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Versions: (RFC 5539) 00 01 02 draft-ietf-netconf-rfc5539bis

NETCONF Working Group                                           M. Badra
Internet-Draft                                                        DU
Obsoletes: 5539 (if approved)                           October 23, 2011
Intended status: Standards Track
Expires: April 25, 2012


              NETCONF Over Transport Layer Security (TLS)
                   draft-badra-netconf-rfc5539bis-00

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.  This document 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 http://datatracker.ietf.org/drafts/current/.

   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 April 25, 2012.

Copyright Notice

   Copyright (c) 2011 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
   (http://trustee.ietf.org/license-info) in effect on the date of
   publication of this document.  Please review these documents
   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



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   described in the Simplified BSD License.


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, Identification and Authorization  . .  5
     3.1.  Server Identity  . . . . . . . . . . . . . . . . . . . . .  5
     3.2.  Client Identity  . . . . . . . . . . . . . . . . . . . . .  6
       3.2.1.  Deriving NETCONF Usernames From NETCONF Client
               Certificates . . . . . . . . . . . . . . . . . . . . .  6
       3.2.2.  Deriving NETCONF Usernames From PSK identities . . . . 14
   4.  Security Considerations  . . . . . . . . . . . . . . . . . . . 15
   5.  IANA Considerations  . . . . . . . . . . . . . . . . . . . . . 15
   6.  Acknowledgements . . . . . . . . . . . . . . . . . . . . . . . 16
   7.  Contributor's Address  . . . . . . . . . . . . . . . . . . . . 16
   8.  References . . . . . . . . . . . . . . . . . . . . . . . . . . 16
     8.1.  Normative References . . . . . . . . . . . . . . . . . . . 16
     8.2.  Informative References . . . . . . . . . . . . . . . . . . 17
   Appendix A.  Change Log (to be removed by RFC Editor before
                publication)  . . . . . . . . . . . . . . . . . . . . 17
     A.1.  From RFC5539 to draft-badra-netconf-rfc5539bis-00  . . . . 17
   Author's Address . . . . . . . . . . . . . . . . . . . . . . . . . 18
























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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 "NETCONF over TLS", which includes support for
   certificate and pre-shared key (PSK)-based 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].

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 [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 client 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 6513.  It MUST therefore 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 data.  In particular, the client will send complete
   XML documents to the server containing <rpc> elements, and the server
   will respond 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 this case, the server replies to
   indicate whether the subscription request was successful and, if it
   was successful, the server 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.



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   The previous version [RFC5539] of this document uses the same
   delimiter 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,
   and at the same time be compatible with existing implementations,
   this document uses the framing protocol defined in [RFC6242] as
   following :

   The <hello> message MUST be followed by the character sequence
   ]]>]]>.  Upon reception of the <hello> message, the receiving peer's
   TLS Transport layer conceptually passes the <hello> message to the
   Messages layer.  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.

   Implementation of the protocol specified in this document MAY
   implement any TLS cipher suite that provides 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 MUST close the associated TLS connection if the
   connection is not expected to issue 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 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
   alert, thus generating an incomplete close on the close_notify's
   receiver side.




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3.  Endpoint Authentication, Identification and Authorization

3.1.  Server Identity

   During the TLS negotiation, the client MUST carefully examine the
   certificate presented by the server to determine if it meets the
   client's 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]):

   o  The client MUST use the server hostname it used to open the
      connection (or the hostname specified in the TLS "server_name"
      extension [RFC5246]) 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.

   o  If a subjectAltName extension of type dNSName is present in the
      certificate, it MUST be used as the source of the server's
      identity.

   o  Matching is case-insensitive.

   o  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.

   o  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
   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



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   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

   The server MUST verify the identity of the client to ensure that the
   incoming client request is legitimate before any configuration or
   state data is sent to or received from the client.

   The NETCONF protocol [RFC6241] requires that the transport protocol's
   authentication process MUST result in an authenticated client
   identity whose permissions are known to the server.  The
   authenticated identity of a client is commonly referred to as the
   NETCONF username.

   The username provided by the 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.

   Algorithms for mapping certificates or PSK identities (sent by the
   client) to NETCONF usernames are described below.

3.2.1.  Deriving NETCONF Usernames From NETCONF Client Certificates

   The algorithm for deriving NETCONF usernames from TLS certificates is
   patterned after the algorithm for deriving tmSecurityNames from TLS
   certificates specified in Transport Layer Security (TLS) Transport
   Model for the Simple Network Management Protocol (SNMP) [RFC6353].
   [RFC6353] specifies that an SNMP engine MUST implement several
   algorithms for transforming a certificate to a tmSecurityName, and
   lets the SNMP engine deployer choose and configure the algorithm most
   suitable for the deployer's environment.

   When a NETCONF server accepts a TLS connection from a NETCONF client,
   the NETCONF server MUST produce a NETCONF username from the
   certificate presented by the NETCONF client.  The NETCONF server MAY
   use any of the following algorithms to produce the NETCONF username
   from the certificate presented by the NETCONF client:

   o  Map a certificate directly to a NETCONF username;

   o  Extract the subjectAltName's rfc822Name from the certificate, then
      use the extracted rfc822Name as the NETCONF username;




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   o  Extract the subjectAltName's dnsName from the certificate, then
      use the extracted dnsName as the NETCONF username;

   o  Extract the subjectAltName's iPAddress from the certificate, then
      use the extracted iPAddress as the NETCONF username;

   o  Examine the subjectAltName's rfc822Name, dnsName, and iPAddress
      fields in a pre-defined order, then use the first matching
      subjectAltName value.

   The NETCONF server MUST implement all of these algorithms, and allow
   the deployer to choose and configure the algorithm used.  The
   certificate-to-username-transforms container in the ietf-netconf-tls-
   username YANG module specifies how a NETCONF server transforms an
   certificate into a NETCONF username.

3.2.1.1.  Identifying a Certificate

   A client certificate has an identity: the certificate.  The TLS and
   corresponding protocols provide an identity.  The identity shows that
   "this client certificate has shown that it, indeed, is on the other
   side of the connection".  With a complete certificate, the
   certificate receiver can be certain that for someone or something on
   the other side to use that certificate successfully, it has the
   associated private key.

   The problem with using the entire certificates as the identity is
   that they are difficult for people to use.  It is generally accepted
   that a fingerprint of a certificate is not likely to come up with a
   collision against a fingerprint of another (different) certificate.
   Thus, assuming a good hash algorithm, using fingerprints is a safe
   way to compare two certificates.

   If if a locally held copy of a trusted CA certificate is configured
   in the transformation container, and that CA certificate was used to
   validate the path to the presented certificate, then the NETCONF
   server SHOULD use that list entry in the transformation container.
   All presented certificates validated by the configured CA certificate
   will be transformed to NETCONF usernames using the same
   transformation algorithm.

3.2.1.2.  Remote Configuration

   The ietf-netconf-tls-username YANG module defines objects for
   remotely configuring the mapping of TLS certficates to NETCONF
   usernames.





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module ietf-netconf-tls-username {

 namespace "urn:ietf:params:xml:ns:yang:ietf-netconf-tls-username";

 prefix "tls-username";

 import ietf-yang-types {
   prefix yang;
 }

 organization
   "IETF NETCONF (Network Configuration) Working Group";

 contact
   "WG Web:   <http://tools.ietf.org/wg/netconf/>
    WG List:  <mailto:netconf@ietf.org>

    WG Chair: Mehmet Ersue
              <mailto:mehmet.ersue@nsn.com>

    WG Chair: Bert Wijnen
              <mailto:bertietf@bwijnen.net>

    Editor:   Mohamad Badra
              <mailto:mbadra@gmail.com>";

 description
   "This module applies to NETCONF over TLS.  It specifies how
    NETCONF servers transform X.509 certificates presented by
    clients into NETCONF usernames.  It also specifies how NETCONF
    clients transform NETCONF usernames into X.509 certificates
    for presentation to NETCONF servers.

    This YANG module is patterned after, and closely models, parts of
    the SNMP-TLS-TM-MIB defined in RFC 6353.  Much of the description
    text has been copied directly from the SNMP-TLS-TM-MIB, and modified
    as necessary.

    Copyright (c) 2011 IETF Trust and the persons identified as
    authors of the code. All rights reserved.

    Redistribution and use in source and binary forms, with or
    without modification, is permitted pursuant to, and subject
    to the license terms contained in, the Simplified BSD
    License set forth in Section 4.c of the IETF Trust's
    Legal Provisions Relating to IETF Documents
    (http://trustee.ietf.org/license-info).




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    This version of this YANG module is part of RFC XXXX; see
    the RFC itself for full legal notices.";
 // RFC Ed.: replace XXXX with actual RFC number and
 // remove this note

 // RFC Ed.: please update the date to the date of publication

 revision "2011-10-17" {
   description
     "Initial version";
   reference
     "RFC XXXX: NETCONF over Transport Layer Security (TLS)";
 }

 typedef tls-fingerprint-type {
   type binary {
     length "0..255";
   }
   description
     "A fingerprint value that can be used to uniquely reference
      other data of potentially arbitrary length.

      An tls-fingerprint-type value is composed of a 1-octet hashing
      algorithm identifier followed by the fingerprint value.  The
      octet value encoded is taken from the IANA TLS HashAlgorithm
      Registry (RFC 5246).  The remaining octets are filled using the
      results of the hashing algorithm.

      This typedef allows for a zero-length (blank) tls-fingerprint-type
      value for use in containers where the fingerprint value MAY be
      optional.  YANG definitions or implementations MAY refuse to
      accept a zero-length value as appropriate.";
 }

 //
 //  Objects related to deriving NETCONF usernames from  X.509 certificates.
 //
 leaf certificate-to-username-transform-count {
   type yang:gauge32;
   description
     "A count of the number of certificate-to-username-transforms.";
   config false;
 }

 leaf certificate-to-username-transform-last-changed {
   type yang:date-and-time;
   description
     "The date and time when the certificate-to-username-transforms



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      was last modified through any means.  The value 0 means the
      certificate-to-username-transforms has not been modified since
      the NETCONF server was started.";
   config false;
 }

 container certificate-to-username-transforms {
   config true;
   description
     "This container is used by a NETCONF server to map the NETCONF
      client's presented X.509 certificate to a NETCONF username.

      On an incoming TLS connection, the client's presented
      certificate MUST either be validated based on an established
      trust anchor, or it MUST directly match a fingerprint in this
      container.  This container does not provide any mechanisms for
      configuring the trust anchors; the transfer of any needed
      trusted certificates for path validation is expected to occur
      through an out-of-band transfer.

      Once the certificate has been found acceptable (either by path
      validation or directly matching a fingerprint in this container),
      this container is consulted to determine the appropriate
      NETCONF username to identify with the remote connection.  This
      is done by considering each active list entry from this container
      in prioritized order according to its index value.
      Each list entry's certificate-fingerprint value determines
      whether the list entry is a match for the incoming connection:

          1) If the list entry's certificate-fingerprint value
             identifies the presented certificate, then consider the
             list entry as a successful match.

          2) If the list entry's certificate-fingerprint value
             identifies a locally held copy of a trusted CA
             certificate and that CA certificate was used to
             validate the path to the presented certificate, then
             consider the list entry as a successful match.

      Once a matching list entry has been found, the NETCONF server uses
      the map-type value to determine how the NETCONF username associated
      with the session SHOULD be determined.  See the map-type column's
      description for details on determining the NETCONF username
      value.  If it is impossible to determine a NETCONF 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.  If a resulting NETCONF username mapped
      from a given list entry is not compatible with the needed requirements



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      of a NETCONF username, then it MUST be considered an invalid match
      and additional list entries MUST be searched looking for another
      potential match.

      If no matching and valid list entry can be found, the connection MUST
      be closed and NETCONF messages MUST NOT be accepted over it.

      Missing values of index are acceptable and implementations
      SHOULD continue to the next highest numbered list entry.  It is
      recommended that administrators skip index values to leave room
      for the insertion of future list entries (for example, use values
      of 10 and 20 when creating initial list entries).

      Users are encouraged to make use of certificates with
      subjectAltName fields that can be used as NETCONF usernames so
      that a single root CA certificate can allow all child certificate's
      subjectAltName to map directly to a NETCONF usernames via a 1:1
      transformation.  However, this container is flexible to allow for
      situations where existing deployed certificate infrastructures do
      not provide adequate subjectAltName values for use as NETCONF
      usernames.";

//        Certificates MAY also be mapped to NETCONF usernames using the
//        CommonName portion of the Subject field.  However, the usage
//        of the CommonName field is deprecated and thus this usage is
//        NOT RECOMMENDED.  Direct mapping from each individual
//        certificate fingerprint to a NETCONF username is also possible
//        but requires one entry in the container per NETCONF username and
//        requires more management operations to completely configure a
//        device.";

   list certificate-to-username-transform {
     key "index";
     description
       "A single list entry that specifies a mapping for an incoming
       TLS certificate to a NETCONF username.";

     leaf index {
       type uint32 {
         range "1..4294967295";
       }
       description
         "A unique, prioritized index for the given entry.  Lower
         numbers indicate a higher priority.";
     }

     leaf certificate-fingerprint {
       type tls-fingerprint-type {



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         length "1..255";
       }
       description
         "A cryptographic hash of a X.509 certificate.  The results of
          a successful matching fingerprint to either the trusted CA in
          the certificate validation path or to the certificate itself
          is dictated by the map-type column.";
     }

     leaf map-type {
       type enumeration {
         enum specified                     { value 1;  }
         enum rfc822Name                    { value 2;  }
         enum dnsName                       { value 3;  }
         enum ipAddress                     { value 4;  }
         enum rfc822Name-dnsName-ipAddress  { value 5;  }
         enum rfc822Name-ipAddress-dnsName  { value 6;  }
         enum dnsName-ipAddress-rfc822Name  { value 7;  }
         enum dnsName-rfc822Name-ipAddress  { value 8;  }
         enum ipAddress-dnsName-rfc822Name  { value 9;  }
         enum ipAddress-rfc822Name-dnsName  { value 10; }
       }

       description
         "Specifies the algorithm for deriving a NETCONF username from
         a certificate.  If a mapping succeeds, then it will return a
         NETCONF username.

         If the resulting mapped value is not compatible with the needed
         requirements of a NETCONF username, then future list entries MUST
         be searched for additional NETCONF username matches to look for a
         mapping that succeeds.

         For each enumerated value listed above, the NETCONF server
         derives the NETCONF from the presented client certificate
         as described:

         specified

           Directly specifies the NETCONF username to be used for
           this certificate.  The value of the NETCONF username
           to use is specified in the data leaf of the list.  The
           data leaf MUST contain a non-zero length value or the
           mapping described in this list entry MUST be considered a
           failure.

         rfc822Name




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           Maps a subjectAltName's rfc822Name to a NETCONF username.
           The local part of the rfc822Name is passed unaltered but
           the host-part of the name MUST be passed in lowercase.
           This mapping results in a 1:1 correspondence between
           equivalent subjectAltName rfc822Name values and NETCONF
           username values except that the host-part of the name
           MUST be passed in lowercase.

           Example rfc822Name Field:  FooBar@Example.COM
           is mapped to NETCONF username: FooBar@example.com.

         dnsName

           Maps a subjectAltName's dNSName to a NETCONF username after
           first converting it to all lowercase (RFC 5280 does not
           specify converting to lowercase so this involves an extra
           step).  This mapping results in a 1:1 correspondence between
           subjectAltName dNSName values and the NETCONF username values.

           reference:  RFC 5280 - Internet X.509 Public Key Infrastructure
                       Certificate and Certificate Revocation
                       List (CRL) Profile.

         ipAddress

           Maps a subjectAltName's iPAddress to a NETCONF username by
           transforming the binary encoded address as follows:

           1) for IPv4, the value is converted into a
              decimal-dotted quad address (e.g., '192.0.2.1').

           2) for IPv6 addresses, the value is converted into a
              32-character all lowercase hexadecimal string
              without any colon separators.

              This mapping results in a 1:1 correspondence between
              subjectAltName iPAddress values and the NETCONF username
              values.

         rfc822Name-dnsName-ipAddress
         rfc822Name-ipAddress-dnsName
         dnsName-ipAddress-rfc822Name
         dnsName-rfc822Name-ipAddress
         ipAddress-dnsName-rfc822Name
         ipAddress-rfc822Name-dnsName

           For each of these enumerations, the NETCONF server derives the
           NETCONF username in a similar manner.  The NETCONF server



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           derives the NETCONF username from the subjectAltName fields
           rfc822Name, dnsName, and ipAddress, as described in sections
           above.  However, each of these subjectAltName fields is
           examined in the order specified by the enumeration name.
           The first matching subjectAltName value found in the certificate
           MUST be used when deriving the NETCONF username.

           For example, the rfc822Name-dnsName-ipAddress enumeration
           specifies the NETCONF server first examines the rfc822Name,
           then examines the dnsName, then finally examines the ipAddress.
           In contrast, the ipAddress-rfc822Name-dnsName enumeration
           specifies the NETCONF server first examines the ipAddress
           name, then examines the rfc822Name, then finally examines
           the dnsName.

           These mappings result in a 1:1 correspondence between
           subjectAltName values and NETCONF username values.  The
           sub-mapping algorithms produced by these combined algorithms
           cannot produce conflicting results between themselves.";
     }  //  leaf map-type

     leaf data {
       type string {
         length "1..max";
       }
       description
         "Auxiliary data used as optional configuration information for
         a given mapping specified by the map-type column.  Only some
         mapping systems will make use of this column.  The value in this
         column MUST be ignored for any mapping type that does not require
         data present in this column.";
     }
   }  // list certificate-to-username-transform
 }    // container certificate-to-username-transform
}


3.2.2.  Deriving NETCONF Usernames From PSK identities

   Implementations MAY optionally support TLS Pre-Shared Key (PSK)
   authentication [RFC4279].  RFC4279 describes pre-shared key
   ciphersuites for TLS.  During the TLS Handshake, the client indicates
   which key to use by including a "PSK identity" in the TLS
   ClientKeyExchange message [RFC4279].  On the server side, this PSK
   identity is used to lookup the key corresponding to the presented PSK
   identity.  If the selected pre-shared keys match, then the client is
   authenticated and the PSK identity is used as the NETCONF username.
   For details on how the PSK identity MAY be encoded in UTF-8, see



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   section 5.1. of RFC [RFC6241].


4.  Security Considerations

   The security considerations described throughout [RFC5246] and
   [RFC6241] apply here as well.

   This document in its current version 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, BEEP or SSH transport can be used.

   An attacker might be able to inject arbitrary NETCONF messages via
   some application that does not carefully check exchanged messages.
   When the :base:1.1 capability is not advertised by both peers, an
   attacker might be able to deliberately insert the delimiter sequence
   ]]>]]> in a NETCONF message to create a DoS attack.  If the :base:1.1
   capability is not advertised by both peers, applications and NETCONF
   APIs MUST ensure that the delimiter sequence ]]>]]> never appears in
   NETCONF messages; otherwise, those messages can be dropped, garbled,
   or misinterpreted.  More specifically, if the delimiter sequence is
   found in a NETCONF message by the sender side, a robust
   implementation of this document SHOULD warn the user that illegal
   characters have been discovered.  If the delimiter sequence is found
   in a NETCONF message by the receiver side (including any XML
   attribute values, XML comments, or processing instructions), a robust
   implementation of this document MUST silently discard the message
   without further processing and then stop the NETCONF session.

   Finally, this document does not introduce any new security
   considerations compared to [RFC6242] and [RFC4742].


5.  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 name "netconf-tls".  This port will be the default
   port for NETCONF over TLS, as defined in this document.









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      Registration Contact:  Mohamad Badra, badra@isima.fr.
      Transport Protocol:  TCP.
      Port Number:  6513
      Broadcast, Multicast or Anycast: No.
      Port Name:  netconf-tls.
      Service Name: netconf.
      Reference: RFC 5539



6.  Acknowledgements

   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 also appreciates 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.  Contributor's Address

   Ibrahim Hajjeh
   Ineovation
   France

   EMail: ibrahim.hajjeh@ineovation.fr

   Alan Luchuk
   SNMP Research, Inc.
   3001 Kimberlin Heights Road
   Knoxville, TN  37920-9716

   EMail: luchuk@snmp.com


8.  References

8.1.  Normative References

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

   [RFC4279]  Eronen, P. and H. Tschofenig, "Pre-Shared Key Ciphersuites



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              for Transport Layer Security (TLS)", RFC 4279,
              December 2005.

   [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 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.

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

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

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

8.2.  Informative References

   [RFC4642]  Murchison, K., Vinocur, J., and C. Newman, "Using
              Transport Layer Security (TLS) with Network News Transfer
              Protocol (NNTP)", RFC 4642, October 2006.

   [RFC5277]  Chisholm, S. and H. Trevino, "NETCONF Event
              Notifications", RFC 5277, July 2008.

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


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

A.1.  From RFC5539 to draft-badra-netconf-rfc5539bis-00

   o  Added text on how the generation of a NETCONF username is done.

   o  Added text on how does this document fulfill the requirements in
      6241 for the format of the username.




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   o  Removed unneeded wording about client/server, and changed use of
      client/server, manager/agent to SSH client/server and NETCONF
      client/server.

   o  Added text to Security Considerations about EOM issues.

   o  Added option for the chunked encoding described in RFC6242.

   o  Added 1.1 capability to enable the chunked encoding described in
      RFC6242.


Author's Address

   Mohamad Badra
   DU

   Email: mbadra@gmail.com

































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