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Versions: 00                                                            
Path Computation Element                                        D. Lopez
Internet-Draft                                       O. Gonzalez de Dios
Intended status: Standards Track                          Telefonica I+D
Expires: January 11, 2014                                  July 10, 2013

                       Secure Transport for PCEP


   The Path Computation Element Communication Protocol (PCEP) defines
   the mechanisms for the communication between a client and a PCE, or
   among PCEs.  This document describe the usage of Transport Layer
   Security to enhance PCEP security, hence the PCEPS acronym proposed
   for it.  The additional security mechanisms are provided by the
   transport protocol supporting PCEP, and therefore they do not affect
   its flexibility and extensibility.

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
   working documents as Internet-Drafts.  The list of current Internet-
   Drafts is at http://datatracker.ietf.org/drafts/current/.

   Internet-Drafts are draft documents valid for a maximum of six months
   and may be updated, replaced, or obsoleted by other documents at any
   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 January 11, 2014.

Copyright Notice

   Copyright (c) 2013 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

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   the Trust Legal Provisions and are provided without warranty as
   described in the Simplified BSD License.

Table of Contents

   1.  Introduction  . . . . . . . . . . . . . . . . . . . . . . . . . 3
   2.  Applying TLS to PCEP  . . . . . . . . . . . . . . . . . . . . . 3
     2.1.  TCP ports . . . . . . . . . . . . . . . . . . . . . . . . . 3
     2.2.  Connection Establishment  . . . . . . . . . . . . . . . . . 4
     2.3.  Peer Identity . . . . . . . . . . . . . . . . . . . . . . . 5
   3.  IANA Considerations . . . . . . . . . . . . . . . . . . . . . . 6
   4.  Security Considerations . . . . . . . . . . . . . . . . . . . . 6
   5.  Acknowledgements  . . . . . . . . . . . . . . . . . . . . . . . 7
   6.  References  . . . . . . . . . . . . . . . . . . . . . . . . . . 7
     6.1.  Normative References  . . . . . . . . . . . . . . . . . . . 7
     6.2.  Informative References  . . . . . . . . . . . . . . . . . . 8
   Authors' Addresses  . . . . . . . . . . . . . . . . . . . . . . . . 8

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1.  Introduction

   PCEP [RFC5440] defines the mechanisms for the communication between a
   Path Computation Client (PCC) and a Path Computation Element (PCE),
   or between two PCEs.  These interactions include requests and replies
   that can be critical for a sustainable network operation and adequate
   resource allocation, and therefore appropriate security becomes a key
   element in the PCE infrastructure.  As the appplications of the PCE
   framework evolves, and more complex service patterns emerge, the
   definition of a secure mode of operation becomes more relevant.

   [RFC5440] analyzes in its section on security considerations the
   potential threats to PCEP and their consequences, and discusses
   several mechanisms for protecting PCEP against security attacks,
   without making a specific recommendation on a particular one or
   defining their application in depth.  Moreover, [RFC6952] remarks the
   importance of ensuring PCEP communication privacy, especially when
   PCEP communication endpoints do not reside in the same AS, as the
   interception of PCEP messages could leak sensitive information
   related to computed paths and resources.

   Among the possible solutions mentioned in these documents, Transport
   Layer Security (TLS) [RFC5246] provides support for peer
   authentication, and message encryption and integrity.  TLS supports
   the usage of well-know mechanisms to support key configuration and
   exchange, and means to perform security checks on the results of PCE
   discovery procedures ([RFC5088] and [RFC5089]).  Since TLS is a
   security container for the transport of PCEP requests and replies, it
   will not interfere with the protocol flexibility and extensibility.

   This document describes how to apply TLS in securing PCE
   interactions, including the handshake mechanisms, the methods for
   peer authentication, and the applicable TLS ciphersuites for data
   exchange.  In the rest of the document we will refer to this usage of
   TLS as transport for PCEP as either "PCEP over TLS" or "PCEPS".

2.  Applying TLS to PCEP

2.1.  TCP ports

   The default destination port number for PCEP over TLS is TCP/XXXX.

   NOTE: This port has to be agreed and registered as PCEPS with IANA.

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2.2.  Connection Establishment

   PCEPS has no notion of negotiating TLS in an established connection.
   Both peers in the connection need to be preconfigured to use PCEPS
   for a given endpoint.  The connection establishment SHALL follow the
   following steps:

   1.  After completing the TCP handshake, immediately negotiate TLS
       sessions according to [RFC5246].  The following restrictions

       *  Support for TLS v1.2 [RFC5246] or later is REQUIRED.

       *  Support for certificate-based mutual authentication is

       *  Negotiation of mutual authentication is REQUIRED.

       *  Negotiation of a ciphersuite providing for integrity
          protection is REQUIRED.

       *  Negotiation of a ciphersuite providing for confidentiality is

       *  Support for and negotiation of compression is OPTIONAL.

       *  PCEPS implementations MUST, at a minimum, support negotiation
          of the TLS_RSA_WITH_3DES_EDE_CBC_SHA, and SHOULD support
          TLS_RSA_WITH_RC4_128_SHA and TLS_RSA_WITH_AES_128_CBC_SHA as
          well.  In addition, PCEPS implementations MUST support
          negotiation of the mandatory-to-implement ciphersuites
          required by the versions of TLS that they support.

   2.  Peer authentication can be performed in any of the following two
       REQUIRED operation models:

       *  TLS with X.509 certificates using PKIX trust models:

          +  Implementations MUST allow the configuration of a list of
             trusted Certification Authorities for incoming connections.

          +  Certificate validation MUST include the verification rules
             as per [RFC5280].

          +  Implementations SHOULD indicate their trusted Certification
             Authorities (CAs).  For TLS 1.2, this is done using
             [RFC5246], Section 7.4.4, "certificate_authorities" (server
             side) and [RFC6066], Section 6 "Trusted CA Indication"

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             (client side).

          +  Peer validation always SHOULD include a check on whether
             the locally configured expected DNS name or IP address of
             the server that is contacted matches its presented
             certificate.  DNS names and IP addresses can be contained
             in the Common Name (CN) or subjectAltName entries.  For
             verification, only one of these entries is to be
             considered.  The following precedence applies: for DNS name
             validation, subjectAltName:DNS has precedence over CN; for
             IP address validation, subjectAltName:iPAddr has precedence
             over CN.

          +  NOTE: Consider here whether peer validation MAY be extended
             by means of the DANE procedures, including its specs as
             informative references.

          +  Implementations MAY allow the configuration of a set of
             additional properties of the certificate to check for a
             peer's authorization to communicate (e.g., a set of allowed
             values in subjectAltName:URI or a set of allowed X509v3
             Certificate Policies)

       *  TLS with X.509 certificates using certificate fingerprints:
          Implementations MUST allow the configuration of a list of
          trusted certificates, identified via fingerprint of the DER
          encoded certificate octets.  Implementations MUST support SHA-
          256 as the hash algorithm for the fingerprint.

   3.  Start exchanging PCEP requests and replies.

   NOTE: TLS re-negotiation left as an open issue.

2.3.  Peer Identity

   Depending on the peer authentication method in use, PCEPS supports
   different operation modes to establish peer's identity and whether it
   is entitled to perform requests or can be considered authoritative in
   its replies.  PCEPS implementations SHOULD provide mechanisms for
   associating peer identities with different levels of access and/or
   authoritativeness, and they MUST provide a mechanism for establish a
   default level for properly identified peers.  Any connection
   established with a peer that cannot be properly identified SHALL be
   terminated before any PCEP exchange takes place.

   In TLS-X.509 mode using fingerprints, a peer is uniquely identified
   by the fingerprint of the presented client certificate.

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   There are numerous trust models in PKIX environments, and it is
   beyond the scope of this document to define how a particular
   deployment determines whether a client is trustworthy.
   Implementations that want to support a wide variety of trust models
   should expose as many details of the presented certificate to the
   administrator as possible so that the trust model can be implemented
   by the administrator.  As a suggestion, at least the following
   parameters of the X.509 client certificate should be exposed:

   o  Peer's IP address

   o  Peer's FQDN

   o  Certificate Fingerprint

   o  Issuer

   o  Subject

   o  All X509v3 Extended Key Usage

   o  All X509v3 Subject Alternative Name

   o  All X509v3 Certificate Policies

   NOTE: Additional procedures enabled by DANE methods are TBD

   NOTE: Specific connections with PCE discovery procedures is TBD

3.  IANA Considerations

   NOTE: PCEPS has to be registered as TCP port XXXX.

   No new PCEP messages or other objects are defined.

4.  Security Considerations

   Since computational resources required by TLS handshake and
   ciphersuite are higher than unencrypted TCP, clients connecting to a
   PCEPS server can more easily create high load conditions and a
   malicious client might create a Denial-of-Service attack more easily.

   Some TLS ciphersuites only provide integrity validation of their
   payload, and provide no encryption.  This specification does not
   forbid the use of such ciphersuites, but administrators must weight
   carefully the risk of relevant internal data leakage that can occur

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   in such a case, as explicitly stated by [RFC6952].

   When using certificate fingerprints to identify PCEPS peers, any two
   certificates that produce the same hash value will be considered the
   same peer.  Therefore, it is important to make sure that the hash
   function used is cryptographically uncompromised so that attackers
   are very unlikely to be able to produce a hash collision with a
   certificate of their choice.  This document mandates support for SHA-
   256, but a later revision may demand support for stronger functions
   if suitable attacks on it are known.

5.  Acknowledgements

   This specification relies on the analysis and profiling of TLS
   included in [RFC6614].

6.  References

6.1.  Normative References

   [RFC5088]  Le Roux, JL., Vasseur, JP., Ikejiri, Y., and R. Zhang,
              "OSPF Protocol Extensions for Path Computation Element
              (PCE) Discovery", RFC 5088, January 2008.

   [RFC5089]  Le Roux, JL., Vasseur, JP., Ikejiri, Y., and R. Zhang,
              "IS-IS Protocol Extensions for Path Computation Element
              (PCE) Discovery", RFC 5089, January 2008.

   [RFC5246]  Dierks, T. and E. Rescorla, "The Transport Layer Security
              (TLS) Protocol Version 1.2", RFC 5246, August 2008.

   [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.

   [RFC6066]  Eastlake, D., "Transport Layer Security (TLS) Extensions:
              Extension Definitions", RFC 6066, January 2011.

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6.2.  Informative References

   [RFC6614]  Winter, S., McCauley, M., Venaas, S., and K. Wierenga,
              "Transport Layer Security (TLS) Encryption for RADIUS",
              RFC 6614, May 2012.

   [RFC6952]  Jethanandani, M., Patel, K., and L. Zheng, "Analysis of
              BGP, LDP, PCEP, and MSDP Issues According to the Keying
              and Authentication for Routing Protocols (KARP) Design
              Guide", RFC 6952, May 2013.

Authors' Addresses

   Diego R. Lopez
   Telefonica I+D
   Don Ramon de la Cruz, 82
   Madrid,   28006

   Phone: +34 913 129 041
   Email: diego@tid.es

   Oscar Gonzalez de Dios
   Telefonica I+D
   Don Ramon de la Cruz, 82
   Madrid,   28006

   Phone: +34 913 129 041
   Email: ogondio@tid.es

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