Certificate Profile and Certificate Management for SEcure Neighbor Discovery (SEND)
RFC 6494

Internet Engineering Task Force (IETF)                       R. Gagliano
Request for Comments: 6494                                 Cisco Systems
Updates: 3971                                                S. Krishnan
Category: Standards Track                                       Ericsson
ISSN: 2070-1721                                                 A. Kukec
                                                   Enterprise Architects
                                                           February 2012

           Certificate Profile and Certificate Management for
                    SEcure Neighbor Discovery (SEND)

Abstract

   SEcure Neighbor Discovery (SEND) utilizes X.509v3 certificates for
   performing router authorization.  This document specifies a
   certificate profile for SEND based on resource certificates along
   with extended key usage values required for SEND.

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 5741.

   Information about the current status of this document, any errata,
   and how to provide feedback on it may be obtained at
   http://www.rfc-editor.org/info/rfc6494.

Copyright Notice

   Copyright (c) 2012 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
   (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.

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Table of Contents

   1. Introduction ....................................................2
   2. Requirements Notation ...........................................3
   3. Terminology .....................................................3
   4. SEND Certificate Profile ........................................4
      4.1. Unconstrained Certified Subnet Prefixes ....................4
   5. Deployment Models ...............................................5
   6. Trust Anchor Material ...........................................5
   7. Extended Key Usage Values .......................................6
   8. CRL Profile and Revocation ......................................7
      8.1. Online Certificate Status Protocol (OCSP) Considerations ...7
   9. Certificate Validation ..........................................8
   10. IANA Considerations ............................................8
   11. Security Considerations ........................................8
   12. Acknowledgements ...............................................8
   13. References .....................................................9
      13.1. Normative References ......................................9
      13.2. Informative References ....................................9
   Appendix A. Router Authorization Certificate Example ..............10
   Appendix B. ASN.1 Module ..........................................11

1.  Introduction

   SEcure Neighbor Discovery (SEND) [RFC3971] utilizes X.509v3
   certificates that include the [RFC3779] extension for IPv6 addresses
   to certify a router's authorization to advertise the IPv6 prefix for
   the Neighbor Discovery (ND) protocol.  The SEND specification defines
   a basic certificate profile for SEND.  The certificate profile
   defined in this document supersedes the profile for Router
   Authorization Certificates specified in [RFC3971].  That is,
   certificates used in SEND (by routers, proxies, or address owners)
   MUST conform to this certificate profile and MAY conform to the
   original profile in [RFC3971].

   The Resource Public Key Infrastructure (RPKI) is the global PKI that
   attests to the allocation of IP address space.  The RPKI represents
   the centralized model discussed in Section 6.2 of [RFC3971].
   Consequently, SEND will use the RPKI Certificate Profile and
   certificate validation detailed in [RFC6487].  Consequently, the
   certificate validation method described in [RFC3971] is updated with
   the certificate validation method in [RFC6487].

   Since the [RFC3779] IPv6 address extension does not mention what
   functions the node can perform for the certified IPv6 space, it
   becomes impossible to know the reason for which the certificate was
   issued.  In order to facilitate issuance of certificates for specific
   functions, it is necessary to utilize the ExtKeyUsageSyntax field

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   (optional in RPKI certificates) of the X.509 certificate to mention
   why the certificate was issued.  This document specifies four
   extended key usage values -- one for routers, two for proxies, and
   one for address owners -- for use with SEND.

   In RFC 3971, two deployment models were described: centralized and
   decentralized.  This document describes the different deployment
   models that can be used with the SEND certificates defined here.

2.  Requirements Notation

   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].

3.  Terminology

   Certified IPv6 address space  IPv6 address space included in an
                                 X.509v3 certificate using the extension
                                 for IPv6 addresses [RFC3779].

   End-entity (EE)               An entity in the PKI that is not a
                                 Certification Authority (CA).

   ISP                           Internet Service Provider.

   NIR                           National Internet Registry.

   RIR                           Regional Internet Registry.

   RPKI                          Resource PKI established in accordance
                                 with [RFC6480].

   RPKI certificates             Certificates as defined in [RFC6487].

   SEND certificates             Certificates as described in [RFC3971]
                                 and extended in this document.  They
                                 are end-entity certificates that belong
                                 either to SEND routers, SEND hosts, or
                                 SEND proxies:

                                 *  Router Authorization Certificates as
                                    defined in [RFC3971].

                                 *  Owner Authorization Certificates as
                                    defined in [RFC3971].

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                                 *  Secure Proxy ND Certificates as
                                    defined in [RFC6496].

   SEND KeyPurposeId             An Extended Key Usage (EKU) value for
                                 SEND, such as the four introduced in
                                 this document.

4.  SEND Certificate Profile

   SEND certificates MUST comply with the RPKI resource profile
   described in [RFC6487].  A Router Authorization Certificate example
   is included in Appendix A.

   In Sections 2, 4.9.10, and 4.9.11 of [RFC6487], it is stated that
   RFC 3779 resource extensions MUST be marked as critical and MUST be
   present in all resource certificates.  SEND certificates MUST include
   the IP Address Delegation extension [RFC3779].  This extension MUST
   include at least one address block for the IPv6 Address Family
   (AFI=0002), as described in Section 4.9.10 of [RFC6487].  SEND
   certificates MUST NOT have more than one IP Address Delegation
   extension.

4.1.  Unconstrained Certified Subnet Prefixes

   Section 7.3 of [RFC3971] defines the Unconstrained Certified subnet
   prefixes category by using certificates containing either the null
   prefix or no prefix extension at all.

   When using the RPKI Certificate Profile, prefix extensions are
   mandatory and the null prefix MUST be validated.  However, a
   certificate may inherit its parent's prefix or range by using the
   "inherit" element for the IPv6 Address Family Identifier (AFI) as
   defined in [RFC3779].  The use of the "inherit" element is permitted
   in [RFC6487].

   Consequently, this document updates Section 7.3 of [RFC3971], adding
   the following text under Unconstrained:

   Network operators that do not want to constrain routers to route
   particular subnet prefixes, but rather inherit those prefixes from
   the routers' parent certificates, should configure routers with
   certificates containing the "inherit" element for the IPv6 AFI.

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5.  Deployment Models

   RFC 3971 describes two deployment models: centralized and
   decentralized.  These models were differentiated by having one trust
   anchor or many trust anchors.  In this document, we introduce two new
   deployment models not based on the number of trust anchors but on the
   localization of the SEND deployment.

   The local SEND deployment model represents those cases where SEND
   deployment is confined to an administrative domain.  In this
   scenario, the deployment of SEND MAY be done independently of the
   existence of deployment in the upper RPKI hierarchy (i.e., an end
   user could perform local SEND deployment without the need for RPKI
   deployment in its ISP).  This model requires the use of local trust
   anchors and configuring islands of trust.  This model MAY include
   Unique Local Addresses (ULAs) [RFC4193].

   The public SEND deployment models represent those cases where SEND
   deployment is linked to RPKI deployment as described in [RFC6480].
   Trust anchor material MAY be part of a different administrative
   domain (i.e., RIRs, NIRs, or ISPs).  It is a global model suitable
   for mobile users.

   These two models are not mutually exclusive.  It is entirely possible
   to have a hybrid model that incorporates features from both of these
   models.  In one such hybrid deployment model, most IP address
   resources (e.g., global unicast addresses) would be certified under
   the global RPKI, while some others (e.g., ULAs) are certified under
   local trust anchors.

6.  Trust Anchor Material

   Relying parties (e.g., end hosts that implement SEND and process
   these router certificates) MUST be configured with one or more trust
   anchors to enable validation of the routers' certificates.  [RFC6495]
   and Section 6.5 of [RFC3971] list the trust anchor configuration
   options for end hosts using SEND.

   In the local SEND deployment model, it is possible to use as a trust
   anchor a certificate that includes in its RFC 3779 address extension
   the prefix ::/0.  In this case, no new trust anchor material would be
   needed when renumbering.  However, if trying to move from the local
   deployment model to the public deployment model, new trust anchor
   material will have to be distributed to relying parties.

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7.  Extended Key Usage Values

   The Internet PKI document [RFC5280] specifies the extended key usage
   X.509 certificate extension.  The extension indicates one or more
   purposes for which the certified public key may be used.  The
   extended key usage extension can be used in conjunction with the key
   usage extension, which indicates the intended purpose of the
   certified public key.  The EKU extension is defined as optional in
   [RFC6487] for end-entity certificates but MUST be present when
   issuing end-entity certificates for SEND.

   The extended key usage extension syntax is repeated here for
   convenience:

      ExtKeyUsageSyntax ::= SEQUENCE SIZE (1..MAX) OF KeyPurposeId

      KeyPurposeId ::= OBJECT IDENTIFIER

   This specification defines four KeyPurposeId values: one for
   authorizing routers (Router Authorization Certificates), two for
   authorizing proxies (Secure Proxy ND Certificates), and one for
   address owners (Owner Authorization Certificates).  Additional
   KeyPurposeId values may be specified in Standards Track documents.

   The inclusion of the router authorization value (id-kp-sendRouter)
   indicates that the certificate has been issued for allowing the
   router to generate Router Advertisement (RA) and Redirect messages
   for any prefix(es) encompassed (as defined in Section 7.1 of
   [RFC6487]) by the IP address space included in the X.509 extensions
   for IP addresses.

   The inclusion of the proxied routing authorization value
   (id-kp-sendProxiedRouter) indicates that the certificate has been
   issued for allowing the proxy to perform proxying of RA and Redirect
   messages for any prefix(es) encompassed by the IP address space
   included in the X.509 extensions for IP addresses.

   The inclusion of the owner authorization value (id-kp-sendOwner)
   indicates that the certificate has been issued for allowing the node
   to use any address(es) that is/are encompassed by the IP address
   space included in the X.509 extensions for IP addresses.  For an
   address in such a certificate, the node can assign the address to an
   interface; send/receive traffic from/to this address; and send/
   respond to NS, NA, and RS messages related to that address.

   The inclusion of the proxied owner authorization value
   (id-kp-sendProxiedOwner) indicates that the certificate has been
   issued for allowing the proxy to perform proxying of Neighbor

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   Solicitation (NS), Neighbor Advertisement (NA), and Router
   Solicitation (RS) messages for any address encompassed by the IP
   address space included in the X.509 extensions for IP addresses.

      send-kp OBJECT IDENTIFIER ::=
        { iso(1) identified-organization(3) dod(6) internet(1)
          security(5) mechanisms(5) pkix(7) kp(3) }

      id-kp-sendRouter OBJECT IDENTIFIER ::= { id-kp 23 }

      id-kp-sendProxiedRouter OBJECT IDENTIFIER ::= { id-kp 24 }

      id-kp-sendOwner OBJECT IDENTIFIER ::= { id-kp 25 }

      id-kp-sendProxiedOwner OBJECT IDENTIFIER ::= { id-kp 26 }

   As described in [RFC6487], the extended key usage extension, if
   present, MUST be non-critical.

   Relying parties MUST require the extended key usage extension to be
   present in a certificate, and they MAY require a particular
   KeyPurposeId value to be present (such as id-kp-sendRouter or
   id-kp-sendProxiedRouter) within the extended key usage extension.  If
   multiple KeyPurposeId values are included, the relying parties need
   not recognize all of them, as long as the required KeyPurposeId value
   is present.  Relying parties MUST reject certificates that do not
   contain at least one SEND KeyPurposeId, even if they include the
   anyExtendedKeyUsage OID defined in [RFC5280].

8.  CRL Profile and Revocation

   RPKI requires the use of Certificate Revocation Lists (CRLs)
   [RFC6487].  The host will obtain the necessary CRLs and perform the
   certificate validation method described in [RFC6487].

8.1.  Online Certificate Status Protocol (OCSP) Considerations

   A host MAY use OCSP [RFC2560] to verify the revocation status of a
   certificate.

   As [RFC6487] is adopted as the base certificate profile for SEND, the
   host SHOULD NOT assume that certificates will include the URI of an
   OCSP server as part of its Authority Information Access (AIA)
   extension.  This is particularly evident in the SEND public
   deployment model, as OCSP services are not required by [RFC6484].

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9.  Certificate Validation

   This section updates Section 6.3.1 of [RFC3971] by introducing new
   validations without introducing any conflict.

   The host MUST perform the certificate validation method described in
   [RFC6487].  The validation of certificates that use the "inherit"
   element where the existence of a parent prefix or range is required
   is described in [RFC3779].

   The host MUST verify that the KeyPurposeId value corresponding to the
   Neighbor Discovery message type is present, as described in
   Section 7.

10.  IANA Considerations

   This document makes use of object identifiers to identify EKUs and
   the ASN.1 (Abstract Syntax Notation One) module found in Appendix B.
   The EKUs and ASN.1 module OID are registered in an arc delegated by
   IANA to the PKIX Working Group.

11.  Security Considerations

   The certification authority needs to ensure that the correct values
   for the extended key usage are inserted in each certificate that is
   issued.  Relying parties may accept or reject a particular
   certificate for an intended use based on the information provided in
   these extensions.  Incorrect representation of the information in the
   extended key usage field can cause the relying party to reject an
   otherwise appropriate certificate or accept a certificate that ought
   to be rejected.  In particular, since a SEND certificate attests that
   its subject is authorized to play a given role in the SEND protocol,
   certificates that contain incorrect EKU values can enable some of the
   same attacks that SEND was meant to prevent.  For example, if a
   malicious host can obtain a certificate that authorizes it to act as
   a router for a given prefix, then it can masquerade as a router for
   that prefix, e.g., in order to attract traffic from local nodes.

12.  Acknowledgements

   The authors would like to thank Alberto Garcia, Stephen Kent, Sean
   Turner, Roni Even, Richard Barnes, Alexey Melnikov, Jari Arkko, David
   Harrington, and Tim Polk for their reviews and suggestions on the
   earlier versions of this document.

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13.  References

13.1.  Normative References

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

   [RFC2560]  Myers, M., Ankney, R., Malpani, A., Galperin, S., and C.
              Adams, "X.509 Internet Public Key Infrastructure Online
              Certificate Status Protocol - OCSP", RFC 2560, June 1999.

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

   [RFC3971]  Arkko, J., Ed., Kempf, J., Zill, B., and P. Nikander,
              "SEcure Neighbor Discovery (SEND)", RFC 3971, March 2005.

   [RFC4193]  Hinden, R. and B. Haberman, "Unique Local IPv6 Unicast
              Addresses", RFC 4193, October 2005.

   [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.

   [RFC6484]  Kent, S., Kong, D., Seo, K., and R. Watro, "Certificate
              Policy (CP) for the Resource Public Key Infrastructure
              (RPKI)", BCP 173, RFC 6484, February 2012.

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

   [RFC6495]  Gagliano, R., Krishnan, S., and A. Kukec, "Subject Key
              Identifier (SKI) SEcure Neighbor Discovery (SEND) Name
              Type Fields", RFC 6495, February 2012.

13.2.  Informative References

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

   [RFC6496]  Krishnan, S., Laganier, J., Bonola, M., and A. Garcia-
              Martinez, "Secure Proxy ND Support for SEcure Neighbor
              Discovery (SEND)", RFC 6496, February 2012.

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Appendix A.  Router Authorization Certificate Example

   Certificate:
       Data:
           Version: 3 (0x2)
           Serial Number: 249 (0xf9)
           Signature Algorithm: sha256WithRSAEncryption
           Issuer: CN=EXAMPLE-CA-2342342652346
           Validity
               Not Before: Jul  2 10:06:32 2010 GMT
               Not After : Jul  2 10:06:32 2011 GMT
           Subject: CN=SEND-EXAMPLE-123432
           Subject Public Key Info:
               Public Key Algorithm: rsaEncryption
                   Public-Key: (2048 bit)
                   Modulus:
                       00:b7:06:0d:8e:f7:39:0a:41:52:93:59:a8:f5:63:
                       3f:2e:3d:24:17:9d:19:aa:09:ff:c0:2a:f3:c6:99:
                       d7:34:0d:bf:f1:e9:73:b5:8f:dc:d4:91:d6:5d:cb:
                       9c:b8:2b:41:63:c1:8f:f7:48:54:02:89:07:24:c3:
                       b0:6e:11:5a:7d:c0:38:88:4b:d9:3b:93:c7:ca:4d:
                       a4:00:a2:d3:6d:14:15:8f:15:08:4d:4e:b3:8a:cc:
                       de:2d:e0:7a:9b:c0:6e:14:f6:a7:ae:b9:e0:c5:18:
                       60:75:3d:d3:50:00:47:0d:86:5b:1c:a0:85:81:af:
                       2b:84:98:49:7d:60:a2:e8:4f:6d:40:ba:d5:fe:de:
                       de:41:53:c7:c4:f4:d3:1a:41:cd:dc:9f:08:43:33:
                       48:00:57:e4:56:93:7d:dd:19:12:e8:bf:26:b3:4b:
                       30:ac:b8:9c:b1:37:05:18:3c:7b:6b:26:d7:c9:15:
                       c9:4a:eb:1b:fa:92:38:46:27:44:96:8a:a1:12:c1:
                       09:77:4a:7b:a5:07:88:a6:36:30:98:70:79:b6:44:
                       7e:b1:c9:4c:5b:11:56:e8:14:50:f7:f8:e5:ed:f1:
                       ac:a4:31:46:36:77:05:c9:63:fe:c3:ab:54:e2:bd:
                       79:1d:14:d1:c2:80:36:d3:be:e6:c7:a2:47:59:1b:
                       75:9f
                   Exponent: 65537 (0x10001)

           X509v3 extensions:
               X509v3 Authority Key Identifier:
                   keyid:4C:5D:56:82:15:8A:67:A6:8C:69:67:68:88
                   :6F:15:E5:C9:96:58:EB

               X509v3 CRL Distribution Points:

                   Full Name:
                     URI:rsync://rsync.example.exampledomain/
                     EXAMPLE-CA-2342342652346/EXAMPLE-CA.crl

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               X509v3 Subject Key Identifier:
                   B8:69:EB:36:23:F1:C4:21:65:DD:13:76:EE:90:AF
                   :F7:CD:E3:61:CD
               X509v3 Key Usage: critical
                   Digital Signature
               sbgp-ipAddrBlock: critical
                   IPv6:
                     2001:db8:cafe:bebe::/64

               X509v3 Extended Key Usage:
                   1.3.6.1.5.5.7.3.23
       Signature Algorithm: sha256WithRSAEncryption
           92:14:38:6e:45:83:1b:cb:7c:45:0d:bc:7f:6e:36:bf:82:cc:
           7e:00:91:ea:f4:24:43:cc:00:3c:3f:c2:99:0c:c6:b9:20:2e:
           ca:dc:df:94:0d:c9:a1:75:c4:5c:39:a1:cf:9f:e1:40:9c:aa:
           a9:80:76:d1:3a:91:d9:db:2f:cd:3c:05:50:52:eb:28:47:d0:
           ab:d3:fd:6f:30:17:16:7f:c6:0f:2b:25:bb:db:29:d7:bb:4e:
           f3:7c:2d:e1:04:b7:f0:bc:d5:8a:ba:8c:0d:39:22:48:02:d1:
           67:fb:35:5c:b6:83:03:63:7c:73:03:70:20:de:fb:d7:12:ed:
           6f:a1:ff:b2:a6:39:fb:55:9a:07:bd:68:40:0f:6f:d5:24:34:
           cf:e8:dd:76:33:2a:d0:b9:1b:ae:a8:68:86:17:f8:13:35:0e:
           f6:04:ec:2a:39:88:06:70:c6:e8:56:87:f7:35:54:2a:28:2c:
           92:47:a9:89:39:d7:72:24:21:9d:02:52:f9:7c:76:7f:e9:cd:
           09:6e:82:f4:da:6c:f9:72:b2:64:98:b5:0c:6a:38:8d:81:e5:
           fc:50:46:6f:38:40:56:06:92:5a:e0:86:5d:55:f5:7b:85:b2:
           68:4f:49:72:e0:fa:2c:bf:9e:7d:aa:28:17:ca:04:b8:ae:69:
           c9:04:28:12

Appendix B.  ASN.1 Module

   SENDCertExtns { iso(1) identified-organization(3) dod(6) internet(1)
   security(5) mechanisms(5) pkix(7) id-mod(0)
   id-mod-send-cert-extns(71) }

   DEFINITIONS IMPLICIT TAGS ::=

   BEGIN

   -- OID Arc

   id-kp OBJECT IDENTIFIER ::=
   { iso(1) identified-organization(3) dod(6) internet(1)
   security(5) mechanisms(5) pkix(7) kp(3) }

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   -- Extended Key Usage Values

   id-kp-sendRouter OBJECT IDENTIFIER ::= { id-kp 23 }
   id-kp-sendProxiedRouter OBJECT IDENTIFIER ::= { id-kp 24 }
   id-kp-sendOwner OBJECT IDENTIFIER ::= { id-kp 25 }
   id-kp-sendProxiedOwner OBJECT IDENTIFIER ::= { id-kp 26 }

   END

Authors' Addresses

   Roque Gagliano
   Cisco Systems
   Avenue des Uttins 5
   Rolle  1180
   Switzerland

   EMail: rogaglia@cisco.com

   Suresh Krishnan
   Ericsson
   8400 Decarie Blvd.
   Town of Mount Royal, QC
   Canada

   Phone: +1 514 345 7900 x42871
   EMail: suresh.krishnan@ericsson.com

   Ana Kukec
   Enterprise Architects
   46/525 Collins St.
   Melbourne, VIC 3000
   Australia

   EMail: ana.kukec@enterprisearchitects.com

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