NETCONF Working Group K. Watsen
Internet-Draft Juniper Networks
Intended status: Standards Track J. Schoenwaelder
Expires: December 03, 2014 Jacobs University Bremen
June 2014
NETCONF Server Configuration Model
draft-ietf-netconf-server-model-01
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 December 03, 2014.
Copyright Notice
Copyright (c) 2014 IETF Trust and the persons identified as the
document authors. All rights reserved.
Watsen & Schoenwaelder Expires December 03, 2014 [Page 1]
Internet-Draft NETCONF Server Configuration Model June 2014
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
the Trust Legal Provisions and are provided without warranty as
described in the Simplified BSD License.
Table of Contents
1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . 3
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 . . . . . . . . . 4
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 . . 5
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 . . . . . . . . . . . . . . . . . . . . . . . 7
4. Keep-Alives for SSH and TLS . . . . . . . . . . . . . . . . . 16
4.1. SSH . . . . . . . . . . . . . . . . . . . . . . . . . . . 16
4.2. TLS . . . . . . . . . . . . . . . . . . . . . . . . . . . 17
5. User Authentication for TLS . . . . . . . . . . . . . . . . . 17
5.1. Introduction . . . . . . . . . . . . . . . . . . . . . . 17
5.2. Data Model Overview . . . . . . . . . . . . . . . . . . . 17
5.3. YANG Module . . . . . . . . . . . . . . . . . . . . . . . 18
6. Security Considerations . . . . . . . . . . . . . . . . . . . 23
7. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 24
8. Other Considerations . . . . . . . . . . . . . . . . . . . . 24
9. Acknowledgements . . . . . . . . . . . . . . . . . . . . . . 24
10. References . . . . . . . . . . . . . . . . . . . . . . . . . 24
10.1. Normative References . . . . . . . . . . . . . . . . . . 24
10.2. Informative References . . . . . . . . . . . . . . . . . 26
Appendix A. Example: SSH Transport Configuration . . . . . . . . 26
Appendix B. Example: TLS Transport Configuration . . . . . . . . 27
Appendix C. Example: TLS Authentication Configuration . . . . . 28
Appendix D. Change Log . . . . . . . . . . . . . . . . . . . . . 29
Watsen & Schoenwaelder Expires December 03, 2014 [Page 2]
Internet-Draft NETCONF Server Configuration Model June 2014
D.1. I-D to 00 . . . . . . . . . . . . . . . . . . . . . . . . 29
D.2. 00 to 01 . . . . . . . . . . . . . . . . . . . . . . . . 29
Appendix E. Open Issues . . . . . . . . . . . . . . . . . . . . 29
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
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
[I-D.ietf-netconf-rfc5539bis], and be extensible to support future
transports as necessary.
Watsen & Schoenwaelder Expires December 03, 2014 [Page 3]
Internet-Draft NETCONF Server Configuration Model June 2014
Since implementations may not support all transports, the module
should use YANG "feature" statements so that implementation 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.
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 ([I-D.ietf-netconf-rfc5539bis] and
[draft-ieft-netconf-reverse-ssh]). 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
Watsen & Schoenwaelder Expires December 03, 2014 [Page 4]
Internet-Draft NETCONF Server Configuration Model June 2014
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
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.
Watsen & Schoenwaelder Expires December 03, 2014 [Page 5]
Internet-Draft NETCONF Server Configuration Model June 2014
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.
3. Data Model
3.1. Overview
To enable transports to configure listening on one or more ports in a
common way, this grouping is defined. This grouping defines SSH and
TLS specific containers, each of which refines the default listening
port appropriately. Further, each of these transport specific
containers use a feature statement, enabling NETCONF servers to
accurately advertise what they support.
module: ietf-netconf-server
+--rw netconf-server
+--rw listen
+--rw ssh {ssh-listen}?
| +--rw (one-or-many)?
| +--:(one-port)
| | +--rw port? inet:port-number
| +--:(many-ports)
| +--rw interface* [address]
| +--rw address inet:host
| +--rw port? inet:port-number
+--rw tls {tls-listen}?
+--rw (one-or-many)?
+--:(one-port)
| +--rw port? inet:port-number
+--:(many-ports)
+--rw interface* [address]
+--rw address inet:host
+--rw port? inet:port-number
To enable transports to configure initiating connections to remote
applications in a common way, this grouping is defined. This
grouping configures a list of network-managers, each with some
transport-specific configuration augmented in. Each of the transport
specific containers use a feature statement, enabling NETCONF servers
to accurately advertise what they support.
module: ietf-netconf-server
+--rw netconf-server
Watsen & Schoenwaelder Expires December 03, 2014 [Page 6]
Internet-Draft NETCONF Server Configuration Model June 2014
+--rw call-home
+--rw network-managers
+--rw network-manager* [name]
+--rw name string
+--rw description? string
+--rw endpoints
| +--rw endpoint* [address]
| +--rw address inet:host
| +--rw port? inet:port-number
+--rw transport
| +--rw ssh {ssh-call-home}?
| | +--rw host-keys
| | +--rw host-key* [name]
| | +--rw name string
| +--rw tls! {tls-call-home}?
+--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
3.2. YANG Module
This YANG module imports YANG types from [RFC6991].
RFC Ed.: update the date below with the date of RFC publication
and remove this note.
<CODE BEGINS> file "ietf-netconf-server.@2014-05-16.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
}
Watsen & Schoenwaelder Expires December 03, 2014 [Page 7]
Internet-Draft NETCONF Server Configuration Model June 2014
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 "2014-01-24" {
description
"Initial version";
reference
"RFC XXXX: NETCONF Server Configuration Model";
}
// Features
feature ssh {
Watsen & Schoenwaelder Expires December 03, 2014 [Page 8]
Internet-Draft NETCONF Server Configuration Model June 2014
description
"A NETCONF server implements this feature if it supports NETCONF
over Secure Shell (SSH).";
reference
"RFC 6242: Using the NETCONF Protocol over Secure Shell (SSH)";
}
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 {
description
"A NETCONF server implements this feature if it supports NETCONF
over Transport Layer Security (TLS).";
reference
"RFC XXXX: NETCONF over Transport Layer Security (TLS)";
}
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.";
}
// Groupings
grouping one-or-many-config {
description
"Provides a choice of configuring one of more ports
to listen for incoming client connections.";
Watsen & Schoenwaelder Expires December 03, 2014 [Page 9]
Internet-Draft NETCONF Server Configuration Model June 2014
choice one-or-many {
default one-port;
case one-port {
leaf port {
type inet:port-number;
description
"The port number the NETCONF server listens on on all
interfaces.";
}
}
case many-ports {
list interface {
key "address";
leaf address {
type inet:host;
mandatory true;
description
"The local IP address 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 network-managers-config {
container network-managers {
description
"A list of network managers the device initates connections
to. The configuration for each network manager specifies
its details, including its endpoints, the type of
connection to maintain, and the reconnection strategy
to use.";
list network-manager {
key name;
leaf name {
type string {
length 1..64; // XXX why these limits?
}
Watsen & Schoenwaelder Expires December 03, 2014 [Page 10]
Internet-Draft NETCONF Server Configuration Model June 2014
mandatory true;
description
"An arbitrary name for the network manager the device
is connecting to.";
}
leaf description {
type string;
description
"An optional description for the network manager.";
}
container endpoints {
description
"An ordered listing of the network manager's
endpoints that the device should attempt connecting
to. Defining more than one enables the device to
support high-availability scenarios.";
list endpoint {
key address;
min-elements 1;
ordered-by user;
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.";
}
}
}
container transport {
}
container connection-type {
description
"Indicates the network manager's preference for how the
device's connection is maintained.";
choice connection-type {
default persistent-connection;
Watsen & Schoenwaelder Expires December 03, 2014 [Page 11]
Internet-Draft NETCONF Server Configuration Model June 2014
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 {
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
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
Watsen & Schoenwaelder Expires December 03, 2014 [Page 12]
Internet-Draft NETCONF Server Configuration Model June 2014
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.";
}
}
}
}
}
// XXX
// Should we have something smarter as the reconnect
// strategy, e.g. an exponential backoff?
container reconnect-strategy {
description
"The reconnection strategy guides how a device reconnects
to an network manager, 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
Watsen & Schoenwaelder Expires December 03, 2014 [Page 13]
Internet-Draft NETCONF Server Configuration Model June 2014
attempt, before trying the next endpoint in the list
(round robin).";
leaf start-with {
type enumeration {
enum first-listed { value 1; }
enum last-connected { value 2; }
}
default first-listed;
description
"Specifies which of the network manager's endpoints the
device should start with when trying to connect to
the network manager. 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 {
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 listen-config {
description
"Provides the configuration of the NETCONF server to
open one or more ports to listen for incoming client
connections.";
container ssh {
if-feature ssh-listen;
uses one-or-many-config {
refine one-or-many/one-port/port {
default 830;
}
Watsen & Schoenwaelder Expires December 03, 2014 [Page 14]
Internet-Draft NETCONF Server Configuration Model June 2014
refine one-or-many/many-ports/interface/port {
default 830;
}
}
}
container tls {
if-feature tls-listen;
uses one-or-many-config {
refine one-or-many/one-port/port {
default 6513;
}
refine one-or-many/many-ports/interface/port {
default 6513;
}
}
}
}
grouping call-home-config {
description
"Provides the configuration of the NETCONF call-home
clients to connect to, the overall call-home policy,
and the reconnect strategy.";
uses network-managers-config {
augment network-managers/network-manager/transport {
container ssh {
if-feature ssh-call-home;
container host-keys {
description
"An ordered listing of the SSH host keys the
device should advertise to the network manager.";
list host-key {
key name;
min-elements 1; // requires 'ssh' element?
ordered-by user;
leaf name {
type string;
mandatory true;
description
"The name of a host key the device should
advertise during the SSH key exchange.";
}
}
}
}
container tls {
Watsen & Schoenwaelder Expires December 03, 2014 [Page 15]
Internet-Draft NETCONF Server Configuration Model June 2014
if-feature tls-call-home;
presence "Enables call home using TLS when configured.";
}
}
}
}
// Module's top-level container
container netconf-server {
description
"Top-level container for NETCONF server configuration.";
container listen {
uses listen-config;
}
container call-home {
uses call-home-config;
}
}
}
<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
Watsen & Schoenwaelder Expires December 03, 2014 [Page 16]
Internet-Draft NETCONF Server Configuration Model June 2014
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
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. User Authentication for TLS
5.1. Introduction
The NETCONF Server Module defined in this draft focuses on the
configuration the SSH and TLS transports. This module does not
define a means to configure User Authentication, as that is a stated
focus for [draft-ietf-netmod-system-mgmt], however, that draft does
not define configuration nodes for TLS client authentication. Thus,
this draft also includes the following YANG module to augment TLS
client authentication into the "ietf-system" module defined in
[draft-ietf-netmod-system-mgmt].
5.2. Data Model Overview
This data model augments the "ietf-system" module defined in
[draft-ietf-netmod-system-mgmt] by adding some configuration nodes
under its "/system/authentication" subtree.
module: ietf-system-tls-auth
augment /sys:system/sys:authentication:
+--rw tls
Watsen & Schoenwaelder Expires December 03, 2014 [Page 17]
Internet-Draft NETCONF Server Configuration Model June 2014
+--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
5.3. YANG Module
This YANG module imports YANG extensions from [RFC6536], and imports
YANG types from [RFC6991] and a YANG grouping from
[I-D.ietf-netmod-snmp-cfg].
RFC Ed.: update the date below with the date of RFC publication
and remove this note.
<CODE BEGINS> file "ietf-system-tls-auth.@2014-05-16.yang"
module ietf-system-tls-auth {
namespace "urn:ietf:params:xml:ns:yang:ietf-system-tls-auth";
prefix "system-tls-auth";
import ietf-system { // draft-ietf-netmod-system-mgmt
prefix "sys";
}
import ietf-netconf-acm {
prefix nacm; // RFC 6536
}
import ietf-yang-types {
prefix yang; // RFC 6991
}
import ietf-x509-cert-to-name {
prefix x509c2n; // I-D.ietf-netconf-rfc5539bis
}
organization
Watsen & Schoenwaelder Expires December 03, 2014 [Page 18]
Internet-Draft NETCONF Server Configuration Model June 2014
"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>
Juergen Schoenwaelder
<mailto:j.schoenwaelder@jacobs-university.de>";
description
"This module augments the ietf-system module in order to
add TLS authentication configuration nodes to the
'authentication' container.
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 "2014-05-24" {
description
"Initial version";
reference
"RFC XXXX: NETCONF Server Configuration Model";
}
Watsen & Schoenwaelder Expires December 03, 2014 [Page 19]
Internet-Draft NETCONF Server Configuration Model June 2014
// Features
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.";
}
grouping tls-global-config {
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";
}
}
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 one of the configured trusted client certificates.";
leaf-list trusted-client-cert {
Watsen & Schoenwaelder Expires December 03, 2014 [Page 20]
Internet-Draft NETCONF Server Configuration Model June 2014
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.
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.
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
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
Watsen & Schoenwaelder Expires December 03, 2014 [Page 21]
Internet-Draft NETCONF Server Configuration Model June 2014
"RFC 4279: Pre-Shared Key Ciphersuites for Transport Layer
Security (TLS)";
list psk-map {
key psk-identity;
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;
description
"The key associated with the PSK identity";
reference
"RFC 4279: Pre-Shared Key Ciphersuites for Transport
Layer Security (TLS)";
}
}
}
}
Watsen & Schoenwaelder Expires December 03, 2014 [Page 22]
Internet-Draft NETCONF Server Configuration Model June 2014
augment "/sys:system/sys:authentication" {
container tls {
uses tls-global-config;
}
}
}
<CODE ENDS>
6. 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.
Watsen & Schoenwaelder Expires December 03, 2014 [Page 23]
Internet-Draft NETCONF Server Configuration Model June 2014
7. 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
8. 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.
9. 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.
10. References
10.1. Normative References
Watsen & Schoenwaelder Expires December 03, 2014 [Page 24]
Internet-Draft NETCONF Server Configuration Model June 2014
[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., Ed., "YANG - A Data Modeling Language for
the Network Configuration Protocol (NETCONF) ", RFC 6020,
October 2010.
[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.
[RFC6241] Enns, R., Ed., Bjorklund, M., Ed., Schoenwaelder, J., Ed.,
and A. Bierman, Ed., "NETCONF Configuration Protocol", RFC
6241, June 2011.
[RFC6242] Wasserman, M., "Using the NETCONF Protocol over Secure
Shell (SSH)", RFC 6242, June 2011.
[I-D.ietf-netconf-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.
[I-D.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.
[draft-ieft-netconf-reverse-ssh]
Watsen, K., "NETCONF over SSH Call Home ", draft-ieft-
netconf-reverse-ssh-00 (work in progress), May 2014.
[draft-ietf-netmod-system-mgmt]
Watsen & Schoenwaelder Expires December 03, 2014 [Page 25]
Internet-Draft NETCONF Server Configuration Model June 2014
Bierman, A., "A YANG Data Model for System Management ",
draft-ieft-netmod-system-mgmt-16 (work in progress), May
2014.
10.2. Informative References
[RFC3688] Mealling, M., "The IETF XML Registry", BCP 81, RFC 3688,
January 2004.
Appendix A. Example: SSH Transport Configuration
<netconf-server xmlns="urn:ietf:params:xml:ns:yang:ietf-netconf-server">
<listen>
<ssh>
<port>831</port>
</ssh>
</listen>
<call-home>
<network-managers>
<network-manager>
<name>config-mgr</name>
<description>
This entry requests the device to periodically
connect to the network manager.
</description>
<endpoints>
<endpoint>
<address>config-mgr1.example.com</address>
</endpoint>
<endpoint>
<address>config-mgr2.example.com</address>
</endpoint>
</endpoints>
<transport>
<ssh>
<host-keys>
<host-key>
<name>ssh_host_key_cert</name>
</host-key>
<host-key>
<name>ssh_host_key_cert2</name>
</host-key>
</host-keys>
</ssh>
</transport>
<connection-type>
<periodic>
<timeout-mins>5</timeout-mins>
Watsen & Schoenwaelder Expires December 03, 2014 [Page 26]
Internet-Draft NETCONF Server Configuration Model June 2014
<linger-secs>10</linger-secs>
</periodic>
</connection-type>
<reconnect-strategy>
<start-with>last-connected</start-with>
<interval-secs>10</interval-secs>
<count-max>3</count-max>
</reconnect-strategy>
</network-manager>
</network-managers>
</call-home>
</netconf-server>
Appendix B. Example: TLS Transport Configuration
<netconf-server xmlns="urn:ietf:params:xml:ns:yang:ietf-netconf-server">
<listen>
<tls>
<interface>
<address>192.0.2.1</address>
<port>6514</port>
</interface>
</tls>
</listen>
<call-home>
<network-managers>
<network-manager>
<name>log-monitor</name>
<description>
This entry requests the device to maintain a
persistent connect to the network manager.
</description>
<endpoints>
<endpoint>
<address>log-monitor1.example.com</address>
</endpoint>
<endpoint>
<address>log-monitor2.example.com</address>
</endpoint>
</endpoints>
<transport>
<tls/>
</transport>
<connection-type>
<persistent>
<keep-alives>
<interval-secs>5</interval-secs>
<count-max>3</count-max>
Watsen & Schoenwaelder Expires December 03, 2014 [Page 27]
Internet-Draft NETCONF Server Configuration Model June 2014
</keep-alives>
</persistent>
</connection-type>
<reconnect-strategy>
<start-with>first-listed</start-with>
<interval-secs>10</interval-secs>
<count-max>4</count-max>
</reconnect-strategy>
</network-manager>
</network-managers>
</call-home>
</netconf-server>
Appendix C. Example: TLS Authentication Configuration
<system xmlns="urn:ietf:params:xml:ns:yang:ietf-system">
<authentication>
<tls xmlns="urn:ietf:params:xml:ns:yang:ietf-system-tls-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>
Watsen & Schoenwaelder Expires December 03, 2014 [Page 28]
Internet-Draft NETCONF Server Configuration Model June 2014
<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>
</authentication>
</system>
Appendix D. Change Log
D.1. I-D to 00
o Changed title to "NETCONF Server Configuration Model"
o Mapped inbound/outbound to listen/call-home
o Restructured YANG module to place transport selection deeper into
the tree, providing a more intuitive data model
o Added section "Keep-Alives for SSH and TLS"
o Updated the Security Considerations section
o Added text for supporting VRFs via augments
o Factored the TLS-AUTH config into another module augmenting the
"ietf-system" module
D.2. 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
Appendix E. Open Issues
o NETCONF implementations typically have config parameters such as
session timeouts or hello timeouts. Shall they be included in
this model?
Watsen & Schoenwaelder Expires December 03, 2014 [Page 29]
Internet-Draft NETCONF Server Configuration Model June 2014
o Do we need knobs to enable/disable call-home without the need to
remove all the call-home client configuration?
Authors' Addresses
Kent Watsen
Juniper Networks
EMail: kwatsen@juniper.net
Juergen Schoenwaelder
Jacobs University Bremen
EMail: j.schoenwaelder@jacobs-university.de
Watsen & Schoenwaelder Expires December 03, 2014 [Page 30]
