draft-ietf-netconf-access-control-07.txt   rfc6536.txt 
Internet Engineering Task Force A. Bierman Internet Engineering Task Force (IETF) A. Bierman
Internet-Draft Brocade Request for Comments: 6536 YumaWorks
Intended status: Standards Track M. Bjorklund Category: Standards Track M. Bjorklund
Expires: June 25, 2012 Tail-f Systems ISSN: 2070-1721 Tail-f Systems
December 23, 2011 March 2012
Network Configuration Protocol (NETCONF) Access Control Model Network Configuration Protocol (NETCONF) Access Control Model
draft-ietf-netconf-access-control-07
Abstract Abstract
The standardization of network configuration interfaces for use with The standardization of network configuration interfaces for use with
the NETCONF protocol requires a structured and secure operating the Network Configuration Protocol (NETCONF) requires a structured
environment that promotes human usability and multi-vendor and secure operating environment that promotes human usability and
interoperability. There is a need for standard mechanisms to multi-vendor interoperability. There is a need for standard
restrict NETCONF protocol access for particular users to a pre- mechanisms to restrict NETCONF protocol access for particular users
configured subset of all available NETCONF protocol operations and to a pre-configured subset of all available NETCONF protocol
content. This document defines such an access control model. operations and content. This document defines such an access control
model.
Status of this Memo
This Internet-Draft is submitted in full conformance with the Status of This Memo
provisions of BCP 78 and BCP 79.
Internet-Drafts are working documents of the Internet Engineering This is an Internet Standards Track document.
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 This document is a product of the Internet Engineering Task Force
and may be updated, replaced, or obsoleted by other documents at any (IETF). It represents the consensus of the IETF community. It has
time. It is inappropriate to use Internet-Drafts as reference received public review and has been approved for publication by the
material or to cite them other than as "work in progress." Internet Engineering Steering Group (IESG). Further information on
Internet Standards is available in Section 2 of RFC 5741.
This Internet-Draft will expire on June 25, 2012. 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/rfc6536.
Copyright Notice Copyright Notice
Copyright (c) 2011 IETF Trust and the persons identified as the Copyright (c) 2012 IETF Trust and the persons identified as the
document authors. All rights reserved. document authors. All rights reserved.
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Table of Contents Table of Contents
1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . . 4 1. Introduction ....................................................3
1.1. Terminology . . . . . . . . . . . . . . . . . . . . . . . 4 1.1. Terminology ................................................3
2. Access Control Design Objectives . . . . . . . . . . . . . . . 6 2. Access Control Design Objectives ................................4
2.1. Access Control Points . . . . . . . . . . . . . . . . . . 6 2.1. Access Control Points ......................................5
2.2. Simplicity . . . . . . . . . . . . . . . . . . . . . . . . 7 2.2. Simplicity .................................................5
2.3. Procedural Interface . . . . . . . . . . . . . . . . . . . 7 2.3. Procedural Interface .......................................6
2.4. Datastore Access . . . . . . . . . . . . . . . . . . . . . 7 2.4. Datastore Access ...........................................6
2.5. Users and Groups . . . . . . . . . . . . . . . . . . . . . 7 2.5. Users and Groups ...........................................6
2.6. Maintenance . . . . . . . . . . . . . . . . . . . . . . . 8 2.6. Maintenance ................................................6
2.7. Configuration Capabilities . . . . . . . . . . . . . . . . 8 2.7. Configuration Capabilities .................................7
2.8. Identifying Security-Sensitive Content . . . . . . . . . . 8 2.8. Identifying Security-Sensitive Content .....................7
3. NETCONF Access Control Model (NACM) . . . . . . . . . . . . . 10 3. NETCONF Access Control Model (NACM) .............................8
3.1. Introduction . . . . . . . . . . . . . . . . . . . . . . . 10 3.1. Introduction ...............................................8
3.1.1. Features . . . . . . . . . . . . . . . . . . . . . . . 10 3.1.1. Features ............................................8
3.1.2. External Dependencies . . . . . . . . . . . . . . . . 11 3.1.2. External Dependencies ...............................9
3.1.3. Message Processing Model . . . . . . . . . . . . . . . 11 3.1.3. Message Processing Model ............................9
3.2. Datastore Access . . . . . . . . . . . . . . . . . . . . . 13 3.2. Datastore Access ..........................................11
3.2.1. Access Rights . . . . . . . . . . . . . . . . . . . . 13 3.2.1. Access Rights ......................................11
3.2.2. <get> and <get-config> Operations . . . . . . . . . . 14 3.2.2. <get> and <get-config> Operations ..................12
3.2.3. <edit-config> Operation . . . . . . . . . . . . . . . 14 3.2.3. <edit-config> Operation ............................12
3.2.4. <copy-config> Operation . . . . . . . . . . . . . . . 15 3.2.4. <copy-config> Operation ............................13
3.2.5. <delete-config> Operation . . . . . . . . . . . . . . 16 3.2.5. <delete-config> Operation ..........................14
3.2.6. <commit> Operation . . . . . . . . . . . . . . . . . . 16 3.2.6. <commit> Operation .................................14
3.2.7. <discard-changes> Operation . . . . . . . . . . . . . 16 3.2.7. <discard-changes> Operation ........................14
3.2.8. <kill-session> Operation . . . . . . . . . . . . . . . 16 3.2.8. <kill-session> Operation ...........................14
3.3. Model Components . . . . . . . . . . . . . . . . . . . . . 16 3.3. Model Components ..........................................15
3.3.1. Users . . . . . . . . . . . . . . . . . . . . . . . . 17 3.3.1. Users ..............................................15
3.3.2. Groups . . . . . . . . . . . . . . . . . . . . . . . . 17 3.3.2. Groups .............................................15
3.3.3. Emergency Recovery Session . . . . . . . . . . . . . . 17 3.3.3. Emergency Recovery Session .........................15
3.3.4. Global Enforcement Controls . . . . . . . . . . . . . 17 3.3.4. Global Enforcement Controls ........................15
3.3.4.1. enable-nacm Switch . . . . . . . . . . . . . . . . 17 3.3.4.1. enable-nacm Switch ........................15
3.3.4.2. read-default Switch . . . . . . . . . . . . . . . 17 3.3.4.2. read-default Switch .......................16
3.3.4.3. write-default Switch . . . . . . . . . . . . . . . 18 3.3.4.3. write-default Switch ......................16
3.3.4.4. exec-default Switch . . . . . . . . . . . . . . . 18 3.3.4.4. exec-default Switch .......................16
3.3.4.5. enable-external-groups Switch . . . . . . . . . . 18 3.3.4.5. enable-external-groups Switch .............17
3.3.5. Access Control Rules . . . . . . . . . . . . . . . . . 19 3.3.5. Access Control Rules ...............................17
3.4. Access Control Enforcement Procedures . . . . . . . . . . 19 3.4. Access Control Enforcement Procedures .....................17
3.4.1. Initial Operation . . . . . . . . . . . . . . . . . . 19 3.4.1. Initial Operation ..................................17
3.4.2. Session Establishment . . . . . . . . . . . . . . . . 20 3.4.2. Session Establishment ..............................18
3.4.3. "access-denied" Error Handling . . . . . . . . . . . . 20 3.4.3. "access-denied" Error Handling .....................18
3.4.4. Incoming RPC Message Validation . . . . . . . . . . . 20 3.4.4. Incoming RPC Message Validation ....................18
3.4.5. Data Node Access Validation . . . . . . . . . . . . . 23 3.4.5. Data Node Access Validation ........................21
3.4.6. Outgoing <notification> Authorization . . . . . . . . 25 3.4.6. Outgoing <notification> Authorization ..............23
3.5. Data Model Definitions . . . . . . . . . . . . . . . . . . 27 3.5. Data Model Definitions ....................................26
3.5.1. Data Organization . . . . . . . . . . . . . . . . . . 27 3.5.1. Data Organization ..................................26
3.5.2. YANG Module . . . . . . . . . . . . . . . . . . . . . 28 3.5.2. YANG Module ........................................26
3.6. IANA Considerations . . . . . . . . . . . . . . . . . . . 38
3.7. Security Considerations . . . . . . . . . . . . . . . . . 39 3.6. IANA Considerations .......................................36
3.7.1. NACM Configuration and Monitoring Considerations . . . 39 3.7. Security Considerations ...................................36
3.7.2. General Configuration Issues . . . . . . . . . . . . . 40 3.7.1. NACM Configuration and Monitoring Considerations ...37
3.7.3. Data Model Design Considerations . . . . . . . . . . . 42 3.7.2. General Configuration Issues .......................38
4. References . . . . . . . . . . . . . . . . . . . . . . . . . . 43 3.7.3. Data Model Design Considerations ...................40
4.1. Normative References . . . . . . . . . . . . . . . . . . . 43 4. References .....................................................40
4.2. Informative References . . . . . . . . . . . . . . . . . . 43 4.1. Normative References ......................................40
Appendix A. Usage Examples . . . . . . . . . . . . . . . . . . . 44 4.2. Informative References ....................................41
A.1. <groups> Example . . . . . . . . . . . . . . . . . . . . . 44 Appendix A. Usage Examples .......................................42
A.2. Module Rule Example . . . . . . . . . . . . . . . . . . . 45 A.1. <groups> Example ..........................................42
A.3. RPC Rule Example . . . . . . . . . . . . . . . . . . . . . 46 A.2. Module Rule Example .......................................43
A.4. Data Rule Example . . . . . . . . . . . . . . . . . . . . 48 A.3. Protocol Operation Rule Example ...........................44
A.5. Notification Rule Example . . . . . . . . . . . . . . . . 50 A.4. Data Node Rule Example ....................................46
Appendix B. Change Log . . . . . . . . . . . . . . . . . . . . . 52 A.5. Notification Rule Example .................................48
B.1. 06-07 . . . . . . . . . . . . . . . . . . . . . . . . . . 52
B.2. 05-06 . . . . . . . . . . . . . . . . . . . . . . . . . . 52
B.3. 04-05 . . . . . . . . . . . . . . . . . . . . . . . . . . 52
B.4. 03-04 . . . . . . . . . . . . . . . . . . . . . . . . . . 52
B.5. 02-03 . . . . . . . . . . . . . . . . . . . . . . . . . . 53
B.6. 01-02 . . . . . . . . . . . . . . . . . . . . . . . . . . 53
B.7. 00-01 . . . . . . . . . . . . . . . . . . . . . . . . . . 53
B.8. 00 . . . . . . . . . . . . . . . . . . . . . . . . . . . . 53
Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . . 54
1. Introduction 1. Introduction
The NETCONF protocol does not provide any standard mechanisms to The NETCONF protocol does not provide any standard mechanisms to
restrict the protocol operations and content that each user is restrict the protocol operations and content that each user is
authorized to access. authorized to access.
There is a need for inter-operable management of the controlled There is a need for interoperable management of the controlled access
access to administrator selected portions of the available NETCONF to administrator-selected portions of the available NETCONF content
content within a particular server. within a particular server.
This document addresses access control mechanisms for the Operation This document addresses access control mechanisms for the Operations
and Content layers of NETCONF, as defined in [RFC6241]. It contains and Content layers of NETCONF, as defined in [RFC6241]. It contains
three main sections: three main sections:
1. Access Control Design Objectives 1. Access Control Design Objectives
2. NETCONF Access Control Model (NACM) 2. NETCONF Access Control Model (NACM)
3. YANG Data Model (ietf-netconf-acm.yang) 3. YANG Data Model (ietf-netconf-acm.yang)
1.1. Terminology 1.1. Terminology
skipping to change at page 5, line 4 skipping to change at page 4, line 18
o session o session
o user o user
The following terms are defined in [RFC6020] and are not redefined The following terms are defined in [RFC6020] and are not redefined
here: here:
o data node o data node
o data definition statement o data definition statement
The following terms are used throughout this documentation:
access control: A security feature provided by the NETCONF server, The following terms are used throughout this document:
access control: A security feature provided by the NETCONF server
that allows an administrator to restrict access to a subset of all that allows an administrator to restrict access to a subset of all
NETCONF protocol operations and data, based on various criteria. NETCONF protocol operations and data, based on various criteria.
access control model (ACM): A conceptual model used to configure and access control model (ACM): A conceptual model used to configure and
monitor the access control procedures desired by the administrator monitor the access control procedures desired by the administrator
to enforce a particular access control policy. to enforce a particular access control policy.
access control rule: The criteria used to determine if a particular access control rule: The criterion used to determine if a particular
NETCONF protocol operation will be permitted or denied. NETCONF protocol operation will be permitted or denied.
access operation: How a request attempts to access a conceptual access operation: How a request attempts to access a conceptual
object. One of "none", "read", "create", "delete", "update", and object. One of "none", "read", "create", "delete", "update", or
"execute". "execute".
recovery session: A special administrative session that is given recovery session: A special administrative session that is given
unlimited NETCONF access, and is exempt from all access control unlimited NETCONF access and is exempt from all access control
enforcement. The mechanism(s) used by a server to control and enforcement. The mechanism(s) used by a server to control and
identify whether a session is a recovery session or not are identify whether or not a session is a recovery session are
implementation-specific and outside the scope of this document. implementation specific and outside the scope of this document.
write access: A shorthand for the "create", "delete", and "update" write access: A shorthand for the "create", "delete", and "update"
access operations. access operations.
2. Access Control Design Objectives 2. Access Control Design Objectives
This section documents the design objectives for the NETCONF Access This section documents the design objectives for the NETCONF Access
Control Model presented in Section 3. Control Model presented in Section 3.
2.1. Access Control Points 2.1. Access Control Points
NETCONF allows new protocol operations to be added at any time, and NETCONF allows new protocol operations to be added at any time, and
the YANG data modeling language supports this feature. It is not the YANG Data Modeling Language supports this feature. It is not
possible to design an ACM for NETCONF that only focuses on a static possible to design an ACM for NETCONF that only focuses on a static
set of protocol operations, like some other protocols. Since few set of protocol operations, like some other protocols. Since few
assumptions can be made about an arbitrary protocol operation, the assumptions can be made about an arbitrary protocol operation, the
NETCONF architectural server components need to be protected at three NETCONF architectural server components need to be protected at three
conceptual control points. conceptual control points.
These access control points, described in Figure 1, are as follows:
protocol operation: Permission to invoke specific protocol
operations.
datastore: Permission to read and/or alter specific data nodes
within any datastore.
notification: Permission to receive specific notification event
types.
+-------------+ +-------------+ +-------------+ +-------------+
client | protocol | | data node | client | protocol | | data node |
request --> | operation | -------------> | access | request --> | operation | -------------> | access |
| allowed? | datastore | allowed? | | allowed? | datastore | allowed? |
+-------------+ or state +-------------+ +-------------+ or state +-------------+
data access data access
+----------------+ +----------------+
| notification | | notification |
event --> | allowed? | event --> | allowed? |
+----------------+ +----------------+
Figure 1 Figure 1
The following access control points, described in Figure 1, are
identified:
protocol operation: Permission to invoke specific protocol
operations.
datastore: Permission to read and/or alter specific data nodes
within any datastore.
notification: Permission to receive specific notification event
types.
2.2. Simplicity 2.2. Simplicity
There is concern that a complicated ACM will not be widely deployed, There is concern that a complicated ACM will not be widely deployed
because it is too hard to use. It needs to be easy to do simple because it is too hard to use. It needs to be easy to do simple
things, and possible to do complex things, instead of hard to do things and possible to do complex things, instead of hard to do
everything. everything.
Configuration of the access control system needs to be as simple as Configuration of the access control system needs to be as simple as
possible. Simple and common tasks need to be easy to configure, and possible. Simple and common tasks need to be easy to configure and
require little expertise or domain-specific knowledge. Complex tasks require little expertise or domain-specific knowledge. Complex tasks
are possible using additional mechanisms, which may require are possible using additional mechanisms, which may require
additional expertise. additional expertise.
A single set of access control rules ought to be able to control all A single set of access control rules ought to be able to control all
types of NETCONF protocol operation invocation, all datastore access, types of NETCONF protocol operation invocation, all datastore access,
and all notification events. and all notification events.
Access control ought to be defined with a small and familiar set of Access control ought to be defined with a small and familiar set of
permissions, while still allowing full control of NETCONF datastore permissions, while still allowing full control of NETCONF datastore
access. access.
2.3. Procedural Interface 2.3. Procedural Interface
The NETCONF protocol uses a remote procedure call model, and an The NETCONF protocol uses a remote procedure call model and an
extensible set of protocol operations. Access control for any extensible set of protocol operations. Access control for any
possible protocol operation is necessary. possible protocol operation is necessary.
2.4. Datastore Access 2.4. Datastore Access
It is necessary to control access to specific nodes and subtrees It is necessary to control access to specific nodes and subtrees
within the NETCONF datastore, regardless of which protocol operation, within the NETCONF datastore, regardless of which protocol operation,
standard or proprietary, was used to access the datastore. standard or proprietary, was used to access the datastore.
2.5. Users and Groups 2.5. Users and Groups
It is necessary that access control rules for a single user or a It is necessary that access control rules for a single user or a
configurable group of users can be configured. configurable group of users can be configured.
The ACM needs to support the concept of administrative groups, to The ACM needs to support the concept of administrative groups, to
support the well-established distinction between a root account and support the well-established distinction between a root account and
other types of less-privileged conceptual user accounts. These other types of less-privileged conceptual user accounts. These
groups need to be configurable by the administrator. groups need to be configurable by the administrator.
It is necessary that the user-to-group mapping can be delegated to a It is necessary that the user-to-group mapping can be delegated to a
central server, such as a RADIUS server [RFC2865] [RFC5607]. Since central server, such as a RADIUS server [RFC2865][RFC5607]. Since
authentication is performed by the NETCONF transport layer, and authentication is performed by the NETCONF transport layer and RADIUS
RADIUS performs authentication and service authorization at the same performs authentication and service authorization at the same time,
time, the underlying NETCONF transport needs to be able to report a the underlying NETCONF transport needs to be able to report a set of
set of group names associated with the user to the server. It is group names associated with the user to the server. It is necessary
necessary that the administrator can disable the usage of these group that the administrator can disable the usage of these group names
names within the ACM. within the ACM.
2.6. Maintenance 2.6. Maintenance
It ought to be possible to disable part or all of the access control It ought to be possible to disable part or all of the access control
model enforcement procedures without deleting any access control model enforcement procedures without deleting any access control
rules. rules.
2.7. Configuration Capabilities 2.7. Configuration Capabilities
Suitable configuration and monitoring mechanisms are needed to allow Suitable configuration and monitoring mechanisms are needed to allow
an administrator to easily manage all aspects of the ACM behavior. A an administrator to easily manage all aspects of the ACM's behavior.
standard data model, suitable for use with the <edit-config> protocol A standard data model, suitable for use with the <edit-config>
operation needs to be available for this purpose. protocol operation, needs to be available for this purpose.
Access control rules to restrict access operations on specific Access control rules to restrict access operations on specific
subtrees within the configuration datastore need to be supported. subtrees within the configuration datastore need to be supported.
2.8. Identifying Security-Sensitive Content 2.8. Identifying Security-Sensitive Content
One of the most important aspects of the data model documentation, One of the most important aspects of the data model documentation,
and biggest concerns during deployment, is the identification of and biggest concerns during deployment, is the identification of
security-sensitive content. This applies to protocol operations in security-sensitive content. This applies to protocol operations in
NETCONF, not just data and notifications. NETCONF, not just data and notifications.
It is mandatory for security-sensitive objects to be documented in It is mandatory for security-sensitive objects to be documented in
the Security Considerations section of an RFC. This is nice, but it the Security Considerations section of an RFC. This is nice, but it
is not good enough, for the following reasons: is not good enough, for the following reasons:
o This documentation-only approach forces administrators to study o This documentation-only approach forces administrators to study
the RFC and determine if there are any potential security risks the RFC and determine if there are any potential security risks
introduced by a new data model. introduced by a new data model.
o If any security risks are identified, then the administrator can o If any security risks are identified, then the administrator must
study some more RFC text, and determine how to mitigate the study some more RFC text and determine how to mitigate the
security risk(s). security risk(s).
o The ACM on each server can be configured to mitigate the security o The ACM on each server must be configured to mitigate the security
risks, e.g., require privileged access to read or write the risks, e.g., require privileged access to read or write the
specific data identified in the Security Considerations section. specific data identified in the Security Considerations section.
o If the ACM is not pre-configured, then there will be a time window o If the ACM is not pre-configured, then there will be a time window
of vulnerability, after the new data model is loaded, and before of vulnerability after the new data model is loaded and before the
the new access control rules for that data model are configured, new access control rules for that data model are configured,
enabled, and debugged. enabled, and debugged.
Often, the administrator just wants to disable default access to the Often, the administrator just wants to disable default access to the
secure content, so no inadvertent or malicious changes can be made to secure content, so no inadvertent or malicious changes can be made to
the server. This allows the default rules to be more lenient, the server. This allows the default rules to be more lenient,
without significantly increasing the security risk. without significantly increasing the security risk.
A data model designer needs to be able to use machine-readable A data model designer needs to be able to use machine-readable
statements to identify NETCONF content which needs to be protected by statements to identify NETCONF content, which needs to be protected
default. This will allow client and server tools to automatically by default. This will allow client and server tools to automatically
identify data-model specific security risks, by denying access to identify data-model-specific security risks, by denying access to
sensitive data unless the user is explicitly authorized to perform sensitive data unless the user is explicitly authorized to perform
the requested access operation. the requested access operation.
3. NETCONF Access Control Model (NACM) 3. NETCONF Access Control Model (NACM)
3.1. Introduction 3.1. Introduction
This section provides a high-level overview of the access control This section provides a high-level overview of the access control
model structure. It describes the NETCONF protocol message model structure. It describes the NETCONF protocol message
processing model, and the conceptual access control requirements processing model and the conceptual access control requirements
within that model. within that model.
3.1.1. Features 3.1.1. Features
The NACM data model provides the following features: The NACM data model provides the following features:
o Independent control of RPC, data, and notification access. o Independent control of remote procedure call (RPC), data, and
notification access.
o Simple access control rules configuration data model that is easy o Simple access control rules configuration data model that is easy
to use. to use.
o The concept of an emergency recovery session is supported, but o The concept of an emergency recovery session is supported, but
configuration of the server for this purpose is beyond the scope configuration of the server for this purpose is beyond the scope
of this document. An emergency recovery session will bypass all of this document. An emergency recovery session will bypass all
access control enforcement, in order to allow it to initialize or access control enforcement, in order to allow it to initialize or
repair the NACM configuration. repair the NACM configuration.
skipping to change at page 11, line 7 skipping to change at page 9, line 13
o Access control rules are simple to configure. o Access control rules are simple to configure.
o The number of denied protocol operation requests and denied o The number of denied protocol operation requests and denied
datastore write requests can be monitored by the client. datastore write requests can be monitored by the client.
o Simple unconstrained YANG instance identifiers are used to o Simple unconstrained YANG instance identifiers are used to
configure access control rules for specific data nodes. configure access control rules for specific data nodes.
3.1.2. External Dependencies 3.1.2. External Dependencies
The NETCONF [RFC6241] protocol is used for all management purposes The NETCONF protocol [RFC6241] is used for all management purposes
within this document. within this document.
The YANG Data Modeling Language [RFC6020] is used to define the The YANG Data Modeling Language [RFC6020] is used to define the
NETCONF data models specified in this document. NETCONF data models specified in this document.
3.1.3. Message Processing Model 3.1.3. Message Processing Model
The following diagram shows the conceptual message flow model, The following diagram shows the conceptual message flow model,
including the points at which access control is applied, during including the points at which access control is applied during
NETCONF message processing. NETCONF message processing.
+-------------------------+ +-------------------------+
| session | | session |
| (username) | | (username) |
+-------------------------+ +-------------------------+
| ^ | ^
V | V |
+--------------+ +---------------+ +--------------+ +---------------+
| message | | message | | message | | message |
skipping to change at page 12, line 49 skipping to change at page 10, line 49
| datastore | | instrumentation | | datastore | | instrumentation |
| | <--- | | | | <--- | |
+---------------+ +-----------------+ +---------------+ +-----------------+
Figure 2 Figure 2
The following high-level sequence of conceptual processing steps is The following high-level sequence of conceptual processing steps is
executed for each received <rpc> message, if access control executed for each received <rpc> message, if access control
enforcement is enabled: enforcement is enabled:
o Access control is applied to all <rpc> messages (except <close- o For each active session, access control is applied individually to
session>) received by the server, individually, for each active all <rpc> messages (except <close-session>) received by the
session, unless the session is identified as a "recovery session". server, unless the session is identified as a recovery session.
o If the user is authorized to execute the specified protocol o If the user is authorized to execute the specified protocol
operation, then processing continues, otherwise the request is operation, then processing continues; otherwise, the request is
rejected with an "access-denied" error. rejected with an "access-denied" error.
o If the configuration datastore or conceptual state data is o If the configuration datastore or conceptual state data is
accessed by the protocol operation, then the server checks if the accessed by the protocol operation, then the server checks if the
client is authorized to access the nodes in the data store. If client is authorized to access the nodes in the datastore. If the
the user is authorized to perform the requested access operation user is authorized to perform the requested access operation on
on the requested data, then processing continues. the requested data, then processing continues.
The following sequence of conceptual processing steps is executed for The following sequence of conceptual processing steps is executed for
each generated notification event, if access control enforcement is each generated notification event, if access control enforcement is
enabled: enabled:
o Server instrumentation generates a notification, for a particular o Server instrumentation generates a notification for a particular
subscription. subscription.
o The notification access control enforcer checks the notification o The notification access control enforcer checks the notification
event type, and if it is one which the user is not authorized to event type, and if it is one that the user is not authorized to
read, then the notification is dropped for that subscription. read, then the notification is dropped for that subscription.
3.2. Datastore Access 3.2. Datastore Access
The same access control rules apply to all datastores. For example, The same access control rules apply to all datastores, for example,
the candidate configuration datastore or the running configuration the candidate configuration datastore or the running configuration
datastore. datastore.
Only the standard NETCONF datastores (candidate, running, and Only the standard NETCONF datastores (candidate, running, and
startup) are controlled by NACM. Local or remote files or datastores startup) are controlled by NACM. Local or remote files or datastores
accessed via the <url> parameter are not controlled by NACM. accessed via the <url> parameter are not controlled by NACM.
3.2.1. Access Rights 3.2.1. Access Rights
A small set of hard-wired datastore access rights is needed to A small set of hard-wired datastore access rights is needed to
control access to all possible NETCONF protocol operations, including control access to all possible NETCONF protocol operations, including
vendor extensions to the standard protocol operation set. vendor extensions to the standard protocol operation set.
The "CRUDX" model can support all NETCONF protocol operations: The "CRUDX" model can support all NETCONF protocol operations:
o Create: Allows the client to add a new data node instance to a o Create: allows the client to add a new data node instance to a
datastore. datastore.
o Read: Allows the client to read a data node instance from a o Read: allows the client to read a data node instance from a
datastore, or receive the notification event type. datastore or receive the notification event type.
o Update: Allows the client to update an existing data node instance o Update: allows the client to update an existing data node instance
in a datastore. in a datastore.
o Delete: Allows the client to delete a data node instance from a o Delete: allows the client to delete a data node instance from a
datastore. datastore.
o eXec: Allows the client to execute the protocol operation. o eXec: allows the client to execute the protocol operation.
3.2.2. <get> and <get-config> Operations 3.2.2. <get> and <get-config> Operations
Data nodes to which the client does not have read access are silently Data nodes to which the client does not have read access are silently
omitted from the <rpc-reply> message. This is done to allow NETCONF omitted from the <rpc-reply> message. This is done to allow NETCONF
filters for <get> and <get-config> to function properly, instead of filters for <get> and <get-config> to function properly, instead of
causing an "access-denied" error because the filter criteria would causing an "access-denied" error because the filter criteria would
otherwise include unauthorized read access to some data nodes. For otherwise include unauthorized read access to some data nodes. For
NETCONF filtering purposes, the selection criteria is applied to the NETCONF filtering purposes, the selection criteria is applied to the
subset of nodes that the user is authorized to read, not the entire subset of nodes that the user is authorized to read, not the entire
datastore. datastore.
3.2.3. <edit-config> Operation 3.2.3. <edit-config> Operation
The NACM access rights are not directly coupled to the <edit-config> The NACM access rights are not directly coupled to the <edit-config>
"operation" attribute, although they are similar. Instead, a NACM "operation" attribute, although they are similar. Instead, a NACM
access right applies to all protocol operations which would result in access right applies to all protocol operations that would result in
a particular access operation to the target datastore. This section a particular access operation to the target datastore. This section
describes how these access rights apply to the specific access describes how these access rights apply to the specific access
operations supported by the <edit-config> protocol operation. operations supported by the <edit-config> protocol operation.
If the effective access operation is "none" (i.e., default- If the effective access operation is "none" (i.e., default-
operation="none") for a particular data node, then no access control operation="none") for a particular data node, then no access control
is applied to that data node. This is required to allow access to a is applied to that data node. This is required to allow access to a
sub-tree within larger data structure. For example, a user may be subtree within a larger data structure. For example, a user may be
authorized to create a new "/interfaces/interface" list entry, but authorized to create a new "/interfaces/interface" list entry but not
not be authorized to create or delete its parent container be authorized to create or delete its parent container
("/interfaces"). If the "/interfaces" container already exists in ("/interfaces"). If the "/interfaces" container already exists in
the target datastore, then the effective operation will be "none" for the target datastore, then the effective operation will be "none" for
the "/interfaces" node if an "/interfaces/interface" list entry is the "/interfaces" node if an "/interfaces/interface" list entry is
edited. edited.
If the protocol operation would result in the creation of a data If the protocol operation would result in the creation of a datastore
store node, and the user does not have "create" access permission for node and the user does not have "create" access permission for that
that node, the protocol operation is rejected with an "access-denied" node, the protocol operation is rejected with an "access-denied"
error. error.
If the protocol operation would result in the deletion of a data If the protocol operation would result in the deletion of a datastore
store node, and the user does not have "delete" access permission for node and the user does not have "delete" access permission for that
that node, the protocol operation is rejected with an "access-denied" node, the protocol operation is rejected with an "access-denied"
error. error.
If the protocol operation would result in the modification of a data If the protocol operation would result in the modification of a
store node, and the user does not have "update" access permission for datastore node and the user does not have "update" access permission
that node, the protocol operation is rejected with an "access-denied" for that node, the protocol operation is rejected with an "access-
error. denied" error.
A "merge" or "replace" <edit-config> operation may include data nodes A "merge" or "replace" <edit-config> operation may include data nodes
which do not alter portions of the existing datastore. For example, that do not alter portions of the existing datastore. For example, a
a container or list node may be present for naming purposes, but does container or list node may be present for naming purposes but does
not actually alter the corresponding datastore node. These unaltered not actually alter the corresponding datastore node. These unaltered
data nodes are ignored by the server, and do not require any access data nodes are ignored by the server and do not require any access
rights by the client. rights by the client.
A "merge" <edit-config> operation may include data nodes, but not A "merge" <edit-config> operation may include data nodes but not
include particular child data nodes that are present in the include particular child data nodes that are present in the
datastore. These missing data nodes within the scope of a "merge" datastore. These missing data nodes within the scope of a "merge"
<edit-config> operation are ignored by the server, and do not require <edit-config> operation are ignored by the server and do not require
any access rights by the client. any access rights by the client.
The contents of specific restricted datastore nodes MUST NOT be The contents of specific restricted datastore nodes MUST NOT be
exposed in any <rpc-error> elements within the reply. exposed in any <rpc-error> elements within the reply.
3.2.4. <copy-config> Operation 3.2.4. <copy-config> Operation
Access control for the <copy-config> protocol operation requires Access control for the <copy-config> protocol operation requires
special consideration because the administrator may be replacing the special consideration because the administrator may be replacing the
entire target datastore. entire target datastore.
If the source of the <copy-config> protocol operation is the running If the source of the <copy-config> protocol operation is the running
configuration datastore, and the target is the startup configuration configuration datastore and the target is the startup configuration
datastore, the client is only required to have permission to execute datastore, the client is only required to have permission to execute
the <copy-config> protocol operation. the <copy-config> protocol operation.
Otherwise: Otherwise:
o If the source of the <copy-config> operation is a datastore, then o If the source of the <copy-config> operation is a datastore, then
data nodes to which the client does not have read access are data nodes to which the client does not have read access are
silently omitted. silently omitted.
o If the target of the <copy-config> operation is a datastore, the o If the target of the <copy-config> operation is a datastore, the
client needs access to the modified nodes. Specifically: client needs access to the modified nodes, specifically:
If the protocol operation would result in the creation of a * If the protocol operation would result in the creation of a
data store node, and the user does not have "create" access datastore node and the user does not have "create" access
permission for that node, the protocol operation is rejected permission for that node, the protocol operation is rejected
with an "access-denied" error. with an "access-denied" error.
If the protocol operation would result in the deletion of a * If the protocol operation would result in the deletion of a
data store node, and the user does not have "delete" access datastore node and the user does not have "delete" access
permission for that node, the protocol operation is rejected permission for that node, the protocol operation is rejected
with an "access-denied" error. with an "access-denied" error.
If the protocol operation would result in the modification of a * If the protocol operation would result in the modification of a
data store node, and the user does not have "update" access datastore node and the user does not have "update" access
permission for that node, the protocol operation is rejected permission for that node, the protocol operation is rejected
with an "access-denied" error. with an "access-denied" error.
3.2.5. <delete-config> Operation 3.2.5. <delete-config> Operation
Access to the <delete-config> protocol operation is denied by Access to the <delete-config> protocol operation is denied by
default. The 'exec-default' parameter does not apply to this default. The "exec-default" leaf does not apply to this protocol
protocol operation. Access control rules must be explicitly operation. Access control rules must be explicitly configured to
configured to allow invocation by a non-recovery session. allow invocation by a non-recovery session.
3.2.6. <commit> Operation 3.2.6. <commit> Operation
The server MUST determine the exact nodes in the running The server MUST determine the exact nodes in the running
configuration datastore which are actually different, and only check configuration datastore that are actually different and only check
"create", "update", and "delete" access permissions for this set of "create", "update", and "delete" access permissions for this set of
nodes, which could be empty. nodes, which could be empty.
For example, if a session can read the entire datastore, but only For example, if a session can read the entire datastore but only
change one leaf, that session needs to be able to edit and commit change one leaf, that session needs to be able to edit and commit
that one leaf. that one leaf.
3.2.7. <discard-changes> Operation 3.2.7. <discard-changes> Operation
The client is only required to have permission to execute the The client is only required to have permission to execute the
<discard-changes> protocol operation. No datastore permissions are <discard-changes> protocol operation. No datastore permissions are
needed. needed.
3.2.8. <kill-session> Operation 3.2.8. <kill-session> Operation
The <kill-session> operation does not directly alter a datastore. The <kill-session> operation does not directly alter a datastore.
However, it allows one session to disrupt another session which is However, it allows one session to disrupt another session that is
editing a datastore. editing a datastore.
Access to the <kill-session> protocol operation is denied by default. Access to the <kill-session> protocol operation is denied by default.
The 'exec-default' parameter does not apply to this protocol The "exec-default" leaf does not apply to this protocol operation.
operation. Access control rules must be explicitly configured to Access control rules must be explicitly configured to allow
allow invocation by a non-recovery session. invocation by a non-recovery session.
3.3. Model Components 3.3. Model Components
This section defines the conceptual components related to access This section defines the conceptual components related to the access
control model. control model.
3.3.1. Users 3.3.1. Users
A "user" is the conceptual entity that is associated with the access A "user" is the conceptual entity that is associated with the access
permissions granted to a particular session. A user is identified by permissions granted to a particular session. A user is identified by
a string which is unique within the server. a string that is unique within the server.
As described in [RFC6241], the user name string is derived from the As described in [RFC6241], the username string is derived from the
transport layer during session establishment. If the transport layer transport layer during session establishment. If the transport layer
cannot authenticate the user, the session is terminated. cannot authenticate the user, the session is terminated.
3.3.2. Groups 3.3.2. Groups
Access to a specific NETCONF protocol operation is granted to a Access to a specific NETCONF protocol operation is granted to a
session, associated with a group, not a user. session, associated with a group, not a user.
A group is identified by its name. All group names are unique within A group is identified by its name. All group names are unique within
the server. the server.
A group member is identified by a user name string. A group member is identified by a username string.
The same user can be a member of multiple groups. The same user can be a member of multiple groups.
3.3.3. Emergency Recovery Session 3.3.3. Emergency Recovery Session
The server MAY support a "recovery session" mechanism, which will The server MAY support a recovery session mechanism, which will
bypass all access control enforcement. This is useful for bypass all access control enforcement. This is useful for
restricting initial access and repairing a broken access control restricting initial access and repairing a broken access control
configuration. configuration.
3.3.4. Global Enforcement Controls 3.3.4. Global Enforcement Controls
There are five global controls that are used to help control how There are five global controls that are used to help control how
access control is enforced. access control is enforced.
3.3.4.1. enable-nacm Switch 3.3.4.1. enable-nacm Switch
A global "enable-nacm" on/off switch is provided to enable or disable A global "enable-nacm" on/off switch is provided to enable or disable
all access control enforcement. When this global switch is set to all access control enforcement. When this global switch is set to
"true", then all requests are checked against the access control "true", then all requests are checked against the access control
rules, and only permitted if configured to allow the specific access rules and only permitted if configured to allow the specific access
request. When this global switch is set to "false", then all access request. When this global switch is set to "false", then all access
requested are permitted. requested are permitted.
3.3.4.2. read-default Switch 3.3.4.2. read-default Switch
An on/off "read-default" switch is provided to enable or disable An on/off "read-default" switch is provided to enable or disable
default access to receive data in replies and notifications. When default access to receive data in replies and notifications. When
the "enable-nacm" global switch is set to "true", then this global the "enable-nacm" global switch is set to "true", then this global
switch is relevant, if no matching access control rule is found to switch is relevant if no matching access control rule is found to
explicitly permit or deny read access to the requested NETCONF explicitly permit or deny read access to the requested NETCONF
datastore data or notification event type. datastore data or notification event type.
When this global switch is set to "permit", and no matching access When this global switch is set to "permit" and no matching access
control rule is found for the NETCONF datastore read or notification control rule is found for the NETCONF datastore read or notification
event requested, then access is permitted. event requested, then access is permitted.
When this global switch is set to "deny", and no matching access When this global switch is set to "deny" and no matching access
control rule is found for the NETCONF datastore read or notification control rule is found for the NETCONF datastore read or notification
event requested, then access is denied. event requested, then access is denied.
3.3.4.3. write-default Switch 3.3.4.3. write-default Switch
An on/off "write-default" switch is provided to enable or disable An on/off "write-default" switch is provided to enable or disable
default access to alter configuration data. When the "enable-nacm" default access to alter configuration data. When the "enable-nacm"
global switch is set to "true", then this global switch is relevant, global switch is set to "true", then this global switch is relevant
if no matching access control rule is found to explicitly permit or if no matching access control rule is found to explicitly permit or
deny write access to the requested NETCONF datastore data. deny write access to the requested NETCONF datastore data.
When this global switch is set to "permit", and no matching access When this global switch is set to "permit" and no matching access
control rule is found for the NETCONF datastore write requested, then control rule is found for the NETCONF datastore write requested, then
access is permitted. access is permitted.
When this global switch is set to "deny", and no matching access When this global switch is set to "deny" and no matching access
control rule is found for the NETCONF datastore write requested, then control rule is found for the NETCONF datastore write requested, then
access is denied. access is denied.
3.3.4.4. exec-default Switch 3.3.4.4. exec-default Switch
An on/off "exec-default" switch is provided to enable or disable An on/off "exec-default" switch is provided to enable or disable
default access to execute protocol operations. When the "enable- default access to execute protocol operations. When the "enable-
nacm" global switch is set to "true", then this global switch is nacm" global switch is set to "true", then this global switch is
relevant, if no matching access control rule is found to explicitly relevant if no matching access control rule is found to explicitly
permit or deny access to the requested NETCONF protocol operation. permit or deny access to the requested NETCONF protocol operation.
When this global switch is set to "permit", and no matching access When this global switch is set to "permit" and no matching access
control rule is found for the NETCONF protocol operation requested, control rule is found for the NETCONF protocol operation requested,
then access is permitted. then access is permitted.
When this global switch is set to "deny", and no matching access When this global switch is set to "deny" and no matching access
control rule is found for the NETCONF protocol operation requested, control rule is found for the NETCONF protocol operation requested,
then access is denied. then access is denied.
3.3.4.5. enable-external-groups Switch 3.3.4.5. enable-external-groups Switch
When this global switch is set to "true", the group names reported by When this global switch is set to "true", the group names reported by
the NETCONF transport layer for a session are used together with the the NETCONF transport layer for a session are used together with the
locally configured group names, to determine the access control rules locally configured group names to determine the access control rules
for the session. for the session.
When this switch is set to "false", the group names reported by the When this switch is set to "false", the group names reported by the
NETCONF transport layer are ignored by NACM. NETCONF transport layer are ignored by NACM.
3.3.5. Access Control Rules 3.3.5. Access Control Rules
There are 4 types of rules available in NACM: There are four types of rules available in NACM:
module rule: Controls access for definitions in a specific YANG module rule: controls access for definitions in a specific YANG
module, identified by its name. module, identified by its name.
protocol operation rule: Controls access for a specific protocol protocol operation rule: controls access for a specific protocol
operation, identified by its YANG module and name. operation, identified by its YANG module and name.
data node rule: Controls access for a specific data node, identified data node rule: controls access for a specific data node, identified
by its path location within the conceptual XML document for the by its path location within the conceptual XML document for the
data node. data node.
notification rule: Controls access for a specific notification event notification rule: controls access for a specific notification event
type, identified by its YANG module and name. type, identified by its YANG module and name.
3.4. Access Control Enforcement Procedures 3.4. Access Control Enforcement Procedures
There are seven separate phases that need to be addressed, four of There are seven separate phases that need to be addressed, four of
which are related to the NETCONF message processing model. In which are related to the NETCONF message processing model
addition, the initial start-up mode for a NETCONF server, session (Section 3.1.3). In addition, the initial startup mode for a NETCONF
establishment, and "access-denied" error handling procedures also server, session establishment, and "access-denied" error-handling
need to be considered. procedures also need to be considered.
The server MUST use the access control rules in effect at the time it The server MUST use the access control rules in effect at the time it
starts processing the message. The same access control rules MUST starts processing the message. The same access control rules MUST
stay in effect for the processing of the entire message. stay in effect for the processing of the entire message.
3.4.1. Initial Operation 3.4.1. Initial Operation
Upon the very first start-up of the NETCONF server, the access Upon the very first startup of the NETCONF server, the access control
control configuration will probably not be present. If it isn't, a configuration will probably not be present. If it isn't, a server
server MUST NOT allow any write access to any session role except a MUST NOT allow any write access to any session role except a recovery
"recovery session". session.
Access rules are enforced any time a request is initiated from a user Access rules are enforced any time a request is initiated from a user
session. Access control is not enforced for server-initiated access session. Access control is not enforced for server-initiated access
requests, such as the initial load of the running datastore, during requests, such as the initial load of the running datastore, during
bootup. bootup.
3.4.2. Session Establishment 3.4.2. Session Establishment
The access control model applies specifically to the well-formed XML The access control model applies specifically to the well-formed XML
content transferred between a client and a server, after session content transferred between a client and a server after session
establishment has been completed, and after the <hello> exchange has establishment has been completed and after the <hello> exchange has
been successfully completed. been successfully completed.
Once session establishment is completed, and a user has been Once session establishment is completed and a user has been
authenticated, the NETCONF transport layer reports the user name and authenticated, the NETCONF transport layer reports the username and a
a possibly empty set of group names associated with the user to the possibly empty set of group names associated with the user to the
NETCONF server. The NETCONF server will enforce the access control NETCONF server. The NETCONF server will enforce the access control
rules, based on the supplied user name, group names, and the rules, based on the supplied username, group names, and the
configuration data stored on the server. configuration data stored on the server.
3.4.3. "access-denied" Error Handling 3.4.3. "access-denied" Error Handling
The "access-denied" error-tag is generated when the access control The "access-denied" error-tag is generated when the access control
system denies access to either a request to invoke a protocol system denies access to either a request to invoke a protocol
operation or a request to perform a particular access operation on operation or a request to perform a particular access operation on
the configuration datastore. the configuration datastore.
A server MUST NOT include any information the client is not allowed A server MUST NOT include any information the client is not allowed
to read in any <error-info> elements within the <rpc-error> response. to read in any <error-info> elements within the <rpc-error> response.
3.4.4. Incoming RPC Message Validation 3.4.4. Incoming RPC Message Validation
The diagram below shows the basic conceptual structure of the access The diagram below shows the basic conceptual structure of the access
control processing model for incoming NETCONF <rpc> messages, within control processing model for incoming NETCONF <rpc> messages within a
a server. server.
NETCONF server NETCONF server
+------------+ +------------+
| XML | | XML |
| message | | message |
| dispatcher | | dispatcher |
+------------+ +------------+
| |
| |
V V
skipping to change at page 21, line 39 skipping to change at page 19, line 39
+----------------------+ +----------------------+
| | | |
| configuration | | configuration |
| datastore | | datastore |
+----------------------+ +----------------------+
Figure 3 Figure 3
Access control begins with the message dispatcher. Access control begins with the message dispatcher.
After the server validates the <rpc> element, and determines the After the server validates the <rpc> element and determines the
namespace URI and the element name of the protocol operation being namespace URI and the element name of the protocol operation being
requested, the server verifies that the user is authorized to invoke requested, the server verifies that the user is authorized to invoke
the protocol operation. the protocol operation.
The server MUST separately authorize every protocol operation by The server MUST separately authorize every protocol operation by
following these steps: following these steps:
1. If the "enable-nacm" leaf is set to "false", then the protocol 1. If the "enable-nacm" leaf is set to "false", then the protocol
operation is permitted. operation is permitted.
2. If the requesting session is identified as a "recovery session", 2. If the requesting session is identified as a recovery session,
then the protocol operation is permitted. then the protocol operation is permitted.
3. If the requested operation is the NETCONF <close-session> 3. If the requested operation is the NETCONF <close-session>
protocol operation, then the protocol operation is permitted. protocol operation, then the protocol operation is permitted.
4. Check all the "group" entries for ones that contain a "user- 4. Check all the "group" entries for ones that contain a "user-
name" entry that equals the user name for the session making the name" entry that equals the username for the session making the
request. If the "enable-external-groups" leaf is "true", add to request. If the "enable-external-groups" leaf is "true", add to
these groups the set of groups provided by the transport layer. these groups the set of groups provided by the transport layer.
5. If no groups are found, continue with step 10. 5. If no groups are found, continue with step 10.
6. Process all rule-list entries, in the order they appear in the 6. Process all rule-list entries, in the order they appear in the
configuration. If a rule-list's "group" leaf-list does not configuration. If a rule-list's "group" leaf-list does not
match any of the user's groups, proceed to the next rule-list match any of the user's groups, proceed to the next rule-list
entry. entry.
7. For each rule-list entry found, process all rules, in order, 7. For each rule-list entry found, process all rules, in order,
until a rule that matches the requested access operation is until a rule that matches the requested access operation is
found. A rule matches if all of the following criteria are met: found. A rule matches if all of the following criteria are met:
* The rule's "module-name" leaf is "*", or equals the name of * The rule's "module-name" leaf is "*" or equals the name of
the YANG module where the protocol operation is defined. the YANG module where the protocol operation is defined.
* The rule does not have a "rule-type" defined, or the "rule- * The rule does not have a "rule-type" defined or the "rule-
type" is "protocol-operation" and the "rpc-name" is "*" or type" is "protocol-operation" and the "rpc-name" is "*" or
equals the name of the requested protocol operation. equals the name of the requested protocol operation.
* The rule's "access-operations" leaf has the "exec" bit set, * The rule's "access-operations" leaf has the "exec" bit set or
or has the special value "*". has the special value "*".
8. If a matching rule is found, then the "action" leaf is checked. 8. If a matching rule is found, then the "action" leaf is checked.
If it is equal to "permit", then the protocol operation is If it is equal to "permit", then the protocol operation is
permitted, otherwise it is denied. permitted; otherwise, it is denied.
9. Otherwise, no matching rule was found in any rule-list entry. 9. At this point, no matching rule was found in any rule-list
entry.
10. If the requested protocol operation is defined in a YANG module 10. If the requested protocol operation is defined in a YANG module
advertised in the server capabilities, and the "rpc" statement advertised in the server capabilities and the "rpc" statement
contains a "nacm:default-deny-all" statement, then the protocol contains a "nacm:default-deny-all" statement, then the protocol
operation is denied. operation is denied.
11. If the requested protocol operation is the NETCONF <kill- 11. If the requested protocol operation is the NETCONF <kill-
session> or <delete-config>, then the protocol operation is session> or <delete-config>, then the protocol operation is
denied. denied.
12. If the "exec-default" leaf is set to "permit", then permit the 12. If the "exec-default" leaf is set to "permit", then permit the
protocol operation, otherwise deny the request. protocol operation; otherwise, deny the request.
If the user is not authorized to invoke the protocol operation then If the user is not authorized to invoke the protocol operation, then
an <rpc-error> is generated with the following information: an <rpc-error> is generated with the following information:
error-tag: access-denied error-tag: access-denied
error-path: Identifies the requested protocol operation. For error-path: Identifies the requested protocol operation. The
example: following example represents the <edit-config> protocol operation
in the NETCONF base namespace:
<error-path <error-path
xmlns:nc="urn:ietf:params:xml:ns:netconf:base:1.0"> xmlns:nc="urn:ietf:params:xml:ns:netconf:base:1.0">
/nc:rpc/nc:edit-config /nc:rpc/nc:edit-config
</error-path> </error-path>
represents the <edit-config> protocol operation in the NETCONF
base namespace.
If a datastore is accessed, either directly or as a side effect of If a datastore is accessed, either directly or as a side effect of
the protocol operation, then the server MUST intercept the access the protocol operation, then the server MUST intercept the access
operation and make sure the user is authorized to perform the operation and make sure the user is authorized to perform the
requested access operation on the specified data, as defined in requested access operation on the specified data, as defined in
Section 3.4.5. Section 3.4.5.
3.4.5. Data Node Access Validation 3.4.5. Data Node Access Validation
If a data node within a datastore is accessed, then the server MUST If a data node within a datastore is accessed, then the server MUST
ensure that the user is authorized to perform the requested read, ensure that the user is authorized to perform the requested "read",
create, update, or delete access operation on the specified data "create", "update", or "delete" access operation on the specified
node. data node.
The data node access request is authorized by following these steps: The data node access request is authorized by following these steps:
1. If the "enable-nacm" leaf is set to "false", then the access 1. If the "enable-nacm" leaf is set to "false", then the access
operation is permitted. operation is permitted.
2. If the requesting session is identified as a "recovery session", 2. If the requesting session is identified as a recovery session,
then the access operation is permitted. then the access operation is permitted.
3. Check all the "group" entries for ones that contain a "user- 3. Check all the "group" entries for ones that contain a "user-
name" entry that equals the user name for the session making the name" entry that equals the username for the session making the
request. If the the "enable-external-groups" leaf is "true", request. If the "enable-external-groups" leaf is "true", add to
add to these groups the set of groups provided by the transport these groups the set of groups provided by the transport layer.
layer.
4. If no groups are found, continue with step 9. 4. If no groups are found, continue with step 9.
5. Process all rule-list entries, in the order they appear in the 5. Process all rule-list entries, in the order they appear in the
configuration. If a rule-list's "group" leaf-list does not configuration. If a rule-list's "group" leaf-list does not
match any of the user's groups, proceed to the next rule-list match any of the user's groups, proceed to the next rule-list
entry. entry.
6. For each rule-list entry found, process all rules, in order, 6. For each rule-list entry found, process all rules, in order,
until a rule that matches the requested access operation is until a rule that matches the requested access operation is
found. A rule matches if all of the following criteria are met: found. A rule matches if all of the following criteria are met:
* The rule's "module-name" leaf is "*", or equals the name of * The rule's "module-name" leaf is "*" or equals the name of
the YANG module where the requested data node is defined. the YANG module where the requested data node is defined.
* The rule does not have a "rule-type" defined, or the "rule- * The rule does not have a "rule-type" defined or the "rule-
type" is "data-node" and the "path" matches the requested type" is "data-node" and the "path" matches the requested
data node. data node.
* For a read access operation, the rule's "access-operations" * For a "read" access operation, the rule's "access-operations"
leaf has the "read" bit set, or has the special value "*". leaf has the "read" bit set or has the special value "*".
* For a create access operation, the rule's "access-operations" * For a "create" access operation, the rule's "access-
leaf has the "create" bit set, or has the special value "*". operations" leaf has the "create" bit set or has the special
value "*".
* For a delete access operation, the rule's "access-operations" * For a "delete" access operation, the rule's "access-
leaf has the "delete" bit set, or has the special value "*". operations" leaf has the "delete" bit set or has the special
value "*".
* For an update access operation, the rule's "access- * For an "update" access operation, the rule's "access-
operations" leaf has the "update" bit set, or has the special operations" leaf has the "update" bit set or has the special
value "*". value "*".
7. If a matching rule is found, then the "action" leaf is checked. 7. If a matching rule is found, then the "action" leaf is checked.
If it is equal to "permit", then the data node access is If it is equal to "permit", then the data node access is
permitted, otherwise it is denied. For a read access operation, permitted; otherwise, it is denied. For a "read" access
"denied" means that the requested data is not returned in the operation, "denied" means that the requested data is not
reply. returned in the reply.
8. Otherwise, no matching rule was found in any rule-list entry. 8. At this point, no matching rule was found in any rule-list
entry.
9. For a read access operation, if the requested data node is 9. For a "read" access operation, if the requested data node is
defined in a YANG module advertised in the server capabilities, defined in a YANG module advertised in the server capabilities
and the data definition statement contains a "nacm:default-deny- and the data definition statement contains a "nacm:default-deny-
all" statement, then the requested data node is not included in all" statement, then the requested data node is not included in
the reply. the reply.
10. For a write access operation, if the requested data node is 10. For a "write" access operation, if the requested data node is
defined in a YANG module advertised in the server capabilities, defined in a YANG module advertised in the server capabilities
and the data definition statement contains a "nacm:default-deny- and the data definition statement contains a "nacm:default-deny-
write" or a "nacm:default-deny-all" statement, then the data write" or a "nacm:default-deny-all" statement, then the data
node access request is denied. node access request is denied.
11. For a read access operation, if the "read-default" leaf is set 11. For a "read" access operation, if the "read-default" leaf is set
to "permit", then include the requested data node in the reply, to "permit", then include the requested data node in the reply;
otherwise do not include the requested data node in the reply. otherwise, do not include the requested data node in the reply.
12. For a write access operation, if the "write-default" leaf is set 12. For a "write" access operation, if the "write-default" leaf is
to "permit", then permit the data node access request, otherwise set to "permit", then permit the data node access request;
deny the request. otherwise, deny the request.
3.4.6. Outgoing <notification> Authorization 3.4.6. Outgoing <notification> Authorization
Configuration of access control rules specifically for descendant Configuration of access control rules specifically for descendant
nodes of the notification event type element are outside the scope of nodes of the notification event type element are outside the scope of
this document. If the user is authorized to receive the notification this document. If the user is authorized to receive the notification
event type, then it is also authorized to receive any data it event type, then it is also authorized to receive any data it
contains. contains.
The following figure shows the conceptual message processing model The following figure shows the conceptual message processing model
skipping to change at page 26, line 36 skipping to change at page 24, line 36
+------------------------+ +------------------------+
| server instrumentation | | server instrumentation |
+------------------------+ +------------------------+
| ^ | ^
V | V |
+----------------------+ +----------------------+
| configuration | | configuration |
| datastore | | datastore |
+----------------------+ +----------------------+
Figure 4 Figure 4
The generation of a notification for a specific subscription The generation of a notification for a specific subscription
[RFC5277] is authorized by following these steps: [RFC5277] is authorized by following these steps:
1. If the "enable-nacm" leaf is set to "false", then the 1. If the "enable-nacm" leaf is set to "false", then the
notification is permitted. notification is permitted.
2. If the session is identified as a "recovery session", then the 2. If the session is identified as a recovery session, then the
notification is permitted. notification is permitted.
3. If the notification is the NETCONF <replayComplete> or 3. If the notification is the NETCONF <replayComplete> or
<notificationComplete> event type [RFC5277], then the <notificationComplete> event type [RFC5277], then the
notification is permitted. notification is permitted.
4. Check all the "group" entries for ones that contain a "user- 4. Check all the "group" entries for ones that contain a "user-
name" entry that equals the user name for the session making the name" entry that equals the username for the session making the
request. If the "enable-external-groups" leaf is "true", add to request. If the "enable-external-groups" leaf is "true", add to
these groups the set of groups provided by the transport layer. these groups the set of groups provided by the transport layer.
5. If no groups are found, continue with step 10. 5. If no groups are found, continue with step 10.
6. Process all rule-list entries, in the order they appear in the 6. Process all rule-list entries, in the order they appear in the
configuration. If a rule-list's "group" leaf-list does not configuration. If a rule-list's "group" leaf-list does not
match any of the user's groups, proceed to the next rule-list match any of the user's groups, proceed to the next rule-list
entry. entry.
7. For each rule-list entry found, process all rules, in order, 7. For each rule-list entry found, process all rules, in order,
until a rule that matches the requested access operation is until a rule that matches the requested access operation is
found. A rule matches if all of the following criteria are met: found. A rule matches if all of the following criteria are met:
* The rule's "module-name" leaf is "*", or equals the name of * The rule's "module-name" leaf is "*" or equals the name of
the YANG module where the notification is defined. the YANG module where the notification is defined.
* The rule does not have a "rule-type" defined, or the "rule- * The rule does not have a "rule-type" defined or the "rule-
type" is "notification" and the "notification-name" is "*", type" is "notification" and the "notification-name" is "*"
equals the name of the notification. and equals the name of the notification.
* The rule's "access-operations" leaf has the "read" bit set, * The rule's "access-operations" leaf has the "read" bit set or
or has the special value "*". has the special value "*".
8. If a matching rule is found, then the "action" leaf is checked. 8. If a matching rule is found, then the "action" leaf is checked.
If it is equal to "permit", then permit the notification, If it is equal to "permit", then permit the notification;
otherwise drop the notification for the associated subscription. otherwise, drop the notification for the associated
subscription.
9. Otherwise, no matching rule was found in any rule-list entry. 9. Otherwise, no matching rule was found in any rule-list entry.
10. If the requested notification is defined in a YANG module 10. If the requested notification is defined in a YANG module
advertised in the server capabilities, and the "notification" advertised in the server capabilities and the "notification"
statement contains a "nacm:default-deny-all" statement, then the statement contains a "nacm:default-deny-all" statement, then the
notification is dropped for the associated subscription. notification is dropped for the associated subscription.
11. If the "read-default" leaf is set to "permit", then permit the 11. If the "read-default" leaf is set to "permit", then permit the
notification, otherwise drop the notification for the associated notification; otherwise, drop the notification for the
subscription. associated subscription.
3.5. Data Model Definitions 3.5. Data Model Definitions
3.5.1. Data Organization 3.5.1. Data Organization
The following diagram highlights the contents and structure of the The following diagram highlights the contents and structure of the
NACM YANG module. NACM YANG module.
+--rw nacm +--rw nacm
+--rw enable-nacm? boolean +--rw enable-nacm? boolean
skipping to change at page 28, line 42 skipping to change at page 27, line 5
+--rw action action-type +--rw action action-type
+--rw comment? string +--rw comment? string
3.5.2. YANG Module 3.5.2. YANG Module
The following YANG module specifies the normative NETCONF content The following YANG module specifies the normative NETCONF content
that MUST by supported by the server. that MUST by supported by the server.
The "ietf-netconf-acm" YANG module imports typedefs from [RFC6021]. The "ietf-netconf-acm" YANG module imports typedefs from [RFC6021].
// RFC Ed.: please update the date to the date of publication <CODE BEGINS> file "ietf-netconf-acm@2012-02-22.yang"
<CODE BEGINS> file="ietf-netconf-acm@2011-12-23.yang"
module ietf-netconf-acm { module ietf-netconf-acm {
namespace "urn:ietf:params:xml:ns:yang:ietf-netconf-acm"; namespace "urn:ietf:params:xml:ns:yang:ietf-netconf-acm";
prefix "nacm"; prefix "nacm";
import ietf-yang-types { import ietf-yang-types {
prefix yang; prefix yang;
} }
skipping to change at page 29, line 21 skipping to change at page 27, line 31
"WG Web: <http://tools.ietf.org/wg/netconf/> "WG Web: <http://tools.ietf.org/wg/netconf/>
WG List: <mailto:netconf@ietf.org> WG List: <mailto:netconf@ietf.org>
WG Chair: Mehmet Ersue WG Chair: Mehmet Ersue
<mailto:mehmet.ersue@nsn.com> <mailto:mehmet.ersue@nsn.com>
WG Chair: Bert Wijnen WG Chair: Bert Wijnen
<mailto:bertietf@bwijnen.net> <mailto:bertietf@bwijnen.net>
Editor: Andy Bierman Editor: Andy Bierman
<mailto:andy@netconfcentral.org> <mailto:andy@yumaworks.com>
Editor: Martin Bjorklund Editor: Martin Bjorklund
<mailto:mbj@tail-f.com>"; <mailto:mbj@tail-f.com>";
description description
"NETCONF Access Control Model. "NETCONF Access Control Model.
Copyright (c) 2011 IETF Trust and the persons identified as Copyright (c) 2012 IETF Trust and the persons identified as
authors of the code. All rights reserved. authors of the code. All rights reserved.
Redistribution and use in source and binary forms, with or Redistribution and use in source and binary forms, with or
without modification, is permitted pursuant to, and subject without modification, is permitted pursuant to, and subject
to the license terms contained in, the Simplified BSD to the license terms contained in, the Simplified BSD
License set forth in Section 4.c of the IETF Trust's License set forth in Section 4.c of the IETF Trust's
Legal Provisions Relating to IETF Documents Legal Provisions Relating to IETF Documents
(http://trustee.ietf.org/license-info). (http://trustee.ietf.org/license-info).
This version of this YANG module is part of RFC XXXX; see This version of this YANG module is part of RFC 6536; see
the RFC itself for full legal notices."; the RFC itself for full legal notices.";
// RFC Ed.: replace XXXX with actual RFC number and
// remove this note
// RFC Ed.: remove this note revision "2012-02-22" {
// Note: extracted from draft-ietf-netconf-access-control-07.txt
// RFC Ed.: please update the date to the date of publication
revision "2011-12-23" {
description description
"Initial version"; "Initial version";
reference reference
"RFC XXXX: Network Configuration Protocol "RFC 6536: Network Configuration Protocol (NETCONF)
Access Control Model"; Access Control Model";
} }
/* /*
* Extension statements * Extension statements
*/ */
extension default-deny-write { extension default-deny-write {
description description
"Used to indicate that the data model node "Used to indicate that the data model node
skipping to change at page 31, line 5 skipping to change at page 29, line 7
/* /*
* Derived types * Derived types
*/ */
typedef user-name-type { typedef user-name-type {
type string { type string {
length "1..max"; length "1..max";
} }
description description
"General Purpose User Name string."; "General Purpose Username string.";
} }
typedef matchall-string-type { typedef matchall-string-type {
type string { type string {
pattern "\*"; pattern "\*";
} }
description description
"The string containing a single asterisk '*' is used "The string containing a single asterisk '*' is used
to conceptually represent all possible values to conceptually represent all possible values
for the particular leaf using this data type."; for the particular leaf using this data type.";
skipping to change at page 32, line 42 skipping to change at page 30, line 43
A node-instance-identifier value is an A node-instance-identifier value is an
unrestricted YANG instance-identifier expression. unrestricted YANG instance-identifier expression.
All the same rules as an instance-identifier apply All the same rules as an instance-identifier apply
except predicates for keys are optional. If a key except predicates for keys are optional. If a key
predicate is missing, then the node-instance-identifier predicate is missing, then the node-instance-identifier
represents all possible server instances for that key. represents all possible server instances for that key.
This XPath expression is evaluated in the following context: This XPath expression is evaluated in the following context:
o The set of namespace declarations are those in scope on o The set of namespace declarations are those in scope on
the leaf element where this type is used. the leaf element where this type is used.
o The set of variable bindings contains one variable, o The set of variable bindings contains one variable,
'USER', which contains the name of user of the current 'USER', which contains the name of the user of the current
session. session.
o The function library is the core function library, but o The function library is the core function library, but
note that due to the syntax restrictions of an note that due to the syntax restrictions of an
instance-identifier, no functions are allowed. instance-identifier, no functions are allowed.
o The context node is the root node in the data tree."; o The context node is the root node in the data tree.";
} }
/* /*
* Data definition statements * Data definition statements
*/ */
container nacm { container nacm {
nacm:default-deny-all; nacm:default-deny-all;
description description
"Parameters for NETCONF Access Control Model."; "Parameters for NETCONF Access Control Model.";
leaf enable-nacm { leaf enable-nacm {
type boolean; type boolean;
default true; default true;
description description
"Enable or disable all NETCONF access control "Enables or disables all NETCONF access control
enforcement. If 'true', then enforcement enforcement. If 'true', then enforcement
is enabled. If 'false', then enforcement is enabled. If 'false', then enforcement
is disabled."; is disabled.";
} }
leaf read-default { leaf read-default {
type action-type; type action-type;
default "permit"; default "permit";
description description
"Controls whether read access is granted if "Controls whether read access is granted if
skipping to change at page 34, line 20 skipping to change at page 32, line 23
NACM groups. If this leaf has the value 'false', any group NACM groups. If this leaf has the value 'false', any group
names reported by the transport layer are ignored by the names reported by the transport layer are ignored by the
server."; server.";
} }
leaf denied-operations { leaf denied-operations {
type yang:zero-based-counter32; type yang:zero-based-counter32;
config false; config false;
mandatory true; mandatory true;
description description
"Number of times a protocol operation request was denied "Number of times since the server last restarted that a
since the server last restarted."; protocol operation request was denied.";
} }
leaf denied-data-writes { leaf denied-data-writes {
type yang:zero-based-counter32; type yang:zero-based-counter32;
config false; config false;
mandatory true; mandatory true;
description description
"Number of times a protocol operation request to alter "Number of times since the server last restarted that a
a configuration datastore was denied, since the protocol operation request to alter
server last restarted."; a configuration datastore was denied.";
} }
leaf denied-notifications { leaf denied-notifications {
type yang:zero-based-counter32; type yang:zero-based-counter32;
config false; config false;
mandatory true; mandatory true;
description description
"Number of times a notification was dropped "Number of times since the server last restarted that
for a subscription because access to a notification was dropped for a subscription because
the event type was denied, since the server access to the event type was denied.";
last restarted.";
} }
container groups { container groups {
description description
"NETCONF Access Control Groups."; "NETCONF Access Control Groups.";
list group { list group {
key name; key name;
description description
"One NACM Group Entry. This list will only contain "One NACM Group Entry. This list will only contain
configured entries, not any entries learned from configured entries, not any entries learned from
any transport protocols."; any transport protocols.";
leaf name { leaf name {
type group-name-type; type group-name-type;
description description
"Group name associated with this entry."; "Group name associated with this entry.";
} }
skipping to change at page 35, line 18 skipping to change at page 33, line 20
leaf name { leaf name {
type group-name-type; type group-name-type;
description description
"Group name associated with this entry."; "Group name associated with this entry.";
} }
leaf-list user-name { leaf-list user-name {
type user-name-type; type user-name-type;
description description
"Each entry identifies the user name of "Each entry identifies the username of
a member of the group associated with a member of the group associated with
this entry."; this entry.";
} }
} }
} }
list rule-list { list rule-list {
key "name"; key "name";
ordered-by user; ordered-by user;
description description
skipping to change at page 35, line 50 skipping to change at page 34, line 4
type matchall-string-type; type matchall-string-type;
type group-name-type; type group-name-type;
} }
description description
"List of administrative groups that will be "List of administrative groups that will be
assigned the associated access rights assigned the associated access rights
defined by the 'rule' list. defined by the 'rule' list.
The string '*' indicates that all groups apply to the The string '*' indicates that all groups apply to the
entry."; entry.";
} }
list rule { list rule {
key "name"; key "name";
ordered-by user; ordered-by user;
description description
"One access control rule. "One access control rule.
Rules are processed in user-defined order until a match is Rules are processed in user-defined order until a match is
found. A rule matches if 'module-name', 'rule-type', and found. A rule matches if 'module-name', 'rule-type', and
'access-operations' matches the request. If a rule 'access-operations' match the request. If a rule
matches, the 'action' leaf determines if access is granted matches, the 'action' leaf determines if access is granted
or not."; or not.";
leaf name { leaf name {
type string { type string {
length "1..max"; length "1..max";
} }
description description
"Arbitrary name assigned to the rule."; "Arbitrary name assigned to the rule.";
} }
leaf module-name { leaf module-name {
type union { type union {
type matchall-string-type; type matchall-string-type;
type string; type string;
} }
default "*"; default "*";
description description
"Name of the module associated with this rule. "Name of the module associated with this rule.
This leaf matches if it has the value '*', or if the This leaf matches if it has the value '*' or if the
object being accessed is defined in the module with the object being accessed is defined in the module with the
specified module name."; specified module name.";
} }
choice rule-type { choice rule-type {
description description
"This choice matches if all leafs present in the rule "This choice matches if all leafs present in the rule
matches the request. If no leafs are present, the match the request. If no leafs are present, the
choice matches all requests."; choice matches all requests.";
case protocol-operation { case protocol-operation {
leaf rpc-name { leaf rpc-name {
type union { type union {
type matchall-string-type; type matchall-string-type;
type string; type string;
} }
description description
"This leaf matches if it has the value '*', or if "This leaf matches if it has the value '*' or if
its value equals the requested protocol operation its value equals the requested protocol operation
name."; name.";
} }
} }
case notification { case notification {
leaf notification-name { leaf notification-name {
type union { type union {
type matchall-string-type; type matchall-string-type;
type string; type string;
} }
description description
"This leaf matches if it has the value '*', or if its "This leaf matches if it has the value '*' or if its
value equals the requested notification name."; value equals the requested notification name.";
} }
} }
case data-node { case data-node {
leaf path { leaf path {
type node-instance-identifier; type node-instance-identifier;
mandatory true; mandatory true;
description description
"Data Node Instance Identifier associated with the "Data Node Instance Identifier associated with the
data node controlled by this rule. data node controlled by this rule.
Configuration data or state data instance Configuration data or state data instance
identifiers start with a top-level data node. A identifiers start with a top-level data node. A
complete instance identifier is required for this complete instance identifier is required for this
type of path value. type of path value.
The special value '/' refers to all possible data The special value '/' refers to all possible
store contents."; datastore contents.";
} }
} }
} }
leaf access-operations { leaf access-operations {
type union { type union {
type matchall-string-type; type matchall-string-type;
type access-operations-type; type access-operations-type;
} }
default "*"; default "*";
description description
"Access operations associated with this rule. "Access operations associated with this rule.
This leaf matches if it has the value '*', or if the This leaf matches if it has the value '*' or if the
bit corresponding to the requested operation is set."; bit corresponding to the requested operation is set.";
} }
leaf action { leaf action {
type action-type; type action-type;
mandatory true; mandatory true;
description description
"The access control action associated with the "The access control action associated with the
rule. If a rule is determined to match a rule. If a rule is determined to match a
particular request, then this object is used particular request, then this object is used
skipping to change at page 38, line 24 skipping to change at page 36, line 26
description description
"A textual description of the access rule."; "A textual description of the access rule.";
} }
} }
} }
} }
} }
<CODE ENDS> <CODE ENDS>
Figure 5
3.6. IANA Considerations 3.6. IANA Considerations
There are two actions that are requested of IANA: This document This document registers one URI in "The IETF XML Registry".
registers one URI in "The IETF XML Registry". Following the format Following the format in [RFC3688], the following has been registered.
in [RFC3688], the following has been registered.
URI: urn:ietf:params:xml:ns:yang:ietf-netconf-acm URI: urn:ietf:params:xml:ns:yang:ietf-netconf-acm
Registrant Contact: The IESG. Registrant Contact: The IESG.
XML: N/A, the requested URI is an XML namespace. XML: N/A, the requested URI is an XML namespace.
This document registers one module in the "YANG Module Names" This document registers one module in the "YANG Module Names"
registry. Following the format in [RFC6020], the following has been registry. Following the format in [RFC6020], the following has been
registered. registered.
name: ietf-netconf-acm Name: ietf-netconf-acm
namespace: urn:ietf:params:xml:ns:yang:ietf-netconf-acm Namespace: urn:ietf:params:xml:ns:yang:ietf-netconf-acm
prefix: nacm Prefix: nacm
reference: RFC XXXX reference: RFC 6536
// RFC Ed.: Replace XXX with actual RFC number
// and remove this note
3.7. Security Considerations 3.7. Security Considerations
This entire document discusses access control requirements and This entire document discusses access control requirements and
mechanisms for restricting NETCONF protocol behavior within a given mechanisms for restricting NETCONF protocol behavior within a given
session. session.
This section highlights the issues for an administrator to consider This section highlights the issues for an administrator to consider
when configuring a NETCONF server with NACM. when configuring a NETCONF server with NACM.
3.7.1. NACM Configuration and Monitoring Considerations 3.7.1. NACM Configuration and Monitoring Considerations
Configuration of the access control system is highly sensitive to Configuration of the access control system is highly sensitive to
system security. A server may choose not to allow any user system security. A server may choose not to allow any user
configuration to some portions of it, such as the global security configuration to some portions of it, such as the global security
level, or the groups which allowed access to system resources. level or the groups that allowed access to system resources.
By default, NACM enforcement is enabled. By default, "read" access By default, NACM enforcement is enabled. By default, "read" access
to all datastore contents is enabled, (unless "nacm:default-deny-all" to all datastore contents is enabled (unless "nacm:default-deny-all"
is specified for the data definition) and "exec" access is enabled is specified for the data definition), and "exec" access is enabled
for safe protocol operations. An administrator needs to ensure that for safe protocol operations. An administrator needs to ensure that
NACM is enabled, and also decide if the default access parameters are NACM is enabled and also decide if the default access parameters are
set appropriately. Make sure the following data nodes are properly set appropriately. Make sure the following data nodes are properly
configured: configured:
o /nacm/enable-nacm (default "true") o /nacm/enable-nacm (default "true")
o /nacm/read-default (default "permit") o /nacm/read-default (default "permit")
o /nacm/write-default (default "deny") o /nacm/write-default (default "deny")
o /nacm/exec-default (default "permit") o /nacm/exec-default (default "permit")
skipping to change at page 39, line 49 skipping to change at page 37, line 40
If write access is allowed for configuration of access control rules, If write access is allowed for configuration of access control rules,
then care needs to be taken not to disrupt the access control then care needs to be taken not to disrupt the access control
enforcement. For example, if the NACM access control rules are enforcement. For example, if the NACM access control rules are
edited directly within the running configuration datastore (i.e., edited directly within the running configuration datastore (i.e.,
:writable-running capability is supported and used), then care needs :writable-running capability is supported and used), then care needs
to be taken not to allow unintended access while the edits are being to be taken not to allow unintended access while the edits are being
done. done.
An administrator needs to make sure that the translation from a An administrator needs to make sure that the translation from a
transport or implementation dependant user identity to a NACM user transport- or implementation-dependent user identity to a NACM
name is unique and correct. This requirement is specified in detail username is unique and correct. This requirement is specified in
in section 2.2 of [RFC6241]. detail in Section 2.2 of [RFC6241].
An administrator needs to be aware that the YANG data structures An administrator needs to be aware that the YANG data structures
representing access control rules (/nacm/rule-list and /nacm/ representing access control rules (/nacm/rule-list and /nacm/
rule-list/rule) are ordered by the client. The server will evaluate rule-list/rule) are ordered by the client. The server will evaluate
the access control rules according to their relative conceptual order the access control rules according to their relative conceptual order
within the running datastore configuration. within the running datastore configuration.
Note that the /nacm/groups data structure contains the administrative Note that the /nacm/groups data structure contains the administrative
group names used by the server. These group names may be configured group names used by the server. These group names may be configured
locally and/or provided through an external protocol, such as RADIUS locally and/or provided through an external protocol, such as RADIUS
[RFC2865] [RFC5607]. [RFC2865][RFC5607].
An administrator needs to be aware of the security properties of any An administrator needs to be aware of the security properties of any
external protocol used by the NETCONF transport layer to determine external protocol used by the NETCONF transport layer to determine
group names. For example, if this protocol does not protect against group names. For example, if this protocol does not protect against
man-in-the-middle attacks, an attacker might be able to inject group man-in-the-middle attacks, an attacker might be able to inject group
names that are configured in NACM, so that a user gets more names that are configured in NACM, so that a user gets more
permissions than it should. In such cases, the administrator may permissions than it should. In such cases, the administrator may
wish to disable the usage of such group names, by setting /nacm/ wish to disable the usage of such group names, by setting /nacm/
enable-external-groups to "false". enable-external-groups to "false".
An administrator needs to restrict read access to the following An administrator needs to restrict read access to the following
objects within this data model, which reveal access control objects within this data model, as they reveal access control
configuration which could be considered sensitive. configuration that could be considered sensitive.
o /nacm/enable-nacm o /nacm/enable-nacm
o /nacm/read-default o /nacm/read-default
o /nacm/write-default o /nacm/write-default
o /nacm/exec-default o /nacm/exec-default
o /nacm/enable-external-groups o /nacm/enable-external-groups
skipping to change at page 41, line 9 skipping to change at page 38, line 52
is protected from such side effects. is protected from such side effects.
It is possible for a session with some write access (e.g., allowed to It is possible for a session with some write access (e.g., allowed to
invoke <edit-config>), but without any access to a particular invoke <edit-config>), but without any access to a particular
datastore subtree containing sensitive data, to determine the datastore subtree containing sensitive data, to determine the
presence or non-presence of that data. This can be done by presence or non-presence of that data. This can be done by
repeatedly issuing some sort of edit request (create, update, or repeatedly issuing some sort of edit request (create, update, or
delete) and possibly receiving "access-denied" errors in response. delete) and possibly receiving "access-denied" errors in response.
These "fishing" attacks can identify the presence or non-presence of These "fishing" attacks can identify the presence or non-presence of
specific sensitive data even without the "error-path" field being specific sensitive data even without the "error-path" field being
present within the "rpc-error" response. present within the <rpc-error> response.
It may be possible for the set of NETCONF capabilities on the server It may be possible for the set of NETCONF capabilities on the server
to change over time. If so, then there is a risk that new protocol to change over time. If so, then there is a risk that new protocol
operations, notifications, and/or datastore content have been added operations, notifications, and/or datastore content have been added
to the device. An administrator needs to be sure the access control to the device. An administrator needs to be sure the access control
rules are correct for the new content in this case. Mechanisms to rules are correct for the new content in this case. Mechanisms to
detect NETCONF capability changes on a specific device are outside detect NETCONF capability changes on a specific device are outside
the scope of this document. the scope of this document.
It is possible that the data model definition itself (e.g., YANG It is possible that the data model definition itself (e.g., YANG
when-stmt) will help an unauthorized session determine the presence when-stmt) will help an unauthorized session determine the presence
or even value of sensitive data nodes by examining the presence and or even value of sensitive data nodes by examining the presence and
values of different data nodes. values of different data nodes.
There is a risk that non-standard protocol operations, or even the There is a risk that non-standard protocol operations, or even the
standard <get> protocol operation, may return data which "aliases" or standard <get> protocol operation, may return data that "aliases" or
"copies" sensitive data from a different data object. There may "copies" sensitive data from a different data object. There may
simply be multiple data model definitions which expose or even simply be multiple data model definitions that expose or even
configure the same underlying system instrumentation. configure the same underlying system instrumentation.
A data model may contain external keys (e.g., YANG leafref), which A data model may contain external keys (e.g., YANG leafref), which
expose values from a different data structure. An administrator expose values from a different data structure. An administrator
needs to be aware of sensitive data models which contain leafref needs to be aware of sensitive data models that contain leafref
nodes. This entails finding all the leafref objects that "point" at nodes. This entails finding all the leafref objects that "point" at
the sensitive data (i.e., "path-stmt" values) that implicitly or the sensitive data (i.e., "path-stmt" values) that implicitly or
explicitly include the sensitive data node. explicitly include the sensitive data node.
It is beyond the scope of this document to define access control It is beyond the scope of this document to define access control
enforcement procedures for underlying device instrumentation that may enforcement procedures for underlying device instrumentation that may
exist to support the NETCONF server operation. An administrator can exist to support the NETCONF server operation. An administrator can
identify each protocol operation that the server provides, and decide identify each protocol operation that the server provides and decide
if it needs any access control applied to it. if it needs any access control applied to it.
This document incorporates the optional use of a "recovery session" This document incorporates the optional use of a recovery session
mechanism, which can be used to bypass access control enforcement in mechanism, which can be used to bypass access control enforcement in
emergencies, such as NACM configuration errors which disable all emergencies, such as NACM configuration errors that disable all
access to the server. The configuration and identification of such a access to the server. The configuration and identification of such a
recovery session mechanism are implementation-specific and outside recovery session mechanism are implementation-specific and outside
the scope of this document. An administrator needs to be aware of the scope of this document. An administrator needs to be aware of
any "recovery session" mechanisms available on the device, and make any recovery session mechanisms available on the device and make sure
sure they are used appropriately. they are used appropriately.
It is possible for a session to disrupt configuration management, It is possible for a session to disrupt configuration management,
even without any write access to the configuration, by locking the even without any write access to the configuration, by locking the
datastore. This may be done to insure all or part of the datastore. This may be done to ensure all or part of the
configuration remains stable while it is being retrieved, or it may configuration remains stable while it is being retrieved, or it may
be done as a "denial-of-service" attack. There is no way for the be done as a "denial-of-service" attack. There is no way for the
server to know the difference. An administrator may wish to restrict server to know the difference. An administrator may wish to restrict
"exec" access to the following protocol operations: "exec" access to the following protocol operations:
o <lock> o <lock>
o <unlock> o <unlock>
o <partial-lock> o <partial-lock>
skipping to change at page 42, line 31 skipping to change at page 40, line 23
3.7.3. Data Model Design Considerations 3.7.3. Data Model Design Considerations
Designers need to clearly identify any sensitive data, notifications, Designers need to clearly identify any sensitive data, notifications,
or protocol operations defined within a YANG module. For such or protocol operations defined within a YANG module. For such
definitions, a "nacm:default-deny-write" or "nacm:default-deny-all" definitions, a "nacm:default-deny-write" or "nacm:default-deny-all"
statement ought to be present, in addition to a clear description of statement ought to be present, in addition to a clear description of
the security risks. the security risks.
Protocol operations need to be properly documented by the data model Protocol operations need to be properly documented by the data model
designer, so it is clear to administrators what data nodes (if any) designer, so it is clear to administrators what data nodes (if any)
are affected by the protocol operation, and what information (if any) are affected by the protocol operation and what information (if any)
is returned in the <rpc-reply> message. is returned in the <rpc-reply> message.
Data models ought to be designed so that different access levels for Data models ought to be designed so that different access levels for
input parameters to protocol operations is not required. Use of input parameters to protocol operations are not required. Use of
generic protocol operations should be avoided, and separate protocol generic protocol operations should be avoided, and if different
operations defined instead, if different access levels are needed. access levels are needed, separate protocol operations should be
defined instead.
4. References 4. References
4.1. Normative References 4.1. Normative References
[RFC2119] Bradner, S., "Key words for use in RFCs to Indicate [RFC2119] Bradner, S., "Key words for use in RFCs to Indicate
Requirement Levels", BCP 14, RFC 2119, March 1997. Requirement Levels", BCP 14, RFC 2119, March 1997.
[RFC3688] Mealling, M., "The IETF XML Registry", BCP 81, RFC 3688, [RFC3688] Mealling, M., "The IETF XML Registry", BCP 81, RFC 3688,
January 2004. January 2004.
skipping to change at page 44, line 16 skipping to change at page 42, line 16
The following XML snippets are provided as examples only, to The following XML snippets are provided as examples only, to
demonstrate how NACM can be configured to perform some access control demonstrate how NACM can be configured to perform some access control
tasks. tasks.
A.1. <groups> Example A.1. <groups> Example
There needs to be at least one <group> entry in order for any of the There needs to be at least one <group> entry in order for any of the
access control rules to be useful. access control rules to be useful.
The following XML shows arbitrary groups, and is not intended to The following XML shows arbitrary groups and is not intended to
represent any particular use-case. represent any particular use case.
<nacm xmlns="urn:ietf:params:xml:ns:yang:ietf-netconf-acm"> <nacm xmlns="urn:ietf:params:xml:ns:yang:ietf-netconf-acm">
<groups> <groups>
<group> <group>
<name>admin</name> <name>admin</name>
<user-name>admin</user-name> <user-name>admin</user-name>
<user-name>andy</user-name> <user-name>andy</user-name>
</group> </group>
<group> <group>
skipping to change at page 44, line 41 skipping to change at page 42, line 41
</group> </group>
<group> <group>
<name>guest</name> <name>guest</name>
<user-name>guest</user-name> <user-name>guest</user-name>
<user-name>guest@example.com</user-name> <user-name>guest@example.com</user-name>
</group> </group>
</groups> </groups>
</nacm> </nacm>
This example shows 3 groups: This example shows three groups:
1. The "admin" group contains 2 users named "admin" and "andy". admin: The "admin" group contains two users named "admin" and
"andy".
2. The "limited" group contains 2 users named "wilma" and "bam-bam". limited: The "limited" group contains two users named "wilma" and
"bam-bam".
3. The "guest" group contains 2 users named "guest" and guest: The "guest" group contains two users named "guest" and
"guest@example.com". "guest@example.com".
A.2. Module Rule Example A.2. Module Rule Example
Module rules are used to control access to all the content defined in Module rules are used to control access to all the content defined in
a specific module. A module rule has the <module-name> leaf set, but a specific module. A module rule has the <module-name> leaf set, but
no case in the "rule-type" choice. no case in the "rule-type" choice.
<nacm xmlns="urn:ietf:params:xml:ns:yang:ietf-netconf-acm"> <nacm xmlns="urn:ietf:params:xml:ns:yang:ietf-netconf-acm">
<rule-list> <rule-list>
<name>guest-acl</name> <name>guest-acl</name>
<group>guest</group> <group>guest</group>
<rule> <rule>
<name>deny-ncm</name> <name>deny-ncm</name>
<module-name>ietf-netconf-monitoring</module-name> <module-name>ietf-netconf-monitoring</module-name>
<access-operations>*</access-operations> <access-operations>*</access-operations>
<action>deny</action> <action>deny</action>
<comment> <comment>
Do not allow guests any access to the netconf Do not allow guests any access to the NETCONF
monitoring information. monitoring information.
</comment> </comment>
</rule> </rule>
</rule-list> </rule-list>
<rule-list> <rule-list>
<name>limited-acl</name> <name>limited-acl</name>
<group>limited</group> <group>limited</group>
<rule> <rule>
<name>permit-ncm</name> <name>permit-ncm</name>
<module-name>ietf-netconf-monitoring</module-name> <module-name>ietf-netconf-monitoring</module-name>
<access-operations>read</access-operations> <access-operations>read</access-operations>
<action>permit</action> <action>permit</action>
<comment> <comment>
Allow read access to the netconf Allow read access to the NETCONF
monitoring information. monitoring information.
</comment> </comment>
</rule> </rule>
<rule> <rule>
<name>permit-exec</name> <name>permit-exec</name>
<module-name>*</module-name> <module-name>*</module-name>
<access-operations>exec</access-operations> <access-operations>exec</access-operations>
<action>permit</action> <action>permit</action>
<comment> <comment>
Allow invocation of the Allow invocation of the
skipping to change at page 46, line 24 skipping to change at page 44, line 21
<access-operations>*</access-operations> <access-operations>*</access-operations>
<action>permit</action> <action>permit</action>
<comment> <comment>
Allow the admin group complete access to all Allow the admin group complete access to all
operations and data. operations and data.
</comment> </comment>
</rule> </rule>
</rule-list> </rule-list>
</nacm> </nacm>
This example shows 4 module rules: This example shows four module rules:
deny-ncm: This rule prevents the "guest" group from reading any deny-ncm: This rule prevents the "guest" group from reading any
monitoring information in the "ietf-netconf-monitoring" YANG monitoring information in the "ietf-netconf-monitoring" YANG
module. module.
permit-ncm: This rule allows the "limited" group to read the "ietf- permit-ncm: This rule allows the "limited" group to read the "ietf-
netconf-monitoring" YANG module. netconf-monitoring" YANG module.
permit-exec: This rule allows the "limited" group to invoke any permit-exec: This rule allows the "limited" group to invoke any
protocol operation supported by the server. protocol operation supported by the server.
permit-all: This rule allows the "admin" group complete access to permit-all: This rule allows the "admin" group complete access to
all content in the server. No subsequent rule will match for the all content in the server. No subsequent rule will match for the
"admin" group, because of this module rule. "admin" group because of this module rule.
A.3. RPC Rule Example A.3. Protocol Operation Rule Example
RPC rules are used to control access to a specific protocol Protocol operation rules are used to control access to a specific
operation. protocol operation.
<nacm xmlns="urn:ietf:params:xml:ns:yang:ietf-netconf-acm"> <nacm xmlns="urn:ietf:params:xml:ns:yang:ietf-netconf-acm">
<rule-list> <rule-list>
<name>guest-limited-acl</name> <name>guest-limited-acl</name>
<group>limited</group> <group>limited</group>
<group>guest</group> <group>guest</group>
<rule> <rule>
<name>deny-kill-session</name> <name>deny-kill-session</name>
<module-name>ietf-netconf</module-name> <module-name>ietf-netconf</module-name>
skipping to change at page 48, line 4 skipping to change at page 45, line 41
<rpc-name>edit-config</rpc-name> <rpc-name>edit-config</rpc-name>
<access-operations>exec</access-operations> <access-operations>exec</access-operations>
<action>permit</action> <action>permit</action>
<comment> <comment>
Allow the limited group to edit the configuration. Allow the limited group to edit the configuration.
</comment> </comment>
</rule> </rule>
</rule-list> </rule-list>
</nacm> </nacm>
This example shows 3 protocol operation rules:
This example shows three protocol operation rules:
deny-kill-session: This rule prevents the "limited" or "guest" deny-kill-session: This rule prevents the "limited" or "guest"
groups from invoking the NETCONF <kill-session> protocol groups from invoking the NETCONF <kill-session> protocol
operation. operation.
deny-delete-config: This rule prevents the "limited" or "guest" deny-delete-config: This rule prevents the "limited" or "guest"
groups from invoking the NETCONF <delete-config> protocol groups from invoking the NETCONF <delete-config> protocol
operation. operation.
permit-edit-config: This rule allows the "limited" group to invoke permit-edit-config: This rule allows the "limited" group to invoke
the NETCONF <edit-config> protocol operation. This rule will have the NETCONF <edit-config> protocol operation. This rule will have
no real effect unless the "exec-default" leaf is set to "deny". no real effect unless the "exec-default" leaf is set to "deny".
A.4. Data Rule Example A.4. Data Node Rule Example
Data rules are used to control access to specific (config and non- Data node rules are used to control access to specific (config and
config) data nodes within the NETCONF content provided by the server. non-config) data nodes within the NETCONF content provided by the
server.
<nacm xmlns="urn:ietf:params:xml:ns:yang:ietf-netconf-acm"> <nacm xmlns="urn:ietf:params:xml:ns:yang:ietf-netconf-acm">
<rule-list> <rule-list>
<name>guest-acl</name> <name>guest-acl</name>
<group>guest</group> <group>guest</group>
<rule> <rule>
<name>deny-nacm</name> <name>deny-nacm</name>
<path xmlns:n="urn:ietf:params:xml:ns:yang:ietf-netconf-acm"> <path xmlns:n="urn:ietf:params:xml:ns:yang:ietf-netconf-acm">
/n:nacm /n:nacm
skipping to change at page 49, line 9 skipping to change at page 46, line 48
<name>permit-acme-config</name> <name>permit-acme-config</name>
<path xmlns:acme="http://example.com/ns/netconf"> <path xmlns:acme="http://example.com/ns/netconf">
/acme:acme-netconf/acme:config-parameters /acme:acme-netconf/acme:config-parameters
</path> </path>
<access-operations> <access-operations>
read create update delete read create update delete
</access-operations> </access-operations>
<action>permit</action> <action>permit</action>
<comment> <comment>
Allow the limited group complete access to the acme Allow the limited group complete access to the acme
netconf configuration parameters. Showing long form NETCONF configuration parameters. Showing long form
of 'access-operations' instead of shorthand. of 'access-operations' instead of shorthand.
</comment> </comment>
</rule> </rule>
</rule-list> </rule-list>
<rule-list> <rule-list>
<name>guest-limited-acl</name> <name>guest-limited-acl</name>
<group>guest</group> <group>guest</group>
<group>limited</group> <group>limited</group>
<rule> <rule>
<name>permit-dummy-interface</name> <name>permit-dummy-interface</name>
<path xmlns:acme="http://example.com/ns/itf"> <path xmlns:acme="http://example.com/ns/itf">
/acme:interfaces/acme:interface[acme:name='dummy'] /acme:interfaces/acme:interface[acme:name='dummy']
</path> </path>
skipping to change at page 50, line 4 skipping to change at page 47, line 39
/acme:interfaces/acme:interface /acme:interfaces/acme:interface
</path> </path>
<access-operations>*</access-operations> <access-operations>*</access-operations>
<action>permit</action> <action>permit</action>
<comment> <comment>
Allow admin full access to all acme interfaces. Allow admin full access to all acme interfaces.
</comment> </comment>
</rule> </rule>
</rule-list> </rule-list>
</nacm> </nacm>
This example shows 4 data rules:
This example shows four data node rules:
deny-nacm: This rule denies the "guest" group any access to the deny-nacm: This rule denies the "guest" group any access to the
<nacm> subtree. Note that the default namespace is only <nacm> subtree. Note that the default namespace is only
applicable because this subtree is defined in the same namespace applicable because this subtree is defined in the same namespace
as the <data-rule> element. as the <data-rule> element.
permit-acme-config: This rule gives the "limited" group read-write permit-acme-config: This rule gives the "limited" group read-write
access to the acme <config-parameters>. access to the acme <config-parameters>.
permit-dummy-interface: This rule gives the "limited" and "guest" permit-dummy-interface: This rule gives the "limited" and "guest"
skipping to change at page 50, line 47 skipping to change at page 48, line 38
<access-operations>read</access-operations> <access-operations>read</access-operations>
<action>deny</action> <action>deny</action>
<comment> <comment>
Do not allow the guest or limited groups Do not allow the guest or limited groups
to receive config change events. to receive config change events.
</comment> </comment>
</rule> </rule>
</rule-list> </rule-list>
</nacm> </nacm>
This example shows 1 notification rule: This example shows one notification rule:
deny-config-change: This rule prevents the "limited" or "guest" deny-config-change: This rule prevents the "limited" or "guest"
groups from receiving the acme <sys-config-change> event type. groups from receiving the acme <sys-config-change> event type.
Appendix B. Change Log
-- RFC Ed.: remove this section before publication.
B.1. 06-07
Added the leaf "enable-external-groups".
Removed dependency to RFC 6242.
Some editorial changes after IESG review.
B.2. 05-06
Added clarification to Security Considerations section about
ordered-by user lists (/nacm/rule-list and /nacm/rule-list/rule).
Added clarifications to security considerations wrt/ user names and
NETCONF capability changes.
Fixed typos found in review.
B.3. 04-05
Updated Security Considerations section.
Changed term 'operator' to 'administrator'.
Used the terms "access operation" and "protocol operation"
consistently.
Moved some normative text from section 2 to section 3. Also made it
more clear that section 2 is not a requirements section, but
documentation of the objectives for NACM.
Renamed "nacm:secure" to "nacm:default-deny-write", and "nacm:very-
secure" to "nacm:default-deny-all". Explained that "nacm:default-
deny-write" is ignored on rpc statements.
Described that <kill-session> and <delete-config> behave as if
specified with "nacm:default-deny-all".
B.4. 03-04
Introduced rule-lists to group related rules together.
Moved "module-rule", "rpc-rule", "notification-rule", and "data-rule"
into one common "rule", with a choice to select between the four
variants.
Changed "superuser" to "recovery session", and adjusted text
throughout document for this change.
Clarified behavior of global default NACM parameters, enable-nacm,
read-default, write-default, exec-default.
Clarified when access control is applied during system
initialization.
B.5. 02-03
Fixed improper usage of RFC 2119 keywords.
Changed term usage of "database" to "datastore".
Clarified that "secure" and "very-secure" extensions only apply if
the /nacm/enable-nacm object is "true".
B.6. 01-02
Removed authentication text and objects.
Changed module name from ietf-nacm to ietf-netconf-acm.
Updated NETCONF and YANG terminology.
Removed open issues section.
Changed some must to MUST in requirements section.
B.7. 00-01
Updated YANG anf YANG Types references.
Updated module namespace URI to standard format.
Updated module header meta-data to standard format.
Filled in IANA section.
B.8. 00
Initial version cloned from
draft-bierman-netconf-access-control-02.txt.
Authors' Addresses Authors' Addresses
Andy Bierman Andy Bierman
Brocade YumaWorks
Email: andy@netconfcentral.org EMail: andy@yumaworks.com
Martin Bjorklund Martin Bjorklund
Tail-f Systems Tail-f Systems
Email: mbj@tail-f.com EMail: mbj@tail-f.com
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