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Using the NETCONF Protocol over Transport Layer Security (TLS) with Mutual X.509 Authentication

The information below is for an old version of the document that is already published as an RFC.
Document Type
This is an older version of an Internet-Draft that was ultimately published as RFC 7589.
Authors Mohamad Badra , Alan Luchuk , Jürgen Schönwälder
Last updated 2015-10-14 (Latest revision 2015-04-10)
Replaces draft-badra-netconf-rfc5539bis
RFC stream Internet Engineering Task Force (IETF)
Intended RFC status Proposed Standard
Additional resources Mailing list discussion
Stream WG state Submitted to IESG for Publication
Document shepherd Mehmet Ersue
Shepherd write-up Show Last changed 2015-02-19
IESG IESG state Became RFC 7589 (Proposed Standard)
Action Holders
Consensus boilerplate Yes
Telechat date (None)
Responsible AD Benoît Claise
Send notices to (None)
IANA IANA review state Version Changed - Review Needed
IANA action state RFC-Ed-Ack
NETCONF Working Group                                           M. Badra
Internet-Draft                                          Zayed University
Obsoletes: 5539 (if approved)                                  A. Luchuk
Intended status: Standards Track                     SNMP Research, Inc.
Expires: October 12, 2015                               J. Schoenwaelder
                                                Jacobs University Bremen
                                                          April 10, 2015

  Using the NETCONF Protocol over Transport Layer Security (TLS) with
                      Mutual X.509 Authentication


   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 with mutual X.509 authentication to secure the exchange of
   NETCONF messages.  This revision of RFC 5539 documents the new
   message framing used by NETCONF 1.1 and it obsoletes RFC 5539.

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

   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 October 12, 2015.

Copyright Notice

   Copyright (c) 2015 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
   ( in effect on the date of
   publication of this document.  Please review these documents

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

Table of Contents

   1.  Introduction  . . . . . . . . . . . . . . . . . . . . . . . .   2
   2.  Connection Initiation . . . . . . . . . . . . . . . . . . . .   3
   3.  Message Framing . . . . . . . . . . . . . . . . . . . . . . .   3
   4.  Connection Closure  . . . . . . . . . . . . . . . . . . . . .   3
   5.  Certificate Validation  . . . . . . . . . . . . . . . . . . .   3
   6.  Server Identity . . . . . . . . . . . . . . . . . . . . . . .   4
   7.  Client Identity . . . . . . . . . . . . . . . . . . . . . . .   4
   8.  Cipher Suites . . . . . . . . . . . . . . . . . . . . . . . .   6
   9.  Security Considerations . . . . . . . . . . . . . . . . . . .   6
   10. IANA Considerations . . . . . . . . . . . . . . . . . . . . .   7
   11. Acknowledgements  . . . . . . . . . . . . . . . . . . . . . .   7
   12. References  . . . . . . . . . . . . . . . . . . . . . . . . .   8
     12.1.  Normative References . . . . . . . . . . . . . . . . . .   8
     12.2.  Informative References . . . . . . . . . . . . . . . . .   8
   Appendix A.  Changes from RFC 5539  . . . . . . . . . . . . . . .   9
   Authors' Addresses  . . . . . . . . . . . . . . . . . . . . . . .   9

1.  Introduction

   The NETCONF protocol [RFC6241] 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 integrity, confidentiality, peer authentication, and
   reliable, sequenced data delivery.

   This document defines how NETCONF messages can be exchanged over
   Transport Layer Security (TLS) [RFC5246].  Implementations MUST
   support mutual TLS certificate-based authentication [RFC5246].  This
   assures the NETCONF server of the identity of the principal who
   wishes to manipulate the management information.  It also assures the
   NETCONF client of the identity of the server for which it wishes to
   manipulate the management information.

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

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2.  Connection Initiation

   The peer acting as the NETCONF client MUST act as the TLS client.
   The TLS client actively opens the TLS connection and the TLS server
   passively listens for the incoming TLS connections.  The well-known
   TCP port number 6513 is used by NETCONF servers to listen for TCP
   connections established by NETCONF over TLS clients.  The TLS client
   MUST send the TLS ClientHello message to begin the TLS handshake.
   The TLS server MUST send a CertificateRequest in order to request a
   certificate from the TLS client.  Once the TLS handshake has
   finished, the client and the server MAY begin to exchange NETCONF
   messages.  Client and server identity verification is done before the
   NETCONF <hello> message is sent.  This means that the identity
   verification is completed before the NETCONF session is started.

3.  Message Framing

   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

   The previous version of this document [RFC5539] used the framing
   sequence defined in [RFC4742].  This version aligns with [RFC6242]
   and adopts the framing protocol defined in [RFC6242] as follows:

   The NETCONF <hello> message MUST be followed by the character
   sequence ]]>]]>.  Upon reception of the <hello> message, the peers
   inspect the announced capabilities.  If the :base:1.1 capability is
   advertised by both peers, the chunked framing mechanism defined in
   Section 4.2 of [RFC6242] is used for the remainder of the NETCONF
   session.  Otherwise, the old end-of-message-based mechanism (see
   Section 4.3 of [RFC6242]) is used.

4.  Connection Closure

   A NETCONF server will process NETCONF messages from the NETCONF
   client in the order in which they are received.  A NETCONF session is
   closed using the <close-session> operation.  When the NETCONF server
   processes a <close-session> operation, the NETCONF server SHALL
   respond and close the TLS session as described in Section 7.2.1 of

5.  Certificate Validation

   Both peers MUST use X.509 certificate path validation [RFC5280] to
   verify the integrity of the certificate presented by the peer.  The
   presented X.509 certificate may also be considered valid if it

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   matches one obtained by another trusted mechanism, such as using a
   locally configured certificate fingerprint.  If X.509 certificate
   path validation fails and the presented X.509 certificate does not
   match a certificate obtained by a trusted mechanism, the connection
   MUST be terminated as defined in [RFC5246].

6.  Server Identity

   The NETCONF client MUST check the identity of the server according to
   Section 6 of [RFC6125].

7.  Client Identity

   The NETCONF server MUST verify the identity of the NETCONF client to
   ensure that the incoming request to establish a NETCONF session is
   legitimate before the NETCONF session is started.

   The NETCONF protocol [RFC6241] requires that the transport protocol's
   authentication process results in an authenticated NETCONF client
   identity whose permissions are known to the server.  The
   authenticated identity of a client is commonly referred to as the
   NETCONF username.  The following algorithm is used by the NETCONF
   server to derive a NETCONF username from a certificate.  (Note that
   the algorithm below is the same as the one described in the SNMP-TLS-
   TM-MIB MIB module defined in [RFC6353] and in the ietf-x509-cert-to-
   name YANG module defined in [RFC7407].)

   (a)  The server maintains an ordered list of mappings of certificates
        to NETCONF usernames.  Each list entry contains

        *  a certificate fingerprint (used for matching the presented

        *  a map type (indicates how the NETCONF username is derived
           from the certificate), and

        *  optional auxiliary data (used to carry a NETCONF username if
           the map type indicates the user name is explicitly

   (b)  The NETCONF username is derived by considering each list entry
        in order.  The fingerprint member of the current list entry
        determines whether the current list entry is a match:

        1.  If the list entry's fingerprint value matches the
            fingerprint of the presented certificate, then consider the
            list entry as a successful match.

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        2.  If the list entry's fingerprint value matches that of a
            locally held copy of a trusted CA certificate, and that CA
            certificate was part of the CA certificate chain to the
            presented certificate, then consider the list entry as a
            successful match.

   (c)  Once a matching list entry has been found, the map type of the
        current list entry is used to determine how the username
        associated with the certificate should be determined.  Possible
        mapping options are:

        A.  The username is taken from the auxiliary data of the current
            list entry.  This means the username is explicitely
            configured (map type 'specified').

        B.  The subjectAltName's rfc822Name field is mapped to the
            username (map type 'san-rfc822-name').  The local part of
            the rfc822Name is used unaltered but the host-part of the
            name must be converted to lowercase.

        C.  The subjectAltName's dNSName is mapped to the username (map
            type 'san-dns-name').  The characters of the dNSName are
            converted to lowercase.

        D.  The subjectAltName's iPAddress is mapped to the username
            (map type 'san-ip-address').  IPv4 addresses are converted
            into decimal-dotted quad notation (e.g., '').  IPv6
            addresses are converted into a 32-character all lowercase
            hexadecimal string without any colon separators.

        E.  Any of the subjectAltName's rfc822Name, dNSName, iPAddress
            is mapped to the username (map type 'san-any').  The first
            matching subjectAltName value found in the certificate of
            the above types MUST be used when deriving the name.

        F.  The certificate's CommonName is mapped to the username (map
            type 'common-name').  The CommonName is converted to UTF-8
            encoding.  The usage of CommonNames is deprecated and users
            are encouraged to use subjectAltName mapping methods

   (d)  If it is impossible to determine a username from the list
        entry's data combined with the data presented in the
        certificate, then additional list entries MUST be searched
        looking for another potential match.  Similarily, if the
        username does not comply to the NETCONF requirements on
        usernames [RFC6241], then additional list entries MUST be

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        searched looking for another potential match.  If there are no
        further list entries, the TLS session MUST be terminated.

   The username provided by the NETCONF over TLS implementation will be
   made available to the NETCONF message layer as the NETCONF username
   without modification.

   The NETCONF server configuration data model
   [I-D.ietf-netconf-server-model] covers NETCONF over TLS and provides
   further details such as certificate fingerprint formats exposed to
   network configuration systems.

8.  Cipher Suites

   Implementations MUST support TLS 1.2 [RFC5246] and are REQUIRED to
   support the mandatory-to-implement cipher suite.  Implementations MAY
   implement additional TLS cipher suites that provide mutual
   authentication [RFC5246] and confidentiality as required by NETCONF
   [RFC6241].  Implementations SHOULD follow the recommendations given
   in [I-D.ietf-uta-tls-bcp].

9.  Security Considerations

   NETCONF is used to access configuration and state information and to
   modify configuration information, so the ability to access this
   protocol should be limited to users and systems that are authorized
   to view the NETCONF server's configuration and state or to modify the
   NETCONF server's configuration.

   Configuration or state data may include sensitive information, such
   as usernames or security keys.  So, NETCONF requires communications
   channels that provide strong encryption for data privacy.  This
   document defines a NETCONF over TLS mapping that provides for support
   of strong encryption and authentication.  The security considerations
   for TLS [RFC5246] and NETCONF [RFC6241] apply here as well.

   NETCONF over TLS requires mutual authentication.  Neither side should
   establish a NETCONF over TLS connection with an unknown, unexpected,
   or incorrect identity on the opposite side.  Note that the decision
   whether a certificate presented by the client is accepted can depend
   on whether a trusted CA certificate is white listed (see Section 7).
   If deployments make use of this option, it is recommended that the
   white listed CA certificate is used only to issue certificates that
   are used for accessing NETCONF servers.  Should the CA certificate be
   used to issue certificates for other purposes, then all certificates
   created for other purposes will be accepted by a NETCONF server as
   well, which is likely not suitable.

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   This document does not support third-party authentication (e.g.,
   backend Authentication, Authorization, and Accounting (AAA) servers)
   due to the fact that TLS does not specify this way of authentication
   and that NETCONF depends on the transport protocol for the
   authentication service.  If third-party authentication is needed, the
   SSH transport [RFC6242] can be used.

   RFC 5539 assumes that the end-of-message (EOM) sequence, ]]>]]>,
   cannot appear in any well-formed XML document, which turned out to be
   mistaken.  The EOM sequence can cause operational problems and open
   space for attacks if sent deliberately in NETCONF messages.  It is
   however believed that the associated threat is not very high.  This
   document still uses the EOM sequence for the initial <hello> message
   to avoid incompatibility with existing implementations.  When both
   peers implement :base:1.1 capability, a proper framing protocol
   (chunked framing mechanism; see Section 3) is used for the rest of
   the NETCONF session, to avoid injection attacks.

10.  IANA Considerations

   Based on the previous version of this document, RFC 5539, IANA has
   assigned a TCP port number (6513) in the "Registered Port Numbers"
   range with the service name "netconf-tls".  This port will be the
   default port for NETCONF over TLS, as defined in Section 2.  Below is
   the registration template following the rules in [RFC6335].

      Service Name:           netconf-tls
      Transport Protocol(s):  TCP
      Assignee:               IESG <>
      Contact:                IETF Chair <>
      Description:            NETCONF over TLS
      Reference:              RFC XXXX
      Port Number:            6513

   [[CREF1: RFC Editor: Please replace XXXX above with the allocated RFC
   number and remove this comment.  --JS]]

11.  Acknowledgements

   The authors like to acknowledge Martin Bjorklund, Olivier Coupelon,
   Mehmet Ersue, Stephen Farrell, Miao Fuyou, Ibrahim Hajjeh, David
   Harrington, Sam Hartman, Alfred Hoenes, Simon Josefsson, Barry Leiba,
   Tom Petch, Eric Rescorla, Dan Romascanu, Kent Watsen, Bert Wijnen,
   Stefan Winter and the NETCONF mailing list members for their comments
   on this document.  Charlie Kaufman, Pasi Eronen, and Tim Polk
   provided a thorough review of previous versions of this document.

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   Juergen Schoenwaelder was partly funded by Flamingo, a Network of
   Excellence project (ICT-318488) supported by the European Commission
   under its Seventh Framework Programme.

12.  References

12.1.  Normative References

              Sheffer, Y., Holz, R., and P. Saint-Andre,
              "Recommendations for Secure Use of TLS and DTLS", draft-
              ietf-uta-tls-bcp-09 (work in progress), February 2015.

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

   [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.

   [RFC6125]  Saint-Andre, P. and J. Hodges, "Representation and
              Verification of Domain-Based Application Service Identity
              within Internet Public Key Infrastructure Using X.509
              (PKIX) Certificates in the Context of Transport Layer
              Security (TLS)", RFC 6125, March 2011.

   [RFC6241]  Enns, R., Bjorklund, M., Schoenwaelder, J., and A.
              Bierman, "Network Configuration Protocol (NETCONF)", RFC
              6241, June 2011.

   [RFC6242]  Wasserman, M., "Using the NETCONF Protocol over Secure
              Shell (SSH)", RFC 6242, June 2011.

   [RFC6335]  Cotton, M., Eggert, L., Touch, J., Westerlund, M., and S.
              Cheshire, "Internet Assigned Numbers Authority (IANA)
              Procedures for the Management of the Service Name and
              Transport Protocol Port Number Registry", BCP 165, RFC
              6335, August 2011.

12.2.  Informative References

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              Watsen, K. and J. Schoenwaelder, "NETCONF Server and
              RESTCONF Server Configuration Models", draft-ietf-netconf-
              server-model-06 (work in progress), February 2015.

   [RFC4742]  Wasserman, M. and T. Goddard, "Using the NETCONF
              Configuration Protocol over Secure SHell (SSH)", RFC 4742,
              December 2006.

   [RFC5539]  Badra, M., "NETCONF over Transport Layer Security (TLS)",
              RFC 5539, May 2009.

   [RFC6353]  Hardaker, W., "Transport Layer Security (TLS) Transport
              Model for the Simple Network Management Protocol (SNMP)",
              STD 78, RFC 6353, July 2011.

   [RFC7407]  Bjorklund, M. and J. Schoenwaelder, "A YANG Data Model for
              SNMP Configuration", RFC 7407, December 2014.

Appendix A.  Changes from RFC 5539

   This section summarizes major changes between this document and RFC

   o  Documented that NETCONF over TLS uses the new message framing if
      both peers support the :base:1.1 capability.

   o  Removed redundant text that can be found in the TLS and NETCONF
      specifications and restructured the text.  Alignment with

   o  Added a high-level description how NETCONF usernames are derived
      from certificates.

   o  Removed the reference to BEEP.

Authors' Addresses

   Mohamad Badra
   Zayed University


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   Alan Luchuk
   SNMP Research, Inc.
   3001 Kimberlin Heights Road
   Knoxville, TN  37920

   Phone: +1 865 573 1434

   Juergen Schoenwaelder
   Jacobs University Bremen
   Campus Ring 1
   28759 Bremen

   Phone: +49 421 200 3587

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