Internet DRAFT - draft-zheng-opsawg-tacacs-yang
draft-zheng-opsawg-tacacs-yang
Network Working Group G. Zheng
Internet-Draft M. Wang
Intended status: Standards Track B. Wu
Expires: December 22, 2019 Huawei
June 20, 2019
Yang data model for TACACS+
draft-zheng-opsawg-tacacs-yang-02
Abstract
This document defines a YANG modules that augment the System data
model defined in the RFC 7317 with TACACS+ client model. The data
model of Terminal Access Controller Access Control System Plus
(TACACS+) client allows the configuration of TACACS+ servers for
centralized Authentication, Authorization and Accounting.
The YANG modules in this document conforms to the Network Management
Datastore Architecture (NMDA) defined in RFC 8342.
Status of This Memo
This Internet-Draft is submitted in full conformance with the
provisions of BCP 78 and BCP 79.
Internet-Drafts are working documents of the Internet Engineering
Task Force (IETF). Note that other groups may also distribute
working documents as Internet-Drafts. The list of current Internet-
Drafts is at https://datatracker.ietf.org/drafts/current/.
Internet-Drafts are draft documents valid for a maximum of six months
and may be updated, replaced, or obsoleted by other documents at any
time. It is inappropriate to use Internet-Drafts as reference
material or to cite them other than as "work in progress."
This Internet-Draft will expire on December 22, 2019.
Copyright Notice
Copyright (c) 2019 IETF Trust and the persons identified as the
document authors. All rights reserved.
This document is subject to BCP 78 and the IETF Trust's Legal
Provisions Relating to IETF Documents
(https://trustee.ietf.org/license-info) in effect on the date of
publication of this document. Please review these documents
carefully, as they describe your rights and restrictions with respect
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to this document. Code Components extracted from this document must
include Simplified BSD License text as described in Section 4.e of
the Trust Legal Provisions and are provided without warranty as
described in the Simplified BSD License.
Table of Contents
1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . 2
2. Conventions used in this document . . . . . . . . . . . . . . 3
2.1. Tree Diagrams . . . . . . . . . . . . . . . . . . . . . . 3
3. TACACS+ Client Model . . . . . . . . . . . . . . . . . . . . 3
4. TACACS+ Client Module . . . . . . . . . . . . . . . . . . . . 5
5. Security Considerations . . . . . . . . . . . . . . . . . . . 11
6. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 11
7. Acknowledgments . . . . . . . . . . . . . . . . . . . . . . . 12
8. References . . . . . . . . . . . . . . . . . . . . . . . . . 12
8.1. Normative References . . . . . . . . . . . . . . . . . . 12
8.2. Informative References . . . . . . . . . . . . . . . . . 13
Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . 13
1. Introduction
This document defines a YANG modules that augment the System data
model defined in the [RFC7317] with TACACS+ client model.
TACACS+ provides Device Administration for routers, network access
servers and other networked computing devices via one or more
centralized servers which is defined inthe TACACS+ Protocol.
[I-D.ietf-opsawg-tacacs]
The System Management Model [RFC7317] defines two YANG features to
support local or RADIUS authentication:
o User Authentication Model: Define a list of usernames and
passwords and control the order in which local or RADIUS
authentication is used.
o RADIUS Client Model: Defines a list of RADIUS server that a device
used.
Since TACACS+ is also used for device management and the feature is
not contained in the system model, this document defines a YANG data
model that allows users to configure TACACS+ client functions on a
device for centralized Authentication, Authorization and Accounting
provided by TACACS+ servers.
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The YANG models can be used with network management protocols such as
NETCONF[RFC6241] to install, manipulate, and delete the configuration
of network devices.
The YANG data model in this document conforms to the Network
Management Datastore Architecture (NMDA) defined in [RFC8342].
2. Conventions used in this document
The keywords "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
BCP14, [RFC2119], [RFC8174] when, and only when, they appear in all
capitals, as shown here.
The following terms are defined in [RFC6241] and are used in this
specification:
o client
o configuration data
o server
o state data
The following terms are defined in [RFC7950] and are used in this
specification:
o augment
o data model
o data node
The terminology for describing YANG data models is found in
[RFC7950].
2.1. Tree Diagrams
Tree diagrams used in this document follow the notation defined in
[RFC8340].
3. TACACS+ Client Model
This model is used to configure TACACS+ client on the device to
support deployment scenarios with centralized authentication,
authorization, and accounting servers. Authentication is used to
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validates a user's name and password, authorization allows the user
to access and execute commands at various command levels assigned to
the user and accounting keeps track of the activity of a user who has
accessed the device.
The ietf-system-tacacsplus module is intended to augment the
"/sys:system" path defined in the ietf-system module with
"tacacsplus" grouping. Therefore, a device can use local, Remote
Authentication Dial In User Service (RADIUS), or Terminal Access
Controller Access Control System Plus (TACACS+) to validate users who
attempt to access the router by several mechanisms, e.g. a command
line interface or a web-based user interface.
The "server" list is directly under the "tacacsplus" container, which
is to hold a list of different TACACS+ server and use server-type to
distinguish the three protocols. The list of servers is for
redundancy purpose.
Most of the parameters in the "server" list are taken directly from
the TACACS+ protocol [I-D.ietf-opsawg-tacacs], and some are derived
from the wide implementation of network equipment manufacturers. For
example, when there are multiple interfaces connected to the TACACS+
server, the source address of outgoing TACACS+ packets could be
specified, or the source address could be specified through the
interface setting. For the TACACS + server located in a private
network, a VRF instance needs to be specified.
The "statistics" container under the "server list" is to record
session statistics and usage information during user access which
include the amount of data a user has sent and/or received during a
session.
The data model for TACACS+ client has the following structure:
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module: ietf-system-tacacsplus
augment /sys:system:
+--rw tacacsplus {tacacsplus}?
+--rw server* [name]
+--rw name string
+--rw server-type? enumeration
+--rw address inet:host
+--rw port? inet:port-number
+--rw shared-secret string
+--rw (source-type)?
| +--:(source-ip)
| | +--rw source-ip? inet:ip-address
| +--:(source-interface)
| +--rw source-interface? if:interface-ref
+--rw single-connection? boolean
+--rw timeout? uint16
+--rw vrf-instance?
| -> /ni:network-instances/network-instance/name
+--ro statistics
+--ro connection-opens? yang:counter64
+--ro connection-closes? yang:counter64
+--ro connection-aborts? yang:counter64
+--ro connection-failures? yang:counter64
+--ro connection-timeouts? yang:counter64
+--ro messages-sent? yang:counter64
+--ro messages-received? yang:counter64
+--ro errors-received? yang:counter64
4. TACACS+ Client Module
<CODE BEGINS> file "ietf-system-tacacsplus@2019-06-20.yang"
module ietf-system-tacacsplus {
yang-version 1.1;
namespace "urn:ietf:params:xml:ns:yang:ietf-system-tacacsplus";
prefix sys-tcsplus;
import ietf-inet-types {
prefix inet;
reference "RFC 6991: Common YANG Data Types";
}
import ietf-yang-types {
prefix yang;
reference "RFC 6991: Common YANG Data Types";
}
import ietf-network-instance {
prefix ni;
reference
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"RFC 8529: YANG Data Model for Network Instances";
}
import ietf-interfaces {
prefix if;
reference
"RFC 8343: A YANG Data Model for Interface Management";
}
import ietf-system {
prefix sys;
reference "RFC 7317: A YANG Data Model for System Management";
}
import ietf-netconf-acm {
prefix nacm;
reference "RFC 8341: Network Configuration Access Control Model";
}
organization
"IETF Opsawg (Operations and Management Area Working Group)";
contact
"WG Web: <http://tools.ietf.org/wg/opsawg/>
WG List: <mailto:opsawg@ietf.org>
Editor: Guangying Zheng
<mailto:zhengguangying@huawei.com>";
description
"This module provides configuration of TACACS+ client.
Copyright (c) 2018 IETF Trust and the persons identified as
authors of the code. All rights reserved.
Redistribution and use in source and binary forms, with or
without modification, is permitted pursuant to, and subject
to the license terms contained in, the Simplified BSD License
set forth in Section 4.c of the IETF Trust's Legal Provisions
Relating to IETF Documents
(http://trustee.ietf.org/license-info).
This version of this YANG module is part of RFC XXXX; see the RFC
itself for full legal notices.";
revision 2019-06-20 {
description
"Initial revision.";
reference "foo";
}
feature tacacsplus {
description
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"Indicates that the device can be configured as a TACACS+
client.";
reference "draft-ietf-opsawg-tacacs-11: The TACACS+ Protocol";
}
grouping statistics {
description
"Grouping for TACACS+ packets statistics attributes";
container statistics {
config false;
description
"A collection of server-related statistics objects";
leaf connection-opens {
type yang:counter64;
description
"Number of new connection requests sent to the server, e.g.
socket open";
}
leaf connection-closes {
type yang:counter64;
description
"Number of connection close requests sent to the server, e.g.
socket close";
}
leaf connection-aborts {
type yang:counter64;
description
"Number of aborted connections to the server. These do
not include connections that are close gracefully.";
}
leaf connection-failures {
type yang:counter64;
description
"Number of connection failures to the server";
}
leaf connection-timeouts {
type yang:counter64;
description
"Number of connection timeouts to the server";
}
leaf messages-sent {
type yang:counter64;
description
"Number of messages sent to the server";
}
leaf messages-received {
type yang:counter64;
description
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"Number of messages received by the server";
}
leaf errors-received {
type yang:counter64;
description
"Number of error messages received from the server";
}
}
}
grouping tacacsplus {
description
"Grouping for TACACS+ attributes";
container tacacsplus {
if-feature "tacacsplus";
description
"Container for TACACS+ configurations and operations.";
list server {
key "name";
ordered-by user;
description
"List of TACACS+ servers used by the device
When the TACACS+ 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 TACACS+ server.";
}
leaf server-type {
type enumeration {
enum authentication {
description
"The server is an authentication server.";
}
enum authorization {
description
"The server is an authorization server.";
}
enum accounting {
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description
"The server is an accounting server.";
}
}
description
"Server type: authentication/authorization/accounting.";
}
leaf address {
type inet:host;
mandatory true;
description
"The address of the TACACS+ server.";
}
leaf port {
type inet:port-number;
default "49";
description
"The port number of TACACS+ Server port.";
}
leaf shared-secret {
type string;
mandatory true;
nacm:default-deny-all;
description
"The shared secret, which is known to both the
TACACS+ client and server. TACACS+ server administrators
SHOULD configure secret keys of minimum
16 characters length.";
reference "TACACS+ protocol:";
}
choice source-type {
description
"The source address type for outbound TACACS+ packets.";
case source-ip {
leaf source-ip {
type inet:ip-address;
description
"Specifies source IP address for TACACS+ outbound
packets.";
}
}
case source-interface {
leaf source-interface {
type if:interface-ref;
description
"Specifies the interface from which the IP address is
derived for use as the source for the outbound TACACS+
packet";
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}
}
}
leaf single-connection {
type boolean;
default "false";
description
"Whether the single connection mode is enabled for the
server. By default, the single connection mode is
disabled.";
}
leaf timeout {
type uint16 {
range "1..300";
}
units "seconds";
default "5";
description
"The number of seconds the device will wait for a
response from each TACACS+ server before trying with a
different server.";
}
leaf vrf-instance {
type leafref {
path "/ni:network-instances/ni:network-instance/ni:name";
}
description
"Specifies the VPN Routing and Forwarding (VRF) instance to
use to communicate with the TACACS+ server.";
}
uses statistics;
}
}
}
augment "/sys:system" {
description
"Augment the system model with authorization and accounting
attributes
Augment the system model with the tacacsplus model";
uses tacacsplus;
}
}
<CODE ENDS>
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5. Security Considerations
The YANG module defined in this document is designed to be accessed
via network management protocols such as NETCONF [RFC6241] or
RESTCONF [RFC8040]. The lowest NETCONF layer is the secure transport
layer, and the mandatory-to-implement secure transport is Secure
Shell (SSH) [RFC6242]. The lowest RESTCONF layer is HTTPS, and the
mandatory-to-implement secure transport is TLS [RFC8446].
The NETCONF access control model [RFC8341] provides the means to
restrict access for particular NETCONF or RESTCONF users to a
preconfigured subset of all available NETCONF or RESTCONF protocol
operations and content.
There are a number of data nodes defined in this YANG module that are
writable/creatable/deletable (i.e., config true, which is the
default). These data nodes may be considered sensitive or vulnerable
in some network environments. Write operations (e.g., edit-config)
to these data nodes without proper protection can have a negative
effect on network operations.
This document describes the use of TACACS+ for purposes of
authentication, authorization and accounting, it is vulnerable to all
of the threats that are present in TACACS+ applications. For a
discussion of such threats, see Section 9 of the TACACS+ Protocol
[I-D.ietf-opsawg-tacacs].
6. IANA Considerations
This document registers a URI in the IETF XML registry [RFC3688].
Following the format in [RFC3688], the following registration is
requested to be made:
URI: urn:ietf:params:xml:ns:yang:ietf-system-tacacsplus
Registrant Contact: The IESG.
XML: N/A, the requested URI is an XML namespace.
This document registers a YANG module in the YANG Module Names
registry [RFC7950].
Name: ietf-system-tacacsplus
Namespace: urn:ietf:params:xml:ns:yang: ietf-tacacsplus
Prefix: sys-tcsplus
Reference: RFC XXXX
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7. Acknowledgments
The authors wish to thank Alex Campbell and Ebben Aries, Alan DeKok,
Joe Clarke, many others for their helpful comments.
8. References
8.1. Normative References
[RFC2119] Bradner, S., "Key words for use in RFCs to Indicate
Requirement Levels", BCP 14, RFC 2119,
DOI 10.17487/RFC2119, March 1997,
<https://www.rfc-editor.org/info/rfc2119>.
[RFC3688] Mealling, M., "The IETF XML Registry", BCP 81, RFC 3688,
DOI 10.17487/RFC3688, January 2004,
<https://www.rfc-editor.org/info/rfc3688>.
[RFC6241] Enns, R., Ed., Bjorklund, M., Ed., Schoenwaelder, J., Ed.,
and A. Bierman, Ed., "Network Configuration Protocol
(NETCONF)", RFC 6241, DOI 10.17487/RFC6241, June 2011,
<https://www.rfc-editor.org/info/rfc6241>.
[RFC6242] Wasserman, M., "Using the NETCONF Protocol over Secure
Shell (SSH)", RFC 6242, DOI 10.17487/RFC6242, June 2011,
<https://www.rfc-editor.org/info/rfc6242>.
[RFC6991] Schoenwaelder, J., Ed., "Common YANG Data Types",
RFC 6991, DOI 10.17487/RFC6991, July 2013,
<https://www.rfc-editor.org/info/rfc6991>.
[RFC7317] Bierman, A. and M. Bjorklund, "A YANG Data Model for
System Management", RFC 7317, DOI 10.17487/RFC7317, August
2014, <https://www.rfc-editor.org/info/rfc7317>.
[RFC7950] Bjorklund, M., Ed., "The YANG 1.1 Data Modeling Language",
RFC 7950, DOI 10.17487/RFC7950, August 2016,
<https://www.rfc-editor.org/info/rfc7950>.
[RFC8040] Bierman, A., Bjorklund, M., and K. Watsen, "RESTCONF
Protocol", RFC 8040, DOI 10.17487/RFC8040, January 2017,
<https://www.rfc-editor.org/info/rfc8040>.
[RFC8174] Leiba, B., "Ambiguity of Uppercase vs Lowercase in RFC
2119 Key Words", BCP 14, RFC 8174, DOI 10.17487/RFC8174,
May 2017, <https://www.rfc-editor.org/info/rfc8174>.
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[RFC8340] Bjorklund, M. and L. Berger, Ed., "YANG Tree Diagrams",
BCP 215, RFC 8340, DOI 10.17487/RFC8340, March 2018,
<https://www.rfc-editor.org/info/rfc8340>.
[RFC8341] Bierman, A. and M. Bjorklund, "Network Configuration
Access Control Model", STD 91, RFC 8341,
DOI 10.17487/RFC8341, March 2018,
<https://www.rfc-editor.org/info/rfc8341>.
[RFC8342] Bjorklund, M., Schoenwaelder, J., Shafer, P., Watsen, K.,
and R. Wilton, "Network Management Datastore Architecture
(NMDA)", RFC 8342, DOI 10.17487/RFC8342, March 2018,
<https://www.rfc-editor.org/info/rfc8342>.
[RFC8446] Rescorla, E., "The Transport Layer Security (TLS) Protocol
Version 1.3", RFC 8446, DOI 10.17487/RFC8446, August 2018,
<https://www.rfc-editor.org/info/rfc8446>.
8.2. Informative References
[I-D.ietf-opsawg-tacacs]
Dahm, T., Ota, A., dcmgash@cisco.com, d., Carrel, D., and
L. Grant, "The TACACS+ Protocol", draft-ietf-opsawg-
tacacs-13 (work in progress), March 2019.
Authors' Addresses
Guangying Zheng
Huawei
101 Software Avenue, Yuhua District
Nanjing, Jiangsu 210012
China
Email: zhengguangying@huawei.com
Michael Wang
Huawei Technologies, Co., Ltd
101 Software Avenue, Yuhua District
Nanjing 210012
China
Email: wangzitao@huawei.com
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Bo Wu
Huawei
101 Software Avenue, Yuhua District
Nanjing, Jiangsu 210012
China
Email: lana.wubo@huawei.com
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