   "represents the allocation hierarchy of IP address space and
   Autonomous System (AS) numbers," which are collectively known as
   Internet Number Resources (INRs).  Since initial deployment, the RPKI
   has grown to include other similar resource and routing data, e.g.,
   Router Keying for BGPsec [RFC8635].

   In security terms, the phrase "Public Key" implies there is also a
   corresponding private key [RFC5280].  The RPKI provides strong
   authority to the current holder of INRs; however, some people have a
   desire to use RPKI private keys to sign arbitrary documents as the
   INR 'holder' of those resources with the inappropriate expectation
   that the signature will be considered an attestation to the
   authenticity of the document content.  But, in reality, the RPKI
   certificate is only an authorization to speak for the explicitly
   identified INRs; it is explicitly not intended for authentication of
   the 'holders' of the INRs.  This situation is emphasized in
   Section 2.1 of [RFC6480].

   It has been suggested that one could authenticate real-world business
   transactions with the signatures of INR holders.  For example, Bill's
   Bait and Sushi (BB&S) could use the private key attesting to that
   they are the holder of their AS in the RPKI to sign a Letter of
   Authorization (LOA) for some other party to rack and stack hardware
   owned by BB&S.  Unfortunately, while this may be technically
   possible, it is neither appropriate nor meaningful.

   The 'I' in RPKI actually stands for "Infrastructure," as in Resource
   Public Key Infrastructure, not for "Identity".  In fact, the RPKI
   does not provide any association between INRs and the real-world
   holder(s) of those INRs.  The RPKI provides authorization to make
   assertions only regarding Internet Number Resources, such as IP
   prefixes or AS numbers, and data such as Autonomous System Provider
   Authorization (ASPA) records [ASPA-PROFILE].

   In short, avoid the desire to use RPKI certificates for any purpose
   other than the verification of authorizations associated with the
   delegation of INRs or attestations related to INRs.  Instead,
   recognize that these authorizations and attestations take place
   irrespective of the identity of an RPKI private key holder.

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.  The RPKI is for Authorization

   The RPKI was designed and specified to sign certificates for use
   within the RPKI itself and to generate Route Origin Authorizations
   (ROAs) [RFC6480] for use in routing.  Its design intentionally
   precluded use for attesting to real-world identity as, among other
   issues, it would expose the Certification Authority (CA) to
   liability.

   That the RPKI does not authenticate real-world identity is by design.
   If it tried to do so, aside from the liability, it would end in a
   world of complexity with no proof of termination.

   Registries such as the Regional Internet Registries (RIRs) provide
   INR to real-world identity mapping through WHOIS [RFC3912] and
   similar services.  They claim to be authoritative, at least for the
   INRs that they allocate.

   That is, RPKI-based credentials of INRs MUST NOT be used to
   authenticate real-world documents or transactions.  That might be
   done with some formal external authentication of authority allowing
   an otherwise anonymous INR holder to authenticate the particular
   document or transaction.  Given such external, i.e. non-RPKI,
   verification of authority, the use of RPKI-based credentials adds no
   authenticity.

3.  Discussion

   Section 2.1 of the RPKI base document [RFC6480] says explicitly "An
   important property of this PKI is that certificates do not attest to
   the identity of the subject."

   Section 3.1 of "Template for a Certification Practice Statement (CPS)
   for the Resource PKI (RPKI)" [RFC7382] states that the Subject name
   in each certificate SHOULD NOT be meaningful and goes on to explain
   this at some length.

   Normally, the INR holder does not hold the private key attesting to
   their resources; the CA does.  The INR holder has a real-world
   business relationship with the CA for which they have likely signed
   real-world documents.

   As the INR holder does not have the keying material, they rely on the
   CA, to which they presumably present credentials, to manipulate their
   INRs.  These credentials may be user ID and password (with two-factor
   authentication one hopes), a hardware token, client browser
   certificates, etc.

   Hence schemes such as Resource Tagged Attestations [RPKI-RTA] and
   Signed Checklists [RPKI-RSC] must go to great lengths to extract the
   supposedly relevant keys from the CA.

   For some particular INR, say, Bill's Bait and Sushi's Autonomous
   System (AS) number, someone out on the net probably has the
   credentials to the CA account in which BB&S's INRs are registered.
   That could be the owner of BB&S, Randy's Taco Stand, an IT vendor, or
   the Government of Elbonia.  One simply can not know.

   In large organizations, INR management is often compartmentalized
   with no authority over anything beyond dealing with INR registration.
   The INR manager for Bill's Bait and Sushi is unlikely to be
   authorized to conduct bank transactions for BB&S, or even to
   authorize access to BB&S's servers in some colocation facility.

   Then there is the temporal issue.  The holder of that AS may be BB&S
   today when some document was signed, and could be the Government of
   Elbonia tomorrow.  Or the resource could have been administratively
   moved from one CA to another, likely requiring a change of keys.  If
   so, how does one determine if the signature on the real-world
   document is still valid?

   While Ghostbuster Records [RFC6493] may seem to identify real-world
   entities, their semantic content is completely arbitrary and does not
   attest to holding of any INRs.  They are merely clues for operational
   support contact in case of technical RPKI problems.

   Usually, before registering INRs, CAs require proof of an INR holding
   via external documentation and authorities.  It is somewhat droll
   that the CPS Template [RFC7382] does not mention any diligence the CA
   must, or even might, conduct to assure the INRs are in fact owned by
   a registrant.

   That someone can provide 'proof of possession' of the private key
   signing over a particular INR should not be taken to imply that they
   are a valid legal representative of the organization in possession of
   that INR.  They could be in an INR administrative role, and not be a
   formal representative of the organization.

   Autonomous System Numbers do not identify real-world entities.  They
   are identifiers some network operators 'own' and are only used for
   loop detection in routing.  They have no inherent semantics other
   than uniqueness.

4.  Security Considerations

   Attempts to use RPKI data to authenticate real-world documents or
   other artifacts requiring identity, while possibly cryptographically
   valid within the RPKI, are misleading as to any authenticity.

   When a document is signed with the private key associated with an
   RPKI certificate, the signer is speaking for the INRs (the IP address
   space and AS numbers) in the certificate.  This is not an identity;
   this is an authorization.  In schemes such as Resource Tagged
   Attestations [RPKI-RTA] and Signed Checklists [RPKI-RSC], the signed
   message further narrows this scope of INRs.  The INRs in the message
   are a subset of the INRs in the certificate.  If the signature is
   valid, the message content comes from a party that is authorized to
   speak for that subset of INRs.

   Control of INRs for an entity could be used to falsely authorize
   transactions or documents for which the INR manager has no authority.

5.  IANA Considerations

   This document has no IANA actions.

6.  References

6.1.  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>.

   [RFC5280]  Cooper, D., Santesson, S., Farrell, S., Boeyen, S.,
              Housley, R., and W. Polk, "Internet X.509 Public Key
              Infrastructure Certificate and Certificate Revocation List
              (CRL) Profile", RFC 5280, DOI 10.17487/RFC5280, May 2008,
              <https://www.rfc-editor.org/info/rfc5280>.

   [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>.

   [RFC7382]  Kent, S., Kong, D., and K. Seo, "Template for a
              Certification Practice Statement (CPS) for the Resource
              PKI (RPKI)", BCP 173, RFC 7382, DOI 10.17487/RFC7382,
              April 2015, <https://www.rfc-editor.org/info/rfc7382>.

   [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>.

   [RFC8635]  Bush, R., Turner, S., and K. Patel, "Router Keying for
              BGPsec", RFC 8635, DOI 10.17487/RFC8635, August 2019,
              <https://www.rfc-editor.org/info/rfc8635>.

6.2.  Informative References

   [ASPA-PROFILE]
              Azimov, A., Uskov, E., Bush, R., Patel, K., Snijders, J.,
              and R. Housley, "A Profile for Autonomous System Provider
              Authorization", Work in Progress, Internet-Draft, draft-
              ietf-sidrops-aspa-profile-07, 31 January 2022,
              <https://datatracker.ietf.org/doc/html/draft-ietf-sidrops-
              aspa-profile-07>.

   [RFC3912]  Daigle, L., "WHOIS Protocol Specification", RFC 3912,
              DOI 10.17487/RFC3912, September 2004,
              <https://www.rfc-editor.org/info/rfc3912>.

   [RFC6493]  Bush, R., "The Resource Public Key Infrastructure (RPKI)
              Ghostbusters Record", RFC 6493, DOI 10.17487/RFC6493,
              February 2012, <https://www.rfc-editor.org/info/rfc6493>.

   [RPKI-RSC] Snijders, J., Harrison, T., and B. Maddison, "A profile
              for Resource Public Key Infrastructure (RPKI) Signed
              Checklists (RSC)", Work in Progress, Internet-Draft,
              draft-ietf-sidrops-rpki-rsc-08, 26 May 2022,
              <https://datatracker.ietf.org/doc/html/draft-ietf-sidrops-
              rpki-rsc-08>.

   [RPKI-RTA] Michaelson, G., Huston, G., Harrison, T., Bruijnzeels, T.,
              and M. Hoffmann, "A profile for Resource Tagged
              Attestations (RTAs)", Work in Progress, Internet-Draft,
              draft-ietf-sidrops-rpki-rta-00, 21 January 2021,
              <https://datatracker.ietf.org/doc/html/draft-ietf-sidrops-
              rpki-rta-00>.

Acknowledgments

   The authors thank George Michaelson and Job Snijders for lively
   discussion, Geoff Huston for some more formal text, Ties de Kock for
   useful suggestions, many directorate and IESG reviewers, and last but
   not least, Biff for the loan of Bill's Bait and Sushi.

Authors' Addresses

   Randy Bush
   Arrcus & Internet Initiative Japan Research
   5147 Crystal Springs
   Bainbridge Island, WA 98110
   United States of America
   Email: randy@psg.com


   Russ Housley
   Vigil Security, LLC
   516 Dranesville Road
   Herndon, VA 20170
   United States of America
   Email: housley@vigilsec.com