NETCONF M. Jethanandani
Internet-Draft VMware
Intended status: Standards Track K. Watsen
Expires: September 10, 2020 Watsen Networks
March 9, 2020

An HTTPS-based Transport for Configured Subscriptions
draft-ietf-netconf-https-notif-02

Abstract

This document defines a YANG data module for configuring HTTPS based configured subscription, as defined in RFC 8639. The use of HTTPS maximizes transport-level interoperability, while allowing for encoding selection from text, e.g. XML or JSON, to binary.

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 September 10, 2020.

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

Subscription to YANG Notifications defines a YANG data module for configuring subscribed notifications. It defines a "subscriptions" container that contains a list of receivers, but it defers the configuration and management of those receivers to other documents. This document defines a YANG 1.1 data module for configuring and managing HTTPS based receivers for the notifications. 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.

This document describes how to enable the transmission of YANG modeled notifications, in the configured encoding (i.e., XML, JSON) over HTTPS. Notifications are delivered in the form of a HTTPS POST. The use of HTTPS maximizes transport-level interoperability, while the encoding selection pivots between implementation simplicity (XML, JSON) and throughput (text versus binary).

1.1. Applicability Statement

While the YANG module has been defined as an augmentation of Subscription to YANG Notifications, the notification method defined in this document MAY be used outside of Subscription to YANG Notifications by using the grouping defined in the model.

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.

2020-03-09 with the actual date of the publication of this document.

1.3. Abbreviations

Acronym Expansion
HTTP Hyper Text Transport Protocol
HTTPS Hyper Text Transport Protocol Secure
TCP Transmission Control Protocol
TLS Transport Layer Security

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. Subscribed Notifications

The following terms are defined in Subscription to YANG Notifications.

2. Learning Receiver Capabilities

2.1. Introduction

To learn the capabilities of the receiver, the publisher can issue a HTTPS GET request with Accept-Type set to application/ietf-https-notif-cap+xml or application/ietf-https-notif-cap+json, with latter as the mandatory to implement, and the default in case the type is not specified. If the receiver supports capabilities such as binary encoding of data, it can return that as a capability in a response. Please note that, when used in conjunction with Subscription to YANG Notifications, dynamic discovery of the receiver’s supported encoding is considered only when the "/subscriptions/subscription/encoding” leaf is not configured, per the “encoding” leaf’s description statement.

2.2. Example

The publisher can send the following request to learn the receiver capabilities. The Accept-Type states its preferred order for Content-Type that it wants to receive starting with XML, and if not supported, to use JSON encoding. Currently, there is only one capability of binary encoding defined.

GET / HTTP/1.1
Host: example.com
Accept-Type: application/ietf-https-notif-cap+xml, application/ietf-https-notif-cap+json

In case the receiver supports the first Accept-Type, its response should 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/ietf-https-notif-cap+xml
Content-Length: nnn

<receiver-capabilities>
  <receiver-capability>
    <urn:ietf:params:https-config:capability:binary-encoding:1.0>
  </receiver-capability>
</receiver-capabilities>

3. YANG module

3.1. Overview

The 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 Subscription to YANG Notifications receiver container to create a reference to a receiver defined by the YANG module. As mentioned earlier, it uses POST method to deliver the notification. The attribute 'path' defines the absolute path for the resource on the receiver, as defined by 'path-absolute' in URI Generic Syntax. The user-id used by Network Configuration Access Control Model, is that of the receiver and is derived from the certificate presented by the receiver.

An abridged tree diagram representing the module is shown below.


module: ietf-https-notif
  augment /sn:subscriptions:
    +--rw https-receivers
       +--rw https-receiver* [name]
          +--rw name                 string
          +--rw tcp-params
          |  +--rw remote-address    inet:host
          |  +--rw remote-port?      inet:port-number
          |  +--rw local-address?    inet:ip-address
          |  +--rw local-port?       inet:port-number
          |  +--rw keepalives!
          |        ...
          +--rw tls-params
          |  +--rw client-identity
          |  |     ...
          |  +--rw server-authentication
          |  |     ...
          |  +--rw hello-params {tls-client-hello-params-config}?
          |  |     ...
          |  +--rw keepalives! {tls-client-keepalives}?
          |        ...
          +--rw http-params
          |  +--rw protocol-version?   enumeration
          |  +--rw client-identity
          |  |     ...
          |  +--rw proxy-server! {proxy-connect}?
          |  |     ...
          |  +--rw path?               inet:uri
          +--rw receiver-identity
             +--rw cert-maps
                   ...
  augment /sn:subscriptions/sn:subscription/sn:receivers/sn:receiver:
    +--rw receiver-ref?   leafref

3.2. YANG module

The YANG module imports Common YANG Data Types, A YANG Data Model for SNMP Configuration, and Subscription to YANG Notifications.

The YANG module is shown below.

<CODE BEGINS> file "ietf-https-notif@2020-03-09.yang"
module ietf-https-notif {
  yang-version 1.1;
  namespace "urn:ietf:params:xml:ns:yang:ietf-https-notif";
  prefix "hn";

  import ietf-inet-types {
    prefix inet;
    reference
      "RFC 6991: Common YANG Data Types.";
  }

  import ietf-subscribed-notifications {
    prefix sn;
    reference
      "I-D.ietf-netconf-subscribed-notifications";
  }

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

  import ietf-tcp-client {
    prefix tcpc;
  }

  import ietf-tls-client {
    prefix tlsc;
  }
  
  import ietf-http-client {
    prefix httpc;
  }
  
  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
    "YANG module for configuring HTTPS base configuration.

     Copyright (c) 2018 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 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.

     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 "2020-03-09" {
    description
      "Initial Version.";
    reference
      "RFC XXXX, YANG Data Module for HTTPS Notifications.";
  }

  identity https {
    base sn:transport;
    description
      "HTTPS transport for notifications.";
  }

  grouping https-receivers {
    description
      "Grouping for HTTPS based receivers such that it can be
       implemented outside the constructs of a Subscription to YANG
       Notification [RFC8639] module.";
    container https-receivers {
      description
        "HTTPS based notifications.";

      list https-receiver {
        key "name";

        leaf name {
          type string;
          description
            "A name that uniquely identifies this receiver.";
        }

        container tcp-params {
          uses tcpc:tcp-client-grouping;
          description
            "TCP client parameters.";
        }

        container tls-params {
          uses tlsc:tls-client-grouping;
          description
            "TLS client parameters.";
        }

        container http-params {
          description
            "HTTP client parameters.";

          uses httpc:http-client-grouping;

          leaf path {
            type inet:uri;
            description
              "The absolute path for the resource on the remote
               HTTPS server. The absolute path as specified in
               RFC 3986 as 'path-absolute'.";
            reference
              "RFC 3986: URI Generic Syntax.";
          }
        }

        container receiver-identity {
          description
            "Specifies mechanism for identifying the receiver. The
             publisher MUST NOT include any content in a notification
             that the user is not 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.";
          }
        }
        description
          "All receivers interested in this notification.";
      }
    }
  }
  
  augment "/sn:subscriptions" {
    description
      "Augment the subscirbed notification module to add in the
       receivers container.";
    uses https-receivers;
  }

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

4. 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 or RESTCONF. The lowest NETCONF layer is the secure transport layer, and the mandatory-to-implement secure transport is Secure Shell (SSH). The lowest RESTCONF layer is HTTPS, and the mandatory-to-implement secure transport is TLS. The NETCONF Access Control Model (NACM) 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.

There are a number of data nodes defined in this YANG module 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:

Some of the readable data nodes in this YANG module 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. These are the subtrees and data nodes and their sensitivity/vulnerability:

Some of the RPC operations in this YANG module may be considered sensitive or vulnerable in some network environments. It is thus important to control access to these operations. These are the operations and their sensitivity/vulnerability:

5. IANA Considerations

This document registers one URI, one YANG module and two Media Types.

5.1. URI Registration

URI: urn:ietf:params:xml:ns:yang:ietf-http-notif

in the IETF XML registry. Following the format in RFC 3688, the following registration is requested to be made:

Registrant Contact: The IESG. XML: N/A, the requested URI is an XML namespace.

5.2. YANG Module Name Registration

This document registers one YANG module in the YANG Module Names registry YANG.

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

5.3. Media Types

5.3.1. Media Type "application/ietf-https-notif-cap+xml

Type name: application

Subtype name: ietf-https-notif-cap+xml

Required parameters: None

Optional parameters: None

Encoding considerations: 
    8-bit Each conceptual YANG data node is encoded according to the XML 
    Encoding Rules and Canonical Format for the specific YANG data node 
    type defined in YANG 1.1 [RFC7950].

Security considerations: 
    Security considerations related to the generation and consumption of 
    RESTCONF messages are discussed in Section NN of RFC XXXX. 
    
    Additional security considerations are specific to the semantics of 
    particular YANG data models. Each YANG module is expected to specify 
    security considerations for the YANG data defined in that module.

Interoperability considerations: N/A

Published specification: RFC XXXX

Applications that use this media type: 
    Instance document data parsers used within a protocol or automation 
    tool that utilize YANG-defined data structures.

Fragment identifier considerations: 
    Fragment identifiers for this type are not defined. All YANG data 
    nodes are accessible as resources using the path in the request URI.

Additional information:

    Deprecated alias names for this type: N/A
    Magic number(s): N/A
    File extension(s): None
    Macintosh file type code(s): "TEXT"

Person & email address to contact for further information: 
    See Author's Address section of RFC XXXX.

Intended usage: COMMON

Restrictions on usage: N/A

Author: See Author's Address section of RFC XXXX

Change controller: 
    Internet Engineering Task Force (mailto:iesg@ietf.org)

Provisional registration? (standards tree only): no

5.3.2. Media Type "application/ietf-https-notif-cap+json

Type name: application

Subtype name: ietf-https-notif-cap+json

Required parameters: None

Optional parameters: None

Encoding considerations: 
    8-bit Each conceptual YANG data node is encoded according to the XML 
    Encoding Rules and Canonical Format for the specific YANG data node 
    type defined in JSON Encoding of Data Modeled with YANG [RFC7951].

Security considerations: 
    Security considerations related to the generation and consumption of 
    RESTCONF messages are discussed in Section NN of RFC XXXX. 
    
    Additional security considerations are specific to the semantics of 
    particular YANG data models. Each YANG module is expected to specify 
    security considerations for the YANG data defined in that module.

Interoperability considerations: N/A

Published specification: RFC XXXX

Applications that use this media type: 
    Instance document data parsers used within a protocol or automation 
    tool that utilize YANG-defined data structures.

Fragment identifier considerations: 
    Fragment identifiers for this type are not defined. All YANG data 
    nodes are accessible as resources using the path in the request URI.

Additional information:

    Deprecated alias names for this type: N/A
    Magic number(s): N/A
    File extension(s): None
    Macintosh file type code(s): "TEXT"

Person & email address to contact for further information: 
    See Author's Address section of RFC XXXX.

Intended usage: COMMON

Restrictions on usage: N/A

Author: See Author's Address section of RFC XXXX

Change controller: 
    Internet Engineering Task Force (mailto:iesg@ietf.org)

Provisional registration? (standards tree only): no

6. Examples

This section tries to show some examples in how the model can be used.

6.1. HTTPS Configured Subscription

This example shows how a HTTPS client can be configured to send notifications to a receiver at address 192.0.2.1, port 443 with server certificates, and the corresponding trust store that is used to authenticate a connection.

[note: '\' line wrapping for formatting only]

<?xml version="1.0" encoding="UTF-8"?>
<config xmlns="urn:ietf:params:xml:ns:netconf:base:1.0">
  <subscriptions
      xmlns="urn:ietf:params:xml:ns:yang:ietf-subscribed-notificatio\
ns">
    <https-receivers
	xmlns="urn:ietf:params:xml:ns:yang:ietf-https-notif"
	xmlns:x509c2n="urn:ietf:params:xml:ns:yang:ietf-x509-cert-to-name">\

      <https-receiver>
	<name>foo</name>
	<tcp-params>
	  <remote-address>my-receiver.my-domain.com</remote-address>
	  <remote-port>443</remote-port>
	</tcp-params>
	<tls-params>
	  <server-authentication>
	    <ca-certs>explicitly-trusted-server-ca-certs</ca-certs>
	    <server-certs>explicitly-trusted-server-certs</server-certs>
	  </server-authentication>
	</tls-params>
	<http-params>
          <client-identity>
	    <basic>
	      <user-id>my-name</user-id>
	      <password>my-password</password>
	    </basic>
          </client-identity>
          <path>/some/path</path>
	</http-params>
	<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>
    </https-receivers>
    <subscription>
      <id>6666</id>
      <stream-subtree-filter>foo</stream-subtree-filter>
      <stream>some-stream</stream>
      <receivers>
	<receiver>
	  <name>my-receiver</name>
	  <receiver-ref
	      xmlns="urn:ietf:params:xml:ns:yang:ietf-https-notif">foo</rec\
eiver-ref>
	</receiver>
      </receivers>
    </subscription>
  </subscriptions>
  
  <truststore xmlns="urn:ietf:params:xml:ns:yang:ietf-truststore">
    <certificates>
      <name>explicitly-trusted-server-certs</name>
      <description>
        Specific server authentication certificates for explicitly
        trusted servers.  These are needed for server certificates
        that are not signed by a pinned CA.
      </description>
      <certificate>
        <name>Fred Flintstone</name>
        <cert>base64encodedvalue==</cert>
      </certificate>
    </certificates>
    <certificates>
      <name>explicitly-trusted-server-ca-certs</name>
      <description>
        Trust anchors (i.e. CA certs) that are used to authenticate
        server connections.  Servers are authenticated if their
        certificate has a chain of trust to one of these CA
        certificates.
      </description>
      <certificate>
        <name>ca.example.com</name>
        <cert>base64encodedvalue==</cert>
      </certificate>
    </certificates>
  </truststore>
</config>

6.2. Bundled Message

In the case of "bundled-message" as defined in Notification Message Headers and Bundles, something that this module supports, the flow of messages would look something like this.

       -------------                               --------------
       | Publisher |                               | Receiver   |
       -------------                               --------------
       Establish TCP             ------>
       Establish TLS             ------>
       Send HTTPS POST message
       with YANG defined         ------>
       notification #1
       Send HTTPS POST message
       with YANG defined         ------>
       notification #2
                                                   Send 204 (No Content)
                                 <------           for notification #1

                                                   Send 204 (No Content)
                                 <------           for notification #2
       Send HTTPS POST message
       with YANG defined         ------->
       notification #3
                                                   Send 204 (No Content)
                                 <------           for notification #3

The content of the exchange would look something like this.

Request:
    POST /some/path HTTP/1.1
    Host: my-receiver.my-domain.com
    Content-Type: application/yang-data+xml
    <notification
      xmlns="urn:ietf:params:xml:ns:netconf:notification:1.0">
      <eventTime>2019-03-22T12:35:00Z</eventTime>
      <foo xmlns="https://example.com/my-foobar-module">
        ...
      </foo>
    </notification>
    <notification
      xmlns="urn:ietf:params:xml:ns:netconf:notification:1.0">
      <eventTime>2019-03-22T12:35:00Z</eventTime>
      <bar xmlns="https://example.com/my-foobar-module">
        ...
      </bar>
    </notification>
    <notification
      xmlns="urn:ietf:params:xml:ns:netconf:notification:1.0">
      <eventTime>2019-03-22T12:35:01Z</eventTime>
      <baz xmlns="https://example.com/my-foobar-module">
        ...
      </baz>
    </notification>
Response:
      HTTP/1.1 204 No Content
      Date: Fri, 03 Mar 2019 12:35:00 GMT
      Server: my-receiver.my-domain.com
      HTTP/1.1 204 No Content
      Date: Fri, 03 Mar 2019 12:35:00 GMT
      Server: my-receiver.my-domain.com
      HTTP/1.1 204 No Content
      Date: Fri, 03 Mar 2019 12:35:01 GMT
      Server: my-receiver.my-domain.com

7. Contributors

8. Acknowledgements

9. References

9.1. Normative references

[I-D.ietf-netconf-notification-messages] Voit, E., Jenkins, T., Birkholz, H., Bierman, A. and A. Clemm, "Notification Message Headers and Bundles", Internet-Draft draft-ietf-netconf-notification-messages-08, November 2019.
[RFC2119] Bradner, S., "Key words for use in RFCs to Indicate Requirement Levels", BCP 14, RFC 2119, DOI 10.17487/RFC2119, March 1997.
[RFC3688] Mealling, M., "The IETF XML Registry", BCP 81, RFC 3688, DOI 10.17487/RFC3688, January 2004.
[RFC6020] Bjorklund, M., "YANG - A Data Modeling Language for the Network Configuration Protocol (NETCONF)", RFC 6020, DOI 10.17487/RFC6020, October 2010.
[RFC6241] Enns, R., Bjorklund, M., Schoenwaelder, J. and A. Bierman, "Network Configuration Protocol (NETCONF)", RFC 6241, DOI 10.17487/RFC6241, June 2011.
[RFC6242] Wasserman, M., "Using the NETCONF Protocol over Secure Shell (SSH)", RFC 6242, DOI 10.17487/RFC6242, June 2011.
[RFC6991] Schoenwaelder, J., "Common YANG Data Types", RFC 6991, DOI 10.17487/RFC6991, July 2013.
[RFC7407] Bjorklund, M. and J. Schoenwaelder, "A YANG Data Model for SNMP Configuration", RFC 7407, DOI 10.17487/RFC7407, December 2014.
[RFC7950] Bjorklund, M., "The YANG 1.1 Data Modeling Language", RFC 7950, DOI 10.17487/RFC7950, August 2016.
[RFC7951] Lhotka, L., "JSON Encoding of Data Modeled with YANG", RFC 7951, DOI 10.17487/RFC7951, August 2016.
[RFC8040] Bierman, A., Bjorklund, M. and K. Watsen, "RESTCONF Protocol", RFC 8040, DOI 10.17487/RFC8040, January 2017.
[RFC8174] Leiba, B., "Ambiguity of Uppercase vs Lowercase in RFC 2119 Key Words", BCP 14, RFC 8174, DOI 10.17487/RFC8174, May 2017.
[RFC8341] Bierman, A. and M. Bjorklund, "Network Configuration Access Control Model", STD 91, RFC 8341, DOI 10.17487/RFC8341, March 2018.
[RFC8446] Rescorla, E., "The Transport Layer Security (TLS) Protocol Version 1.3", RFC 8446, DOI 10.17487/RFC8446, August 2018.
[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.

9.2. Informative references

[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.

Authors' Addresses

Mahesh Jethanandani VMware EMail: mjethanandani@gmail.com
Kent Watsen Watsen Networks USA EMail: kent+ietf@watsen.net