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An HTTPS-based Transport for YANG Notifications
draft-ietf-netconf-https-notif-11

Document Type Active Internet-Draft (netconf WG)
Authors Mahesh Jethanandani , Kent Watsen
Last updated 2022-07-19
Replaces draft-mahesh-netconf-https-notif
Stream Internet Engineering Task Force (IETF)
Intended RFC status Proposed Standard
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Additional resources Yang catalog entry for ietf-https-notif@2020-10-21.yang
Yang catalog entry for ietf-sub-notif-recv-list@2020-10-21.yang
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draft-ietf-netconf-https-notif-11
NETCONF                                                M.J. Jethanandani
Internet-Draft                                            Kloud Services
Intended status: Standards Track                             K.W. Watsen
Expires: 20 January 2023                                 Watsen Networks
                                                            19 July 2022

            An HTTPS-based Transport for YANG Notifications
                   draft-ietf-netconf-https-notif-11

Abstract

   This document defines a protocol for sending notifications over
   HTTPS.  YANG modules for configuring publishers are also defined.
   Examples are provided illustrating how to configure various
   publishers.

   This document requires that the publisher is a "server" (e.g., a
   NETCONF or RESTCONF server), but does not assume that the receiver is
   a server.

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 https://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 20 January 2023.

Copyright Notice

   Copyright (c) 2022 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

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   extracted from this document must include Revised BSD License text as
   described in Section 4.e of the Trust Legal Provisions and are
   provided without warranty as described in the Revised BSD License.

Table of Contents

   1.  Introduction  . . . . . . . . . . . . . . . . . . . . . . . .   3
     1.1.  Applicability Statement . . . . . . . . . . . . . . . . .   3
     1.2.  Note to RFC Editor  . . . . . . . . . . . . . . . . . . .   3
     1.3.  Abbreviations . . . . . . . . . . . . . . . . . . . . . .   4
     1.4.  Terminology . . . . . . . . . . . . . . . . . . . . . . .   4
       1.4.1.  Terms Imported from RFC 8639  . . . . . . . . . . . .   4
   2.  Overview of Publisher to Receiver Interaction . . . . . . . .   4
   3.  Discovering a Receiver's Capabilities . . . . . . . . . . . .   5
     3.1.  Applicability . . . . . . . . . . . . . . . . . . . . . .   5
     3.2.  Request . . . . . . . . . . . . . . . . . . . . . . . . .   6
     3.3.  Response  . . . . . . . . . . . . . . . . . . . . . . . .   6
     3.4.  Example . . . . . . . . . . . . . . . . . . . . . . . . .   6
   4.  Sending Event Notifications . . . . . . . . . . . . . . . . .   7
     4.1.  Request . . . . . . . . . . . . . . . . . . . . . . . . .   8
     4.2.  Response  . . . . . . . . . . . . . . . . . . . . . . . .   8
     4.3.  Example . . . . . . . . . . . . . . . . . . . . . . . . .   8
   5.  The "ietf-subscribed-notif-receivers" Module  . . . . . . . .   9
     5.1.  Data Model Overview . . . . . . . . . . . . . . . . . . .   9
     5.2.  YANG Module . . . . . . . . . . . . . . . . . . . . . . .   9
   6.  The "ietf-https-notif-transport" Module . . . . . . . . . . .  12
     6.1.  Data Model Overview . . . . . . . . . . . . . . . . . . .  12
     6.2.  YANG module . . . . . . . . . . . . . . . . . . . . . . .  14
   7.  Security Considerations . . . . . . . . . . . . . . . . . . .  17
   8.  IANA Considerations . . . . . . . . . . . . . . . . . . . . .  18
     8.1.  The "IETF XML" Registry . . . . . . . . . . . . . . . . .  18
     8.2.  The "YANG Module Names" Registry  . . . . . . . . . . . .  18
     8.3.  The "Capabilities for HTTPS Notification Receivers"
           Registry  . . . . . . . . . . . . . . . . . . . . . . . .  19
   9.  References  . . . . . . . . . . . . . . . . . . . . . . . . .  20
     9.1.  Normative references  . . . . . . . . . . . . . . . . . .  20
     9.2.  Informative references  . . . . . . . . . . . . . . . . .  21
   Appendix A.  Configuration Examples . . . . . . . . . . . . . . .  22
     A.1.  Using Subscribed Notifications (RFC 8639) . . . . . . . .  22
     A.2.  Not Using Subscribed Notifications  . . . . . . . . . . .  24
   Acknowledgements  . . . . . . . . . . . . . . . . . . . . . . . .  26
   Authors' Addresses  . . . . . . . . . . . . . . . . . . . . . . .  26

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1.  Introduction

   This document defines a protocol for sending notifications over
   HTTPS.  Using HTTPS maximizes transport-level interoperability, while
   allowing for a variety of encoding options.  This document defines
   support for JSON and XML; future efforts may define support for other
   encodings (e.g., binary).

   This document requires that the publisher is a "server" (e.g., a
   NETCONF or RESTCONF server), but does not assume that the receiver is
   a NETCONF or RESTCONF server.  It does expect the receiver to be an
   HTTPS server to receive the notfications.

   This document also defines two YANG 1.1 [RFC7950] modules that extend
   the data model defined in Subscription to YANG Notifications
   [RFC8639], enabling the configuration of HTTPS-based receivers.

   An example module illustrating the configuration of a publisher not
   using the data model defined in RFC 8639 is also provided.

   Configured subscriptions enable a server, acting as a publisher of
   notifications, to proactively push notifications to external
   receivers without the receivers needing to first connect to the
   server, as is the case with dynamic subscriptions.

1.1.  Applicability Statement

   While the YANG modules have been defined as an augmentation of
   Subscription to YANG Notifications [RFC8639], the notification method
   defined in this document MAY be used outside of Subscription to YANG
   Notifications [RFC8639] by using some of the definitions from this
   module along with the grouping defined in Groupings for HTTP Clients
   and Servers [I-D.ietf-netconf-http-client-server].  For an example on
   how that can be done, see Section A.2.

1.2.  Note to RFC Editor

   This document uses several placeholder values throughout the
   document.  Please replace them as follows and remove this section
   before publication.

   RFC XXXX, where XXXX is the number assigned to this document at the
   time of publication.

   RFC YYYY, where YYYY is the number assigned to
   [I-D.ietf-netconf-http-client-server].

   2022-07-18 with the actual date of the publication of this document.

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1.3.  Abbreviations

            +=========+======================================+
            | Acronym | Expansion                            |
            +=========+======================================+
            | HTTP    | Hypertext Transfer Protocol          |
            +---------+--------------------------------------+
            | HTTPS   | Hyper Text Transport Protocol Secure |
            +---------+--------------------------------------+
            | TCP     | Transmission Control Protocol        |
            +---------+--------------------------------------+
            | TLS     | Transport Layer Security             |
            +---------+--------------------------------------+

                                 Table 1

1.4.  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.

1.4.1.  Terms Imported from RFC 8639

   The following terms are defined in Subscription to YANG Notifications
   [RFC8639].

   *  Subscribed Notifications

2.  Overview of Publisher to Receiver Interaction

   The protocol consists of two HTTP-based target resources presented by
   the receiver.  These two resources share a common prefix that the
   publisher must know.  If the data model in section 6.2 is used, this
   common prefix is defined by the "path" leaf in the "http-client-
   parameters" container.

   *  "capabilities": A target resource enabling the publisher to
      discover what optional capabilities a receiver supports.
      Publishers SHOULD query this target before sending any
      notifications or if ever an error occurs.

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   *  "relay-notifications": A target resource enabling the publisher to
      send one or more notification to a receiver.  This document
      defines support for sending only one notification per message; a
      future effort MAY extend the protocol to send multiple
      notifications per message.

   The protocol is illustrated in the diagram below:

             -------------                      --------------
             | Publisher |                      | Receiver   |
             -------------                      --------------

        Send HTTPS GET message    ------>
        to discover receiver's
        capabilities

                                  <------    Send 200 (OK) containing
                                             capabilities supported
                                             by the receiver

   +-- For Each Notification (MAY be pipelined) ---------------------+
   |                                                                 |
   |    Send HTTPS POST message   ------>                            |
   |    with YANG defined                                            |
   |    notification                                                 |
   |                                                                 |
   |                              <------    Send 204 (No Content)   |
   +-----------------------------------------------------------------+

   Note that, for RFC 8639 configured subscriptions, the very first
   notification must be the "subscription-started" notification.

   The POST messages MAY be "pipelined" (not illustrated in the diagram
   above), whereby multiple notifications are sent without waiting for
   the HTTP response for a previous POST.

3.  Discovering a Receiver's Capabilities

3.1.  Applicability

   For publishers using Subscription to YANG Notifications [RFC8639],
   dynamic discovery of a receiver's supported encoding is necessary
   only when the "/subscriptions/subscription/encoding" leaf is not
   configured, per the "encoding" leaf's description statement in the
   "ietf-subscribed-notification" module.

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3.2.  Request

   To learn the capabilities of a receiver, a publisher can issue an
   HTTPS GET request to the "capabilities" resource (see Section 2) on
   the receiver with "Accept" header set using the "application/xml"
   and/or "application/json" media-types, with the latter as mandatory
   to implement, and the default in case the type is not specified.

3.3.  Response

   The receiver responds with a "200 (OK)" message, having the "Content-
   Type" header set to either "application/xml" or "application/json"
   (which ever was selected), and containing in the response body a list
   of the receiver's capabilities encoded in the selected format.

   Even though a YANG module is not defined for this interaction, the
   response body MUST conform to the following YANG-modeled format:

   container receiver-capabilities {
     description
       "A container for a list of capabilities supported by
        the receiver.";
     leaf-list receiver-capability {
       type "inet:uri";
       description
         "A capability supported by the receiver.  A partial list of
          capabilities is defined in the 'Capabilities for HTTPS
          Notification Receivers' registry (see RFC XXXX). Additional
          custom capabilities MAY be defined.";
     }
   }

   As it is possible that the receiver may return custom capability
   URIs, the publisher MUST ignore any capabilities that it does not
   recognize.

3.4.  Example

   The publisher can send the following request to learn the receiver
   capabilities.  In this example, the "Accept" states that the
   publisher wants to receive the capabilities response in XML but, if
   not supported, then in JSON.

   GET /some/path/capabilities HTTP/1.1
   Host: example.com
   Accept: application/xml, application/json

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   If the receiver is able to reply using "application/xml", and
   assuming it is able to receive JSON and XML encoded notifications,
   and it is able to process the RFC 8639 state machine, the response
   might look like this:

   HTTP/1.1 200 OK
   Date: Wed, 26 Feb 2020 20:33:30 GMT
   Server: example-server
   Cache-Control: no-cache
   Content-Type: application/xml
   Content-Length: nnn

   <receiver-capabilities>
     <receiver-capability>\
       urn:ietf:capability:https-notif-receiver:encoding:json\
     </receiver-capability>
     <receiver-capability>\
       urn:ietf:capability:https-notif-receiver:encoding:xml\
     </receiver-capability>
     <receiver-capability>\
       urn:ietf:capability:https-notif-receiver:sub-notif\
     </receiver-capability>
   </receiver-capabilities>

   If the receiver is unable to reply using "application/xml", the
   response might look like this:

   HTTP/1.1 200 OK
   Date: Wed, 26 Feb 2020 20:33:30 GMT
   Server: example-server
   Cache-Control: no-cache
   Content-Type: application/json
   Content-Length: nnn

   {
      "receiver-capabilities": {
        "receiver-capability": [
          "urn:ietf:capability:https-notif-receiver:encoding:json",
          "urn:ietf:capability:https-notif-receiver:encoding:xml",
          "urn:ietf:capability:https-notif-receiver:sub-notif"
        ]
      }
   }

4.  Sending Event Notifications

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4.1.  Request

   The publisher sends an HTTPS POST request to the "relay-notification"
   resource (see Section 2) on the receiver with the "Content-Type"
   header set to either "application/json" or "application/xml" and a
   body containing the notification encoded using the specified format.

   XML-encoded notifications are encoded using the format defined by
   NETCONF Event Notifications [RFC5277] for XML.

   JSON-encoded notifications are encoded the same as specified in
   Section 6.4 in RESTCONF [RFC8040] with the following deviations:

   *  The notifications do not contain the "data:" prefix used by SSE.

   *  Instead of saying that, for JSON-encoding purposes, the module
      name for the "notification" element is "ietf-restconf", the module
      name will instead be "ietf-https-notif".

4.2.  Response

   The response should be "204 (No Content)".

4.3.  Example

   An XML-encoded notification might be sent as follows:

  POST /some/path/relay-notification HTTP/1.1
  Host: example.com
  Content-Type: application/xml

  <notification xmlns="urn:ietf:params:xml:ns:netconf:notification:1.0">
    <eventTime>2019-03-22T12:35:00Z</eventTime>
    <event xmlns="https://example.com/example-mod">
      <event-class>fault</event-class>
      <reporting-entity>
        <card>Ethernet0</card>
      </reporting-entity>
      <severity>major</severity>
    </event>
  </notification>

   A JSON-encoded notification might be sent as follows:

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   POST /some/path/relay-notification HTTP/1.1
   Host: example.com
   Content-Type: application/json

   {
     "ietf-https-notif:notification": {
       "eventTime": "2013-12-21T00:01:00Z",
       "example-mod:event" : {
         "event-class" : "fault",
         "reporting-entity" : { "card" : "Ethernet0" },
         "severity" : "major"
       }
     }
   }

   And, in either case, the response might be as follows:

   HTTP/1.1 204 No Content
   Date: Wed, 26 Feb 2020 20:33:30 GMT
   Server: example-server

5.  The "ietf-subscribed-notif-receivers" Module

5.1.  Data Model Overview

   This YANG module augments the "ietf-subscribed-notifications" module
   to define a choice of transport types that other modules such as the
   "ietf-https-notif-transport" module can use to define a transport
   specific receiver.

   module: ietf-subscribed-notif-receivers

     augment /sn:subscriptions:
       +--rw receiver-instances
          +--rw receiver-instance* [name]
             +--rw name    string
             +--rw (transport-type)
     augment /sn:subscriptions/sn:subscription/sn:receivers/sn:receiver:
       +--rw receiver-instance-ref?   leafref

5.2.  YANG Module

   The YANG module imports Subscription to YANG Notifications [RFC8639].

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   <CODE BEGINS> file "ietf-subscribed-notif-receivers@2022-07-18.yang"
   module ietf-subscribed-notif-receivers {
     yang-version 1.1;
     namespace
       "urn:ietf:params:xml:ns:yang:ietf-subscribed-notif-receivers";
     prefix "snr";

     import ietf-subscribed-notifications {
       prefix sn;
       reference
         "RFC 8639: Subscription to YANG Notifications";
     }

     organization
       "IETF NETCONF Working Group";

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

        Authors: Mahesh Jethanandani (mjethanandani at gmail dot com)
                 Kent Watsen (kent plus ietf at watsen dot net)";

     description
       "This YANG module is implemented by Publishers implementing
        the 'ietf-subscribed-notifications' module defined in RFC 8639.

        While this module is defined in RFC XXXX, which primarily
        defines an HTTPS-based transport for notifications, this module
        is not HTTP-specific.  It is a generic extension that can be
        used by any 'notif' transport.

        This module defines two 'augment' statements.  One statement
        augments a 'container' statement called 'receiver-instances'
        into the top-level 'subscriptions' container.  The other
        statement, called 'receiver-instance-ref', augemnts a 'leaf'
        statement into each 'receiver' that references one of the
        afore mentioned receiver instances.  This indirection enables
        multiple configured subscriptions to send notifications to
        the same receiver instance.

        Copyright (c) 2022 IETF Trust and the persons identified as
        the document authors.  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 Revised BSD
        License set forth in Section 4.c of the IETF Trust's Legal
        Provisions Relating to IETF Documents

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        (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.

        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 (RFC 2119) (RFC 8174) when, and only when,
        they appear in all capitals, as shown here.";

     revision "2022-07-18" {
       description
         "Initial Version.";
       reference
         "RFC XXXX: An HTTPS-based Transport for YANG Notifications.";
     }

     augment "/sn:subscriptions" {
       container receiver-instances {
         description
           "A container for all instances of receivers.";

         list receiver-instance {
           key "name";

           leaf name {
             type string;
             description
               "An arbitrary but unique name for this receiver
                instance.";
           }

           choice transport-type {
             mandatory true;
             description
               "Choice of different types of transports used to
                send notifications.  The 'case' statements must
                be augmented in by other modules.";
           }
           description
             "A list of all receiver instances.";
         }
       }
       description
         "Augment the subscriptions container to define the
          transport type.";
     }

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     augment
       "/sn:subscriptions/sn:subscription/sn:receivers/sn:receiver" {
       leaf receiver-instance-ref {
         type leafref {
           path "/sn:subscriptions/snr:receiver-instances/" +
                "snr:receiver-instance/snr:name";
         }
         description
           "Reference to a receiver instance.";
       }
       description
         "Augment the subscriptions container to define an optional
          reference to a receiver instance.";
     }
   }
   <CODE ENDS>

6.  The "ietf-https-notif-transport" Module

6.1.  Data Model Overview

   This YANG module is a definition of a set of receivers that are
   interested in the notifications published by the publisher.  The
   module contains the TCP, TLS and HTTPS parameters that are needed to
   communicate with the receiver.  The module augments the "ietf-
   subscribed-notif-receivers" module to define a transport specific
   receiver.

   As mentioned earlier, it uses a POST method to deliver the
   notification.  The "http-receiver/tls/http-client-parameters/path"
   leaf defines the path for the resource on the receiver, as defined by
   "path-absolute" in URI Generic Syntax [RFC3986].  The user-id used by
   Network Configuration Access Control Model [RFC8341], is that of the
   receiver and is derived from the certificate presented by the
   receiver as part of "receiver-identity".

   An abridged tree diagram representing the module is shown below.

   module: ietf-https-notif-transport

     augment /sn:subscriptions/snr:receiver-instances
               /snr:receiver-instance/snr:transport-type:
       +--:(https)
          +--rw https-receiver
             +--rw (transport)
             |  +--:(tcp) {tcp-supported,not httpc:tcp-supported}?
             |  |  +--rw tcp
             |  |     +--rw tcp-client-parameters

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             |  |     |  +--rw remote-address    inet:host
             |  |     |  +--rw remote-port?      inet:port-number
             |  |     |  +--rw local-address?    inet:ip-address
             |  |     |  |       {local-binding-supported}?
             |  |     |  +--rw local-port?       inet:port-number
             |  |     |  |       {local-binding-supported}?
             |  |     |  +--rw proxy-server! {proxy-connect}?
             |  |     |  |     ...
             |  |     |  +--rw keepalives! {keepalives-supported}?
             |  |     |        ...
             |  |     +--rw http-client-parameters
             |  |        +--rw client-identity!
             |  |        |     ...
             |  |        +--rw proxy-connect! {proxy-connect}?
             |  |              ...
             |  +--:(tls) {tls-supported}?
             |     +--rw tls
             |        +--rw tcp-client-parameters
             |        |  +--rw remote-address    inet:host
             |        |  +--rw remote-port?      inet:port-number
             |        |  +--rw local-address?    inet:ip-address
             |        |  |       {local-binding-supported}?
             |        |  +--rw local-port?       inet:port-number
             |        |  |       {local-binding-supported}?
             |        |  +--rw proxy-server! {proxy-connect}?
             |        |  |     ...
             |        |  +--rw keepalives! {keepalives-supported}?
             |        |        ...
             |        +--rw tls-client-parameters
             |        |  +--rw client-identity!
             |        |  |     ...
             |        |  +--rw server-authentication
             |        |  |     ...
             |        |  +--rw hello-params {tlscmn:hello-params}?
             |        |  |     ...
             |        |  +--rw keepalives {tls-client-keepalives}?
             |        |        ...
             |        +--rw http-client-parameters
             |           +--rw client-identity!
             |           |     ...
             |           +--rw proxy-connect! {proxy-connect}?
             |           |     ...
             |           +--rw path               string
             +--rw receiver-identity {receiver-identity}?
                +--rw cert-maps
                   +--rw cert-to-name* [id]
                      +--rw id             uint32
                      +--rw fingerprint    x509c2n:tls-fingerprint

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                      +--rw map-type       identityref
                      +--rw name           string

6.2.  YANG module

   The YANG module imports A YANG Data Model for SNMP Configuration
   [RFC7407], Subscription to YANG Notifications [RFC8639], and YANG
   Groupings for HTTP Clients and HTTP Servers
   [I-D.ietf-netconf-http-client-server].

   The YANG module is shown below.

   <CODE BEGINS> file "ietf-https-notif-transport@2022-07-18.yang"
   module ietf-https-notif-transport {
     yang-version 1.1;
     namespace "urn:ietf:params:xml:ns:yang:ietf-https-notif-transport";
     prefix "hnt";

     import ietf-x509-cert-to-name {
       prefix x509c2n;
       reference
         "RFC 7407: YANG Data Model for SNMP Configuration.";
     }

     import ietf-subscribed-notifications {
       prefix sn;
       reference
         "RFC 8639: Subscription to YANG Notifications";
     }

     import ietf-subscribed-notif-receivers {
       prefix snr;
       reference
         "RFC XXXX: An HTTPS-based Transport for
                    Configured Subscriptions";
     }

     import ietf-http-client {
       prefix httpc;
       reference
         "RFC YYYY: YANG Groupings for HTTP Clients and HTTP Servers";
     }

     organization
       "IETF NETCONF Working Group";

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

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        WG List:  <netconf@ietf.org>

        Authors: Mahesh Jethanandani (mjethanandani at gmail dot com)
                 Kent Watsen (kent plus ietf at watsen dot net)";

     description
       "This YANG module is implemented by Publishers that implement
        the 'ietf-subscribed-notifications' module defined in RFC 8639.

        This module augments a 'case' statement called 'https' into
        the 'choice' statement called 'transport-type' defined
        by the 'ietf-https-notif-transport' module defined in RFC XXXX.

        Copyright (c) 2022 IETF Trust and the persons identified as
        the document authors.  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 Revised 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.

        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 (RFC 2119) (RFC 8174) when, and only when,
        they appear in all capitals, as shown here.";

     revision "2022-07-18" {
       description
         "Initial Version.";
       reference
         "RFC XXXX: An HTTPS-based Transport for YANG Notifications.";
     }

     feature receiver-identity {
       description
         "Indicates that the server supports filtering notifications
          based on the receiver's identity derived from its TLS
          certificate.";
     }

     identity https {
       base sn:transport;
       description

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         "HTTPS transport for notifications.";
     }

     grouping https-receiver-grouping {
       description
         "A grouping that may be used by other modules wishing to
          configure HTTPS-based notifications without using RFC 8639.";
       uses httpc:http-client-stack-grouping {
         refine "transport/tcp" {
           // create the logical impossibility of enabling the
           // "tcp" transport (i.e., "HTTP" without the 'S').
           if-feature "not httpc:tcp-supported";
         }
         augment "transport/tls/tls/http-client-parameters" {
           leaf path {
             type string;
             mandatory true;
             description
               "A path to the target resources.  Under this
                path the receiver must support both the 'capabilities'
                and 'relay-notification' resource targets, as described
                in RFC XXXX.";
           }
           description
             "Augmentation to add a receiver-specific path for the
              'capabilities' and 'relay-notification' resources.";
         }
       }
       container receiver-identity {
         if-feature receiver-identity;
         description
           "Maps the receiver's TLS certificate to a local identity
            enabling access control to be applied to filter out
            notifications that the receiver may not be authorized
            to view.";
         container cert-maps {
           uses x509c2n:cert-to-name;
           description
             "The cert-maps container is used by a TLS-based HTTP
              server to map the HTTPS client's presented X.509
              certificate to a 'local' username. If no matching and
              valid cert-to-name list entry is found, the publisher
              MUST close the connection, and MUST NOT not send any
              notifications over it.";
           reference
             "RFC 7407: A YANG Data Model for SNMP Configuration.";
         }
       }

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     }

     augment "/sn:subscriptions/snr:receiver-instances/" +
             "snr:receiver-instance/snr:transport-type" {
       case https {
         container https-receiver {
           description
             "The HTTPS receiver to send notifications to.";
           uses https-receiver-grouping;
         }
       }
       description
         "Augment the transport-type choice to include the 'https'
          transport.";
     }
   }
   <CODE ENDS>

7.  Security Considerations

   The YANG modules 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 NETCONF 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.

   The YANG modules in this document makes use of grouping that are
   defined in YANG Groupings for HTTP Clients and HTTP Servers
   [I-D.ietf-netconf-http-client-server], and A YANG Data Model for SNMP
   Configuration [RFC7407].  Please see the Security Considerations
   section of those documents for considerations related to sensitivity
   and vulnerability of the data nodes defined in them.

   There are a number of data nodes defined in the YANG modules that are
   writable/creatable/deletable (i.e., config true, which is the
   default).  These data nodes may be considered sensitive or vulnerable
   in some network environments.  Write operations (e.g., edit-config)
   to these data nodes without proper protection can have a negative
   effect on network operations.  These are the subtrees and data nodes
   and their sensitivity/vulnerability:

   *  The "path" node in "ietf-subscribed-notif-receivers" module can be
      modified by a malicious user to point to an invalid URI.

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   Some of the readable data nodes in the YANG modules may be considered
   sensitive or vulnerable in some network environments.  It is thus
   important to control read access (e.g., via get, get-config, or
   notification) to these data nodes.  The model does not define any
   readable subtrees and data nodes.

   Some of the RPC operations in the YANG modules may be considered
   sensitive or vulnerable in some network environments.  It is thus
   important to control access to these operations.  The model does not
   define any RPC operations.

8.  IANA Considerations

8.1.  The "IETF XML" Registry

   This document registers two URIs in the "ns" subregistry of the "IETF
   XML" registry [RFC3688].  Following the format in [RFC3688], the
   following registrations are requested:

   URI: urn:ietf:params:xml:ns:yang:ietf-subscribed-notif-receivers
   Registrant Contact: The IESG
   XML: N/A, the requested URI is an XML namespace.

   URI: urn:ietf:params:xml:ns:yang:ietf-https-notif-transport
   Registrant Contact: The IESG
   XML: N/A, the requested URI is an XML namespace.

8.2.  The "YANG Module Names" Registry

   This document registers two YANG modules in the "YANG Module Names"
   registry [RFC6020].  Following the format in [RFC6020], the following
   registrations are requested:

name:         ietf-subscribed-notif-receivers
namespace:    urn:ietf:params:xml:ns:yang:ietf-subscribed-notif-receivers
prefix:       snr
reference:    RFC XXXX

name:         ietf-https-notif-transport
namespace:    urn:ietf:params:xml:ns:yang:ietf-https-notif-transport
prefix:       hnt
reference:    RFC XXXX

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8.3.  The "Capabilities for HTTPS Notification Receivers" Registry

   Following the guidelines defined in [RFC8126], this document defines
   a new registry called "Capabilities for HTTPS Notification
   Receivers".  This registry defines capabilities that can be supported
   by HTTPS-based notification receivers.

   The following note shall be at the top of the registry:

   This registry defines capabilities that can be
   supported by HTTPS-based notification receivers.

   The fields for each registry are:

   *  URN

      -  The name of the URN (required).

      -  The URN must conform to the syntax described by [RFC8141].

      -  The URN must begin with the string "urn:ietf:capability:https-
         notif-receiver".

   *  Reference

      -  The RFC that defined the URN.

      -  The RFC must be in the form "RFC <Number>: <Title>.

   *  Description

      -  An arbitrary description of the capability (optional).

      -  The description should be no more than a few sentences.

      -  The description is to be in English, but may contain UTF-8
         characters as may be needed in some cases.

   The update policy is "RFC Required".  Updates do not require an
   expert review by a Designated Expert.

   Following is the initial assignment for this registry:

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Record:
   URN:         urn:ietf:capability:https-notif-receiver:encoding:json
   Reference:   RFC XXXX
   Description: Identifies support for JSON-encoded notifications.

Record:
   URN:         urn:ietf:capability:https-notif-receiver:encoding:xml
   Reference:   RFC XXXX
   Description: Identifies support for XML-encoded notifications.

Record:
   URN:         urn:ietf:capability:https-notif-receiver:encoding:sub-notif
   Reference:   RFC XXXX
   Description: Identifies support for state machine described in
                RFC 8639, enabling the publisher to send, e.g., the
                "subscription-started" notification.

9.  References

9.1.  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>.

   [RFC3986]  Berners-Lee, T., Fielding, R., and L. Masinter, "Uniform
              Resource Identifier (URI): Generic Syntax", STD 66,
              RFC 3986, DOI 10.17487/RFC3986, January 2005,
              <https://www.rfc-editor.org/info/rfc3986>.

   [RFC5277]  Chisholm, S. and H. Trevino, "NETCONF Event
              Notifications", RFC 5277, DOI 10.17487/RFC5277, July 2008,
              <https://www.rfc-editor.org/info/rfc5277>.

   [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>.

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   [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>.

   [RFC7407]  Bjorklund, M. and J. Schoenwaelder, "A YANG Data Model for
              SNMP Configuration", RFC 7407, DOI 10.17487/RFC7407,
              December 2014, <https://www.rfc-editor.org/info/rfc7407>.

   [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>.

   [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>.

   [RFC8639]  Voit, E., Clemm, A., Gonzalez Prieto, A., Nilsen-Nygaard,
              E., and A. Tripathy, "Subscription to YANG Notifications",
              RFC 8639, DOI 10.17487/RFC8639, September 2019,
              <https://www.rfc-editor.org/info/rfc8639>.

   [I-D.ietf-netconf-http-client-server]
              Watsen, K., "YANG Groupings for HTTP Clients and HTTP
              Servers", Work in Progress, Internet-Draft, draft-ietf-
              netconf-http-client-server-10, 24 May 2022,
              <https://www.ietf.org/archive/id/draft-ietf-netconf-http-
              client-server-10.txt>.

9.2.  Informative references

   [RFC8126]  Cotton, M., Leiba, B., and T. Narten, "Guidelines for
              Writing an IANA Considerations Section in RFCs", BCP 26,
              RFC 8126, DOI 10.17487/RFC8126, June 2017,
              <https://www.rfc-editor.org/info/rfc8126>.

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   [RFC8141]  Saint-Andre, P. and J. Klensin, "Uniform Resource Names
              (URNs)", RFC 8141, DOI 10.17487/RFC8141, April 2017,
              <https://www.rfc-editor.org/info/rfc8141>.

Appendix A.  Configuration Examples

   This non-normative section shows two examples for how the "ietf-
   https-notif-transport" module can be used to configure a publisher to
   send notifications to a receiver.

   In both examples, the publisher, being an HTTPS client, is configured
   to send notifications to a receiver.

A.1.  Using Subscribed Notifications (RFC 8639)

   This example shows how an RFC 8639 [RFC8639] based publisher can be
   configured to send notifications to a receiver.

   =============== NOTE: '\' line wrapping per RFC 8792 ================

   <?xml version="1.0" encoding="UTF-8"?>
   <subscriptions
       xmlns="urn:ietf:params:xml:ns:yang:ietf-subscribed-notifications\
   ">
     <receiver-instances
         xmlns="urn:ietf:params:xml:ns:yang:ietf-subscribed-notif-recei\
   vers">
       <receiver-instance>
         <name>global-receiver-def</name>
         <https-receiver
             xmlns="urn:ietf:params:xml:ns:yang:ietf-https-notif-transp\
   ort"
             xmlns:x509c2n="urn:ietf:params:xml:ns:yang:ietf-x509-cert-\
   to-name">
           <tls>
             <tcp-client-parameters>
               <remote-address>receiver.example.com</remote-address>
               <remote-port>443</remote-port>
             </tcp-client-parameters>
             <tls-client-parameters>
               <server-authentication>
                 <ca-certs>
                   <local-definition>
                     <certificate>
                       <name>Server Cert Issuer #1</name>
                       <cert-data>base64encodedvalue==</cert-data>
                     </certificate>
                   </local-definition>

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                 </ca-certs>
               </server-authentication>
             </tls-client-parameters>
             <http-client-parameters>
               <client-identity>
                 <basic>
                   <user-id>my-name</user-id>
                   <cleartext-password>my-password</cleartext-password>
                 </basic>
               </client-identity>
               <path
                   xmlns="urn:ietf:params:xml:ns:yang:ietf-https-notif-\
   transport">/some/path</path>
             </http-client-parameters>
           </tls>
           <receiver-identity>
             <cert-maps>
               <cert-to-name>
                 <id>1</id>
                 <fingerprint>11:0A:05:11:00</fingerprint>
                 <map-type>x509c2n:san-any</map-type>
               </cert-to-name>
             </cert-maps>
           </receiver-identity>
         </https-receiver>
       </receiver-instance>
     </receiver-instances>
     <subscription>
       <id>6666</id>
       <transport xmlns:ph="urn:ietf:params:xml:ns:yang:ietf-https-noti\
   f-transport">ph:https</transport>
       <stream-subtree-filter>some-subtree-filter</stream-subtree-filte\
   r>
       <stream>some-stream</stream>
       <receivers>
         <receiver>
           <name>subscription-specific-receiver-def</name>
           <receiver-instance-ref xmlns="urn:ietf:params:xml:ns:yang:ie\
   tf-subscribed-notif-receivers">global-receiver-def</receiver-instanc\
   e-ref>
         </receiver>
       </receivers>
     </subscription>
   </subscriptions>
   <truststore xmlns="urn:ietf:params:xml:ns:yang:ietf-truststore">
     <certificate-bags>
       <certificate-bag>
         <name>explicitly-trusted-server-ca-certs</name>

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         <description>
           Trust anchors (i.e. CA certs) that are used to
           authenticate connections to receivers.  Receivers
           are authenticated if their certificate has a chain
           of trust to one of these CA certificates.
           certificates.
         </description>
         <certificate>
           <name>ca.example.com</name>
           <cert-data>base64encodedvalue==</cert-data>
         </certificate>
         <certificate>
           <name>Fred Flintstone</name>
           <cert-data>base64encodedvalue==</cert-data>
         </certificate>
       </certificate-bag>
     </certificate-bags>
   </truststore>

A.2.  Not Using Subscribed Notifications

   In the case that it is desired to use HTTPS-based notifications
   outside of Subscribed Notifications, an application-specific module
   would need to define the configuration for sending the notification.

   Following is an example module.  Note that the module "uses" the
   "https-receiver-grouping" grouping from the "ietf-https-notif-
   transport" module.

   module example-custom-module {
     yang-version 1.1;
     namespace "http://example.com/example-custom-module";
     prefix "custom";

     import ietf-https-notif-transport {
       prefix "hnt";
       reference
         "RFC XXXX:
           An HTTPS-based Transport for Configured Subscriptions";
     }

     organization
       "Example, Inc.";

     contact
       "Support at example.com";

     description

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       "Example of module not using Subscribed Notifications module.";

     revision "2022-07-18" {
       description
         "Initial Version.";
       reference
         "RFC XXXX: An HTTPS-based Transport for YANG Notifications.";
     }

     container example-module {
       description
         "Example of using HTTPS notif without having to
          implement Subscribed Notifications.";

       container https-receivers {
         description
           "A container of all HTTPS notif receivers.";
         list https-receiver {
          key "name";
           description
             "A list of HTTPS nofif receivers.";
          leaf name {
            type string;
            description
              "A unique name for the https notif receiver.";
          }
           uses hnt:https-receiver-grouping;
         }
       }
     }
   }

   Following is what the corresponding configuration looks like:

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   <?xml version="1.0" encoding="UTF-8"?>
   <example-module xmlns="http://example.com/example-custom-module">
     <https-receivers>
       <https-receiver>
         <name>foo</name>
         <tls>
           <tcp-client-parameters>
             <remote-address>receiver.example.com</remote-address>
             <remote-port>443</remote-port>
           </tcp-client-parameters>
           <tls-client-parameters>
             <server-authentication>
               <ca-certs>
                 <local-definition>
                   <certificate>
                     <name>Server Cert Issuer #1</name>
                     <cert-data>base64encodedvalue==</cert-data>
                   </certificate>
                 </local-definition>
               </ca-certs>
             </server-authentication>
           </tls-client-parameters>
           <http-client-parameters>
             <client-identity>
               <basic>
                 <user-id>my-name</user-id>
                 <cleartext-password>my-password</cleartext-password>
               </basic>
             </client-identity>
             <path>/some/path</path>
           </http-client-parameters>
         </tls>
       </https-receiver>
     </https-receivers>
   </example-module>

Acknowledgements

   The authors would like to thank for following for lively discussions
   on list and in the halls (ordered by first name): Eric Voit, Henning
   Rogge, Martin Bjorklund, Reshad Rahman, and Rob Wilton.

Authors' Addresses

   Mahesh Jethanandani
   Kloud Services
   Email: mjethanandani@gmail.com

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   Kent Watsen
   Watsen Networks
   Email: kent+ietf@watsen.net

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