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Working Group                                                U. Chunduri
Internet-Draft                                                   A. Tian
Intended status: Informational                             Ericsson Inc.
Expires: April 8, 2013                                   October 5, 2012

                KARP KMP: Simplified Peer Authentication


   This document describes the usage of Router Fingerprint
   Authentication (RFA) with public keys as a potential peer
   authentication method with KARP Key Management Protocol (KMP).  The
   advantage of RFA is, neither it requires out-of-band, mutually
   agreeable symmetric keys nor a full PKI based system (trust anchor or
   CA certificates) for mutual authentication of the peers with KARP KMP
   deployments.  Usage of Router Fingerprints give a significant
   operational improvement from symmetric key based systems and yet
   provide a secure authentication technique.

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
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   Internet-Drafts are draft documents valid for a maximum of six months
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   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 April 8, 2013.

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
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   (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

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   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.

Table of Contents

   1.  Introduction  . . . . . . . . . . . . . . . . . . . . . . . . . 3
     1.1.  Requirements Language . . . . . . . . . . . . . . . . . . . 4
     1.2.  Acronyms  . . . . . . . . . . . . . . . . . . . . . . . . . 4
   2.  Router Fingerprint  . . . . . . . . . . . . . . . . . . . . . . 4
   3.  Usage of Router Fingerprints with KARP KMP  . . . . . . . . . . 5
     3.1.  Impact on the PAD . . . . . . . . . . . . . . . . . . . . . 6
   4.  Publishing Router Fingerprints  . . . . . . . . . . . . . . . . 6
   5.  Scope of Fingerprints usage with RPs  . . . . . . . . . . . . . 6
   6.  Fingerprint Revocation  . . . . . . . . . . . . . . . . . . . . 7
   7.  IANA Considerations . . . . . . . . . . . . . . . . . . . . . . 7
   8.  Security Considerations . . . . . . . . . . . . . . . . . . . . 7
   9.  Acknowledgements  . . . . . . . . . . . . . . . . . . . . . . . 7
   10. References  . . . . . . . . . . . . . . . . . . . . . . . . . . 8
     10.1. Normative References  . . . . . . . . . . . . . . . . . . . 8
     10.2. Informative References  . . . . . . . . . . . . . . . . . . 8
   Authors' Addresses  . . . . . . . . . . . . . . . . . . . . . . . . 9

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1.  Introduction

   A Key Management Protocol (KMP) framework for TCP-based pair wise
   routing protocols (BGP [RFC4271], PCEP [RFC5440], MSDP [RFC3618] and
   LDP [RFC5036]) is detailed in
   [chunduri-karp-using-ikev2-with-tcp-ao].  Usage of IKEv2[RFC5996] as
   the KMP is also described in the same document.  This draft explores
   a simple and secure authentication method, which can be used for KARP
   KMP deployments.

   Currently operators don't often change the manual keys deployed for
   protecting the Routing Protocol (RP) messages because of various
   reasons as noted in Section 2.3 of KARP threat document [I-D.ietf-
   karp-threats-reqs].  One of the KARP WG goals is to define mechanisms
   to support key changes for all RPs which use either Manual Key
   Management (MKM) or KMP with out much operational overhead.

   Apart from Peer's identity verification, authentication and parameter
   negotiation, deployment of KMP can be more useful, when it comes to
   rekey the keys used by RPs.  Rekeying can be achieved with out the
   operator's intervention and as per the provisioned rekey policy.  But
   for the operators, usage of IKEv2 KMP opens up numerous possibilities
   for peer authentication and manual symmetric keys not only to
   bootstrap KMP but used for peer authentication.  Various other peer
   authentication mechanisms with the advantages/drawbacks of each
   mechanisms are described in the Appendix of the [chunduri-karp-using-
   ikev2-with-tcp-ao] document.

   If symmetric pre-shared keys are used by IKEv2 KMP to authenticate
   the peer before generating the shared key(s), apart from the other
   issues with symmetric keys, the problem still remain the same when it
   comes to changing these keys.

   To reduce the operational costs for changing the keys at peering
   points with relatively large number of peers for various TCP based
   RPs, this document describes the use of one of the available IKEv2
   KMP peer authentication methods with raw or x.509 encoded public keys
   (to be called as Router Fingerprints in the rest of the document).
   Router Fingerprint Authentication (RFA) mechanism in conjunction with
   KARP KMP require neither out-of-band symmetric keys nor a fully
   functional PKI based system with trust anchor certificates as
   explained further in Section 2.

   Section 2 describes the Router Fingerprints in the context of various
   KMPs and specifically for IKEv2 KMP.  Generation and usage of the
   Router Fingerprints is described in Section 3 and Section 4 describes
   an error free method for publishing the Router Fingerprints.

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1.1.  Requirements Language

   The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT",
   document are to be interpreted as described in RFC 2119 [RFC2119].

1.2.  Acronyms

   CRL     -  Certificate Revocation List.

   EBGP    -  External BGP (BGP connection between external peers).

   EE      -  End Entity.

   IBGP    -  Internal BGP (BGP connection between internal peers).

   KMP     -  Key Management Protocol (auto key management).

   MKM     -  Manual Key management Protocols.

   PAD     -  Peer Authorization Database.

   RFA     -  Router Fingerprint Authentication.

   RP      -  Routing Protocol.

2.  Router Fingerprint

   Router Fingerprint is a sequence of bytes used to authenticate the
   public key before using the same to authenticate the peer in the
   context of KMP.

   Various forms of the fingerprint mechanism based on the public keys
   are already in use as defined in [RFC4252] and [RFC4253].
   Fingerprints are also used primarily for root key authentication in
   x.509 based PKI [RFC5280].  This documents only highlights the usage
   of raw public key based authentication mechanism already defined in
   [RFC5996] for KARP deployments.

   To generate a fingerprint:

   1.  A router needs to generate an asymmetric Private/Public key pair.
       Asymmetric crypto algorithms based on RSA [RFC3447] or for
       shorter and still secure keys Elliptic Curve Cryptography (ECC)
       [RFC4492] can be used for generating the Private/Public key pair.

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   2.  Once the Asymmetric key pair is generated, the public key can be
       encoded with any additional data (specific to the router) and can
       be in the form of more easily administrable X.509 PKI Certificate
       profile and to be specific as specified in the
       SubjectPublicKeyInfo structure in Section 4.1 of [RFC5280].  This
       does not force use of X.509 or full compliance with [RFC5280]
       since formatting any public key as a SubjectPublicKeyInfo is
       relatively straightforward and well supported by libraries.

   3.  The result should be hashed with a cryptographic hash function,
       preferably SHA-256 or hash functions with similar strength (see
       more discussion on choosing preferred hash function in
       Section 8).

   The fingerprint generated is not a secret and can be distributed
   publicly.  This is further discussed in Section 4.

3.  Usage of Router Fingerprints with KARP KMP

   To use Router Fingerprints authentication with KARP KMP, a Private/
   Public key-pair MUST be generated by the router as specified in
   Section 2.  Base IKEv2 [RFC5996] standard supports only raw RSA based
   public keys.  The type of the public keys and encoding has to be more
   generic to deploy this peer authentication method.

   With current specification [RFC5996] when sender needs to get the
   certificate of the receiver, Certificate Request payload (CERTREQ as
   specified in [RFC5996]) is sent with cert encoding set to "Raw RSA
   Key" and Certification Authority field is empty.  The receiver of
   this CERTREQ payload, (currently) uses PKCS #1 encoding for the
   generated RSA Public Key and sends the same in CERT payload as
   Certificate Data with Certificate Encoding set to "Raw RSA Key" as
   described in Section 3.6 of IKEv2 [RFC5996].  Once the public key of
   the sender is received, the verification MUST be done with the
   already published/stored fingerprints of the sender.

   As noted above the current IKEv2[RFC5996] specification only supports
   raw RSA public keys.  [I-D.kivinen-ipsecme-oob-pubkey] enhances
   support for other types of public keys and also defines new encoding
   format to carry the public key fingerprint in the CERT payload.  For
   RPs to use Router Fingerprint Authentication in the context of IKEv2
   MUST follow the encoding format as specified in [I-D.kivinen-ipsecme-

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3.1.  Impact on the PAD

   The Peer Authorization Database (PAD) and the role it plays in peer
   authentication is defined in section 4.4.3 of [RFC4301].  One of the
   functions of the PAD is to provide the authentication data for each
   peer.  [RFC4301] supports X.509 certificate or pre-shared secret
   authentication data types.  So, it is necessary (and one more reason)
   to encode the raw public keys as X.509 certificates before sending
   the same in CERT payload.  Though the public key received is in the
   form of x.509 certificate, for RFA, the PAD entry need not contain a
   trust anchor via which the end entity (EE) certificate or the public
   key for the peer must be verifiable.  The PAD entry MUST rather
   contain the published fingerprint of the peer.

4.  Publishing Router Fingerprints

   The router fingerprint generated is not a secret and can be exchanged
   out-of-band or can be distributed publicly.  Please refer to
   Section 5 for the generic usage and scope of the RFA in routing
   environments.  In the case of inter-domain routing using EBGP
   [RFC4271] and if the routers are outside of the SIDR [I-D.ietf-sidr-
   bgpsec-overview] environment, fingerprint can also be exchanged out-
   of-band through Service Level Agreements (SLAs) at the RP peering
   points.  A KARP KMP deployment using router fingerprints need to
   resort to out-of-band public key validation procedure to verify
   authenticity of the keys being used.  The router fingerprints should
   be part of the KMP PAD to validate the public key received in the KMP
   messages.  For conveying router fingerprints data bytes in a clear
   unambiguous way PGP (Pretty Good Privacy) wordlists can be used.

5.  Scope of Fingerprints usage with RPs

   The fingerprint method described in this document in general is more
   suitable for intra domain deployments.  This includes KMP usage for
   E.g., for IBGP [RFC4271] and LDP [RFC5036] peers, where KARP KMP can
   be deployed with out having to configure either manual pre-shared
   keys to bootstrap KMP or full PKI with trust anchor certificates.
   This method also can be potentially used between EBGP [RFC4271]
   speakers outside of the SIDR ([I-D.ietf-sidr-bgpsec-overview])
   deployment scope, where full PKI infrastructure is not available to
   deploy with KARP KMP and at the same time, still operators want to
   avoid provisioning manual keys.

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6.  Fingerprint Revocation

   The idea of RFA in the context of KARP KMP is to deploy a better
   authentication mechanism than the mutually shared symmetric keys
   between two routers.  This SHOULD be used especially where number of
   peers using this method is relatively smaller and operationally
   manageable.  Any changes in the router fingerprints SHOULD be
   administered manually by the operator.

   When there are a large number of peers, the need for router
   fingerprint changes may increase.  This may be for reasons of key
   compromises or other potential changes to the routers.  In such
   environments, operators SHOULD look to full PKI with trust anchor
   certificates and CRL profiles as specified in the [RFC5280].  In this
   context, RFA mechanism should be only seen as substantial improvement
   from mutually shared manual keying authentication methods.

7.  IANA Considerations

   This document defines no new namespaces.

8.  Security Considerations

   If collision attacks are perceived as a threat, the hash function to
   generate the fingerprints SHOULD also possess the property of
   collision-resistance.  To mitigate preimage attacks, the
   cryptographic hash function used for a fingerprint SHOULD possess the
   property of second preimage resistance.

   If generated fingerprints are truncated to make those short, the
   truncated fingerprints MUST be long enough to preserve the relevant
   properties of the hash function against brute-force search attacks.

   Considering the above facts, it's recommended to use SHA-256 or
   similar hash functions with good security properties to generate the

9.  Acknowledgements

   The authors would like to thank Jari Arkko for initial and valuable
   discussions on operationally simplified authentication mechanisms in
   general and RFA mechanism as described in this document in
   particular.  Authors would like to acknowledge Joel Halpern for
   supporting this work and providing continuous feedback on the draft,
   including the usefulness of this approach in routing environments.

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   Thanks to Tero Kivinen for extended discussions on applicability and
   usage of authentication method described for KARP KMP.

10.  References

10.1.  Normative References

              Chunduri, U., Tian, A., and J. Touch, "Using IKEv2 with
              TCP-AO", draft-chunduri-karp-using-ikev2-with-tcp-ao-01
              (work in progress), March 2012.

              Kivinen, T., Wouters, P., and H. Tschofenig, "More Raw
              Public Keys for IKEv2",
              draft-kivinen-ipsecme-oob-pubkey-00 (work in progress),
              March 2012.

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

   [RFC5996]  Kaufman, C., Hoffman, P., Nir, Y., and P. Eronen,
              "Internet Key Exchange Protocol Version 2 (IKEv2)",
              RFC 5996, September 2010.

10.2.  Informative References

              Lebovitz, G. and M. Bhatia, "Keying and Authentication for
              Routing Protocols (KARP) Overview, Threats, and
              Requirements", draft-ietf-karp-threats-reqs-05 (work in
              progress), May 2012.

              Lepinski, M. and S. Turner, "An Overview of BGPSEC",
              draft-ietf-sidr-bgpsec-overview-02 (work in progress),
              May 2012.

   [RFC3447]  Jonsson, J. and B. Kaliski, "Public-Key Cryptography
              Standards (PKCS) #1: RSA Cryptography Specifications
              Version 2.1", RFC 3447, February 2003.

   [RFC3618]  Fenner, B. and D. Meyer, "Multicast Source Discovery
              Protocol (MSDP)", RFC 3618, October 2003.

   [RFC4107]  Bellovin, S. and R. Housley, "Guidelines for Cryptographic
              Key Management", BCP 107, RFC 4107, June 2005.

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   [RFC4252]  Ylonen, T. and C. Lonvick, "The Secure Shell (SSH)
              Authentication Protocol", RFC 4252, January 2006.

   [RFC4253]  Ylonen, T. and C. Lonvick, "The Secure Shell (SSH)
              Transport Layer Protocol", RFC 4253, January 2006.

   [RFC4271]  Rekhter, Y., Li, T., and S. Hares, "A Border Gateway
              Protocol 4 (BGP-4)", RFC 4271, January 2006.

   [RFC4301]  Kent, S. and K. Seo, "Security Architecture for the
              Internet Protocol", RFC 4301, December 2005.

   [RFC4492]  Blake-Wilson, S., Bolyard, N., Gupta, V., Hawk, C., and B.
              Moeller, "Elliptic Curve Cryptography (ECC) Cipher Suites
              for Transport Layer Security (TLS)", RFC 4492, May 2006.

   [RFC5036]  Andersson, L., Minei, I., and B. Thomas, "LDP
              Specification", RFC 5036, October 2007.

   [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.

   [RFC5440]  Vasseur, JP. and JL. Le Roux, "Path Computation Element
              (PCE) Communication Protocol (PCEP)", RFC 5440,
              March 2009.

   [RFC6518]  Lebovitz, G. and M. Bhatia, "Keying and Authentication for
              Routing Protocols (KARP) Design Guidelines", RFC 6518,
              February 2012.

Authors' Addresses

   Uma Chunduri
   Ericsson Inc.
   300 Holger Way
   San Jose, California  95134

   Phone: +1 (408) 750-5678
   Email: uma.chunduri@ericsson.com

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   Albert Tian
   Ericsson Inc.
   300 Holger Way
   San Jose, California  95134

   Phone: +1 (408) 750-5210
   Email: albert.tian@ericsson.com

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