A YANG Data Model for System Management
RFC 7317
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RFC - Proposed Standard
(August 2014; Errata)
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Authors |
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Andy Bierman
,
Martin Björklund
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Last updated |
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2020-07-30
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draft-bierman-netmod-system-mgmt
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Internet Engineering Task Force (IETF)
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Internet Engineering Task Force (IETF) A. Bierman
Request for Comments: 7317 YumaWorks
Category: Standards Track M. Bjorklund
ISSN: 2070-1721 Tail-f Systems
August 2014
A YANG Data Model for System Management
Abstract
This document defines a YANG data model for the configuration and
identification of some common system properties within a device
containing a Network Configuration Protocol (NETCONF) server. This
document also includes data node definitions for system
identification, time-of-day management, user management, DNS resolver
configuration, and some protocol operations for system management.
Status of This Memo
This is an Internet Standards Track document.
This document is a product of the Internet Engineering Task Force
(IETF). It represents the consensus of the IETF community. It has
received public review and has been approved for publication by the
Internet Engineering Steering Group (IESG). Further information on
Internet Standards is available in Section 2 of RFC 5741.
Information about the current status of this document, any errata,
and how to provide feedback on it may be obtained at
http://www.rfc-editor.org/info/rfc7317.
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.
Bierman & Bjorklund Standards Track [Page 1]
RFC 7317 YANG System Management August 2014
Table of Contents
1. Introduction ....................................................2
1.1. Terminology ................................................3
1.2. Tree Diagrams ..............................................3
2. Objectives ......................................................4
2.1. System Identification ......................................4
2.2. System Time Management .....................................4
2.3. User Authentication ........................................4
2.4. DNS Resolver ...............................................5
2.5. System Control .............................................5
3. System Data Model ...............................................5
3.1. System Identification ......................................5
3.2. System Time Management .....................................6
3.3. DNS Resolver Model .........................................7
3.4. RADIUS Client Model ........................................7
3.5. User Authentication Model ..................................8
3.5.1. SSH Public Key Authentication .......................8
3.5.2. Local User Password Authentication ..................9
3.5.3. RADIUS Password Authentication ......................9
3.6. System Control .............................................9
4. Relationship to the SNMPv2-MIB .................................10
5. IANA Crypt Hash YANG Module ....................................10
6. System YANG Module .............................................13
7. IANA Considerations ............................................31
8. Security Considerations ........................................31
9. References .....................................................33
9.1. Normative References ......................................33
9.2. Informative References ....................................35
1. Introduction
This document defines a YANG [RFC6020] data model for the
configuration and identification of some common properties within a
device containing a Network Configuration Protocol (NETCONF) server.
Devices that are managed by NETCONF and perhaps other mechanisms have
common properties that need to be configured and monitored in a
standard way.
The "ietf-system" YANG module defined in this document provides the
following features:
o configuration and monitoring of system identification
o configuration and monitoring of system time-of-day
o configuration of user authentication
Bierman & Bjorklund Standards Track [Page 2]
RFC 7317 YANG System Management August 2014
o configuration of local users
o configuration of the DNS resolver
o system control operations (shutdown, restart, setting time)
1.1. Terminology
The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT",
"SHOULD", "SHOULD NOT", "RECOMMENDED", "NOT RECOMMENDED", "MAY", and
"OPTIONAL" in this document are to be interpreted as described in
BCP 14, [RFC2119].
The following terms are defined in [RFC6241] and are not redefined
here:
o client
o configuration data
o server
o state data
The following terms are defined in [RFC6020] and are not redefined
here:
o augment
o data model
1.2. Tree Diagrams
A simplified graphical representation of the data model 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" means 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.
Bierman & Bjorklund Standards Track [Page 3]
RFC 7317 YANG System Management August 2014
o Parentheses enclose choice and case nodes, and case nodes are also
marked with a colon (":").
o Ellipsis ("...") stands for contents of subtrees that are not
shown.
2. Objectives
2.1. System Identification
There are many common properties used to identify devices, operating
systems, software versions, etc. that need to be supported in the
system data module. These objects are defined as operational state
data, and the information returned by the server is intended to be
specific to the device vendor.
Some user-configurable administrative strings are also provided, such
as the system location and description.
2.2. System Time Management
Management of the date and time used by the system needs to be
supported. The use of one or more NTP servers to automatically set
the system date and time needs to be possible. Utilization of the
Time Zone Database [RFC6557] also needs to be supported. It should
be possible to configure the system to use NTP.
2.3. User Authentication
The authentication mechanism needs to support password authentication
over RADIUS in order to support deployment scenarios with centralized
authentication servers. Additionally, for scenarios when no
centralized authentication server exists or for situations where the
centralized authentication server cannot be reached from the device,
local users need to be supported.
Since the mandatory transport protocol for NETCONF is Secure Shell
(SSH) [RFC6242], the authentication model needs to support SSH's
"publickey" and "password" authentication methods [RFC4252].
The model for authentication configuration should be flexible enough
to support authentication methods defined by other standards
documents or by vendors. It should be possible to configure the
system authentication properties.
Bierman & Bjorklund Standards Track [Page 4]
RFC 7317 YANG System Management August 2014
2.4. DNS Resolver
The configuration of the DNS resolver within the system containing
the NETCONF server is required in order to control how domain names
are resolved.
2.5. System Control
A few operations are needed to support common tasks such as
restarting the device or setting the system date and time.
3. System Data Model
3.1. System Identification
The data model for system identification has the following structure:
+--rw system
| +--rw contact? string
| +--rw hostname? inet:domain-name
| +--rw location? string
+--ro system-state
+--ro platform
+--ro os-name? string
+--ro os-release? string
+--ro os-version? string
+--ro machine? string
Bierman & Bjorklund Standards Track [Page 5]
RFC 7317 YANG System Management August 2014
3.2. System Time Management
The data model for system time management has the following
structure:
+--rw system
| +--rw clock
| | +--rw (timezone)?
| | +--:(timezone-name)
| | | +--rw timezone-name? timezone-name
| | +--:(timezone-utc-offset)
| | +--rw timezone-utc-offset? int16
| +--rw ntp!
| +--rw enabled? boolean
| +--rw server* [name]
| +--rw name string
| +--rw (transport)
| | +--:(udp)
| | +--rw udp
| | +--rw address inet:host
| | +--rw port? inet:port-number
| +--rw association-type? enumeration
| +--rw iburst? boolean
| +--rw prefer? boolean
+--ro system-state
+--ro clock
+--ro current-datetime? yang:date-and-time
+--ro boot-datetime? yang:date-and-time
New "case" statements can be added in future revisions of this data
model, or through augmentation by some other data model.
Bierman & Bjorklund Standards Track [Page 6]
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3.3. DNS Resolver Model
The data model for configuration of the DNS resolver has the
following structure:
+--rw system
+--rw dns-resolver
+--rw search* inet:domain-name
+--rw server* [name]
| +--rw name string
| +--rw (transport)
| +--:(udp-and-tcp)
| +--udp-and-tcp
| +--rw address inet:ip-address
| +--rw port? inet:port-number
+--rw options
+--rw timeout? uint8
+--rw attempts? uint8
New "case" statements can be added in future revisions of this data
model, or through augmentation by some other data model.
3.4. RADIUS Client Model
The data model for configuration of the RADIUS client has the
following structure:
+--rw system
+--rw radius
+--rw server* [name]
| +--rw name string
| +--rw (transport)
| | +--:(udp)
| | +--rw udp
| | +--rw address inet:host
| | +--rw authentication-port? inet:port-number
| | +--rw shared-secret string
| +--rw authentication-type? identityref
+--rw options
+--rw timeout? uint8
+--rw attempts? uint8
New "case" statements can be added in future revisions of this data
model, or through augmentation by some other data model.
Bierman & Bjorklund Standards Track [Page 7]
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3.5. User Authentication Model
This document defines three authentication methods for use with
NETCONF:
o publickey for local users over SSH
o password for local users over any secure transport
o password for RADIUS users over any secure transport
Additional methods can be defined by other standards documents or by
vendors.
This document defines two optional YANG features: "local-users" and
"radius-authentication", which the server advertises to indicate
support for configuring local users on the device and support for
using RADIUS for authentication, respectively.
The authentication parameters defined in this document are primarily
used to configure authentication of NETCONF users but MAY also be
used by other interfaces, e.g., a command line interface or a web-
based user interface.
The data model for user authentication has the following structure:
+--rw system
+--rw authentication
+--rw user-authentication-order* identityref
+--rw user* [name]
+--rw name string
+--rw password? ianach:crypt-hash
+--rw authorized-key* [name]
+--rw name string
+--rw algorithm string
+--rw key-data binary
3.5.1. SSH Public Key Authentication
If the NETCONF server advertises the "local-users" feature,
configuration of local users and their SSH public keys is supported
in the /system/authentication/user list.
Public key authentication is requested by the SSH client. If the
"local-users" feature is supported, then when a NETCONF client starts
an SSH session towards the server using the "publickey"
authentication "method name" [RFC4252], the SSH server looks up the
Bierman & Bjorklund Standards Track [Page 8]
RFC 7317 YANG System Management August 2014
user name given in the SSH authentication request in the
/system/authentication/user list and verifies the key as described in
[RFC4253].
3.5.2. Local User Password Authentication
If the NETCONF server advertises the "local-users" feature,
configuration of local users and their passwords is supported in the
/system/authentication/user list.
For NETCONF transport protocols that support password authentication,
the leaf-list "user-authentication-order" is used to control whether
or not local user password authentication should be used.
In SSH, password authentication is requested by the client. Other
NETCONF transport protocols MAY also support password authentication.
When local user password authentication is requested, the NETCONF
transport looks up the user name provided by the client in the
/system/authentication/user list and verifies the password.
3.5.3. RADIUS Password Authentication
If the NETCONF server advertises the "radius-authentication" feature,
the device supports user authentication using RADIUS.
For NETCONF transport protocols that support password authentication,
the leaf-list "user-authentication-order" is used to control whether
or not RADIUS password authentication should be used.
In SSH, password authentication is requested by the client. Other
NETCONF transport protocols MAY also support password authentication.
3.6. System Control
The following operations are defined:
set-current-datetime
system-restart
system-shutdown
Two protocol operations are included to restart or shut down the
system. The 'system-restart' operation can be used to restart the
entire system (not just the NETCONF server). The 'system-shutdown'
operation can be used to power off the entire system.
Bierman & Bjorklund Standards Track [Page 9]
RFC 7317 YANG System Management August 2014
4. Relationship to the SNMPv2-MIB
If a device implements the SNMPv2-MIB [RFC3418], there are two
objects that MAY be mapped by the implementation. See the YANG
module definition in Section 6 for details. The following table
lists the YANG data nodes with corresponding objects in the
SNMPv2-MIB.
+----------------+-------------------+
| YANG data node | SNMPv2-MIB object |
+----------------+-------------------+
| contact | sysContact |
| location | sysLocation |
+----------------+-------------------+
YANG Interface Configuration Data Nodes and
Related SNMPv2-MIB Objects
5. IANA Crypt Hash YANG Module
This YANG module references [RFC1321], [IEEE-1003.1-2008], and
[FIPS.180-4.2012].
<CODE BEGINS> file "iana-crypt-hash@2014-08-06.yang"
module iana-crypt-hash {
namespace "urn:ietf:params:xml:ns:yang:iana-crypt-hash";
prefix ianach;
organization "IANA";
contact
" Internet Assigned Numbers Authority
Postal: ICANN
12025 Waterfront Drive, Suite 300
Los Angeles, CA 90094-2536
United States
Tel: +1 310 301 5800
E-Mail: iana@iana.org>";
description
"This YANG module defines a type for storing passwords
using a hash function and features to indicate which hash
functions are supported by an implementation.
The latest revision of this YANG module can be obtained from
the IANA web site.
Bierman & Bjorklund Standards Track [Page 10]
RFC 7317 YANG System Management August 2014
Requests for new values should be made to IANA via
email (iana@iana.org).
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).
The initial version of this YANG module is part of RFC 7317;
see the RFC itself for full legal notices.";
revision 2014-08-06 {
description
"Initial revision.";
reference
"RFC 7317: A YANG Data Model for System Management";
}
typedef crypt-hash {
type string {
pattern
'$0$.*'
+ '|$1$[a-zA-Z0-9./]{1,8}$[a-zA-Z0-9./]{22}'
+ '|$5$(rounds=\d+$)?[a-zA-Z0-9./]{1,16}$[a-zA-Z0-9./]{43}'
+ '|$6$(rounds=\d+$)?[a-zA-Z0-9./]{1,16}$[a-zA-Z0-9./]{86}';
}
description
"The crypt-hash type is used to store passwords using
a hash function. The algorithms for applying the hash
function and encoding the result are implemented in
various UNIX systems as the function crypt(3).
A value of this type matches one of the forms:
$0$<clear text password>
$<id>$<salt>$<password hash>
$<id>$<parameter>$<salt>$<password hash>
The '$0$' prefix signals that the value is clear text. When
such a value is received by the server, a hash value is
calculated, and the string '$<id>$<salt>$' or
$<id>$<parameter>$<salt>$ is prepended to the result. This
value is stored in the configuration data store.
Bierman & Bjorklund Standards Track [Page 11]
RFC 7317 YANG System Management August 2014
If a value starting with '$<id>$', where <id> is not '0', is
received, the server knows that the value already represents a
hashed value and stores it 'as is' in the data store.
When a server needs to verify a password given by a user, it
finds the stored password hash string for that user, extracts
the salt, and calculates the hash with the salt and given
password as input. If the calculated hash value is the same
as the stored value, the password given by the client is
accepted.
This type defines the following hash functions:
id | hash function | feature
---+---------------+-------------------
1 | MD5 | crypt-hash-md5
5 | SHA-256 | crypt-hash-sha-256
6 | SHA-512 | crypt-hash-sha-512
The server indicates support for the different hash functions
by advertising the corresponding feature.";
reference
"IEEE Std 1003.1-2008 - crypt() function
RFC 1321: The MD5 Message-Digest Algorithm
FIPS.180-4.2012: Secure Hash Standard (SHS)";
}
feature crypt-hash-md5 {
description
"Indicates that the device supports the MD5
hash function in 'crypt-hash' values.";
reference "RFC 1321: The MD5 Message-Digest Algorithm";
}
feature crypt-hash-sha-256 {
description
"Indicates that the device supports the SHA-256
hash function in 'crypt-hash' values.";
reference "FIPS.180-4.2012: Secure Hash Standard (SHS)";
}
Bierman & Bjorklund Standards Track [Page 12]
RFC 7317 YANG System Management August 2014
feature crypt-hash-sha-512 {
description
"Indicates that the device supports the SHA-512
hash function in 'crypt-hash' values.";
reference "FIPS.180-4.2012: Secure Hash Standard (SHS)";
}
}
<CODE ENDS>
6. System YANG Module
This YANG module imports YANG extensions from [RFC6536] and imports
YANG types from [RFC6991]. It also references [RFC1035], [RFC2865],
[RFC3418], [RFC5607], [RFC5966], and [RFC6557].
<CODE BEGINS> file "ietf-system@2014-08-06.yang"
module ietf-system {
namespace "urn:ietf:params:xml:ns:yang:ietf-system";
prefix "sys";
import ietf-yang-types {
prefix yang;
}
import ietf-inet-types {
prefix inet;
}
import ietf-netconf-acm {
prefix nacm;
}
import iana-crypt-hash {
prefix ianach;
}
organization
"IETF NETMOD (NETCONF Data Modeling Language) Working Group";
Bierman & Bjorklund Standards Track [Page 13]
RFC 7317 YANG System Management August 2014
contact
"WG Web: <http://tools.ietf.org/wg/netmod/>
WG List: <mailto:netmod@ietf.org>
WG Chair: Thomas Nadeau
<mailto:tnadeau@lucidvision.com>
WG Chair: Juergen Schoenwaelder
<mailto:j.schoenwaelder@jacobs-university.de>
Editor: Andy Bierman
<mailto:andy@yumaworks.com>
Editor: Martin Bjorklund
<mailto:mbj@tail-f.com>";
description
"This module contains a collection of YANG definitions for the
configuration and identification of some common system
properties within a device containing a NETCONF server. This
includes data node definitions for system identification,
time-of-day management, user management, DNS resolver
configuration, and some protocol operations for system
management.
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 7317; see
the RFC itself for full legal notices.";
revision 2014-08-06 {
description
"Initial revision.";
reference
"RFC 7317: A YANG Data Model for System Management";
}
Bierman & Bjorklund Standards Track [Page 14]
RFC 7317 YANG System Management August 2014
/*
* Typedefs
*/
typedef timezone-name {
type string;
description
"A time zone name as used by the Time Zone Database,
sometimes referred to as the 'Olson Database'.
The exact set of valid values is an implementation-specific
matter. Client discovery of the exact set of time zone names
for a particular server is out of scope.";
reference
"RFC 6557: Procedures for Maintaining the Time Zone Database";
}
/*
* Features
*/
feature radius {
description
"Indicates that the device can be configured as a RADIUS
client.";
reference
"RFC 2865: Remote Authentication Dial In User Service (RADIUS)";
}
feature authentication {
description
"Indicates that the device supports configuration of
user authentication.";
}
feature local-users {
if-feature authentication;
description
"Indicates that the device supports configuration of
local user authentication.";
}
Bierman & Bjorklund Standards Track [Page 15]
RFC 7317 YANG System Management August 2014
feature radius-authentication {
if-feature radius;
if-feature authentication;
description
"Indicates that the device supports configuration of user
authentication over RADIUS.";
reference
"RFC 2865: Remote Authentication Dial In User Service (RADIUS)
RFC 5607: Remote Authentication Dial-In User Service (RADIUS)
Authorization for Network Access Server (NAS)
Management";
}
feature ntp {
description
"Indicates that the device can be configured to use one or
more NTP servers to set the system date and time.";
}
feature ntp-udp-port {
if-feature ntp;
description
"Indicates that the device supports the configuration of
the UDP port for NTP servers.
This is a 'feature', since many implementations do not support
any port other than the default port.";
}
feature timezone-name {
description
"Indicates that the local time zone on the device
can be configured to use the TZ database
to set the time zone and manage daylight saving time.";
reference
"RFC 6557: Procedures for Maintaining the Time Zone Database";
}
feature dns-udp-tcp-port {
description
"Indicates that the device supports the configuration of
the UDP and TCP port for DNS servers.
This is a 'feature', since many implementations do not support
any port other than the default port.";
}
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/*
* Identities
*/
identity authentication-method {
description
"Base identity for user authentication methods.";
}
identity radius {
base authentication-method;
description
"Indicates user authentication using RADIUS.";
reference
"RFC 2865: Remote Authentication Dial In User Service (RADIUS)
RFC 5607: Remote Authentication Dial-In User Service (RADIUS)
Authorization for Network Access Server (NAS)
Management";
}
identity local-users {
base authentication-method;
description
"Indicates password-based authentication of locally
configured users.";
}
identity radius-authentication-type {
description
"Base identity for RADIUS authentication types.";
}
identity radius-pap {
base radius-authentication-type;
description
"The device requests Password Authentication Protocol (PAP)
authentication from the RADIUS server.";
reference
"RFC 2865: Remote Authentication Dial In User Service (RADIUS)";
}
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identity radius-chap {
base radius-authentication-type;
description
"The device requests Challenge Handshake Authentication
Protocol (CHAP) authentication from the RADIUS server.";
reference
"RFC 2865: Remote Authentication Dial In User Service (RADIUS)";
}
/*
* Configuration data nodes
*/
container system {
description
"System group configuration.";
leaf contact {
type string;
description
"The administrator contact information for the system.
A server implementation MAY map this leaf to the sysContact
MIB object. Such an implementation needs to use some
mechanism to handle the differences in size and characters
allowed between this leaf and sysContact. The definition of
such a mechanism is outside the scope of this document.";
reference
"RFC 3418: Management Information Base (MIB) for the
Simple Network Management Protocol (SNMP)
SNMPv2-MIB.sysContact";
}
leaf hostname {
type inet:domain-name;
description
"The name of the host. This name can be a single domain
label or the fully qualified domain name of the host.";
}
leaf location {
type string;
description
"The system location.
A server implementation MAY map this leaf to the sysLocation
MIB object. Such an implementation needs to use some
mechanism to handle the differences in size and characters
allowed between this leaf and sysLocation. The definition
of such a mechanism is outside the scope of this document.";
Bierman & Bjorklund Standards Track [Page 18]
RFC 7317 YANG System Management August 2014
reference
"RFC 3418: Management Information Base (MIB) for the
Simple Network Management Protocol (SNMP)
SNMPv2-MIB.sysLocation";
}
container clock {
description
"Configuration of the system date and time properties.";
choice timezone {
description
"The system time zone information.";
case timezone-name {
if-feature timezone-name;
leaf timezone-name {
type timezone-name;
description
"The TZ database name to use for the system, such
as 'Europe/Stockholm'.";
}
}
case timezone-utc-offset {
leaf timezone-utc-offset {
type int16 {
range "-1500 .. 1500";
}
units "minutes";
description
"The number of minutes to add to UTC time to
identify the time zone for this system. For example,
'UTC - 8:00 hours' would be represented as '-480'.
Note that automatic daylight saving time adjustment
is not provided if this object is used.";
}
}
}
}
container ntp {
if-feature ntp;
presence
"Enables the NTP client unless the 'enabled' leaf
(which defaults to 'true') is set to 'false'";
description
"Configuration of the NTP client.";
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leaf enabled {
type boolean;
default true;
description
"Indicates that the system should attempt to
synchronize the system clock with an NTP server
from the 'ntp/server' list.";
}
list server {
key name;
description
"List of NTP servers to use for system clock
synchronization. If '/system/ntp/enabled'
is 'true', then the system will attempt to
contact and utilize the specified NTP servers.";
leaf name {
type string;
description
"An arbitrary name for the NTP server.";
}
choice transport {
mandatory true;
description
"The transport-protocol-specific parameters for this
server.";
case udp {
container udp {
description
"Contains UDP-specific configuration parameters
for NTP.";
leaf address {
type inet:host;
mandatory true;
description
"The address of the NTP server.";
}
leaf port {
if-feature ntp-udp-port;
type inet:port-number;
default 123;
description
"The port number of the NTP server.";
}
}
}
}
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leaf association-type {
type enumeration {
enum server {
description
"Use client association mode. This device
will not provide synchronization to the
configured NTP server.";
}
enum peer {
description
"Use symmetric active association mode.
This device may provide synchronization
to the configured NTP server.";
}
enum pool {
description
"Use client association mode with one or
more of the NTP servers found by DNS
resolution of the domain name given by
the 'address' leaf. This device will not
provide synchronization to the servers.";
}
}
default server;
description
"The desired association type for this NTP server.";
}
leaf iburst {
type boolean;
default false;
description
"Indicates whether this server should enable burst
synchronization or not.";
}
leaf prefer {
type boolean;
default false;
description
"Indicates whether this server should be preferred
or not.";
}
}
}
container dns-resolver {
description
"Configuration of the DNS resolver.";
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leaf-list search {
type inet:domain-name;
ordered-by user;
description
"An ordered list of domains to search when resolving
a host name.";
}
list server {
key name;
ordered-by user;
description
"List of the DNS servers that the resolver should query.
When the resolver is invoked by a calling application, it
sends the query to the first name server in this list. If
no response has been received within 'timeout' seconds,
the resolver continues with the next server in the list.
If no response is received from any server, the resolver
continues with the first server again. When the resolver
has traversed the list 'attempts' times without receiving
any response, it gives up and returns an error to the
calling application.
Implementations MAY limit the number of entries in this
list.";
leaf name {
type string;
description
"An arbitrary name for the DNS server.";
}
choice transport {
mandatory true;
description
"The transport-protocol-specific parameters for this
server.";
case udp-and-tcp {
container udp-and-tcp {
description
"Contains UDP- and TCP-specific configuration
parameters for DNS.";
reference
"RFC 1035: Domain Names - Implementation and
Specification
RFC 5966: DNS Transport over TCP - Implementation
Requirements";
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leaf address {
type inet:ip-address;
mandatory true;
description
"The address of the DNS server.";
}
leaf port {
if-feature dns-udp-tcp-port;
type inet:port-number;
default 53;
description
"The UDP and TCP port number of the DNS server.";
}
}
}
}
}
container options {
description
"Resolver options. The set of available options has been
limited to those that are generally available across
different resolver implementations and generally useful.";
leaf timeout {
type uint8 {
range "1..max";
}
units "seconds";
default "5";
description
"The amount of time the resolver will wait for a
response from each remote name server before
retrying the query via a different name server.";
}
leaf attempts {
type uint8 {
range "1..max";
}
default "2";
description
"The number of times the resolver will send a query to
all of its name servers before giving up and returning
an error to the calling application.";
}
}
}
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container radius {
if-feature radius;
description
"Configuration of the RADIUS client.";
list server {
key name;
ordered-by user;
description
"List of RADIUS servers used by the device.
When the RADIUS client is invoked by a calling
application, it sends the query to the first server in
this list. If no response has been received within
'timeout' seconds, the client continues with the next
server in the list. If no response is received from any
server, the client continues with the first server again.
When the client has traversed the list 'attempts' times
without receiving any response, it gives up and returns an
error to the calling application.";
leaf name {
type string;
description
"An arbitrary name for the RADIUS server.";
}
choice transport {
mandatory true;
description
"The transport-protocol-specific parameters for this
server.";
case udp {
container udp {
description
"Contains UDP-specific configuration parameters
for RADIUS.";
leaf address {
type inet:host;
mandatory true;
description
"The address of the RADIUS server.";
}
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leaf authentication-port {
type inet:port-number;
default "1812";
description
"The port number of the RADIUS server.";
}
leaf shared-secret {
type string;
mandatory true;
nacm:default-deny-all;
description
"The shared secret, which is known to both the
RADIUS client and server.";
reference
"RFC 2865: Remote Authentication Dial In User
Service (RADIUS)";
}
}
}
}
leaf authentication-type {
type identityref {
base radius-authentication-type;
}
default radius-pap;
description
"The authentication type requested from the RADIUS
server.";
}
}
container options {
description
"RADIUS client options.";
leaf timeout {
type uint8 {
range "1..max";
}
units "seconds";
default "5";
description
"The number of seconds the device will wait for a
response from each RADIUS server before trying with a
different server.";
}
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leaf attempts {
type uint8 {
range "1..max";
}
default "2";
description
"The number of times the device will send a query to
all of its RADIUS servers before giving up.";
}
}
}
container authentication {
nacm:default-deny-write;
if-feature authentication;
description
"The authentication configuration subtree.";
leaf-list user-authentication-order {
type identityref {
base authentication-method;
}
must '(. != "sys:radius" or ../../radius/server)' {
error-message
"When 'radius' is used, a RADIUS server"
+ " must be configured.";
description
"When 'radius' is used as an authentication method,
a RADIUS server must be configured.";
}
ordered-by user;
description
"When the device authenticates a user with a password,
it tries the authentication methods in this leaf-list in
order. If authentication with one method fails, the next
method is used. If no method succeeds, the user is
denied access.
An empty user-authentication-order leaf-list still allows
authentication of users using mechanisms that do not
involve a password.
If the 'radius-authentication' feature is advertised by
the NETCONF server, the 'radius' identity can be added to
this list.
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If the 'local-users' feature is advertised by the
NETCONF server, the 'local-users' identity can be
added to this list.";
}
list user {
if-feature local-users;
key name;
description
"The list of local users configured on this device.";
leaf name {
type string;
description
"The user name string identifying this entry.";
}
leaf password {
type ianach:crypt-hash;
description
"The password for this entry.";
}
list authorized-key {
key name;
description
"A list of public SSH keys for this user. These keys
are allowed for SSH authentication, as described in
RFC 4253.";
reference
"RFC 4253: The Secure Shell (SSH) Transport Layer
Protocol";
leaf name {
type string;
description
"An arbitrary name for the SSH key.";
}
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leaf algorithm {
type string;
mandatory true;
description
"The public key algorithm name for this SSH key.
Valid values are the values in the IANA 'Secure Shell
(SSH) Protocol Parameters' registry, Public Key
Algorithm Names.";
reference
"IANA 'Secure Shell (SSH) Protocol Parameters'
registry, Public Key Algorithm Names";
}
leaf key-data {
type binary;
mandatory true;
description
"The binary public key data for this SSH key, as
specified by RFC 4253, Section 6.6, i.e.:
string certificate or public key format
identifier
byte[n] key/certificate data.";
reference
"RFC 4253: The Secure Shell (SSH) Transport Layer
Protocol";
}
}
}
}
}
/*
* Operational state data nodes
*/
container system-state {
config false;
description
"System group operational state.";
container platform {
description
"Contains vendor-specific information for
identifying the system platform and operating system.";
reference
"IEEE Std 1003.1-2008 - sys/utsname.h";
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leaf os-name {
type string;
description
"The name of the operating system in use -
for example, 'Linux'.";
reference
"IEEE Std 1003.1-2008 - utsname.sysname";
}
leaf os-release {
type string;
description
"The current release level of the operating
system in use. This string MAY indicate
the OS source code revision.";
reference
"IEEE Std 1003.1-2008 - utsname.release";
}
leaf os-version {
type string;
description
"The current version level of the operating
system in use. This string MAY indicate
the specific OS build date and target variant
information.";
reference
"IEEE Std 1003.1-2008 - utsname.version";
}
leaf machine {
type string;
description
"A vendor-specific identifier string representing
the hardware in use.";
reference
"IEEE Std 1003.1-2008 - utsname.machine";
}
}
container clock {
description
"Monitoring of the system date and time properties.";
leaf current-datetime {
type yang:date-and-time;
description
"The current system date and time.";
}
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leaf boot-datetime {
type yang:date-and-time;
description
"The system date and time when the system last restarted.";
}
}
}
rpc set-current-datetime {
nacm:default-deny-all;
description
"Set the /system-state/clock/current-datetime leaf
to the specified value.
If the system is using NTP (i.e., /system/ntp/enabled
is set to 'true'), then this operation will fail with
error-tag 'operation-failed' and error-app-tag value of
'ntp-active'.";
input {
leaf current-datetime {
type yang:date-and-time;
mandatory true;
description
"The current system date and time.";
}
}
}
rpc system-restart {
nacm:default-deny-all;
description
"Request that the entire system be restarted immediately.
A server SHOULD send an rpc reply to the client before
restarting the system.";
}
rpc system-shutdown {
nacm:default-deny-all;
description
"Request that the entire system be shut down immediately.
A server SHOULD send an rpc reply to the client before
shutting down the system.";
}
}
<CODE ENDS>
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RFC 7317 YANG System Management August 2014
7. IANA Considerations
IANA has created an IANA-maintained YANG module called
"iana-crypt-hash", based on the contents of Section 5, which will
allow for new hash algorithms to be added to the type "crypt-hash".
The registration procedure will be Expert Review, as defined by
[RFC5226].
This document registers two URIs in the "IETF XML Registry"
[RFC3688]. Following the format in RFC 3688, the following
registrations have been made.
URI: urn:ietf:params:xml:ns:yang:iana-crypt-hash
Registrant Contact: The IESG.
XML: N/A; the requested URI is an XML namespace.
URI: urn:ietf:params:xml:ns:yang:ietf-system
Registrant Contact: The IESG.
XML: N/A; the requested URI is an XML namespace.
This document registers two YANG modules in the "YANG Module Names"
registry [RFC6020].
name: iana-crypt-hash
namespace: urn:ietf:params:xml:ns:yang:iana-crypt-hash
prefix: ianach
reference: RFC 7317
name: ietf-system
namespace: urn:ietf:params:xml:ns:yang:ietf-system
prefix: sys
reference: RFC 7317
8. Security Considerations
The YANG modules defined in this memo are designed to be accessed via
the NETCONF protocol [RFC6241]. The lowest NETCONF layer is the
secure transport layer and the mandatory to implement secure
transport is SSH [RFC6242]. The NETCONF access control model
[RFC6536] provides the means to restrict access for particular
NETCONF users to a pre-configured subset of all available NETCONF
protocol operations and content.
There are a number of data nodes defined in the "ietf-system" YANG
module 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 operations (e.g.,
Bierman & Bjorklund Standards Track [Page 31]
RFC 7317 YANG System Management August 2014
edit-config) to these data nodes without proper protection can have a
negative effect on network operations. These are the subtrees and
data nodes and their sensitivity/vulnerability:
o /system/clock/timezone: This choice contains the objects used to
control the time zone used by the device.
o /system/ntp: This container contains the objects used to control
the Network Time Protocol servers used by the device.
o /system/dns-resolver: This container contains the objects used to
control the Domain Name System servers used by the device.
o /system/radius: This container contains the objects used to
control the Remote Authentication Dial-In User Service servers
used by the device.
o /system/authentication/user-authentication-order: This leaf
controls how user login attempts are authenticated by the device.
o /system/authentication/user: This list contains the local users
enabled on the system.
Some of the readable data nodes in the "ietf-system" YANG module may
be considered sensitive or vulnerable in some network environments.
It is thus important to control read access (e.g., via get,
get-config or notification) to these data nodes. These are the
subtrees and data nodes and their sensitivity/vulnerability:
o /system/platform: This container has objects that may help
identify the specific NETCONF server and/or operating system
implementation used on the device.
o /system/authentication/user: This list has objects that may help
identify the specific user names and password information in use
on the device.
Some of the RPC operations in the "ietf-system" YANG module may be
considered sensitive or vulnerable in some network environments. It
is thus important to control access to these operations. These are
the operations and their sensitivity/vulnerability:
o set-current-datetime: Changes the current date and time on the
device.
o system-restart: Reboots the device.
o system-shutdown: Shuts down the device.
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RFC 7317 YANG System Management August 2014
Since this document describes the use of RADIUS for purposes of
authentication, it is vulnerable to all of the threats that are
present in other RADIUS applications. For a discussion of such
threats, see [RFC2865] and [RFC3162], and Section 4 of [RFC3579].
This document provides configuration parameters for SSH's "publickey"
and "password" authentication mechanisms. Section 9.4 of [RFC4251]
and Section 11 of [RFC4252] discuss security considerations for these
mechanisms.
The "iana-crypt-hash" YANG module defines a type "crypt-hash" that
can be used to store MD5 hashes. [RFC6151] discusses security
considerations for MD5. The usage of MD5 is NOT RECOMMENDED.
9. References
9.1. Normative References
[FIPS.180-4.2012]
National Institute of Standards and Technology, "Secure
Hash Standard (SHS)", FIPS PUB 180-4, March 2012,
<http://csrc.nist.gov/publications/fips/fips180-4/
fips-180-4.pdf>.
[IEEE-1003.1-2008]
Institute of Electrical and Electronics Engineers,
"POSIX.1-2008", IEEE Standard 1003.1, March 2008.
[RFC1035] Mockapetris, P., "Domain names - implementation and
specification", STD 13, RFC 1035, November 1987.
[RFC1321] Rivest, R., "The MD5 Message-Digest Algorithm", RFC 1321,
April 1992.
[RFC2119] Bradner, S., "Key words for use in RFCs to Indicate
Requirement Levels", BCP 14, RFC 2119, March 1997.
[RFC2865] Rigney, C., Willens, S., Rubens, A., and W. Simpson,
"Remote Authentication Dial In User Service (RADIUS)",
RFC 2865, June 2000.
[RFC3162] Aboba, B., Zorn, G., and D. Mitton, "RADIUS and IPv6",
RFC 3162, August 2001.
[RFC3418] Presuhn, R., "Management Information Base (MIB) for the
Simple Network Management Protocol (SNMP)", STD 62,
RFC 3418, December 2002.
Bierman & Bjorklund Standards Track [Page 33]
RFC 7317 YANG System Management August 2014
[RFC4251] Ylonen, T. and C. Lonvick, "The Secure Shell (SSH)
Protocol Architecture", RFC 4251, January 2006.
[RFC4252] Ylonen, T. and C. Lonvick, "The Secure Shell (SSH)
Authentication Protocol", RFC 4252, January 2006.
[RFC4253] Ylonen, T. and C. Lonvick, "The Secure Shell (SSH)
Transport Layer Protocol", RFC 4253, January 2006.
[RFC5226] Narten, T. and H. Alvestrand, "Guidelines for Writing an
IANA Considerations Section in RFCs", BCP 26, RFC 5226,
May 2008.
[RFC5607] Nelson, D. and G. Weber, "Remote Authentication Dial-In
User Service (RADIUS) Authorization for Network Access
Server (NAS) Management", RFC 5607, July 2009.
[RFC5966] Bellis, R., "DNS Transport over TCP - Implementation
Requirements", RFC 5966, August 2010.
[RFC6020] Bjorklund, M., "YANG - A Data Modeling Language for the
Network Configuration Protocol (NETCONF)", RFC 6020,
October 2010.
[RFC6151] Turner, S. and L. Chen, "Updated Security Considerations
for the MD5 Message-Digest and the HMAC-MD5 Algorithms",
RFC 6151, March 2011.
[RFC6241] Enns, R., Ed., Bjorklund, M., Ed., Schoenwaelder, J., Ed.,
and A. Bierman, Ed., "Network Configuration Protocol
(NETCONF)", RFC 6241, June 2011.
[RFC6242] Wasserman, M., "Using the NETCONF Protocol over Secure
Shell (SSH)", RFC 6242, June 2011.
[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.
Bierman & Bjorklund Standards Track [Page 34]
RFC 7317 YANG System Management August 2014
9.2. Informative References
[RFC3579] Aboba, B. and P. Calhoun, "RADIUS (Remote Authentication
Dial In User Service) Support For Extensible
Authentication Protocol (EAP)", RFC 3579, September 2003.
[RFC3688] Mealling, M., "The IETF XML Registry", BCP 81, RFC 3688,
January 2004.
[RFC6557] Lear, E. and P. Eggert, "Procedures for Maintaining the
Time Zone Database", BCP 175, RFC 6557, February 2012.
Authors' Addresses
Andy Bierman
YumaWorks
EMail: andy@yumaworks.com
Martin Bjorklund
Tail-f Systems
EMail: mbj@tail-f.com
Bierman & Bjorklund Standards Track [Page 35]