Internet Engineering Task Force A. Bierman
Internet-Draft InterWorking Labs
Intended status: Standards Track February 25, 2010
Expires: August 29, 2010
Network Configuration Protocol Access Control Model
draft-bierman-netconf-access-control-01
Abstract
The standardization of network configuration interfaces for use with
the NETCONF protocol requires a structured and secure operating
environment, which 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 which meets these requirements.
Status of this Memo
This Internet-Draft is submitted to IETF in full conformance with the
provisions of BCP 78 and BCP 79.
Internet-Drafts are working documents of the Internet Engineering
Task Force (IETF), its areas, and its working groups. Note that
other groups may also distribute working documents as Internet-
Drafts.
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."
The list of current Internet-Drafts can be accessed at
http://www.ietf.org/ietf/1id-abstracts.txt.
The list of Internet-Draft Shadow Directories can be accessed at
http://www.ietf.org/shadow.html.
This Internet-Draft will expire on August 29, 2010.
Copyright Notice
Copyright (c) 2010 IETF Trust and the persons identified as the
document authors. All rights reserved.
Bierman Expires August 29, 2010 [Page 1]
Internet-Draft NACM February 2010
This document is subject to BCP 78 and the IETF Trust's Legal
Provisions Relating to IETF Documents
(http://trustee.ietf.org/license-info) in effect on the date of
publication of this document. Please review these documents
carefully, as they describe your rights and restrictions with respect
to this document. Code Components extracted from this document must
include Simplified BSD License text as described in Section 4.e of
the Trust Legal Provisions and are provided without warranty as
described in the 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. NACM Terms . . . . . . . . . . . . . . . . . . . . . . 5
2. Access Control Requirements . . . . . . . . . . . . . . . . . 6
2.1. Protocol Control Points . . . . . . . . . . . . . . . . . 6
2.2. Simplicity . . . . . . . . . . . . . . . . . . . . . . . . 7
2.3. Procedural Interface . . . . . . . . . . . . . . . . . . . 7
2.4. Database Access . . . . . . . . . . . . . . . . . . . . . 8
2.5. Users and Groups . . . . . . . . . . . . . . . . . . . . . 8
2.6. Maintenance . . . . . . . . . . . . . . . . . . . . . . . 9
2.7. Configuration Capabilities . . . . . . . . . . . . . . . . 9
2.8. Identifying Security Holes . . . . . . . . . . . . . . . . 9
2.9. Data Shadowing . . . . . . . . . . . . . . . . . . . . . . 10
2.10. NETCONF Specific Requirements . . . . . . . . . . . . . . 11
3. NETCONF Access Control Model (NACM) . . . . . . . . . . . . . 12
3.1. Introduction . . . . . . . . . . . . . . . . . . . . . . . 12
3.1.1. Features . . . . . . . . . . . . . . . . . . . . . . . 12
3.1.2. External Dependencies . . . . . . . . . . . . . . . . 13
3.1.3. Message Processing Model . . . . . . . . . . . . . . . 13
3.2. Model Components . . . . . . . . . . . . . . . . . . . . . 15
3.2.1. Users . . . . . . . . . . . . . . . . . . . . . . . . 15
3.2.2. Groups . . . . . . . . . . . . . . . . . . . . . . . . 16
3.2.3. Sessions . . . . . . . . . . . . . . . . . . . . . . . 16
3.2.4. Access Permissions . . . . . . . . . . . . . . . . . . 16
3.2.5. Global Enforcement Controls . . . . . . . . . . . . . 17
3.2.6. Access Control Rules . . . . . . . . . . . . . . . . . 17
3.3. Access Control Enforcement Procedures . . . . . . . . . . 17
3.3.1. Initial Operation . . . . . . . . . . . . . . . . . . 17
3.3.2. Session Establishment . . . . . . . . . . . . . . . . 18
3.3.3. 'access-denied' Error Handling . . . . . . . . . . . . 18
3.3.4. Incoming RPC Message Validation . . . . . . . . . . . 18
3.3.5. Data Node Access Validation . . . . . . . . . . . . . 21
3.3.6. Outgoing <rpc-reply> Authorization . . . . . . . . . . 23
Bierman Expires August 29, 2010 [Page 2]
Internet-Draft NACM February 2010
3.3.7. Outgoing <notification> Authorization . . . . . . . . 23
3.4. Data Model Definitions . . . . . . . . . . . . . . . . . . 26
3.4.1. High Level Procedures . . . . . . . . . . . . . . . . 26
3.4.2. Data Organization . . . . . . . . . . . . . . . . . . 26
3.4.3. YANG Module . . . . . . . . . . . . . . . . . . . . . 27
3.5. IANA Considerations . . . . . . . . . . . . . . . . . . . 36
3.6. Security Considerations . . . . . . . . . . . . . . . . . 36
4. Normative References . . . . . . . . . . . . . . . . . . . . . 39
Appendix A. Usage Examples . . . . . . . . . . . . . . . . . . . 40
A.1. <groups> Example . . . . . . . . . . . . . . . . . . . . . 40
A.2. <module-rule> Example . . . . . . . . . . . . . . . . . . 41
A.3. <rpc-rule> Example . . . . . . . . . . . . . . . . . . . . 42
A.4. <data-rule> Example . . . . . . . . . . . . . . . . . . . 43
A.5. <notification-rule> Example . . . . . . . . . . . . . . . 44
Appendix B. Open Issues . . . . . . . . . . . . . . . . . . . . . 46
Author's Address . . . . . . . . . . . . . . . . . . . . . . . . . 47
Bierman Expires August 29, 2010 [Page 3]
Internet-Draft NACM February 2010
1. Introduction
The NETCONF protocol does not provide any standard mechanisms to
restrict the operations and content that each user is authorized to
use. Any user that is able to start a NETCONF session is allowed to
access every protocol operation, all database content, and all
notification content.
There is a need for the inter-operable management of the controlled
access to operator selected portions of the available NETCONF content
within a particular server.
This document addresses NETCONF protocol access control mechanisms
for the RPC, Operations, and Content layers, as defined in [RFC4741],
and [RFC5277]. It contains three main sections:
1. Access Control Requirements
2. NETCONF Access Control Model (NACM)
3. YANG Data Model (nacm.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 RFC 4741 and are not redefined
here:
o client
o operation
o RPC operation
o server
o session
o user
Bierman Expires August 29, 2010 [Page 4]
Internet-Draft NACM February 2010
1.1.3. NACM Terms
The following terms are used throughout this documentation:
access control: A security feature provided by the NETCONF server,
which 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 should be permitted or
denied.
superuser: The special administrative user account which is given
unlimited NETCONF access, and is exempt from all access control
enforcement.
Bierman Expires August 29, 2010 [Page 5]
Internet-Draft NACM February 2010
2. Access Control Requirements
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 must be protected at several
conceptual control points.
+-------------+ +-------------+
client | RPC | | prune | client
request --> | operation | | restricted | ---> reply
| allowed? | | <rpc-reply> |
+-------------+ | nodes? |
| +-------------+
| if any database 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:
RPC operation: Configurable permission to invoke specific RPC
operations is required. Wildcard or multiple target mechanisms to
reduce configuration and effort are also required.
NETCONF database: Configurable permission to read and/or alter
specific data nodes within any conceptual database is required.
Wildcard or multiple target mechanisms to reduce configuration and
effort are also required.
Bierman Expires August 29, 2010 [Page 6]
Internet-Draft NACM February 2010
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
should be easy to do simple things, and hard to do complex things,
instead of hard to do everything.
Configuration of the access control system must be simple to use.
Simple and common tasks should be easy to configure, and require
little expertise or domain-specific knowledge. Complex tasks should
be 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 RPC operation invocation, all conceptual database
access, and all NETCONF session output.
Protocol access should be defined with a small and familiar set of
permissions such as 'read', 'write', and 'execute'.
Default access control policy needs to be as secure as possible.
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, including vendor-specific
'actions'. 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 RPC operations is not required. However, since
this cannot always be avoided, then it should be possible to control
access to specific input parameters. If a restricted parameter is
Bierman Expires August 29, 2010 [Page 7]
Internet-Draft NACM February 2010
used, then the request is rejected with an 'access-denied' error.
2.4. Database Access
It must be possible control access to specific nodes and sub-trees
within the conceptual NETCONF database.
In order for a user to obtain access to a particular database node,
the user must be authorized to have the same requested access to the
specified node, and all of its ancestors.
The same access control rules apply to all conceptual databases. For
example, the candidate configuration or the running configuration.
Only the standard NETCONF databases (candidate, running, and startup)
are controlled y the ACM. Local or remote files or databases
accessed via the <url> parameter are optional to support.
The non-volatile startup configuration needs to be loaded into the
running configuration without applying any access control rules.
This operation is conceptually performed by the superuser account.
Only the superuser should be able to alter the factory-default access
control rules.
Read operations for restricted configuration data, either directly or
via wildcard access, are silently omitted from the <rpc-reply>.
Create, merge, replace, and delete operations on a database node for
which the user does not have 'write' access permission is rejected
with an 'access-denied' error. The specific restricted database
nodes must not be exposed in any <rpc-error> elements within the
reply.
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.
A configurable superuser account is needed which bypasses all access
control rules. This is needed in case the access control rules are
mis-configured, and all access is denied.
The ACM must support the concept of administrative groups, to support
the well-established distinction between a root account and other
Bierman Expires August 29, 2010 [Page 8]
Internet-Draft NACM February 2010
types of less-privileged conceptual user accounts. These groups must
be configurable by the operator.
2.6. Maintenance
It should be possible to disable part or all of the access control
model without deleting any configuration. By default, only the
'superuser' should be able to perform this task.
It should be possible to configure a 'superuser' account so that all
access control is disabled for just this user. This allows the
access control rules to always be modified without completely
disabling access control for all users.
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 XML data model, suitable for use with the <edit-config>
operation must be available for this purpose.
All standard access control parameters must persist in non-volatile
storage, and be used upon the next reboot.
Access control rules to restrict operations on specific sub-trees
within the configuration database must be supported. Existing
mechanisms should be used to identify the sub-tree(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 commands in NETCONF, not
just data and notifications.
It is customary 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 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 must study
some more RFC text, and determine out how to close the security
hole(s).
Bierman Expires August 29, 2010 [Page 9]
Internet-Draft NACM February 2010
o The ACM on each server must 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
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 should be able to use machine-readable
statements to identity NETCONF content which should be protected by
default. This will allow client and server tools to automatically
close data-model specific security holes by requiring 'superuser'
access unless an access control rule is explicitly configured to
allow 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 YANG leafref data type is used, then this data shadowing can
be detected by applications (and the server stack), and prevented.
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 insure than unauthorized access to its
conceptual databases and non-configuration data nodes is prevented.
However, if a NETCONF operation accesses device instrumentation
instead of the protected data node, then this access will not be
protected.
It is beyond the scope of this document to define access control
Bierman Expires August 29, 2010 [Page 10]
Internet-Draft NACM February 2010
enforcement procedures for underlying device instrumentation that may
exist to support the NETCONF server operation. An operator must
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 database access request, even
for proprietary operations.
A session must always be authorized to invoke the <close-session>
operation, defined in [RFC4741].
A session 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.
Within a single server, the module namespace URI associated with a
specific module name string must persist across a reboot, and never
change, once assigned.
Bierman Expires August 29, 2010 [Page 11]
Internet-Draft NACM February 2010
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 Very simple access control rules configuration data model which is
easy to use.
o The concept of a 'superuser' type of account is supported, but
configuration of user accounts is beyond the scope of this
document. The server must be able to determine if a superuser
account is available, and if so, the actual user name for this
account. A session associated with the superuser account will
bypass all access control enforcement.
o A simple and familiar set of permissions is used:
read: If granted, then the session is authorized to receive the
associated data within an <rpc-reply> or <notification>
message.
write: If granted, then the session is authorized to alter the
associated data node.
exec: If granted, then the session is authorized to invoke the
associated RPC operation.
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 or downgraded during operation, in
order to debug operational problems.
Bierman Expires August 29, 2010 [Page 12]
Internet-Draft NACM February 2010
o Access control rule are simple to configure.
o The number of denied RPC operation requests and denied database
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, or child
nodes within specific RPC input, RPC output, and notification
event type content.
3.1.2. External Dependencies
The NETCONF [RFC4741] protocol is used for all management purposes
within this document. The server must support the features
identified by the 'NETCONF-base' capability. It is expected that the
mandatory transport mapping NETCONF Over SSH [RFC4742] 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 [I-D.ietf-netmod-yang] is used to
define the NETCONF data models specified in this document. The YANG
instance-identifier data type can be used to configure data-node-
specific access control rules.
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.
Bierman Expires August 29, 2010 [Page 13]
Internet-Draft NACM February 2010
+-------------------------+
| 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 |
| database | | instrumentation |
| | <--- | |
+---------------+ +-----------------+
Figure 2
The follow 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 user identity for the session is the
'superuser'.
Bierman Expires August 29, 2010 [Page 14]
Internet-Draft NACM February 2010
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 database or conceptual state data is accessed
by the RPC operation, then the configuration access must be
authorized first. If the session is authorized to perform the
requested operation on the requested data, then processing
continues.
The follow 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 identity, which 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.
Configuration of users is beyond the scope of this document.
The user name string is usually derived from the transport layer
during session establishment. A server is required to have an
authenticated user name for a session before <rpc> requests will be
accepted. Otherwise all requests must be rejected with an 'access-
denied' error-tag value.
The server should support a 'superuser' administrative user account,
which will bypass all access control enforcement. This is useful for
restricting initial access and repairing a broken access control
configuration. This account may be configurable to use a specific
user, or disabled completely. Some systems have factory-selected
superuser account names. There is no need to standardize the exact
user name for the superuser account. If no such account, then all
NETCONF access will be controlled.
Bierman Expires August 29, 2010 [Page 15]
Internet-Draft NACM February 2010
3.2.2. Groups
Access to a specific NETCONF protocol mechanism is granted to a
session, associated with a group, not a user.
A group is identified by its YANG group identity, which must use the
'nacm-groups' identity as its base.
All group names must be unique within the server.
A group member is identified by a user name string.
The same user may be configured in multiple groups.
The server should support the 3 default group identities defined in
this document (admin, monitor, guest), however these roles are just
unique identities, provided for operator convenience. There is no
standard behavior defined for each group identity. That is up to the
operator who configures the groups.
3.2.3. Sessions
A session is simply a NETCONF session, which is the entity which is
granted access to specific NETCONF protocol mechanisms.
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 role or
group. The same access permissions should stay in affect for the
lifetime of a session.
The access control model treats RPC operation execution separately
from configuration database access and outgoing messages:
read: Read access to conceptual server data, <rpc-reply> and
<notification> content.
write: Write access to any configuration database.
exec: Permission to invoke an RPC operation.
Bierman Expires August 29, 2010 [Page 16]
Internet-Draft NACM February 2010
3.2.5. Global Enforcement Controls
A global on/off switch is provided to enable or disable all access
control enforcement.
An on/off switch is provided to enable or disable default access to
invoke RPC operations.
An on/off switch is provided to enable or disable default permission
to receive data in replies and notifications.
An on/off switch is provided to enable or disable default access to
alter configuration data.
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.
RPC operation rule: Controls access for a specific RPC 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 must 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 must
also 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 not, a server
should not allow any write access to any session role except
'superuser' type of account in this state.
There is no requirement to enforce access control rules before or
while the non-volatile configuration data is processed and loaded
Bierman Expires August 29, 2010 [Page 17]
Internet-Draft NACM February 2010
into the running configuration.
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 identity has been
authenticated, a NETCONF server will enforce the access control
rules, based on the supplied user identity 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 an RPC operation
or a request to perform a particular operation on the configuration
database.
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.
Bierman Expires August 29, 2010 [Page 18]
Internet-Draft NACM February 2010
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 |
| database |
+----------------------+
Figure 3
Access control begins with the message dispatcher. Only well-formed
XML messages should be processed by the server.
A server should not allow access to configuration databases through
any top level element except the <rpc> element in the NETCONF-base
namespace. If it does, the server should still enforce access
control to configuration data, even if the access is from some
mechanism outside the standard protocol operations.
After the server validates the <rpc> element, and determines the
namespace URI and the element name of the RPC operation being
requested, the RPC access control enforcer verifies that the session
is authorized to invoke the RPC operation.
Bierman Expires August 29, 2010 [Page 19]
Internet-Draft NACM February 2010
The RPC operation is authorized by following these steps:
1. If the <enable-nacm> parameter is set to 'false', then the RPC
operation is permitted.
2. If the session is associated with the 'superuser' account, then
the RPC operation is permitted.
3. If the requested operation is the NETCONF <close-session>
operation, then the RPC operation is permitted.
4. Check all the <group> entries for ones that contain a <user-
name> entry that matches the user name for the session making
the request.
5. If no groups are found:
* If the requested RPC operation is associated with a YANG
module advertised in the server capabilities, and the rpc
statement contains a nacm:secure or nacm:very-secure
extension, then the RPC operation is denied.
* If the <exec-default> parameter is set to 'permit', then
permit the RPC operation, otherwise deny the request.
6. Check if there are any matching <rpc-rule> entries for the
requested RPC operation. Any matching rules are processing in
user-defined order, in case there are multiple <rpc-rule>
entries for the requested RPC operation.
7. If an <rpc-rule> entry is found, then check the <allowed-rights>
bits field for the entry, otherwise continue. If the 'exec' bit
is present in the <allowed-rights> bits field then the RPC
operation is permitted, otherwise it is denied.
8. Check if there are any matching <module-rule> entries for the
same module as the requested RPC operation. Any matching rules
are processing in user-defined order, in case there are multiple
<module-rule> entries for the module containing the requested
RPC operation.
9. If a <module-rule> entry is found, then check the <allowed-
rights> bits field for the entry, otherwise continue. If the
'exec' bit is present in the <allowed-rights> bits field then
the RPC operation is permitted, otherwise it is denied.
10. If the requested operation is identified an a nacm:secure or
nacm:very-secure RPC operation, then the RPC operation is
Bierman Expires August 29, 2010 [Page 20]
Internet-Draft NACM February 2010
denied.
11. If the <exec-default> parameter is set to 'permit', then permit
the RPC operation, otherwise deny the request.
If the session is not authorized to invoke the RPC operation then an
<rpc-error> is generated with the following information:
error-tag: access-denied
error-path: /rpc/method-QName, where 'method-QName' is a qualified
name identifying the actual RPC operation name. For example,
'/rpc/edit-config' represents the <edit-config> operation in the
NETCONF base namespace..
If the configuration database is accessed, either directly or as a
side effect of the RPC operation, then the server must intercept the
operation and make sure the session is authorized to perform the
requested operation on the specified data.
3.3.5. Data Node Access Validation
If a data node within a configuration database is accessed, or a
conceptual non-configuration node is accessed, then the server must
ensure that the client session is authorized to perform the requested
operation (read or write) on the specified data node.
The data node access request is authorized by following these steps:
1. If the <enable-nacm> parameter is set to 'false', then the data
node access request is permitted.
2. If the session is associated with the 'superuser' account, then
the data node access request is permitted.
3. Check all the <group> entries for ones that contain a <user-
name> entry that matches the user name for the session making
the request.
4. If no groups are found:
* If the requested data node is associated with a YANG module
advertised in the server capabilities, and the data
definition statements (or any of its ancestors) contains a
nacm:secure or nacm:very-secure extension, then the data node
access request is denied.
Bierman Expires August 29, 2010 [Page 21]
Internet-Draft NACM February 2010
* For a read request, if the <read-default> parameter is set to
'permit', then permit the data node access request, otherwise
deny the request.
* For a write request, if the <write-default> parameter is set
to 'permit', then permit the data node access request,
otherwise deny the request.
5. Check if there are any matching <data-rule> entries for the
requested data node access request. Any matching rules are
processing in user-defined order, in case there are multiple
<data-rule> entries for the requested data node.
6. If an <data-rule> entry is found, then check the <allowed-
rights> bits field for the entry, otherwise continue.
1. For a read operation, if the 'read' bit is present in the
<allowed-rights> bits field then the request is permitted,
otherwise it is denied.
2. For a write operation, if the 'write' bit is present in the
<allowed-rights> bits field then the request is permitted,
otherwise it is denied.
7. Check if there are any matching <module-rule> entries for the
same module as the requested data node. Any matching rules are
processing in user-defined order, in case there are multiple
<module-rule> entries for the module containing the requested
data node.
8. If a <module-rule> entry is found, then check the <allowed-
rights> bits field for the entry, otherwise continue.
1. For a read operation, if the 'read' bit is present in the
<allowed-rights> bits field then the request is permitted,
otherwise it is denied.
2. For a write operation, if the 'write' bit is present in the
<allowed-rights> bits field then the request is permitted,
otherwise it is denied.
9. For a read request, if the requested data node is identified an
a nacm:very-secure definition, then the data node access request
is denied.
10. For a write request, if the requested data node is identified an
a nacm:secure or nacm:very-secure definition, then the data node
access request is denied.
Bierman Expires August 29, 2010 [Page 22]
Internet-Draft NACM February 2010
11. For a read request, if the <read-default> parameter is set to
'permit', then permit the data node access request, otherwise
deny the request.
12. For a write request, if the <write-default> parameter is set to
'permit', then permit the data node access request, otherwise
deny the request.
3.3.6. Outgoing <rpc-reply> Authorization
The <rpc-reply> message should be checked by the server to make sure
no unauthorized data is contained within it. If so, the restricted
data must be removed from the message before it is sent to the
client.
Configuration of access control rules exclusively for the RPC output
section, for an <rpc-reply> message that does not return data from a
conceptual database or non-configuration data suitable for retrieval
with the <get> operation is outside the scope of this document. For
RPC operations which do not access any data nodes, then any client
authorized to invoke the RPC operation is also authorized to receive
the <rpc-reply> for that RPC operation.
3.3.7. Outgoing <notification> Authorization
The <notification> message should be checked by the server to make
sure no unauthorized data is contained within it. If so, the
restricted data must be removed from the message before it is sent to
the client.
Configuration of access control rules specifically for descendent
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.
Bierman Expires August 29, 2010 [Page 23]
Internet-Draft NACM February 2010
NETCONF server
+------------+
| XML |
| message |
| generator |
+------------+
^
|
+----------------+
| <notification> |
| generator |
+----------------+
^
|
+=================+
| <notification> |
| access control |
| <eventType> |
+=================+
^
|
+------------------------+
| server instrumentation |
+------------------------+
| ^
V |
+----------------------+
| configuration |
| database |
+----------------------+
Figure 4
The generation of a notification event for a specific subscription is
authorized by following these steps:
1. If the <enable-nacm> parameter is set to 'false', then the
notification event is permitted.
2. If the session is associated with the 'superuser' account, then
the notification event is permitted.
3. If the requested operation is the NETCONF <replayComplete> or
<notificationComplete> event type, then the notification event
is permitted.
Bierman Expires August 29, 2010 [Page 24]
Internet-Draft NACM February 2010
4. Check all the <group> entries for ones that contain a <user-
name> entry that matches the user name for the session that
started the notification subscription.
5. If no groups are found:
* If the requested notification is associated with a YANG
module advertised in the server capabilities, and the
notification statement contains a nacm:secure or nacm:very-
secure extension, then the notification event is dropped for
the associated subscription.
* If the <read-default> parameter is set to 'permit', then
permit the notification event, otherwise drop this event type
for the associated subscription.
6. Check if there are any matching <notification-rule> entries for
the specific notification event type being delivered to the
subscription. Any matching rules are processing in user-defined
order, in case there are multiple <notification-rule> entries
for the requested notification event type.
7. If a <notification-rule> entry is found, then check the
<allowed-rights> bits field for the entry, otherwise continue.
If the 'read' bit is present in the <allowed-rights> bits field
then the notification event type is permitted, otherwise it is
dropped for the associated subscription.
8. Check if there are any matching <module-rule> entries for the
same module as the notification event type. Any matching rules
are processing in user-defined order, in case there are multiple
<module-rule> entries for the module containing the notification
event type.
9. If a <module-rule> entry is found, then check the <allowed-
rights> bits field for the entry, otherwise continue. If the
'read' bit is present in the <allowed-rights> bits field then
the notification event type is permitted, otherwise it is
dropped for the associated subscription.
10. If the requested event type is identified an a nacm:very-secure
notification definition, then the notification event type is
denied.
11. If the <read-default> parameter is set to 'permit', then permit
the notification event type, otherwise it is dropped for the
associated subscription.`<
Bierman Expires August 29, 2010 [Page 25]
Internet-Draft NACM February 2010
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. High Level Procedures
There are some high level management procedures that an administrator
needs to consider before using this access control model:
1. Configure the global settings.
2. Configure one or more user groups.
3. Configure zero or more access control rules for specific modules.
4. Configure zero or more access control rules for specific RPC
operations.
5. Configure zero or more access control rules for data node access.
6. Configure zero or more access control rules for notification
event type access.
3.4.2. Data Organization
The top-level element is called <nacm>, and it is defined the 'nacm'
module 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 RPC
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.
Bierman Expires August 29, 2010 [Page 26]
Internet-Draft NACM February 2010
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.
container <groups>: Configures the groups used within the access
control system.
list <group>: A list of user names belonging to the same
administrative group.
container <rules>: Configures the access control rules used within
the server.
list <module-rule>: Configures the access control rules for a
specific module.
list <rpc-rule>: Configures the access control rules for RPC
operation invocation.
list <data-rule>: Configures the access control rules for
configuration database access.
list <notification-rule>: Configures the access control rules for
controlling delivery of <notification> events.
3.4.3. YANG Module
The following YANG module is provided to specify the normative
NETCONF content that must by supported by the server.
<CODE BEGINS> file="nacm.yang"
module nacm {
namespace "file://draft-bierman-netconf-access-control-01.txt";
prefix "nacm";
import ietf-yang-types { prefix yang; }
organization "Netconf Central, Inc.";
contact "Andy Bierman <andy@netconfcentral.org>.";
description
"NETCONF Server Access Control Model";
Bierman Expires August 29, 2010 [Page 27]
Internet-Draft NACM February 2010
revision 2010-02-21 {
description
"Initial version (work-in-progress).";
}
typedef nacm-user-name {
description "General Purpose User Name string.";
type string {
length "1..64";
pattern '[a-z,A-Z,_][a-z,A-Z,0-9,\-,_,@,.]{0,63}';
}
}
typedef nacm-rights {
description
"NETCONF Access Rights";
type bits {
bit read {
description
"Read access allowed to all specified data.
Any protocol operation or notification that
returns data to an application is a read
operation.";
}
bit write {
description
"Write access allowed to all specified data.
Any protocol operation that alters a database
is a write operation.";
}
bit exec {
description
"Execution access to the specified RPC operation.
Any RPC operation invocation is an exec operation.";
}
}
}
typedef nacm-group {
description
"Type of administrative group that can be
assigned to the user, and specified in
an access control rule.
The identityref data type is used to allow as
many groups to be added as needed. There are
Bierman Expires August 29, 2010 [Page 28]
Internet-Draft NACM February 2010
no standard semantics for each identity.
It simply represents a unique group name.";
type identityref {
base nacm-groups;
}
}
typedef nacm-action {
description
"Action taken by the server when a particular
rule matches.";
type enumeration {
enum permit {
description "Requested action is permitted.";
}
enum deny {
description "Requested action is denied.";
}
}
}
typedef schema-instance-identifier {
description
"Path expression used to represent a special
schema-instance identifier string.
A schema-instance-identifier value string 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 schema-instance-identifier
represents all possible server instances for that key.";
type string;
}
extension secure {
description
"Used to indicate that the data model node
represents a sensitive security system parameter.
If present, the NETCONF server will only allow
the designated 'superuser' to have write or execute
default nacm-rights for the node. An explicit access
control rule is required for all other users.
The 'secure' extension may appear within a data, rpc,
or notification node definition. It is ignored
Bierman Expires August 29, 2010 [Page 29]
Internet-Draft NACM February 2010
otherwise.";
}
extension very-secure {
description
"Used to indicate that the data model node
controls a very sensitive security system parameter.
If present, the NETCONF server will only allow
the designated 'superuser' to have read, write, or execute
default nacm-rights for the node. An explicit access
control rule is required for all other users.
The 'very-secure' extension may appear within a data, rpc,
or notification node definition. It is ignored
otherwise.";
}
identity nacm-groups {
description
"Root of all NETCONF Administrative Groups";
}
identity admin {
description
"Example Administrator group.";
base nacm-groups;
}
identity monitor {
description
"Example Monitoring group.";
base nacm-groups;
}
identity guest {
description
"Example Guest group.";
base nacm-groups;
}
container nacm {
nacm:very-secure;
description
"Parameters for NETCONF Access Control Model.";
presence
Bierman Expires August 29, 2010 [Page 30]
Internet-Draft NACM February 2010
"An empty nacm container indicates that the
NACM service is running, and possibly using
all default parameters.";
leaf enable-nacm {
description
"Enable or disable all NETCONF access control
enforcement. If 'true', then enforcement
is enabled. If 'false', then enforcement
is disabled.";
type boolean;
default true;
}
leaf read-default {
description
"Controls whether read access is granted if
no appropriate rule is found for a
particular read request.";
type nacm-action;
default "permit";
}
leaf write-default {
description
"Controls whether write access is granted if
no appropriate rule is found for a
particular write request.";
type nacm-action;
default "deny";
}
leaf exec-default {
description
"Controls whether exec access is granted if
no appropriate rule is found for a
particular RPC operation request.";
type nacm-action;
default "permit";
}
leaf denied-rpcs {
description
"Number of times an RPC operation request was denied";
type yang:zero-based-counter32;
config false;
}
Bierman Expires August 29, 2010 [Page 31]
Internet-Draft NACM February 2010
leaf denied-data-writes {
description
"Number of times a request to alter a data node
was denied.";
type yang:zero-based-counter32;
config false;
}
container groups {
description
"NACM Group Table";
list group {
description "One NACM Group Entry";
key group-identity;
leaf group-identity {
description
"Group identity associated with this entry.";
type nacm-group;
}
leaf-list user-name {
description
"Each entry identifies the user name of
a member of the group associated with
this entry.";
type nacm-user-name;
}
}
}
container rules {
description
"NETCONF Access Control Rules.";
grouping common-rule-parms {
leaf rule-name {
description
"Arbitrary name assigned to the
access control rule.";
type string {
length "1..1023";
}
}
leaf allowed-rights {
Bierman Expires August 29, 2010 [Page 32]
Internet-Draft NACM February 2010
description
"List of access rights granted to
specified administrative groups for the
content specified by the associated path.";
type nacm-rights;
mandatory true;
}
leaf-list allowed-group {
description
"List of administrative groups which will be
assigned the associated access rights
for the content specified by the associated
path.";
type nacm-group;
min-elements 1;
}
leaf comment {
description
"A textual description of the access rule.";
type string {
length "0..4095";
}
}
}
list module-rule {
description
"One Module Access Rule.
Rules are processed in user-defined order.
A module rule is considered a match if
the XML namespace for the specified module
name matches the XML namespace used within
a NETCONF PDU, and the administrative group
associated with the requesting session is
specified in the 'allowed-group' leaf-list.";
ordered-by user;
key "module-name rule-name";
leaf module-name {
description
"Name of the module associated with
this rule.";
type string {
length "1..max";
Bierman Expires August 29, 2010 [Page 33]
Internet-Draft NACM February 2010
}
}
uses common-rule-parms;
}
list rpc-rule {
description
"One RPC Operation Access Rule.
Rules are processed in user-defined order.
An RPC rule is considered a match if
the module name of the requested RPC
operation matches 'rpc-module-name',
the requested RPC operation matches
'rpc-name', and an administrative group
associated with the session user
is listed in the 'allowed-group'
leaf-list";
ordered-by user;
key "rpc-module-name
rpc-name
rule-name";
leaf rpc-module-name {
description
"Name of the module defining this
RPC operation.";
type string {
length "1..max";
}
}
leaf rpc-name {
description
"Name of the RPC operation.";
type string {
length "1..max";
}
}
uses common-rule-parms;
}
list data-rule {
description
"One Data Access Control Rule.
Bierman Expires August 29, 2010 [Page 34]
Internet-Draft NACM February 2010
Rules are processed in user-defined order.
A data rule is considered to match when
the path expression identifies
the same node that is being accessed
in the NETCONF database, and the administrative
group associated with the session is identified
in the 'allowed-group' leaf-list.";
key "rule-name";
ordered-by user;
leaf path {
description
"Schema 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 database contents.";
type schema-instance-identifier;
mandatory true;
}
uses common-rule-parms;
}
list notification-rule {
description
"One Notification Access Rule.
A notification is considered a match if
the module name of the requested
event type matches 'notification-module-name',
the requested event type matches the
'notification-name', and the administrative group
associated with the requesting session
is listed in the 'allowed-group' leaf-list.";
ordered-by user;
key "notification-module-name
notification-name
Bierman Expires August 29, 2010 [Page 35]
Internet-Draft NACM February 2010
rule-name";
leaf notification-module-name {
description
"Name of the module defining this
notification event type.";
type string {
length "1..max";
}
}
leaf notification-name {
description
"Name of the notification event.";
type string {
length "1..max";
}
}
uses common-rule-parms;
}
}
}
}
<CODE ENDS>
Figure 5
3.5. IANA Considerations
There are two actions that are requested of IANA:
1. register data model schema namespace URI (TBD)
2. register data model name ('nacm')
3.6. Security Considerations
This entire document discusses access control requirements and
mechanisms for restricting NETCONF protocol behavior within a given
session.
Bierman Expires August 29, 2010 [Page 36]
Internet-Draft NACM February 2010
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 superuser account,
which can be used to bypass access control enforcement.
Configuration user accounts is outside the scope of this document,
however it is suggested that the 'root' account not be used for
NETCONF over SSH servers, because 'root' SSH logins should be
disabled in the SSH server.
If the server chooses to allow user configuration of the access
control system, then only sessions using the 'superuser'
administrative user should be allowed to have write access to the
data model.
If the server chooses to allow user retrieval of the access control
system configuration, then only sessions using the 'superuser'
administrative user should be allowed to have read access to the data
model.
There is a risk that invocation of non-standard RPC operations will
have undocumented side effects. An administrator should construct
access control rules such that the configuration database is
protected from such side effects. Also, such RPC operations should
never be invoked by a session using the 'superuser' administrative
user.
There is a risk that non-standard RPC 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 should avoid
using data models which use this practice.
An administrator should restrict write access to all configurable
objects within this data model. It is suggested that only sessions
using the 'superuser' administrative role be permitted to configure
the data model defined in this document.
If write access is allowed for configuration of access control rules,
then care must be taken not to disrupt the access control
enforcement.
An administrator should restrict read access to the following objects
within this data model, which reveal access control configuration
Bierman Expires August 29, 2010 [Page 37]
Internet-Draft NACM February 2010
which could be considered sensitive.
o enable-nacm
o read-default
o write-default
o exec-default
o groups
o rules
Bierman Expires August 29, 2010 [Page 38]
Internet-Draft NACM February 2010
4. Normative References
[RFC2119] Bradner, S., "Key words for use in RFCs to Indicate
Requirement Levels", BCP 14, RFC 2119, March 1997.
[RFC4741] Enns, R., "NETCONF Configuration Protocol", RFC 4741,
December 2006.
[RFC4742] Wasserman, M. and T. Goddard, "Using the NETCONF
Configuration Protocol over Secure SHell (SSH)", RFC 4742,
December 2006.
[RFC5277] Chisholm, S. and H. Trevino, "NETCONF Event
Notifications", RFC 5277, July 2008.
[W3C.REC-xml]
Bray, T., Paoli, J., Sperberg-McQueen, C., and E. Maler,
"Extensible Markup Language (XML) 1.0 (2nd ed)", W3C REC-
xml, October 2000, <http://www.w3.org/TR/REC-xml>.
[I-D.ietf-netmod-yang]
Bjorklund, M., "YANG - A data modeling language for
NETCONF", draft-ietf-netmod-yang-11 (work in progress),
February 2010.
[I-D.ietf-netmod-yang-types]
Schoenwaelder, J., "Common YANG Data Types",
draft-ietf-netmod-yang-types-07 (work in progress),
February 2010.
Bierman Expires August 29, 2010 [Page 39]
Internet-Draft NACM February 2010
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 must 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.
<nc:config xmlns:nc="urn:ietf:params:xml:ns:netconf:base:1.0">
<nacm:nacm
xmlns:nacm="file://draft-bierman-netconf-access-control-01.txt">
<nacm:groups>
<nacm:group>
<nacm:group-identity>nacm:admin</nacm:group-identity>
<nacm:user-name>admin</nacm:user-name>
<nacm:user-name>andy</nacm:user-name>
</nacm:group>
<nacm:group>
<nacm:group-identity>nacm:monitor</nacm:group-identity>
<nacm:user-name>wilma</nacm:user-name>
<nacm:user-name>bam-bam</nacm:user-name>
</nacm:group>
<nacm:group>
<nacm:group-identity>nacm:guest</nacm:group-identity>
<nacm:user-name>guest</nacm:user-name>
<nacm:user-name>guest@example.com</nacm:user-name>
</nacm:group>
</nacm:groups>
</nc:config>
</nacm:nacm>
This example shows 3 groups:
1. The nacm:admin group contains 2 users named 'admin' and 'andy'.
2. The nacm:monitor group contains 2 users named 'wilma' and 'bam-
bam'.
3. The nacm:guest group contains 2 users named 'guest' and
'guest@example.com'.
Bierman Expires August 29, 2010 [Page 40]
Internet-Draft NACM February 2010
A.2. <module-rule> Example
Module rules are used to control access to all the content defined in
a specific module. These rules are checked after none of the
specific rules (i.e., rpc-rule, data-rule, or notification-rule)
matched the current access request.
<nc:config xmlns:nc="urn:ietf:params:xml:ns:netconf:base:1.0">
<nacm:nacm
xmlns:nacm="file://draft-bierman-netconf-access-control-01.txt">
<nacm:rules>
<nacm:module-rule>
<nacm:module-name>
ietf-netconf-monitoring
</nacm:module-name>
<nacm:rule-name>1</nacm:rule-name>
<nacm:allowed-rights>read</nacm:allowed-rights>
<nacm:allowed-group>nacm:admin</nacm:allowed-group>
<nacm:allowed-group>nacm:monitor</nacm:allowed-group>
<nacm:comment>
do not allow guests to read the netconf information
</nacm:comment>
</nacm:module-rule>
<nacm:module-rule>
<nacm:module-name>ietf-netconf</nacm:module-name>
<nacm:rule-name>1</nacm:rule-name>
<nacm:allowed-rights>read write exec</nacm:allowed-rights>
<nacm:allowed-group>nacm:admin</nacm:allowed-group>
<nacm:comment>
allow admin complete access to the standard operations
</nacm:comment>
</nacm:module-rule>
</nacm:rules>
</nc:config>
</nacm:nacm>
This example shows 2 module rules:
1. This rule allows the admin and monitor groups (but not the guest
group) to read the <netconf-state> sub-tree, which is defined in
the ietf-netconf-monitoring YANG module.
2. This rule allows complete access to the ietf-netconf module for
the admin group.
Bierman Expires August 29, 2010 [Page 41]
Internet-Draft NACM February 2010
A.3. <rpc-rule> Example
RPC rules are used to control access to a specific RPC operation.
<nc:config xmlns:nc="urn:ietf:params:xml:ns:netconf:base:1.0">
<nacm:nacm
xmlns:nacm="file://draft-bierman-netconf-access-control-01.txt">
<nacm:rules>
<nacm:rpc-rule>
<nacm:rpc-module-name>
ietf-netconf
</nacm:rpc-module-name>
<nacm:rpc-name>
kill-session
</nacm:rpc-name>
<nacm:rule-name>1</nacm:rule-name>
<nacm:allowed-rights/>
<nacm:allowed-group>nacm:monitor</nacm:allowed-group>
<nacm:allowed-group>nacm:guest</nacm:allowed-group>
<nacm:comment>
do not allow monitor or guest to kill another session
</nacm:comment>
</nacm:rpc-rule>
<nacm:rpc-rule>
<nacm:rpc-module-name>
ietf-netconf
</nacm:rpc-module-name>
<nacm:rpc-name>
delete-config
</nacm:rpc-name>
<nacm:rule-name>1</nacm:rule-name>
<nacm:allowed-rights/>
<nacm:allowed-group>nacm:monitor</nacm:allowed-group>
<nacm:allowed-group>nacm:guest</nacm:allowed-group>
<nacm:comment>
do not allow monitor or guest to delete any configs
</nacm:comment>
</nacm:rpc-rule>
</nacm:rules>
</nc:config>
</nacm:nacm>
This example shows 2 RPC rules:
1. This rule prevents the monitor or guest groups (but not the admin
group) from invoking the NETCONF <kill-session> RPC operation.
Bierman Expires August 29, 2010 [Page 42]
Internet-Draft NACM February 2010
2. This rule prevents the monitor or guest groups (but not the admin
group) from invoking the NETCONF <delete-config> RPC operation.
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.
<nc:config xmlns:nc="urn:ietf:params:xml:ns:netconf:base:1.0">
<nacm:nacm
xmlns:nacm="file://draft-bierman-netconf-access-control-01.txt">
<nacm:rules>
<nacm:data-rule>
<nacm:rule-name>data-1</nacm:rule-name>
<nacm:path>/nacm:nacm</nacm:path>
<nacm:allowed-rights>read write</nacm:allowed-rights>
<nacm:allowed-group>nacm:admin</nacm:allowed-group>
<nacm:comment>
allow admin access to /nacm
</nacm:comment>
</nacm:data-rule>
<nacm:data-rule>
<nacm:rule-name>data-acme-config</nacm:rule-name>
<nacm:path
xmlns:acme="http://example.com/ns/netconf">
/acme:acme-netconf/acme:config-parameters
</nacm:path>
<nacm:allowed-rights>read write</nacm:allowed-rights>
<nacm:allowed-group>nacm:admin</nacm:allowed-group>
<nacm:allowed-group>nacm:monitor</nacm:allowed-group>
<nacm:comment>
allow admin and monitor to access acme
netconf config parameters.
</nacm:comment>
</nacm:data-rule>
<nacm:data-rule>
<nacm:rule-name>dummy-itf</nacm:rule-name>
<nacm:path
xmlns:acme="http://example.com/ns/itf">
/acme:interfaces/acme:interface[acme:name='dummy']
</nacm:path>
<nacm:allowed-rights>read write</nacm:allowed-rights>
<nacm:allowed-group>nacm:monitor</nacm:allowed-group>
<nacm:allowed-group>nacm:guest</nacm:allowed-group>
<nacm:comment>
allow monitor and guest full access to acme
dummy interface
Bierman Expires August 29, 2010 [Page 43]
Internet-Draft NACM February 2010
</nacm:comment>
</nacm:data-rule>
<nacm:data-rule>
<nacm:rule-name>admin-itf</nacm:rule-name>
<nacm:path
xmlns:acme="http://example.com/ns/itf">
/acme:interfaces/acme:interface
</nacm:path>
<nacm:allowed-rights>read write</nacm:allowed-rights>
<nacm:allowed-group>nacm:admin</nacm:allowed-group>
<nacm:comment>
allow admin full access to all acme interfaces
</nacm:comment>
</nacm:data-rule>
</nacm:rules>
</nc:config>
</nacm:nacm>
This example shows 4 data rules:
data-1: This rule gives the admin group read-write access to the
<nacm> sub-tree.
data-acme-config: This rule gives the admin and monitor groups read-
write access to the acme <config-parameters>.
dummy-itf: This rule gives the monitor and guest groups read-write
access to the acme <interface>. entry named 'dummy'.
admin-itf: This rule gives the admin group read-write access to all
acme <interface>. entries.
A.5. <notification-rule> Example
Notification rules are used to control access to a specific
notification event type.
Bierman Expires August 29, 2010 [Page 44]
Internet-Draft NACM February 2010
<nc:config xmlns:nc="urn:ietf:params:xml:ns:netconf:base:1.0">
<nacm:nacm
xmlns:nacm="file://draft-bierman-netconf-access-control-01.txt">
<nacm:rules>
<nacm:notification-rule>
<nacm:notification-module-name>
acme-system
</nacm:notification-module-name>
<nacm:notification-name>
sys-config-change
</nacm:notification-name>
<nacm:rule-name>1</nacm:rule-name>
<nacm:allowed-rights/>
<nacm:allowed-group>nacm:monitor</nacm:allowed-group>
<nacm:allowed-group>nacm:guest</nacm:allowed-group>
<nacm:comment>
only the admin group can receive config change events
</nacm:comment>
</nacm:notification-rule>
</nacm:rules>
</nc:config>
</nacm:nacm>
This example shows 1 notification rule:
1. This rule prevents the monitor or guest groups (but not the admin
group) from receiving the acme <sys-config-change> event type.
Bierman Expires August 29, 2010 [Page 45]
Internet-Draft NACM February 2010
Appendix B. Open Issues
1. Do modules need to be identified by their XML namespace URI, or
is the module name good enough?
2. Are any more wildcard mechanisms needed to specify the scope of
an access control rule?
3. Should regular expressions (module='foo-*') be allowed in schema-
instance-identifier strings?
4. Should XPath be allowed for specifying access control rules for
data nodes?
5. Are any 'access-denied' notifications needed?
6. Should data rules support nodes that would not be eligible for
retrieval with the <get> operation? If so, should schema nodes
such as rpc 'input' or 'output' be in the path expression? How
would notification content be identified?
7. Do any external access control models need to be supported
somehow? For example, should the <groups> configuration be
optionally read-only, so it can just mirror the internal
(external or proprietary) group configuration?
8. Should the nacm:secure and nacm:very-secure extensions be
optional to support, via a YANG feature?
9. Should the default access levels (e.g., read-default) be more
restrictive by default? Shiuld these defaults be a vendor
decision? An operator decision? It is important that the server
be able to install a factory default <nacm> container if needed.
Bierman Expires August 29, 2010 [Page 46]
Internet-Draft NACM February 2010
Author's Address
Andy Bierman
InterWorking Labs
303 Potrero Street, Suite 52
Santa Cruz, CA 95060-2760
USA
Phone: +1 831 460 7010
Email: andyb@iwl.com
Bierman Expires August 29, 2010 [Page 47]