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draft-ietf-netconf-tls-04.txt --> draft-ietf-netconf-tls-05.txt

Internet Draft LIMOS Laboratory
Intended status: Standards Track September 2, October 17, 2008
Expires: March April 2009

NETCONF over Transport Layer Security (TLS)
draft-ietf-netconf-tls-04.txt
draft-ietf-netconf-tls-05.txt

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This Internet-Draft will expire on March 2, April 17, 2009.

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 Protocol 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.....................4 Identification.....................5
3.1. Server Identity...........................................5
3.2. Client Identity...........................................6
3.3. Pre-shared key Authentication.............................6
4. Cipher Suite Requirements......................................7
5. Security Considerations........................................7
6. Considerations........................................6
5. IANA Considerations............................................7
7. Considerations............................................6
6. Acknowledgments................................................7
8. References.....................................................8
8.1.
7. References.....................................................7
7.1. Normative References......................................8 References......................................7
Author's Addresses................................................8
Intellectual Property and Copyright Statement.....................8

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1. Introduction

The NETCONF protocol [RFC4741] defines a simple mechanism through which a
network device can be managed. NETCONF is connection-
oriented, connection-oriented,
requiring a persistent connection between peers. This connection
must provide reliable, sequenced data delivery, integrity and
confidentiality and peers authentication.

This document
describes how to use 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 [RFC5246] to secure NETCONF connections. (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 Transport Layer Security (TLS) 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 IANA-to-be-assigned TCP port <TBA>. <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 been finished, the client and the server MAY then send their begin to exchange NETCONF exchanges.
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 NETCONF
server by creating a subscription to receive event notifications
[RFC5277], in which the NETCONF server replies to indicate whether the
subscription request was successful and, if it was successful, begins
sending the event notifications to the NETCONF client as the events occur
within

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All these elements are encapsulated into NETCONF messages MUST be sent as TLS records of
type "application data". These records are protected using the It is
possible that multiple NETCONF messages be contained in one TLS
material keys.
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.

2.2. Connection Closure

Either NETCONF peer MAY stop

Implementation of the NETCONF connection at protocol specified in this document MAY
implement any time and
therefore notify the other NETCONF peer TLS cipher suite that no more data on this
channel will be sent provides certificate-based mutual
authentication [RFC5246].

Implementations MUST support TLS 1.2 [RFC5246] and that any data received after a closure
request will be ignored. are REQUIRED to
support the mandatory to implement cipher suite, which is
TLS_RSA_WITH_AES_128_CBC_SHA. This MAY happen when no data document is received
from a connection assumed to apply to
future versions of TLS, in which case the mandatory to implement
cipher suite for a long time, where the application decides what
"long" means. implemented version MUST be supported.

2.2. Connection Closure

A TLS has client (NETCONF manager) MUST close the ability for secure associated TLS
connection closure using the Alert
protocol. When the NETCONF peer closes if the connection is not expected to issues any NETCONF connection, it
RPC commands later. It MUST send a TLS close_notify alert before
closing the TCP connection.
Any data received after a closure alert is ignored.

Unless a fatal error has occurred, each party is required The TLS client MAY choose to send a not wait for
the TLS server (NETCONF agent) close_notify alert before closing and simply close
the write side of connection, thus generating an incomplete close on the connection
[RFC5246]. The other party TLS server
side. Once the TLS server gets a close_notify from the TLS client,
it MUST respond reply with a close_notify alert of
its own and close down unless it becomes aware that the
connection immediately, discarding any
pending writes. It is not required for has already been closed by the initiator of TLS client (e.g., the close to
wait
closure was indicated by TCP).

When no data is received from a connection for a long time (where the responding close_notify alert before closing the read
side of
application decides what "long" means), a NETCONF peer MAY close the
connection.

3. Endpoint Authentication and Identification The NETCONF requires that its transport provide mutual authentication of
client and server, so cipher suites that are anonymous or which only
authenticate the server to the client peer MUST NOT be used with NETCONF.
This document specifies how attempt to use TLS initiate an exchange of
close_notify alerts with endpoint authentication,
which can be based on either preshared keys [RFC4279] or public key
certificates [RFC5246]. Some cipher suites (e.g.
TLS_RSA_PSK_WITH_AES_128_CBC_SHA) use both. Section 3.1 describes
how the client authenticates the server if public key certificates
are provided by the server, section 3.2 describes how the server
authenticates other NETCONF peer before closing the client if public key certificates are provided by
connection. The close_notify's sender that is unprepared to receive
any more data MAY close the client, and section 3.3 describes how connection after sending the client and server
mutually authenticate one another using a pre-shared key (PSK). 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 these the rules [RFC4642]: 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 left-most 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).

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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.

3.3. Pre-shared key Authentication

[RFC4279] supports authentication based on pre-shared keys (PSKs).
These pre-shared keys are symmetric keys, shared in advance among the
communicating parties.

The PSK can be generated in many ways and its length is variable. It
is RECOMMENDED that implementations that allow the administrator to
manually configure the PSK also provide functionality for generating
a new random PSK, taking [RFC4086] into account.

If both the client and the server agree on using the pre-shared key
authentication, the server can provide a "PSK identity hint" in the
ServerKeyExchange message. If a hint is provided, the
psk_identity_hint is encoded in the same way as in [RFC4279] and
should be a string representation of the name of the server
recognizable to the administrator or his software. In the case where
the user types a server name to connect to, it should be that string.
If the string the user enters differs from the one returned as
psk_identity_hint, the software could display the server's name local store of already-verified certificates and
ask identity
bindings).

If the user client has external information as to confirm. For automated scripts, the names could be expected to match. It is highly recommended that implementations set
the psk_identity_hint to the DNS name identity of
the NETCONF server (i.e.,
the TLS server).

It is RECOMMENDED that users choose different PSKs for server, the different
servers they manage.

[RFC4279] defines some conformance requirements for hostname check MAY be omitted.

3.2. Client Identity

Typically, the PSK, for server has no external knowledge of what the
PSK client's
identity encoding ought to be and for so checks (other than that the identity hint. Moreover, 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
describes the management interface requirements for entering MUST check the PSK
and/or PSK identity (See Section 5 of [RFC4279] for a more detailed
description of these requirements). Those same requirements apply
here as well.

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4. Cipher Suite Requirements

A compliant implementation of the protocol specified in this document
MUST implement the cipher suite TLS_DHE_PSK_WITH_AES_128_CBC_SHA and
MAY implement any TLS cipher suite that provides mutual
authentication.

5. Security Considerations

The security considerations described throughout [RFC5246] and
[RFC4279] 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.

As with all schemes involving shared keys, special care should be
taken to protect the shared secret as well as to limit its exposure
over time. Alternatively, using certificates would provide better
protection.

5. IANA Considerations

IANA is requested to assign a TCP port number that in the "Registered Port
Numbers" range with the name "netconf-tls". This port will be the
default port for NETCONF over TLS sessions TLS, as defined in this document.

IANA has assigned port <TBA> for this purpose.

Registration Contact: Mohamad Badra, badra@isima.fr.
Transport Protocol: TCP.
Port Number: TBA-by-IANA (if possible, please assign 6513).
Broadcast, Multicast or Anycast: Anycast.
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 3.1 3 was lifted from
[RFC4642].

The author would like to acknowledge David Harrington, Miao Fuyou,
Eric Rescorla, Juergen Schoenwaelder, Simon Josefsson, Olivier
Coupelon 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.

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7. References

8.1.

7.1. Normative References

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

[RFC4086] Eastlake, D., 3rd, Schiller, J., and S. Crocker,
"Randomness Requirements for Security", BCP 106, RFC 4086,
June 2005.

[RFC4279] Eronen, P. and H. Tschofenig., "Pre-Shared Key Ciphersuites
for Transport Layer Security (TLS)", RFC 4279, December
2005.

[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: hajjeh@ineovation.com Ibrahim.hajjeh@ineovation.com

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