NETCONF Working Group                                           M. Badra
Internet-Draft                                          Zayed University
Obsoletes: 5539 (if approved)                                  A. Luchuk
Intended status: Standards Track                     SNMP Research, Inc.
Expires: June 11, 2015                                  J. Schoenwaelder
                                                Jacobs University Bremen
                                                        December 8, 2014

  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 June 11, 2015.

Copyright Notice

   Copyright (c) 2014 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  . . . . . . . . . . . . . . . . . . .   4
   6.  Server Identity . . . . . . . . . . . . . . . . . . . . . . .   4
   7.  Client Identity . . . . . . . . . . . . . . . . . . . . . . .   4
   8.  Cipher Suites . . . . . . . . . . . . . . . . . . . . . . . .   5
   9.  Security Considerations . . . . . . . . . . . . . . . . . . .   6
   10. IANA Considerations . . . . . . . . . . . . . . . . . . . . .   6
   11. Acknowledgements  . . . . . . . . . . . . . . . . . . . . . .   7
   12. Contributor's Address . . . . . . . . . . . . . . . . . . . .   7
   13. References  . . . . . . . . . . . . . . . . . . . . . . . . .   7
     13.1.  Normative References . . . . . . . . . . . . . . . . . .   7
     13.2.  Informative References . . . . . . . . . . . . . . . . .   8
   Appendix A.  Changes from RFC 5539  . . . . . . . . . . . . . . .   8
   Appendix B.  Change Log (to be removed by RFC Editor before
                publication) . . . . . . . . . . . . . . . . . . . .   9
     B.1.  draft-ietf-netconf-rfc5539bis-07  . . . . . . . . . . . .   9
     B.2.  draft-ietf-netconf-rfc5539bis-06  . . . . . . . . . . . .   9
     B.3.  draft-ietf-netconf-rfc5539bis-05  . . . . . . . . . . . .   9
     B.4.  draft-ietf-netconf-rfc5539bis-04  . . . . . . . . . . . .   9
     B.5.  draft-ietf-netconf-rfc5539bis-03  . . . . . . . . . . . .   9
     B.6.  draft-ietf-netconf-rfc5539bis-02  . . . . . . . . . . . .  10
     B.7.  draft-ietf-netconf-rfc5539bis-00  . . . . . . . . . . . .  10
   Authors' Addresses  . . . . . . . . . . . . . . . . . . . . . . .  10

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 assures the

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   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].

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.
   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 [RFC5539] of this document used the framing
   sequence defined in [RFC4742], under the assumption that it could not
   be found in well-formed XML documents.  However, this assumption is
   not correct [RFC6242].  In order to solve this problem, this document
   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

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   respond and close the TLS session as described in Section 7.2.1 of

5.  Certificate Validation

   Both peers use X.509 certificate path validation [RFC5280] to verify
   the integrity of the certificate presented by the peer.  presented
   X.509 certificate may also be considered valid if it matches a
   locally configured certificate fingerprint.  If X.509 certificate
   path validation fails and the presented X.509 certificate does not
   match a locally configured certificate fingerprint, the connection
   MUST be terminated as defined in [RFC5246].

6.  Server Identity

   The NETCONF client MUST carefully examine the certificate presented
   by the NETCONF server to determine if it meets the client's
   expectations.  If the NETCONF client has external information as to
   the expected identity of the NETCONF server, the hostname check MAY
   be omitted.  Otherwise, the NETCONF client MUST check its
   understanding of the NETCONF 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 and guidelines defined
   in [RFC6125].  If the match fails, the NETCONF client MUST either ask
   for explicit user confirmation or terminate the connection and
   indicate the NETCONF server's identity is suspect.

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 MUST result 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:

      The server maintains an ordered list of mappings of certificates
      to names.  The username is derived by considering each list entry
      in order.  The fingerprint member of a list entry determines
      whether the list entry is a match:

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

      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.

      Once a matching list entry has been found, the map-type member of
      the list entry is used to determine how the name associated with
      the certificate should be determined.  Possible options are:

      A.  The username is explicitly configured.

      B.  The subjectAltName's rfc822Name is mapped to a username.

      C.  The subjectAltName's dNSName is mapped to a username.

      D.  The subjectAltName's iPAddress is mapped to a username.

      E.  Any of the subjectAltName's rfc822Name, dNSName, iPAddress is
          mapped to a username.

      F.  The certificate's CommonName is mapped to a username.

      If it is impossible to determine a name from the cert-to-name list
      entry's data combined with the data presented in the certificate,
      then additional cert-to-name list entries MUST be searched looking
      for another potential match.

   The username provided by the NETCONF over TLS implementation will be
   made available to the NETCONF message layer as the NETCONF username
   without modification.  If the username does not comply to the NETCONF
   requirements on usernames [RFC6241], i.e., the username is not
   representable in XML, the TLS session MUST be dropped.

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].

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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.  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 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].

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

11.  Acknowledgements

   The authors like to acknowledge Martin Bjorklund, Olivier Coupelon,
   Mehmet Ersue, Miao Fuyou, David Harrington, Alfred Hoenes, Simon
   Josefsson, Tom Petch, Eric Rescorla, Dan Romascanu, Kent Watsen, Bert
   Wijnen 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.

   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.  Contributor's Address

   Ibrahim Hajjeh


13.  References

13.1.  Normative References

              Sheffer, Y., Holz, R., and P. Saint-Andre,
              "Recommendations for Secure Use of TLS and DTLS", draft-
              ietf-uta-tls-bcp-07 (work in progress), November 2014.

   [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.

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   [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.

13.2.  Informative References

   [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.

Appendix A.  Changes from RFC 5539

   This section lists major changes between this document and RFC 5539.

   o  Documented that NETCONF 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.

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

   o  Removed the reference to BEEP.

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Appendix B.  Change Log (to be removed by RFC Editor before publication)

B.1.  draft-ietf-netconf-rfc5539bis-07

   o  Limited the scope of the document to TLS with mutual X.509

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

   o  Editorial changes

B.2.  draft-ietf-netconf-rfc5539bis-06

   o  Removed all call-home related text.

   o  Removed redundant text as discussed at the Toronto IETF meeting.

B.3.  draft-ietf-netconf-rfc5539bis-05

   o  Removed the YANG configuration data model since it became a
      separate document.

   o  Added reference to RFC 3234 plus editorial updates.

B.4.  draft-ietf-netconf-rfc5539bis-04

   o  Added the applicability statement proposed by Stephen Hanna.

   o  Added call-home configuration objects and a tls-call-home feature.

   o  Rewrote the text such that the role swap happens right after the
      TCP connection has been established.

B.5.  draft-ietf-netconf-rfc5539bis-03

   o  Added support for call home (allocation of a new port number,
      rewrote text to allow a NETCONF client to be a TLS server and a
      NETCONF server to be a TLS client).

   o  Merged sections 2 and 3 into a new section 2 and restructured the

   o  Extended the IANA considerations section.

   o  Using the cert-to-name mapping grouping from the SNMP
      configuration data model and updated the examples.

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   o  Creating an extensible set of YANG (sub)modules for NETCONF
      following the (sub)module structure of the SNMP configuration

B.6.  draft-ietf-netconf-rfc5539bis-02

   o  Addressed remaining issues identified at IETF 85

      *  Harmonized the cert-maps container of the YANG module in this
         draft with the tlstm container in the ietf-snmp-tls sub-module
         specified in draft-ietf-netmod-snmp-cfg.  Replaced the children
         of the cert-maps container with the children copied from the
         tlstm container of the ietf-snmp-tls sub-module.

      *  Added an overview of data model in the ietf-netconf-tls YANG

      *  Added example configurations.

   o  Addessed issues posted on NETCONF WG E-mail list.

   o  Deleted the superfluous tls container that was directly below the
      netconf-config container.

   o  Added a statement to the text indicating that support for mapping
      X.509 certificates to NETCONF usernames is optional.  This is
      analogous to existing text indicating that support for mapping
      pre-shared keys to NETCONF usernames is optional.  Resource-
      constrained systems now can omit support for mapping X.509
      certificates to NETCONF usernames and still comply with this

   o  Clarified the document structure by promoting the sections of the
      document related to the data model.

   o  Updated author's addresses.

B.7.  draft-ietf-netconf-rfc5539bis-00

   o  Remove the reference to BEEP.

   o  Rename host-part to domain-part in the description of RFC822.

Authors' Addresses

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   Mohamad Badra
   Zayed University


   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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