Skip to main content

Resource Certificate PKI (RPKI) Trust Anchor Locator

The information below is for an old version of the document.
Document Type
This is an older version of an Internet-Draft that was ultimately published as RFC 7730.
Authors Geoff Huston , Samuel Weiler , George G. Michaelson , Stephen Kent
Last updated 2014-03-18
RFC stream Internet Engineering Task Force (IETF)
Additional resources Mailing list discussion
Stream WG state WG Document
Document shepherd (None)
IESG IESG state I-D Exists
Consensus boilerplate Unknown
Telechat date (None)
Responsible AD (None)
Send notices to (None)
SIDR                                                           G. Huston
Internet-Draft                                                     APNIC
Obsoletes: 6490 (if approved)                                  S. Weiler
Intended status: Standards Track                            SPARTA, Inc.
Expires: September 5, 2014                                 G. Michaelson
                                                                 S. Kent
                                                           March 4, 2014

          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 September 5, 2014.

Copyright Notice

   Copyright (c) 2014 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

Huston, et al.          Expires September 5, 2014               [Page 1]
Internet-Draft          RPKI Trust Anchor Locator             March 2014

   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 . . . . . . . . . . . . . . . . . . . . . . . 6
   4.  Security Considerations . . . . . . . . . . . . . . . . . . . . 6
   5.  IANA Considerations . . . . . . . . . . . . . . . . . . . . . . 7
   6.  Acknowledgments . . . . . . . . . . . . . . . . . . . . . . . . 7
   7.  References  . . . . . . . . . . . . . . . . . . . . . . . . . . 7
     7.1.  Normative References  . . . . . . . . . . . . . . . . . . . 7
     7.2.  Informative References  . . . . . . . . . . . . . . . . . . 8
   Authors' Addresses  . . . . . . . . . . . . . . . . . . . . . . . . 8

Huston, et al.          Expires September 5, 2014               [Page 2]
Internet-Draft          RPKI Trust Anchor Locator             March 2014

1.  Introduction

   This document defines a Trust Anchor Locator (TAL) for the Resource
   Certificate Public Key Infrastructure (RPKI) [RFC6480].  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 material
   and RPs.

1.1.  Terminology

   The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT",
   document are to be interpreted as described in [RFC2119].

2.  Trust Anchor Locator

2.1.  Trust Anchor Locator Format

   This document does not propose a new format for trust anchor
   material.  A trust anchor in the RPKI is represented by a self-signed
   X.509 Certificate Authority (CA), 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 trust
   anchor in a very simple fashion.  That data is referred to as the

   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 acting as a trust anchor is
   likely to change over time.  Thus, if one were to use the common PKI
   convention of distributing a trust anchor to RPs in a secure fashion,
   this procedure would need to be repeated whenever the INR set for the
   entity acting as a trust anchor changed.  By distributing the TAL (in
   a secure fashion), instead of the trust anchor, 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 [RFC5914]
   adopted as a PKIX standard.  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 trust anchor work, and the RPKI implementer
   community has elected to utilize the TAL format, rather than define

Huston, et al.          Expires September 5, 2014               [Page 3]
Internet-Draft          RPKI Trust Anchor Locator             March 2014

   the requisite extension.  The community also prefers the simplicity
   of the ASCII encoding of the TAL, vs. the binary (ASN.1) encoding for

   The TAL is an ordered sequence of:

      1)  a URI section,

      2)  a <CRLF> or <LF> line break,

      3)  a subjectPublicKeyInfo [RFC5280] in DER format [X.509],
          encoded in Base64 (see Section 4 of [RFC4648].

   where the URI section is comprised of one of more of the ordered
   sequence of:

      1.1)  an rsync URI [RFC5781],

      1.2)  a <CRLF> or <LF> line break.

2.2.  TAL and Trust Anchor Certificate Considerations

   Each 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 [RFC6487].  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 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 [RFC6480].

   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

Huston, et al.          Expires September 5, 2014               [Page 4]
Internet-Draft          RPKI Trust Anchor Locator             March 2014

   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
   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 [RFC6486] that lists this certificate.

   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

   Where the TAL contains two or more rsync URIs, then the same self-
   signed CA certificate MUST be found at each referenced location.  In
   order to operational increase resilience, it is RECOMMENDED that the
   domain name parts of each of these URIs resolve to distinct IP
   addresses that are used by a diverse set of repository publication
   points, and these IP addresses be included in distinct Route
   Origination Authorizations (ROAs) objects signed by different CAs.

2.3.  Example


Huston, et al.          Expires September 5, 2014               [Page 5]
Internet-Draft          RPKI Trust Anchor Locator             March 2014

3.  Relying Party Use

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

   1.  Retrieve the object referenced by (one of) the URI(s) 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

   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

   In the case where a TAL contains multiple URIs, an RP MAY use a
   locally defined preference rule to select the URI to retrieve the
   self-signed RPKI CA certificate that is to be used as a trust anchor.
   Some examples are:
   o  Using the order provided in the TAL
   o  Selecting the URI randomly from the available list
   o  Creating a prioritized list of URIs based on RP-specific
      parameters, such as connection establishment delay

   If the connection to the preferred URI fails, or the retrieved CA
   certificate public key does not match the TAL public key, the RP
   SHOULD retrieve the CA certificate from the next URI, according to
   the local preference ranking of URIs.

4.  Security Considerations

   Compromise of a trust anchor private key permits unauthorized parties
   to masquerade as a trust anchor, with potentially severe

Huston, et al.          Expires September 5, 2014               [Page 6]
Internet-Draft          RPKI Trust Anchor Locator             March 2014

   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 thetrust anchor 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.

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.

   The authors acknowledge with work of Roque Gagliano, Terry Manderson
   and Carloa Martinez Cagnazzo in developing the ideas behind the
   inclusion of multiple URIs in the TAL.

7.  References

7.1.  Normative References

   [RFC2119]  Bradner, S., "Key words for use in RFCs to Indicate
              Requirement Levels", BCP 14, RFC 2119, March 1997.

   [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.,

Huston, et al.          Expires September 5, 2014               [Page 7]
Internet-Draft          RPKI Trust Anchor Locator             March 2014

              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.

   [RFC6480]  Lepinski, M. and S. Kent, "An Infrastructure to Support
              Secure Internet Routing", RFC 6480, February 2012.

   [RFC6487]  Huston, G., Michaelson, G., and R. Loomans, "A Profile for
              X.509 PKIX Resource Certificates", RFC 6487,
              February 2012.

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

7.2.  Informative References

   [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.

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

   [RFC6486]  Austein, R., Huston, G., Kent, S., and M. Lepinski,
              "Manifests for the Resource Public Key Infrastructure
              (RPKI)", RFC 6486, February 2012.

Authors' Addresses

   Geoff Huston


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


Huston, et al.          Expires September 5, 2014               [Page 8]
Internet-Draft          RPKI Trust Anchor Locator             March 2014

   George Michaelson
   Asia Pacific Network Information Centre


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


Huston, et al.          Expires September 5, 2014               [Page 9]