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IETF RFC 6494
Last modified on Saturday, February 4th, 2012
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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/RFC 6494.
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.
Gagliano, et al. Standards Track PAGE 1 
RFC 6494 SEND Certificate Profile and Management February 2012
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) [RFC 3971] utilizes X.509v3
certificates that include the [RFC 3779] 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 [RFC 3971]. 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 [RFC 3971].
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 [RFC 3971].
Consequently, SEND will use the RPKI Certificate Profile and
certificate validation detailed in [RFC 6487]. Consequently, the
certificate validation method described in [RFC 3971] is updated with
the certificate validation method in [RFC 6487].
Since the [RFC 3779] 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
Gagliano, et al. Standards Track PAGE 2
RFC 6494 SEND Certificate Profile and Management February 2012
(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 [RFC 2119].
3. Terminology
Certified IPv6 address space IPv6 address space included in an
X.509v3 certificate using the extension
for IPv6 addresses [RFC 3779].
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 [RFC 6480].
RPKI certificates Certificates as defined in [RFC 6487].
SEND certificates Certificates as described in [RFC 3971]
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 [RFC 3971].
* Owner Authorization Certificates as
defined in [RFC 3971].
Gagliano, et al. Standards Track PAGE 3
RFC 6494 SEND Certificate Profile and Management February 2012
* Secure Proxy ND Certificates as
defined in [RFC 6496].
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 [RFC 6487]. A Router Authorization Certificate example
is included in Appendix A.
In Sections 2, 4.9.10, and 4.9.11 of [RFC 6487], 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 [RFC 3779]. This extension MUST
include at least one address block for the IPv6 Address Family
(AFI=0002), as described in Section 4.9.10 of [RFC 6487]. SEND
certificates MUST NOT have more than one IP Address Delegation
extension.
4.1. Unconstrained Certified Subnet Prefixes
Section 7.3 of [RFC 3971] 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 [RFC 3779]. The use of the "inherit" element is permitted
in [RFC 6487].
Consequently, this document updates Section 7.3 of [RFC 3971], 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.
Gagliano, et al. Standards Track PAGE 4
RFC 6494 SEND Certificate Profile and Management February 2012
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) [RFC 4193].
The public SEND deployment models represent those cases where SEND
deployment is linked to RPKI deployment as described in [RFC 6480].
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. [RFC 6495]
and Section 6.5 of [RFC 3971] 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.
Gagliano, et al. Standards Track PAGE 5
RFC 6494 SEND Certificate Profile and Management February 2012
7. Extended Key Usage Values
The Internet PKI document [RFC 5280] 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
[RFC 6487] 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
[RFC 6487]) 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
Gagliano, et al. Standards Track PAGE 6
RFC 6494 SEND Certificate Profile and Management February 2012
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 [RFC 6487], 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 [RFC 5280].
8. CRL Profile and Revocation
RPKI requires the use of Certificate Revocation Lists (CRLs)
[RFC 6487]. The host will obtain the necessary CRLs and perform the
certificate validation method described in [RFC 6487].
8.1. Online Certificate Status Protocol (OCSP) Considerations
A host MAY use OCSP [RFC 2560] to verify the revocation status of a
certificate.
As [RFC 6487] 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 [RFC 6484].
Gagliano, et al. Standards Track PAGE 7
RFC 6494 SEND Certificate Profile and Management February 2012
9. Certificate Validation
This section updates Section 6.3.1 of [RFC 3971] by introducing new
validations without introducing any conflict.
The host MUST perform the certificate validation method described in
[RFC 6487]. The validation of certificates that use the "inherit"
element where the existence of a parent prefix or range is required
is described in [RFC 3779].
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.
Gagliano, et al. Standards Track PAGE 8
RFC 6494 SEND Certificate Profile and Management February 2012
13. References
13.1. Normative References
[RFC 2119] Bradner, S., "Key words for use in RFCs to Indicate
Requirement Levels", BCP 14, RFC 2119, March 1997.
[RFC 2560] 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.
[RFC 3779] Lynn, C., Kent, S., and K. Seo, "X.509 Extensions for IP
Addresses and AS Identifiers", RFC 3779, June 2004.
[RFC 3971] Arkko, J., Ed., Kempf, J., Zill, B., and P. Nikander,
"SEcure Neighbor Discovery (SEND)", RFC 3971, March 2005.
[RFC 4193] Hinden, R. and B. Haberman, "Unique Local IPv6 Unicast
Addresses", RFC 4193, October 2005.
[RFC 5280] 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.
[RFC 6484] 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.
[RFC 6487] Huston, G., Michaelson, G., and R. Loomans, "A Profile for
X.509 PKIX Resource Certificates", RFC 6487,
February 2012.
[RFC 6495] 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
[RFC 6480] Lepinski, M. and S. Kent, "An Infrastructure to Support
Secure Internet Routing", RFC 6480, February 2012.
[RFC 6496] Krishnan, S., Laganier, J., Bonola, M., and A. Garcia-
Martinez, "Secure Proxy ND Support for SEcure Neighbor
Discovery (SEND)", RFC 6496, February 2012.
Gagliano, et al. Standards Track PAGE 9
RFC 6494 SEND Certificate Profile and Management February 2012
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
Gagliano, et al. Standards Track PAGE 10
RFC 6494 SEND Certificate Profile and Management February 2012
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) }
Gagliano, et al. Standards Track PAGE 11
RFC 6494 SEND Certificate Profile and Management February 2012
-- 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
Gagliano, et al. Standards Track PAGE 12
RFC TOTAL SIZE: 26425 bytes
PUBLICATION DATE: Saturday, February 4th, 2012
LEGAL RIGHTS: The IETF Trust (see BCP 78)
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