NETCONF Working Group Mohamad Badra
Internet Draft LIMOS Laboratory
Intended status: Standards Track October 22, 2008
Expires: April 2009
NETCONF over Transport Layer Security (TLS)
draft-ietf-netconf-tls-06.txt
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Copyright Notice
Copyright (C) The IETF Trust (2008).
Abstract
The Network Configuration Protocol (NETCONF) provides mechanisms to
install, manipulate, and delete the configuration of network devices.
This document describes how to use the Transport Layer Security (TLS)
protocol to secure NETCONF exchanges.
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Table of Contents
1. Introduction...................................................3
1.1. Conventions used in this document.........................3
2. NETCONF over TLS...............................................3
2.1. Connection Initiation.....................................3
2.2. Connection Closure........................................4
3. Endpoint Authentication and Identification.....................5
3.1. Server Identity...........................................5
3.2. Client Identity...........................................6
4. Security Considerations........................................6
5. IANA Considerations............................................6
6. Acknowledgments................................................7
7. References.....................................................7
7.1. Normative References......................................7
Author's Addresses................................................8
Intellectual Property and Copyright Statement.....................8
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1. Introduction
The NETCONF protocol [RFC4741] defines a mechanism through which a
network device can be managed. NETCONF is connection-oriented,
requiring a persistent connection between peers. This connection
must provide reliable, sequenced data delivery, integrity and
confidentiality and peers authentication.
This document defines "NETCONF over TLS", which includes support for
certificate-based mutual authentication and key derivation, utilizing
the protected ciphersuite negotiation, mutual authentication and key
management capabilities of the TLS (Transport Layer Security)
protocol, described in [RFC5246].
Throughout this document, the terms "client" and "server" are used to
refer to the two ends of the TLS connection. The client actively
opens the TLS connection, and the server passively listens for the
incoming TLS connection. The terms "manager" and "agent" are used to
refer to the two ends of the NETCONF protocol session. The manager
issues NETCONF remote procedure call (RPC) commands, and the agent
replies to those commands. When NETCONF is run over TLS using the
mapping defined in this document, the client is always the manager,
and the server is always the agent.
1.1. Conventions used in this document
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 [RFC2119].
2. NETCONF over TLS
Since TLS is application protocol-independent, NETCONF can operate on
top of the TLS protocol transparently. This document defines how
NETCONF can be used within a TLS session.
2.1. Connection Initiation
The peer acting as the NETCONF manager MUST also act as the TLS
client. It MUST connect to the server that passively listens for the
incoming TLS connection on the TCP port <IANA-to-be-assigned>. (Note
to RFC Editor: please replace <IANA-to-be-assigned> with the IANA-
assigned value, and remove this note). It MUST therefore send the
TLS ClientHello to begin the TLS handshake. Once the TLS handshake
has finished, the client and the server MAY begin to exchange NETCONF
data. In particular, the client will send complete XML documents to
the server containing <rpc> elements, and the server will respond
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with complete XML documents containing <rpc-reply> elements. The
client MAY indicate interest in receiving event notifications from a
server by creating a subscription to receive event notifications
[RFC5277], in which case the server replies to indicate whether the
subscription request was successful and, if it was successful, begins
sending the event notifications to the client as the events occur
within the system.
All NETCONF messages MUST be sent as TLS "application data". It is
possible that multiple NETCONF messages be contained in one TLS
record, or that a NETCONF message be transferred in multiple TLS
records.
Current NETCONF messages don't include a message's length. This
document uses consequently the same delimiter sequence defined in
[RFC4742] and therefore the special character sequence, ]]>]]>, to
delimit XML documents.
Implementation of the protocol specified in this document MAY
implement any TLS cipher suite that provides certificate-based mutual
authentication [RFC5246].
Implementations MUST support TLS 1.2 [RFC5246] and are REQUIRED to
support the mandatory to implement cipher suite, which is
TLS_RSA_WITH_AES_128_CBC_SHA. This document is assumed to apply to
future versions of TLS, in which case the mandatory to implement
cipher suite for the implemented version MUST be supported.
2.2. Connection Closure
A TLS client (NETCONF manager) MUST close the associated TLS
connection if the connection is not expected to issues any NETCONF
RPC commands later. It MUST send a TLS close_notify alert before
closing the connection. The TLS client MAY choose to not wait for
the TLS server (NETCONF agent) close_notify alert and simply close
the connection, thus generating an incomplete close on the TLS server
side. Once the TLS server gets a close_notify from the TLS client,
it MUST reply with a close_notify unless it becomes aware that the
connection has already been closed by the TLS client (e.g., the
closure was indicated by TCP).
When no data is received from a connection for a long time (where the
application decides what "long" means), a NETCONF peer MAY close the
connection. The NETCONF peer MUST attempt to initiate an exchange of
close_notify alerts with the other NETCONF peer before closing the
connection. The close_notify's sender that is unprepared to receive
any more data MAY close the connection after sending the close_notify
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alert, thus generating an incomplete close on the close_notify's
receiver side.
3. Endpoint Authentication and Identification
3.1. Server Identity
During the TLS negotiation, the client MUST carefully examine the
certificate presented by the server to determine if it meets their
expectations. Particularly, the client MUST check its understanding
of the server hostname against the server's identity as presented in
the server Certificate message, in order to prevent man-in-the-middle
attacks.
Matching is performed according to the rules below (following the
example of [RFC4642]):
- The client MUST use the server hostname it used to open the
connection (or the hostname specified in TLS "server_name"
extension [RFC4366]) as the value to compare against the server
name as expressed in the server certificate. The client MUST
NOT use any form of the server hostname derived from an
insecure remote source (e.g., insecure DNS lookup). CNAME
canonicalization is not done.
- If a subjectAltName extension of type dNSName is present in the
certificate, it MUST be used as the source of the server's
identity.
- Matching is case-insensitive.
- A "*" wildcard character MAY be used as the leftmost name
component in the certificate. For example, *.example.com would
match a.example.com, foo.example.com, etc., but would not match
example.com.
- If the certificate contains multiple names (e.g., more than one
dNSName field), then a match with any one of the fields is
considered acceptable.
If the match fails, the client MUST either ask for explicit user
confirmation or terminate the connection and indicate the server's
identity is suspect.
Additionally, clients MUST verify the binding between the identity of
the servers to which they connect and the public keys presented by
those servers. Clients SHOULD implement the algorithm in Section 6
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of [RFC5280] for general certificate validation, but MAY supplement
that algorithm with other validation methods that achieve equivalent
levels of verification (such as comparing the server certificate
against a local store of already-verified certificates and identity
bindings).
If the client has external information as to the expected identity of
the server, the hostname check MAY be omitted.
3.2. Client Identity
Typically, the server has no external knowledge of what the client's
identity ought to be and so checks (other than that the client has a
certificate chain rooted in an appropriate CA) are not possible. If
a server has such knowledge (typically from some source external to
NETCONF or TLS) it MUST check the identity as described above.
4. Security Considerations
The security considerations described throughout [RFC5246] apply here
as well.
This document in its current version doesn't support third party
authentication due to the fact that TLS doesn't specify this way of
authentication and that NETCONF depends on the transport protocol for
the authentication service. If third party authentication is needed,
BEEP or SSH transport can be used.
5. IANA Considerations
IANA is requested to assign a TCP port number in the "Registered Port
Numbers" range with the name "netconf-tls". This port will be the
default port for NETCONF over TLS, as defined in this document.
Registration Contact: Mohamad Badra, badra@isima.fr.
Transport Protocol: TCP.
Port Number: TBA-by-IANA (if possible, please assign 6513).
Broadcast, Multicast or Anycast: No.
Port Name: netconf-tls.
Service Name: netconf.
Reference: draft-ietf-netconf-tls-05.
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6. Acknowledgments
A significant amount of the text in Section 3 was lifted from
[RFC4642].
The author would like to acknowledge David Harrington, Miao Fuyou,
Eric Rescorla, Juergen Schoenwaelder, Simon Josefsson, Olivier
Coupelon, Alfred Hoenes and the NETCONF mailing list members for
their comments on the document. The author appreciates also Bert
Wijnen, Mehmet Ersue and Dan Romascanu for their efforts on issues
resolving discussion, and Charlie Kaufman, Pasi Eronen and Tim Polk
for the thorough review of this document.
7. References
7.1. Normative References
[RFC2119] Bradner, S., "Key words for use in RFCs to Indicate
Requirement Levels", BCP 14, RFC 2119, March 1997.
[RFC4366] Blake-Wilson, S., Nystrom, M., Hopwood, D., Mikkelsen, J.,
and T. Wright, "Transport Layer Security (TLS) Extensions",
RFC 4366, April 2006.
[RFC4642] Murchison, K., Vinocur, J., Newman, C., "Using Transport
Layer Security (TLS) with Network News Transfer Protocol
(NNTP)", RFC 4642, October 2006
[RFC4741] Enns, R., "NETCONF Configuration Protocol", RFC 4741,
December 2006.
[RFC4742] Wasserman, M. and T. Goddard, "Using the NETCONF
Configuration Protocol over Secure Shell (SSH)", RFC 4742,
December 2006.
[RFC5246] Dierks, T. and E. Rescorla, "The Transport Layer Security
(TLS) Protocol 1.2", RFC5246, August 2008.
[RFC5277] Chisholm, S. and H. Trevino, "NETCONF Event Notifications",
RFC 5277, July 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.
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Author's Addresses
Mohamad Badra
LIMOS Laboratory - UMR6158, CNRS
France
Email: badra@isima.fr
Contributors
Ibrahim Hajjeh
INEOVATION
France
Email: Ibrahim.hajjeh@ineovation.com
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