Internet Engineering Task Force A. Bierman
Internet-Draft Brocade
Intended status: Standards Track M. Bjorklund
Expires: December 16, 2011 Tail-f Systems
June 14, 2011
Network Configuration Protocol Access Control Model
draft-ietf-netconf-access-control-04
Abstract
The standardization of network configuration interfaces for use with
the NETCONF protocol requires a structured and secure operating
environment that promotes human usability and multi-vendor
interoperability. There is a need for standard mechanisms to
restrict NETCONF protocol access for particular users to a pre-
configured subset of all available NETCONF operations and content.
This document discusses requirements for a suitable access control
model, and provides one solution that meets these requirements.
Status of this Memo
This Internet-Draft is submitted in full conformance with the
provisions of BCP 78 and BCP 79.
Internet-Drafts are working documents of the Internet Engineering
Task Force (IETF). Note that other groups may also distribute
working documents as Internet-Drafts. The list of current Internet-
Drafts is at http://datatracker.ietf.org/drafts/current/.
Internet-Drafts are draft documents valid for a maximum of six months
and may be updated, replaced, or obsoleted by other documents at any
time. It is inappropriate to use Internet-Drafts as reference
material or to cite them other than as "work in progress."
This Internet-Draft will expire on December 16, 2011.
Copyright Notice
Copyright (c) 2011 IETF Trust and the persons identified as the
document authors. All rights reserved.
This document is subject to BCP 78 and the IETF Trust's Legal
Provisions Relating to IETF Documents
(http://trustee.ietf.org/license-info) in effect on the date of
publication of this document. Please review these documents
carefully, as they describe your rights and restrictions with respect
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to this document. Code Components extracted from this document must
include Simplified BSD License text as described in Section 4.e of
the Trust Legal Provisions and are provided without warranty as
described in the Simplified BSD License.
Table of Contents
1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . . 4
1.1. Terminology . . . . . . . . . . . . . . . . . . . . . . . 4
1.1.1. Requirements Notation . . . . . . . . . . . . . . . . 4
1.1.2. NETCONF Terms . . . . . . . . . . . . . . . . . . . . 4
1.1.3. YANG Terms . . . . . . . . . . . . . . . . . . . . . . 5
1.1.4. NACM Terms . . . . . . . . . . . . . . . . . . . . . . 5
2. Access Control Design Objectives . . . . . . . . . . . . . . . 6
2.1. Protocol Control Points . . . . . . . . . . . . . . . . . 6
2.2. Simplicity . . . . . . . . . . . . . . . . . . . . . . . . 7
2.3. Procedural Interface . . . . . . . . . . . . . . . . . . . 7
2.4. Datastore Access . . . . . . . . . . . . . . . . . . . . . 8
2.4.1. Access Rights . . . . . . . . . . . . . . . . . . . . 8
2.4.2. <get> and <get-config> Operations . . . . . . . . . . 8
2.4.3. <edit-config> Operation . . . . . . . . . . . . . . . 9
2.4.4. <copy-config> Operation . . . . . . . . . . . . . . . 10
2.5. Users and Groups . . . . . . . . . . . . . . . . . . . . . 10
2.6. Maintenance . . . . . . . . . . . . . . . . . . . . . . . 11
2.7. Configuration Capabilities . . . . . . . . . . . . . . . . 11
2.8. Identifying Security Holes . . . . . . . . . . . . . . . . 11
2.9. Data Shadowing . . . . . . . . . . . . . . . . . . . . . . 12
2.10. NETCONF Specific Requirements . . . . . . . . . . . . . . 12
3. NETCONF Access Control Model (NACM) . . . . . . . . . . . . . 14
3.1. Introduction . . . . . . . . . . . . . . . . . . . . . . . 14
3.1.1. Features . . . . . . . . . . . . . . . . . . . . . . . 14
3.1.2. External Dependencies . . . . . . . . . . . . . . . . 15
3.1.3. Message Processing Model . . . . . . . . . . . . . . . 15
3.2. Model Components . . . . . . . . . . . . . . . . . . . . . 17
3.2.1. Users . . . . . . . . . . . . . . . . . . . . . . . . 17
3.2.2. Groups . . . . . . . . . . . . . . . . . . . . . . . . 17
3.2.3. Sessions . . . . . . . . . . . . . . . . . . . . . . . 18
3.2.4. Access Permissions . . . . . . . . . . . . . . . . . . 18
3.2.5. Global Enforcement Controls . . . . . . . . . . . . . 18
3.2.5.1. enable-nacm Switch . . . . . . . . . . . . . . . . 18
3.2.5.2. read-default Switch . . . . . . . . . . . . . . . 19
3.2.5.3. write-default Switch . . . . . . . . . . . . . . . 19
3.2.5.4. exec-default Switch . . . . . . . . . . . . . . . 19
3.2.6. Access Control Rules . . . . . . . . . . . . . . . . . 20
3.3. Access Control Enforcement Procedures . . . . . . . . . . 20
3.3.1. Initial Operation . . . . . . . . . . . . . . . . . . 20
3.3.2. Session Establishment . . . . . . . . . . . . . . . . 21
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3.3.3. "access-denied" Error Handling . . . . . . . . . . . . 21
3.3.4. Incoming RPC Message Validation . . . . . . . . . . . 21
3.3.5. Data Node Access Validation . . . . . . . . . . . . . 24
3.3.6. Outgoing <notification> Authorization . . . . . . . . 26
3.4. Data Model Definitions . . . . . . . . . . . . . . . . . . 28
3.4.1. Data Organization . . . . . . . . . . . . . . . . . . 28
3.4.2. YANG Module . . . . . . . . . . . . . . . . . . . . . 29
3.5. IANA Considerations . . . . . . . . . . . . . . . . . . . 38
3.6. Security Considerations . . . . . . . . . . . . . . . . . 39
4. References . . . . . . . . . . . . . . . . . . . . . . . . . . 41
4.1. Normative References . . . . . . . . . . . . . . . . . . . 41
4.2. Informative References . . . . . . . . . . . . . . . . . . 41
Appendix A. Usage Examples . . . . . . . . . . . . . . . . . . . 42
A.1. <groups> Example . . . . . . . . . . . . . . . . . . . . . 42
A.2. Module Rule Example . . . . . . . . . . . . . . . . . . . 43
A.3. RPC Rule Example . . . . . . . . . . . . . . . . . . . . . 44
A.4. Data Rule Example . . . . . . . . . . . . . . . . . . . . 46
A.5. Notification Rule Example . . . . . . . . . . . . . . . . 48
Appendix B. Change Log . . . . . . . . . . . . . . . . . . . . . 50
B.1. 03-04 . . . . . . . . . . . . . . . . . . . . . . . . . . 50
B.2. 02-03 . . . . . . . . . . . . . . . . . . . . . . . . . . 50
B.3. 01-02 . . . . . . . . . . . . . . . . . . . . . . . . . . 50
B.4. 00-01 . . . . . . . . . . . . . . . . . . . . . . . . . . 50
B.5. 00 . . . . . . . . . . . . . . . . . . . . . . . . . . . . 51
Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . . 52
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1. Introduction
The NETCONF protocol does not provide any standard mechanisms to
restrict the operations and content that each user is authorized to
use.
There is a need for inter-operable management of the controlled
access to operator selected portions of the available NETCONF content
within a particular server.
This document addresses access control mechanisms for the Operation
and Content layers of NETCONF, as defined in
[I-D.ietf-netconf-4741bis], and [RFC5277]. It contains three main
sections:
1. Access Control Design Objectives
2. NETCONF Access Control Model (NACM)
3. YANG Data Model (ietf-netconf-acm.yang)
1.1. Terminology
1.1.1. Requirements Notation
The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT",
"SHOULD", "SHOULD NOT", "RECOMMENDED", "MAY", and "OPTIONAL" in this
document are to be interpreted as described in [RFC2119].
1.1.2. NETCONF Terms
The following terms are defined in [I-D.ietf-netconf-4741bis] and are
not redefined here:
o client
o datastore
o operation
o protocol operation
o server
o session
o user
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1.1.3. YANG Terms
The following terms are defined in [RFC6020] and are not redefined
here:
o data node
o data definition statement
1.1.4. NACM Terms
The following terms are used throughout this documentation:
access control: A security feature provided by the NETCONF server,
that allows an operator to restrict access to a subset of all
NETCONF protocol operations and data, based on various criteria.
access control model (ACM): A conceptual model used to configure and
monitor the access control procedures desired by the operator to
enforce a particular access control policy.
access control rule: The conceptual criteria used to determine if a
particular NETCONF protocol operation will be permitted or denied.
access operation: How a request attempts to access a conceptual
object. One of "read", "create", "delete", "update", and
"execute".
recovery session: A special administrative session that is given
unlimited NETCONF access, and is exempt from all access control
enforcement. The specific mechanism(s) used by an implementation
to control and identify whether a session is a recovery session or
not are outside the scope of this document.
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2. Access Control Design Objectives
[Editor's note: some things described here are requirements (MUST,
SHOULD, etc), but some things are descriptions how NACM works, e.g.
2.4.1, 2.4.3...]
2.1. Protocol Control Points
The NETCONF protocol allows new operations to be added at any time,
and the YANG data modeling language supports this feature. It is not
possible to design an ACM for NETCONF which only focuses on a static
set of operations, like some other protocols. Since few assumptions
can be made about an arbitrary protocol operation, the NETCONF
architectural server components need to be protected at several
conceptual control points.
+-------------+ +-------------+
client | protocol | | prune | client
request --> | operation | | restricted | ---> reply
| allowed? | | <rpc-reply> |
+-------------+ | nodes? |
| +-------------+
| if any datastore or
| state data is accessed
| by the operation
V
+-------------+ +----------------+
| data node | | prune |
| access | | restricted |
| allowed? | | <notification> | ---> client
+-------------+ | event or data? | session
+----------------+
Figure 1
The following access control points are defined:
protocol operation: Configurable permission to invoke specific
protocol operations is required. Wildcard or multiple target
mechanisms to reduce configuration and effort are also required.
NETCONF datastore: Configurable permission to read and/or alter
specific data nodes within any conceptual datastore is required.
Wildcard or multiple target mechanisms to reduce configuration and
effort are also required.
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RPC Reply Content: Configurable permission to read specific data
nodes within any conceptual RPC output section is required.
Unauthorized data is silently omitted from the reply, instead of
dropping the reply or sending an "access-denied" error.
Notification Content: Configurable permission to receive specific
notification event types is required.
2.2. Simplicity
Experience has shown that a complicated ACM will not be widely
deployed, because it is too hard to use. The key factor that is
ignored in such solutions is the concept of "localized cost". It
needs to be easy to do simple things, and possible to do complex
things, instead of hard to do everything.
Configuration of the access control system needs to be as simple as
possible. Simple and common tasks need to be easy to configure, and
require little expertise or domain-specific knowledge. Complex tasks
are possible using additional mechanisms, which may require
additional expertise.
A single set of access control rules SHOULD be able to control all
types of NETCONF protocol operation invocation, all conceptual
datastore access, and all NETCONF session output.
Access control SHOULD be defined with a small and familiar set of
permissions, while still allowing full control of NETCONF datastore
access.
Access control does not need to be applied to NETCONF <hello>
messages.
2.3. Procedural Interface
The NETCONF protocol uses a procedural interface model, and an
extensible set of protocol operations. Access control for any
possible protocol operation is required.
It MUST be possible to configure the ACM to permit or deny access to
specific NETCONF operations.
YANG modules SHOULD be designed so that different access levels for
input parameters to protocol operations is not required. Use of
generic operations should be avoided, and separate operations defined
instead, if different access levels are needed.
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2.4. Datastore Access
It MUST be possible to control access to specific nodes and subtrees
within the conceptual NETCONF datastore.
The same access control rules apply to all conceptual datastores.
For example, the candidate configuration or the running
configuration.
Only the standard NETCONF datastores (candidate, running, and
startup) are controlled by the ACM. Local or remote files or
datastores accessed via the <url> parameter are optional to support.
The non-volatile startup configuration needs to be loaded at boot-
time into the running configuration without applying any access
control rules. Access control is applied after the server has
booted, and user sessions are active.
2.4.1. Access Rights
A small set of hard-wired datastore access rights is needed to
control access to all possible NETCONF datastore operations,
including vendor extensions to the standard operation set.
The familiar "CRUDX" model can support all NETCONF operations:
o Create: Allows the client to add a new data node instance to a
datastore.
o Read: Allows the client to read a data node instance from a
datastore, or receive the notification event type.
o Update: Allows the client to update an existing data node instance
in a datastore.
o Delete: Allows the client to delete a data node instance from a
datastore.
o eXec: Allows the client to execute the protocol operation.
2.4.2. <get> and <get-config> Operations
Data nodes to which the client does not have read access, either
directly or via wildcard access, are silently omitted from the <rpc-
reply> message. This is done to allow NETCONF filters for <get> and
<get-config> to function properly, instead of causing an "access-
denied" error because the filter criteria would otherwise include
unauthorized read access to some data nodes. For NETCONF filtering
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purposes, the selection criteria is applied to the subset of nodes
that the client is authorized to read, not the entire datastore.
2.4.3. <edit-config> Operation
The NACM access rights are not directly coupled to the <edit-config>
"operation" attribute, although they are similar. Instead, a NACM
access right applies to all operations which would result in a
particular access operation to the target datastore. This section
describes how these access rights apply to the specific datastore
operations supported by the <edit-config> operation.
If the effective operation is "none" (i.e., default-operation="none")
for a particular data node, then no access control is applied to that
data node.
A "create", "merge", or "replace" operation on a datastore node which
would result in the creation of a new data node instance, for which
the user does not have "create" access permission, is rejected with
an "access-denied" error.
A "merge" or "replace" operation on a datastore node which would
result in the modification of an existing data node instance, for
which the user does not have "update" access permission, is rejected
with an "access-denied" error.
A "replace", "delete", or "remove" operation on a datastore node
which would result in the deletion of an existing data node instance,
for which the user does not have "delete" access permission, is
rejected with an "access-denied" error.
A "merge" operation may include data nodes which do not alter
portions of the existing datastore. For example, a container or list
node may be present for naming purposes, but does not actually alter
the corresponding datastore node. These unaltered data nodes within
the scope of a "merge" operation are ignored by the server, and do
not require any access rights by the client.
[Editor's note: ditto for "replace" (and copy-config...) Note that
with this rule, a client w/o read access can guess db content by
sending merge requests - if access-denied is not returned, it means
the db has that value.]
A "merge" operation may include data nodes, but not include
particular child data nodes that are present in the datastore. These
missing data nodes within the scope of a "merge" operation are
ignored by the server, and do not require any access rights by the
client.
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The contents of specific restricted datastore nodes MUST NOT be
exposed in any <rpc-error> elements within the reply.
2.4.4. <copy-config> Operation
Access control for the <copy-config> operation requires special
consideration because the operator is replacing the entire target
datastore. Read access to the entire source datastore, and write
access to the entire target datastore is needed for this operation to
succeed.
The server SHOULD determine the exact nodes in the target datastore
which are actually different, and only check write access permissions
for this set of nodes, which could be empty. For example, if a
session can read the entire datastore, but only change one leaf, that
session SHOULD be able to edit and save that one leaf. E.g., the
<copy-config> operation from <running> to <startup> SHOULD succeed if
the only effective changes are for data nodes that session is
authorized to change.
A client MUST have access to every datastore node, even ones that are
not present in the source configuration data.
For example, consider a common use-case such as a simple backup and
restore procedure. The operator (client) MUST have full read access
to the datastore in order to receive a complete copy of its contents.
If the server simply omits these subtrees from the reply, and that
copy is later used to restore the server datastore, the server will
interpret the missing nodes as a request to delete those nodes, and
return an error.
2.5. Users and Groups
The server MUST obtain a user name from the underlying NETCONF
transport, such as an SSH user name.
It MUST be possible to specify access control rules for a single user
or a configurable group of users.
The ACM MUST support the concept of administrative groups, to support
the well-established distinction between a root account and other
types of less-privileged conceptual user accounts. These groups MUST
be configurable by the operator.
It MUST be possible to delegate the user-to-group mapping to a
central server, such as a RADIUS server [RFC2865] [RFC5607]. Since
authentication is performed by the NETCONF transport layer, and
RADIUS performs authentication and service authorization at the same
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time, it MUST be possible for the underlying NETCONF transport to
report a set of group names associated with the user to the server.
2.6. Maintenance
It SHOULD be possible to disable part or all of the access control
model without deleting any configuration.
2.7. Configuration Capabilities
Suitable control and monitoring mechanisms are needed to allow an
operator to easily manage all aspects of the ACM behavior. A
standard data model, suitable for use with the <edit-config>
operation MUST be available for this purpose.
Access control rules to restrict operations on specific subtrees
within the configuration datastore MUST be supported. Existing
mechanisms can be used to identify the subtree(s) for this purpose.
2.8. Identifying Security Holes
One of the most important aspects of the data model documentation,
and biggest concerns during deployment, is the identification of
security-sensitive content. This applies to operations in NETCONF,
not just data and notifications.
It is mandatory for security-sensitive objects to be documented in
the Security Considerations section of an RFC. This is nice, but it
is not good enough, for the following reasons:
o This documentation-only approach forces operators to study the RFC
and determine if there are any potential security holes introduced
by a new YANG module.
o If any security holes are identified, then the operator can study
some more RFC text, and determine how to close the security
hole(s).
o The ACM on each server can be configured to close the security
holes, e.g., require privileged access to read or write the
specific data identified in the Security Considerations section.
o If the ACM is not pre-configured, then there will be a time window
of vulnerability, after the new module is loaded, and before the
new access control rules for that module are configured, enabled,
and debugged.
Often, the operator just wants to disable default access to the
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secure content, so no inadvertent or malicious changes can be made to
the server. This allows the default rules to be more lenient,
without significantly increasing the security risk.
A data model designer needs to be able to use machine-readable
statements to identify NETCONF content which needs to be protected by
default. This will allow client and server tools to automatically
close data-model specific security holes, by denying access to
sensitive data unless the user is explicitly authorized to perform
the requested operation.
2.9. Data Shadowing
One of the more complicated security administration problems is
identifying data nodes which shadow or mirror the content of another
data node. An access control rule to prevent read operations for a
particular node may be insufficient to prevent access to the data
node with the copied value.
If the description statement, other documentation, or no
documentation exists to identify a data shadow problem, then it may
not be detected.
Since NETCONF allows any vendor operation to be added to the
protocol, there is no way to reliably identify all of the operations
that may expose copies of sensitive data nodes in <rpc-reply>
messages.
A NETCONF server MUST ensure that unauthorized access to its
conceptual datastores and non-configuration data nodes is prevented.
It is beyond the scope of this document to define access control
enforcement procedures for underlying device instrumentation that may
exist to support the NETCONF server operation. An operator can
identify each operation that the server provides, and decide if it
needs any access control applied to it.
Proprietary protocol operations SHOULD be properly documented by the
vendor, so it is clear to operators what data nodes (if any) are
affected by the operation, and what information (if any) is returned
in the <rpc-reply> message.
2.10. NETCONF Specific Requirements
The server MUST be able to identify the specific protocol access
request at the 4 access control points defined above.
The server MUST be able to identify any datastore access request,
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even for proprietary operations.
A client MUST always be authorized to invoke the <close-session>
operation, defined in [I-D.ietf-netconf-4741bis].
A client MUST always be authorized to receive the <replayComplete>
and <notificationComplete> notification events, defined in [RFC5277]
The set of module name strings used within one particular server MUST
be unique.
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3. NETCONF Access Control Model (NACM)
3.1. Introduction
This section provides a high-level overview of the access control
model structure. It describes the NETCONF protocol message
processing model, and the conceptual access control requirements
within that model.
3.1.1. Features
The NACM data model provides the following features:
o Independent control of RPC, data, and notification access.
o Simple access control rules configuration data model that is easy
to use.
o The concept of an emergency recovery session is supported, but
configuration of the server for this purpose is beyond the scope
of this document. An emergency recovery session will bypass all
access control enforcement, in order to allow it to initialize or
repair the NACM configuration.
o A simple and familiar set of datastore permissions is used.
o Support for YANG security tagging (e.g., nacm:secure extension)
allows default security modes to automatically exclude sensitive
data.
o Separate default access modes for read, write, and execute
permissions.
o Access control rules are applied to configurable groups of users.
o The entire ACM can be disabled during operation, in order to debug
operational problems.
o Access control rules are simple to configure.
o The number of denied protocol operation requests and denied
datastore write requests can be monitored by the client.
o Simple unconstrained YANG instance identifiers are used to
configure access control rules for specific data nodes.
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3.1.2. External Dependencies
The NETCONF [I-D.ietf-netconf-4741bis] protocol is used for all
management purposes within this document. It is expected that the
mandatory transport mapping NETCONF Over SSH
[I-D.ietf-netconf-rfc4742bis] is also supported by the server, and
that the server has access to the user name associated with each
session.
The YANG Data Modeling Language [RFC6020] is used to define the
NETCONF data models specified in this document.
3.1.3. Message Processing Model
The following diagram shows the NETCONF message flow model, including
the points at which access control is applied, during NETCONF message
processing.
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+-------------------------+
| session |
| (username) |
+-------------------------+
| ^
V |
+--------------+ +---------------+
| message | | message |
| dispatcher | | generator |
+--------------+ +---------------+
| ^ ^
V | |
+===========+ +-------------+ +----------------+
| <rpc> |---> | <rpc-reply> | | <notification> |
| acc. ctl | | generator | | generator |
+===========+ +-------------+ +----------------+
| ^ ^ ^
V +------+ | |
+-----------+ | +=============+ +================+
| <rpc> | | | <rpc-reply> | | <notification> |
| processor |-+ | acc. ctl | | access ctl |
+-----------+ +=============+ +================+
| | ^ ^
V +----------------+ | |
+===========+ | | |
| data node | | | |
| acc. ctl | -----------+ | | |
+===========+ | | | |
| | | | |
V V V | |
+---------------+ +-----------------+
| configuration | ---> | server |
| datastore | | instrumentation |
| | <--- | |
+---------------+ +-----------------+
Figure 2
The following high-level sequence of conceptual processing steps is
executed for each received <rpc> message, if access control
enforcement is enabled:
o Access control is applied to all <rpc> messages (except <close-
session>) received by the server, individually, for each active
session, unless the session is identified as a "recovery session".
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o If the session is authorized to execute the specified RPC
operation, then processing continues, otherwise the request is
rejected with an "access-denied" error.
o If the configuration datastore or conceptual state data is
accessed by the protocol operation, then the data node access MUST
be authorized. If the session is authorized to perform the
requested operation on the requested data, then processing
continues.
The following sequence of conceptual processing steps is executed for
each generated notification event, if access control enforcement is
enabled:
o Server instrumentation generates a conceptual notification, for a
particular subscription.
o The notification access control enforcer checks the notification
event type, and if it is one which the session is not authorized
to read, then the notification is dropped for that subscription.
3.2. Model Components
This section defines the conceptual components related to access
control model.
3.2.1. Users
A "user" is the conceptual entity that is associated with the access
permissions granted to a particular session. A user is identified by
a string which MUST be unique within the server.
As described in [I-D.ietf-netconf-4741bis], the user name string is
derived from the transport layer during session establishment. If
the transport layer cannot authenticate the user, the session is
terminated.
The server MAY support a "recovery session" mechanism, which will
bypass all access control enforcement. This is useful for
restricting initial access and repairing a broken access control
configuration.
3.2.2. Groups
Access to a specific NETCONF operation is granted to a session,
associated with a group, not a user.
A group is identified by its name. All group names MUST be unique
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within the server.
A group member is identified by a user name string.
The same user may be configured in multiple groups.
3.2.3. Sessions
A session is simply a NETCONF session, which is the entity that is
granted access to specific NETCONF operations.
A session is associated with a single user name for the lifetime of
the session.
3.2.4. Access Permissions
The access permissions are the NETCONF protocol specific set of
permissions that have been assigned to a particular session.
The same access permissions MUST stay in effect for the processing of
a particular message.
The server MUST use the access control rules in effect at the time
the message is processed.
The access control model treats protocol operation execution
separately from configuration datastore access and outgoing messages:
create: Permission to create conceptual server data.
read: Read access to conceptual server data, <rpc-reply> and
<notification> content.
update: Permission to modify existing conceptual server data.
delete: Permission to delete existing conceptual server data.
exec: Permission to invoke a protocol operation.
3.2.5. Global Enforcement Controls
There are four global controls that are used to help control how
access control is enforced.
3.2.5.1. enable-nacm Switch
A global "enable-nacm" on/off switch is provided to enable or disable
all access control enforcement. When this global switch is set to
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"true", then all access requested are checked against the access
control rules, and only permitted if configured to allow the specific
access request. When this global switch is set to "false", then all
access requested are permitted.
3.2.5.2. read-default Switch
An on/off "read-default" switch is provided to enable or disable
default access to receive data in replies and notifications. When
the "enable-nacm" global switch is set to "true", then this global
switch is relevant, if no matching access control rule is found to
explicitly permit or deny read access to the requested NETCONF
datastore data or notification event type.
When this global switch is set to "permit", and no matching access
control rule is found for the NETCONF datastore read or notification
event requested, then access is permitted.
When this global switch is set to "deny", and no matching access
control rule is found for the NETCONF datastore read or notification
event requested, then access is denied.
3.2.5.3. write-default Switch
An on/off "write-default" switch is provided to enable or disable
default access to alter configuration data. When the "enable-nacm"
global switch is set to "true", then this global switch is relevant,
if no matching access control rule is found to explicitly permit or
deny write access to the requested NETCONF datastore data.
When this global switch is set to "permit", and no matching access
control rule is found for the NETCONF datastore write requested, then
access is permitted.
When this global switch is set to "deny", and no matching access
control rule is found for the NETCONF datastore write requested, then
access is denied.
3.2.5.4. exec-default Switch
An on/off "exec-default" switch is provided to enable or disable
default access to execute protocol operations. When the "enable-
nacm" global switch is set to "true", then this global switch is
relevant, if no matching access control rule is found to explicitly
permit or deny access to the requested NETCONF protocol operation.
When this global switch is set to "permit", and no matching access
control rule is found for the NETCONF protocol operation requested,
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then access is permitted.
When this global switch is set to "deny", and no matching access
control rule is found for the NETCONF protocol operation requested,
then access is denied.
3.2.6. Access Control Rules
There are 4 types of rules available in NACM:
module rule: Controls access for definitions in a specific module,
identified by its name.
protocol operation rule: Controls access for a specific protocol
operation, identified by its module and name.
data node rule: Controls access for a specific data node, identified
by its path location within the conceptual XML document for the
data node.
notification rule: Controls access for a specific notification event
type, identified by its module and name.
3.3. Access Control Enforcement Procedures
There are seven separate phases that need to be addressed, four of
which are related to the NETCONF message processing model. In
addition, the initial start-up mode for a NETCONF server, session
establishment, and "access-denied" error handling procedures also
need to be considered.
3.3.1. Initial Operation
Upon the very first start-up of the NETCONF server, the access
control configuration will probably not be present. If it isn't, a
server MUST NOT allow any write access to any session role except a
"recovery session", if supported.
Access control rules are not enforced before or while the non-
volatile configuration data is processed and loaded into the running
configuration, when the server is booting or rebooting. Access rules
are enforced any time a request is initiated from a user session.
Access control is not enforced for server-initiated access requests,
such as the initial load of the running datastore, during bootup.
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3.3.2. Session Establishment
The access control model applies specifically to the well-formed XML
content transferred between a client and a server, after session
establishment has been completed, and after the <hello> exchange has
been successfully completed.
A server SHOULD NOT include any sensitive information in any
<capability> elements within the <hello> exchange.
Once session establishment is completed, and a user has been
authenticated, the NETCONF transport layer reports the user name and
a possibly empty set of group names associated with the user to the
NETCONF server. The NETCONF server will enforce the access control
rules, based on the supplied user name, group names, and the
configuration data stored on the server.
3.3.3. "access-denied" Error Handling
The "access-denied" error-tag is generated when the access control
system denies access to either a request to invoke a protocol
operation or a request to perform a particular operation on the
configuration datastore.
A server MUST NOT include any sensitive information in any <error-
info> elements within the <rpc-error> response.
3.3.4. Incoming RPC Message Validation
The diagram below shows the basic conceptual structure of the access
control processing model for incoming NETCONF <rpc> messages, within
a server.
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NETCONF server
+------------+
| XML |
| message |
| dispatcher |
+------------+
|
|
V
+------------+
| NC-base NS |
| <rpc> |
+------------+
| | |
| | +-------------------------+
| +------------+ |
V V V
+-----------+ +---------------+ +------------+
| acme NS | | NC-base NS | | NC-base NS |
| <my-edit> | | <edit-config> | | <unlock> |
+-----------+ +---------------+ +------------+
| |
| |
V V
+----------------------+
| |
| configuration |
| datastore |
+----------------------+
Figure 3
Access control begins with the message dispatcher.
After the server validates the <rpc> element, and determines the
namespace URI and the element name of the protocol operation being
requested, the RPC access control enforcer verifies that the session
is authorized to invoke the protocol operation.
The protocol operation is authorized by following these steps:
1. If the "enable-nacm" leaf is set to "false", then the protocol
operation is permitted.
2. If the requesting session is identified as a "recovery session",
then the protocol operation is permitted.
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3. If the requested operation is the NETCONF <close-session>
operation, then the protocol operation is permitted.
4. Check all the "group" entries for ones that contain a "user-
name" entry that equals the user name for the session making the
request. Add to these groups the set of groups provided by the
transport layer.
5. If no groups are found, continue with step 10.
6. Process all rule-list entries, in order. If a rule-list's
"group" leaf-list does not match any of the user's groups,
proceed to the next rule-list entry.
7. For each rule-list entry found, process all rules, in order,
until a rule that matches the requested operation is 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 YANG module where the protocol operation is defined.
* The rule does not have a "rule-type" defined, or the "rule-
type" is "protocol-operation" and the "rpc-name" is "*" or
equals the name of the requested protocol operation.
* The rule's "access-operations" leaf has the "exec" bit set,
or has the special value "*".
8. If a matching rule is found, then the "action" leaf is checked.
If it is equal to "permit", then the protocol operation is
permitted, otherwise it is denied.
9. Otherwise, no matching rule was found in any rule-list entry.
10. If the requested protocol operation is defined in a YANG module
advertised in the server capabilities, and the "rpc" statement
contains a "nacm:secure" or a "nacm:very-secure" statement, then
the protocol operation is denied.
11. If the "exec-default" leaf is set to "permit", then permit the
protocol operation, otherwise deny the request.
If the session is not authorized to invoke the protocol operation
then an <rpc-error> is generated with the following information:
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error-tag: access-denied
error-path: Identifies the requested protocol operation. For
example:
<error-path
xmlns:nc="urn:ietf:params:xml:ns:netconf:base:1.0">
/nc:rpc/nc:edit-config
</error-path>
represents the <edit-config> operation in the NETCONF base
namespace.
If a datastore is accessed, either directly or as a side effect of
the protocol operation, then the server MUST intercept the operation
and make sure the session is authorized to perform the requested
operation on the specified data, as defined in Section 3.3.5.
3.3.5. Data Node Access Validation
If a data node within a datastore is accessed, then the server MUST
ensure that the client session is authorized to perform the requested
read, create, update, or delete operation on the specified data node.
The data node access request is authorized by following these steps:
1. If the "enable-nacm" leaf is set to "false", then the protocol
operation is permitted.
2. If the requesting session is identified as a "recovery session",
then the protocol operation is permitted.
3. Check all the "group" entries for ones that contain a "user-
name" entry that equals the user name for the session making the
request. Add to these groups the set of groups provided by the
transport layer.
4. If no groups are found, continue with step 9.
5. Process all rule-list entries, in order. If a rule-list's
"group" leaf-list does not match any of the user's groups,
proceed to the next rule-list entry.
6. For each rule-list entry found, process all rules, in order,
until a rule that matches the requested operation is found. A
rule matches if all of the following criteria are met:
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* The rule's "module-name" leaf is "*", or equals the name of
the YANG module where the protocol operation is defined.
* The rule does not have a "rule-type" defined, or the "rule-
type" is "data-node" and the "path" matches the requested
data node.
* For a read operation, the rule's "access-operations" leaf has
the "read" bit set, or has the special value "*".
* For a creation operation, the rule's "access-operations" leaf
has the "create" bit set, or has the special value "*".
* For a deletion operation, the rule's "access-operations" leaf
has the "delete" bit set, or has the special value "*".
* For an update operation, the rule's "access-operations" leaf
has the "update" bit set, or has the special value "*".
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
permitted, otherwise it is denied. For a read operation,
"denied" means that the requested data is not returned in the
reply.
8. Otherwise, no matching rule was found in any rule-list entry.
9. For a read operation, if the requested data node is defined in a
YANG module advertised in the server capabilities, and the data
definition statement contains a "nacm:very-secure" statement,
then the requested data node is not included in the reply.
10. For a write operation, if the requested data node is defined in
a YANG module advertised in the server capabilities, and the
data definition statement contains a "nacm:secure" or a "nacm:
very-secure" statement, then the data node access request is
denied.
11. For a read operation, if the "read-default" leaf is set to
"permit", then include the requested data node in the reply,
otherwise do not include the requested data node in the reply.
12. For a write operation, if the "write-default" leaf is set to
"permit", then permit the data node access request, otherwise
deny the request.
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3.3.6. Outgoing <notification> Authorization
Configuration of access control rules specifically for descendant
nodes of the notification event type element are outside the scope of
this document. If the session is authorized to receive the
notification event type, then it is also authorized to receive any
data it contains.
The following figure shows the conceptual message processing model
for outgoing <notification> messages.
NETCONF server
+------------+
| XML |
| message |
| generator |
+------------+
^
|
+----------------+
| <notification> |
| generator |
+----------------+
^
|
+=================+
| <notification> |
| access control |
| <eventType> |
+=================+
^
|
+------------------------+
| server instrumentation |
+------------------------+
| ^
V |
+----------------------+
| configuration |
| datastore |
+----------------------+
Figure 4
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The generation of a notification for a specific subscription is
authorized by following these steps:
1. If the "enable-nacm" leaf is set to "false", then the
notification is permitted.
2. If the session is identified as a "recovery session", then the
notification is permitted.
3. If the notification is the NETCONF <replayComplete> or
<notificationComplete> event type, then the notification is
permitted.
4. Check all the "group" entries for ones that contain a "user-
name" entry that equals the user name for the session making the
request. Add to these groups the set of groups provided by the
transport layer.
5. If no groups are found, continue with step 10.
6. Process all rule-list entries, in order. If a rule-list's
"group" leaf-list does not match any of the user's groups,
proceed to the next rule-list entry.
7. For each rule-list entry found, process all rules, in order,
until a rule that matches the requested operation is 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 YANG module where the protocol operation is defined.
* The rule does not have a "rule-type" defined, or the "rule-
type" is "notification" and the "notification-name" is "*",
equals the name of the notification.
* The rule's "access-operations" leaf has the "read" bit set,
or has the special value "*".
8. If a matching rule is found, then the "action" leaf is checked.
If it is equal to "permit", then permit the notification,
otherwise drop the notification for the associated subscription.
9. Otherwise, no matching rule was found in any rule-list entry.
10. If the requested notification is defined in a YANG module
advertised in the server capabilities, and the "notification"
statement contains a "nacm:very-secure" statement, then the
notification is dropped for the associated subscription.
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11. If the "read-default" leaf is set to "permit", then permit the
notification, otherwise drop the notification for the associated
subscription.
3.4. Data Model Definitions
This section defines the semantics of the conceptual data structures
found in the data model in Section 3.4.
3.4.1. Data Organization
The top-level element is called <nacm>, and it is defined in the
"ietf-netconf-acm" module's namespace.
There are several data structures defined as child nodes of the
<nacm> element:
leaf <enable-nacm>: On/off boolean switch to enable or disable
access control enforcement.
leaf <read-default>: Enumeration to permit or deny default read
access requests.
leaf <write-default>: Enumeration to permit or deny default write
access requests.
leaf <exec-default>: Enumeration to permit or deny default protocol
operation execution requests.
leaf <denied-rpcs>: Read-only counter of the number of times the
server has denied an RPC operation request, since the last reboot
of the server.
leaf <denied-data-writes>: Read-only counter of the number of times
the server has denied a data node write request, since the last
reboot of the server.
leaf <denied-notifications>: Read-only counter of the number of
times the server has denied a notification, since the last reboot
of the server.
container <groups>: Configures the groups used within the access
control system.
list <group>: A list of user names belonging to the same
administrative group.
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container <rules>: Configures the access control rules used within
the server.
list <rule-list>: An ordered collection of related access control
rules.
list <rule>: Configures the access control rules for protocol
operation invocation, configuration datastore access, and
for controlling delivery of <notification> events.
3.4.2. YANG Module
The following YANG module specifies the normative NETCONF content
that MUST by supported by the server.
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@2011-06-14.yang"
module ietf-netconf-acm {
namespace "urn:ietf:params:xml:ns:yang:ietf-netconf-acm";
prefix "nacm";
import ietf-yang-types {
prefix yang;
}
organization
"IETF NETCONF (Network Configuration) Working Group";
contact
"WG Web: <http://tools.ietf.org/wg/netconf/>
WG List: <mailto:netconf@ietf.org>
WG Chair: Mehmet Ersue
<mailto:mehmet.ersue@nsn.com>
WG Chair: Bert Wijnen
<mailto:bertietf@bwijnen.net>
Editor: Andy Bierman
<mailto:andy.bierman@brocade.com>
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Editor: Martin Bjorklund
<mailto:mbj@tail-f.com>";
description
"NETCONF Server Access Control Model.
Copyright (c) 2011 IETF Trust and the persons identified as
authors of the code. All rights reserved.
Redistribution and use in source and binary forms, with or
without modification, is permitted pursuant to, and subject
to the license terms contained in, the Simplified BSD
License set forth in Section 4.c of the IETF Trust's
Legal Provisions Relating to IETF Documents
(http://trustee.ietf.org/license-info).
This version of this YANG module is part of RFC XXXX; see
the RFC itself for full legal notices.";
// RFC Ed.: replace XXXX with actual RFC number and
// remove this note
// RFC Ed.: remove this note
// Note: extracted from draft-ietf-netconf-access-control-04.txt
// RFC Ed.: please update the date to the date of publication
revision "2011-06-14" {
description
"Initial version";
reference
"RFC XXXX: Network Configuration Protocol
Access Control Model";
}
/*
* Extension statements
*/
extension secure {
description
"Used to indicate that the data model node
represents a sensitive security system parameter.
If present, and the NACM module is enabled (i.e.,
/nacm/enable-nacm object equals 'true'), the NETCONF server
will only allow the designated 'recovery session' to have
write or execute access to the node. An explicit access
control rule is required for all other users.
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The 'secure' extension MAY appear within a data definition
statement or rpc statement. It is ignored otherwise.";
}
extension very-secure {
description
"Used to indicate that the data model node
controls a very sensitive security system parameter.
If present, and the NACM module is enabled (i.e.,
/nacm/enable-nacm object equals 'true'), the NETCONF server
will only allow the designated 'recovery session' to have
read, write, or execute access to the node. An explicit
access control rule is required for all other users.
The 'very-secure' extension MAY appear within a data
definition statement, rpc statement, or notification
statement. It is ignored otherwise.";
}
/*
* Derived types
*/
typedef user-name-type {
type string {
length "1..max";
}
description
"General Purpose User Name string.";
}
typedef matchall-string-type {
type string {
pattern "\*";
}
description
"The string containing a single asterisk '*' is used
to conceptually represent all possible values
for the particular leaf using this data type.";
}
typedef access-operations-type {
type bits {
bit create {
description
"Any operation that creates a
new instance of the specified data is a create
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operation.";
}
bit read {
description
"Any operation or notification that
returns data to an application is a read
operation.";
}
bit update {
description
"Any operation that alters an existing
data node is an update operation.";
}
bit delete {
description
"Any operation that removes a datastore
node instance is a delete operation.";
}
bit exec {
description
"Execution access to the specified RPC operation.
Any RPC operation invocation is an exec operation.";
}
}
description
"NETCONF Access Operation.";
}
typedef group-name-type {
type string {
length "1..max";
pattern "[^\*].*";
}
description
"Name of administrative group that can be
assigned to the user, and specified in
an access control rule-list.";
}
typedef action-type {
type enumeration {
enum permit {
description
"Requested action is permitted.";
}
enum deny {
description
"Requested action is denied.";
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}
}
description
"Action taken by the server when a particular
rule matches.";
}
typedef node-instance-identifier {
type yang:xpath1.0;
description
"Path expression used to represent a special
data node instance identifier string.
A node-instance-identifier value is an
unrestricted YANG instance-identifier expression.
All the same rules as an instance-identifier apply
except predicates for keys are optional. If a key
predicate is missing, then the node-instance-identifier
represents all possible server instances for that key.
This XPath expression is evaluated in the following context:
o The set of namespace declarations are those in scope on
the leaf element where this type is used.
o The set of variable bindings contains one variable,
'USER', which contains the name of user of the current
session.
o The function library is the core function library, but
note that due to the syntax restrictions of an
instance-identifier, no functions are allowed.
o The context node is the root node in the data tree.";
}
container nacm {
nacm:very-secure;
description
"Parameters for NETCONF Access Control Model.";
leaf enable-nacm {
type boolean;
default true;
description
"Enable or disable all NETCONF access control
enforcement. If 'true', then enforcement
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is enabled. If 'false', then enforcement
is disabled.";
}
leaf read-default {
type action-type;
default "permit";
description
"Controls whether read access is granted if
no appropriate rule is found for a
particular read request.";
}
leaf write-default {
type action-type;
default "deny";
description
"Controls whether create, update, or delete access
is granted if no appropriate rule is found for a
particular write request.";
}
leaf exec-default {
type action-type;
default "permit";
description
"Controls whether exec access is granted if no appropriate
rule is found for a particular RPC operation request.";
}
leaf denied-rpcs {
type yang:zero-based-counter32;
config false;
mandatory true;
description
"Number of times an RPC operation request was denied
since the server last restarted.";
}
leaf denied-data-writes {
type yang:zero-based-counter32;
config false;
mandatory true;
description
"Number of times a request to alter a data node
was denied, since the server last restarted.";
}
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leaf denied-notifications {
type yang:zero-based-counter32;
config false;
mandatory true;
description
"Number of times a notification was denied
since the server last restarted.";
}
container groups {
description
"NETCONF Access Control Groups.";
list group {
key name;
description
"One NACM Group Entry.";
leaf name {
type group-name-type;
description
"Group name associated with this entry.";
}
leaf-list user-name {
type user-name-type;
description
"Each entry identifies the user name of
a member of the group associated with
this entry.";
}
}
}
list rule-list {
key "name";
ordered-by user;
description
"An ordered collection of access control rules.";
leaf name {
type string {
length "1..256";
}
description
"Arbitrary name assigned to the rule-list.";
}
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leaf-list group {
type union {
type matchall-string-type;
type group-name-type;
}
description
"List of administrative groups that will be
assigned the associated access rights
defined by the 'rule' list.
The string '*' indicates that all groups apply to the
entry.";
}
list rule {
key "name";
ordered-by user;
description
"One access control rule.
Rules are processed in user-defined order until a match is
found. A rule matches if 'module-name', 'rule-type', and
'access-operations' matches the request. If a rule
matches, the 'action' leaf determines if access is granted
or not.";
leaf name {
type string {
length "1..256";
}
description
"Arbitrary name assigned to the rule.";
}
leaf module-name {
type union {
type matchall-string-type;
type string;
}
default "*";
description
"Name of the module associated with this rule.
This leaf matches if it has the value '*', or if the
object being accessed is defined in the module with the
specified module name.";
}
choice rule-type {
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description
"This choice matches if all leafs present in the rule
matches the request. If no leafs are present, the
choice matches all requests.";
case protocol-operation {
leaf rpc-name {
type union {
type matchall-string-type;
type string;
}
description
"This leaf matches if it has the value '*', or if its
value equals the requested RPC operation name.";
}
}
case notification {
leaf notification-name {
type union {
type matchall-string-type;
type string;
}
description
"This leaf matches if it has the value '*', or if its
value equals the requested notification name.";
}
}
case data-node {
leaf path {
type node-instance-identifier;
mandatory true;
description
"Data Node Instance Identifier associated with the data
node controlled by this rule.
Configuration data or state data instance
identifiers start with a top-level data node. A
complete instance identifier is required for this
type of path value.
The special value '/' refers to all possible data
store contents.";
}
}
}
leaf access-operations {
type union {
type matchall-string-type;
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type access-operations-type;
}
default "*";
description
"Access operations associated with this rule.
This leaf matches if it has the value '*', or if the
bit corresponding to the requested operation is set.";
}
leaf action {
type action-type;
mandatory true;
description
"The access control action associated with the
rule. If a rule is determined to match a
particular request, then this object is used
to determine whether to permit or deny the
request.";
}
leaf comment {
type string;
description
"A textual description of the access rule.";
}
}
}
}
}
<CODE ENDS>
Figure 5
3.5. IANA Considerations
There are two actions that are requested of IANA: This document
registers one URI in "The IETF XML Registry". Following the format
in [RFC3688], the following has been registered.
URI: urn:ietf:params:xml:ns:yang:ietf-netconf-acm
Registrant Contact: The IESG.
XML: N/A, the requested URI is an XML namespace.
This document registers one module in the "YANG Module Names"
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registry. Following the format in [RFC6020], the following has been
registered.
name: ietf-netconf-acm
namespace: urn:ietf:params:xml:ns:yang:ietf-netconf-acm
prefix: nacm
reference: RFC XXXX
// RFC Ed.: Replace XXX with actual RFC number
// and remove this note
3.6. Security Considerations
This entire document discusses access control requirements and
mechanisms for restricting NETCONF protocol behavior within a given
session.
Configuration of the access control system is highly sensitive to
system security. A server may choose not to allow any user
configuration to some portions of it, such as the global security
level, or the groups which allowed access to system resources.
This document incorporates the optional use of a "recovery session"
mechanism, which can be used to bypass access control enforcement in
emergencies, such as NACM configuration errors which disable all
access to the server. The configuration and identification of such a
recovery session mechanism are outside the scope of this document.
There is a risk that invocation of non-standard protocol operations
will have undocumented side effects. An administrator needs to
construct access control rules such that the configuration datastore
is protected from such side effects. Also, such protocol operations
SHOULD never be invoked by a session during a "recovery session".
There is a risk that non-standard protocol operations, or even the
standard <get> operation, may return data which "aliases" or "copies"
sensitive data from a different data object. In this case, the
namespace and/or the element name will not match the values for the
sensitive data, which is then fully or partially copied into a
different namespace and/or element. An administrator needs to avoid
using data models which use this practice.
An administrator needs to restrict write access to all configurable
objects within this data model.
If write access is allowed for configuration of access control rules,
then care needs to be taken not to disrupt the access control
enforcement.
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An administrator needs to restrict read access to the following
objects within this data model, which reveal access control
configuration which could be considered sensitive.
o enable-nacm
o read-default
o write-default
o exec-default
o groups
o rules
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4. References
4.1. Normative References
[RFC2119] Bradner, S., "Key words for use in RFCs to Indicate
Requirement Levels", BCP 14, RFC 2119, March 1997.
[RFC3688] Mealling, M., "The IETF XML Registry", BCP 81, RFC 3688,
January 2004.
[RFC5277] Chisholm, S. and H. Trevino, "NETCONF Event
Notifications", RFC 5277, July 2008.
[RFC6020] Bjorklund, M., "YANG - A Data Modeling Language for the
Network Configuration Protocol (NETCONF)", RFC 6020,
October 2010.
[RFC6021] Schoenwaelder, J., "Common YANG Data Types", RFC 6021,
October 2010.
[I-D.ietf-netconf-4741bis]
Enns, R., Bjorklund, M., Schoenwaelder, J., and A.
Bierman, "Network Configuration Protocol (NETCONF)",
draft-ietf-netconf-4741bis-10 (work in progress),
March 2011.
[I-D.ietf-netconf-rfc4742bis]
Wasserman, M. and T. Goddard, "Using the NETCONF
Configuration Protocol over Secure Shell (SSH)",
draft-ietf-netconf-rfc4742bis-08 (work in progress),
March 2011.
4.2. Informative References
[RFC2865] Rigney, C., Willens, S., Rubens, A., and W. Simpson,
"Remote Authentication Dial In User Service (RADIUS)",
RFC 2865, June 2000.
[RFC5607] Nelson, D. and G. Weber, "Remote Authentication Dial-In
User Service (RADIUS) Authorization for Network Access
Server (NAS) Management", RFC 5607, July 2009.
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Appendix A. Usage Examples
The following XML snippets are provided as examples only, to
demonstrate how NACM can be configured to perform some access control
tasks.
A.1. <groups> Example
There needs to be at least one <group> entry in order for any of the
access control rules to be useful.
The following XML shows arbitrary groups, and is not intended to
represent any particular use-case.
<nacm xmlns="urn:ietf:params:xml:ns:yang:ietf-netconf-acm">
<groups>
<group>
<name>admin</name>
<user-name>admin</user-name>
<user-name>andy</user-name>
</group>
<group>
<name>monitor</name>
<user-name>wilma</user-name>
<user-name>bam-bam</user-name>
</group>
<group>
<name>guest</name>
<user-name>guest</user-name>
<user-name>guest@example.com</user-name>
</group>
</groups>
</nacm>
This example shows 3 groups:
1. The "admin" group contains 2 users named "admin" and "andy".
2. The "monitor" group contains 2 users named "wilma" and "bam-bam".
3. The "guest" group contains 2 users named "guest" and
"guest@example.com".
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A.2. Module Rule Example
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
no case in the "rule-type" choice.
<nacm xmlns="urn:ietf:params:xml:ns:yang:ietf-netconf-acm">
<rule-list>
<name>guest</name>
<group>guest</group>
<rule>
<name>mod-1</name>
<module-name>ietf-netconf-monitoring</module-name>
<access-operations>*</access-operations>
<action>deny</action>
<comment>
Do not allow guests any access to the netconf
monitoring information.
</comment>
</rule>
</rule-list>
<rule-list>
<name>monitor example</name>
<group>monitor</group>
<rule>
<name>mod-2</name>
<module-name>ietf-netconf-monitoring</module-name>
<access-operations>read</access-operations>
<action>permit</action>
<comment>
Allow read access to the netconf
monitoring information.
</comment>
</rule>
<rule>
<name>mod-3</name>
<module-name>*</module-name>
<access-operations>exec</access-operations>
<action>permit</action>
<comment>
Allow invocation of the
supported server operations.
</comment>
</rule>
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</rule-list>
<rule-list>
<name>admin example</name>
<group>admin</group>
<rule>
<name>mod-4</name>
<module-name>*</module-name>
<access-operations>*</access-operations>
<action>permit</action>
<comment>
Allow the admin group complete access to all
operations and data.
</comment>
</rule>
</rule-list>
</nacm>
This example shows 4 module rules:
mod-1: This rule prevents the guest group from reading any
monitoring information in the ietf-netconf-monitoring YANG module.
mod-2: This rule allows the monitor group to read the ietf-netconf-
monitoring YANG module.
mod-3: This rule allows the monitor group to invoke any protocol
operation supported by the server.
mod-4: This rule allows the admin group complete access to all
content in the server. No subsequent rule will match for the
admin group, because of this module rule.
A.3. RPC Rule Example
RPC rules are used to control access to a specific protocol
operation.
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<nacm xmlns="urn:ietf:params:xml:ns:yang:ietf-netconf-acm">
<rule-list>
<name>guest</name>
<group>monitor</group>
<group>guest</group>
<rule>
<name>rpc-1</name>
<module-name>ietf-netconf</module-name>
<rpc-name>kill-session</rpc-name>
<access-operations>exec</access-operations>
<action>deny</action>
<comment>
Do not allow the monitor or guest group
to kill another session.
</comment>
</rule>
<rule>
<name>rpc-2</name>
<module-name>ietf-netconf</module-name>
<rpc-name>delete-config</rpc-name>
<access-operations>exec</access-operations>
<action>deny</action>
<comment>
Do not allow monitor or guest group
to delete any configurations.
</comment>
</rule>
</rule-list>
<rule-list>
<name>monitor</name>
<group>monitor</group>
<rule>
<name>rpc-3</name>
<module-name>ietf-netconf</module-name>
<rpc-name>edit-config</rpc-name>
<access-operations>exec</access-operations>
<action>permit</action>
<comment>
Allow the monitor group to edit the configuration.
</comment>
</rule>
</rule-list>
</nacm>
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This example shows 3 protocol operation rules:
rpc-1: This rule prevents the monitor or guest groups from invoking
the NETCONF <kill-session> protocol operation.
rpc-2: This rule prevents the monitor or guest groups from invoking
the NETCONF <delete-config> protocol operation.
rpc-3: This rule allows the monitor group to invoke the NETCONF
<edit-config> protocol operation. This rule will have no real
effect unless the "exec-default" leaf is set to "deny".
A.4. Data Rule Example
Data rules are used to control access to specific (config and non-
config) data nodes within the NETCONF content provided by the server.
<nacm xmlns="urn:ietf:params:xml:ns:yang:ietf-netconf-acm">
<rule-list>
<name>guest rules</name>
<group>guest</group>
<rule>
<name>data-1</name>
<path xmlns:n="urn:ietf:params:xml:ns:yang:ietf-netconf-acm">
/n:nacm
</path>
<access-operations>*</access-operations>
<action>deny</action>
<comment>
Deny the guest group any access to the /nacm data.
</comment>
</rule>
</rule-list>
<rule-list>
<name>monitor rules</name>
<group>monitor</group>
<rule>
<name>data-acme-config</name>
<path xmlns:acme="http://example.com/ns/netconf">
/acme:acme-netconf/acme:config-parameters
</path>
<access-operations>
read create update delete
</access-operations>
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<action>permit</action>
<comment>
Allow the monitor group complete access to the acme
netconf configuration parameters. Showing long form
of 'access-operations' instead of shorthand.
</comment>
</rule>
</rule-list>
<rule-list>
<name>dummy-itf</name>
<group>guest monitor</group>
<rule>
<name>dummy-itf</name>
<path xmlns:acme="http://example.com/ns/itf">
/acme:interfaces/acme:interface[acme:name='dummy']
</path>
<access-operations>read update</access-operations>
<action>permit</action>
<comment>
Allow the monitor and guest groups read
and update access to the dummy interface.
</comment>
</rule>
</rule-list>
<rule-list>
<name>admin rules</name>
<rule>
<name>admin-itf</name>
<path xmlns:acme="http://example.com/ns/itf">
/acme:interfaces/acme:interface
</path>
<access-operations>*</access-operations>
<action>permit</action>
<comment>
Allow admin full access to all acme interfaces.
</comment>
</rule>
</rule-list>
</nacm>
This example shows 4 data rules:
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data-1: This rule denies the guest group any access to the <nacm>
subtree. Note that the default namespace is only applicable
because this subtree is defined in the same namespace as the
<data-rule> element.
data-acme-config: This rule gives the monitor group read-write
access to the acme <config-parameters>.
dummy-itf: This rule gives the monitor and guest groups read-update
access to the acme <interface>. entry named "dummy". This entry
cannot be created or deleted by these groups, just altered.
admin-itf: This rule gives the admin group read-write access to all
acme <interface>. entries. This is an example of an unreachable
rule because the "mod-3" rule already gives the admin group full
access to this data.
A.5. Notification Rule Example
Notification rules are used to control access to a specific
notification event type.
<nacm xmlns="urn:ietf:params:xml:ns:yang:ietf-netconf-acm">
<rule-list>
<name>sys</name>
<group>monitor</group>
<group>guest</group>
<rule>
<name>notif-1</name>
<module-name>acme-system</module-name>
<notification-name>sys-config-change</notification-name>
<access-operations>read</access-operations>
<action>deny</action>
<comment>
Do not allow the guest or monitor groups
to receive config change events.
</comment>
</rule>
</rule-list>
</nacm>
This example shows 1 notification rule:
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notif-1: This rule prevents the monitor or guest groups from
receiving the acme <sys-config-change> event type.
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Appendix B. Change Log
-- RFC Ed.: remove this section before publication.
B.1. 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.2. 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.3. 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.4. 00-01
Updated YANG anf YANG Types references.
Updated module namespace URI to standard format.
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Updated module header meta-data to standard format.
Filled in IANA section.
B.5. 00
Initial version cloned from
draft-bierman-netconf-access-control-02.txt.
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Authors' Addresses
Andy Bierman
Brocade
Email: andy.bierman@brocade.com
Martin Bjorklund
Tail-f Systems
Email: mbj@tail-f.com
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