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Internet Engineering Task Force (IETF)                         G. HustonRequest for Comments: 6490                                         APNICCategory: Standards Track                                      S. WeilerISSN: 2070-1721                                             SPARTA, Inc.                                                           G. Michaelson                                                                   APNIC                                                                 S. Kent                                                                     BBN                                                           February 2012Resource Public Key Infrastructure (RPKI) Trust Anchor LocatorAbstract   This document defines a Trust Anchor Locator (TAL) for the Resource   Public Key Infrastructure (RPKI).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 inSection 2 of RFC 5741.   Information about the current status of this document, any errata,   and how to provide feedback on it may be obtained athttp://www.rfc-editor.org/info/rfc6490.Copyright Notice   Copyright (c) 2012 IETF Trust and the persons identified as the   document authors.  All rights reserved.   This document is subject toBCP 78 and the IETF Trust's Legal   Provisions Relating to IETF Documents   (http://trustee.ietf.org/license-info) 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   the Trust Legal Provisions and are provided without warranty as   described in the Simplified BSD License.Huston, et al.               Standards Track                    [Page 1]

RFC 6490                RPKI Trust Anchor Locator          February 2012Table of Contents1. Introduction ....................................................21.1. Terminology ................................................22. Trust Anchor Locator ............................................22.1. Trust Anchor Locator Format ................................22.2. TAL and Trust Anchor Certificate Considerations ............32.3. Example ....................................................43. Relying Party Use ...............................................54. Security Considerations .........................................55. Acknowledgments .................................................66. References ......................................................66.1. Normative References .......................................66.2. Informative References .....................................61.  Introduction   This document defines a Trust Anchor Locator (TAL) for the Resource   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",   "SHOULD", "SHOULD NOT", "RECOMMENDED", "MAY", and "OPTIONAL" in this   document are to be interpreted as described in [RFC2119].2.  Trust Anchor Locator2.1.  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 Certification Authority (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 trust anchor in a very simple fashion.  That data   is referred to as the TAL.   The motivation for defining the TAL is to enable selected data in the   trust anchor to change, without needing to effect redistribution 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 ofHuston, et al.               Standards Track                    [Page 2]

RFC 6490                RPKI Trust Anchor Locator          February 2012   distributing a trust anchor to RPs in a secure fashion, this   procedure would need to be repeated whenever the INR set for the   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 trust anchor's public key and its location   do 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   the requisite extension.  The community also prefers the simplicity   of the ASCII encoding of the TAL versus the binary (ASN.1) encoding   for TrustAnchorInfo.   The TAL is an ordered sequence of:   1) An rsync URI [RFC5781],   2) A <CRLF> or <LF> line break, and   3) A subjectPublicKeyInfo [RFC5280] in DER format [X.509], encoded in      Base64 (seeSection 4 of [RFC4648]).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 [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 for the particular set of INRs that   are associated with the putative trust anchor.   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.Huston, et al.               Standards Track                    [Page 3]

RFC 6490                RPKI Trust Anchor Locator          February 2012   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 Certificate Revocation   List (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 reissued for any reason, the replacement CA certificate   MUST be accessible using the same URI.   Because the trust anchor is a self-signed certificate, there is no   corresponding CRL 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   TAL.2.3.  Example   rsync://rpki.example.org/rpki/hedgehog/root.cer   MIIBIjANBgkqhkiG9w0BAQEFAAOCAQ8AMIIBCgKCAQEAovWQL2lh6knDx   GUG5hbtCXvvh4AOzjhDkSHlj22gn/1oiM9IeDATIwP44vhQ6L/xvuk7W6   Kfa5ygmqQ+xOZOwTWPcrUbqaQyPNxokuivzyvqVZVDecOEqs78q58mSp9   nbtxmLRW7B67SJCBSzfa5XpVyXYEgYAjkk3fpmefU+AcxtxvvHB5OVPIa   BfPcs80ICMgHQX+fphvute9XLxjfJKJWkhZqZ0v7pZm2uhkcPx1PMGcrG   ee0WSDC3fr3erLueagpiLsFjwwpX6F+Ms8vqz45H+DKmYKvPSstZjCCq9   aJ0qANT9OtnfSDOS+aLRPjZryCNyvvBHxZXqj5YCGKtwIDAQABHuston, et al.               Standards Track                    [Page 4]

RFC 6490                RPKI Trust Anchor Locator          February 20123.  Relying Party Use   In order to use the TAL to retrieve and validate a (putative) trust   anchor, an RP SHOULD:   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      [RFC6487].   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.  These checks apply to      the validity of attestations made in the context of the RPKI,      relating to all resources described in the INR extension of this      certificate.   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 TAL.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 TAL does not directly provide a list of resources covered by the   referenced self-signed CA certificate.  Instead, the RP is referred   to the trust 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.  For more information on this approach, see [TA-MGMT].Huston, et al.               Standards Track                    [Page 5]

RFC 6490                RPKI Trust Anchor Locator          February 20125.  Acknowledgments   This approach to trust anchor material was originally described by   Robert Kisteleki.   The authors acknowledge the contributions of Rob Austein and Randy   Bush, who assisted with earlier draft versions of this document and   with helpful review comments.6.  References6.1.  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.,              Housley, R., and W. Polk, "Internet X.509 Public Key              Infrastructure Certificate and Certificate Revocation List              (CRL) Profile",RFC 5280, May 2008.   [RFC5781]  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.   [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", 2000.6.2.  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.Huston, et al.               Standards Track                    [Page 6]

RFC 6490                RPKI Trust Anchor Locator          February 2012   [RFC6480]  Lepinski, M. and S. Kent, "An Infrastructure to Support              Secure Internet Routing",RFC 6480, February 2012.   [RFC6486]  Austein, R., Huston, G., Kent, S., and M. Lepinski,              "Manifests for the Resource Public Key Infrastructure              (RPKI)",RFC 6486, February 2012.   [TA-MGMT]  Reynolds, M. and S. Kent, "Local Trust Anchor Management              for the Resource Public Key Infrastructure", Work in              Progress, December 2011.Authors' Addresses   Geoff Huston   APNIC   EMail: gih@apnic.net   URI:http://www.apnic.net   Samuel Weiler   SPARTA, Inc.   7110 Samuel Morse Drive   Columbia, Maryland  21046   USA   EMail: weiler@tislabs.com   George Michaelson   APNIC   EMail: ggm@apnic.net   URI:http://www.apnic.net   Stephen Kent   BBN Technologies   10 Moulton St.   Cambridge, MA  02138   USA   EMail: kent@bbn.comHuston, et al.               Standards Track                    [Page 7]