Internet Engineering Task Force A. Bierman Internet-Draft Brocade Intended status: Standards Track M. Bjorklund Expires: December 16, 2011 Tail-f Systems June 14, 2011 Network Configuration Protocol Access Control Model draft-ietf-netconf-access-control-04 Abstract The standardization of network configuration interfaces for use with the NETCONF protocol requires a structured and secure operating environment that promotes human usability and multi-vendor interoperability. There is a need for standard mechanisms to restrict NETCONF protocol access for particular users to a pre- configured subset of all available NETCONF operations and content. This document discusses requirements for a suitable access control model, and provides one solution that meets these requirements. Status of this Memo This Internet-Draft is submitted in full conformance with the provisions of BCP 78 and BCP 79. Internet-Drafts are working documents of the Internet Engineering Task Force (IETF). Note that other groups may also distribute working documents as Internet-Drafts. The list of current Internet- Drafts is at http://datatracker.ietf.org/drafts/current/. Internet-Drafts are draft documents valid for a maximum of six months and may be updated, replaced, or obsoleted by other documents at any time. It is inappropriate to use Internet-Drafts as reference material or to cite them other than as "work in progress." This Internet-Draft will expire on December 16, 2011. Copyright Notice Copyright (c) 2011 IETF Trust and the persons identified as the document authors. All rights reserved. This document is subject to BCP 78 and the IETF Trust's Legal Provisions Relating to IETF Documents (http://trustee.ietf.org/license-info) in effect on the date of publication of this document. Please review these documents carefully, as they describe your rights and restrictions with respect Bierman & Bjorklund Expires December 16, 2011 [Page 1] Internet-Draft NACM June 2011 to this document. Code Components extracted from this document must include Simplified BSD License text as described in Section 4.e of the Trust Legal Provisions and are provided without warranty as described in the Simplified BSD License. Table of Contents 1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . . 4 1.1. Terminology . . . . . . . . . . . . . . . . . . . . . . . 4 1.1.1. Requirements Notation . . . . . . . . . . . . . . . . 4 1.1.2. NETCONF Terms . . . . . . . . . . . . . . . . . . . . 4 1.1.3. YANG Terms . . . . . . . . . . . . . . . . . . . . . . 5 1.1.4. NACM Terms . . . . . . . . . . . . . . . . . . . . . . 5 2. Access Control Design Objectives . . . . . . . . . . . . . . . 6 2.1. Protocol Control Points . . . . . . . . . . . . . . . . . 6 2.2. Simplicity . . . . . . . . . . . . . . . . . . . . . . . . 7 2.3. Procedural Interface . . . . . . . . . . . . . . . . . . . 7 2.4. Datastore Access . . . . . . . . . . . . . . . . . . . . . 8 2.4.1. Access Rights . . . . . . . . . . . . . . . . . . . . 8 2.4.2. and Operations . . . . . . . . . . 8 2.4.3. Operation . . . . . . . . . . . . . . . 9 2.4.4. Operation . . . . . . . . . . . . . . . 10 2.5. Users and Groups . . . . . . . . . . . . . . . . . . . . . 10 2.6. Maintenance . . . . . . . . . . . . . . . . . . . . . . . 11 2.7. Configuration Capabilities . . . . . . . . . . . . . . . . 11 2.8. Identifying Security Holes . . . . . . . . . . . . . . . . 11 2.9. Data Shadowing . . . . . . . . . . . . . . . . . . . . . . 12 2.10. NETCONF Specific Requirements . . . . . . . . . . . . . . 12 3. NETCONF Access Control Model (NACM) . . . . . . . . . . . . . 14 3.1. Introduction . . . . . . . . . . . . . . . . . . . . . . . 14 3.1.1. Features . . . . . . . . . . . . . . . . . . . . . . . 14 3.1.2. External Dependencies . . . . . . . . . . . . . . . . 15 3.1.3. Message Processing Model . . . . . . . . . . . . . . . 15 3.2. Model Components . . . . . . . . . . . . . . . . . . . . . 17 3.2.1. Users . . . . . . . . . . . . . . . . . . . . . . . . 17 3.2.2. Groups . . . . . . . . . . . . . . . . . . . . . . . . 17 3.2.3. Sessions . . . . . . . . . . . . . . . . . . . . . . . 18 3.2.4. Access Permissions . . . . . . . . . . . . . . . . . . 18 3.2.5. Global Enforcement Controls . . . . . . . . . . . . . 18 3.2.5.1. enable-nacm Switch . . . . . . . . . . . . . . . . 18 3.2.5.2. read-default Switch . . . . . . . . . . . . . . . 19 3.2.5.3. write-default Switch . . . . . . . . . . . . . . . 19 3.2.5.4. exec-default Switch . . . . . . . . . . . . . . . 19 3.2.6. Access Control Rules . . . . . . . . . . . . . . . . . 20 3.3. Access Control Enforcement Procedures . . . . . . . . . . 20 3.3.1. Initial Operation . . . . . . . . . . . . . . . . . . 20 3.3.2. Session Establishment . . . . . . . . . . . . . . . . 21 Bierman & Bjorklund Expires December 16, 2011 [Page 2] Internet-Draft NACM June 2011 3.3.3. "access-denied" Error Handling . . . . . . . . . . . . 21 3.3.4. Incoming RPC Message Validation . . . . . . . . . . . 21 3.3.5. Data Node Access Validation . . . . . . . . . . . . . 24 3.3.6. Outgoing Authorization . . . . . . . . 26 3.4. Data Model Definitions . . . . . . . . . . . . . . . . . . 28 3.4.1. Data Organization . . . . . . . . . . . . . . . . . . 28 3.4.2. YANG Module . . . . . . . . . . . . . . . . . . . . . 29 3.5. IANA Considerations . . . . . . . . . . . . . . . . . . . 38 3.6. Security Considerations . . . . . . . . . . . . . . . . . 39 4. References . . . . . . . . . . . . . . . . . . . . . . . . . . 41 4.1. Normative References . . . . . . . . . . . . . . . . . . . 41 4.2. Informative References . . . . . . . . . . . . . . . . . . 41 Appendix A. Usage Examples . . . . . . . . . . . . . . . . . . . 42 A.1. Example . . . . . . . . . . . . . . . . . . . . . 42 A.2. Module Rule Example . . . . . . . . . . . . . . . . . . . 43 A.3. RPC Rule Example . . . . . . . . . . . . . . . . . . . . . 44 A.4. Data Rule Example . . . . . . . . . . . . . . . . . . . . 46 A.5. Notification Rule Example . . . . . . . . . . . . . . . . 48 Appendix B. Change Log . . . . . . . . . . . . . . . . . . . . . 50 B.1. 03-04 . . . . . . . . . . . . . . . . . . . . . . . . . . 50 B.2. 02-03 . . . . . . . . . . . . . . . . . . . . . . . . . . 50 B.3. 01-02 . . . . . . . . . . . . . . . . . . . . . . . . . . 50 B.4. 00-01 . . . . . . . . . . . . . . . . . . . . . . . . . . 50 B.5. 00 . . . . . . . . . . . . . . . . . . . . . . . . . . . . 51 Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . . 52 Bierman & Bjorklund Expires December 16, 2011 [Page 3] Internet-Draft NACM June 2011 1. Introduction The NETCONF protocol does not provide any standard mechanisms to restrict the operations and content that each user is authorized to use. There is a need for inter-operable management of the controlled access to operator selected portions of the available NETCONF content within a particular server. This document addresses access control mechanisms for the Operation and Content layers of NETCONF, as defined in [I-D.ietf-netconf-4741bis], and [RFC5277]. It contains three main sections: 1. Access Control Design Objectives 2. NETCONF Access Control Model (NACM) 3. YANG Data Model (ietf-netconf-acm.yang) 1.1. Terminology 1.1.1. Requirements Notation The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT", "SHOULD", "SHOULD NOT", "RECOMMENDED", "MAY", and "OPTIONAL" in this document are to be interpreted as described in [RFC2119]. 1.1.2. NETCONF Terms The following terms are defined in [I-D.ietf-netconf-4741bis] and are not redefined here: o client o datastore o operation o protocol operation o server o session o user Bierman & Bjorklund Expires December 16, 2011 [Page 4] Internet-Draft NACM June 2011 1.1.3. YANG Terms The following terms are defined in [RFC6020] and are not redefined here: o data node o data definition statement 1.1.4. NACM Terms The following terms are used throughout this documentation: access control: A security feature provided by the NETCONF server, that allows an operator to restrict access to a subset of all NETCONF protocol operations and data, based on various criteria. access control model (ACM): A conceptual model used to configure and monitor the access control procedures desired by the operator to enforce a particular access control policy. access control rule: The conceptual criteria used to determine if a particular NETCONF protocol operation will be permitted or denied. access operation: How a request attempts to access a conceptual object. One of "read", "create", "delete", "update", and "execute". recovery session: A special administrative session that is given unlimited NETCONF access, and is exempt from all access control enforcement. The specific mechanism(s) used by an implementation to control and identify whether a session is a recovery session or not are outside the scope of this document. Bierman & Bjorklund Expires December 16, 2011 [Page 5] Internet-Draft NACM June 2011 2. Access Control Design Objectives [Editor's note: some things described here are requirements (MUST, SHOULD, etc), but some things are descriptions how NACM works, e.g. 2.4.1, 2.4.3...] 2.1. Protocol Control Points The NETCONF protocol allows new operations to be added at any time, and the YANG data modeling language supports this feature. It is not possible to design an ACM for NETCONF which only focuses on a static set of operations, like some other protocols. Since few assumptions can be made about an arbitrary protocol operation, the NETCONF architectural server components need to be protected at several conceptual control points. +-------------+ +-------------+ client | protocol | | prune | client request --> | operation | | restricted | ---> reply | allowed? | | | +-------------+ | nodes? | | +-------------+ | if any datastore or | state data is accessed | by the operation V +-------------+ +----------------+ | data node | | prune | | access | | restricted | | allowed? | | | ---> client +-------------+ | event or data? | session +----------------+ Figure 1 The following access control points are defined: protocol operation: Configurable permission to invoke specific protocol operations is required. Wildcard or multiple target mechanisms to reduce configuration and effort are also required. NETCONF datastore: Configurable permission to read and/or alter specific data nodes within any conceptual datastore is required. Wildcard or multiple target mechanisms to reduce configuration and effort are also required. Bierman & Bjorklund Expires December 16, 2011 [Page 6] Internet-Draft NACM June 2011 RPC Reply Content: Configurable permission to read specific data nodes within any conceptual RPC output section is required. Unauthorized data is silently omitted from the reply, instead of dropping the reply or sending an "access-denied" error. Notification Content: Configurable permission to receive specific notification event types is required. 2.2. Simplicity Experience has shown that a complicated ACM will not be widely deployed, because it is too hard to use. The key factor that is ignored in such solutions is the concept of "localized cost". It needs to be easy to do simple things, and possible to do complex things, instead of hard to do everything. Configuration of the access control system needs to be as simple as possible. Simple and common tasks need to be easy to configure, and require little expertise or domain-specific knowledge. Complex tasks are possible using additional mechanisms, which may require additional expertise. A single set of access control rules SHOULD be able to control all types of NETCONF protocol operation invocation, all conceptual datastore access, and all NETCONF session output. Access control SHOULD be defined with a small and familiar set of permissions, while still allowing full control of NETCONF datastore access. Access control does not need to be applied to NETCONF messages. 2.3. Procedural Interface The NETCONF protocol uses a procedural interface model, and an extensible set of protocol operations. Access control for any possible protocol operation is required. It MUST be possible to configure the ACM to permit or deny access to specific NETCONF operations. YANG modules SHOULD be designed so that different access levels for input parameters to protocol operations is not required. Use of generic operations should be avoided, and separate operations defined instead, if different access levels are needed. Bierman & Bjorklund Expires December 16, 2011 [Page 7] Internet-Draft NACM June 2011 2.4. Datastore Access It MUST be possible to control access to specific nodes and subtrees within the conceptual NETCONF datastore. The same access control rules apply to all conceptual datastores. For example, the candidate configuration or the running configuration. Only the standard NETCONF datastores (candidate, running, and startup) are controlled by the ACM. Local or remote files or datastores accessed via the parameter are optional to support. The non-volatile startup configuration needs to be loaded at boot- time into the running configuration without applying any access control rules. Access control is applied after the server has booted, and user sessions are active. 2.4.1. Access Rights A small set of hard-wired datastore access rights is needed to control access to all possible NETCONF datastore operations, including vendor extensions to the standard operation set. The familiar "CRUDX" model can support all NETCONF operations: o Create: Allows the client to add a new data node instance to a datastore. o Read: Allows the client to read a data node instance from a datastore, or receive the notification event type. o Update: Allows the client to update an existing data node instance in a datastore. o Delete: Allows the client to delete a data node instance from a datastore. o eXec: Allows the client to execute the protocol operation. 2.4.2. and Operations Data nodes to which the client does not have read access, either directly or via wildcard access, are silently omitted from the message. This is done to allow NETCONF filters for and to function properly, instead of causing an "access- denied" error because the filter criteria would otherwise include unauthorized read access to some data nodes. For NETCONF filtering Bierman & Bjorklund Expires December 16, 2011 [Page 8] Internet-Draft NACM June 2011 purposes, the selection criteria is applied to the subset of nodes that the client is authorized to read, not the entire datastore. 2.4.3. Operation The NACM access rights are not directly coupled to the "operation" attribute, although they are similar. Instead, a NACM access right applies to all operations which would result in a particular access operation to the target datastore. This section describes how these access rights apply to the specific datastore operations supported by the operation. If the effective operation is "none" (i.e., default-operation="none") for a particular data node, then no access control is applied to that data node. A "create", "merge", or "replace" operation on a datastore node which would result in the creation of a new data node instance, for which the user does not have "create" access permission, is rejected with an "access-denied" error. A "merge" or "replace" operation on a datastore node which would result in the modification of an existing data node instance, for which the user does not have "update" access permission, is rejected with an "access-denied" error. A "replace", "delete", or "remove" operation on a datastore node which would result in the deletion of an existing data node instance, for which the user does not have "delete" access permission, is rejected with an "access-denied" error. A "merge" operation may include data nodes which do not alter portions of the existing datastore. For example, a container or list node may be present for naming purposes, but does not actually alter the corresponding datastore node. These unaltered data nodes within the scope of a "merge" operation are ignored by the server, and do not require any access rights by the client. [Editor's note: ditto for "replace" (and copy-config...) Note that with this rule, a client w/o read access can guess db content by sending merge requests - if access-denied is not returned, it means the db has that value.] A "merge" operation may include data nodes, but not include particular child data nodes that are present in the datastore. These missing data nodes within the scope of a "merge" operation are ignored by the server, and do not require any access rights by the client. Bierman & Bjorklund Expires December 16, 2011 [Page 9] Internet-Draft NACM June 2011 The contents of specific restricted datastore nodes MUST NOT be exposed in any elements within the reply. 2.4.4. Operation Access control for the operation requires special consideration because the operator is replacing the entire target datastore. Read access to the entire source datastore, and write access to the entire target datastore is needed for this operation to succeed. The server SHOULD determine the exact nodes in the target datastore which are actually different, and only check write access permissions for this set of nodes, which could be empty. For example, if a session can read the entire datastore, but only change one leaf, that session SHOULD be able to edit and save that one leaf. E.g., the operation from to SHOULD succeed if the only effective changes are for data nodes that session is authorized to change. A client MUST have access to every datastore node, even ones that are not present in the source configuration data. For example, consider a common use-case such as a simple backup and restore procedure. The operator (client) MUST have full read access to the datastore in order to receive a complete copy of its contents. If the server simply omits these subtrees from the reply, and that copy is later used to restore the server datastore, the server will interpret the missing nodes as a request to delete those nodes, and return an error. 2.5. Users and Groups The server MUST obtain a user name from the underlying NETCONF transport, such as an SSH user name. It MUST be possible to specify access control rules for a single user or a configurable group of users. The ACM MUST support the concept of administrative groups, to support the well-established distinction between a root account and other types of less-privileged conceptual user accounts. These groups MUST be configurable by the operator. It MUST be possible to delegate the user-to-group mapping to a central server, such as a RADIUS server [RFC2865] [RFC5607]. Since authentication is performed by the NETCONF transport layer, and RADIUS performs authentication and service authorization at the same Bierman & Bjorklund Expires December 16, 2011 [Page 10] Internet-Draft NACM June 2011 time, it MUST be possible for the underlying NETCONF transport to report a set of group names associated with the user to the server. 2.6. Maintenance It SHOULD be possible to disable part or all of the access control model without deleting any configuration. 2.7. Configuration Capabilities Suitable control and monitoring mechanisms are needed to allow an operator to easily manage all aspects of the ACM behavior. A standard data model, suitable for use with the operation MUST be available for this purpose. Access control rules to restrict operations on specific subtrees within the configuration datastore MUST be supported. Existing mechanisms can be used to identify the subtree(s) for this purpose. 2.8. Identifying Security Holes One of the most important aspects of the data model documentation, and biggest concerns during deployment, is the identification of security-sensitive content. This applies to operations in NETCONF, not just data and notifications. It is mandatory for security-sensitive objects to be documented in the Security Considerations section of an RFC. This is nice, but it is not good enough, for the following reasons: o This documentation-only approach forces operators to study the RFC and determine if there are any potential security holes introduced by a new YANG module. o If any security holes are identified, then the operator can study some more RFC text, and determine how to close the security hole(s). o The ACM on each server can be configured to close the security holes, e.g., require privileged access to read or write the specific data identified in the Security Considerations section. o If the ACM is not pre-configured, then there will be a time window of vulnerability, after the new module is loaded, and before the new access control rules for that module are configured, enabled, and debugged. Often, the operator just wants to disable default access to the Bierman & Bjorklund Expires December 16, 2011 [Page 11] Internet-Draft NACM June 2011 secure content, so no inadvertent or malicious changes can be made to the server. This allows the default rules to be more lenient, without significantly increasing the security risk. A data model designer needs to be able to use machine-readable statements to identify NETCONF content which needs to be protected by default. This will allow client and server tools to automatically close data-model specific security holes, by denying access to sensitive data unless the user is explicitly authorized to perform the requested operation. 2.9. Data Shadowing One of the more complicated security administration problems is identifying data nodes which shadow or mirror the content of another data node. An access control rule to prevent read operations for a particular node may be insufficient to prevent access to the data node with the copied value. If the description statement, other documentation, or no documentation exists to identify a data shadow problem, then it may not be detected. Since NETCONF allows any vendor operation to be added to the protocol, there is no way to reliably identify all of the operations that may expose copies of sensitive data nodes in messages. A NETCONF server MUST ensure that unauthorized access to its conceptual datastores and non-configuration data nodes is prevented. It is beyond the scope of this document to define access control enforcement procedures for underlying device instrumentation that may exist to support the NETCONF server operation. An operator can identify each operation that the server provides, and decide if it needs any access control applied to it. Proprietary protocol operations SHOULD be properly documented by the vendor, so it is clear to operators what data nodes (if any) are affected by the operation, and what information (if any) is returned in the message. 2.10. NETCONF Specific Requirements The server MUST be able to identify the specific protocol access request at the 4 access control points defined above. The server MUST be able to identify any datastore access request, Bierman & Bjorklund Expires December 16, 2011 [Page 12] Internet-Draft NACM June 2011 even for proprietary operations. A client MUST always be authorized to invoke the operation, defined in [I-D.ietf-netconf-4741bis]. A client MUST always be authorized to receive the and notification events, defined in [RFC5277] The set of module name strings used within one particular server MUST be unique. Bierman & Bjorklund Expires December 16, 2011 [Page 13] Internet-Draft NACM June 2011 3. NETCONF Access Control Model (NACM) 3.1. Introduction This section provides a high-level overview of the access control model structure. It describes the NETCONF protocol message processing model, and the conceptual access control requirements within that model. 3.1.1. Features The NACM data model provides the following features: o Independent control of RPC, data, and notification access. o Simple access control rules configuration data model that is easy to use. o The concept of an emergency recovery session is supported, but configuration of the server for this purpose is beyond the scope of this document. An emergency recovery session will bypass all access control enforcement, in order to allow it to initialize or repair the NACM configuration. o A simple and familiar set of datastore permissions is used. o Support for YANG security tagging (e.g., nacm:secure extension) allows default security modes to automatically exclude sensitive data. o Separate default access modes for read, write, and execute permissions. o Access control rules are applied to configurable groups of users. o The entire ACM can be disabled during operation, in order to debug operational problems. o Access control rules are simple to configure. o The number of denied protocol operation requests and denied datastore write requests can be monitored by the client. o Simple unconstrained YANG instance identifiers are used to configure access control rules for specific data nodes. Bierman & Bjorklund Expires December 16, 2011 [Page 14] Internet-Draft NACM June 2011 3.1.2. External Dependencies The NETCONF [I-D.ietf-netconf-4741bis] protocol is used for all management purposes within this document. It is expected that the mandatory transport mapping NETCONF Over SSH [I-D.ietf-netconf-rfc4742bis] is also supported by the server, and that the server has access to the user name associated with each session. The YANG Data Modeling Language [RFC6020] is used to define the NETCONF data models specified in this document. 3.1.3. Message Processing Model The following diagram shows the NETCONF message flow model, including the points at which access control is applied, during NETCONF message processing. Bierman & Bjorklund Expires December 16, 2011 [Page 15] Internet-Draft NACM June 2011 +-------------------------+ | session | | (username) | +-------------------------+ | ^ V | +--------------+ +---------------+ | message | | message | | dispatcher | | generator | +--------------+ +---------------+ | ^ ^ V | | +===========+ +-------------+ +----------------+ | |---> | | | | | acc. ctl | | generator | | generator | +===========+ +-------------+ +----------------+ | ^ ^ ^ V +------+ | | +-----------+ | +=============+ +================+ | | | | | | | | processor |-+ | acc. ctl | | access ctl | +-----------+ +=============+ +================+ | | ^ ^ V +----------------+ | | +===========+ | | | | data node | | | | | acc. ctl | -----------+ | | | +===========+ | | | | | | | | | V V V | | +---------------+ +-----------------+ | configuration | ---> | server | | datastore | | instrumentation | | | <--- | | +---------------+ +-----------------+ Figure 2 The following high-level sequence of conceptual processing steps is executed for each received message, if access control enforcement is enabled: o Access control is applied to all messages (except ) received by the server, individually, for each active session, unless the session is identified as a "recovery session". Bierman & Bjorklund Expires December 16, 2011 [Page 16] Internet-Draft NACM June 2011 o If the session is authorized to execute the specified RPC operation, then processing continues, otherwise the request is rejected with an "access-denied" error. o If the configuration datastore or conceptual state data is accessed by the protocol operation, then the data node access MUST be authorized. If the session is authorized to perform the requested operation on the requested data, then processing continues. The following sequence of conceptual processing steps is executed for each generated notification event, if access control enforcement is enabled: o Server instrumentation generates a conceptual notification, for a particular subscription. o The notification access control enforcer checks the notification event type, and if it is one which the session is not authorized to read, then the notification is dropped for that subscription. 3.2. Model Components This section defines the conceptual components related to access control model. 3.2.1. Users A "user" is the conceptual entity that is associated with the access permissions granted to a particular session. A user is identified by a string which MUST be unique within the server. As described in [I-D.ietf-netconf-4741bis], the user name string is derived from the transport layer during session establishment. If the transport layer cannot authenticate the user, the session is terminated. The server MAY support a "recovery session" mechanism, which will bypass all access control enforcement. This is useful for restricting initial access and repairing a broken access control configuration. 3.2.2. Groups Access to a specific NETCONF operation is granted to a session, associated with a group, not a user. A group is identified by its name. All group names MUST be unique Bierman & Bjorklund Expires December 16, 2011 [Page 17] Internet-Draft NACM June 2011 within the server. A group member is identified by a user name string. The same user may be configured in multiple groups. 3.2.3. Sessions A session is simply a NETCONF session, which is the entity that is granted access to specific NETCONF operations. A session is associated with a single user name for the lifetime of the session. 3.2.4. Access Permissions The access permissions are the NETCONF protocol specific set of permissions that have been assigned to a particular session. The same access permissions MUST stay in effect for the processing of a particular message. The server MUST use the access control rules in effect at the time the message is processed. The access control model treats protocol operation execution separately from configuration datastore access and outgoing messages: create: Permission to create conceptual server data. read: Read access to conceptual server data, and content. update: Permission to modify existing conceptual server data. delete: Permission to delete existing conceptual server data. exec: Permission to invoke a protocol operation. 3.2.5. Global Enforcement Controls There are four global controls that are used to help control how access control is enforced. 3.2.5.1. enable-nacm Switch A global "enable-nacm" on/off switch is provided to enable or disable all access control enforcement. When this global switch is set to Bierman & Bjorklund Expires December 16, 2011 [Page 18] Internet-Draft NACM June 2011 "true", then all access requested are checked against the access control rules, and only permitted if configured to allow the specific access request. When this global switch is set to "false", then all access requested are permitted. 3.2.5.2. read-default Switch An on/off "read-default" switch is provided to enable or disable default access to receive data in replies and notifications. When the "enable-nacm" global switch is set to "true", then this global switch is relevant, if no matching access control rule is found to explicitly permit or deny read access to the requested NETCONF datastore data or notification event type. When this global switch is set to "permit", and no matching access control rule is found for the NETCONF datastore read or notification event requested, then access is permitted. When this global switch is set to "deny", and no matching access control rule is found for the NETCONF datastore read or notification event requested, then access is denied. 3.2.5.3. write-default Switch An on/off "write-default" switch is provided to enable or disable default access to alter configuration data. When the "enable-nacm" global switch is set to "true", then this global switch is relevant, if no matching access control rule is found to explicitly permit or deny write access to the requested NETCONF datastore data. When this global switch is set to "permit", and no matching access control rule is found for the NETCONF datastore write requested, then access is permitted. When this global switch is set to "deny", and no matching access control rule is found for the NETCONF datastore write requested, then access is denied. 3.2.5.4. exec-default Switch An on/off "exec-default" switch is provided to enable or disable default access to execute protocol operations. When the "enable- nacm" global switch is set to "true", then this global switch is relevant, if no matching access control rule is found to explicitly permit or deny access to the requested NETCONF protocol operation. When this global switch is set to "permit", and no matching access control rule is found for the NETCONF protocol operation requested, Bierman & Bjorklund Expires December 16, 2011 [Page 19] Internet-Draft NACM June 2011 then access is permitted. When this global switch is set to "deny", and no matching access control rule is found for the NETCONF protocol operation requested, then access is denied. 3.2.6. Access Control Rules There are 4 types of rules available in NACM: module rule: Controls access for definitions in a specific module, identified by its name. protocol operation rule: Controls access for a specific protocol operation, identified by its module and name. data node rule: Controls access for a specific data node, identified by its path location within the conceptual XML document for the data node. notification rule: Controls access for a specific notification event type, identified by its module and name. 3.3. Access Control Enforcement Procedures There are seven separate phases that need to be addressed, four of which are related to the NETCONF message processing model. In addition, the initial start-up mode for a NETCONF server, session establishment, and "access-denied" error handling procedures also need to be considered. 3.3.1. Initial Operation Upon the very first start-up of the NETCONF server, the access control configuration will probably not be present. If it isn't, a server MUST NOT allow any write access to any session role except a "recovery session", if supported. Access control rules are not enforced before or while the non- volatile configuration data is processed and loaded into the running configuration, when the server is booting or rebooting. Access rules are enforced any time a request is initiated from a user session. Access control is not enforced for server-initiated access requests, such as the initial load of the running datastore, during bootup. Bierman & Bjorklund Expires December 16, 2011 [Page 20] Internet-Draft NACM June 2011 3.3.2. Session Establishment The access control model applies specifically to the well-formed XML content transferred between a client and a server, after session establishment has been completed, and after the exchange has been successfully completed. A server SHOULD NOT include any sensitive information in any elements within the exchange. Once session establishment is completed, and a user has been authenticated, the NETCONF transport layer reports the user name and a possibly empty set of group names associated with the user to the NETCONF server. The NETCONF server will enforce the access control rules, based on the supplied user name, group names, and the configuration data stored on the server. 3.3.3. "access-denied" Error Handling The "access-denied" error-tag is generated when the access control system denies access to either a request to invoke a protocol operation or a request to perform a particular operation on the configuration datastore. A server MUST NOT include any sensitive information in any elements within the response. 3.3.4. Incoming RPC Message Validation The diagram below shows the basic conceptual structure of the access control processing model for incoming NETCONF messages, within a server. Bierman & Bjorklund Expires December 16, 2011 [Page 21] Internet-Draft NACM June 2011 NETCONF server +------------+ | XML | | message | | dispatcher | +------------+ | | V +------------+ | NC-base NS | | | +------------+ | | | | | +-------------------------+ | +------------+ | V V V +-----------+ +---------------+ +------------+ | acme NS | | NC-base NS | | NC-base NS | | | | | | | +-----------+ +---------------+ +------------+ | | | | V V +----------------------+ | | | configuration | | datastore | +----------------------+ Figure 3 Access control begins with the message dispatcher. After the server validates the element, and determines the namespace URI and the element name of the protocol operation being requested, the RPC access control enforcer verifies that the session is authorized to invoke the protocol operation. The protocol operation is authorized by following these steps: 1. If the "enable-nacm" leaf is set to "false", then the protocol operation is permitted. 2. If the requesting session is identified as a "recovery session", then the protocol operation is permitted. Bierman & Bjorklund Expires December 16, 2011 [Page 22] Internet-Draft NACM June 2011 3. If the requested operation is the NETCONF operation, then the protocol operation is permitted. 4. Check all the "group" entries for ones that contain a "user- name" entry that equals the user name for the session making the request. Add to these groups the set of groups provided by the transport layer. 5. If no groups are found, continue with step 10. 6. Process all rule-list entries, in order. If a rule-list's "group" leaf-list does not match any of the user's groups, proceed to the next rule-list entry. 7. For each rule-list entry found, process all rules, in order, until a rule that matches the requested operation is found. A rule matches if all of the following criteria are met: * The rule's "module-name" leaf is "*", or equals the name of the YANG module where the protocol operation is defined. * The rule does not have a "rule-type" defined, or the "rule- type" is "protocol-operation" and the "rpc-name" is "*" or equals the name of the requested protocol operation. * The rule's "access-operations" leaf has the "exec" bit set, or has the special value "*". 8. If a matching rule is found, then the "action" leaf is checked. If it is equal to "permit", then the protocol operation is permitted, otherwise it is denied. 9. Otherwise, no matching rule was found in any rule-list entry. 10. If the requested protocol operation is defined in a YANG module advertised in the server capabilities, and the "rpc" statement contains a "nacm:secure" or a "nacm:very-secure" statement, then the protocol operation is denied. 11. If the "exec-default" leaf is set to "permit", then permit the protocol operation, otherwise deny the request. If the session is not authorized to invoke the protocol operation then an is generated with the following information: Bierman & Bjorklund Expires December 16, 2011 [Page 23] Internet-Draft NACM June 2011 error-tag: access-denied error-path: Identifies the requested protocol operation. For example: /nc:rpc/nc:edit-config represents the operation in the NETCONF base namespace. If a datastore is accessed, either directly or as a side effect of the protocol operation, then the server MUST intercept the operation and make sure the session is authorized to perform the requested operation on the specified data, as defined in Section 3.3.5. 3.3.5. Data Node Access Validation If a data node within a datastore is accessed, then the server MUST ensure that the client session is authorized to perform the requested read, create, update, or delete operation on the specified data node. The data node access request is authorized by following these steps: 1. If the "enable-nacm" leaf is set to "false", then the protocol operation is permitted. 2. If the requesting session is identified as a "recovery session", then the protocol operation is permitted. 3. Check all the "group" entries for ones that contain a "user- name" entry that equals the user name for the session making the request. Add to these groups the set of groups provided by the transport layer. 4. If no groups are found, continue with step 9. 5. Process all rule-list entries, in order. If a rule-list's "group" leaf-list does not match any of the user's groups, proceed to the next rule-list entry. 6. For each rule-list entry found, process all rules, in order, until a rule that matches the requested operation is found. A rule matches if all of the following criteria are met: Bierman & Bjorklund Expires December 16, 2011 [Page 24] Internet-Draft NACM June 2011 * The rule's "module-name" leaf is "*", or equals the name of the YANG module where the protocol operation is defined. * The rule does not have a "rule-type" defined, or the "rule- type" is "data-node" and the "path" matches the requested data node. * For a read operation, the rule's "access-operations" leaf has the "read" bit set, or has the special value "*". * For a creation operation, the rule's "access-operations" leaf has the "create" bit set, or has the special value "*". * For a deletion operation, the rule's "access-operations" leaf has the "delete" bit set, or has the special value "*". * For an update operation, the rule's "access-operations" leaf has the "update" bit set, or has the special value "*". 7. If a matching rule is found, then the "action" leaf is checked. If it is equal to "permit", then the data node access is permitted, otherwise it is denied. For a read operation, "denied" means that the requested data is not returned in the reply. 8. Otherwise, no matching rule was found in any rule-list entry. 9. For a read operation, if the requested data node is defined in a YANG module advertised in the server capabilities, and the data definition statement contains a "nacm:very-secure" statement, then the requested data node is not included in the reply. 10. For a write operation, if the requested data node is defined in a YANG module advertised in the server capabilities, and the data definition statement contains a "nacm:secure" or a "nacm: very-secure" statement, then the data node access request is denied. 11. For a read operation, if the "read-default" leaf is set to "permit", then include the requested data node in the reply, otherwise do not include the requested data node in the reply. 12. For a write operation, if the "write-default" leaf is set to "permit", then permit the data node access request, otherwise deny the request. Bierman & Bjorklund Expires December 16, 2011 [Page 25] Internet-Draft NACM June 2011 3.3.6. Outgoing Authorization Configuration of access control rules specifically for descendant nodes of the notification event type element are outside the scope of this document. If the session is authorized to receive the notification event type, then it is also authorized to receive any data it contains. The following figure shows the conceptual message processing model for outgoing messages. NETCONF server +------------+ | XML | | message | | generator | +------------+ ^ | +----------------+ | | | generator | +----------------+ ^ | +=================+ | | | access control | | | +=================+ ^ | +------------------------+ | server instrumentation | +------------------------+ | ^ V | +----------------------+ | configuration | | datastore | +----------------------+ Figure 4 Bierman & Bjorklund Expires December 16, 2011 [Page 26] Internet-Draft NACM June 2011 The generation of a notification for a specific subscription is authorized by following these steps: 1. If the "enable-nacm" leaf is set to "false", then the notification is permitted. 2. If the session is identified as a "recovery session", then the notification is permitted. 3. If the notification is the NETCONF or event type, then the notification is permitted. 4. Check all the "group" entries for ones that contain a "user- name" entry that equals the user name for the session making the request. Add to these groups the set of groups provided by the transport layer. 5. If no groups are found, continue with step 10. 6. Process all rule-list entries, in order. If a rule-list's "group" leaf-list does not match any of the user's groups, proceed to the next rule-list entry. 7. For each rule-list entry found, process all rules, in order, until a rule that matches the requested operation is found. A rule matches if all of the following criteria are met: * The rule's "module-name" leaf is "*", or equals the name of the YANG module where the protocol operation is defined. * The rule does not have a "rule-type" defined, or the "rule- type" is "notification" and the "notification-name" is "*", equals the name of the notification. * The rule's "access-operations" leaf has the "read" bit set, or has the special value "*". 8. If a matching rule is found, then the "action" leaf is checked. If it is equal to "permit", then permit the notification, otherwise drop the notification for the associated subscription. 9. Otherwise, no matching rule was found in any rule-list entry. 10. If the requested notification is defined in a YANG module advertised in the server capabilities, and the "notification" statement contains a "nacm:very-secure" statement, then the notification is dropped for the associated subscription. Bierman & Bjorklund Expires December 16, 2011 [Page 27] Internet-Draft NACM June 2011 11. If the "read-default" leaf is set to "permit", then permit the notification, otherwise drop the notification for the associated subscription. 3.4. Data Model Definitions This section defines the semantics of the conceptual data structures found in the data model in Section 3.4. 3.4.1. Data Organization The top-level element is called , and it is defined in the "ietf-netconf-acm" module's namespace. There are several data structures defined as child nodes of the element: leaf : On/off boolean switch to enable or disable access control enforcement. leaf : Enumeration to permit or deny default read access requests. leaf : Enumeration to permit or deny default write access requests. leaf : Enumeration to permit or deny default protocol operation execution requests. leaf : Read-only counter of the number of times the server has denied an RPC operation request, since the last reboot of the server. leaf : Read-only counter of the number of times the server has denied a data node write request, since the last reboot of the server. leaf : Read-only counter of the number of times the server has denied a notification, since the last reboot of the server. container : Configures the groups used within the access control system. list : A list of user names belonging to the same administrative group. Bierman & Bjorklund Expires December 16, 2011 [Page 28] Internet-Draft NACM June 2011 container : Configures the access control rules used within the server. list : An ordered collection of related access control rules. list : Configures the access control rules for protocol operation invocation, configuration datastore access, and for controlling delivery of events. 3.4.2. YANG Module The following YANG module specifies the normative NETCONF content that MUST by supported by the server. The ietf-netconf-acm YANG module imports typedefs from [RFC6021]. // RFC Ed.: please update the date to the date of publication file="ietf-netconf-acm@2011-06-14.yang" module ietf-netconf-acm { namespace "urn:ietf:params:xml:ns:yang:ietf-netconf-acm"; prefix "nacm"; import ietf-yang-types { prefix yang; } organization "IETF NETCONF (Network Configuration) Working Group"; contact "WG Web: WG List: WG Chair: Mehmet Ersue WG Chair: Bert Wijnen Editor: Andy Bierman Bierman & Bjorklund Expires December 16, 2011 [Page 29] Internet-Draft NACM June 2011 Editor: Martin Bjorklund "; description "NETCONF Server Access Control Model. Copyright (c) 2011 IETF Trust and the persons identified as authors of the code. All rights reserved. Redistribution and use in source and binary forms, with or without modification, is permitted pursuant to, and subject to the license terms contained in, the Simplified BSD License set forth in Section 4.c of the IETF Trust's Legal Provisions Relating to IETF Documents (http://trustee.ietf.org/license-info). This version of this YANG module is part of RFC XXXX; see the RFC itself for full legal notices."; // RFC Ed.: replace XXXX with actual RFC number and // remove this note // RFC Ed.: remove this note // Note: extracted from draft-ietf-netconf-access-control-04.txt // RFC Ed.: please update the date to the date of publication revision "2011-06-14" { description "Initial version"; reference "RFC XXXX: Network Configuration Protocol Access Control Model"; } /* * Extension statements */ extension secure { description "Used to indicate that the data model node represents a sensitive security system parameter. If present, and the NACM module is enabled (i.e., /nacm/enable-nacm object equals 'true'), the NETCONF server will only allow the designated 'recovery session' to have write or execute access to the node. An explicit access control rule is required for all other users. Bierman & Bjorklund Expires December 16, 2011 [Page 30] Internet-Draft NACM June 2011 The 'secure' extension MAY appear within a data definition statement or rpc statement. It is ignored otherwise."; } extension very-secure { description "Used to indicate that the data model node controls a very sensitive security system parameter. If present, and the NACM module is enabled (i.e., /nacm/enable-nacm object equals 'true'), the NETCONF server will only allow the designated 'recovery session' to have read, write, or execute access to the node. An explicit access control rule is required for all other users. The 'very-secure' extension MAY appear within a data definition statement, rpc statement, or notification statement. It is ignored otherwise."; } /* * Derived types */ typedef user-name-type { type string { length "1..max"; } description "General Purpose User Name string."; } typedef matchall-string-type { type string { pattern "\*"; } description "The string containing a single asterisk '*' is used to conceptually represent all possible values for the particular leaf using this data type."; } typedef access-operations-type { type bits { bit create { description "Any operation that creates a new instance of the specified data is a create Bierman & Bjorklund Expires December 16, 2011 [Page 31] Internet-Draft NACM June 2011 operation."; } bit read { description "Any operation or notification that returns data to an application is a read operation."; } bit update { description "Any operation that alters an existing data node is an update operation."; } bit delete { description "Any operation that removes a datastore node instance is a delete operation."; } bit exec { description "Execution access to the specified RPC operation. Any RPC operation invocation is an exec operation."; } } description "NETCONF Access Operation."; } typedef group-name-type { type string { length "1..max"; pattern "[^\*].*"; } description "Name of administrative group that can be assigned to the user, and specified in an access control rule-list."; } typedef action-type { type enumeration { enum permit { description "Requested action is permitted."; } enum deny { description "Requested action is denied."; Bierman & Bjorklund Expires December 16, 2011 [Page 32] Internet-Draft NACM June 2011 } } description "Action taken by the server when a particular rule matches."; } typedef node-instance-identifier { type yang:xpath1.0; description "Path expression used to represent a special data node instance identifier string. A node-instance-identifier value is an unrestricted YANG instance-identifier expression. All the same rules as an instance-identifier apply except predicates for keys are optional. If a key predicate is missing, then the node-instance-identifier represents all possible server instances for that key. This XPath expression is evaluated in the following context: o The set of namespace declarations are those in scope on the leaf element where this type is used. o The set of variable bindings contains one variable, 'USER', which contains the name of user of the current session. o The function library is the core function library, but note that due to the syntax restrictions of an instance-identifier, no functions are allowed. o The context node is the root node in the data tree."; } container nacm { nacm:very-secure; description "Parameters for NETCONF Access Control Model."; leaf enable-nacm { type boolean; default true; description "Enable or disable all NETCONF access control enforcement. If 'true', then enforcement Bierman & Bjorklund Expires December 16, 2011 [Page 33] Internet-Draft NACM June 2011 is enabled. If 'false', then enforcement is disabled."; } leaf read-default { type action-type; default "permit"; description "Controls whether read access is granted if no appropriate rule is found for a particular read request."; } leaf write-default { type action-type; default "deny"; description "Controls whether create, update, or delete access is granted if no appropriate rule is found for a particular write request."; } leaf exec-default { type action-type; default "permit"; description "Controls whether exec access is granted if no appropriate rule is found for a particular RPC operation request."; } leaf denied-rpcs { type yang:zero-based-counter32; config false; mandatory true; description "Number of times an RPC operation request was denied since the server last restarted."; } leaf denied-data-writes { type yang:zero-based-counter32; config false; mandatory true; description "Number of times a request to alter a data node was denied, since the server last restarted."; } Bierman & Bjorklund Expires December 16, 2011 [Page 34] Internet-Draft NACM June 2011 leaf denied-notifications { type yang:zero-based-counter32; config false; mandatory true; description "Number of times a notification was denied since the server last restarted."; } container groups { description "NETCONF Access Control Groups."; list group { key name; description "One NACM Group Entry."; leaf name { type group-name-type; description "Group name associated with this entry."; } leaf-list user-name { type user-name-type; description "Each entry identifies the user name of a member of the group associated with this entry."; } } } list rule-list { key "name"; ordered-by user; description "An ordered collection of access control rules."; leaf name { type string { length "1..256"; } description "Arbitrary name assigned to the rule-list."; } Bierman & Bjorklund Expires December 16, 2011 [Page 35] Internet-Draft NACM June 2011 leaf-list group { type union { type matchall-string-type; type group-name-type; } description "List of administrative groups that will be assigned the associated access rights defined by the 'rule' list. The string '*' indicates that all groups apply to the entry."; } list rule { key "name"; ordered-by user; description "One access control rule. Rules are processed in user-defined order until a match is found. A rule matches if 'module-name', 'rule-type', and 'access-operations' matches the request. If a rule matches, the 'action' leaf determines if access is granted or not."; leaf name { type string { length "1..256"; } description "Arbitrary name assigned to the rule."; } leaf module-name { type union { type matchall-string-type; type string; } default "*"; description "Name of the module associated with this rule. This leaf matches if it has the value '*', or if the object being accessed is defined in the module with the specified module name."; } choice rule-type { Bierman & Bjorklund Expires December 16, 2011 [Page 36] Internet-Draft NACM June 2011 description "This choice matches if all leafs present in the rule matches the request. If no leafs are present, the choice matches all requests."; case protocol-operation { leaf rpc-name { type union { type matchall-string-type; type string; } description "This leaf matches if it has the value '*', or if its value equals the requested RPC operation name."; } } case notification { leaf notification-name { type union { type matchall-string-type; type string; } description "This leaf matches if it has the value '*', or if its value equals the requested notification name."; } } case data-node { leaf path { type node-instance-identifier; mandatory true; description "Data Node Instance Identifier associated with the data node controlled by this rule. Configuration data or state data instance identifiers start with a top-level data node. A complete instance identifier is required for this type of path value. The special value '/' refers to all possible data store contents."; } } } leaf access-operations { type union { type matchall-string-type; Bierman & Bjorklund Expires December 16, 2011 [Page 37] Internet-Draft NACM June 2011 type access-operations-type; } default "*"; description "Access operations associated with this rule. This leaf matches if it has the value '*', or if the bit corresponding to the requested operation is set."; } leaf action { type action-type; mandatory true; description "The access control action associated with the rule. If a rule is determined to match a particular request, then this object is used to determine whether to permit or deny the request."; } leaf comment { type string; description "A textual description of the access rule."; } } } } } Figure 5 3.5. IANA Considerations There are two actions that are requested of IANA: This document registers one URI in "The IETF XML Registry". Following the format in [RFC3688], the following has been registered. URI: urn:ietf:params:xml:ns:yang:ietf-netconf-acm Registrant Contact: The IESG. XML: N/A, the requested URI is an XML namespace. This document registers one module in the "YANG Module Names" Bierman & Bjorklund Expires December 16, 2011 [Page 38] Internet-Draft NACM June 2011 registry. Following the format in [RFC6020], the following has been registered. name: ietf-netconf-acm namespace: urn:ietf:params:xml:ns:yang:ietf-netconf-acm prefix: nacm reference: RFC XXXX // RFC Ed.: Replace XXX with actual RFC number // and remove this note 3.6. Security Considerations This entire document discusses access control requirements and mechanisms for restricting NETCONF protocol behavior within a given session. Configuration of the access control system is highly sensitive to system security. A server may choose not to allow any user configuration to some portions of it, such as the global security level, or the groups which allowed access to system resources. This document incorporates the optional use of a "recovery session" mechanism, which can be used to bypass access control enforcement in emergencies, such as NACM configuration errors which disable all access to the server. The configuration and identification of such a recovery session mechanism are outside the scope of this document. There is a risk that invocation of non-standard protocol operations will have undocumented side effects. An administrator needs to construct access control rules such that the configuration datastore is protected from such side effects. Also, such protocol operations SHOULD never be invoked by a session during a "recovery session". There is a risk that non-standard protocol operations, or even the standard operation, may return data which "aliases" or "copies" sensitive data from a different data object. In this case, the namespace and/or the element name will not match the values for the sensitive data, which is then fully or partially copied into a different namespace and/or element. An administrator needs to avoid using data models which use this practice. An administrator needs to restrict write access to all configurable objects within this data model. If write access is allowed for configuration of access control rules, then care needs to be taken not to disrupt the access control enforcement. Bierman & Bjorklund Expires December 16, 2011 [Page 39] Internet-Draft NACM June 2011 An administrator needs to restrict read access to the following objects within this data model, which reveal access control configuration which could be considered sensitive. o enable-nacm o read-default o write-default o exec-default o groups o rules Bierman & Bjorklund Expires December 16, 2011 [Page 40] Internet-Draft NACM June 2011 4. References 4.1. Normative References [RFC2119] Bradner, S., "Key words for use in RFCs to Indicate Requirement Levels", BCP 14, RFC 2119, March 1997. [RFC3688] Mealling, M., "The IETF XML Registry", BCP 81, RFC 3688, January 2004. [RFC5277] Chisholm, S. and H. Trevino, "NETCONF Event Notifications", RFC 5277, July 2008. [RFC6020] Bjorklund, M., "YANG - A Data Modeling Language for the Network Configuration Protocol (NETCONF)", RFC 6020, October 2010. [RFC6021] Schoenwaelder, J., "Common YANG Data Types", RFC 6021, October 2010. [I-D.ietf-netconf-4741bis] Enns, R., Bjorklund, M., Schoenwaelder, J., and A. Bierman, "Network Configuration Protocol (NETCONF)", draft-ietf-netconf-4741bis-10 (work in progress), March 2011. [I-D.ietf-netconf-rfc4742bis] Wasserman, M. and T. Goddard, "Using the NETCONF Configuration Protocol over Secure Shell (SSH)", draft-ietf-netconf-rfc4742bis-08 (work in progress), March 2011. 4.2. Informative References [RFC2865] Rigney, C., Willens, S., Rubens, A., and W. Simpson, "Remote Authentication Dial In User Service (RADIUS)", RFC 2865, June 2000. [RFC5607] Nelson, D. and G. Weber, "Remote Authentication Dial-In User Service (RADIUS) Authorization for Network Access Server (NAS) Management", RFC 5607, July 2009. Bierman & Bjorklund Expires December 16, 2011 [Page 41] Internet-Draft NACM June 2011 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. Example There needs to be at least one 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. admin admin andy monitor wilma bam-bam guest guest guest@example.com This example shows 3 groups: 1. The "admin" group contains 2 users named "admin" and "andy". 2. The "monitor" group contains 2 users named "wilma" and "bam-bam". 3. The "guest" group contains 2 users named "guest" and "guest@example.com". Bierman & Bjorklund Expires December 16, 2011 [Page 42] Internet-Draft NACM June 2011 A.2. Module Rule Example Module rules are used to control access to all the content defined in a specific module. A module rule has the leaf set, but no case in the "rule-type" choice. guest guest mod-1 ietf-netconf-monitoring * deny Do not allow guests any access to the netconf monitoring information. monitor example monitor mod-2 ietf-netconf-monitoring read permit Allow read access to the netconf monitoring information. mod-3 * exec permit Allow invocation of the supported server operations. Bierman & Bjorklund Expires December 16, 2011 [Page 43] Internet-Draft NACM June 2011 admin example admin mod-4 * * permit Allow the admin group complete access to all operations and data. This example shows 4 module rules: mod-1: This rule prevents the guest group from reading any monitoring information in the ietf-netconf-monitoring YANG module. mod-2: This rule allows the monitor group to read the ietf-netconf- monitoring YANG module. mod-3: This rule allows the monitor group to invoke any protocol operation supported by the server. mod-4: This rule allows the admin group complete access to all content in the server. No subsequent rule will match for the admin group, because of this module rule. A.3. RPC Rule Example RPC rules are used to control access to a specific protocol operation. Bierman & Bjorklund Expires December 16, 2011 [Page 44] Internet-Draft NACM June 2011 guest monitor guest rpc-1 ietf-netconf kill-session exec deny Do not allow the monitor or guest group to kill another session. rpc-2 ietf-netconf delete-config exec deny Do not allow monitor or guest group to delete any configurations. monitor monitor rpc-3 ietf-netconf edit-config exec permit Allow the monitor group to edit the configuration. Bierman & Bjorklund Expires December 16, 2011 [Page 45] Internet-Draft NACM June 2011 This example shows 3 protocol operation rules: rpc-1: This rule prevents the monitor or guest groups from invoking the NETCONF protocol operation. rpc-2: This rule prevents the monitor or guest groups from invoking the NETCONF protocol operation. rpc-3: This rule allows the monitor group to invoke the NETCONF protocol operation. This rule will have no real effect unless the "exec-default" leaf is set to "deny". A.4. Data Rule Example Data rules are used to control access to specific (config and non- config) data nodes within the NETCONF content provided by the server. guest rules guest data-1 /n:nacm * deny Deny the guest group any access to the /nacm data. monitor rules monitor data-acme-config /acme:acme-netconf/acme:config-parameters read create update delete Bierman & Bjorklund Expires December 16, 2011 [Page 46] Internet-Draft NACM June 2011 permit Allow the monitor group complete access to the acme netconf configuration parameters. Showing long form of 'access-operations' instead of shorthand. dummy-itf guest monitor dummy-itf /acme:interfaces/acme:interface[acme:name='dummy'] read update permit Allow the monitor and guest groups read and update access to the dummy interface. admin rules admin-itf /acme:interfaces/acme:interface * permit Allow admin full access to all acme interfaces. This example shows 4 data rules: Bierman & Bjorklund Expires December 16, 2011 [Page 47] Internet-Draft NACM June 2011 data-1: This rule denies the guest group any access to the subtree. Note that the default namespace is only applicable because this subtree is defined in the same namespace as the element. data-acme-config: This rule gives the monitor group read-write access to the acme . dummy-itf: This rule gives the monitor and guest groups read-update access to the acme . 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 . 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. sys monitor guest notif-1 acme-system sys-config-change read deny Do not allow the guest or monitor groups to receive config change events. This example shows 1 notification rule: Bierman & Bjorklund Expires December 16, 2011 [Page 48] Internet-Draft NACM June 2011 notif-1: This rule prevents the monitor or guest groups from receiving the acme event type. Bierman & Bjorklund Expires December 16, 2011 [Page 49] Internet-Draft NACM June 2011 Appendix B. Change Log -- RFC Ed.: remove this section before publication. B.1. 03-04 Introduced rule-lists to group related rules together. Moved "module-rule", "rpc-rule", "notification-rule", and "data-rule" into one common "rule", with a choice to select between the four variants. Changed "superuser" to "recovery session", and adjusted text throughout document for this change. Clarified behavior of global default NACM parameters, enable-nacm, read-default, write-default, exec-default. Clarified when access control is applied during system initialization. B.2. 02-03 Fixed improper usage of RFC 2119 keywords. Changed term usage of "database" to "datastore". Clarified that "secure" and "very-secure" extensions only apply if the /nacm/enable-nacm object is "true". B.3. 01-02 Removed authentication text and objects. Changed module name from ietf-nacm to ietf-netconf-acm. Updated NETCONF and YANG terminology. Removed open issues section. Changed some must to MUST in requirements section. B.4. 00-01 Updated YANG anf YANG Types references. Updated module namespace URI to standard format. Bierman & Bjorklund Expires December 16, 2011 [Page 50] Internet-Draft NACM June 2011 Updated module header meta-data to standard format. Filled in IANA section. B.5. 00 Initial version cloned from draft-bierman-netconf-access-control-02.txt. Bierman & Bjorklund Expires December 16, 2011 [Page 51] Internet-Draft NACM June 2011 Authors' Addresses Andy Bierman Brocade Email: andy.bierman@brocade.com Martin Bjorklund Tail-f Systems Email: mbj@tail-f.com Bierman & Bjorklund Expires December 16, 2011 [Page 52]