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draft-ietf-netconf-netconf-client-server
NETCONF Working Group K. Watsen
Internet-Draft Juniper Networks
Intended status: Standards Track J. Schoenwaelder
Expires: March 26, 2015 Jacobs University Bremen
September 22, 2014
NETCONF Server Configuration Model
draft-ietf-netconf-server-model-03
Abstract
This draft defines a NETCONF server configuration data model. This
data model enables configuration of the NETCONF service itself,
including which transports it supports, what ports they listen on,
whether they support device-initiated connections, and associated
parameters.
Status of This Memo
This Internet-Draft is submitted in full conformance with the
provisions of BCP 78 and BCP 79.
Internet-Drafts are working documents of the Internet Engineering
Task Force (IETF). Note that other groups may also distribute
working documents as Internet-Drafts. The list of current Internet-
Drafts is at http://datatracker.ietf.org/drafts/current/.
Internet-Drafts are draft documents valid for a maximum of six months
and may be updated, replaced, or obsoleted by other documents at any
time. It is inappropriate to use Internet-Drafts as reference
material or to cite them other than as "work in progress."
This Internet-Draft will expire on March 26, 2015.
Copyright Notice
Copyright (c) 2014 IETF Trust and the persons identified as the
document authors. All rights reserved.
This document is subject to BCP 78 and the IETF Trust's Legal
Provisions Relating to IETF Documents
(http://trustee.ietf.org/license-info) in effect on the date of
publication of this document. Please review these documents
carefully, as they describe your rights and restrictions with respect
to this document. Code Components extracted from this document must
include Simplified BSD License text as described in Section 4.e of
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the Trust Legal Provisions and are provided without warranty as
described in the Simplified BSD License.
Table of Contents
1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . 2
1.1. Terminology . . . . . . . . . . . . . . . . . . . . . . . 3
1.2. Tree Diagrams . . . . . . . . . . . . . . . . . . . . . . 3
2. Objectives . . . . . . . . . . . . . . . . . . . . . . . . . 3
2.1. Support all NETCONF Transports . . . . . . . . . . . . . 3
2.2. Align Transport-Specific Configurations . . . . . . . . . 3
2.3. Support both Listening for Connections and Call Home . . 4
2.4. For Call Home Connections . . . . . . . . . . . . . . . . 4
2.4.1. Support More than One Application . . . . . . . . . . 4
2.4.2. Support Applications Having More than One Server . . 4
2.4.3. Support a Reconnection Strategy . . . . . . . . . . . 4
2.4.4. Support both Persistent and Periodic Connections . . 4
2.4.5. Reconnection Strategy for Periodic Connections . . . 5
2.4.6. Keep-Alives for Persistent Connections . . . . . . . 5
2.4.7. Customizations for Periodic Connections . . . . . . . 5
3. Data Model . . . . . . . . . . . . . . . . . . . . . . . . . 6
3.1. Overview . . . . . . . . . . . . . . . . . . . . . . . . 6
3.2. YANG Module . . . . . . . . . . . . . . . . . . . . . . . 8
4. Keep-Alives for SSH and TLS . . . . . . . . . . . . . . . . . 21
4.1. SSH . . . . . . . . . . . . . . . . . . . . . . . . . . . 21
4.2. TLS . . . . . . . . . . . . . . . . . . . . . . . . . . . 22
5. Security Considerations . . . . . . . . . . . . . . . . . . . 22
6. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 23
7. Other Considerations . . . . . . . . . . . . . . . . . . . . 23
8. Acknowledgements . . . . . . . . . . . . . . . . . . . . . . 23
9. References . . . . . . . . . . . . . . . . . . . . . . . . . 24
9.1. Normative References . . . . . . . . . . . . . . . . . . 24
9.2. Informative References . . . . . . . . . . . . . . . . . 25
Appendix A. Examples . . . . . . . . . . . . . . . . . . . . . . 26
A.1. SSH Transport Configuration . . . . . . . . . . . . . . . 26
A.2. TLS Transport Configuration . . . . . . . . . . . . . . . 26
Appendix B. Change Log . . . . . . . . . . . . . . . . . . . . . 27
B.1. 00 to 01 . . . . . . . . . . . . . . . . . . . . . . . . 28
B.2. 01 to 02 . . . . . . . . . . . . . . . . . . . . . . . . 28
B.3. 02 to 03 . . . . . . . . . . . . . . . . . . . . . . . . 28
Appendix C. Open Issues . . . . . . . . . . . . . . . . . . . . 28
1. Introduction
This draft defines a NETCONF [RFC6241] server configuration data
model. This data model enables configuration of the NETCONF service
itself, including which transports are supported, what ports does the
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server listen on, whether call-home is supported, and associated
parameters.
1.1. Terminology
The keywords "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT",
"SHOULD", "SHOULD NOT", "RECOMMENDED", "MAY", and "OPTIONAL" in this
document are to be interpreted as described in RFC 2119 [RFC2119].
1.2. Tree Diagrams
A simplified graphical representation of data models is used in this
document. The meaning of the symbols in these diagrams is as
follows:
o Brackets "[" and "]" enclose list keys.
o Abbreviations before data node names: "rw" means configuration
(read-write) and "ro" state data (read-only).
o Symbols after data node names: "?" means an optional node, "!"
means a presence container, and "*" denotes a list and leaf-list.
o Parentheses enclose choice and case nodes, and case nodes are also
marked with a colon (":").
2. Objectives
The primary purpose of the YANG module defined herein is to enable
the configuration of the NETCONF service on the device. This scope
includes the following objectives:
2.1. Support all NETCONF Transports
The YANG module should support all current NETCONF transports, namely
NETCONF over SSH [RFC6242] and NETCONF over TLS [rfc5539bis], and be
extensible to support future transports as necessary.
Since implementations may not support all transports, the module
should use YANG "feature" statements so that implementations can
accurately advertise which transports are supported.
2.2. Align Transport-Specific Configurations
While each transport is unique in its protocol and may have some
distinct configurations, there remains a significant overlap between
them. Thus the YANG module should use "grouping" statements so that
the common aspects can be configured similarly.
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2.3. Support both Listening for Connections and Call Home
NETCONF has always supported the server opening a port to listen for
client connections. More recently the NETCONF working group defined
support for call-home ([draft-ietf-netconf-call-home]). The module
should configure both listening for connections and call-home.
Since implementations may not support both listening for connections
and call home, YANG "feature" statements should be used so that
implementation can accurately advertise the connection types it
supports.
2.4. For Call Home Connections
The following objectives only pertain to call home connections.
2.4.1. Support More than One Application
A device may be managed by more than one northbound application. For
instance, a deployment may have one application for provisioning and
another for fault monitoring. Therefore, when it is desired for a
device to initiate call home connections, it should be able to do so
for more than one application.
2.4.2. Support Applications Having More than One Server
An application managing a device may implement a high-availability
strategy employing a multiplicity of active and/or passive servers.
Therefore, when it is desired for a device to initiate call home
connections, it should be able to connect to any of the applications
servers.
2.4.3. Support a Reconnection Strategy
Assuming an application has more than one server, then it becomes
necessary to configure how a device should reconnect to the
application should it lose its connection to the application's
servers. Of primary interest is if the device should start with
first server defined in a user-ordered list of servers or with the
last server it was connected to. Secondary settings might specify
the frequency of attempts and number of attempts per server.
Therefore, a reconnection strategy should be configurable.
2.4.4. Support both Persistent and Periodic Connections
Applications may vary greatly on how frequently they need to interact
with a device, how responsive interactions with devices need to be,
and how many simultaneous connections they can support. Some
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applications may need a persistent connection to devices to optimize
real-time interactions, while others are satisfied with periodic
interactions and reduced resources required. Therefore, when it is
necessary for devices to initiate connections, the type of connection
desired should be configured.
2.4.5. Reconnection Strategy for Periodic Connections
The reconnection strategy should apply to both persistent and
periodic connections. How it applies to periodic connections becomes
clear when considering that a periodic "connection" is a logical
connection to a single server. That is, the periods of
unconnectedness are intentional as opposed to due to external
reasons. A periodic "connection" should always reconnect to the same
server until it is no longer able to, at which time the reconnection
strategy guides how to connect to another server.
2.4.6. Keep-Alives for Persistent Connections
If a persistent connection is desired, it is the responsibility of
the connection-initiator to actively test the aliveness of the
connection. The connection initiator must immediately work to
reestablish a persistent connection as soon as the connection is
lost. How often the connection should be tested is driven by
applications requirements, and therefore keep-alive settings should
be configurable on a per-application basis.
2.4.7. Customizations for Periodic Connections
If a periodic connection is desired, it is necessary for the device
to know how often it should connect. This delay essentially
determines how long the application might have to wait to send data
to the device. This setting does not constrain how often the device
must wait to send data to the application, as the device should
immediately connect to the application whenever it has data to send
to it.
A common communication pattern is that one data transmission is many
times closely followed by another. For instance, if the device needs
to send a notification message, there's a high probability that it
will send another shortly thereafter. Likewise, the application may
have a sequence of pending messages to send. Thus, it should be
possible for a device to hold a connection open until some amount of
time of no data being transmitted as transpired.
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3. Data Model
3.1. Overview
The following subtree illustrates how this YANG module enables
configuration for listening for remote connections, as described in
[RFC6242] and [rfc5539bis]. Feature statements are used to limit
both if listening is supported at all as well as for which
transports. If listening for connections is supported, then the
model enables configuring a list of listening endpoints, each
configured with a user-specified name (the key field), the transport
to use (i.e. SSH, TLS), and the IP address and port to listen on.
The port field is optional, defaulting to the transport-specific port
when not configured.
module: ietf-netconf-server
+--rw netconf-server
+--rw listen* [name]
+--rw name string
+--rw (transport)
+--:(ssh) {ssh-listen}?
| +--rw ssh
| +--rw address inet:host
| +--rw port? inet:port-number
+--:(tls) {tls-listen}?
+--rw tls
+--rw address inet:host
+--rw port? inet:port-number
The following subtree illustrates how this YANG module enables
configuration for call home, as described in
[draft-ietf-netconf-call-home]. Feature statements are used to limit
both if call-home is supported at all as well as for which
transports, if it is. If call-home is supported, then the model
supports configuring a list of applications to connect to. Each
application is configured with a user-specified name (the key field),
the transport to be used (i.e. SSH, TLS), and a list of remote
endpoints, each having a name, an IP address, and an optional port.
Additionally, the configuration for each remote application indicates
the connection-type (persistent vs. periodic) and associated
parameters, as well as the reconnection strategy to use.
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module: ietf-netconf-server
+--rw netconf-server
+--rw call-home* [name]
+--rw name string
+--rw (transport)
| +--:(ssh) {ssh-call-home}?
| | +--rw ssh
| | +--rw endpoints
| | | +--rw endpoint* [name]
| | | +--rw name string
| | | +--rw address inet:host
| | | +--rw port? inet:port-number
| | +--rw host-key* [name]
| | +--rw name string
| +--:(tls) {tls-call-home}?
| +--rw tls
| +--rw endpoints
| +--rw endpoint* [name]
| +--rw name string
| +--rw address inet:host
| +--rw port? inet:port-number
+--rw connection-type
| +--rw (connection-type)?
| +--:(persistent-connection)
| | +--rw persistent
| | +--rw keep-alives
| | +--rw interval-secs? uint8
| | +--rw count-max? uint8
| +--:(periodic-connection)
| +--rw periodic
| +--rw timeout-mins? uint8
| +--rw linger-secs? uint8
+--rw reconnect-strategy
+--rw start-with? enumeration
+--rw interval-secs? uint8
+--rw count-max? uint8
The following subtree illustrates how this YANG module enables
authentication of TLS client certificates and mapping TLS clients to
NETCONF user names. More specifically, the "trusted-ca-certs" and
"trusted-client-certs" containers are used to authenticate TLS client
certificates, while "cert-maps" and "psk-maps" are used to map TLS
clients to NETCONF user names.
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module: ietf-netconf-server
+--rw netconf-server
+--rw tls-client-auth
+--rw trusted-ca-certs
| +--rw trusted-ca-cert* binary
+--rw trusted-client-certs
| +--rw trusted-client-cert* binary
+--rw cert-maps {tls-map-certificates}?
| +--rw cert-to-name* [id]
| +--rw id uint32
| +--rw fingerprint x509c2n:tls-fingerprint
| +--rw map-type identityref
| +--rw name string
+--rw psk-maps {tls-map-pre-shared-keys}?
+--rw psk-map* [psk-identity]
+--rw psk-identity string
+--rw user-name nacm:user-name-type
+--rw not-valid-before? yang:date-and-time
+--rw not-valid-after? yang:date-and-time
+--rw key yang:hex-string
3.2. YANG Module
This YANG module imports YANG types from [RFC6991], [RFC6536], and
[draft-ietf-netmod-snmp-cfg].
RFC Ed.: update the date below with the date of RFC publication
and remove this note.
<CODE BEGINS> file "ietf-netconf-server@YYYY-MM-DD.yang"
module ietf-netconf-server {
namespace "urn:ietf:params:xml:ns:yang:ietf-netconf-server";
prefix "ncserver";
import ietf-inet-types {
prefix inet; // RFC 6991
}
import ietf-yang-types {
prefix yang; // RFC 6991
}
import ietf-netconf-acm {
prefix nacm; // RFC 6536
}
import ietf-x509-cert-to-name {
prefix x509c2n; // draft-ietf-netmod-snmp-cfg
}
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organization
"IETF NETCONF (Network Configuration) Working Group";
contact
"WG Web: <http://tools.ietf.org/wg/netconf/>
WG List: <mailto:netconf@ietf.org>
WG Chair: Mehmet Ersue
<mailto:mehmet.ersue@nsn.com>
WG Chair: Bert Wijnen
<mailto:bertietf@bwijnen.net>
Editor: Kent Watsen
<mailto:kwatsen@juniper.net>";
description
"This module contains a collection of YANG definitions for
configuring NETCONF servers.
Copyright (c) 2014 IETF Trust and the persons identified as
authors of the code. All rights reserved.
Redistribution and use in source and binary forms, with or
without modification, is permitted pursuant to, and subject
to the license terms contained in, the Simplified BSD
License set forth in Section 4.c of the IETF Trust's
Legal Provisions Relating to IETF Documents
(http://trustee.ietf.org/license-info).
This version of this YANG module is part of RFC XXXX; see
the RFC itself for full legal notices.";
// RFC Ed.: replace XXXX with actual RFC number and
// remove this note
// RFC Ed.: please update the date to the date of publication
revision "YYYY-MM-DD" {
description
"Initial version";
reference
"RFC XXXX: NETCONF Server Configuration Model";
}
// Features
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feature ssh-listen {
description
"The ssh-listen feature indicates that the NETCONF server can
open a port to listen for incoming client connections.";
}
feature ssh-call-home {
description
"The ssh-call-home feature indicates that the NETCONF server can
connect to a client.";
reference
"RFC XXXX: Reverse Secure Shell (Reverse SSH)";
}
feature tls-listen {
description
"The tls-listen feature indicates that the NETCONF server can
open a port to listen for incoming client connections.";
}
feature tls-call-home {
description
"The tls-call-home feature indicates that the NETCONF server can
connect to a client.";
}
feature tls-map-certificates {
description
"The tls-map-certificates feature indicates that the
NETCONF server implements mapping X.509 certificates to NETCONF
usernames.";
}
feature tls-map-pre-shared-keys {
description
"The tls-map-pre-shared-keys feature indicates that the
NETCONF server implements mapping TLS pre-shared keys
to NETCONF usernames.";
}
// Module's top-level container
container netconf-server {
description
"Top-level container for NETCONF server configuration.";
list listen {
key name;
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description
"List of endpoints to listen for connections on.";
//if-feature "(ssh-listen or tls-listen)";
uses listen-config;
}
list call-home {
key name;
description
"List of applications to call-home to.";
//if-feature "(ssh-call-home or tls-call-home)";
uses call-home-config;
}
container tls-client-auth {
//if-feature "(tls-listen or tls-call-home)";
description
"Container for TLS client authentication configuration.";
uses trusted-ca-certs-grouping;
uses trusted-client-certs-grouping;
uses cert-maps-grouping;
uses psk-maps-grouping;
}
}
// Groupings
grouping listen-config {
description
"Grouping for listen configuration.";
leaf name {
type string;
description
"An arbitrary name for the listen endpoint.";
}
choice transport {
mandatory true;
description
"Selects between SSH and TLS transports.";
case ssh {
if-feature ssh-listen;
container ssh {
description
"SSH-specific listening configuration for inbound
connections.";
uses listen-per-transport-config {
refine port {
default 830;
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}
}
}
}
case tls {
if-feature tls-listen;
container tls {
description
"TLS-specific listening configuration for inbound
connections.";
uses listen-per-transport-config {
refine port {
default 6513;
}
}
}
}
}
}
grouping listen-per-transport-config {
description
"Provides the configuration of the NETCONF server to
open one or more ports to listen for incoming client
connections.";
leaf address {
type inet:host;
mandatory true;
description
"The local IP address/name of the interface to listen on.";
}
leaf port {
type inet:port-number;
description
"The local port number on this interface the
NETCONF server listens on.";
}
}
grouping call-home-config {
description
"Grouping for call-home configuration.";
leaf name {
type string;
description
"An arbitrary name for the remote application.";
}
uses call-home-transport-config;
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uses call-home-connection-type-config;
uses call-home-reconnection-strategy-config;
}
grouping call-home-transport-config {
description
"Grouping for call-home specific transport selection.";
choice transport {
mandatory true;
description
"Selects between SSH and TLS transports.";
case ssh {
if-feature ssh-call-home;
container ssh {
description
"Specifies SSH-specific call-home transport
configuration.";
uses call-home-per-transport-config {
refine endpoints/endpoint/port {
default 9999; // pending IANA assignment
}
}
list host-key {
key name;
min-elements 1;
ordered-by user;
description
"User-ordered list of host-keys the SSH server
should advertise.";
leaf name {
type string;
mandatory true;
description
"The name of a host key the device should
advertise during the SSH key exchange.";
}
}
}
}
case tls {
if-feature tls-call-home;
container tls {
description
"Specifies TLS-specific call-home transport
configuration.";
uses call-home-per-transport-config {
refine endpoints/endpoint/port {
default 9999; // pending IANA assignment
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}
}
}
}
}
}
grouping call-home-per-transport-config {
description
"Grouping for transport-specific configuration for
call-home connections.";
container endpoints {
description
"Container for the list of endpoints.";
list endpoint {
key name;
min-elements 1;
ordered-by user;
description
"User-ordered list of endpoints for this application.
Defining more than one enables high-availability.";
leaf name {
type string;
description
"An arbitrary name for the endpoint to connect to.";
}
leaf address {
type inet:host;
mandatory true;
description
"The hostname or IP address of the endpoint.
If a hostname is provided and DNS resolves to
more than one IP address, the device SHOULD
try all of the ones it can based on how its
networking stack is configured (e.g. v4, v6,
dual-stack).";
}
leaf port {
type inet:port-number;
description
"The IP port for this endpoint. The device will use
the IANA-assigned well-known port if not specified.";
}
}
}
}
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grouping call-home-connection-type-config {
description
"Grouping to define connection-type for call-home
based connections.";
container connection-type {
description
"Indicates the network manager's preference for how the
device's connection is maintained.";
choice connection-type {
default persistent-connection;
description
"Selects between persistent and periodic connections.";
case persistent-connection {
container persistent {
description
"Maintain a persistent connection to the
network manager. If the connection goes down,
immediately start trying to reconnect to it,
using the reconnection strategy.
This connection type minimizes any
manager-to-device data-transfer delay,
albeit at the expense of holding resources
longer.";
container keep-alives {
description
"Configures keep-alive policy, to proactively
detect when a persistent connection to an
endpoint has dropped.";
leaf interval-secs {
type uint8;
units seconds;
default 15;
description
"Sets a timeout interval in seconds after which
if no data has been received from the manager's
endpoint, a message will be sent to request a
response from the endpoint. A value of '0'
indicates that no keep-alive messages should
be sent.";
}
leaf count-max {
type uint8;
default 3;
description
"Sets the number of keep-alive messages that may
be sent without receiving any data from the
manager's endpoint before assuming the endpoint
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is no longer alive. If this threshold is
reached, the transport-level connection will be
disconnected (thus triggering the reconnection
strategy). The interval timer is reset after
each transmission, thus an unresponsive
endpoint will be disconnected after about
count-max * interval-secs seconds.";
}
}
}
}
case periodic-connection {
container periodic {
description
"Periodically connect to network manager, using the
reconnection strategy, so it can flush any pending
data it may be holding. This connection type
minimizes resources held open, albeit at the
expense of longer manager-to-device data-transfer
delay. Note that for device-to-manager data, the
data should be sent immediately, connecting to
network manager first if not already.";
leaf timeout-mins {
type uint8;
units minutes;
default 5;
description
"The maximum amount of unconnected time the
device will wait until establishing a
connection to the network manager again. The
device MAY establish a connection before this
time if it has data it needs to send to the
network manager. Note: this value differs from
the reconnection strategy's interval-secs
value.";
}
leaf linger-secs {
type uint8;
units seconds;
default 30;
description
"The amount of time the device should wait after
last receiving data from or sending data to the
network manager's endpoint before closing its
connection to it. This is an optimization to
prevent unnecessary connections.";
}
}
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}
}
}
}
grouping call-home-reconnection-strategy-config {
description
"Grouping for reconnection strategy.";
container reconnect-strategy {
description
"The reconnection strategy guides how a device reconnects
to an application, after losing a connection to it,
even if due to a reboot. The device starts with the
specified endpoint, tries to connect to it count-max
times, waiting interval-secs between each connection
attempt, before trying the next endpoint in the list
(round robin).";
leaf start-with {
type enumeration {
enum first-listed {
description
"Indicates that reconnections should start with
the first endpoint listed.";
}
enum last-connected {
description
"Indicates that reconnections should start with
the endpoint last connected to.";
}
}
default first-listed;
description
"Specifies which of the application's endpoints the
device should start with when trying to connect to
the application. If no previous connection has
ever been established, last-connected defaults to
the first endpoint listed.";
}
leaf interval-secs {
type uint8;
units seconds;
default 5;
description
"Specifies the time delay between connection attempts
to the same endpoint. Note: this value differs from
the periodic-connection's timeout-mins value.";
}
leaf count-max {
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type uint8;
default 3;
description
"Specifies the number times the device tries to
connect to a specific endpoint before moving on to
the next endpoint in the list (round robin).";
}
}
}
grouping trusted-ca-certs-grouping {
description
"Grouping for trusted-ca-certs container.";
container trusted-ca-certs {
description
"A list of Certificate Authority (CA) certificates that a
NETCONF server can use to authenticate a NETCONF client's
certificate. A client's certificate is authenticated if
its Issuer matches one of the configured trusted CA
certificates.";
leaf-list trusted-ca-cert {
type binary;
ordered-by system;
description
"The binary certificate structure, as
specified by RFC 5246, Section 7.4.6, i.e.,:
opaque ASN.1Cert<1..2^24>;
";
reference
"RFC 5246: The Transport Layer Security (TLS)
Protocol Version 1.2";
}
}
}
grouping trusted-client-certs-grouping {
description
"Grouping for trusted-client-certs container.";
container trusted-client-certs {
description
"A list of client certificates that a NETCONF server can
use to authenticate a NETCONF client's certificate. A
client's certificate is authenticated if it is an exact
match to a configured trusted client certificates.";
leaf-list trusted-client-cert {
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type binary;
ordered-by system;
description
"The binary certificate structure, as
specified by RFC 5246, Section 7.4.6, i.e.,:
opaque ASN.1Cert<1..2^24>;
";
reference
"RFC 5246: The Transport Layer Security (TLS)
Protocol Version 1.2";
}
}
}
// Objects for deriving NETCONF usernames from X.509
// certificates.
grouping cert-maps-grouping {
description
"Grouping for cert-maps container.";
container cert-maps {
if-feature tls-map-certificates;
uses x509c2n:cert-to-name;
description
"The cert-maps container is used by a NETCONF server to
map the NETCONF client's presented X.509 certificate to
a NETCONF username.
If no matching and valid cert-to-name list entry can be
found, then the NETCONF server MUST close the connection,
and MUST NOT accept NETCONF messages over it.";
}
}
// Objects for deriving NETCONF usernames from TLS
// pre-shared keys.
grouping psk-maps-grouping {
description
"Grouping for psk-maps container.";
container psk-maps {
if-feature tls-map-pre-shared-keys;
description
"During the TLS Handshake, the client indicates which
key to use by including a PSK identity in the TLS
ClientKeyExchange message. On the NETCONF server side,
this PSK identity is used to look up an entry in the psk-map
list. If such an entry is found, and the pre-shared keys
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match, then the client is authenticated. The NETCONF
server uses the value from the user-name leaf in the
psk-map list as the NETCONF username. If the NETCONF
server cannot find an entry in the psk-map list, or if
the pre-shared keys do not match, then the NETCONF
server terminates the connection.";
reference
"RFC 4279: Pre-Shared Key Ciphersuites for Transport Layer
Security (TLS)";
list psk-map {
key psk-identity;
description
"List a pre-shared key mappings.";
leaf psk-identity {
type string;
description
"The PSK identity encoded as a UTF-8 string. For
details how certain common PSK identity formats can
be encoded in UTF-8, see section 5.1. of RFC 4279.";
reference
"RFC 4279: Pre-Shared Key Ciphersuites for Transport
Layer Security (TLS)";
}
leaf user-name {
type nacm:user-name-type;
mandatory true;
description
"The NETCONF username associated with this PSK
identity.";
}
leaf not-valid-before {
type yang:date-and-time;
description
"This PSK identity is not valid before the given date
and time.";
}
leaf not-valid-after {
type yang:date-and-time;
description
"This PSK identity is not valid after the given date
and time.";
}
leaf key {
type yang:hex-string;
mandatory true;
nacm:default-deny-all;
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description
"The key associated with the PSK identity";
reference
"RFC 4279: Pre-Shared Key Ciphersuites for Transport
Layer Security (TLS)";
}
}
}
}
}
<CODE ENDS>
4. Keep-Alives for SSH and TLS
One the objectives listed above, Keep-Alives for Persistent
Connections (Section 2.4.6) indicates a need for a "keep-alive"
mechanism. This section specifies how the NETCONF keep-alive
mechanism is to be implemented.
Both SSH and TLS have the ability to support keep-alives. Using
these mechanisms, the keep-alive messages are sent inside the
encrypted tunnel, thus thwarting spoof attacks.
4.1. SSH
The SSH keep-alive solution that is expected to be used when
configured using the data model defined in this document is
ubiquitous in practice, though never being explicitly defined in an
RFC. The strategy used is to purposely send a malformed request
message with a flag set to ensure a response. More specifically, per
section 4 of [RFC4253], either SSH peer can send a
SSH_MSG_GLOBAL_REQUEST message with "want reply" set to '1' and that,
if there is an error, will get back a SSH_MSG_REQUEST_FAILURE
response. Similarly, section 5 of [RFC4253] says that either SSH
peer can send a SSH_MSG_CHANNEL_REQUEST message with "want reply" set
to '1' and that, if there is an error, will get back a
SSH_MSG_CHANNEL_FAILURE response.
To ensure that the request will fail, current implementations send an
invalid "request name" or "request type", respectively. Abiding to
the extensibility guidelines specified in Section 6 of [RFC4251],
these implementations use the "name@domain". For instance, when
configured to send keep-alives, OpenSSH sends the string
"keepalive@openssh.com". In order to remain compatible with existing
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implementations, this draft does not require a specific "request
name" or "request type" string be used.
4.2. TLS
The TLS keep-alive solution is defined in [RFC6520]. This solution
allows both peers to advertise if they can receive heartbeat request
messages from its peer. For standard NETCONF over TLS connections,
devices SHOULD advertise "peer_allowed_to_send", as per [RFC6520].
This advertisement is not a "MUST" in order to grandfather existing
NETCONF over TLS implementations. For NETCONF over TLS Call Home,
the network management system MUST advertise "peer_allowed_to_send"
per [RFC6520]. This is a "MUST" so as to ensure devices can depend
in it always being there for call home connections, which is
conveniently when keep-alives are needed the most.
5. Security Considerations
The YANG modules defined in this memo are designed to be accessed via
the NETCONF protocol [RFC6241]. Authorization for access to specific
portions of conceptual data and operations within this module is
provided by the NETCONF access control model (NACM) [RFC6536].
There are a number of data nodes defined in the "ietf-netconf-server"
and "ietf-system-tls-auth" YANG modules which 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 and read operations to these data nodes can have
a negative effect on network operations. It is thus important to
control write and read access to these data nodes. Below are the
data nodes and their sensitivity/vulnerability.
ietf-netconf-server:
o None.
ietf-system-tls-auth:
o /system/authentication/tls/psk-maps/psk-map/user-name: This leaf
node contains a user name that some deployments may consider
sensitive information.
o /system/authentication/tls/psk-maps/psk-map/key: This leaf node
contains a shared key that remote clients use to authenticate
themselves to the system. This value should not be readable or
writable by anyone by default.
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6. IANA Considerations
This document registers two URIs in the IETF XML registry [RFC2119].
Following the format in [RFC3688], the following registrations are
requested:
URI: urn:ietf:params:xml:ns:yang:ietf-netconf-server
Registrant Contact: The NETCONF WG of the IETF.
XML: N/A, the requested URI is an XML namespace.
URI: urn:ietf:params:xml:ns:yang:ietf-system-tle-auth
Registrant Contact: The NETCONF WG of the IETF.
XML: N/A, the requested URI is an XML namespace.
This document registers two YANG modules in the YANG Module Names
registry [RFC6020].
name: ietf-netconf-server
namespace: urn:ietf:params:xml:ns:yang:ietf-netconf-server
prefix: ncserver
reference: RFC XXXX
name: ietf-system-tls-auth
namespace: urn:ietf:params:xml:ns:yang:ietf-system-tls-auth
prefix: sys-tls-auth
reference: RFC XXXX
7. Other Considerations
The YANG module define herein does not itself support virtual routing
and forwarding (VRF). It is expected that external modules will
augment in VRF designations when needed.
8. Acknowledgements
The authors would like to thank for following for lively discussions
on list and in the halls (ordered by last name): Andy Bierman, Martin
Bjorklund, Benoit Claise, David Lamparter, Alan Luchuk, Ladislav
Lhotka, Radek Krejci, Tom Petch, and Phil Shafer.
Juergen Schoenwaelder and was partly funded by Flamingo, a Network of
Excellence project (ICT-318488) supported by the European Commission
under its Seventh Framework Programme.
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9. References
9.1. Normative References
[RFC2119] Bradner, S., "Key words for use in RFCs to Indicate
Requirement Levels", BCP 14, RFC 2119, March 1997.
[RFC4251] Ylonen, T. and C. Lonvick, "The Secure Shell (SSH)
Protocol Architecture", RFC 4251, January 2006.
[RFC4253] Ylonen, T. and C. Lonvick, "The Secure Shell (SSH)
Transport Layer Protocol", RFC 4253, January 2006.
[RFC6020] Bjorklund, M., "YANG - A Data Modeling Language for the
Network Configuration Protocol (NETCONF)", RFC 6020,
October 2010.
[RFC6241] Enns, R., Bjorklund, M., Schoenwaelder, J., and A.
Bierman, "Network Configuration Protocol (NETCONF)", RFC
6241, June 2011.
[RFC6242] Wasserman, M., "Using the NETCONF Protocol over Secure
Shell (SSH)", RFC 6242, June 2011.
[RFC6520] Seggelmann, R., Tuexen, M., and M. Williams, "Transport
Layer Security (TLS) and Datagram Transport Layer Security
(DTLS) Heartbeat Extension", RFC 6520, February 2012.
[RFC6536] Bierman, A. and M. Bjorklund, "Network Configuration
Protocol (NETCONF) Access Control Model", RFC 6536, March
2012.
[RFC6991] Schoenwaelder, J., "Common YANG Data Types", RFC 6991,
July 2013.
[draft-ietf-netconf-call-home]
Watsen, K., "NETCONF Call Home", draft-ieft-netconf-call-
home-00 (work in progress), 2014.
[draft-ietf-netmod-snmp-cfg]
Bjorklund, M. and J. Schoenwaelder, "A YANG Data Model for
SNMP Configuration", draft-ietf-netmod-snmp-cfg-03 (work
in progress), November 2013.
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[rfc5539bis]
Badra, M., Luchuk, A., and J. Schoenwaelder, "Using the
NETCONF Protocol over Transport Layer Security (TLS)",
draft-ietf-netconf-rfc5539bis-04 (work in progress),
October 2013.
9.2. Informative References
[RFC3688] Mealling, M., "The IETF XML Registry", BCP 81, RFC 3688,
January 2004.
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Appendix A. Examples
A.1. SSH Transport Configuration
<netconf-server xmlns="urn:ietf:params:xml:ns:yang:ietf-netconf-server">
<listen>
<name>foo bar</name>
<ssh>
<port>831</port>
</ssh>
</listen>
<call-home>
<name>config-mgr</name>
<ssh>
<endpoints>
<endpoint>
<name>east-data-center</name>
<address>11.22.33.44</address>
</endpoint>
<endpoint>
<name>west-data-center</name>
<address>55.66.77.88</address>
</endpoint>
</endpoints>
</ssh>
</call-home>
</netconf-server>
A.2. TLS Transport Configuration
<netconf-server xmlns="urn:ietf:params:xml:ns:yang:ietf-netconf-server">
<listen>
<name>foo bar</name>
<ssh>
<port>831</port>
</ssh>
</listen>
<call-home>
<name>config-mgr</name>
<tls>
<endpoints>
<endpoint>
<name>east-data-center</name>
<address>11.22.33.44</address>
</endpoint>
<endpoint>
<name>west-data-center</name>
<address>55.66.77.88</address>
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</endpoint>
</endpoints>
</tls>
</call-home>
<tls-client-auth>
<trusted-ca-certs>
<trusted-ca-cert>
QW4gRWFzdGVyIGVnZywgZm9yIHRob3NlIHdobyBtaWdodCBsb29rICA6KQo=
</trusted-ca-cert>
</trusted-ca-certs>
<trusted-client-certs>
<trusted-client-cert>
SSBhbSB0aGUgZWdnIG1hbiwgdGhleSBhcmUgdGhlIGVnZyBtZW4uCg==
</trusted-client-cert>
<trusted-client-cert>
SSBhbSB0aGUgd2FscnVzLCBnb28gZ29vIGcnam9vYi4K
</trusted-client-cert>
</trusted-client-certs>
<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-to-name>
<id>2</id>
<fingerprint>11:0A:05:11:00</fingerprint>
<map-type>x509c2n:specified</map-type>
<name>Joe Cool</name>
</cert-to-name>
</cert-maps>
<psk-maps>
<psk-map>
<psk-identity>a8gc8]klh59</psk-identity>
<user-name>admin</user-name>
<not-valid-before>2013-01-01T00:00:00Z</not-valid-before>
<not-valid-after>2014-01-01T00:00:00Z</not-valid-after>
</psk-map>
</psk-maps>
</tls-client-auth>
</netconf-server>
Appendix B. Change Log
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B.1. 00 to 01
o Restructured document so it flows better
o Added trusted-ca-certs and trusted-client-certs objects into the
ietf-system-tls-auth module
B.2. 01 to 02
o removed the "one-to-many" construct
o removed "address" as a key field
o removed "network-manager" terminology
o moved open issues to github issues
o brought TLS client auth back into model
B.3. 02 to 03
o fixed tree diagrams and surrounding text
Appendix C. Open Issues
Please see: https://github.com/netconf-wg/server-model/issues.
Authors' Addresses
Kent Watsen
Juniper Networks
EMail: kwatsen@juniper.net
Juergen Schoenwaelder
Jacobs University Bremen
EMail: j.schoenwaelder@jacobs-university.de
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