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Versions: 00 01 draft-ietf-netconf-zerotouch

NETCONF Working Group                                          K. Watsen
Internet-Draft                                                  S. Hanna
Intended status: Standards Track                        Juniper Networks
Expires: August 05, 2014                                       J. Clarke
                                                           Cisco Systems
                                                          M. Abrahamsson
                                                               T-Systems
                                                           February 2014


       Zero Touch Provisioning for NETCONF Call Home (ZeroTouch)
                   draft-kwatsen-netconf-zerotouch-01

Abstract

   This draft presents a technique for how to establish a secure NETCONF
   connection between a newly deployed networking device, configured
   with just its factory default settings, and the new owner's Network
   Management System (NMS).

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 August 05, 2014.

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
   (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



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   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.  Requirements Terminology  . . . . . . . . . . . . . . . . . .   2
   2.  Introduction  . . . . . . . . . . . . . . . . . . . . . . . .   2
   3.  Actors and Roles  . . . . . . . . . . . . . . . . . . . . . .   4
     3.1.  Device  . . . . . . . . . . . . . . . . . . . . . . . . .   4
     3.2.  Configlet . . . . . . . . . . . . . . . . . . . . . . . .   4
     3.3.  Configlet Signer  . . . . . . . . . . . . . . . . . . . .   5
     3.4.  Configuration Server  . . . . . . . . . . . . . . . . . .   5
     3.5.  Network Management System (NMS) . . . . . . . . . . . . .   7
   4.  Device Boot Sequence  . . . . . . . . . . . . . . . . . . . .   7
     4.1.  Precondition  . . . . . . . . . . . . . . . . . . . . . .   7
     4.2.  Runtime Operation . . . . . . . . . . . . . . . . . . . .   9
   5.  Configlets  . . . . . . . . . . . . . . . . . . . . . . . . .  12
     5.1.  Data Model  . . . . . . . . . . . . . . . . . . . . . . .  12
     5.2.  Signature . . . . . . . . . . . . . . . . . . . . . . . .  15
     5.3.  YANG Module . . . . . . . . . . . . . . . . . . . . . . .  15
   6.  Security Considerations . . . . . . . . . . . . . . . . . . .  19
   7.  IANA Considerations . . . . . . . . . . . . . . . . . . . . .  20
   8.  Acknowledgements  . . . . . . . . . . . . . . . . . . . . . .  20
   9.  References  . . . . . . . . . . . . . . . . . . . . . . . . .  20
     9.1.  Normative References  . . . . . . . . . . . . . . . . . .  20
     9.2.  Informative References  . . . . . . . . . . . . . . . . .  21
   Appendix A.  Examples . . . . . . . . . . . . . . . . . . . . . .  21
     A.1.  Signed Configlet  . . . . . . . . . . . . . . . . . . . .  21
   Appendix B.  Change Log . . . . . . . . . . . . . . . . . . . . .  25
     B.1.  00 to 01  . . . . . . . . . . . . . . . . . . . . . . . .  25
   Appendix C.  Open Issues  . . . . . . . . . . . . . . . . . . . .  25
     C.1.  How to best structure the Configlet YANG module?  . . . .  25
     C.2.  Should Configlets always be signed? . . . . . . . . . . .  25

1.  Requirements Terminology

   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.  Introduction

   The solution presented herein is designed to support the NETCONF
   configuration protocol [RFC6241].  This is achieved by leveraging the
   recently standardized call home mechanisms for SSH [REVERSE-SSH] and
   TLS [RFC5539bis].




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   A fundamental business requirement is to reduce operational costs
   where possible.  Deploying new devices is typically one of the
   largest costs in running the network, as sending trained specialists
   to each site is both cost prohibitive and doesn't scale.

   Both networking vendors and standard bodies have tried to address
   this issue, with varying levels of success.  For instance, the
   Broadband Forum TR-069 specification [TR069] relies on DHCP for NMS
   discovery, but this only works in environments where the DHCP server
   can be configured, which isn't the case when the device is connected
   to an ISP's network.  In another example, some network vendors have
   enabled their devices to load an initial configuration from removable
   storage media (e.g., a USB flash drive), but not all devices have
   such ports.

   The solution presented herein attempts to addresses the evaluation
   criteria outlined by the draft "Configuring Security Parameters in
   Small Devices" [draft-hanna-zeroconf-seccfg-00]: security,
   flexibility, ease of use, and device cost.  More specifically:

   o  Security

         Security is fundamental to any automated discovery solution,
         especially one that bootstraps the parameters used to secure a
         device's connection to its NMS.  Consistent with [RFC3365],
         security is a required aspect of ZeroTouch.  Every ZeroTouch
         implementation is sure to be secure.

   o  Flexibility

         ZeroTouch is designed to support a wide variety of deployments,
         including cases where the device is connected to a network
         without administrative control of the local DHCP and DNS
         servers, where the device is connected to an untrusted network,
         or deployed behind a gateway that dynamically translates its
         network address (e.g., NAT).  Special consideration is also
         provided for devices that are on a network with no public
         Internet access.

   o  Ease of Use

         Ultimately, the success of the solution depends on the ability
         for presumably non-technical personnel to be able to complete
         the installation by themselves.  To this end, it is envisioned
         that installers only need to connect the device to a wired or
         wireless network and a power source and wait for the device to
         indicate success.  ZeroTouch also attempts to not be overly
         complicated for NMS administrators.



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   o  Device Cost

         For vendors of devices with already slim margins, such as
         consumer-oriented devices, a significant concern is the cost of
         goods.  Fortunately, the solution presented in this draft
         requires minimal additional components.  Additionally, the
         development effort doesn't seem exorbitant, though that may
         vary by vendor and their circumstances.

3.  Actors and Roles

3.1.  Device

   The device is the networking entity that initiates Zero Touch.
   Whenever a device boots with its factory default settings, it
   initiates ZeroTouch with the goal of finding a Configlet with which
   it can use to configure itself.  Once a Configlet is found, the
   device initializes its configuration using that Configlet and then
   exits ZeroTouch.  Since the Configlet configures the device to "call
   home" upon entering its normal operating mode, the device immediately
   begins trying to establish a reverse-SSH or reverse-TLS connection,
   as specified by the Configlet.

3.2.  Configlet

   A Configlet is an XML file, containing specific YANG-defined
   configuration, that has been signed by a trusted signer known to the
   device (e.g., the device's manufacturer).

   The Configlet data-model, defined by the YANG module in this document
   (see Section 3.2), is just enough to configure a local user account
   and either reverse-SSH or reverse-TLS.  More specifically, this data-
   model is a subset of what's defined in ietf-system and ietf-netconf-
   server YANG models.  This focused data-model is consistent with the
   common use-case of having the NMS push a full configuration to a
   device when it calls home.

   The signature on the Configlet is enveloped, meaning that the
   signature is contained inside the XML file itself.  The signature
   block also contains the X.509 certificate of the Configlet Signer and
   its chain of trust.

   Once a device authenticates the signature on a Configlet and matches
   the unique identifier (e.g., serial number) within the Configlet, it
   merges the configuration contained in the Configlet into its running
   datastore.





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3.3.  Configlet Signer

   A Configlet Signer is the entity authorized by the device
   manufacturer to sign Configlets for its devices (note: this may be
   the device vendor itself).

   A Configlet Signer MUST provide a user-facing service enabling the
   creation of a Configlet with user-specific deployment values, using
   the YANG schema defined in Section 3.2.  This document does not
   specify what form this interface must take, so it is the Configlet
   Signer's discretion if it is a web page, a REST API, or something
   else.

   A Configlet Signer MUST ensure that the end-user is the rightful
   owner of the device containing the unique identifier value to be put
   into the Configlet.  How a Configlet Signer ensures this is outside
   the scope of this document, but it is envisioned that the vendor
   would provide a secured interface for its trusted Configlet Signers
   to use.

   A Configlet Signer MUST have an X.509 certificate with Key Usage
   capable of signing data (digitalSignature) and be signed by a
   certificate authority having a chain of trust leading to a trust
   anchor known to the devices loading its Configlets.  The Configlet
   Signer MUST possess all intermediate certificates leading to its
   trust anchor.

   When a Configlet Signer signs a Configlet, it attaches both the
   signature and the chain of X.509 certificates, including its own, but
   not necessarily including the trust anchor's certificate.  This chain
   of certificates is needed so a device can validate a Configlet using
   only the Configlet Signer trust anchors known to it.

   A Configlet Signer does not need to retain the Configlet after
   signing it; it is expected that either the end-user or the Configlet
   Signer will convey the signer Configlet to a Configuration Server
   where it will be hosted.

3.4.  Configuration Server

   A Configuration Server is the entity hosting configurations that can
   be downloaded over a network.  Configuration Servers are known to
   devices in the form of a URI, to which a device appends the
   fingerprint of its entity certificate (see Section 4.1 for details).
   For instance, if the URI were:






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      https://example.com?id=
      scp://user@zerotouch.example.com/configlets/
      ftp://example.com/zerotouch/configlets/

   then the device would try to access:

      https://example.com?id=<fingerprint>
      scp://user@zerotouch.example.com/configlets/<fingerprint>
      ftp://example.com/zerotouch/configlets/<fingerprint>

   where the fingerprint is generated using the SHA-256 algorithm over
   the device's entity certificate.  For instance, using OpenSSL's
   command line tool: `openssl dgst -sha256 <entity certificate>` (see
   Section 4.1).

   The Configuration Server is expected to be able to map the
   fingerprint to a device-specific unique identifier (e.g., serial
   number), which is the value contained in the Configlet it is hosting.
   How the Configuration Server does this mapping is outside the scope
   of this document, but it is envisioned that the vendor would provide
   a secured interface for its trusted Configuration Servers to use.

   Configuration Servers do not need to use encryption, since the
   Configlets themselves are immutable to tampering, due to being
   signed.  However, for confidentiality reasons, it is RECOMMENDED to
   use encryption, so adversaries cannot see the Configlet's otherwise
   clear-text content, from which they can learn some details about the
   device's internal deployment.

   If a Configuration Server uses X.509-based encryption, then its X.509
   certificate MUST have a chain of trust to a trust anchor known to
   devices.  The Configuration Server MUST possess all the intermediate
   certificates leading to a trust anchor.

   When a Configuration Server negotiates encryption with the device, it
   provides the chain of X.509 certificates, including its own, but not
   necessarily including the trust anchor's certificate.  Devices need
   the chain of certificates to be passed so they can validate the
   server using only a minimal list of Configuration Server trust
   anchors.

   Configuration Server's SHOULD automatically expire Configlets after
   some user-specified amount of time.

   In order to facilitate troubleshooting and auditing, the
   Configuration Server SHOULD record into a log a record of the various
   Configlet download requests.  This draft does not define what
   information should be kept or for how long.



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3.5.  Network Management System (NMS)

   The NMS is the ultimate destination of ZeroTouch for a device.  It is
   the NMS's network address configured in the Configlet.  The device
   will connect to the NMS using either a reverse-SSH or reverse-TLS, as
   configured by the Configlet loaded.

   In order to authenticate the device, the NMS MUST possess the X.509
   certificate for the trust anchor leading to the device's entity
   certificate.  The NMS uses this certificate to validate the server-
   certificate the device presents during SSH or TLS transport
   negotiation.

   The NMS SHOULD also validate that the unique identifier (e.g., serial
   number), within the "Common Name" field of the device's X.509
   certificate, is an identity that the NMS is expecting, and not
   another device having the same device type.  In order for the NMS to
   know the unique identifiers for devices shipped directly to their
   destinations, it may be necessary for the device manufacturer to
   provide the unique identifiers along with other shipping or billing
   information.  This draft not specify a format for this information
   exchange.

   In addition to authenticating the device, the NMS must also
   authenticate itself to the device.  How this is done is protocol
   specific.  For reverse-SSH, the NMS needs to know the information
   configured on the device by the Configlet it loaded, specifically the
   name of a local user account and the necessary credentials configured
   for the account (i.e., password or the private-half of a SSH host
   key).  For reverse-TLS, the NMS must present a client certificate.
   Presumably the NMS has been configured with the information used when
   the Configlet was created.

4.  Device Boot Sequence

4.1.  Precondition

   Devices supporting ZeroTouch MUST support either reverse-SSH or
   reverse-TLS, and MAY support both.  In either case, the device MUST
   present an X.509-based certificate encoding a unique device
   identifier (e.g. serial number) and a public key, both signed by a
   trusted certificate authority.  This certificate is the "entity
   certificate" in the diagram below.  This certificate is needed in
   order for the NMS to positively authenticate a device.  For reverse-
   SSH, this certificate requirement constrains the SSH host key
   algorithms the device is allowed to to use to those defined in
   [RFC6187].




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   The unique identifier MUST be something that is both known to the
   device and easily tracked through labels affixed to the device as
   well as the box it is packaged in.  A device's serial number is
   commonly treated this way and would be suitable for this purpose.

   The device MUST possess the private key matching the public key
   encoded in the entity certificate.  Ideally, the private key SHOULD
   be generated and protected by a tamper-resistant cryptographic
   processor, as this provides the greatest assurance that the private
   key is known to no one, including the device's manufacturer.

   The entity certificate MUST be signed by a certificate authority
   having a chain of trust to a well-known trust anchor.  The device
   MUST also possess the X.509 certificates for any intermediate CAs
   leading to the trust anchor.  During SSH or TLS transport setup, the
   device will send both its entity and any intermediate certificates so
   the NMS can verify the certificate path using only the well-known
   trust anchor.

   Since the entity certificate is to be used for SSH and TLS
   connections, its Key Usage, if set, SHOULD have the digitalSignature,
   keyEncipherment, and keyAgreement bits set.

   In order for a device to know where it can obtain a Configlet, it
   MUST have two sets of URIs, identifying resources where it can obtain
   Configlets.  One set contains secure schemes (e.g. https://, scp://)
   and the other contains insecure schemes (e.g., http://, ftp://).
   These URIs point to the "Configuration Servers" in the diagram below.

   In order for a device to use a URI with a secure scheme, devices MUST
   possess a trust anchor certificate that it can use to authenticate
   the Configuration Server with.  As each Configuration Server may use
   a different trust anchor, this generalizes to a list of Configuration
   Server trust anchor certificates.  These trust anchors MAY include
   broadly recognized certificate authorities, such as the certificates
   packaged with web browsers.

   In order for a device to authenticate Configlets, it MUST have a
   trust anchor for the CA that signed the Configlet.  The CA used to
   sign Configlets is called a "Configlet Signer" in the diagram below.
   In order to enable Configlets to be signed by different CAs, the
   device MAY have either a list of trust anchors, or a single trust
   anchor that delegates Configlet signing trust to other CAs.  The
   diagram below shows a list of Configlet Signer trust anchors only
   because it is the more flexible option.

   Devices SHOULD ensure that all its trust anchor certificates,
   including those for the Configlet Signer and Configuration Server,



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   are protected from external modification.  It is for this reason that
   the diagram below shows them in immutable storage.  However, it may
   be necessary to update these certificates over time (e.g., the vendor
   wants to delegate trust to a new CA).  Therefore, devices MAY update
   these trust anchors when needed through a verifiable process, such as
   a software upgrade using signed software images.

   Devices SHOULD ensure that the certificates for its trust anchors are
   protected from external modification, specifically the Configlet
   Signer and Configuration Server X.509 certificates.  It is for this
   reason that the diagram below shows them in immutable storage.  The
   certificates for the device's trust anchors MAY be updated along with
   a standard software image upgrade.

   Device State Precondition

   +------------------------------------------------------------------+
   |                            <device>                              |
   |                                                                  |
   |     +------------------------------------------------------+     |
   |     |                <immutable storage>                   |     |
   |     |                                                      |     |
   |     |  list of Configlet Signer trust anchor certificates  |     |
   |     |  list of Configuration Server trust anchor certs     |     |
   |     +------------------------------------------------------+     |
   |                                                                  |
   |   +----------------------------------------------------------+   |
   |   |                    <other storage>                       |   |
   |   |                                                          |   |
   |   |  two sets of Configuration Server URIs                   |   |
   |   |  device entity & associated intermediate certificate(s)  |   |
   |   +----------------------------------------------------------+   |
   |                                                                  |
   |                    +----------------------+                      |
   |                    |  <crypto processor>  |                      |
   |                    |                      |                      |
   |                    |  device private key  |                      |
   |                    +----------------------+                      |
   |                                                                  |
   +------------------------------------------------------------------+

4.2.  Runtime Operation

   Whenever a device boots with its factory default settings, it
   initiates ZeroTouch with the goal of finding a configuration with
   which it can use to configure itself.





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   The device MUST first initialize its networking as per its default
   factory configuration.  This SHOULD result in the dynamic assignment
   of an IP address, subnet or prefix, gateway, and a DNS server.

   While initializing its networking, the device MAY receive some
   additional URIs for where a software image or configuration can be
   downloaded.  This draft does not define how such URIs MAY be
   exchanged, for instance, using DHCP options.

   If, while initializing its networking, the device receives software
   image URIs, it MAY download and install the software image only if
   the image is protected from modification (e.g., the image is signed)
   and the device is able to verify its integrity.  The device SHOULD
   try URIs with secure schemes before URIs with insecure schemes (e.g.,
   scp:// before ftp://).  If the device needs to reboot to activate the
   new software image, it MUST do so with its default factory
   configuration set so that ZeroTouch will run again when the device
   comes back up.

   If, while initializing its networking, the device receives
   configuration URIs, each URI SHOULD be appended to one of the
   device's two sets of Configuration Server URIs, depending on if the
   URI's scheme is secure or not.  URIs added this way MUST remain
   distinguishable from those URIs the device was shipped with, for
   reasons discussed in Section 4.2.

   Before trying any of the Configuration Server URIs, the device SHOULD
   first try to load a configuration through local means that assert
   physical presence.  For instance, a removable USB flash drive or
   near-field communication mechanism.  Configurations obtained through
   an assertion of physical presence do not have to be signed or contain
   the device's unique identifier (e.g., serial number).  If a Configlet
   is found, the device MUST use it without trying any of the
   Configuration Server URIs.

   If a configuration was not found via physical presence, the device
   then iterates over its two sets of Configuration Server URIs.  The
   device MUST first try all the URIs from the set having secure schemes
   before trying any of the URIs from the set having insecure schemes.
   For each URI, until a usable configuration is found and successfully
   loaded, the device attempts to download a configuration from the URI.
   If the URI uses a secure scheme (e.g., https), the device MUST
   validate the Configuration Server's certificate using one of its
   Configuration Server trust anchors.  If the device is unable to
   verify the server's certificate, the device MUST skip that URI.  If
   the device reaches the end of all its URIs without finding a
   configuration, it MAY continue its normal boot sequence using its
   factory default configuration.



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   When the device is accessing a Configuration Server URI that it was
   shipped with (i.e., not discovered while initializing its networking,
   it MUST do so by appending the fingerprint of its entity certificate
   to the URI's string, as described in the Section 3.4.  For URIs
   discovered while initializing its networking, the device MAY try both
   the raw URI as well as the permutation of it using its fingerprint.

   The Configuration Server's response MAY be anything allowed by the
   given URI's scheme.  For instance, if the scheme is HTTP-based, the
   Configuration Server MAY return an HTTP redirect.  In this way, a
   vendor's Configuration Server service may allow the device owner to
   redirect the device to a Configuration Server running in their
   network.

   If the Configuration Server returns a Configlet, the device MUST
   first verify it before use.  Configlet verification entails both
   verifying the Configlet's signature using the device's list of
   Configlet Signer trust anchors, and also verifying that the unique
   identifier (e.g., serial number) within the Configlet matches the
   device's unique identifier.

   Once a Configlet is authenticated, the device merges the Configlet's
   contents into its running configuration and then exits ZeroTouch.
   Since the Configlet configures the device to "call home," upon
   entering its normal operating mode, the device immediately begins
   trying to establish a reverse-SSH or reverse-TLS connection, as
   specified by the Configlet.

   If configured to establish a reverse-SSH connection, the the device
   MUST use its entity and associated intermediate X.509 certificates as
   its host key per RFC 6187 [RFC6187].  If configured to use reverse-
   TLS, the device MUST use its entity and associated intermediate X.509
   certificates as its server-side certificate for the TLS connection.

   In order to facilitate troubleshooting, the device SHOULD record into
   a log information relating to its stepping through the ZeroTouch
   sequence of steps.  This draft does not define any specific log
   messages, for instance, for Syslog or SNMP.

   ZeroTouch Sequence Diagram











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          DEVICE     LOCAL DHCP          CONFIGLET         NMS
            |          SERVER             SERVERS           |
            |             |                  |              |
            |------------>|                  |              |
            | Lease IP    |                  |              |
            |             |                  |              |
            |------------------------------->|              |
            | Iterate until Configlet found  |              |
            |             |                  |              |
            |             |                  |              |
            |---------------------+          |              |
            | Validate Configlet  |          |              |
            |<--------------------+          |              |
            |             |                  |              |
            |             |                  |              |
            |---------------------------------------------->|
            | reverse-SSH or reverse-TLS     |              |
            |             |                  |              |
            |             |                  |              |

5.  Configlets

5.1.  Data Model

   The Configlet's data is modeled after the data models provided by
   draft-ietf-netmod-system-mgmt and draft-kwatsen-netconf-server.
   These data models are used to configure a local user account and
   either reverse-SSH or reverse-TLS.  Networking is not included in the
   Configlet data model as it is expected that the device will by
   assigned a dynamic address by the network and that it will use this
   address both when connecting to a Configuration Server and later the
   NMS.

   From draft-ietf-netmod-system-mgmt, the data model for user
   authentication has the following structure:


         +--rw system
            +--rw authentication
               +--rw user-authentication-order*   identityref
               +--rw user* [name]
                  +--rw name        string
                  +--rw password?   crypt-hash
                  +--rw ssh-key* [name]
                     +--rw name         string
                     +--rw algorithm    string
                     +--rw key-data     binary




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   From draft-kwatsen-netconf-server, the data model for reverse-SSH has
   the following structure:

   +--rw netconf
      +--rw ssh {ssh}?
         +--rw listen {inbound-ssh}?
         |  +--rw (one-or-many)?
         |     +--:(one-port)
         |     |  +--rw port?        inet:port-number
         |     +--:(many-ports)
         |        +--rw interface* [address]
         |           +--rw address    inet:ip-address
         |           +--rw port?      inet:port-number
         +--rw call-home {outbound-ssh}?
            +--rw applications
               +--rw application* [name]
                  +--rw name                  string
                  +--rw description?          string
                  +--rw servers
                  |  +--rw server* [address]
                  |     +--rw address    inet:host
                  |     +--rw port?      inet:port-number
                  +--rw connection-type
                  |  +--rw (connection-type)?
                  |     +--:(persistent-connection)
                  |     |  +--rw persistent
                  |     |     +--rw keep-alives
                  |     |        +--rw interval-secs?   uint8
                  |     |        +--rw count-max?       uint8
                  |     +--:(periodic-connection)
                  |        +--rw periodic
                  |           +--rw timeout-mins?   uint8
                  |           +--rw linger-secs?    uint8
                  +--rw reconnect-strategy
                  |  +--rw start-with?      enumeration
                  |  +--rw interval-secs?   uint8
                  |  +--rw count-max?       uint8
                  +--rw host-keys
                     +--rw host-key* [name]
                        +--rw name    string

   Also from draft-kwatsen-netconf-server, the data model for reverse-
   TLS has the following structure:








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   +--rw netconf
      +--rw tls {tls}?
         +--rw listen {inbound-tls}?
         |  +--rw (one-or-many)?
         |     +--:(one-port)
         |     |  +--rw port?        inet:port-number
         |     +--:(many-ports)
         |        +--rw interface* [address]
         |           +--rw address    inet:ip-address
         |           +--rw port?      inet:port-number
         +--rw call-home {outbound-tls}?
         |  +--rw applications
         |     +--rw application* [name]
         |        +--rw name                  string
         |        +--rw description?          string
         |        +--rw servers
         |        |  +--rw server* [address]
         |        |     +--rw address    inet:host
         |        |     +--rw port?      inet:port-number
         |        +--rw connection-type
         |        |  +--rw (connection-type)?
         |        |     +--:(persistent-connection)
         |        |     |  +--rw persistent
         |        |     |     +--rw keep-alives
         |        |     |        +--rw interval-secs?   uint8
         |        |     |        +--rw count-max?       uint8
         |        |     +--:(periodic-connection)
         |        |        +--rw periodic
         |        |           +--rw timeout-mins?   uint8
         |        |           +--rw linger-secs?    uint8
         |        +--rw reconnect-strategy
         |           +--rw start-with?      enumeration
         |           +--rw interval-secs?   uint8
         |           +--rw count-max?       uint8
         +--rw cert-maps {tls-map-certificates}?
         |  +--rw cert-to-name* [id]
         |     +--rw id             uint32
         |     +--rw fingerprint    x509c2n:tls-fingerprint
         |     +--rw map-type       identityref
         |     +--rw name           string
         +--rw psk-maps {tls-map-pre-shared-keys}?
            +--rw psk-map* [psk-identity]
               +--rw psk-identity        string
               +--rw user-name           nacm:user-name-type
               +--rw not-valid-before?   yang:date-and-time
               +--rw not-valid-after?    yang:date-and-time
               +--rw key                 yang:hex-string




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5.2.  Signature

   Configlets obtained over the network MUST be signed using the W3C
   standard "XML Signature Syntax and Processing" [XMLSIG].  The entire
   contents of the Configlet MUST be signed.  The signature block must
   also include the Configlet Signer's certificate and any intermediate
   certificates leading to a Configlet Signer trust anchor.

   A signed Configlet example is in the Appendix.

5.3.  YANG Module

   Following is the YANG module for the Configlet:

   module ietf-netconf-zerotouch {

     namespace "urn:ietf:params:xml:ns:yang:ietf-netconf-zerotouch";
     prefix "nczerotouch";

     //import ietf-system {
     //    prefix ncsystem;
     //}

     import ietf-netconf-server {
         prefix ncserver;
     }

     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:   Kent Watsen
                 <mailto:kwatsen@juniper.net>";

     description
      "This module contains a collection of YANG definitions for
       configuring NETCONF zerotouch.

       Copyright (c) 2014 IETF Trust and the persons identified as



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       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).

       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 "2014-01-24" {
       description
        "Initial version";
       reference
        "RFC XXXX: A YANG Data Model for NETCONF ZeroTouch Configlet";
     }

     typedef crypt-hash {
       type string {
         pattern
           '$0$.*'
         + '|$1$[a-zA-Z0-9./]{1,8}$[a-zA-Z0-9./]{22}'
         + '|$5$(rounds=\d+$)?[a-zA-Z0-9./]{1,16}$[a-zA-Z0-9./]{43}'
         + '|$6$(rounds=\d+$)?[a-zA-Z0-9./]{1,16}$[a-zA-Z0-9./]{86}';
       }
       description
         "The crypt-hash type is used to store passwords using
          a hash function.  The algorithms for applying the hash
          function and encoding the result are implemented in
          various UNIX systems as the function crypt(3).

          A value of this type matches one of the forms:

            $0$<clear text password>
            $<id>$<salt>$<password hash>
            $<id>$<parameter>$<salt>$<password hash>

          The '$0$' prefix signals that the value is clear text.  When
          such a value is received by the server, a hash value is
          calculated, and the string '$<id>$<salt>$' or
          $<id>$<parameter>$<salt>$ is prepended to the result.  This
          value is stored in the configuration data store.



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          If a value starting with '$<id>$', where <id> is not '0', is
          received, the server knows that the value already represents a
          hashed value, and stores it as is in the data store.

          When a server needs to verify a password given by a user, it
          finds the stored password hash string for that user, extracts
          the salt, and calculates the hash with the salt and given
          password as input.  If the calculated hash value is the same
          as the stored value, the password given by the client is
          accepted.

          This type defines the following hash functions:

            id | hash function | feature
            ---+---------------+-------------------
             1 | MD5           | crypt-hash-md5
             5 | SHA-256       | crypt-hash-sha-256
             6 | SHA-512       | crypt-hash-sha-512

          The server indicates support for the different hash functions
          by advertising the corresponding feature.";
       reference
         "IEEE Std 1003.1-2008 - crypt() function
          Wikipedia: http://en.wikipedia.org/wiki/Crypt_(C)
          RFC 1321: The MD5 Message-Digest Algorithm
          FIPS.180-3.2008: Secure Hash Standard";
     }


     container configlet {
       description
        "Top-level container for ZeroTouch configuration objects.";

       container system {
         // no way to use top-level "netconf" container?
         container authentication {

           list user {
             key name;
             description
               "The list of local users configured on this device.";

             leaf name {
               type string;
               description
                "The user name string identifying this entry.";
             }
             leaf password {



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               type crypt-hash;
               description
                 "The password for this entry.";
             }
             list ssh-key {
               key name;
               description
                 "A list of public SSH keys for this user.";
               reference
                 "RFC 4253: The Secure Shell (SSH) Transport Layer
                            Protocol";

               leaf name {
                 type string;
                 description
                   "An arbitrary name for the ssh key.";
               }
               leaf algorithm {
                 type string;
                 mandatory true;
                 description
                   "The public key algorithm name for this ssh key.

                    Valid values are the values in the IANA Secure Shell
                    (SSH) Protocol Parameters registry, Public Key
                    Algorithm Names";
                 reference
                   "IANA Secure Shell (SSH) Protocol Parameters
                    registry, Public Key Algorithm Names";
               }
               leaf key-data {
                 type binary;
                 mandatory true;
                 description
                   "The binary key data for this ssh key.";
               }
             }
           }
         }
       }

       container netconf-server {
         // no way to use top-level "netconf" container?

         container ssh {
           uses ncserver:ssh-config;
             // no way to disable "listen" container?
         }



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         container tls {
           uses ncserver:tls-config;
             // no way to disable "listen" container?
         }
       }


     }
   }

6.  Security Considerations

   It is not possible to substitute a Configlet created for a different
   device, since devices assert that the Configlet contains their unique
   identifier (e.g., serial number).

   It is possible to substitute a Configlet created for a device with a
   different Configlet created for the same device.  Generally, unless
   imposed by the Configlet Signers, there is no limit to the number of
   Configlets that may be generated for a given device.  This could be
   resolved, in part, by placing a timestamp into the Configlet and
   ensuring devices do not load Configlets older than some amount, but
   this requires the devices have an accurate clock when validating a
   Configlet and for Configlet Signers to not sign a Configlet when
   another Configlet is still active.

   Confidentiality of Configlets loaded over a network is only assured
   when the device uses a secure networking scheme and validates the
   Configuration Server's certificate.

   Confidentiality is further provided by using the fingerprint of the
   device's entity certificate when doing a Configuration Server lookup,
   as it is not guessable and thus makes it nearly impossible for an
   adversary to lookup.

   This draft allows devices to try alternate means to load a Configlet
   before trying the network, so long as they assert physical presence.
   For instance, a removable USB drive or a near-field communication
   mechanism.  Further, this draft does not require Configlets to be
   signed, if loaded via a mechanism that asserts physical presence. or
   require those Configlets to have the device's unique identifier value
   set.  All of these relaxations in Security are deemed acceptable
   because physical presence should only be accessible to trusted
   parties.







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   This draft allows devices to use insecure schemes when doing a
   Configuration Server lookup.  This is deemed acceptable because the
   Configlet is tamper-proof, due to being signed, only confidentiality
   is lost.

   This draft entails the device having an X.509 certificate that is
   used by the NMS to authenticate the device.  This certificate and
   every certificate in the chain leading to the well known trust
   anchor, should have a expiration date greater than the device's
   useful life expectancy.  Given the long-lived nature of these device
   certificates, it is paramount to use a strong key length (e.g.,
   512-bit ECC).  Configlet Signers should deploy Online Certificate
   State Protocol (OCSP) responders or CRL Distribution Points (CDP) to
   revoke certificates in case necessary.

   This draft mentions using the device's serial number as its unique
   identifier in its entity certificate.  This is because serial numbers
   are ubiquitous and prominently contained in invoices and on labels
   affixed to devices and their packaging.  That said, serial numbers
   many times encode revealing information, such as the device's model
   number, manufacture date, and/or sequence number.  Knowledge of this
   information may provide an adversary with details needed to launch an
   attack.  To address this concern, the certificate could contain the
   hash of the serial number instead, which the NMS could also compute,
   but doing so is much less intuitive and raises questions if it is
   just security through obscurity.

   It is paramount the device manufacturer ensures the integrity of the
   device's list of trust anchors.  It should not be possible for anyone
   other than the manufacturer be able to modify the list of trust
   anchors.  One way to achieve this to sign the list of trust anchors
   with a private key known only to the manufacturer, and for the
   matching public key to be stored on tamper-resistant read-only media.

7.  IANA Considerations

   None

8.  Acknowledgements

   The authors would like to thank Russ Mundy and Wes Hardaker for
   brainstorming the solution presented in this draft with us during the
   IETF 87 meeting in Berlin.

9.  References

9.1.  Normative References




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

   [RFC3365]  Schiller, J., "Strong Security Requirements for Internet
              Engineering Task Force Standard Protocols ", RFC 3365,
              August 2002.

   [RFC4252]  Ylonen, T. and C. Lonvick, Ed., "The Secure Shell (SSH)
              Authentication Protocol ", RFC 4252, January 2006.

   [RFC5539bis]
              Badra, M. and A. Luchuk, "Using the NETCONF Protocol over
              Transport Layer Security (TLS) ", RFC 5539, March 2011.

   [RFC6187]  Igoe, K. and D. Stebila, "X.509v3 Certificates for Secure
              Shell Authentication ", RFC 6187, March 2011.

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

   [REVERSE-SSH]
              Watsen, K., "Reverse SSH", June 2013.

   [XMLSIG]   , "XML Signature Syntax and Processing", June 2008.

9.2.  Informative References

   [TR069]    The Broadband Forum, ., "TR-069 Amendment 3, CPE WAN
              Management Protocol ", November 2010.

   [draft-hanna-zeroconf-seccfg-00]
              Hanna, ., "Configuring Security Parameters in Small
              Devices ", January 2002.

Appendix A.  Examples

A.1.  Signed Configlet

   This example illustrates a Configlet configuring both a local user
   account and reverse-SSH.  This Configlet includes both the Configlet
   Signer's certificate as well as an Intermediate certificate.  Note
   that '\' characters have been added for formatting reasons.

   <?xml version="1.0"?>
   <configlet xmlns="urn:ietf:params:xml:ns:yang:ietf-netconf-zerotouch">
     <!-- from ietf-system.yang -->
     <system>



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       <authentication>
         <user>
           <name>admin</name>
           <ssh-key>
             <name>admin's rsa ssh host-key</name>
             <algorithm>ssh-rsa</algorithm>
             <key-data>AAAAB3NzaC1yc2EAAAADAQABAAABAQDeJMV8zrtsi8CgEsRC
             jCzfve2m6zD3awSBPrh7ICggLQvHVbPL89eHLuecStKL3HrEgXaI/O2Mwj
             E1lG9YxLzeS5p2ngzK61vikUSqfMukeBohFTrDZ8bUtrF+HMLlTRnoCVcC
             WAw1lOr9IDGDAuww6G45gLcHalHMmBtQxKnZdzU9kx/fL3ZS5G76Fy6sA5
             vg7SLqQFPjXXft2CAhin8xwYRZy6r/2N9PMJ2Dnepvq4H2DKqBIe340jWq
             EIuA7LvEJYql4unq4Iog+/+CiumTkmQIWRgIoj4FCzYkO9NvRE6fOSLLf6
             gakWVOZZgQ8929uWjCWlGlqn2mPibp2Go1</key-data>
           </ssh-key>
         </user>
       </authentication>
     </system>
     <!-- from ietf-netconf-server.yang -->
     <netconf-server>
       <ssh>
         <call-home>
           <applications>
             <application>
               <name>config-mgr</name>
               <description>
                This entry requests the device to periodically
                connect to the Configuration Manager application
             </description>
               <servers>
                 <server>
                   <address>config-mgr1.example.com</address>
                 </server>
                 <server>
                   <address>config-mgr2.example.com</address>
                 </server>
               </servers>
               <connection-type>
                 <periodic>
                   <timeout-mins>5</timeout-mins>
                   <linger-secs>10</linger-secs>
                 </periodic>
               </connection-type>
               <reconnect-strategy>
                 <start-with>last-connected</start-with>
                 <interval-secs>10</interval-secs>
                 <count-max>3</count-max>
               </reconnect-strategy>
               <host-keys>



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                 <host-key>
                   <name>ssh_host_key_cert</name>
                 </host-key>
                 <host-key>
                   <name>ssh_host_key_cert2</name>
                 </host-key>
               </host-keys>
             </application>
           </applications>
         </call-home>
       </ssh>
     </netconf-server>
     <Signature xmlns="http://www.w3.org/2000/09/xmldsig#">
       <SignedInfo>
         <CanonicalizationMethod
           Algorithm="http://www.w3.org/2001/10/xml-exc-c14n#"/>
         <SignatureMethod
           Algorithm="http://www.w3.org/2000/09/xmldsig#rsa-sha1"/>
         <Reference>
           <Transforms>
             <Transform
               Algorithm=\
               "http://www.w3.org/2000/09/xmldsig#enveloped-signature"/>
           </Transforms>
           <DigestMethod
             Algorithm="http://www.w3.org/2000/09/xmldsig#sha1"/>
           <DigestValue>2xlFdlVifb1snGBLJuEZYrLjSUQ=</DigestValue>
         </Reference>
       </SignedInfo>
       <SignatureValue>\
   HUx3S7TZXGJGUhazWGRSB9CBMZ0T+tTrB1fOnTcKi9wU4UOnSw5KMWDvOVwc6ldM
   UIOJIuJigWhSkn+VvWSWz6qy7LTYIywNcxDyghMvmMXfoRXETpL+qCDxribMi4VW
   mVhEw1oe83kJt7W/0DJUE7FFKRUhPjy9EgxpQX/7WdKSK+4f2uYkSpq2UumW3DIU
   LeK9vNRVQBbhmcF3zZWANmwKH5V4WeQimwWE497AeSYWgSImSetADI0NvvXfBZjx
   JqzFEaYLNz8IB0ZVY+w14s1RZbN7YmxhN1R3q52wWvHjR2SylR/Z5BpIhYoDeKoD
   HMQMf3HZL06Hm5S8r8rgGg==</SignatureValue>
       <KeyInfo>
         <X509Data>
           <X509Certificate>\
   MIIFKjCCBBKgAwIBAgIBAjANBgkqhkiG9w0BAQsFADAwMRMwEQYDVQQKFApUUE1f
   VmVuZG9yMRkwFwYDVQQDFBBKdW5pcGVyX1hYWFhYX0NBMB4XDTEzMTAyMDE2MjIx
   MFoXDTE0MTAyMDE2MjIxMFowKzETMBEGA1UEChQKVFBNX1ZlbmRvcjEUMBIGA1UE
   AxQLY2hpcF8wMDAwMDEwggEiMA0GCSqGSIb3DQEBAQUAA4IBDwAwggEKAoIBAQDf
   4hyWqFsf801sZYJQBJ0PB4cHmlnPNOs9pv3QCCB1PzlYhfcDOygVmqhzZjPY+t7q
   ZTjPs/E8n5X4dd0DkR80uc4MWmzc40Pz2HAW6GQ2mo+eUYzXUqQFbi3EkqrzddZk
   gRi6vuadMkAcJH8ugYR+cbw/LlpXhIy2A5fUh4JP7Y9l1wABTbK8eGhF9cvGxBYR
   +KqZJycoV6aaIvD/0NO1CNSaGeAJXXxXWoRF5E6HVKsolTHPPdi+40BmYrCuuWy6
   1ybCIP5uZZ7Oza4j0n/fPb6SEqEa0I1zUEWlFQMZYsBClNY5TzWHNgQ5dPJO2qgx



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   PONwnLIsx46DlAzlpFpXAgMBAAGjggJSMIICTjAMBgNVHRMBAf8EAjAAMIGTBgNV
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   feDp86jGN6348H+z9CzXUSbyOn6utIxN0SvVESxx</X509Certificate>
           <X509Certificate>\
   MIIExTCCA62gAwIBAgIBATANBgkqhkiG9w0BAQsFADCBqjELMAkGA1UEBhMCVVMx
   EzARBgNVBAgTCkNhbGlmb3JuaWExEjAQBgNVBAcTCVN1bm55dmFsZTEZMBcGA1UE
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   ASIwDQYJKoZIhvcNAQEBBQADggEPADCCAQoCggEBAK+D34JQ/tsWv5SZ5L2TF7u7
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   fsHY2CtQaP/r8hT/8TjPB4mJpbuG1P/BpIAXtBC+hqggwAnNpVfcAxReozzoFCcC
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   BfXhJE4VOjAEQ8w+Sftu1lu6rJZr3ctSLg==</X509Certificate>
         </X509Data>
       </KeyInfo>



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     </Signature>
   </configlet>

Appendix B.  Change Log

B.1.  00 to 01

      Complete re-write.  Switched from using signed DNS records using
      DNSSEC to using signed YANG-defined XML files using XML Signature.
      This update took into a lot a feedback from both operators and
      vendors.

Appendix C.  Open Issues

C.1.  How to best structure the Configlet YANG module?

   The current YANG module must redefine parts of the "ietf-system" and
   "ietf-netconf-server" modules.  Also, when referencing parts that it
   can, the YANG module unnecessarily includes parts it doesn't need,
   such as configuring the device to listen for inbound connections.
   Ideally "deviation" statements could be used to delete the unwanted
   sub-trees.

C.2.  Should Configlets always be signed?

   This drafts states that Configlets don't have to be signed when
   loaded through a mechanism that asserts physical presence.  However,
   some have voiced concern, saying that no possible backdoor should be
   allowed.

Authors' Addresses

   Kent Watsen
   Juniper Networks

   EMail: kwatsen@juniper.net


   Stephen Hanna
   Juniper Networks

   EMail: shanna@juniper.net


   Joe Marcus Clarke
   Cisco Systems

   EMail: jclarke@cisco.com



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   Mikael Abrahamsson
   T-Systems

   EMail: "mikael.abrahamsson@t-systems.se















































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