Internet Engineering Task Force                               A. Bierman
Internet-Draft                                                   Brocade
Intended status: Standards Track                            M. Bjorklund
Expires: April 28, August 7, 2011                                   Tail-f Systems
                                                        October 25, 2010
                                                        February 3, 2011

          Network Configuration Protocol Access Control Model
                  draft-ietf-netconf-access-control-01
                  draft-ietf-netconf-access-control-02

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

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   provisions of BCP 78 and BCP 79.

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   This Internet-Draft will expire on April 28, August 7, 2011.

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Table of Contents

   1.  Introduction . . . . . . . . . . . . . . . . . . . . . . . . .  5  4
     1.1.  Terminology  . . . . . . . . . . . . . . . . . . . . . . .  5  4
       1.1.1.  Requirements Notation  . . . . . . . . . . . . . . . .  5  4
       1.1.2.  NETCONF Terms  . . . . . . . . . . . . . . . . . . . .  5  4
       1.1.3.  NACM  YANG Terms . . . . . . . . . . . . . . . . . . . . . .  6
   2.  Authentication Requirements  5
       1.1.4.  NACM Terms . . . . . . . . . . . . . . . . .  7
   3. . . . . .  5
   2.  Access Control Requirements  . . . . . . . . . . . . . . . . .  8
     3.1.  6
     2.1.  Protocol Control Points  . . . . . . . . . . . . . . . . .  8
     3.2.  6
     2.2.  Simplicity . . . . . . . . . . . . . . . . . . . . . . . .  9
     3.3.  7
     2.3.  Procedural Interface . . . . . . . . . . . . . . . . . . .  9
     3.4.  Database  7
     2.4.  Datastore Access . . . . . . . . . . . . . . . . . . . . .  9
       3.4.1.  7
       2.4.1.  Access Rights  . . . . . . . . . . . . . . . . . . . . 10
       3.4.2.  8
       2.4.2.  <get> and <get-config> Operations  . . . . . . . . . . 10
       3.4.3.  8
       2.4.3.  <edit-config> Operation  . . . . . . . . . . . . . . . 10
       3.4.4.  8
       2.4.4.  <copy-config> Operation  . . . . . . . . . . . . . . . 11
     3.5.  9
     2.5.  Users and Groups . . . . . . . . . . . . . . . . . . . . . 12
     3.6. 10
     2.6.  Maintenance  . . . . . . . . . . . . . . . . . . . . . . . 12
     3.7. 10
     2.7.  Configuration Capabilities . . . . . . . . . . . . . . . . 12
     3.8. 10
     2.8.  Identifying Security Holes . . . . . . . . . . . . . . . . 13
     3.9. 11
     2.9.  Data Shadowing . . . . . . . . . . . . . . . . . . . . . . 13
     3.10. 12
     2.10. NETCONF Specific Requirements  . . . . . . . . . . . . . . 14
   4. 12
   3.  NETCONF Authentication and Authorization Access Control Model (NACM)  . . . . . . . . 15
     4.1.  SSH Public Key Authentication  . . . . . . . . 14
     3.1.  Introduction . . . . . . 15
     4.2.  Local User Password Authentication . . . . . . . . . . . . 16
     4.3.  RADIUS Password Authentication and Service
           Authorization . . . . . 14
       3.1.1.  Features . . . . . . . . . . . . . . . . . 16
       4.3.1.  Operation . . . . . . 14
       3.1.2.  External Dependencies  . . . . . . . . . . . . . . . . 16
   5.  NETCONF Access Control 15
       3.1.3.  Message Processing Model (NACM)  . . . . . . . . . . . . . 18
     5.1.  Introduction . . . . 15
     3.2.  Model Components . . . . . . . . . . . . . . . . . . . 18
       5.1.1.  Features . . 17
       3.2.1.  Users  . . . . . . . . . . . . . . . . . . . . . 18
       5.1.2.  External Dependencies . . . 17
       3.2.2.  Groups . . . . . . . . . . . . . 19
       5.1.3.  Message Processing Model . . . . . . . . . . . 18
       3.2.3.  Sessions . . . . 19
     5.2.  Model Components . . . . . . . . . . . . . . . . . . . 18
       3.2.4.  Access Permissions . . 21
       5.2.1.  Users . . . . . . . . . . . . . . . . 18
       3.2.5.  Global Enforcement Controls  . . . . . . . . 21
       5.2.2.  Groups . . . . . 19
       3.2.6.  Access Control Rules . . . . . . . . . . . . . . . . . 19
     3.3.  Access Control Enforcement Procedures  . . 22
       5.2.3.  Sessions . . . . . . . . 19
       3.3.1.  Initial Operation  . . . . . . . . . . . . . . . 22
       5.2.4.  Access Permissions . . . 19
       3.3.2.  Session Establishment  . . . . . . . . . . . . . . . 22
       5.2.5.  Global Enforcement Controls . 20
       3.3.3.  'access-denied' Error Handling . . . . . . . . . . . . 23
       5.2.6.  Access Control Rules 20
       3.3.4.  Incoming RPC Message Validation  . . . . . . . . . . . . . . . . . 23
     5.3. 20
       3.3.5.  Data Node Access Control Enforcement Procedures  . . Validation  . . . . . . . . 23
       5.3.1.  Initial Operation . . . . . 23
       3.3.6.  Outgoing <rpc-reply> Authorization . . . . . . . . . . 26
       3.3.7.  Outgoing <notification> Authorization  . . . 24
       5.3.2.  Session Establishment . . . . . 26
     3.4.  Data Model Definitions . . . . . . . . . . . 24
       5.3.3.  'access-denied' Error Handling . . . . . . . 29
       3.4.1.  High Level Procedures  . . . . . 24
       5.3.4.  Incoming RPC Message Validation . . . . . . . . . . . 24
       5.3.5. 29
       3.4.2.  Data Node Access Validation  . . . . . Organization  . . . . . . . . 27
       5.3.6.  Outgoing <rpc-reply> Authorization . . . . . . . . . . 29
       5.3.7.  Outgoing <notification> Authorization  . . . . . . . . 30
     5.4.  Data Model Definitions . . . . . . .
       3.4.3.  YANG Module  . . . . . . . . . . . 33
       5.4.1.  High Level Procedures . . . . . . . . . . 30
     3.5.  IANA Considerations  . . . . . . 33
       5.4.2.  Data Organization . . . . . . . . . . . . . 41
     3.6.  Security Considerations  . . . . . 33
       5.4.3.  YANG Module . . . . . . . . . . . . 41
   4.  References . . . . . . . . . 34
     5.5.  IANA Considerations . . . . . . . . . . . . . . . . . 44
     4.1.  Normative References . . 50
     5.6.  Security Considerations . . . . . . . . . . . . . . . . . 50
   6.  Normative 44
     4.2.  Informative References . . . . . . . . . . . . . . . . . . . . . 52 44
   Appendix A.  Usage Examples  . . . . . . . . . . . . . . . . . . . 53 45
     A.1.  <groups> Example . . . . . . . . . . . . . . . . . . . . . 53 45
     A.2.  <module-rule> Example  . . . . . . . . . . . . . . . . . . 54 46
     A.3.  <rpc-rule> Example . . . . . . . . . . . . . . . . . . . . 55 47
     A.4.  <data-rule> Example  . . . . . . . . . . . . . . . . . . . 57 49
     A.5.  <notification-rule> Example  . . . . . . . . . . . . . . . 59 51
   Appendix B.  Open Issues  Change Log  . . . . . . . . . . . . . . . . . . . . . 60
   Appendix C.  Change Log 52
     B.1.  01-02  . . . . . . . . . . . . . . . . . . . . . 61
     C.1. . . . . . 52
     B.2.  00-01  . . . . . . . . . . . . . . . . . . . . . . . . . . 61
     C.2. 52
     B.3.  00 . . . . . . . . . . . . . . . . . . . . . . . . . . . . 61 52
   Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . . 62 53

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 NETCONF protocol authentication and access control mechanisms for the Operation
   and Content layers, layers of NETCONF, as defined in [RFC4741],
   [I-D.ietf-netconf-4741bis], and [RFC5277].  It contains five three main
   sections:

   1.  Authentication Requirements

   2.  Access Control Requirements

   3.  NETCONF Authentication and Authorization Model

   4.

   2.  NETCONF Access Control Model (NACM)

   5.

   3.  YANG Data Model (ietf-nacm.yang) (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 RFC 4741 [I-D.ietf-netconf-4741bis] and are
   not redefined here:

   o  client

   o  datastore

   o  operation

   o  RPC  protocol operation

   o  server

   o  session

   o  user

1.1.3.  YANG Terms

   The following terms are defined in [RFC6020] and are not redefined
   here:

   o  data node

1.1.4.  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.

   authentication:  The process of verifying a user's identity.

   superuser:  The special administrative user account which is given
      unlimited NETCONF access, and is exempt from all access control
      enforcement.

2.  Authentication Requirements

   The authentication mechanism must support password authentication
   over RADIUS, to support deployment scenarios with centralized
   authentication servers.  Additionally, local users must be supported,
   for scenarios when no centralized authentication server exists, or
   for situations where the centralized authentication server cannot be
   reached from the device.

   Since the mandatory transport protocol for NETCONF is SSH NETCONF
   Over SSH [RFC4742], the authentication model must support SSH's
   "publickey" and "password" authentication methods [RFC4252]

   The model for authentication configuration should be flexible enough
   to support authentication methods defined by other standard documents
   or by vendors.

3.  Access Control Requirements

3.1.

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  protocol   |          |   prune     |      client
    request -->  |  operation  |          | restricted  | ---> reply
                 |  allowed?   |          | <rpc-reply> |
                 +-------------+          |   nodes?    |
                       |                  +-------------+
                       | if any database 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:

   RPC

   protocol operation:  Configurable permission to invoke specific RPC
      protocol operations is required.  Wildcard or multiple target
      mechanisms to reduce configuration and effort are also required.

   NETCONF database: datastore:  Configurable permission to read and/or alter
      specific data nodes within any conceptual database datastore is required.
      Wildcard or multiple target mechanisms to reduce configuration and
      effort are also required.

   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.

3.2.

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 protocol operation invocation, all conceptual database
   datastore access, and all NETCONF session output.

   Default access control policy needs to be as secure as possible.

   Protocol access should be defined with a small and familiar set of
   permissions, while still allowing full control of NETCONF database datastore
   access.

   Access control does not need to be applied to NETCONF <hello>
   messages.

3.3.

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 RPC protocol operations is not required.

3.4.  Database

2.4.  Datastore Access

   It must be possible to control access to specific nodes and sub-trees
   within the conceptual NETCONF database. datastore.

   In order for a user to obtain access to a particular database datastore 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. datastores.
   For example, the candidate configuration or the running
   configuration.

   Only the standard NETCONF databases datastores (candidate, running, and
   startup) are controlled by the ACM.  Local or remote files or databases
   datastores 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.

   Only a privileged user should be able to alter the factory-default
   access control rules.

3.4.1.

2.4.1.  Access Rights

   A small set of hard-wired database datastore access rights is needed to
   control access to all possible NETCONF database 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
      database.
      datastore.

   o  Read: Allows the client to read a data node instance from a
      database,
      datastore, or receive the notification event type.

   o  Update: Allows the client to update an existing data node instance
      in a database. datastore.

   o  Delete: Allows the client to delete a data node instance from a
      database.
      datastore.

   o  eXec: Allows the client to execute the protocol operation.

3.4.2.

2.4.2.  <get> and <get-config> Operations

   Read operations for restricted configuration data,

   Data nodes to which the client does not have 'read' access, either
   directly or via wildcard access, are silently omitted from the <rpc-reply> <rpc-
   reply> message.

3.4.3.

2.4.3.  <edit-config> Operation

   The NACM access rights are not directly coupled to the NETCONF
   operation <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 database. datastore.  This section
   describes how these access rights apply to the specific database 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 database 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 database 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' 'replace', 'delete', or 'delete' 'remove' operation on a database 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 database. datastore.  For example, a container or list
   nodes may be present for naming purposes, which do not actually alter
   the corresponding database 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.

   A 'merge' operation may include data nodes, but not include
   particular child data nodes that are present in the database. 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.

   The contents of specific restricted database datastore nodes must not be
   exposed in any <rpc-error> elements within the reply.

3.4.4.

2.4.4.  <copy-config> Operation

   Access control for the <copy-config> operation requires special
   consideration because the operator is replacing the entire target
   database.  Write
   datastore.  Read access to the entire database source datastore, and write
   access to the entire target datastore is needed for this operation to
   succeed.

   A client must have access to every database 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 must have full read access to the
   database
   datastore in order to receive a complete copy of its contents.  If
   not, the server will simply omit these sub-trees from the reply.  If
   that copy is later used to restore the server database, datastore, the server
   will interpret the missing nodes as a request to delete those nodes,
   and return an error.

3.5.

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
   types of less-privileged conceptual user accounts.  These groups must
   be configurable by the operator.

3.6.

   It must be possible to delegate the user-to-group mapping to a
   central server, such as RADIUS [RFC2865] [RFC5607].  Since
   authentication is performed by the NETCONF transport layer, and
   RADIUS performs authentication and service authorization at the same
   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.  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.

3.7.

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 sub-trees
   within the configuration database datastore must be supported.  Existing
   mechanisms should be used to identify the sub-tree(s) for this
   purpose.

3.8.

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 customary 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 must study
      some more RFC text, and determine how to close the security
      hole(s).

   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 identify NETCONF content which should 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.

3.9.

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 ensure that unauthorized access to its
   conceptual databases 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 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.

3.10.

2.10.  NETCONF Specific Requirements

   The server must MUST be able to identify the specific protocol access
   request at the 4 access control points defined above.

   The server must MUST be able to identify any database datastore access request,
   even for proprietary operations.

   A session must client MUST always be authorized to invoke the <close-session>
   operation, defined in [RFC4741]. [I-D.ietf-netconf-4741bis].

   A session must 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 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.

4.

3.  NETCONF Authentication and Authorization Access Control Model (NACM)

3.1.  Introduction

   This document defines three authentication methods for use with
   NETCONF:

      publickey for local users over SSH
      password for local users over any transport
      password for RADIUS users over any transport

   Additional methods may be defined by other standard documents or by
   vendors.

   Conceptually, the NETCONF transport subsystem authenticates the user,
   and passes the name section provides a high-level overview of the authenticated user to access control
   model structure.  It describes the NETCONF server. protocol message
   processing model, and the conceptual access control requirements
   within that model.

3.1.1.  Features

   The NETCONF server authorizes NACM data model provides the user by mapping it following features:

   o  Independent control of RPC, data, and notification access.

   o  Very simple access control rules configuration data model which is
      easy to one or more
   groups.  Access use.

   o  The concept of a 'superuser' type of account is supported, but
      configuration such an account is beyond the scope of this
      document.  The server must be able to specific operations determine if a superuser
      account is available, and content 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 datastore permissions is then controlled
   by 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 as described are applied to configurable groups of users.

   o  The entire ACM can be disabled during operation, in Section 5.

   Some protocols, such as RADIUS, performs both authentication and
   authorization, and has a mechanism order to report authorization attributes 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.  These attributes

   o  Simple unconstrained YANG instance identifiers are made available used to
      configure access control rules for specific data nodes.

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
   server in an implementation specific manner.

   This document defines two optional YANG features, 'local-users' Over SSH
   [I-D.ietf-netconf-rfc4742bis] is also supported by the server, and
   'radius', which
   that the server advertises has access to indicate support for
   configuring local users on the device, and for configuring RADIUS
   access, respectively.

4.1.  SSH Public Key Authentication

   If the NETCONF server advertises the 'local-users' feature,
   configuration of local users and their SSH public keys is supported
   in the /nacm/authentication/user list.

   Public key authentication is requested by the SSH client.  The SSH
   server looks up the user name provided by the client in the /nacm/
   authentication/user list, and verifies the key as described in
   [RFC4253].

   If the 'local-users' feature is supported, then when a NETCONF client
   starts an SSH session towards the server, using the "publickey"
   authentication 'method name' [RFC4252], the SSH server looks up the user name given in the SSH authentication request in the /nacm/
   authentication/user list,

4.2.  Local User Password Authentication

   If the NETCONF server advertises the 'local-users' feature,
   configuration of local users and their passwords is supported in the
   /nacm/authentication/user list.

   For NETCONF transport protocols that support password authentication,
   the leaf-list 'user-authentication-order' associated with each
   session.

   The YANG Data Modeling Language [RFC6020] is used to control if local
   user password authentication should be used.

   In SSH, password authentication is requested by the client.  Other
   NETCONF transport protocols may also support password authentication.

   When local user password authentication is requested, the NETCONF
   transport looks up the user name provided by the client in the /nacm/
   authentication/user list, and verifies the password.

4.3.  RADIUS Password Authentication and Service Authorization

   If define the
   NETCONF server advertises the 'radius' feature, it supports
   user authentication and service authorization with RADIUS, as
   described data models specified in this section.

   For NETCONF transport protocols that support password authentication,
   the leaf-list 'user-authentication-order' document.  The YANG instance-
   identifier data type is used to configure data-node-specific access
   control if
   RADIUS password authentication should be used.

   In SSH, password authentication is requested by rules.

3.1.3.  Message Processing Model

   The following diagram shows the client.  Other NETCONF transport protocols may also support password authentication.

4.3.1.  Operation

   [Editor's Note: I prefer to keep this section short, and just refer
   to message flow model, including
   the relevant rfcs points at which have detailed information on radius usage,
   instead of duplicating this info here...]

   When RADIUS user authentication access control is requested, the applied, during NETCONF transport
   subsystem acts as a RADIUS client.  In the Access-Request request
   [RFC2865], the following RADIUS attributes SHOULD be sent by the
   client [RFC5607]:

   o  Service-Type with the value Framed-Management

   o  Framed-Management-Protocol with the value NETCONF

   o  Management-Transport-Protection with the value Integrity-
      Confidentiality-Protection

   As described in RFC 5607, if an Access-Accept message is received
   which does not authorize the requested service, access MUST be
   denied.

   If any Management-Policy-Id attributes are present in the Access-
   Accept message, they are treated as group names in the access control
   procedure, as described in Section 5.

   The following RADIUS attributes MAY be sent by the RADIUS server:

   o  Session-Timeout

   o  Idle-Timeout

   See [RFC2865] for a description of these attributes.  These timeout
   values MUST be enforced by the NETCONF server.

5.  NETCONF Access Control Model (NACM)

5.1.  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.

5.1.1.  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 such an account 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 database 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 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.

5.1.2.  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 [RFC6020] 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.

5.1.3.  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.

                    +-------------------------+
                    |
   processing.

                    +-------------------------+
                    |       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 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 user identity for the session is the
      'superuser'.

   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 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.

5.2.  Model Components

   This section defines the conceptual components related to access
   control model.

5.2.1.  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.

   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 write requests must be rejected with an
   'access-denied' error-tag value.  If a read operation is not
   authorized, then the requested data is silently dropped from the
   reply.

   The server MAY 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 exists, then
   all NETCONF access will be controlled by NACM.

5.2.2.  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
   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.

5.2.3.  Sessions

   A session is simply a NETCONF session, which is the entity which is
   granted access to specific NETCONF operations.

   A session is associated with a single user name for the lifetime of
   the session.

5.2.4.  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 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 RPC operation execution separately
   from configuration database 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 an RPC operation.

5.2.5.  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.

5.2.6.  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.

5.3.  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.

5.3.1.  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
   into the running configuration.

5.3.2.  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.

5.3.3.  '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.

5.3.4.  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.

                   NETCONF server
                  +------------+
         +===========+     +-------------+   +----------------+
         |    XML   <rpc>   |---> | <rpc-reply> |   message   | <notification> | dispatcher
         |
                  +------------+ acc. ctl  |     |  generator  |   |  generator     |
         +===========+     +-------------+   +----------------+
               |              ^    ^                ^
               V
                  +------------+       +------+    | NC-base NS                |
         +-----------+ |   +=============+  +================+
         |   <rpc>   |
                  +------------+ |   | <rpc-reply> |  | <notification> |  +-------------------------+
         |   +------------+ processor |-+   |  acc. ctl   |  |  access ctl    |
                    V                V               V
         +-----------+ +---------------+ +------------+     +=============+  +================+
               | acme NS   |                  ^        ^
               V   +----------------+ | NC-base NS        |
         +===========+              | NC-base NS |        | <my-edit>
         | data node |              | |        |
         | acc. ctl  | -----------+ | |        |
         +===========+            | | <edit-config> |        | <unlock>
               |
               +-----------+ +---------------+ +------------+                  | | |        |
               V                  V
                    +----------------------+ V |        |
         +---------------+      +-----------------+
         | configuration | ---> |     server      |      database
         |
                    +----------------------+   datastore   |      | instrumentation |
         |               | <--- |                 |
         +---------------+      +-----------------+

                                 Figure 3 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 begins with the message dispatcher.  Only well-formed
   XML is applied to all <rpc> messages should be processed (except <close-
      session>) received by the server.

   After the server validates server, individually, for each active
      session, unless the <rpc> element, and determines session is associated with the
   namespace URI and 'superuser'
      account.

   o  If the element name of 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 being
   requested, on the RPC 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 verifies that checks the notification
      event type, and if it is one which the session is not authorized
      to invoke read, then the RPC operation.

   The RPC operation notification is authorized by following these steps:

   1.   If dropped for that subscription.

3.2.  Model Components

   This section defines the <enable-nacm> parameter conceptual components related to access
   control model.

3.2.1.  Users

   A 'user' is set the conceptual entity, which is associated with the
   access permissions granted to 'false', then a particular session.  A user is
   identified by a string which must be unique within the RPC
        operation server.

   As described in [I-D.ietf-netconf-4741bis], the user name string is permitted.

   2.
   derived from the transport layer during session establishment.  If
   the transport layer cannot authenticate the user, the session is associated with the
   terminated.

   The server MAY support a 'superuser' administrative user account, then
   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 RPC exact
   user name for the superuser account.  If no such account exists, then
   all NETCONF access will be controlled by NACM.

3.2.2.  Groups

   Access to a specific NETCONF operation is permitted.

   3.   If the requested operation granted to a session,
   associated with a group, not a user.

   A group is identified by its name.  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.

3.2.3.  Sessions

   A session is simply a NETCONF session, which is the entity which is
   granted access to specific NETCONF <close-session>
        operation, then the RPC operation operations.

   A session is permitted.

   4.   Check all the <group> entries for ones that contain associated with a <user-
        name> entry that matches the single user name for the session making lifetime of
   the request.

   5.   If no groups session.

3.2.4.  Access Permissions

   The access permissions are found:

        *  If the requested RPC operation is associated with NETCONF protocol specific set of
   permissions that have been assigned to a YANG
           module advertised particular session.

   The same access permissions MUST stay in effect for the server capabilities, and the rpc
           statement contains processing of
   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 particular message.

   The server MUST use the
        requested RPC operation.  Any matching access control rules are processed 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 effect at the <allowed-rights>
        bits field for time
   the entry, otherwise continue. message is processed.

   The 'exec' bit
        MUST be present in the <allowed-rights> bits field for 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 an <rpc-
        rule>, so it is not used in this procedure.

   8.   If the <rpc-rule> entry is considered a match, the the 'nacm-
        action' leaf protocol operation.

3.2.5.  Global Enforcement Controls

   A global on/off switch is checked.  If provided to enable or disable all access
   control enforcement.

   An on/off switch is equal provided to 'permit', then the RPC
        operation enable or disable default access to
   invoke protocol operations.

   An on/off switch is permitted, otherwise it provided to enable or disable default permission
   to receive data in replies and notifications.

   An on/off switch is denied.

   9.   Check if there provided to enable or disable default access to
   alter configuration data.

3.2.6.  Access Control Rules

   There are any matching <module-rule> entries for the
        same module as the requested RPC operation.  Any matching 4 types of rules
        are processed available in user-defined order, NACM:

   module rule:  Controls access for definitions in case there are multiple
        <module-rule> entries a specific module,
      identified by its name.

   protocol operation rule:  Controls access for the a specific protocol
      operation, identified by its module containing the requested
        RPC operation.

   10.  If and name.

   data node rule:  Controls access for a <module-rule> entry is found, then check specific data node, identified
      by its path location within the <allowed-
        rights> bits field conceptual XML document for the entry, otherwise continue.  If the
        'exec' bit is present in the <allowed-rights> bits field then
        the RPC rule is considered
      data node.

   notification rule:  Controls access for a match. otherwise it is not
        considered 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 match the request.

   11.  If NETCONF message processing model.  In addition,
   the <module-rule> entry is considered initial start-up mode for a match, 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 'nacm-
        action' leaf is checked.  If is equal to 'permit', then NETCONF server, the RPC
        operation is permitted, otherwise it is denied.

   12. access
   control configuration will probably not be present.  If the requested operation is identified an not, a nacm:secure server
   MUST 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
        nacm:very-secure RPC operation, then
   while the RPC operation non-volatile configuration data is
        denied.

   13.  If processed and loaded
   into the <exec-default> parameter is set running configuration.

3.3.2.  Session Establishment

   The access control model applies specifically to 'permit', then permit
        the RPC operation, otherwise the RPC operation is denied.

   If the well-formed XML
   content transferred between a client and a server, after session is not authorized to invoke
   establishment has been completed, and after the RPC operation then an
   <rpc-error> is generated with <hello> exchange has
   been successfully completed.

   A server should not include any sensitive information in any
   <capability> elements within the following information:

   error-tag:  access-denied

   error-path:  /rpc/method-QName, where 'method-QName' <hello> exchange.

   Once session establishment is completed, and a qualified
      name identifying the actual RPC operation name.  For example,
      '/rpc/edit-config' represents the <edit-config> operation in user identity has been
   authenticated, the NETCONF base namespace.

   If the configuration database is accessed, either directly or as transport layer reports the username and a
   side effect
   possibly empty set of group names associated with the RPC operation, then user to the
   NETCONF server.  The NETCONF server must intercept will enforce the
   operation access control
   rules, based on the supplied user identity, group names, and make sure the session
   configuration data stored on the server.

3.3.3.  'access-denied' Error Handling

   The 'access-denied' error-tag is authorized generated when the access control
   system denies access to either a request to invoke a protocol
   operation or a request to perform the
   requested a particular operation on the specified data.

5.3.5.  Data Node Access
   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

   If a data node

   The diagram below shows the basic conceptual structure of the access
   control processing model for incoming NETCONF <rpc> messages, within
   a server.

                   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 is accessed, or a
   conceptual non-configuration node is accessed, then     |
                    |      datastore       |
                    +----------------------+

                                 Figure 3

   Access control begins with the message dispatcher.  Only well-formed
   XML messages should be processed by the server.

   After the server must
   ensure 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 client session
   is authorized to perform the requested
   operation create, read, update, or delete operation on invoke the specified
   data node. protocol operation.

   The data node access request protocol operation is authorized by following these steps:

   1.   If the <enable-nacm> parameter is set to 'false', then the data
        node access request
        protocol operation is permitted.

   2.   If the session is associated with the 'superuser' account, then
        the data node access request protocol operation is permitted.

   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 matches the user name for the session making
        the request.

   4.  Add to these groups the set of groups provided by
        the transport layer.

   5.   If no groups are found:

        *  If the requested data node protocol operation is associated with a YANG
           module advertised in the server capabilities, and the data
           definition statements (or any of its ancestors) rpc
           statement contains a nacm:secure or nacm:very-secure
           extension, then the data node
           access request protocol operation is denied.

        *  For a read request, if  If the <read-default> <exec-default> parameter is set to 'permit', then
           permit the data node access request, otherwise
           deny the request.  For a read protocol operation, this means that the
           requested node is not included in the rpc-reply.

        *  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.

   6.   Check if there are any matching <data-rule> <rpc-rule> entries for the
        requested data node access request. protocol operation.  Any matching rules are processed
        in user-defined order, in case there are multiple
        <data-rule> <rpc-rule>
        entries for the requested data node.

   6. protocol operation.

   7.   If an <data-rule> <rpc-rule> entry is found, then check the <allowed-
        rights> <allowed-rights>
        bits field for the entry, otherwise continue.

        1.  For a creation operation, if the 'create' bit is present in
            the <allowed-rights> bits field then the entry is considered
            to be a match.

        2.  For a read operation, if the 'read' bit is present in the
            <allowed-rights> bits field, then the entry is considered to
            be a match.

        3.  For an update (e.g., 'merge' or 'replace') operation, if the
            'update' bit is present in the <allowed-rights> bits field
            then the entry is considered to be a match.

        4.  For a deletion (e.g., 'delete') operation, if the 'delete'  The 'exec' bit is
        MUST be present in the <allowed-rights> bits field then the
            entry for an <rpc-
        rule>, so it is considered to be a match.

   7. not used in this procedure.

   8.   If the <data-rule> <rpc-rule> entry is considered a match, the then the 'nacm-
        action' leaf is checked.  If it is equal to 'permit', then the
        data
        protocol operation is permitted, otherwise it is denied.  For 'read'
        operations, 'denied' means the requested data is not returned in
        the reply.

   8.

   9.   Check if there are any matching <module-rule> entries for the
        same module as the requested data node. protocol operation.  Any matching
        rules are processed in user-defined order, in case there are
        multiple <module-rule> entries for the module containing the
        requested
        data node.

   9. protocol operation.

   10.  If a <module-rule> entry is found, then check the <allowed-
        rights> bits field for the entry, otherwise continue.

        1.  For a creation operation, if  If the 'create'
        'exec' bit is present in the <allowed-rights> bits field then
        the entry is considered
            to be a match.

        2.  For a read operation, if the 'read' bit is present in the
            <allowed-rights> bits field, then the entry RPC rule is considered to
            be a match.

        3.  For an update (e.g., 'merge' or 'replace') operation, if the
            'update' bit is present in the <allowed-rights> bits field
            then the entry otherwise it is not
        considered to be a match.

        4.  For a deletion (e.g., 'delete') operation, if the 'delete'
            bit is present in the <allowed-rights> bits field then match the
            entry is considered to be a match.

   10. request.

   11.  If the <module-rule> entry is considered a match, then the the 'nacm-
        action'
        'nacm-action' leaf is checked.  If it is equal to 'permit', then the
        data operation is permitted, otherwise it is denied.  For 'read'
        operations, 'denied' means the requested data is not returned in
        the reply.

   11.  For a read request, if the requested data node is identified an
        a nacm:very-secure definition, then the requested data node is
        not included in the reply.

   12.  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.

   13.  For a read request, if the <read-default> parameter is set to
        'permit', then include the requested data in then
        the reply, protocol operation is permitted, otherwise do not inlcude it is denied.

   12.  If the requested data in the reply.

   14.  For operation is identified an a write request, if nacm:secure or
        nacm:very-secure protocol operation, then the <write-default> protocol operation
        is denied.

   13.  If the <exec-default> parameter is set to 'permit', then permit
        the data node access request, protocol operation, otherwise
        deny the request.

5.3.6.  Outgoing <rpc-reply> Authorization

   The <rpc-reply> message should be checked by the server to make sure
   no unauthorized data protocol operation is contained within it.
        denied.

   If so, the restricted
   data must be removed from the message before it session is sent to the
   client.

   For RPC operations which do not access any data nodes, then any
   client authorized to invoke the RPC protocol operation
   then an <rpc-error> is also authorized to
   receive the <rpc-reply> for that RPC operation.

5.3.7.  Outgoing <notification> Authorization

   The <notification> message should be checked by generated with the server to make
   sure no unauthorized data following information:

   error-tag:  access-denied

   error-path:  /rpc/method-QName, where 'method-QName' is contained within it.  If so, a qualified
      name identifying the
   restricted data must be removed from actual protocol operation name.  For example,
      '/rpc/edit-config' represents the message before it is sent to <edit-config> operation in the client.

   Configuration of access control rules specifically for descendent
   nodes
      NETCONF base namespace.

   If the configuration datastore is accessed, either directly or as a
   side effect of the notification event type element are outside protocol operation, then the scope of
   this document.  If server MUST intercept
   the operation and make sure the session is authorized to receive perform the
   notification event type,
   requested operation on the specified data.

3.3.5.  Data Node Access Validation

   If a data node within a configuration datastore is accessed, or a
   conceptual non-configuration node is accessed, then it the server MUST
   ensure that the client session is also authorized to receive any perform the requested
   operation create, read, update, or delete operation on the specified
   data it contains. node.

   The following figure shows the conceptual message processing model
   for outgoing <notification> messages.

                   NETCONF server
                  +------------+
                  |    XML     |
                  |   message  |
                  | generator  |
                  +------------+
                        ^
                        |
                +----------------+
                | <notification> |
                |  generator     |
                +----------------+
                        ^
                        |
               +=================+
               | <notification>  |
               | data node access control |
               |  <eventType>    |
               +=================+
                        ^
                        |
            +------------------------+
            | server instrumentation |
            +------------------------+
                      |     ^
                      V     |
             +----------------------+
             |    configuration     |
             |      database        |
             +----------------------+

                                 Figure 4

   The generation of a notification event for a specific subscription request is authorized by following these steps:

   1.   If the <enable-nacm> parameter is set to 'false', then the
        notification event data
        node access request is permitted.

   2.   If the session is associated with the 'superuser' account, then
        the notification event data node access request is permitted.

   3.   If the requested operation is the NETCONF <replayComplete> or
        <notificationComplete> event type, then the notification event
        is permitted.

   4.   Check all the <group> entries for ones that contain a <user-
        name> entry that matches the user name for the session that
        started making
        the notification subscription.

   5. request.  Add to these groups the set of groups provided by
        the transport layer.

   4.   If no groups are found:

        *  If the requested notification data node is associated with a YANG module
           advertised in the server capabilities, and the
           notification data
           definition statement or any of its ancestors contains a nacm:secure or nacm:very- nacm:
           secure or nacm:very-secure extension, then the notification event data node
           access request is dropped for
           the associated subscription. denied.

        *  If  For a read request, if the <read-default> parameter is set to
           'permit', then permit the notification event, data node access request, otherwise drop
           deny the request.  For a read operation, this event type
           for means that the associated subscription.

   6.
           requested node is not included in the rpc-reply.

        *  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 <notification-rule> <data-rule> entries for the specific notification event type being delivered to the
        subscription.
        requested data node access request.  Any matching rules are
        processed in user-defined order, in case there are multiple <notification-rule>
        <data-rule> entries for the requested notification event type.

   7. data node.

   6.   If a <notification-rule> an <data-rule> entry is found, then check the
        <allowed-rights> <allowed-
        rights> bits field for the entry, otherwise continue.
        If

        1.  For a creation operation, if the 'create' bit is present in
            the <allowed-rights> bits field then the entry is considered
            to be a match.

        2.  For a read operation, if the 'read' bit is present in the
            <allowed-rights> bits field, then the entry is considered to
            be a match.

        3.  For an update (e.g., 'merge' or 'replace') operation, if the
            'update' bit is present in the <allowed-rights> bits field
            then the notification event type entry is considered to be a match.

        4.  For a deletion (e.g., 'delete') operation, if the 'delete'
            bit is present in the <allowed-rights> bits field then the
            entry is considered to be a match.

   7.   If the <data-rule> entry is considered a match, then the 'nacm-
        action' leaf is checked.  If it is equal to 'permit', then the
        data operation is permitted, otherwise it is
        dropped for denied.  For 'read'
        operations, 'denied' means the associated subscription. requested data is not returned in
        the reply.

   8.   Check if there are any matching <module-rule> entries for the
        same module as the notification event type. requested data node.  Any matching rules are
        processed in user-defined order, in case there are multiple
        <module-rule> entries for the module containing the notification
        event type. requested
        data node.

   9.   If a <module-rule> entry is found, then check the <allowed-
        rights> bits field for the entry, otherwise continue.  If

        1.  For a creation operation, if the 'create' bit is present in
            the <allowed-rights> bits field then the entry is considered
            to be a match.

        2.  For a read operation, if the 'read' bit is present in the
            <allowed-rights> bits field, then the entry is considered to
            be a match.

        3.  For an update (e.g., 'merge' or 'replace') operation, if the
            'update' bit is present in the <allowed-rights> bits field
            then the entry is considered to be a match.

        4.  For a deletion (e.g., 'delete') operation, if the
        'read' 'delete'
            bit is present in the <allowed-rights> bits field then the notification event type is permitted, otherwise it
            entry is
        dropped for the associated subscription. considered to be a match.

   10.  If the requested event type <module-rule> entry is identified an considered a nacm:very-secure
        notification definition, match, then the notification event type
        'nacm-action' leaf is
        denied.

   11. checked.  If the <read-default> parameter it is set equal to 'permit', then permit
        the notification event type, otherwise it is dropped for the
        associated subscription.

5.4.  Data Model Definitions

   This section defines the semantics of the conceptual data structures
   found in the data model in Section 5.4.

5.4.1.  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.

5.4.2.  Data Organization

   The top-level element is called <nacm>, and it is defined in
        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.

   container <authentication>:  Configuration of the NETCONF server user
      authentication mechanisms.

   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 is permitted, otherwise it is denied.  For
        'read' operations, 'denied' means the number of times requested data is not
        returned in the
      server has denied an RPC operation reply.

   11.  For a read request, since if the last reboot
      of requested data node is identified an
        a nacm:very-secure definition, then the server.

   leaf <denied-data-writes>:  Read-only counter of requested data node is
        not included in the number of times reply.

   12.  For a write request, if the server has denied requested data node is identified an
        a nacm:secure or nacm:very-secure definition, then the data node
        access request is denied.

   13.  For a read request, if the <read-default> parameter is set to
        'permit', then include the requested data in the reply,
        otherwise do not include the requested data in the reply.

   14.  For a write request, since if the last
      reboot of <write-default> parameter is set to
        'permit', then permit the server.

   container <groups>:  Configures data node access request, otherwise
        deny the groups used 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.

   For protocol operations which do not access
      control system.

      list <group>:  A list of user names belonging any data nodes, then any
   client authorized to invoke the same
         administrative group.

   container <rules>:  Configures protocol operation is also authorized
   to receive the access control rules used <rpc-reply> for that protocol 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 server.

      list <module-rule>:  Configures
   restricted data must be removed from the access control rules for a
         specific module.

      list <rpc-rule>:  Configures message before it is sent to
   the client.

   Configuration of access control rules specifically for RPC
         operation invocation.

      list <data-rule>:  Configures descendent
   nodes of the access control rules for
         configuration database access.

      list <notification-rule>:  Configures notification event type element are outside the access control rules for
         controlling delivery scope of <notification> events.

5.4.3.  YANG Module

   The following YANG module
   this document.  If the session is provided authorized to specify the normative
   NETCONF content that must by supported by the server.

   The ietf-nacm YANG module imports typedefs from [RFC6021].

 // RFC Ed.: please update receive the date
   notification event type, then it is also authorized to receive any
   data it contains.

   The following figure shows the date of publication
 <CODE BEGINS> file="ietf-nacm@2010-10-25.yang"

 module ietf-nacm {

   namespace "urn:ietf:params:xml:ns:yang:ietf-nacm";

   prefix "nacm";

   import ietf-yang-types {
     prefix yang;

   }

   import ietf-inet-types {
     prefix inet;
   }

   organization
     "IETF conceptual message processing model
   for outgoing <notification> messages.

                   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>

      Editor:   Martin Bjorklund
                <mailto:mbj@tail-f.com>";

   description
     "NETCONF Server Access Control Model.

      Copyright (c) 2010 IETF Trust and server
                  +------------+
                  |    XML     |
                  |   message  |
                  | generator  |
                  +------------+
                        ^
                        |
                +----------------+
                | <notification> |
                |  generator     |
                +----------------+
                        ^
                        |
               +=================+
               | <notification>  |
               |  access control |
               |  <eventType>    |
               +=================+
                        ^
                        |
            +------------------------+
            | server instrumentation |
            +------------------------+
                      |     ^
                      V     |
             +----------------------+
             |    configuration     |
             |      datastore       |
             +----------------------+

                                 Figure 4

   The generation of a notification event for a specific subscription is
   authorized by following these steps:

   1.   If the persons identified as
      authors of <enable-nacm> parameter is set to 'false', then the code. All rights reserved.

      Redistribution and use in source and binary forms,
        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
      without modification,
        <notificationComplete> event type, then the notification event
        is permitted pursuant to, and subject
      to permitted.

   4.   Check all the license terms contained in, <group> entries for ones that contain a <user-
        name> entry that matches the Simplified BSD
      License set forth in Section 4.c of user name for the IETF Trust's
      Legal Provisions Relating session that
        started the notification subscription.  Add to IETF Documents
      (http://trustee.ietf.org/license-info).

      This version these groups the
        set of this groups provided by the transport layer.

   5.   If no groups are found:

        *  If the requested notification is associated with a YANG
           module is part of RFC XXX; see advertised in the RFC itself for full legal notices.";
   // RFC Ed.: replace XXXX with actual RFC number server capabilities, and remove this note

   //reference "RFC XXXX";

   // RFC Ed.: remove this note
   // Note: extracted from draft-ietf-netconf-access-control-01.txt
   // RFC Ed.: please update the date to
           notification statement contains a nacm:secure or nacm:very-
           secure extension, then the date of publication
   revision "2010-10-25" {
     description
       "Initial version";
     reference
       "RFC XXXX: Network Configuration Protocol Access Control Model";
   }

   /* notification event is dropped for
           the associated subscription.

        * Extension statements
    */

   extension secure {
     description
       "Used  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 indicate that the data model node
        represents
        subscription.  Any matching rules are processed in user-defined
        order, in case there are multiple <notification-rule> entries
        for the requested notification event type.

   7.   If a sensitive security system parameter. <notification-rule> entry is found, then check the
        <allowed-rights> bits field for the entry, otherwise continue.
        If present, the NETCONF server will only allow 'read' bit is present in the designated 'superuser' to have write or execute
        default nacm-rights-type for <allowed-rights> bits field
        then the node.  An explicit access
        control rule notification event type is required permitted, otherwise it is
        dropped for all other users.

        The 'secure' extension may appear within a data, rpc,
        or the associated subscription.

   8.   Check if there are any matching <module-rule> entries for the
        same module as the notification node definition.  It is ignored
        otherwise.";
   }

   extension very-secure {
     description
       "Used to indicate that event type.  Any matching rules
        are processed in user-defined order, in case there are multiple
        <module-rule> entries for the data model node
        controls module containing the notification
        event type.

   9.   If a very sensitive security system parameter. <module-rule> entry is found, then check the <allowed-
        rights> bits field for the entry, otherwise continue.  If present, the NETCONF server will only allow
        'read' bit is present in the designated 'superuser' to have read, write, or execute
        default nacm-rights-type for <allowed-rights> bits field then
        the node.  An explicit access
        control rule notification event type is required permitted, otherwise it is
        dropped for all other users.

        The 'very-secure' extension may appear within the associated subscription.

   10.  If the requested event type is identified an a data, rpc,
        or nacm:very-secure
        notification node definition.  It definition, then the notification event type is ignored
        otherwise.";
   }

   /*
    * Features
    */

   feature authentication {
     description
       "Indicates that
        denied.

   11.  If the NETCONF server can be configured <read-default> parameter is set to do authentication of users.";
   }

   feature radius {
     if-feature authentication;
     description
       "Indicates that 'permit', then permit
        the NETCONF server can be
        configured to act as a NAS and authenticate users
        with RADIUS.";
     reference
       "RFC 2865: Remote Authentication Dial In User Service (RADIUS)
        RFC 5607: Remote Authentication Dial-In User Service (RADIUS)
                  Authorization notification event type, otherwise it is dropped for Network Access Server (NAS)
                  Management";
   }

   feature local-users {
     if-feature authentication;
     description
       "Indicates 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.  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 NETCONF server supports
        local global settings.

   2.  Configure one or more user authentication.";
   }

   /*
    * Identities
    */

   identity authentication-method {
     description
       "Base identity groups.

   3.  Configure zero or more access control rules for NETCONF authentication methods.";
   }

   identity radius {
     base authentication-method;
     description
       "Indicates NETCONF authentication using RADIUS.";
     reference
       "RFC 2865: Remote Authentication Dial In User Service (RADIUS)
        RFC 5607: Remote Authentication Dial-In User Service (RADIUS)
                  Authorization specific modules.

   4.  Configure zero or more access control rules for Network Access Server (NAS)
                  Management";
   }

   identity local-users {
     base authentication-method;
     description
       "Indicates password-based NETCONF authentication using locally
        configured users.";
   }

   /*
    * Derived types
    */

   typedef nacm-user-name-type {
     type string {
       length "1..max";
     }
     description
       "General Purpose User Name string.";
   }

   typedef nacm-matchall-string-type { specific protocol
       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 string {
       pattern "\*";
     }
     description
       "The string containing a single asterisk '*' access.

3.4.2.  Data Organization

   The top-level element is used
        to conceptually represent all possible values
        for called <nacm>, and it is defined in the particular leaf using this
   'ietf-netconf-acm' module namespace.

   There are several data type.";
   }

   typedef nacm-rights-type {
     type union {
       type nacm-matchall-string-type;

       type bits {
         bit create {
           description
             "Create access allowed to all specified data.
              Any protocol operation that creates a
              new instance structures defined as child nodes of the specified data is a create
              operation.";
         }
         bit read {
           description
             "Read access allowed
   <nacm> element:

   leaf <enable-nacm>:  On/off boolean switch to all specified data.
              Any protocol operation enable or notification that
              returns data disable
      access control enforcement.

   leaf <read-default>:  Enumeration to an application is a permit or deny default read
              operation.";
         }
         bit update {
           description
             "Update
      access allowed requests.

   leaf <write-default>:  Enumeration to all specified data.
              Any protocol operation that alters an existing
              data node is an update operation.";
         }
         bit delete {
           description
             "Delete permit or deny default write
      access allowed requests.

   leaf <exec-default>:  Enumeration to all specified data.
              Any permit or deny default protocol
      operation that removes a database
              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 Rights.
        The string '*' indicates that all possible access
        rights apply to execution requests.

   leaf <denied-rpcs>:  Read-only counter of the access rule.  Otherwise, only number of times the specific access rights represented by
      server has denied an RPC operation request, since the bit names
        that are present apply to last reboot
      of the access rule.";
   }

   typedef nacm-group-name-type {
     type string {
       length "1..max";
       pattern "[^\*].*";
     }
     description
       "Name server.

   leaf <denied-data-writes>:  Read-only counter of administrative group that can be
        assigned to the user, and specified in
        an access control rule.";
   }

   typedef nacm-action-type {
     type enumeration {
       enum permit {
         description
           "Requested action is permitted.";
       }
       enum deny {
         description
           "Requested action is denied.";
       }
     }
     description
       "Action taken by number of times
      the server when has denied a particular
        rule matches.";

   }

   typedef schema-instance-identifier {
     type yang:xpath1.0;
     description
       "Path expression data node write request, since the last
      reboot of the server.

   container <groups>:  Configures the groups used to represent a special
        schema-instance identifier string. within the access
      control system.

      list <group>:  A schema-instance-identifier value is an
        unrestricted YANG instance-identifier expression.
        All 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 as an instance-identifier apply
        except predicates for keys are optional.  If a key
        predicate is missing, then
         specific module.

      list <rpc-rule>:  Configures the schema-instance-identifier
        represents all possible server instances access control rules for that key.

        This XPath expression is evaluated in the following context:

          o  The set of namespace declarations are those in scope on protocol
         operation invocation.

      list <data-rule>:  Configures the leaf element where this type is used.

          o  The set of variable bindings contains one variable,
             'USER', which contains access control rules for
         configuration datastore access.

      list <notification-rule>:  Configures the name of user access control rules for
         controlling delivery of the current
              session.

          o <notification> events.

3.4.3.  YANG Module

   The function library following YANG module is provided to specify the core function library, but
             note normative
   NETCONF content that due to must by supported by the syntax restrictions of an
             instance-identifier, no functions are allowed.

          o server.

   The context node is ietf-netconf-acm YANG module imports typedefs from [RFC6021].

   // RFC Ed.: please update the root node in date to the data tree.";
   }

   typedef md5-crypt date of publication
   <CODE BEGINS> file="ietf-netconf-acm@2011-02-03.yang"

   module ietf-netconf-acm {
     type string

     namespace "urn:ietf:params:xml:ns:yang:ietf-netconf-acm";

     prefix "nacm";

     import ietf-yang-types {
       pattern "$0$.* | $1$[a-zA-Z0-9./]{2,8}$.*";
       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>

        Editor:   Martin Bjorklund
                  <mailto:mbj@tail-f.com>";

     description
       "The md5-crypt type is used to store a password hash based on
       "NETCONF Server Access Control Model.

        Copyright (c) 2011 IETF Trust and the
        MD5 message digest algorithm.  When a clear text value is set to
        a leaf persons identified as
        authors of this type, the server calculates a MD5 password hash, code. All rights reserved.

        Redistribution and stores the result use in source and binary forms, with or
        without modification, is permitted pursuant to, and subject
        to the datastore.  Thus, license terms contained in, the password is
        never stored Simplified BSD
        License set forth in clear text.

        When a leaf Section 4.c of this type is read, the stored password hash IETF Trust's
        Legal Provisions Relating to IETF Documents
        (http://trustee.ietf.org/license-info).

        This version of this YANG module is
        returned.

        A value 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 type matches one of note
     // Note: extracted from draft-ietf-netconf-access-control-02.txt

     // RFC Ed.: please update the forms:

          $0$<clear text password>
          $1$<salt>$<password hash>

       The '$0$' prefix signals date to the date of publication
     revision "2011-02-03" {
       description
         "Initial version";
       reference
         "RFC XXXX: Network Configuration Protocol
                    Access Control Model";
     }

     /*
      * Extension statements
      */

     extension secure {
       description
         "Used to indicate that the value is clear text.  When
       such data model node
          represents a value is received by sensitive security system parameter.

          If present, the server, an MD5 digest is
       calculated, and NETCONF server will only allow
          the string '$1$<salt>$' is prepended designated 'superuser' to have write or execute
          default nacm-rights-type for the
       result, where <salt> node.  An explicit access
          control rule is required for all other users.

          The 'secure' extension may appear within a random 2-8 characters long salt used
       to generate the digest.  This value data, rpc,
          or notification node definition.  It is stored in ignored
          otherwise.";
     }

     extension very-secure {
       description
         "Used to indicate that the
       configuration data store.

       If model node
          controls a value starting with '$1$<salt>$' is received, very sensitive security system parameter.

          If present, the NETCONF server
       knows that the value already represents an MD5 digest, and
       stores it as is in will only allow
          the data store.

       When a server needs designated 'superuser' to verify a password given by a user, it
       finds the stored password hash string have read, write, or execute
          default nacm-rights-type for that user, extracts
       the salt, and calculates the hash with the salt and given
       password as input.  If the calculated hash value is the same as
       the stored value, the password given by the client is correct.

       The digest algorithm node.  An explicit access
          control rule is the md5 crypt function used for
       encrypting passwords required for various UNIX systems.";
     reference
       "RFC 1321: all other users.

          The MD5 Message-Digest Algorithm
        http://en.wikipedia.org/wiki/Crypt_(Unix)";
          // FIXME: ref to wikipedia ok?? 'very-secure' extension may appear within a data, rpc,
          or notification node definition.  It is ignored
          otherwise.";
     }

   container nacm

     /*
      * Derived types
      */

     typedef nacm-user-name-type {
       type string {
     nacm:very-secure;

     presence
       "An empty nacm container indicates that the
        NACM service is running, and using
        all default parameters.";
         length "1..max";
       }
       description
       "Parameters for NETCONF Access Control Model.";

     container authentication
         "General Purpose User Name string.";
     }

     typedef nacm-matchall-string-type {
       nacm:very-secure;
       if-feature authentication;
       type string {
         pattern "\*";
       }
       description
         "The authentication configuration string containing a single asterisk '*' is used
          to conceptually represent all possible values
          for the
          NETCONF server.";

       leaf-list user-authentication-order particular leaf using this data type.";
     }

     typedef nacm-rights-type {
       type union {
         type identityref nacm-matchall-string-type;

         type bits {
           base authentication-method;
         }
         must '(. = "nacm:radius" and ../radius/server) or'
            + '(. != "nacm:radius")' {
           error-message
             "When 'radius'
           bit create {
             description
               "Create access allowed to all specified data.
                Any protocol operation that creates a
                new instance of the specified data is used, a radius server
              must be configured."; create
                operation.";
           }
         ordered-by user;
           bit read {
             description
           "When the NETCONF server authenticates a user with
            a password, it tries the authentication methods in this
            leaf-list in order.  If authentication with one method
            fails, the next method
               "Read access allowed to all specified data.
                Any protocol operation or notification that
                returns data to an application is used.  If no method succeeds,
            the user a read
                operation.";
           }
           bit update {
             description
               "Update access allowed to all specified data.
                Any protocol operation that alters an existing
                data node is denied access.

            If the 'radius' feature an update operation.";
           }
           bit delete {
             description
               "Delete access allowed to all specified data.
                Any protocol operation that removes a database
                node instance is advertised by the NETCONF
            server, the 'radius' identity can be added a delete operation.";
           }
           bit exec {
             description
               "Execution access to this
            list.

            If the 'local-users' feature specified RPC operation.
                Any RPC operation invocation is advertised by the
            NETCONF server, the 'local-users' identity can be
            added to this list."; an exec operation.";
           }
         }
       }

       container radius {
         if-feature radius;
       description
           "The radius configuration for
         "NETCONF Access Rights.
          The string '*' indicates that all possible access
          rights apply to the NETCONF server.";

         list server {
           key address;

           description
             "The radius server configuration used access rule.  Otherwise, only
          the specific access rights represented by the NETCONF server.";

           leaf address {
             type inet:host;
             description
               "The address of bit names
          that are present apply to the radius server."; access rule.";
     }
           leaf port

     typedef nacm-group-name-type {
       type inet:port-number;
             default "1812";
             description
              "The port number of the radius server.";
           }
           leaf shared-secret string {
             type string; // FIXME
 /*
   We're using a special type aes-cfb-128-encrypted-string which works
   like the md5-crypt string, but encrypts the clear text value using a
   pre-provisioned password (not part
         length "1..max";
         pattern "[^\*].*";
       }
       description
         "Name of the config db!).

   We use $0$ for cleartext and $4$ for the encrypted value.
   (we also have a des-version which uses $3$).

   But I was thinking administrative group that maybe we could define a type for encrypted
   values without specifying the encryption algorithm, just specifying
   the format.  $0$<clear text> | $x$<encrypted value>, and how it is
   encrypted is implementation specific.

   One alternative is to store this shared secret in clear text.  It is
   transmitted over a secure transport, and marked as very-secure.  (The
   same argument could be made for user passwords, but these are
   personal and not even root should can be able to read my passwd in clear
   text, so it makes more sense to keep them hidden.)
  */
             description
               "The shared secret which is known
          assigned to both the RADIUS
                client and server.";
             reference
               "RFC 2865: Remote Authentication Dial In User Service";
           }
           /*
             How about configuration of number of retransmits user, and timeout?
            */
         } specified in
          an access control rule.";
     }

       list user {
         if-feature local-users;
         key name;

         description
           "The list of local users configured on this device.";

         leaf name

     typedef nacm-action-type {
       type nacm-user-name-type; enumeration {
         enum permit {
           description
            "The user name string identifying this entry.";
             "Requested action is permitted.";
         }
         leaf password
         enum deny {
           type md5-crypt;
           description
             "The password for this entry.";
             "Requested action is denied.";
         }
       }
       description
         "Action taken by the server when a particular
          rule matches.";
     }
         leaf ssh-dsa

     typedef schema-instance-identifier {
       type binary; yang:xpath1.0;
       description
             "The public DSA
         "Path expression used to represent a special
          schema-instance identifier string.

          A schema-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 schema-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 entry."; 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.";
     }
         leaf ssh-rsa

     container nacm {
           type binary;
       nacm:very-secure;

       description
             "The public RSA key
         "Parameters for this entry.";
         }
       }
     } NETCONF Access Control Model.";

       leaf enable-nacm {
         type boolean;
         default true;
         description
           "Enable or disable all NETCONF access control
            enforcement.  If 'true', then enforcement
            is enabled.  If 'false', then enforcement
            is disabled.";
       }

       leaf read-default {
         type nacm-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 nacm-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 nacm-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.";
       }

       container groups {
         description
           "NETCONF Access Control Groups.";

         list group {
           key name;

           description
             "One NACM Group Entry.";

           leaf name {
             type nacm-group-name-type;
             description
               "Group name associated with this entry.";
           }

           leaf-list user-name {
             type nacm-user-name-type;
             description
               "Each entry identifies the user name of
                a member of the group associated with
                this entry.";
           }
         }
       }
       container rules {
         description
           "NETCONF Access Control Rules.";

         grouping common-rule-parms {
           description
             "Common rule parameters.";

           leaf rule-name {
             type string {
               length "1..256";
             }
             description
               "Arbitrary name assigned to the
                access control rule.";
           }

           leaf allowed-rights {
             type nacm-rights-type;
             description
               "List of access rights granted to
                specified administrative groups for the
                content specified by the associated path.";
           }

           leaf-list allowed-group {
             type union {
               type nacm-matchall-string-type;
               type nacm-group-name-type;
             }
             min-elements 1;
             description
               "List of administrative groups which will be
                assigned the associated access rights
                for the content specified by the associated path.

                The string '*' indicates that all configured
                administrative groups apply to the entry.";
           }

           leaf nacm-action {
             type nacm-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 {
               length "1..4095";
             }
             description
               "A textual description of the access rule.";
           }
         }

         list module-rule {
           key "module-name rule-name";
           ordered-by user;

           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, and the requested operation
              is included in the 'allowed-rights' leaf.";

           leaf module-name {
             type string;
             description
               "Name of the module associated with this rule.";
           }

           uses common-rule-parms {
             refine allowed-rights {
               mandatory true;
             }
           }
         }

         list rpc-rule {
           key "module-name rpc-name rule-name";
           ordered-by user;

           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 '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.  The 'allowed-rights' leaf
              is ignored by the server if it is present.
              Only the 'exec' bit can possibly cause
              a match for an RPC rule.";

           leaf module-name {
             type string;
             description
               "Name of the module defining this RPC operation.";
           }

           leaf rpc-name {
             type string;
             description
               "Name of the RPC operation.";
           }

           uses common-rule-parms;
         }

         list data-rule {
           key "rule-name";
           ordered-by user;

           description
             "One Data Access Control Rule.

              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,
              and the requested operation is included in the
              'allowed-rights' leaf.";

           leaf path {
             type schema-instance-identifier;
             mandatory true;
             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.";
           }

           uses common-rule-parms {
             refine allowed-rights {
               mandatory true;
             }
           }
         }

         list notification-rule {
           key "module-name
                notification-name
                rule-name";
           ordered-by user;

           description
             "One Notification Access Rule.

              A notification is considered a match if the module name of
              the requested event type matches
              '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.  If the 'allowed-rights'
              leaf is present, it is ignored by the server.
              Only the 'read' bit can possibly cause
              a match for a notification rule.";

           leaf module-name {
             type string;
             description
               "Name of the module defining this
                notification event type.";
           }

           leaf notification-name {
             type string;
             description
               "Name of the notification event.";
           }

           uses common-rule-parms;
         }
       }

     }
   }

   <CODE ENDS>

                                 Figure 5

5.5.

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-nacm 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"
   registry.  Following the format in [RFC6020], the following has been
   registered.

        name: ietf-nacm ietf-netconf-acm
        namespace: urn:ietf:params:xml:ns:yang:ietf-nacm 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

5.6.

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 'superuser' account,
   which can be used to bypass access control enforcement.  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 protocol operations
   will have undocumented side effects.  An administrator should
   construct access control rules such that the configuration database datastore
   is protected from such side effects.  Also, such RPC protocol operations
   should never be invoked by a session using the 'superuser'
   administrative user.

   There is a risk that non-standard RPC 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 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
   which could be considered sensitive.

   o  enable-nacm

   o  read-default

   o  write-default

   o  exec-default

   o  groups
   o  rules

6.

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.

   [RFC2865]  Rigney, C., Willens, S., Rubens, A., and W. Simpson,
              "Remote Authentication Dial In User Service (RADIUS)",
              RFC 2865, June 2000.

   [RFC3688]  Mealling, M., "The IETF XML Registry", BCP 81, RFC 3688,
              January 2004.

   [RFC4252]  Ylonen, T.

   [RFC5277]  Chisholm, S. and C. Lonvick, "The Secure Shell (SSH)
              Authentication Protocol", H. Trevino, "NETCONF Event
              Notifications", RFC 4252, January 2006.

   [RFC4253]  Ylonen, T. and C. Lonvick, "The Secure Shell (SSH)
              Transport Layer Protocol", 5277, July 2008.

   [RFC6020]  Bjorklund, M., "YANG - A Data Modeling Language for the
              Network Configuration Protocol (NETCONF)", RFC 4253, January 2006.

   [RFC4741] 6020,
              October 2010.

   [RFC6021]  Schoenwaelder, J., "Common YANG Data Types", RFC 6021,
              October 2010.

   [I-D.ietf-netconf-4741bis]
              Enns, R., "NETCONF Bjorklund, M., Schoenwaelder, J., and A.
              Bierman, "Network Configuration Protocol", RFC 4741,
              December 2006.

   [RFC4742] Protocol (NETCONF)",
              draft-ietf-netconf-4741bis-07 (work in progress),
              January 2011.

   [I-D.ietf-netconf-rfc4742bis]
              Wasserman, M. and T. Goddard, "Using the NETCONF
              Configuration Protocol over Secure SHell Shell (SSH)", RFC 4742,
              December 2006.

   [RFC5277]  Chisholm, S.
              draft-ietf-netconf-rfc4742bis-06 (work in progress),
              January 2011.

4.2.  Informative References

   [RFC2865]  Rigney, C., Willens, S., Rubens, A., and H. Trevino, "NETCONF Event
              Notifications", W. Simpson,
              "Remote Authentication Dial In User Service (RADIUS)",
              RFC 5277, July 2008. 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.

   [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.

   [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>.

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.

   <nacm xmlns="urn:ietf:params:xml:ns:yang:ietf-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 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'.

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.

   <nacm xmlns="urn:ietf:params:xml:ns:yang:ietf-nacm"> xmlns="urn:ietf:params:xml:ns:yang:ietf-netconf-acm">
     <rules>
       <module-rule>
         <module-name>ietf-netconf-monitoring</module-name>
         <rule-name>mod-1</rule-name>
         <allowed-rights>*</allowed-rights>
         <allowed-group>guest</allowed-group>
         <nacm-action>deny</nacm-action>
         <comment>
             Do not allow guests any access to the netconf
             monitoring information.
         </comment>
       </module-rule>

       <module-rule>
         <module-name>ietf-netconf-monitoring</module-name>
         <rule-name>mod-2</rule-name>
         <allowed-rights>read</allowed-rights>
         <allowed-group>monitor</allowed-group>
         <nacm-action>permit</nacm-action>
         <comment>
             Allow the monitor group read access to the netconf
             monitoring information.
         </comment>
       </module-rule>

       <module-rule>
         <module-name>*</module-name>
         <rule-name>mod-3</rule-name>
         <allowed-rights>exec</allowed-rights>
         <allowed-group>monitor</allowed-group>
         <nacm-action>permit</nacm-action>
         <comment>
             Allow the monitor group to invoke any of the
             supported server operations.
         </comment>
       </module-rule>
       <module-rule>
         <module-name>*</module-name>
         <rule-name>mod-4</rule-name>
         <allowed-rights>*</allowed-rights>
         <allowed-group>admin</allowed-group>
         <nacm-action>permit</nacm-action>
         <comment>
             Allow the admin group complete access to all
             operations and data.
         </comment>
       </module-rule>

     </rules>
   </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 RPC 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 RPC protocol
   operation.

   <nacm xmlns="urn:ietf:params:xml:ns:yang:ietf-nacm"> xmlns="urn:ietf:params:xml:ns:yang:ietf-netconf-acm">
     <rules>
       <rpc-rule>
         <module-name>ietf-netconf</module-name>
         <rpc-name>kill-session</rpc-name>
         <rule-name>rpc-1</rule-name>
         <allowed-group>monitor</allowed-group>
         <allowed-group>guest</allowed-group>
         <nacm-action>deny</nacm-action>
         <comment>
           Do not allow the monitor or guest group
           to kill another session.
         </comment>
       </rpc-rule>

       <rpc-rule>
         <module-name>ietf-netconf</module-name>
         <rpc-name>delete-config</rpc-name>
         <rule-name>rpc-2</rule-name>
         <allowed-group>monitor</allowed-group>
         <allowed-group>guest</allowed-group>
         <nacm-action>deny</nacm-action>
         <comment>
           Do not allow monitor or guest group
           to delete any configurations.
         </comment>
       </rpc-rule>

       <rpc-rule>
         <module-name>ietf-netconf</module-name>
         <rpc-name>edit-config</rpc-name>
         <rule-name>rpc-3</rule-name>
         <allowed-group>monitor</allowed-group>
         <nacm-action>permit</nacm-action>
         <comment>
           Allow the monitor group to edit the configuration.
         </comment>
       </rpc-rule>
     </rules>
   </nacm>

   This example shows 3 RPC protocol operation rules:

   rpc-1:  This rule prevents the monitor or guest groups from invoking
      the NETCONF <kill-session> RPC protocol operation.

   rpc-2:  This rule prevents the monitor or guest groups from invoking
      the NETCONF <delete-config> RPC protocol operation.

   rpc-3:  This rule allows the monitor group to invoke the NETCONF
      <edit-config> RPC protocol operation.  This rule will have no real
      affect 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-nacm"> xmlns="urn:ietf:params:xml:ns:yang:ietf-netconf-acm">
     <rules>
       <data-rule>
         <rule-name>data-1</rule-name>
         <path>/nacm</path>
         <allowed-rights>*</allowed-rights>
         <allowed-group>guest</allowed-group>
         <nacm-action>deny</nacm-action>
         <comment>
           Deny the guest group any access to the /nacm data.
         </comment>
       </data-rule>

       <data-rule>
         <rule-name>data-acme-config</rule-name>
         <path xmlns:acme="http://example.com/ns/netconf">
           /acme:acme-netconf/acme:config-parameters
         </path>
         <allowed-rights>read create update delete</allowed-rights>
         <allowed-group>monitor</allowed-group>
         <nacm-action>permit</nacm-action>
         <comment>
           Allow the monitor group complete access to the acme
           netconf configuration parameters.  Showing long form
           of 'allowed-rights' instead of shorthand.
         </comment>
       </data-rule>

       <data-rule>
         <rule-name>dummy-itf</rule-name>
         <path xmlns:acme="http://example.com/ns/itf">
           /acme:interfaces/acme:interface[acme:name='dummy']

         </path>
         <allowed-rights>read update</allowed-rights>
         <allowed-group>monitor</allowed-group>
         <allowed-group>guest</allowed-group>
         <nacm-action>permit</nacm-action>
         <comment>
           Allow the monitor and guest groups read
           and update access to the dummy interface.
         </comment>
       </data-rule>

       <data-rule>
         <rule-name>admin-itf</rule-name>
         <path xmlns:acme="http://example.com/ns/itf">
           /acme:interfaces/acme:interface
         </path>
         <allowed-rights>*</allowed-rights>
         <allowed-group>admin</allowed-group>
         <nacm-action>permit</nacm-action>
         <comment>
           Allow admin full access to all acme interfaces.
           This is an example of an unreachable rule,
           because the admin group already has full access
           to all modules (see rule 'mod-4').
           All 'module-rule' entries will be checked
           before this 'data-rule' entry is checked.
         </comment>
       </data-rule>
     </rules>
   </nacm>

   This example shows 4 data rules:

   data-1:  This rule denies the guest group any access to the <nacm>
      sub-tree.  Note that the default namespace is only applicable
      because this sub-tree 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-nacm"> xmlns="urn:ietf:params:xml:ns:yang:ietf-netconf-acm">
     <rules>
       <notification-rule>
         <module-name>acme-system</module-name>
         <notification-name>sys-config-change</notification-name>
         <rule-name>notif-1</rule-name>
         <allowed-group>monitor</allowed-group>
         <allowed-group>guest</allowed-group>
         <nacm-action>deny</nacm-action>
         <comment>
           Do not allow the guest or monitor groups
           to receive config change events.
         </comment>
       </notification-rule>
     </rules>
   </nacm>

   This example shows 1 notification rule:

   notif-1:  This rule prevents the monitor or guest groups from
      receiving the acme <sys-config-change> event type.

Appendix B.  Open Issues  Change Log

   -- RFC Ed.: remove this section before publication.

   1.  Do modules need to be identified by their XML namespace URI, or
       is the

B.1.  01-02

   Removed authentication text and objects.

   Changed 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 from ietf-nacm 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 ietf-netconf-acm.

   Updated NETCONF 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 terminology.

   Removed open issues section.

   Changed some must to install a factory default <nacm> container if needed.

Appendix C.  Change Log

   -- RFC Ed.: remove this section before publication.

C.1. MUST in requirements section.

B.2.  00-01

   Updated YANG anf YANG Types references.

   Updated module namespace URI to standard format.

   Updated module header meta-data to standard format.

   Filled in IANA section.

C.2.

B.3.  00

   Initial version cloned from
   draft-bierman-netconf-access-control-02.txt.

Authors' Addresses

   Andy Bierman
   Brocade

   Email: andy.bierman@brocade.com

   Martin Bjorklund
   Tail-f Systems

   Email: mbj@tail-f.com