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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: April 29, 2015 Jacobs University Bremen
October 26, 2014
NETCONF Server Configuration Model
draft-ietf-netconf-server-model-04
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 call-home is supported, 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 April 29, 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
the Trust Legal Provisions and are provided without warranty as
described in the Simplified BSD License.
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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. Enable each transport to select which keys to use . . . . 4
2.3. Support authenticating client-certificates . . . . . . . 4
2.4. Support mapping authenticated client-certificates to
usernames . . . . . . . . . . . . . . . . . . . . . . . . 4
2.5. Support both Listening for connections and Call Home . . 4
2.6. For Call Home connections . . . . . . . . . . . . . . . . 4
2.6.1. Support more than one application . . . . . . . . . . 4
2.6.2. Support applications having more than one server . . 5
2.6.3. Support a reconnection strategy . . . . . . . . . . . 5
2.6.4. Support both persistent and periodic connections . . 5
2.6.5. Reconnection strategy for periodic connections . . . 5
2.6.6. Keep-alives for persistent connections . . . . . . . 5
2.6.7. Customizations for periodic connections . . . . . . . 6
3. Data Model . . . . . . . . . . . . . . . . . . . . . . . . . 6
3.1. Overview . . . . . . . . . . . . . . . . . . . . . . . . 6
3.1.1. The "session-options" subtree . . . . . . . . . . . . 6
3.1.2. The "listen" subtree . . . . . . . . . . . . . . . . 6
3.1.3. The "call-home" subtree . . . . . . . . . . . . . . . 7
3.1.4. The "ssh" subtree . . . . . . . . . . . . . . . . . . 9
3.1.5. The "tls" subtree . . . . . . . . . . . . . . . . . . 9
3.2. YANG Module . . . . . . . . . . . . . . . . . . . . . . . 10
4. Implementation strategy for keep-alives . . . . . . . . . . . 24
4.1. Keep-alives for SSH . . . . . . . . . . . . . . . . . . . 24
4.2. Keep-alives for TLS . . . . . . . . . . . . . . . . . . . 25
5. Security Considerations . . . . . . . . . . . . . . . . . . . 25
6. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 26
7. Other Considerations . . . . . . . . . . . . . . . . . . . . 26
8. Acknowledgements . . . . . . . . . . . . . . . . . . . . . . 26
9. References . . . . . . . . . . . . . . . . . . . . . . . . . 27
9.1. Normative References . . . . . . . . . . . . . . . . . . 27
9.2. Informative References . . . . . . . . . . . . . . . . . 28
Appendix A. Examples . . . . . . . . . . . . . . . . . . . . . . 29
A.1. SSH Transport Configuration + State . . . . . . . . . . . 29
A.2. TLS Transport Configuration + State . . . . . . . . . . . 31
Appendix B. Change Log . . . . . . . . . . . . . . . . . . . . . 32
B.1. 00 to 01 . . . . . . . . . . . . . . . . . . . . . . . . 33
B.2. 01 to 02 . . . . . . . . . . . . . . . . . . . . . . . . 33
B.3. 02 to 03 . . . . . . . . . . . . . . . . . . . . . . . . 33
B.4. 03 to 04 . . . . . . . . . . . . . . . . . . . . . . . . 33
Appendix C. Open Issues . . . . . . . . . . . . . . . . . . . . 34
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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 the
server listens 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 server 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.
Because implementations may not support all transports, the module
should use YANG "feature" statements so that implementations can
accurately advertise which transports are supported.
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2.2. Enable each transport to select which keys to use
Systems may have a multiplicity of host-keys or server-certificates
from which subsets are configured for specific uses. For instance, a
system may want to use one set of SSH host-keys when listening on
port 830, and a different set of SSH host-keys when calling home.
2.3. Support authenticating client-certificates
When certificates are used to authenticate NETCONF clients, there is
a need to configure the system to know how to authenticate the
certificates. The system should be able to do this either by using
path-validation to a configured trust anchor or by matching the
client-certificate to one previously configured.
2.4. Support mapping authenticated client-certificates to usernames
Some transports (e.g., TLS) need additional support to map
authenticated transport-level sessions to a NETCONF username. The
NETCONF server model defined herein should define an ability for this
mapping to be configured."
2.5. 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.
Because 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.
2.6. For Call Home connections
The following objectives only pertain to call home connections.
2.6.1. 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.
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2.6.2. 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 application's
servers.
2.6.3. 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.
2.6.4. 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.
2.6.5. 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.
2.6.6. 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
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application requirements, and therefore keep-alive settings should be
configurable on a per-application basis.
2.6.7. 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.
3. Data Model
3.1. Overview
3.1.1. The "session-options" subtree
module: ietf-netconf-server
+--rw netconf-server
+--rw session-options
+--rw hello-timeout? uint32
+--rw idle-timeout? uint32
The above subtree illustrates how this YANG module enables
configuration of NETCONF session options, independent of any
transport or connection strategy. Please see the YANG module
(Section 3.2) for a complete description of these configuration
knobs.
3.1.2. The "listen" subtree
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module: ietf-netconf-server
+--rw netconf-server
+--rw listen {"(ssh-listen or tls-listen)"}? // YANG 1.1 syntax
+--rw max-sessions? uint16
+--rw endpoint* [name]
+--rw name string
+--rw (transport)
| +--:(ssh) {ssh-listen}?
| | +--rw ssh
| | +--rw address? inet:ip-address
| | +--rw port? inet:port-number
| | +--rw host-keys
| | +--rw host-key* string
| +--:(tls) {tls-listen}?
| +--rw tls
| +--rw address? inet:ip-address
| +--rw port? inet:port-number
| +--rw certificates
| +--rw certificate* string
+--rw keep-alives
+--rw interval-secs? uint8
+--rw count-max? uint8
The above 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.
3.1.3. The "call-home" subtree
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module: ietf-netconf-server
+--rw netconf-server
+--rw call-home {"(ssh-call-home or tls-call-home)"}? // YANG 1.1 syntax
+--rw application* [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-keys
| | +--rw host-key* 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 certificates
| +--rw certificate* string
+--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 above 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
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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.
3.1.4. The "ssh" subtree
module: ietf-netconf-server
+--rw netconf-server
+--rw ssh
+--ro host-keys
+--ro host-key* [name]
+--ro name string
+--ro format-identifier string
+--ro data binary
+--ro fingerprint string
The above subtree illustrates how this YANG module provides SSH state
independent of if the NETCONF server if listening or calling home.
This data-model provides a read-only listing of currently configured
TLC certificates.
3.1.5. The "tls" subtree
module: ietf-netconf-server
+--rw netconf-server
+--rw tls
+--ro certificates
| +--ro certificate* [name]
| +--ro name string
| +--ro data binary
+--rw client-auth
+--rw trusted-ca-certs
| +--rw trusted-ca-cert* binary
+--rw trusted-client-certs
| +--rw trusted-client-cert* binary
+--rw cert-maps
+--rw cert-to-name* [id]
+--rw id uint32
+--rw fingerprint x509c2n:tls-fingerprint
+--rw map-type identityref
+--rw name string
The above subtree illustrates how this YANG module provides TLS state
and enables TLS configuration independent of if the NETCONF server if
listening or calling home. This data-model provides 1) a read-only
listing of currently configured TLC certificates and 2) an ability to
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configure how client-certificates are authenicated and how
authenticated client-certificates are mapped to NETCONF user names.
3.2. YANG Module
This YANG module imports YANG types from [RFC6991], 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@2014-10-26.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-x509-cert-to-name {
prefix x509c2n; // draft-ietf-netmod-snmp-cfg
}
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.
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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 "2014-10-26" { // YYYY-MM-DD
description
"Initial version";
reference
"RFC XXXX: NETCONF Server Configuration Model";
}
// Features
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.";
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}
// top-level container (groupings below)
container netconf-server {
description
"Top-level container for NETCONF server configuration.";
uses session-options-container;
uses listen-container;
uses call-home-container;
uses ssh-container;
uses tls-container;
}
grouping session-options-container {
description
"";
container session-options {
description
"NETCONF session options, independent of transport
or connection strategy.";
leaf hello-timeout {
type uint32 {
range "0 | 10 .. 3600";
}
units "seconds";
default '600';
description
"Specifies the number of seconds that a session
may exist before the hello PDU is received.
A session will be dropped if no hello PDU
is received before this number of seconds elapses.
If this parameter is set to zero, then the server
will wait forever for a hello message, and not
drop any sessions stuck in 'hello-wait' state.
Setting this parameter to zero may permit
denial of service attacks, since only a limited
number of concurrent sessions are supported
by the server.";
}
leaf idle-timeout {
type uint32 {
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range "0 | 10 .. 360000";
}
units "seconds";
default '3600';
description
"Specifies the number of seconds that a session
may remain idle without issuing any RPC requests.
A session will be dropped if it is idle for an
interval longer than this number of seconds.
Sessions that have a notification subscription
active are never dropped.
If this parameter is set to zero, then the server
will never drop a session because it is idle.";
}
}
}
grouping listen-container {
description
"";
container listen {
description
"Configures listen behavior";
//if-feature "(ssh-listen or tls-listen)";
leaf max-sessions {
type uint16 {
range "0 .. 1024";
}
default '0';
description
"Specifies the maximum number of concurrent sessions
that can be active at one time. The value 0 indicates
that no artificial session limit should be used.";
}
list endpoint {
key name;
description
"List of endpoints to listen for connections on.";
leaf name {
type string;
description
"An arbitrary name for the listen endpoint.";
}
choice transport {
mandatory true;
description
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"Selects between SSH and TLS transports.";
case ssh {
if-feature ssh-listen;
container ssh {
description
"SSH-specific listening configuration for inbound
connections.";
uses address-and-port-grouping {
refine port {
default 830;
}
}
uses host-keys-container;
}
}
case tls {
if-feature tls-listen;
container tls {
description
"TLS-specific listening configuration for inbound
connections.";
uses address-and-port-grouping {
refine port {
default 6513;
}
}
uses certificates-container;
}
}
}
uses keep-alives-container {
refine keep-alives/interval-secs {
default 0; // disabled by default for listen connections
}
}
}
}
}
grouping call-home-container {
description
"";
container call-home {
//if-feature "(ssh-call-home or tls-call-home)";
description
"Configures call-home behavior";
list application {
key name;
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description
"List of applications to call-home to.";
leaf name {
type string;
description
"An arbitrary name for the remote application.";
}
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 endpoints-container {
refine endpoints/endpoint/port {
default 8888; // pending IANA assignment
}
}
uses host-keys-container;
}
}
case tls {
if-feature tls-call-home;
container tls {
description
"Specifies TLS-specific call-home transport
configuration.";
uses endpoints-container {
refine endpoints/endpoint/port {
default 9999; // pending IANA assignment
}
}
uses certificates-container;
}
}
}
container connection-type {
description
"Indicates the NETCONF client's preference for how the
device's connection is maintained.";
choice connection-type {
default persistent-connection;
description
"Selects between persistent and periodic connections.";
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case persistent-connection {
container persistent {
description
"Maintain a persistent connection to the
NETCONF client. If the connection goes down,
immediately start trying to reconnect to it,
using the reconnection strategy.
This connection type minimizes any NETCONF
client to NETCONF server data-transfer delay,
albeit at the expense of holding resources
longer.";
uses keep-alives-container {
refine keep-alives/interval-secs {
default 15; // 15 seconds for call-home sessions
}
}
}
}
case periodic-connection {
container periodic {
description
"Periodically connect to NETCONF client, using the
reconnection strategy, so the NETCONF client can
deliver pending messages to the NETCONF server.
For messages the NETCONF server wants to send to
to the NETCONF client, the NETCONF server should
proactively connect to the NETCONF client, if
not already, to send the messages immediately.";
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 NETCONF client again. The
device MAY establish a connection before this
time if it has data it needs to send to the
NETCONF client. Note: this value differs from
the reconnection strategy's interval-secs
value.";
}
leaf linger-secs {
type uint8;
units seconds;
default 30;
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description
"The amount of time the device should wait after
last receiving data from or sending data to the
NETCONF client's endpoint before closing its
connection to it. This is an optimization to
prevent unnecessary connections.";
}
}
}
}
}
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. NETCONF servers
SHOULD support this flag across reboots.";
}
}
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
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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 ssh-container {
description
"";
container ssh {
description
"Configures SSH properties not specific to the listen
or call-home use-cases";
//if-feature "(ssh-listen or ssh-call-home)";
container host-keys {
config false;
description
"Parent container for a list of host keys";
list host-key {
key name;
description
"A read-only list of host-keys supported by server";
leaf name {
type string;
description
"Common name for the host-key";
}
leaf format-identifier {
type string;
mandatory true;
description
"ssh-dss, ssh-rsa, x509v3-rsa2048-sha256, etc.";
reference
"RFC 4253: SSH Transport Layer Protocol, section 6.6
RFC 6187: X.509v3 Certificates for SSH, section 3";
}
leaf data {
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type binary;
mandatory true;
description
"Key-specific binary encoding.";
reference
"RFC 4253: SSH Transport Layer Protocol, section 6.6";
}
leaf fingerprint {
type string;
mandatory true;
description
"c1:b1:30:29:d7:b8:de:6c:97:77:10:d7:46:41:63:87";
reference
"RFC 4716: The Secure Shell (SSH) Public Key File
Format, section 4";
}
}
}
}
}
grouping tls-container {
description
"";
container tls {
description
"Configures TLS properties not specific to the listen
or call-home use-cases";
//if-feature "(tls-listen or tls-call-home)";
container certificates {
config false;
description
"Parent container for a list of certificates";
list certificate {
key name;
description
"A list of certificates";
leaf name {
type string;
description
"the certificate's common name";
}
leaf data {
type binary;
mandatory true;
description
"The binary certificate structure, as specified
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by RFC 5246, Section 7.4.2, i.e.,: opaque
ASN.1Cert<1..2^24-1>;";
}
}
}
container client-auth {
description
"Container for TLS client authentication configuration.";
container trusted-ca-certs {
description
"A list of Certificate Authority (CA) certificates that
a NETCONF server can use to authenticate NETCONF client
certificates. A client's certificate is authenticated
if there is a chain of trust to a configured trusted CA
certificate. Note, in the TLS protocol, the client
certificate MAY be accompanied with additional
certificates forming a chain of trust. The client's
certificate is authenticated if there is path-validation
from any of the certificates it presents to a configured
trust anchor.";
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 a configured trusted client certificates.";
leaf-list trusted-client-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>;
";
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reference
"RFC 5246: The Transport Layer Security (TLS)
Protocol Version 1.2";
}
}
container cert-maps {
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.";
}
}
}
}
grouping host-keys-container {
description
"";
container host-keys {
description
"Parent container for the list of host-keys.";
leaf-list host-key {
type string;
min-elements 1;
ordered-by user;
description
"User-ordered list of host-keys the SSH server
considers when composing the list of server
host key algorithms it will send to the client.
The value of the string is the name of a
host-key configured on the system, as returned
by /netconf-server/ssh/host-keys/host-key/name.";
reference
"RFC 4253: The SSH Transport Layer Protocol, Section 7";
}
}
}
grouping certificates-container {
description
"";
container certificates {
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description
"Parent container for the list of certificates.";
leaf-list certificate {
type string;
min-elements 1;
description
"Unordered list of certificates the TLS server can
pick from when sending its Server Certificate
message. The value of the string is the name of a
certificate configured on the system, as returned by
/netconf-server/tls/certificates/certificate/name";
reference
"RFC 5246: The TLS Protocol, Section 7.4.2";
}
}
}
grouping address-and-port-grouping {
description
"a common grouping";
leaf address {
type inet:ip-address;
description
"The 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 endpoints-container {
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.";
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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 or hostname 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.";
}
}
}
}
grouping keep-alives-container {
description
"";
container keep-alives {
description
"Configures the keep-alive policy, to proactively
test the aliveness of the NETCONF client, in
order to know when a new call home connection
should be established. Keepalive implementation
is described in RFC XXXX, section 4.";
reference
"RFC XXXX: NETCONF Server Configuration Model
Section 4";
leaf interval-secs {
type uint8;
units seconds;
description
"Sets a timeout interval in seconds after which
if no data has been received from the NETCONF
client, a message will be sent to request a
response from the NETCONF client. A value of
'0' indicates that no keep-alive messages
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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 NETCONF client before assuming the NETCONF
client is no longer alive. If this threshold
is reached, the transport-level connection
will be disconnected, which will trigger the
reconnection strategy). The interval timer is
reset after each transmission, thus an
unresponsive NETCONF client will be dropped
after ~count-max * interval-secs seconds.";
}
}
}
}
<CODE ENDS>
4. Implementation strategy for keep-alives
One of the objectives listed above, Keep-alives for persistent
connections (Section 2.6.6), indicates a need for a "keep-alive"
mechanism. This section specifies how the NETCONF keep-alive
mechanism is to be implemented for both the SSH and TLS transports.
Both SSH and TLS have the ability to support keep-alives securely.
Using the strategies listed below, the keep-alive messages are sent
inside the encrypted transport sessions.
4.1. Keep-alives for SSH
The SSH keep-alive solution that is expected to be used 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.
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To ensure that the request will fail, current implementations of this
keep-alive strategy (e.g. OpenSSH's `sshd` server) 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, implementations are free to
pick values of their choosing.
4.2. Keep-alives for TLS
The TLS keep-alive solution that is expected to be used 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 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 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"
YANG module which are readable and/or writable that 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.
netconf-server/tls/client-auth/trusted-ca-certs:
o This container contains certificates that the system is to use as
trust anchors for authenticating TLS-specific client certificates.
Write access to this node should be protected.
netconf-server/tls/client-auth/trusted-client-certs:
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o This container contains certificates that the system is to trust
directly when authenticating TLS-specific client certificates.
Write access to this node should be protected.
netconf-server/tls/client-auth/cert-map:
o This container contains a user name that some deployments may
consider sensitive information. Read access to this node may need
to be guarded.
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
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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.
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.
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[draft-ietf-netmod-snmp-cfg]
Bjorklund, M. and J. Schoenwaelder, "A YANG Data Model for
SNMP Configuration", draft-ietf-netmod-snmp-cfg-08 (work
in progress), September 2014.
[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 + State
The following example illustrastes the <get> response from a NETCONF
server that only supports SSH, both listening for incoming
connections as well as calling home to a single application having
two endpoints. Please also note that the list of host-keys at the
end is read-only operational state.
<netconf-server xmlns="urn:ietf:params:xml:ns:yang:ietf-netconf-server">
<listen>
<endpoint>
<name>foo bar</name>
<ssh>
<address>11.22.33.44</address>
<host-keys>
<host-key>my-rsa-key</host-key>
<host-key>my-dss-key</host-key>
</host-keys>
</ssh>
</endpoint>
</listen>
<call-home>
<application>
<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>
<host-keys>
<host-key>my-call-home-x509-key</host-key>
</host-keys>
</ssh>
</application>
</call-home>
<ssh>
<host-keys>
<host-key>
<name>my-rsa-key</name>
<format-identifier>ssh-rsa</format-identifier>
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<data> <!-- base64 reformated for draft -->
AAAAB3NzaC1yc2EAAAABIwAAAQEA7D2lxYg3+WD97RZqZtO8bUU8QpIl6g9
X11kZHZ8NgSIR+x2H1MHCD5sEjmx/B6JIouK5eBvbJE9FFV3phsl62fupN6
Y4EmXosC6iqpuI41dcGA63XCQ1OenWG4ppdq1f8tlecSrmEcLw7MKPzBHK6
rNQTciqMuVuLPOKwBu/54QAiUwvvHKAsk8bkN9YxEJ1NTV1FFQmvMOADVcD
2qqPangETwV5zInW8AEkBbLccM/mmHucGNS81axXR3V9R5KgXF2DyGB47d2
k6iOnGa3LBIOYi/5Q+O8IFUlO+kytfqwuFgUc+Mx7aKReSIAPov3owVjeBL
KWsvjD24UO68qtwQ==
</data>
<fingerprint>
c1:b1:30:29:d7:b8:de:6c:97:77:10:d7:46:41:63:87
</fingerprint>
</host-key>
<host-key>
<name>my-dss-key</name>
<format-identifier>ssh-dss</format-identifier>
<data> <!-- base64 reformated for draft -->
AAAAB3NzaC1kc3MAAACBAIq7XfGmZKJgibJEIMzj70YMVfpeewBCj89VrUS
gLsJmxP/TrXFuhzW2UIaI8sePMYUXj/Vgp5DUD+eBSBkHMH4ga0U5t/clqn
y73x8Vg6LQg9f0OTaUnpRWbWrdac7U5/BRBTtMA3amHZhHrKs7BrCepS/y8
cUbxBCPF3aYMK/5AAAAFQC7wetEbDwghYtz8Z3xIwDdxs6mOwAAAIBursEk
jnvs5zzyUH7iNiyBojDoyrsq81jPM6KopkfA5Ypp2KTySPev/mkL0SoVfIb
+HttVfQ3Q63+sf1Qyk+gUtniSdN2AqtFQYKxtTcXim4McWk6IixkYFP8kkt
02t9Hsl0eXvltmogrlRsiuJsTAbFS+QTeq4OGTODCT5jjVdQAAAIA2llpZg
y5v46lGt4dQhkH8ytyMGyjBRPF6rm51msinX3lMR9xfwTaS7ZYP0b6HJt5M
sQI+m7iIYaVFB1oC8niXbkkavLcxhGpNVkwE2INWS4TIBbTQhivuoE+dMYY
KauLQxqSUjixJk3LjhCQb
</data>
<fingerprint>
c1:b1:30:29:d7:b8:de:6c:97:77:10:d7:46:41:63:87
</fingerprint>
</host-key>
<host-key>
<name>my-call-home-x509-key</name>
<format-identifier>x509v3-rsa2048-sha256</format-identifier>
<data> <!-- base64 reformated for draft -->
AAAAB3NzaC1yc2EAAAABIwAAAQEAyBLl90dPUGX7Es12q7YKkw6v8WgWop+
B62zhT39C+yvslMIwIqgHYii0h/TGktahKpBwssawfhvAZoMF/nOyO3yDPD
pQxNrA76H7owNOjG5206QHDYfVALKPvxgrDy/6BjsR9MayOGkZTSL6GRFSl
g7ivT9AIR9E5qXmP+1z+IDufRlpwfaGfpZAxjJLEwzAjFAIwXsXKJ5FH/QP
mfC6gxfhqpt9rJCDlgqmzrXi8dXKsFUC3/o1lzezqTXTV1iMETTuCHgWegF
5QcX2baBdFgCnkd1SnftVoBHVnvXA1euRqgiG3fMNK4rct0D99D+GI+kZc+
vQyUdCw3dPlhXPZw==
</data>
<fingerprint>
97:77:10:29:d7:b8:de:6c:97:77:30:29:d7:41:63:87
</fingerprint>
</host-key>
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</host-keys>
</ssh>
</netconf-server>
A.2. TLS Transport Configuration + State
The following example illustrastes the <get> response from a NETCONF
server that only supports TLS, both listening for incoming
connections as well as calling home to a single application having
two endpoints. Please note also the configurations for
authenticating client certificates and mappings authenticated
certificates to NETCONF user names.
<netconf-server xmlns="urn:ietf:params:xml:ns:yang:ietf-netconf-server">
<listen>
<endpoint>
<name>primary-netconf-endpoint</name>
<tls>
<address>11.22.33.44</address>
<certificates>
<certificate>fw1.east.example.com</certificate>
</certificates>
</tls>
</endpoint>
</listen>
<call-home>
<application>
<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>
</endpoint>
</endpoints>
<certificates>
<certificate>fw1.east.example.com</certificate>
</certificates>
</tls>
</application>
</call-home>
<tls>
<certificates>
<certificate>
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<name>fw1.east.example.com</name>
<data> <!-- base64 reformated for draft -->
AAAAB3NzaC1yc2EAAAABIwAAAQEA7D2lxYg3+WD97RZqZtO8bUU8QpIl6g9
X11kZHZ8NgSIR+x2H1MHCD5sEjmx/B6JIouK5eBvbJE9FFV3phsl62fupN6
Y4EmXosC6iqpuI41dcGA63XCQ1OenWG4ppdq1f8tlecSrmEcLw7MKPzBHK6
rNQTciqMuVuLPOKwBu/54QAiUwvvHKAsk8bkN9YxEJ1NTV1FFQmvMOADVcD
2qqPangETwV5zInW8AEkBbLccM/mmHucGNS81axXR3V9R5KgXF2DyGB47d2
k6iOnGa3LBIOYi/5Q+O8IFUlO+kytfqwuFgUc+Mx7aKReSIAPov3owVjeBL
KWsvjD24UO68qtwQ==
</data>
</certificate>
</certificates>
<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>
</client-auth>
</tls>
</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
B.4. 03 to 04
o reduced the number of grouping statements
o removed psk-maps and associated feature statements
o added ability for listen/call-home instances to specify which
host-keys/certificates (of all listed) to use
o clarified that last-connected should span reboots
o added missing "objectives" for selecting which keys to use,
authenticating client-certificates, and mapping authenticated
client-certificates to usernames
o clarified indirect client certificate authentication
o added keep-alive configuration for listen connections
o added global-level NETCONF session parameters
Watsen & Schoenwaelder Expires April 29, 2015 [Page 33]
Internet-Draft NETCONF Server Configuration Model October 2014
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
Watsen & Schoenwaelder Expires April 29, 2015 [Page 34]
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