Resource Public Key Infrastructure (RPKI) object profile for Signed Checklist (RSC)

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Table of Contents

1. Introduction

This document defines a Cryptographic Message Syntax (CMS) [RFC5652] profile for a general purpose listing of checksums (a 'checklist'), for use with the Resource Public Key Infrastructure (RPKI) [RFC6480]. The objective is to allow an attestation, in the form of a listing of one or more checksums of arbitrary files, to be signed "with resources", and for validation to provide a means to confirm a given Internet Resource Holder produced the RPKI Signed Checklist (RSC). The profile is intended to provide for the signing of a checksum listing with a specific set of Internet Number Resources.¶

Signed Checklists are expected to facilitate inter-domain business use-cases which depend on an ability to verify resource holdership. RPKI-based validation processes are expected to become the industry norm for automated Bring Your Own IP (BYOIP) on-boarding or establishment of physical interconnection between Autonomous Systems.¶

The RSC concept borrows heavily from RTA [I-D.ietf-sidrops-rpki-rta], Manifests [RFC6486], and OpenBSD's [signify] utility. The main difference between RSC and RTA is that the RTA profile allows multiple signers to attest a single digital object through a checksum of its content, while the RSC profile allows a single signer to attest the existence of multiple digital objects. A single signer profile is considered a simplification for both implementers and operators.¶

2. RSC Profile and Distribution

RSC follows the Signed Object Template for the RPKI [RFC6488] with one exception. Because RSCs MUST NOT be distributed through the global RPKI Repository system, the Subject Information Access (SIA) extension MUST be omitted from the RSC's X.509 End-Entity (EE) certificate.¶

What constitutes suitable transport for RSC files is deliberately unspecified. It might be a USB stick, a web interface secured with conventional HTTPS, PGP-signed email, a T-shirt printed with a QR code, or a carrier pigeon.¶

3. The RSC ContentType

The ContentType for an RSC is defined as rpkiSignedChecklist, and has the numerical value of 1.2.840.113549.1.9.16.1.48.¶

This OID MUST appear both within the eContentType in the encapContentInfo object as well as the ContentType signed attribute in the signerInfo object (see [RFC6488]).¶

4. The RSC eContent

The content of an RSC indicates that a checklist for arbitrary digital objects has been signed "with resources". An RSC is formally defined as:¶

RpkiSignedChecklist-2021
  { iso(1) member-body(2) us(840) rsadsi(113549)
    pkcs(1) pkcs9(9) smime(16) mod(0) TBD }

DEFINITIONS EXPLICIT TAGS ::=
BEGIN

IMPORTS
  CONTENT-TYPE, Digest, DigestAlgorithmIdentifier
  FROM CryptographicMessageSyntax-2010 -- in [RFC6268]
    { iso(1) member-body(2) us(840) rsadsi(113549) pkcs(1)
      pkcs-9(9) smime(16) modules(0) id-mod-cms-2009(58) }

  ASIdOrRange, IPAddressOrRange
  FROM IPAddrAndASCertExtn -- in [RFC3779]
    { iso(1) identified-organization(3) dod(6) internet(1)
      security(5) mechanisms(5) pkix(7) mod(0)
      id-mod-ip-addr-and-as-ident(30) } ;

ct-rpkiSignedChecklist CONTENT-TYPE ::=
    { TYPE RpkiSignedChecklist IDENTIFIED BY
      id-ct-signedChecklist }

id-ct-signedChecklist OBJECT IDENTIFIER ::=
    { iso(1) member-body(2) us(840) rsadsi(113549) pkcs(1)
      pkcs-9(9) id-smime(16) id-ct(1) 48 }

RpkiSignedChecklist ::= SEQUENCE {
  version  [0]          INTEGER DEFAULT 0,
  resources             ResourceBlock,
  digestAlgorithm       DigestAlgorithmIdentifier,
  checkList             SEQUENCE SIZE (1..MAX) OF FileNameAndHash }

FileNameAndHash ::= SEQUENCE {
  fileName        IA5String OPTIONAL,
  hash            Digest }

ResourceBlock ::= SEQUENCE {
    asID         [0]       AsList OPTIONAL,
    ipAddrBlocks [1]       IPList OPTIONAL }
    -- at least one of asID or ipAddrBlocks MUST be present
    ( WITH COMPONENTS { ..., asID PRESENT} |
      WITH COMPONENTS { ..., ipAddrBlocks PRESENT } )

AsList ::= SEQUENCE (SIZE(1..MAX)) OF ASIdOrRange

IPList ::= SEQUENCE (SIZE(1..MAX)) OF IPAddressFamilyItem

IPAddressFamilyItem ::= SEQUENCE {    -- AFI & optional SAFI --
   addressFamily        OCTET STRING (SIZE (2..3)),
   iPAddressOrRange     IPAddressOrRange }

END

7. Security Considerations

Relying parties are hereby warned that the data in a RPKI Signed Checklist is self-asserted. When determining the meaning of any data contained in an RPKI Signed Checklist, Relying Parties MUST NOT make any assumptions about the signer beyond the fact that it had sufficient control of the issuing CA to create the object. These data have not been verified by the Certificate Authority (CA) that issued the CA certificate to the entity that issued the EE Certificate used to validate the Signed Checklist.¶

RPKI Certificates are not bound to real world identities, see [I-D.ymbk-sidrops-rpki-has-no-identity] for an elaboration. Relying Parties can only associate real world entities to Internet Number Resources by additionally consulting an exogenous authority. Signed Checklists are a tool to communicate assertions 'signed with Internet Number Resources', not about any other aspect of the resource holder's business operations such as the identity of the resource holder itself.¶

RSC objects are not distributed through the RPKI Repository system. From this, it follows that third parties who do not have a copy of a given RSC, may not be aware of the existence of that RSC. Since RSC objects use EE Certificates, but all other currently defined types of RPKI object profiles are published in public CA repositories, an observer may infer from discrepancies in the Repository that RSC object(s) may exist. For example, if a CA does not use random serial numbers for Certificates, an observer could detect gaps between the serial numbers of the published EE Certificates. Similarly, if the CA includes a serial number on a CRL that does not match any published object, an observer could postulate an RSC EE Certificate was revoked.¶

Conversely, a gap in serial numbers does not imply that an RSC exists. Nor does an arbitrary (to the RP unknown) serial in a CRL imply an RSC object exists: the implicitly referenced object might not be a RSC, it might never have been published, or was revoked before it was visible to RPs. In general, it is not possible to confidently infer the existence or non-existence of RSCs from the Repository state without access to a given RSC.¶

While an one-time-use EE Certificate must only be used to generate and sign a single RSC object, CAs technically are not restricted from generating and signing multiple different RSC objects with a single keypair. Any RSC objects sharing the same EE Certificate can not be revoked individually.¶

9. IANA Considerations

Decimal   Description             References
---------------------------------------------------------------
  48      id-ct-signedChecklist   [draft-ietf-sidrops-rpki-rsc]

Name              OID                         Specification
-------------------------------------------------------------
Signed Checklist  1.2.840.113549.1.9.16.1.48  [draft-ietf-sidrops-rpki-rsc]

Filename Extension  RPKI Object       Reference
-------------------------------------------------------------------
       .sig         Signed Checklist  [draft-ietf-sidrops-rpki-rsc]

Decimal  Description                      References
-----------------------------------------------------------------------
    TBD  id-mod-rpkiSignedChecklist-2021  [draft-ietf-sidrops-rpki-rsc]

   Type name: application
   Subtype name: rpki-checklist
   Required parameters: None
   Optional parameters: None
   Encoding considerations: binary
   Security considerations: Carries an RPKI Signed Checklist
                            [RFC-TBD].
   Interoperability considerations: None
   Published specification: This document.
   Applications that use this media type: RPKI operators.
   Additional information:
     Content: This media type is a signed object, as defined
         in [RFC6488], which contains a payload of a list of
         checksums as defined above in this document.
     Magic number(s): None
     File extension(s): .sig
     Macintosh file type code(s):
   Person & email address to contact for further information:
     Job Snijders <job@fastly.com>
   Intended usage: COMMON
   Restrictions on usage: None
   Author: Job Snijders <job@fastly.com>
   Change controller: Job Snijders <job@fastly.com>

Appendix A. Acknowledgements

The authors wish to thank George Michaelson, Tom Harrison, Geoff Huston, Randy Bush, Stephen Kent, Matt Lepinski, Rob Austein, Ted Unangst, and Marc Espie for prior art. The authors thank Russ Housley for reviewing the ASN.1 notation and providing suggestions. The authors would like to thank Nimrod Levy, Tim Bruijnzeels, Alberto Leiva, Ties de Kock, and Peter Peele for document review and suggestions.¶

Authors' Addresses