



Internet Engineering Task Force (IETF)                             Q. Wu
Request for Comments: 8808                                        Huawei
Category: Standards Track                                     B. Lengyel
ISSN: 2070-1721                                         Ericsson Hungary
                                                                  Y. Niu
                                                                  Huawei
                                                             August 2020


             A YANG Data Model for Factory Default Settings

Abstract

   This document defines a YANG data model with the "factory-reset" RPC
   to allow clients to reset a server back to its factory default
   condition.  It also defines an optional "factory-default" datastore
   to allow clients to read the factory default configuration for the
   device.

   The YANG data model in this document conforms to the Network
   Management Datastore Architecture (NMDA) defined in RFC 8342.

Status of This Memo

   This is an Internet Standards Track document.

   This document is a product of the Internet Engineering Task Force
   (IETF).  It represents the consensus of the IETF community.  It has
   received public review and has been approved for publication by the
   Internet Engineering Steering Group (IESG).  Further information on
   Internet Standards is available in Section 2 of RFC 7841.

   Information about the current status of this document, any errata,
   and how to provide feedback on it may be obtained at
   https://www.rfc-editor.org/info/rfc8808.

Copyright Notice

   Copyright (c) 2020 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
   (https://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
   described in the Simplified BSD License.

Table of Contents

   1.  Introduction
     1.1.  Terminology
   2.  "Factory-Reset" RPC
   3.  "Factory-Default" Datastore
   4.  YANG Module
   5.  IANA Considerations
   6.  Security Considerations
   7.  References
     7.1.  Normative References
     7.2.  Informative References
   Acknowledgements
   Contributors
   Authors' Addresses

1.  Introduction

   This document defines a YANG data model and associated mechanism to
   reset a server to its factory default contents.  This mechanism may
   be used, for example, when the existing configuration has major
   errors and so restarting the configuration process from scratch is
   the best option.

   A "factory-reset" remote procedure call (RPC) is defined within the
   YANG data model.  When resetting a device, all previous configuration
   settings will be lost and replaced by the factory default contents.

   In addition, an optional "factory-default" read-only datastore is
   defined within the YANG data model.  This datastore contains the data
   to replace the contents of implemented read-write conventional
   configuration datastores at reset and can also be used in the
   <get-data> operation.

   The YANG data model in this document conforms to the Network
   Management Datastore Architecture defined in [RFC8342].

1.1.  Terminology

   The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT",
   "SHOULD", "SHOULD NOT", "RECOMMENDED", "NOT RECOMMENDED", "MAY", and
   "OPTIONAL" in this document are to be interpreted as described in
   BCP 14 [RFC2119] [RFC8174] when, and only when, they appear in all
   capitals, as shown here.

   The following terms are defined in [RFC8342] and [RFC7950] and are
   not redefined here:

   *  server

   *  startup configuration datastore

   *  candidate configuration datastore

   *  running configuration datastore

   *  intended configuration datastore

   *  operational state datastore

   *  conventional configuration datastore

   *  datastore schema

   *  RPC operation

   This document defines the following term:

   "factory-default" datastore:  A read-only configuration datastore
      holding a preset initial configuration that is used to initialize
      the configuration of a server.  This datastore is referred to as
      "<factory-default>".

2.  "Factory-Reset" RPC

   This document introduces a new "factory-reset" RPC.  Upon receiving
   the RPC:

   *  All supported conventional read-write configuration datastores
      (i.e., <running>, <startup>, and <candidate>) are reset to the
      contents of <factory-default>.

   *  Read-only datastores receive their contents from other datastores
      (e.g., <intended> gets its contents from <running>).

   *  All data in any dynamic configuration datastores MUST be
      discarded.

   *  The contents of the <operational> datastore MUST reflect the
      operational state of the device after applying the factory default
      configuration.

   In addition, the "factory-reset" RPC MUST restore nonvolatile storage
   to factory condition.  Depending on the system, this may entail
   deleting dynamically generated files, such as those containing keys
   (e.g., /etc/ssl/private), certificates (e.g., /etc/ssl), logs (e.g.,
   /var/log), and temporary files (e.g., /tmp/*).  Any other
   cryptographic keys that are part of the factory-installed image will
   be retained (such as an Initial Device Identifier (IDevID)
   certificate [BRSKI]).  When this process includes security-sensitive
   data such as cryptographic keys or passwords, it is RECOMMENDED to
   perform the deletion in as thorough a manner as possible (e.g.,
   overwriting the physical storage medium with zeros and/or random bits
   for repurposing or end-of-life (EOL) disposal) to reduce the risk of
   the sensitive material being recoverable.  The "factory-reset" RPC
   MAY also be used to trigger some other resetting tasks such as
   restarting the node or some of the software processes.

   Note that operators should be aware that since all read-write
   datastores are immediately reset to factory default, the device may
   become unreachable as a host on the network.  It is important to
   understand how a given vendor's device will behave after the RPC is
   executed.  Implementors SHOULD reboot the device and get it properly
   configured or otherwise restart processes needed to bootstrap it.

3.  "Factory-Default" Datastore

   Following the guidelines for defining datastores in Appendix A of
   [RFC8342], this document introduces a new optional datastore resource
   named "factory-default" that represents a preset initial
   configuration that can be used to initialize the configuration of a
   server.  A device MAY implement the "factory-reset" RPC without
   implementing the "factory-default" datastore, which would only
   eliminate the ability to programmatically determine the factory
   default configuration.

   Name:  "factory-default".

   YANG modules:  The "factory-default" datastore schema MUST be either
      (1) the same as the conventional configuration datastores or
      (2) a subset of the datastore schema for the conventional
      configuration datastores.

   YANG nodes:  All "config true" data nodes.

   Management operations:  The contents of the datastore is set by the
      server in an implementation-dependent manner.  The contents cannot
      be changed by management operations via the Network Configuration
      Protocol (NETCONF), RESTCONF, the CLI, etc., unless specialized,
      dedicated operations are provided.  The datastore can be read
      using the standard NETCONF/RESTCONF protocol operations.  The
      "factory-reset" operation copies the factory default contents to
      <running> and, if present, <startup> and/or <candidate>.  The
      contents of these datastores is then propagated automatically to
      any other read-only datastores, e.g., <intended> and
      <operational>.

   Origin:  This document does not define a new origin identity, as it
      does not interact with the <operational> datastore.

   Protocols:  RESTCONF, NETCONF, and other management protocols.

   Defining YANG module:  "ietf-factory-default".

   The contents of <factory-default> are defined by the device vendor
   and MUST persist across device restarts.  If supported, the "factory-
   default" datastore MUST be included in the list of datastores in the
   YANG library [RFC8525].

4.  YANG Module

   This module uses the "datastore" identity [RFC8342] and the
   "default-deny-all" extension statement from [RFC8341].

   <CODE BEGINS> file "ietf-factory-default@2020-08-31.yang"
      module ietf-factory-default {
        yang-version 1.1;
        namespace "urn:ietf:params:xml:ns:yang:ietf-factory-default";
        prefix fd;

        import ietf-datastores {
          prefix ds;
          reference
            "RFC 8342: Network Management Datastore Architecture
             (NMDA)";
        }
        import ietf-netconf-acm {
          prefix nacm;
          reference
            "RFC 8341: Network Configuration Access Control Model";
        }

        organization
          "IETF Network Modeling (netmod) Working Group";
        contact
          "WG Web:   <https://datatracker.ietf.org/wg/netmod/>
           WG List:  <mailto:netmod@ietf.org>

           Editor:   Qin Wu
                     <mailto:bill.wu@huawei.com>

           Editor:   Balazs Lengyel
                     <mailto:balazs.lengyel@ericsson.com>

           Editor:   Ye Niu
                     <mailto:niuye@huawei.com>";
        description
          "This module provides functionality to reset a server to its
           factory default configuration and, when supported, to
           discover the factory default configuration contents
           independently of resetting the server.

           Copyright (c) 2020 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
           (https://trustee.ietf.org/license-info).

           This version of this YANG module is part of RFC 8808; see the
           RFC itself for full legal notices.";

        revision 2020-08-31 {
          description
            "Initial revision.";
          reference
            "RFC 8808: A YANG Data Model for Factory Default Settings";
        }

        feature factory-default-datastore {
          description
            "Indicates that the factory default configuration is
             available as a datastore.";
        }

        rpc factory-reset {
          nacm:default-deny-all;
          description
            "The server resets all datastores to their factory
             default contents and any nonvolatile storage back to
             factory condition, deleting all dynamically
             generated files, including those containing keys,
             certificates, logs, and other temporary files.

             Depending on the factory default configuration, after
             being reset, the device may become unreachable on the
             network.";
        }

        identity factory-default {
          if-feature "factory-default-datastore";
          base ds:datastore;
          description
            "This read-only datastore contains the factory default
             configuration for the device that will be used to replace
             the contents of the read-write conventional configuration
             datastores during a 'factory-reset' RPC operation.";
        }
      }
   <CODE ENDS>

5.  IANA Considerations

   IANA has registered the following URI in the "ns" subregistry within
   the "IETF XML Registry" [RFC3688]:

   URI:  urn:ietf:params:xml:ns:yang:ietf-factory-default
   Registrant Contact:  The IESG.
   XML:  N/A; the requested URI is an XML namespace.

   IANA has registered the following YANG module in the "YANG Module
   Names" subregistry [RFC6020] within the "YANG Parameters" registry:

   Name:  ietf-factory-default
   Namespace:  urn:ietf:params:xml:ns:yang:ietf-factory-default
   Prefix:  fd
   Reference:  8808

6.  Security Considerations

   The YANG module specified in this document defines a schema for data
   that is designed to be accessed via network management protocols such
   as NETCONF [RFC6241] or RESTCONF [RFC8040].  The lowest NETCONF layer
   is the secure transport layer, and the mandatory-to-implement secure
   transport is Secure Shell (SSH) [RFC6242].  The lowest RESTCONF layer
   is HTTPS, and the mandatory-to-implement secure transport is TLS
   [RFC8446].

   The Network Configuration Access Control Model (NACM) [RFC8341]
   provides the means to restrict access for particular NETCONF or
   RESTCONF users to a preconfigured subset of all available NETCONF or
   RESTCONF protocol operations and content.

   Access to the "factory-reset" RPC operation and factory default
   values of all configuration data nodes within the "factory-default"
   datastore is considered sensitive and therefore has been restricted
   by using the "default-deny-all" access control statement defined in
   [RFC8341].

   The "factory-reset" RPC can prevent any further management of the
   device when the server is reset back to its factory default
   condition, e.g., the session and client configurations are included
   in the factory default contents or treated as dynamic files in
   nonvolatile storage and overwritten by the "factory-reset" RPC.

   The operational disruption caused by setting the configuration to
   factory default contents or the lack of appropriate security control
   on the factory default configuration varies greatly, depending on the
   implementation and current configuration.

   The nonvolatile storage is expected to be wiped clean and reset back
   to the factory default state, but there is no guarantee that the data
   is wiped clean according to any particular data-cleansing standard,
   and the owner of the device MUST NOT rely on any sensitive data
   (e.g., private keys) being forensically unrecoverable from the
   device's nonvolatile storage after a "factory-reset" RPC has been
   invoked.

7.  References

7.1.  Normative References

   [RFC2119]  Bradner, S., "Key words for use in RFCs to Indicate
              Requirement Levels", BCP 14, RFC 2119,
              DOI 10.17487/RFC2119, March 1997,
              <https://www.rfc-editor.org/info/rfc2119>.

   [RFC3688]  Mealling, M., "The IETF XML Registry", BCP 81, RFC 3688,
              DOI 10.17487/RFC3688, January 2004,
              <https://www.rfc-editor.org/info/rfc3688>.

   [RFC6020]  Bjorklund, M., Ed., "YANG - A Data Modeling Language for
              the Network Configuration Protocol (NETCONF)", RFC 6020,
              DOI 10.17487/RFC6020, October 2010,
              <https://www.rfc-editor.org/info/rfc6020>.

   [RFC6241]  Enns, R., Ed., Bjorklund, M., Ed., Schoenwaelder, J., Ed.,
              and A. Bierman, Ed., "Network Configuration Protocol
              (NETCONF)", RFC 6241, DOI 10.17487/RFC6241, June 2011,
              <https://www.rfc-editor.org/info/rfc6241>.

   [RFC6242]  Wasserman, M., "Using the NETCONF Protocol over Secure
              Shell (SSH)", RFC 6242, DOI 10.17487/RFC6242, June 2011,
              <https://www.rfc-editor.org/info/rfc6242>.

   [RFC7950]  Bjorklund, M., Ed., "The YANG 1.1 Data Modeling Language",
              RFC 7950, DOI 10.17487/RFC7950, August 2016,
              <https://www.rfc-editor.org/info/rfc7950>.

   [RFC8040]  Bierman, A., Bjorklund, M., and K. Watsen, "RESTCONF
              Protocol", RFC 8040, DOI 10.17487/RFC8040, January 2017,
              <https://www.rfc-editor.org/info/rfc8040>.

   [RFC8174]  Leiba, B., "Ambiguity of Uppercase vs Lowercase in RFC
              2119 Key Words", BCP 14, RFC 8174, DOI 10.17487/RFC8174,
              May 2017, <https://www.rfc-editor.org/info/rfc8174>.

   [RFC8341]  Bierman, A. and M. Bjorklund, "Network Configuration
              Access Control Model", STD 91, RFC 8341,
              DOI 10.17487/RFC8341, March 2018,
              <https://www.rfc-editor.org/info/rfc8341>.

   [RFC8342]  Bjorklund, M., Schoenwaelder, J., Shafer, P., Watsen, K.,
              and R. Wilton, "Network Management Datastore Architecture
              (NMDA)", RFC 8342, DOI 10.17487/RFC8342, March 2018,
              <https://www.rfc-editor.org/info/rfc8342>.

   [RFC8446]  Rescorla, E., "The Transport Layer Security (TLS) Protocol
              Version 1.3", RFC 8446, DOI 10.17487/RFC8446, August 2018,
              <https://www.rfc-editor.org/info/rfc8446>.

   [RFC8525]  Bierman, A., Bjorklund, M., Schoenwaelder, J., Watsen, K.,
              and R. Wilton, "YANG Library", RFC 8525,
              DOI 10.17487/RFC8525, March 2019,
              <https://www.rfc-editor.org/info/rfc8525>.

7.2.  Informative References

   [BRSKI]    Pritikin, M., Richardson, M. C., Eckert, T., Behringer, M.
              H., and K. Watsen, "Bootstrapping Remote Secure Key
              Infrastructures (BRSKI)", Work in Progress, Internet-
              Draft, draft-ietf-anima-bootstrapping-keyinfra-43, 7
              August 2020, <https://tools.ietf.org/html/draft-ietf-
              anima-bootstrapping-keyinfra-43>.

Acknowledgements

   Thanks to Juergen Schoenwaelder, Ladislav Lhotka, Alex Campbell, Joe
   Clarke, Robert Wilton, Kent Watsen, Joel Jaeggli, Lou Berger, Andy
   Bierman, Susan Hares, Benjamin Kaduk, Stephen Kent, Stewart Bryant,
   Éric Vyncke, Murray Kucherawy, Roman Danyliw, Tony Przygienda, and
   John Heasley for reviewing, and providing important input to, this
   document.

Contributors

   Rohit R Ranade
   Huawei

   Email: rohitrranade@huawei.com


Authors' Addresses

   Qin Wu
   Huawei
   Yuhua District
   101 Software Avenue
   Nanjing
   Jiangsu, 210012
   China

   Email: bill.wu@huawei.com


   Balazs Lengyel
   Ericsson Hungary
   Budapest
   Magyar Tudosok korutja 11
   1117
   Hungary

   Phone: +36-70-330-7909
   Email: balazs.lengyel@ericsson.com


   Ye Niu
   Huawei

   Email: niuye@huawei.com
