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Resource Public Key Infrastructure (RPKI) Trust Anchor Locator

The information below is for an old version of the document that is already published as an RFC.
Document Type
This is an older version of an Internet-Draft that was ultimately published as RFC 6490.
Authors Samuel Weiler , Stephen Kent , Geoff Huston , George G. Michaelson
Last updated 2015-10-14 (Latest revision 2011-04-13)
RFC stream Internet Engineering Task Force (IETF)
Intended RFC status Proposed Standard
Additional resources Mailing list discussion
Stream WG state WG Document
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IESG IESG state Became RFC 6490 (Proposed Standard)
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Responsible AD Stewart Bryant
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SIDR                                                           G. Huston
Internet-Draft                                                     APNIC
Intended status: Standards Track                               S. Weiler
Expires: October 15, 2011                                   SPARTA, Inc.
                                                           G. Michaelson
                                                                 S. Kent
                                                          April 13, 2011

          Resource Certificate PKI (RPKI) Trust Anchor Locator


   This document defines a Trust Anchor Locator (TAL) for the Resource
   Certificate Public Key Infrastructure (RPKI).

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

   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 October 15, 2011.

Copyright Notice

   Copyright (c) 2011 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
   ( 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 Simplified BSD License text as described in Section 4.e of

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   the Trust Legal Provisions and are provided without warranty as
   described in the Simplified BSD License.

Table of Contents

   1.  Introduction  . . . . . . . . . . . . . . . . . . . . . . . . . 3
     1.1.  Terminology . . . . . . . . . . . . . . . . . . . . . . . . 3
   2.  Trust Anchor Locator  . . . . . . . . . . . . . . . . . . . . . 3
     2.1.  Trust Anchor Locator Format . . . . . . . . . . . . . . . . 3
     2.2.  TAL and Trust Anchor Certificate Considerations . . . . . . 4
     2.3.  Example . . . . . . . . . . . . . . . . . . . . . . . . . . 5
   3.  Relying Party Use . . . . . . . . . . . . . . . . . . . . . . . 5
   4.  Security Considerations . . . . . . . . . . . . . . . . . . . . 6
   5.  IANA Considerations . . . . . . . . . . . . . . . . . . . . . . 6
   6.  Acknowledgments . . . . . . . . . . . . . . . . . . . . . . . . 6
   7.  References  . . . . . . . . . . . . . . . . . . . . . . . . . . 7
     7.1.  Normative References  . . . . . . . . . . . . . . . . . . . 7
     7.2.  Informative References  . . . . . . . . . . . . . . . . . . 7
   Authors' Addresses  . . . . . . . . . . . . . . . . . . . . . . . . 8

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1.  Introduction

   This document defines a Trust Anchor Locator (TAL) for the Resource
   Certificate Public Key Infrastructure (RPKI) [ID.sidr-arch].  This
   format may be used to distribute trust anchor material using a mix of
   out-of-band and online means.  Procedures used by relying parties
   (RPs) to verify RPKI signed objects SHOULD support this format to
   facilitate interoperability between creators of Trust Anchor (TA)
   material and RPs.

1.1.  Terminology

   The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT",
   document are to be interpreted as described in RFC 2119.

2.  Trust Anchor Locator

2.1.  Trust Anchor Locator Format

   This document does not propose a new format for TA material.  A TA in
   the RPKI is represented by a self-signed X.509 CA certificate, a
   format commonly used in PKIs and widely supported by RP software.
   This document specifies a format for data used to retrieve and verify
   the authenticity of a TA, in a very simple fashion.  That data is
   referred to as "Trust Anchor Locator" (TAL).

   The motivation for defining the TAL is to enable selected data in the
   trust anchor to change, without needing to effect re-distribution of
   the trust anchor per se.  In the RPKI, certificates contain
   extensions that represent Internet Number Resources (INRs) [RFC3779].
   The set of INRs associated with an entity likely will change over
   time.  Thus, if one were to use the common PKI convention of
   distributing a TA to RPs in a secure fashion, this procedure would
   need to be repeated whenever the INR set for the TA changed.  By
   distributing the TAL (in a secure fashion), instead of the TA, this
   problem is avoided, i.e., the TAL is constant so long as the TA's
   public key and its location does not change.

   The TAL is analogous to the TrustAnchorInfo data structure adopted as
   a PKIX standard [RFC5914].  That standard could be used to represent
   the TAL, if one defined an rsync URI extension for that data
   structure.  However, the TAL format was adopted by RPKI implementors
   prior to the PKIX TA work, and the RPKI implementer community has
   elected to utilize the TAL format, rather than define the requisite
   extension.  The community also prefers the simplicity of the ASCII
   encoding of the TAL, vs. the binary (ASN.1) encoding for

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   The TAL is an ordered sequence of a rsync URI [RFC5781], and a base
   64-encoding with URL and filename safe alphabet [RFC4648], DER-
   encoded X.509 [X.509] subjectPublicKeyInfo [RFC5280].  The sequence
   separator is an ASCII line break sequence, namely the CR LF character
   pair.  The CR character is OPTIONAL.

2.2.  TAL and Trust Anchor Certificate Considerations

   The rsync URI in the TAL MUST reference a single object.  It MUST NOT
   reference a directory or any other form of collection of objects.

   The referenced object MUST be a self-signed CA certificate that
   conforms to the RPKI certificate profile [ID.sidr-res-certs].  This
   certificate is the trust anchor in certification path discovery
   [RFC4158] and validation [RFC5280][RFC3779].

   The validity interval of this trust anchor SHOULD reflect the
   anticipated period of stability the particular set of Internet Number
   Resources (INRs) that are associated with the putative TA.

   The INR [RFC3779] extension(s) of this trust anchor MUST contain a
   non-empty set of number resources.  It MUST NOT use the "inherit"
   form of the INR extension(s).  The INR set described in this
   certificate is the set of number resources for which the issuing
   entity is offering itself as a putative trust anchor in the RPKI

   The public key used to verify the trust anchor MUST be the same as
   the subjectPublicKeyInfo in the CA certificate and in the TAL.

   The trust anchor MUST contain a stable key.  This key MUST NOT change
   when the certificate is reissued due to changes in the INR
   extension(s), when the certificate is renewed prior to expiration or
   for any reason other than a key change.

   Because the public key in the TAL and the trust anchor MUST be
   stable, this motivates operation of that CA in an off-line mode.
   Thus the entity that issues the trust anchor SHOULD issue a
   subordinate CA certificate that contains the same INRs (via the use
   of the "inherit" option in the INR extensions of the subordinate
   certificate).  This allows the entity that issues the trust anchor to
   keep the corresponding private key of this certificate off-line,
   while issuing all relevant child certificates under the immediate
   subordinate CA.  This measure also allows the CRL issued by that
   entity to be used to revoke the subordinate (CA) certificate in the
   event of suspected key compromise of this potentially more vulnerable

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   online operational key pair.

   The trust anchor MUST be published at a stable URI.  When the trust
   anchor is re-issued for any reason, the replacement CA certificate
   MUST be accessible using the same URI.

   Becuase the trust anchor is a self-signed certificate, there is no
   corresponding Certificate Revocation List that can be used to revoke
   it, nor is there a manifest [ID.sidr-rpki-manifests] that lists this

   If an entity wishes to withdraw a self-signed CA certificate as a
   putative Trust Anchor, for any reason, including key rollover, the
   entity MUST remove the object from the location referenced in the

2.3.  Example


3.  Relying Party Use

   In order to use the TAL to retrieve and validate a (putative) TA, an

   1.  Retrieve the object referenced by the URI contained in the TAL.

   2.  Confirm that the retrieved object is a current, self-signed RPKI
       CA certificate that conforms to the profile as specified in

   3.  Confirm that the public key in the TAL matches the public key in
       the retrieved object.

   4.  Perform other checks, as deemed appropriate (locally), to ensure
       that the RP is willing to accept the entity publishing this self-
       signed CA certificate to be a trust anchor, relating to the
       validity of attestations made in the context of the RPKI
       (relating to all resources described in the INR extension of this

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   An RP SHOULD perform these functions for each instance of TAL that it
   is holding for this purpose every time the RP performs a re-
   synchronization across the local repository cache.  In any case, an
   RP also SHOULD perform these functions prior to the expiration of the
   locally cached copy of the retrieved trust anchor referenced by the

4.  Security Considerations

   Compromise of a trust anchor private key permits unauthorized parties
   to masquerade as a trust anchor, with potentially severe
   consequences.  Reliance on an inappropriate or incorrect trust anchor
   has similar potentially severe consequences.

   This trust anchor locator does not directly provide a list of
   resources covered by the referenced self-signed CA certificate.
   Instead, the RP is referred to the TA itself and the INR extension(s)
   within this certificate.  This provides necessary operational
   flexibility, but it also allows the certificate issuer to claim to be
   authoritative for any resource.  Relying parties should either have
   great confidence in the issuers of such certificates that they are
   configuring as trust anchors, or they should issue their own self-
   signed certificate as a trust anchor and, in doing so, impose
   constraints on the subordinate certificates.  For more information on
   this approach, see [ID.reynolds-rpki-ltamgmt].

5.  IANA Considerations

   [This document specifies no IANA actions.]

6.  Acknowledgments

   This approach to TA material was originally described by Robert

   The authors acknowledge the contributions of Rob Austein and Randy
   Bush, who assisted with earlier versions of this document and with
   helpful review comments.

7.  References

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7.1.  Normative References

              Huston, G., Michaelson, G., and R. Loomans, "A Profile for
              X.509 PKIX Resource Certificates", Work in progress:
              Internet Drafts draft-ietf-sidr-res-certs-17.txt,
              September 2009.

   [RFC3779]  Lynn, C., Kent, S., and K. Seo, "X.509 Extensions for IP
              Addresses and AS Identifiers", RFC 3779, June 2004.

   [RFC4648]  Josefsson, S., "The Base16, Base32, and Base64 Data
              Encodings", RFC 4648, October 2006.

   [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, May 2008.

   [RFC5781]  Weiler, S., Ward, D., and R. Housley, "The rsync URI
              Scheme", RFC 5781, February 2010.

   [X.509]    ITU-T, "Recommendation X.509: The Directory -
              Authentication Framework", 2000.

7.2.  Informative References

              Reynolds, M. and S. Kent, "Local Trust Anchor Management
              for the Resource Public Key Infrastructure", Work in
              progress: Internet
              Drafts draft-reynolds-rpki-ltamgmt-01.txt, September 2010.

              Lepinski, M. and S. Kent, "An Infrastructure to Support
              Secure Internet Routing", Work in progress: Internet
              Drafts draft-ietf-sidr-arch-11.txt, September 2010.

              Austein, R., Huston, G., Kent, S., and M. Lepinski,
              "Manifests for the Resource Public Key Infrastructure",
              draft-ietf-sidr-rpki-manifests (work in progress),
              May 2010.

   [RFC4158]  Cooper, M., Dzambasow, Y., Hesse, P., Joseph, S., and R.
              Nicholas, "Internet X.509 Public Key Infrastructure:
              Certification Path Building", RFC 4158, September 2005.

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   [RFC5914]  Housley, R., Ashmore, S., and C. Wallace, "Trust Anchor
              Format", RFC 5914, June 2010.

Authors' Addresses

   Geoff Huston


   Samuel Weiler
   SPARTA, Inc.
   7110 Samuel Morse Drive
   Colombia, Maryland  21046


   George Michaelson
   Asia Pacific Network Information Centre


   Stephen Kent
   BBN Technologies
   10 Moulton St.
   Cambridge, MA  02138


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