Network Working Group S. Krishnan
Internet-Draft Ericsson
Intended status: Standards Track A. Kukec
Expires: September 10, 2009 University of Zagreb
K. Ahmed
Microsoft
March 9, 2009
Certificate profile and certificate management for SEND
draft-krishnan-cgaext-send-cert-eku-03
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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.
Table of Contents
1. Requirements notation . . . . . . . . . . . . . . . . . . . . 3
2. Introduction . . . . . . . . . . . . . . . . . . . . . . . . . 4
3. Certificate Management in SEND . . . . . . . . . . . . . . . . 5
3.1. Motivations for using RPKI . . . . . . . . . . . . . . . . 5
4. Certificate profile . . . . . . . . . . . . . . . . . . . . . 6
4.1. Extended Key Usage Values . . . . . . . . . . . . . . . . 6
5. Backward Compatibility . . . . . . . . . . . . . . . . . . . . 8
6. Security Considerations . . . . . . . . . . . . . . . . . . . 9
7. Acknowledgements . . . . . . . . . . . . . . . . . . . . . . . 10
8. Normative References . . . . . . . . . . . . . . . . . . . . . 11
Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . . 12
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1. 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].
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2. Introduction
Secure Neighbor Discovery [RFC3971] Utilizes X.509v3 certificates for
performing router authorization. It uses the X.509 extension for IP
addresses to verify whether the router is authorized to advertise the
mentioned IP addresses.
The SEND specification does not describe the set of extensions that
need to be supported and the revocation mechanisms for SEND
certificates. This document uses the Resource Certificates specified
in [RES-CERTS] in order to provide this information.
Also, since the IP addresses extension does not mention what
functions the subject of the certificate can perform for the IP
addresses, it becomes impossible to know the reason for which the
certificate was issued. In order to facilitate issuance of
certificates for specific functions, this document utilizes the
ExtKeyUsageSyntax field of the X.509 certificate to mention the
purpose for which the certificate was issued. This document
specifies three extended key usage values, one for routers, one for
proxies, and one for address owners, for use with SEND.
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3. Certificate Management in SEND
A certification path in SEND is transported in Certification Path
Advertisement (CPA) message sent from a router to SEND host. CPA
message is sent in reply to the Certification Path Solicitation
message (CPS) message. The certification path sent in CPA message is
a path between a router and SEND host's trust anchor and it might be
potentially voluminous. Thus, CPA and CPS messages are kept separate
from the rest of SEND messages.
SEND specification does not define any certificate management
routines (certificate issuance and revocation). The only two
routines described in SEND specification are the Certificate path
validation and IP address extension verification.
3.1. Motivations for using RPKI
This draft recommends that the SEND PKI be made part of the bigger
RPKI [SIDR-ARCH]. The main advantages of this model are:
o It is a global model suitable for mobile users. The RPKI has
default trust anchors that are widely used and available for
mobile users.
o The RPKI project (certificate management and certificate profile)
has been adopted by all the RIRs and IANA. SEND could simply
adopt well-known and already accepted RPKI mechanisms.
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4. Certificate profile
End entity certificates issued in support of SeND MUST comply with
the RPKI resource profile [RES-CERTS]. CA certificates used to
verify these router (EE) certificates also MUST comply with this
profile. This implies that these CA certificates MUST contain at an
RFC 3779 address extension representing the address space allocations
held by the service provider represented by the CA.
Relying parties (e.g., user devices that implement SeND and process
these router certificates) MUST be configured with one or more trust
anchors, to enable validation of the router certificates. These
trust anchors MAY be the default trust anchors defined for the RPKI,
or they MAY be self-signed (CA) certificates associated with the
service providers operating the routers in question. In either case,
it is RECOMMENDED that the RPKI trust anchor representation defined
in [RES-CERTS] be employed.
Because of the flexibility afforded service through (local) trust
anchor configuration, certificates used for SeND support can be
issued prior to issuance of RPKI certificates under the global
address allocation hierarchy. Note, however, that a CA certificate
issued independently of the global RPKI will have to be reissued in
order to integrate a local PKI with the global RPKI.
In addition to conforming to the Resource Certificate Profile as
specified in [RES-CERTS] the SEND certificate MUST support the
Extended Key Usage extension. The Extended Key Usage extension is
described in section 5.1. It MUST be marked as critical.
4.1. 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 key
usage extension, which indicates the intended purpose of the
certified public key.
The extended key usage extension syntax is repeated here for
convenience:
ExtKeyUsageSyntax ::= SEQUENCE SIZE (1..MAX) OF KeyPurposeId
KeyPurposeId ::= OBJECT IDENTIFIER
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This specification defines three KeyPurposeId values: one for
authorizing routers, one for authorizing proxies, and one for address
owners.
The inclusion of the router authorization value indicates that the
certificate has been issued for allowing the router to advertise
prefix(es) that are mentioned using the X.509 extensions for IP
addresses and AS identifiers [RFC3779]
The inclusion of the proxy authorization value indicates that the
certificate has been issued for allowing the proxy to perform
proxying of neighbor discovery messages for the prefix(es) that are
mentioned using the X.509 extensions for IP addresses and AS
identifiers [RFC3779]
The inclusion of the owner authorization value indicates that the
certificate has been issued for allowing the node to use the
address(es) or prefix(es) that are mentioned using the X.509
extensions for IP addresses and AS identifiers [RFC3779]
Inclusion of multiple values indicates that the certified public key
is appropriate for use by a node performing more than one of these
functions.
send-kp OBJECT IDENTIFIER ::=
{ iso(1) identified-organization(3) dod(6) internet(1)
security(5) mechanisms(5) TBA1 }
id-kp-sendRouter OBJECT IDENTIFIER ::= { send-kp 1 }
id-kp-sendProxy OBJECT IDENTIFIER ::= { send-kp 2 }
id-kp-sendOwner OBJECT IDENTIFIER ::= { send-kp 3 }
The extended key usage extension MAY, at the option of the
certificate issuer, be either critical or non-critical.
Certificate-using applications MAY 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-sendProxy) within the extended key usage extension. If
multiple KeyPurposeId values are included, the certificate-using
application need not recognize all of them, as long as the required
KeyPurposeId value is present.
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5. Backward Compatibility
The disadvantages of this model are related to the fact that the SEND
specification was developed before the standardization of the RPKI.
Hence, SEND is not completely compliant with the RPKI specifications
since it defines its own IP prefix validation routine and it is not
suitable for the use with CRLs, while the RPKI suports only CRLs.
This means that SEND implementations supporting this profile will not
be able to interoperate with legacy SEND implementations.
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6. 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.
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7. Acknowledgements
The authors would like to thank Steve Kent, Richard Barnes, Sandy
Murphy, Marcelo Bagnulo, and Gabriel Montenegro for reviewing earlier
versions of this document and suggesting text to make the document
better.
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8. Normative References
[RES-CERTS]
Huston, G., Michaelson, G., and R. Loomans, "A Profile for
X.509 PKIX Resource Certificates",
draft-ietf-sidr-res-certs-16 (work in progress),
February 2009.
[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.
[RFC3971] Arkko, J., Kempf, J., Zill, B., and P. Nikander, "SEcure
Neighbor Discovery (SEND)", RFC 3971, March 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.
[SIDR-ARCH]
Lepinski, M. and S. Kent, "An Infrastructure to Support
Secure Internet Routing", draft-ietf-sidr-arch-04 (work in
progress), November 2008.
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Authors' Addresses
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
University of Zagreb
Unska 3
Zagreb
Croatia
Email: ana.kukec@fer.hr
Khaja Ahmed
Microsoft
Email: khaja@windows.microsoft.com
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