Internet DRAFT - draft-lopez-pcp-pceps
draft-lopez-pcp-pceps
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
draft-lopez-pcp-pceps-00
Abstract
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
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This Internet-Draft will expire on January 11, 2014.
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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
apply:
* Support for TLS v1.2 [RFC5246] or later is REQUIRED.
* Support for certificate-based mutual authentication is
REQUIRED.
* Negotiation of mutual authentication is REQUIRED.
* Negotiation of a ciphersuite providing for integrity
protection is REQUIRED.
* Negotiation of a ciphersuite providing for confidentiality is
RECOMMENDED.
* 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
Spain
Phone: +34 913 129 041
Email: diego@tid.es
Oscar Gonzalez de Dios
Telefonica I+D
Don Ramon de la Cruz, 82
Madrid, 28006
Spain
Phone: +34 913 129 041
Email: ogondio@tid.es
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