Network Working Group B. Wijnen
Request for Comments: 3415 Lucent Technologies
STD: 62 R. Presuhn
Obsoletes: 2575 BMC Software, Inc.
Category: Standards Track K. McCloghrie
 Cisco Systems, Inc.
 December 2002
 View-based Access Control Model (VACM) for the
 Simple Network Management Protocol (SNMP)
Status of this Memo
 This document specifies an Internet standards track protocol for the
 Internet community, and requests discussion and suggestions for
 improvements. Please refer to the current edition of the "Internet
 Official Protocol Standards" (STD 1) for the standardization state
 and status of this protocol. Distribution of this memo is unlimited.
Copyright Notice
 Copyright (C) The Internet Society (2002). All Rights Reserved.
Abstract
 This document describes the View-based Access Control Model (VACM)
 for use in the Simple Network Management Protocol (SNMP)
 architecture. It defines the Elements of Procedure for controlling
 access to management information. This document also includes a
 Management Information Base (MIB) for remotely managing the
 configuration parameters for the View-based Access Control Model.
 This document obsoletes RFC 2575.
Table of Contents
 1. Introduction ................................................. 2
 1.2. Access Control ............................................. 3
 1.3. Local Configuration Datastore .............................. 3
 2. Elements of the Model ........................................ 4
 2.1. Groups ..................................................... 4
 2.2. securityLevel .............................................. 4
 2.3. Contexts ................................................... 4
 2.4. MIB Views and View Families ................................ 5
 2.4.1. View Subtree ............................................. 5
 2.4.2. ViewTreeFamily ........................................... 6
 2.5. Access Policy .............................................. 6
 3. Elements of Procedure ........................................ 7
 3.1. Overview of isAccessAllowed Process ....................... 8
 3.2. Processing the isAccessAllowed Service Request ............. 9
 4. Definitions .................................................. 11
 5. Intellectual Property ........................................ 28
 6. Acknowledgements ............................................. 28
 7. Security Considerations ...................................... 30
 7.1. Recommended Practices ...................................... 30
 7.2. Defining Groups ............................................ 30
 7.3. Conformance ................................................ 31
 7.4. Access to the SNMP-VIEW-BASED-ACM-MIB ...................... 31
 8. References ................................................... 31
 A. Installation ................................................. 33
 B. Change Log ................................................... 36
 Editors' Addresses ............................................... 38
 Full Copyright Statement ......................................... 39
1. Introduction
 The Architecture for describing Internet Management Frameworks
 [RFC3411] describes that an SNMP engine is composed of:
 1) a Dispatcher
 2) a Message Processing Subsystem,
 3) a Security Subsystem, and
 4) an Access Control Subsystem.
 Applications make use of the services of these subsystems.
 It is important to understand the SNMP architecture and its
 terminology to understand where the View-based Access Control Model
 described in this document fits into the architecture and interacts
 with other subsystems within the architecture. The reader is
 expected to have read and understood the description and terminology
 of the SNMP architecture, as defined in [RFC3411].
 The Access Control Subsystem of an SNMP engine has the responsibility
 for checking whether a specific type of access (read, write, notify)
 to a particular object (instance) is allowed.
 It is the purpose of this document to define a specific model of the
 Access Control Subsystem, designated the View-based Access Control
 Model. Note that this is not necessarily the only Access Control
 Model.
 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 BCP 14, RFC 2119.
1.2. Access Control
 Access Control occurs (either implicitly or explicitly) in an SNMP
 entity when processing SNMP retrieval or modification request
 messages from an SNMP entity. For example a Command Responder
 application applies Access Control when processing requests that it
 received from a Command Generator application. These requests
 contain Read Class and Write Class PDUs as defined in [RFC3411].
 Access Control also occurs in an SNMP entity when an SNMP
 notification message is generated (by a Notification Originator
 application). These notification messages contain Notification Class
 PDUs as defined in [RFC3411].
 The View-based Access Control Model defines a set of services that an
 application (such as a Command Responder or a Notification Originator
 application) can use for checking access rights. It is the
 responsibility of the application to make the proper service calls
 for access checking.
1.3. Local Configuration Datastore
 To implement the model described in this document, an SNMP entity
 needs to retain information about access rights and policies. This
 information is part of the SNMP engine's Local Configuration
 Datastore (LCD). See [RFC3411] for the definition of LCD.
 In order to allow an SNMP entity's LCD to be remotely configured,
 portions of the LCD need to be accessible as managed objects. A MIB
 module, the View-based Access Control Model Configuration MIB, which
 defines these managed object types is included in this document.
2. Elements of the Model
 This section contains definitions to realize the access control
 service provided by the View-based Access Control Model.
2.1. Groups
 A group is a set of zero or more <securityModel, securityName> tuples
 on whose behalf SNMP management objects can be accessed. A group
 defines the access rights afforded to all securityNames which belong
 to that group. The combination of a securityModel and a securityName
 maps to at most one group. A group is identified by a groupName.
 The Access Control module assumes that the securityName has already
 been authenticated as needed and provides no further authentication
 of its own.
 The View-based Access Control Model uses the securityModel and the
 securityName as inputs to the Access Control module when called to
 check for access rights. It determines the groupName as a function
 of securityModel and securityName.
2.2. securityLevel
 Different access rights for members of a group can be defined for
 different levels of security, i.e., noAuthNoPriv, authNoPriv, and
 authPriv. The securityLevel identifies the level of security that
 will be assumed when checking for access rights. See the SNMP
 Architecture document [RFC3411] for a definition of securityLevel.
 The View-based Access Control Model requires that the securityLevel
 is passed as input to the Access Control module when called to check
 for access rights.
2.3. Contexts
 An SNMP context is a collection of management information accessible
 by an SNMP entity. An item of management information may exist in
 more than one context. An SNMP entity potentially has access to many
 contexts. Details about the naming of management information can be
 found in the SNMP Architecture document [RFC3411].
 The View-based Access Control Model defines a vacmContextTable that
 lists the locally available contexts by contextName.
2.4. MIB Views and View Families
 For security reasons, it is often valuable to be able to restrict the
 access rights of some groups to only a subset of the management
 information in the management domain. To provide this capability,
 access to a context is via a "MIB view" which details a specific set
 of managed object types (and optionally, the specific instances of
 object types) within that context. For example, for a given context,
 there will typically always be one MIB view which provides access to
 all management information in that context, and often there will be
 other MIB views each of which contains some subset of the
 information. So, the access allowed for a group can be restricted in
 the desired manner by specifying its rights in terms of the
 particular (subset) MIB view it can access within each appropriate
 context.
 Since managed object types (and their instances) are identified via
 the tree-like naming structure of ISO's OBJECT IDENTIFIERs [ISO-
 ASN.1, RFC2578], it is convenient to define a MIB view as the
 combination of a set of "view subtrees", where each view subtree is a
 subtree within the managed object naming tree. Thus, a simple MIB
 view (e.g., all managed objects within the Internet Network
 Management Framework) can be defined as a single view subtree, while
 more complicated MIB views (e.g., all information relevant to a
 particular network interface) can be represented by the union of
 multiple view subtrees.
 While any set of managed objects can be described by the union of
 some number of view subtrees, situations can arise that would require
 a very large number of view subtrees. This could happen, for
 example, when specifying all columns in one conceptual row of a MIB
 table because they would appear in separate subtrees, one per column,
 each with a very similar format. Because the formats are similar,
 the required set of subtrees can easily be aggregated into one
 structure. This structure is named a family of view subtrees after
 the set of subtrees that it conceptually represents. A family of
 view subtrees can either be included or excluded from a MIB view.
2.4.1. View Subtree
 A view subtree is the set of all MIB object instances which have a
 common ASN.1 OBJECT IDENTIFIER prefix to their names. A view subtree
 is identified by the OBJECT IDENTIFIER value which is the longest
 OBJECT IDENTIFIER prefix common to all (potential) MIB object
 instances in that subtree.
2.4.2. ViewTreeFamily
 A family of view subtrees is a pairing of an OBJECT IDENTIFIER value
 (called the family name) together with a bit string value (called the
 family mask). The family mask indicates which sub-identifiers of the
 associated family name are significant to the family's definition.
 For each possible managed object instance, that instance belongs to a
 particular ViewTreeFamily if both of the following conditions are
 true:
 - the OBJECT IDENTIFIER name of the managed object instance contains
 at least as many sub-identifiers as does the family name, and
 - each sub-identifier in the OBJECT IDENTIFIER name of the managed
 object instance matches the corresponding sub-identifier of the
 family name whenever the corresponding bit of the associated
 family mask is non-zero.
 When the configured value of the family mask is all ones, the view
 subtree family is identical to the single view subtree identified by
 the family name.
 When the configured value of the family mask is shorter than required
 to perform the above test, its value is implicitly extended with
 ones. Consequently, a view subtree family having a family mask of
 zero length always corresponds to a single view subtree.
2.5. Access Policy
 The View-based Access Control Model determines the access rights of a
 group, representing zero or more securityNames which have the same
 access rights. For a particular context, identified by contextName,
 to which a group, identified by groupName, has access using a
 particular securityModel and securityLevel, that group's access
 rights are given by a read-view, a write-view and a notify-view.
 The read-view represents the set of object instances authorized for
 the group when reading objects. Reading objects occurs when
 processing a retrieval operation (when handling Read Class PDUs).
 The write-view represents the set of object instances authorized for
 the group when writing objects. Writing objects occurs when
 processing a write operation (when handling Write Class PDUs).
 The notify-view represents the set of object instances authorized for
 the group when sending objects in a notification, such as when
 sending a notification (when sending Notification Class PDUs).
3. Elements of Procedure
 This section describes the procedures followed by an Access Control
 module that implements the View-based Access Control Model when
 checking access rights as requested by an application (for example a
 Command Responder or a Notification Originator application). The
 abstract service primitive is:
 statusInformation = -- success or errorIndication
 isAccessAllowed(
 securityModel -- Security Model in use
 securityName -- principal who wants access
 securityLevel -- Level of Security
 viewType -- read, write, or notify view
 contextName -- context containing variableName
 variableName -- OID for the managed object
 )
 The abstract data elements are:
 statusInformation - one of the following:
 accessAllowed - a MIB view was found and access is granted.
 notInView - a MIB view was found but access is denied.
 The variableName is not in the configured
 MIB view for the specified viewType (e.g., in
 the relevant entry in the vacmAccessTable).
 noSuchView - no MIB view found because no view has been
 configured for specified viewType (e.g., in
 the relevant entry in the vacmAccessTable).
 noSuchContext - no MIB view found because of no entry in the
 vacmContextTable for specified contextName.
 noGroupName - no MIB view found because no entry has been
 configured in the vacmSecurityToGroupTable
 for the specified combination of
 securityModel and securityName.
 noAccessEntry - no MIB view found because no entry has been
 configured in the vacmAccessTable for the
 specified combination of contextName,
 groupName (from vacmSecurityToGroupTable),
 securityModel and securityLevel.
 otherError - failure, an undefined error occurred.
 securityModel - Security Model under which access is requested.
 securityName - the principal on whose behalf access is requested.
 securityLevel - Level of Security under which access is requested.
 viewType - view to be checked (read, write or notify).
 contextName - context in which access is requested.
 variableName - object instance to which access is requested.
3.1. Overview of isAccessAllowed Process
 The following picture shows how the decision for access control is
 made by the View-based Access Control Model.
 +--------------------------------------------------------------------+
 | |
 | +-> securityModel -+ |
 | | (a) | |
 | who -+ +-> groupName ----+ |
 | (1) | | (x) | |
 | +-> securityName --+ | |
 | (b) | |
 | | |
 | where -> contextName ---------------------+ |
 | (2) (e) | |
 | | |
 | | |
 | +-> securityModel -------------------+ |
 | | (a) | |
 | how -+ +-> viewName -+ |
 | (3) | | (y) | |
 | +-> securityLevel -------------------+ | |
 | (c) | +-> yes/no |
 | | | decision |
 | why ---> viewType (read/write/notify) ----+ | (z) |
 | (4) (d) | |
 | | |
 | what --> object-type ------+ | |
 | (5) (m) | | |
 | +-> variableName (OID) ------+ |
 | | (f) |
 | which -> object-instance --+ |
 | (6) (n) |
 | |
 +--------------------------------------------------------------------+
 How the decision for isAccessAllowed is made.
 1) Inputs to the isAccessAllowed service are:
 (a) securityModel -- Security Model in use
 (b) securityName -- principal who wants to access
 (c) securityLevel -- Level of Security
 (d) viewType -- read, write, or notify view
 (e) contextName -- context containing variableName
 (f) variableName -- OID for the managed object
 -- this is made up of:
 - object-type (m)
 - object-instance (n)
 2) The partial "who" (1), represented by the securityModel (a) and
 the securityName (b), are used as the indices (a,b) into the
 vacmSecurityToGroupTable to find a single entry that produces a
 group, represented by groupName (x).
 3) The "where" (2), represented by the contextName (e), the "who",
 represented by the groupName (x) from the previous step, and the
 "how" (3), represented by securityModel (a) and securityLevel (c),
 are used as indices (e,x,a,c) into the vacmAccessTable to find a
 single entry that contains three MIB views.
 4) The "why" (4), represented by the viewType (d), is used to select
 the proper MIB view, represented by a viewName (y), from the
 vacmAccessEntry selected in the previous step. This viewName (y)
 is an index into the vacmViewTreeFamilyTable and selects the set
 of entries that define the variableNames which are included in or
 excluded from the MIB view identified by the viewName (y).
 5) The "what" (5) type of management data and "which" (6) particular
 instance, represented by the variableName (f), is then checked to
 be in the MIB view or not, e.g., the yes/no decision (z).
3.2. Processing the isAccessAllowed Service Request
 This section describes the procedure followed by an Access Control
 module that implements the View-based Access Control Model whenever
 it receives an isAccessAllowed request.
 1) The vacmContextTable is consulted for information about the SNMP
 context identified by the contextName. If information about this
 SNMP context is absent from the table, then an errorIndication
 (noSuchContext) is returned to the calling module.
 2) The vacmSecurityToGroupTable is consulted for mapping the
 securityModel and securityName to a groupName. If the information
 about this combination is absent from the table, then an
 errorIndication (noGroupName) is returned to the calling module.
 3) The vacmAccessTable is consulted for information about the
 groupName, contextName, securityModel and securityLevel. If
 information about this combination is absent from the table, then
 an errorIndication (noAccessEntry) is returned to the calling
 module.
 4) a) If the viewType is "read", then the read view is used for
 checking access rights.
 b) If the viewType is "write", then the write view is used for
 checking access rights.
 c) If the viewType is "notify", then the notify view is used for
 checking access rights.
 If the view to be used is the empty view (zero length viewName)
 then an errorIndication (noSuchView) is returned to the calling
 module.
 5) a) If there is no view configured for the specified viewType, then
 an errorIndication (noSuchView) is returned to the calling
 module.
 b) If the specified variableName (object instance) is not in the
 MIB view (see DESCRIPTION clause for vacmViewTreeFamilyTable in
 section 4), then an errorIndication (notInView) is returned to
 the calling module.
 Otherwise,
 c) The specified variableName is in the MIB view. A
 statusInformation of success (accessAllowed) is returned to the
 calling module.
4. Definitions
SNMP-VIEW-BASED-ACM-MIB DEFINITIONS ::= BEGIN
IMPORTS
 MODULE-COMPLIANCE, OBJECT-GROUP FROM SNMPv2-CONF
 MODULE-IDENTITY, OBJECT-TYPE,
 snmpModules FROM SNMPv2-SMI
 TestAndIncr,
 RowStatus, StorageType FROM SNMPv2-TC
 SnmpAdminString,
 SnmpSecurityLevel,
 SnmpSecurityModel FROM SNMP-FRAMEWORK-MIB;
snmpVacmMIB MODULE-IDENTITY
 LAST-UPDATED "200210160000Z" -- 16 Oct 2002, midnight
 ORGANIZATION "SNMPv3 Working Group"
 CONTACT-INFO "WG-email: snmpv3@lists.tislabs.com
 Subscribe: majordomo@lists.tislabs.com
 In message body: subscribe snmpv3
 Co-Chair: Russ Mundy
 Network Associates Laboratories
 postal: 15204 Omega Drive, Suite 300
 Rockville, MD 20850-4601
 USA
 email: mundy@tislabs.com
 phone: +1 301-947-7107
 Co-Chair: David Harrington
 Enterasys Networks
 Postal: 35 Industrial Way
 P. O. Box 5004
 Rochester, New Hampshire 03866-5005
 USA
 EMail: dbh@enterasys.com
 Phone: +1 603-337-2614
 Co-editor: Bert Wijnen
 Lucent Technologies
 postal: Schagen 33
 3461 GL Linschoten
 Netherlands
 email: bwijnen@lucent.com
 phone: +31-348-480-685
 Co-editor: Randy Presuhn
 BMC Software, Inc.
 postal: 2141 North First Street
 San Jose, CA 95131
 USA
 email: randy_presuhn@bmc.com
 phone: +1 408-546-1006
 Co-editor: Keith McCloghrie
 Cisco Systems, Inc.
 postal: 170 West Tasman Drive
 San Jose, CA 95134-1706
 USA
 email: kzm@cisco.com
 phone: +1-408-526-5260
 "
 DESCRIPTION "The management information definitions for the
 View-based Access Control Model for SNMP.
 Copyright (C) The Internet Society (2002). This
 version of this MIB module is part of RFC 3415;
 see the RFC itself for full legal notices.
 "
-- Revision history
 REVISION "200210160000Z" -- 16 Oct 2002, midnight
 DESCRIPTION "Clarifications, published as RFC3415"
 REVISION "199901200000Z" -- 20 Jan 1999, midnight
 DESCRIPTION "Clarifications, published as RFC2575"
 REVISION "199711200000Z" -- 20 Nov 1997, midnight
 DESCRIPTION "Initial version, published as RFC2275"
 ::= { snmpModules 16 }
-- Administrative assignments ****************************************
vacmMIBObjects OBJECT IDENTIFIER ::= { snmpVacmMIB 1 }
vacmMIBConformance OBJECT IDENTIFIER ::= { snmpVacmMIB 2 }
-- Information about Local Contexts **********************************
vacmContextTable OBJECT-TYPE
 SYNTAX SEQUENCE OF VacmContextEntry
 MAX-ACCESS not-accessible
 STATUS current
 DESCRIPTION "The table of locally available contexts.
 This table provides information to SNMP Command
 Generator applications so that they can properly
 configure the vacmAccessTable to control access to
 all contexts at the SNMP entity.
 This table may change dynamically if the SNMP entity
 allows that contexts are added/deleted dynamically
 (for instance when its configuration changes). Such
 changes would happen only if the management
 instrumentation at that SNMP entity recognizes more
 (or fewer) contexts.
 The presence of entries in this table and of entries
 in the vacmAccessTable are independent. That is, a
 context identified by an entry in this table is not
 necessarily referenced by any entries in the
 vacmAccessTable; and the context(s) referenced by an
 entry in the vacmAccessTable does not necessarily
 currently exist and thus need not be identified by an
 entry in this table.
 This table must be made accessible via the default
 context so that Command Responder applications have
 a standard way of retrieving the information.
 This table is read-only. It cannot be configured via
 SNMP.
 "
 ::= { vacmMIBObjects 1 }
vacmContextEntry OBJECT-TYPE
 SYNTAX VacmContextEntry
 MAX-ACCESS not-accessible
 STATUS current
 DESCRIPTION "Information about a particular context."
 INDEX {
 vacmContextName
 }
 ::= { vacmContextTable 1 }
VacmContextEntry ::= SEQUENCE
 {
 vacmContextName SnmpAdminString
 }
vacmContextName OBJECT-TYPE
 SYNTAX SnmpAdminString (SIZE(0..32))
 MAX-ACCESS read-only
 STATUS current
 DESCRIPTION "A human readable name identifying a particular
 context at a particular SNMP entity.
 The empty contextName (zero length) represents the
 default context.
 "
 ::= { vacmContextEntry 1 }
-- Information about Groups ******************************************
vacmSecurityToGroupTable OBJECT-TYPE
 SYNTAX SEQUENCE OF VacmSecurityToGroupEntry
 MAX-ACCESS not-accessible
 STATUS current
 DESCRIPTION "This table maps a combination of securityModel and
 securityName into a groupName which is used to define
 an access control policy for a group of principals.
 "
 ::= { vacmMIBObjects 2 }
vacmSecurityToGroupEntry OBJECT-TYPE
 SYNTAX VacmSecurityToGroupEntry
 MAX-ACCESS not-accessible
 STATUS current
 DESCRIPTION "An entry in this table maps the combination of a
 securityModel and securityName into a groupName.
 "
 INDEX {
 vacmSecurityModel,
 vacmSecurityName
 }
 ::= { vacmSecurityToGroupTable 1 }
VacmSecurityToGroupEntry ::= SEQUENCE
 {
 vacmSecurityModel SnmpSecurityModel,
 vacmSecurityName SnmpAdminString,
 vacmGroupName SnmpAdminString,
 vacmSecurityToGroupStorageType StorageType,
 vacmSecurityToGroupStatus RowStatus
 }
vacmSecurityModel OBJECT-TYPE
 SYNTAX SnmpSecurityModel(1..2147483647)
 MAX-ACCESS not-accessible
 STATUS current
 DESCRIPTION "The Security Model, by which the vacmSecurityName
 referenced by this entry is provided.
 Note, this object may not take the 'any' (0) value.
 "
 ::= { vacmSecurityToGroupEntry 1 }
vacmSecurityName OBJECT-TYPE
 SYNTAX SnmpAdminString (SIZE(1..32))
 MAX-ACCESS not-accessible
 STATUS current
 DESCRIPTION "The securityName for the principal, represented in a
 Security Model independent format, which is mapped by
 this entry to a groupName.
 "
 ::= { vacmSecurityToGroupEntry 2 }
vacmGroupName OBJECT-TYPE
 SYNTAX SnmpAdminString (SIZE(1..32))
 MAX-ACCESS read-create
 STATUS current
 DESCRIPTION "The name of the group to which this entry (e.g., the
 combination of securityModel and securityName)
 belongs.
 This groupName is used as index into the
 vacmAccessTable to select an access control policy.
 However, a value in this table does not imply that an
 instance with the value exists in table vacmAccesTable.
 "
 ::= { vacmSecurityToGroupEntry 3 }
vacmSecurityToGroupStorageType OBJECT-TYPE
 SYNTAX StorageType
 MAX-ACCESS read-create
 STATUS current
 DESCRIPTION "The storage type for this conceptual row.
 Conceptual rows having the value 'permanent' need not
 allow write-access to any columnar objects in the row.
 "
 DEFVAL { nonVolatile }
 ::= { vacmSecurityToGroupEntry 4 }
vacmSecurityToGroupStatus OBJECT-TYPE
 SYNTAX RowStatus
 MAX-ACCESS read-create
 STATUS current
 DESCRIPTION "The status of this conceptual row.
 Until instances of all corresponding columns are
 appropriately configured, the value of the
 corresponding instance of the vacmSecurityToGroupStatus
 column is 'notReady'.
 In particular, a newly created row cannot be made
 active until a value has been set for vacmGroupName.
 The RowStatus TC [RFC2579] requires that this
 DESCRIPTION clause states under which circumstances
 other objects in this row can be modified:
 The value of this object has no effect on whether
 other objects in this conceptual row can be modified.
 "
 ::= { vacmSecurityToGroupEntry 5 }
-- Information about Access Rights ***********************************
vacmAccessTable OBJECT-TYPE
 SYNTAX SEQUENCE OF VacmAccessEntry
 MAX-ACCESS not-accessible
 STATUS current
 DESCRIPTION "The table of access rights for groups.
 Each entry is indexed by a groupName, a contextPrefix,
 a securityModel and a securityLevel. To determine
 whether access is allowed, one entry from this table
 needs to be selected and the proper viewName from that
 entry must be used for access control checking.
 To select the proper entry, follow these steps:
 1) the set of possible matches is formed by the
 intersection of the following sets of entries:
 the set of entries with identical vacmGroupName
 the union of these two sets:
 - the set with identical vacmAccessContextPrefix
 - the set of entries with vacmAccessContextMatch
 value of 'prefix' and matching
 vacmAccessContextPrefix
 intersected with the union of these two sets:
 - the set of entries with identical
 vacmSecurityModel
 - the set of entries with vacmSecurityModel
 value of 'any'
 intersected with the set of entries with
 vacmAccessSecurityLevel value less than or equal
 to the requested securityLevel
 2) if this set has only one member, we're done
 otherwise, it comes down to deciding how to weight
 the preferences between ContextPrefixes,
 SecurityModels, and SecurityLevels as follows:
 a) if the subset of entries with securityModel
 matching the securityModel in the message is
 not empty, then discard the rest.
 b) if the subset of entries with
 vacmAccessContextPrefix matching the contextName
 in the message is not empty,
 then discard the rest
 c) discard all entries with ContextPrefixes shorter
 than the longest one remaining in the set
 d) select the entry with the highest securityLevel
 Please note that for securityLevel noAuthNoPriv, all
 groups are really equivalent since the assumption that
 the securityName has been authenticated does not hold.
 "
 ::= { vacmMIBObjects 4 }
vacmAccessEntry OBJECT-TYPE
 SYNTAX VacmAccessEntry
 MAX-ACCESS not-accessible
 STATUS current
 DESCRIPTION "An access right configured in the Local Configuration
 Datastore (LCD) authorizing access to an SNMP context.
 Entries in this table can use an instance value for
 object vacmGroupName even if no entry in table
 vacmAccessSecurityToGroupTable has a corresponding
 value for object vacmGroupName.
 "
 INDEX { vacmGroupName,
 vacmAccessContextPrefix,
 vacmAccessSecurityModel,
 vacmAccessSecurityLevel
 }
 ::= { vacmAccessTable 1 }
VacmAccessEntry ::= SEQUENCE
 {
 vacmAccessContextPrefix SnmpAdminString,
 vacmAccessSecurityModel SnmpSecurityModel,
 vacmAccessSecurityLevel SnmpSecurityLevel,
 vacmAccessContextMatch INTEGER,
 vacmAccessReadViewName SnmpAdminString,
 vacmAccessWriteViewName SnmpAdminString,
 vacmAccessNotifyViewName SnmpAdminString,
 vacmAccessStorageType StorageType,
 vacmAccessStatus RowStatus
 }
vacmAccessContextPrefix OBJECT-TYPE
 SYNTAX SnmpAdminString (SIZE(0..32))
 MAX-ACCESS not-accessible
 STATUS current
 DESCRIPTION "In order to gain the access rights allowed by this
 conceptual row, a contextName must match exactly
 (if the value of vacmAccessContextMatch is 'exact')
 or partially (if the value of vacmAccessContextMatch
 is 'prefix') to the value of the instance of this
 object.
 "
 ::= { vacmAccessEntry 1 }
vacmAccessSecurityModel OBJECT-TYPE
 SYNTAX SnmpSecurityModel
 MAX-ACCESS not-accessible
 STATUS current
 DESCRIPTION "In order to gain the access rights allowed by this
 conceptual row, this securityModel must be in use.
 "
 ::= { vacmAccessEntry 2 }
vacmAccessSecurityLevel OBJECT-TYPE
 SYNTAX SnmpSecurityLevel
 MAX-ACCESS not-accessible
 STATUS current
 DESCRIPTION "The minimum level of security required in order to
 gain the access rights allowed by this conceptual
 row. A securityLevel of noAuthNoPriv is less than
 authNoPriv which in turn is less than authPriv.
 If multiple entries are equally indexed except for
 this vacmAccessSecurityLevel index, then the entry
 which has the highest value for
 vacmAccessSecurityLevel is selected.
 "
 ::= { vacmAccessEntry 3 }
vacmAccessContextMatch OBJECT-TYPE
 SYNTAX INTEGER
 { exact (1), -- exact match of prefix and contextName
 prefix (2) -- Only match to the prefix
 }
 MAX-ACCESS read-create
 STATUS current
 DESCRIPTION "If the value of this object is exact(1), then all
 rows where the contextName exactly matches
 vacmAccessContextPrefix are selected.
 If the value of this object is prefix(2), then all
 rows where the contextName whose starting octets
 exactly match vacmAccessContextPrefix are selected.
 This allows for a simple form of wildcarding.
 "
 DEFVAL { exact }
 ::= { vacmAccessEntry 4 }
vacmAccessReadViewName OBJECT-TYPE
 SYNTAX SnmpAdminString (SIZE(0..32))
 MAX-ACCESS read-create
 STATUS current
 DESCRIPTION "The value of an instance of this object identifies
 the MIB view of the SNMP context to which this
 conceptual row authorizes read access.
 The identified MIB view is that one for which the
 vacmViewTreeFamilyViewName has the same value as the
 instance of this object; if the value is the empty
 string or if there is no active MIB view having this
 value of vacmViewTreeFamilyViewName, then no access
 is granted.
 "
 DEFVAL { ''H } -- the empty string
 ::= { vacmAccessEntry 5 }
vacmAccessWriteViewName OBJECT-TYPE
 SYNTAX SnmpAdminString (SIZE(0..32))
 MAX-ACCESS read-create
 STATUS current
 DESCRIPTION "The value of an instance of this object identifies
 the MIB view of the SNMP context to which this
 conceptual row authorizes write access.
 The identified MIB view is that one for which the
 vacmViewTreeFamilyViewName has the same value as the
 instance of this object; if the value is the empty
 string or if there is no active MIB view having this
 value of vacmViewTreeFamilyViewName, then no access
 is granted.
 "
 DEFVAL { ''H } -- the empty string
 ::= { vacmAccessEntry 6 }
vacmAccessNotifyViewName OBJECT-TYPE
 SYNTAX SnmpAdminString (SIZE(0..32))
 MAX-ACCESS read-create
 STATUS current
 DESCRIPTION "The value of an instance of this object identifies
 the MIB view of the SNMP context to which this
 conceptual row authorizes access for notifications.
 The identified MIB view is that one for which the
 vacmViewTreeFamilyViewName has the same value as the
 instance of this object; if the value is the empty
 string or if there is no active MIB view having this
 value of vacmViewTreeFamilyViewName, then no access
 is granted.
 "
 DEFVAL { ''H } -- the empty string
 ::= { vacmAccessEntry 7 }
vacmAccessStorageType OBJECT-TYPE
 SYNTAX StorageType
 MAX-ACCESS read-create
 STATUS current
 DESCRIPTION "The storage type for this conceptual row.
 Conceptual rows having the value 'permanent' need not
 allow write-access to any columnar objects in the row.
 "
 DEFVAL { nonVolatile }
 ::= { vacmAccessEntry 8 }
vacmAccessStatus OBJECT-TYPE
 SYNTAX RowStatus
 MAX-ACCESS read-create
 STATUS current
 DESCRIPTION "The status of this conceptual row.
 The RowStatus TC [RFC2579] requires that this
 DESCRIPTION clause states under which circumstances
 other objects in this row can be modified:
 The value of this object has no effect on whether
 other objects in this conceptual row can be modified.
 "
 ::= { vacmAccessEntry 9 }
-- Information about MIB views ***************************************
-- Support for instance-level granularity is optional.
--
-- In some implementations, instance-level access control
-- granularity may come at a high performance cost. Managers
-- should avoid requesting such configurations unnecessarily.
vacmMIBViews OBJECT IDENTIFIER ::= { vacmMIBObjects 5 }
vacmViewSpinLock OBJECT-TYPE
 SYNTAX TestAndIncr
 MAX-ACCESS read-write
 STATUS current
 DESCRIPTION "An advisory lock used to allow cooperating SNMP
 Command Generator applications to coordinate their
 use of the Set operation in creating or modifying
 views.
 When creating a new view or altering an existing
 view, it is important to understand the potential
 interactions with other uses of the view. The
 vacmViewSpinLock should be retrieved. The name of
 the view to be created should be determined to be
 unique by the SNMP Command Generator application by
 consulting the vacmViewTreeFamilyTable. Finally,
 the named view may be created (Set), including the
 advisory lock.
 If another SNMP Command Generator application has
 altered the views in the meantime, then the spin
 lock's value will have changed, and so this creation
 will fail because it will specify the wrong value for
 the spin lock.
 Since this is an advisory lock, the use of this lock
 is not enforced.
 "
 ::= { vacmMIBViews 1 }
vacmViewTreeFamilyTable OBJECT-TYPE
 SYNTAX SEQUENCE OF VacmViewTreeFamilyEntry
 MAX-ACCESS not-accessible
 STATUS current
 DESCRIPTION "Locally held information about families of subtrees
 within MIB views.
 Each MIB view is defined by two sets of view subtrees:
 - the included view subtrees, and
 - the excluded view subtrees.
 Every such view subtree, both the included and the
 excluded ones, is defined in this table.
 To determine if a particular object instance is in
 a particular MIB view, compare the object instance's
 OBJECT IDENTIFIER with each of the MIB view's active
 entries in this table. If none match, then the
 object instance is not in the MIB view. If one or
 more match, then the object instance is included in,
 or excluded from, the MIB view according to the
 value of vacmViewTreeFamilyType in the entry whose
 value of vacmViewTreeFamilySubtree has the most
 sub-identifiers. If multiple entries match and have
 the same number of sub-identifiers (when wildcarding
 is specified with the value of vacmViewTreeFamilyMask),
 then the lexicographically greatest instance of
 vacmViewTreeFamilyType determines the inclusion or
 exclusion.
 An object instance's OBJECT IDENTIFIER X matches an
 active entry in this table when the number of
 sub-identifiers in X is at least as many as in the
 value of vacmViewTreeFamilySubtree for the entry,
 and each sub-identifier in the value of
 vacmViewTreeFamilySubtree matches its corresponding
 sub-identifier in X. Two sub-identifiers match
 either if the corresponding bit of the value of
 vacmViewTreeFamilyMask for the entry is zero (the
 'wild card' value), or if they are equal.
 A 'family' of subtrees is the set of subtrees defined
 by a particular combination of values of
 vacmViewTreeFamilySubtree and vacmViewTreeFamilyMask.
 In the case where no 'wild card' is defined in the
 vacmViewTreeFamilyMask, the family of subtrees reduces
 to a single subtree.
 When creating or changing MIB views, an SNMP Command
 Generator application should utilize the
 vacmViewSpinLock to try to avoid collisions. See
 DESCRIPTION clause of vacmViewSpinLock.
 When creating MIB views, it is strongly advised that
 first the 'excluded' vacmViewTreeFamilyEntries are
 created and then the 'included' entries.
 When deleting MIB views, it is strongly advised that
 first the 'included' vacmViewTreeFamilyEntries are
 deleted and then the 'excluded' entries.
 If a create for an entry for instance-level access
 control is received and the implementation does not
 support instance-level granularity, then an
 inconsistentName error must be returned.
 "
 ::= { vacmMIBViews 2 }
vacmViewTreeFamilyEntry OBJECT-TYPE
 SYNTAX VacmViewTreeFamilyEntry
 MAX-ACCESS not-accessible
 STATUS current
 DESCRIPTION "Information on a particular family of view subtrees
 included in or excluded from a particular SNMP
 context's MIB view.
 Implementations must not restrict the number of
 families of view subtrees for a given MIB view,
 except as dictated by resource constraints on the
 overall number of entries in the
 vacmViewTreeFamilyTable.
 If no conceptual rows exist in this table for a given
 MIB view (viewName), that view may be thought of as
 consisting of the empty set of view subtrees.
 "
 INDEX { vacmViewTreeFamilyViewName,
 vacmViewTreeFamilySubtree
 }
 ::= { vacmViewTreeFamilyTable 1 }
VacmViewTreeFamilyEntry ::= SEQUENCE
 {
 vacmViewTreeFamilyViewName SnmpAdminString,
 vacmViewTreeFamilySubtree OBJECT IDENTIFIER,
 vacmViewTreeFamilyMask OCTET STRING,
 vacmViewTreeFamilyType INTEGER,
 vacmViewTreeFamilyStorageType StorageType,
 vacmViewTreeFamilyStatus RowStatus
 }
vacmViewTreeFamilyViewName OBJECT-TYPE
 SYNTAX SnmpAdminString (SIZE(1..32))
 MAX-ACCESS not-accessible
 STATUS current
 DESCRIPTION "The human readable name for a family of view subtrees.
 "
 ::= { vacmViewTreeFamilyEntry 1 }
vacmViewTreeFamilySubtree OBJECT-TYPE
 SYNTAX OBJECT IDENTIFIER
 MAX-ACCESS not-accessible
 STATUS current
 DESCRIPTION "The MIB subtree which when combined with the
 corresponding instance of vacmViewTreeFamilyMask
 defines a family of view subtrees.
 "
 ::= { vacmViewTreeFamilyEntry 2 }
vacmViewTreeFamilyMask OBJECT-TYPE
 SYNTAX OCTET STRING (SIZE (0..16))
 MAX-ACCESS read-create
 STATUS current
 DESCRIPTION "The bit mask which, in combination with the
 corresponding instance of vacmViewTreeFamilySubtree,
 defines a family of view subtrees.
 Each bit of this bit mask corresponds to a
 sub-identifier of vacmViewTreeFamilySubtree, with the
 most significant bit of the i-th octet of this octet
 string value (extended if necessary, see below)
 corresponding to the (8*i - 7)-th sub-identifier, and
 the least significant bit of the i-th octet of this
 octet string corresponding to the (8*i)-th
 sub-identifier, where i is in the range 1 through 16.
 Each bit of this bit mask specifies whether or not
 the corresponding sub-identifiers must match when
 determining if an OBJECT IDENTIFIER is in this
 family of view subtrees; a '1' indicates that an
 exact match must occur; a '0' indicates 'wild card',
 i.e., any sub-identifier value matches.
 Thus, the OBJECT IDENTIFIER X of an object instance
 is contained in a family of view subtrees if, for
 each sub-identifier of the value of
 vacmViewTreeFamilySubtree, either:
 the i-th bit of vacmViewTreeFamilyMask is 0, or
 the i-th sub-identifier of X is equal to the i-th
 sub-identifier of the value of
 vacmViewTreeFamilySubtree.
 If the value of this bit mask is M bits long and
 there are more than M sub-identifiers in the
 corresponding instance of vacmViewTreeFamilySubtree,
 then the bit mask is extended with 1's to be the
 required length.
 Note that when the value of this object is the
 zero-length string, this extension rule results in
 a mask of all-1's being used (i.e., no 'wild card'),
 and the family of view subtrees is the one view
 subtree uniquely identified by the corresponding
 instance of vacmViewTreeFamilySubtree.
 Note that masks of length greater than zero length
 do not need to be supported. In this case this
 object is made read-only.
 "
 DEFVAL { ''H }
 ::= { vacmViewTreeFamilyEntry 3 }
vacmViewTreeFamilyType OBJECT-TYPE
 SYNTAX INTEGER { included(1), excluded(2) }
 MAX-ACCESS read-create
 STATUS current
 DESCRIPTION "Indicates whether the corresponding instances of
 vacmViewTreeFamilySubtree and vacmViewTreeFamilyMask
 define a family of view subtrees which is included in
 or excluded from the MIB view.
 "
 DEFVAL { included }
 ::= { vacmViewTreeFamilyEntry 4 }
vacmViewTreeFamilyStorageType OBJECT-TYPE
 SYNTAX StorageType
 MAX-ACCESS read-create
 STATUS current
 DESCRIPTION "The storage type for this conceptual row.
 Conceptual rows having the value 'permanent' need not
 allow write-access to any columnar objects in the row.
 "
 DEFVAL { nonVolatile }
 ::= { vacmViewTreeFamilyEntry 5 }
vacmViewTreeFamilyStatus OBJECT-TYPE
 SYNTAX RowStatus
 MAX-ACCESS read-create
 STATUS current
 DESCRIPTION "The status of this conceptual row.
 The RowStatus TC [RFC2579] requires that this
 DESCRIPTION clause states under which circumstances
 other objects in this row can be modified:
 The value of this object has no effect on whether
 other objects in this conceptual row can be modified.
 "
 ::= { vacmViewTreeFamilyEntry 6 }
-- Conformance information *******************************************
vacmMIBCompliances OBJECT IDENTIFIER ::= { vacmMIBConformance 1 }
vacmMIBGroups OBJECT IDENTIFIER ::= { vacmMIBConformance 2 }
-- Compliance statements *********************************************
vacmMIBCompliance MODULE-COMPLIANCE
 STATUS current
 DESCRIPTION "The compliance statement for SNMP engines which
 implement the SNMP View-based Access Control Model
 configuration MIB.
 "
 MODULE -- this module
 MANDATORY-GROUPS { vacmBasicGroup }
 OBJECT vacmAccessContextMatch
 MIN-ACCESS read-only
 DESCRIPTION "Write access is not required."
 OBJECT vacmAccessReadViewName
 MIN-ACCESS read-only
 DESCRIPTION "Write access is not required."
 OBJECT vacmAccessWriteViewName
 MIN-ACCESS read-only
 DESCRIPTION "Write access is not required."
 OBJECT vacmAccessNotifyViewName
 MIN-ACCESS read-only
 DESCRIPTION "Write access is not required."
 OBJECT vacmAccessStorageType
 MIN-ACCESS read-only
 DESCRIPTION "Write access is not required."
 OBJECT vacmAccessStatus
 MIN-ACCESS read-only
 DESCRIPTION "Create/delete/modify access to the
 vacmAccessTable is not required.
 "
 OBJECT vacmViewTreeFamilyMask
 WRITE-SYNTAX OCTET STRING (SIZE (0))
 MIN-ACCESS read-only
 DESCRIPTION "Support for configuration via SNMP of subtree
 families using wild-cards is not required.
 "
 OBJECT vacmViewTreeFamilyType
 MIN-ACCESS read-only
 DESCRIPTION "Write access is not required."
 OBJECT vacmViewTreeFamilyStorageType
 MIN-ACCESS read-only
 DESCRIPTION "Write access is not required."
 OBJECT vacmViewTreeFamilyStatus
 MIN-ACCESS read-only
 DESCRIPTION "Create/delete/modify access to the
 vacmViewTreeFamilyTable is not required.
 "
 ::= { vacmMIBCompliances 1 }
-- Units of conformance **********************************************
vacmBasicGroup OBJECT-GROUP
 OBJECTS {
 vacmContextName,
 vacmGroupName,
 vacmSecurityToGroupStorageType,
 vacmSecurityToGroupStatus,
 vacmAccessContextMatch,
 vacmAccessReadViewName,
 vacmAccessWriteViewName,
 vacmAccessNotifyViewName,
 vacmAccessStorageType,
 vacmAccessStatus,
 vacmViewSpinLock,
 vacmViewTreeFamilyMask,
 vacmViewTreeFamilyType,
 vacmViewTreeFamilyStorageType,
 vacmViewTreeFamilyStatus
 }
 STATUS current
 DESCRIPTION "A collection of objects providing for remote
 configuration of an SNMP engine which implements
 the SNMP View-based Access Control Model.
 "
 ::= { vacmMIBGroups 1 }
END
5. Intellectual Property
 The IETF takes no position regarding the validity or scope of any
 intellectual property or other rights that might be claimed to
 pertain to the implementation or use of the technology described in
 this document or the extent to which any license under such rights
 might or might not be available; neither does it represent that it
 has made any effort to identify any such rights. Information on the
 IETF's procedures with respect to rights in standards-track and
 standards-related documentation can be found in BCP-11. Copies of
 claims of rights made available for publication and any assurances of
 licenses to be made available, or the result of an attempt made to
 obtain a general license or permission for the use of such
 proprietary rights by implementors or users of this specification can
 be obtained from the IETF Secretariat.
 The IETF invites any interested party to bring to its attention any
 copyrights, patents or patent applications, or other proprietary
 rights which may cover technology that may be required to practice
 this standard. Please address the information to the IETF Executive
 Director.
6. Acknowledgements
 This document is the result of the efforts of the SNMPv3 Working
 Group. Some special thanks are in order to the following SNMPv3 WG
 members:
 Harald Tveit Alvestrand (Maxware)
 Dave Battle (SNMP Research, Inc.)
 Alan Beard (Disney Worldwide Services)
 Paul Berrevoets (SWI Systemware/Halcyon Inc.)
 Martin Bjorklund (Ericsson)
 Uri Blumenthal (IBM T.J. Watson Research Center)
 Jeff Case (SNMP Research, Inc.)
 John Curran (BBN)
 Mike Daniele (Compaq Computer Corporation)
 T. Max Devlin (Eltrax Systems)
 John Flick (Hewlett Packard)
 Rob Frye (MCI)
 Wes Hardaker (U.C.Davis, Information Technology - D.C.A.S.)
 David Harrington (Cabletron Systems Inc.)
 Lauren Heintz (BMC Software, Inc.)
 N.C. Hien (IBM T.J. Watson Research Center)
 Michael Kirkham (InterWorking Labs, Inc.)
 Dave Levi (SNMP Research, Inc.)
 Louis A Mamakos (UUNET Technologies Inc.)
 Joe Marzot (Nortel Networks)
 Paul Meyer (Secure Computing Corporation)
 Keith McCloghrie (Cisco Systems)
 Bob Moore (IBM)
 Russ Mundy (TIS Labs at Network Associates)
 Bob Natale (ACE*COMM Corporation)
 Mike O'Dell (UUNET Technologies Inc.)
 Dave Perkins (DeskTalk)
 Peter Polkinghorne (Brunel University)
 Randy Presuhn (BMC Software, Inc.)
 David Reeder (TIS Labs at Network Associates)
 David Reid (SNMP Research, Inc.)
 Aleksey Romanov (Quality Quorum)
 Shawn Routhier (Epilogue)
 Juergen Schoenwaelder (TU Braunschweig)
 Bob Stewart (Cisco Systems)
 Mike Thatcher (Independent Consultant)
 Bert Wijnen (IBM T.J. Watson Research Center)
 The document is based on recommendations of the IETF Security and
 Administrative Framework Evolution for SNMP Advisory Team. Members
 of that Advisory Team were:
 David Harrington (Cabletron Systems Inc.)
 Jeff Johnson (Cisco Systems)
 David Levi (SNMP Research Inc.)
 John Linn (Openvision)
 Russ Mundy (Trusted Information Systems) chair
 Shawn Routhier (Epilogue)
 Glenn Waters (Nortel)
 Bert Wijnen (IBM T. J. Watson Research Center)
 As recommended by the Advisory Team and the SNMPv3 Working Group
 Charter, the design incorporates as much as practical from previous
 RFCs and drafts. As a result, special thanks are due to the authors
 of previous designs known as SNMPv2u and SNMPv2*:
 Jeff Case (SNMP Research, Inc.)
 David Harrington (Cabletron Systems Inc.)
 David Levi (SNMP Research, Inc.)
 Keith McCloghrie (Cisco Systems)
 Brian O'Keefe (Hewlett Packard)
 Marshall T. Rose (Dover Beach Consulting)
 Jon Saperia (BGS Systems Inc.)
 Steve Waldbusser (International Network Services)
 Glenn W. Waters (Bell-Northern Research Ltd.)
7. Security Considerations
7.1. Recommended Practices
 This document is meant for use in the SNMP architecture. The View-
 based Access Control Model described in this document checks access
 rights to management information based on:
 - contextName, representing a set of management information at the
 managed system where the Access Control module is running.
 - groupName, representing a set of zero or more securityNames. The
 combination of a securityModel and a securityName is mapped into a
 group in the View-based Access Control Model.
 - securityModel under which access is requested.
 - securityLevel under which access is requested.
 - operation performed on the management information.
 - MIB views for read, write or notify access.
 When the User-based Access Control module is called for checking
 access rights, it is assumed that the calling module has ensured the
 authentication and privacy aspects as specified by the securityLevel
 that is being passed.
 When creating entries in or deleting entries from the
 vacmViewTreeFamilyTable it is important to do such in the sequence as
 recommended in the DESCRIPTION clause of the vacmViewTreeFamilyTable
 definition. Otherwise unwanted access may be granted while changing
 the entries in the table.
7.2. Defining Groups
 The groupNames are used to give access to a group of zero or more
 securityNames. Within the View-Based Access Control Model, a
 groupName is considered to exist if that groupName is listed in the
 vacmSecurityToGroupTable.
 By mapping the combination of a securityModel and securityName into a
 groupName, an SNMP Command Generator application can add/delete
 securityNames to/from a group, if proper access is allowed.
 Further it is important to realize that the grouping of
 <securityModel, securityName> tuples in the vacmSecurityToGroupTable
 does not take securityLevel into account. It is therefore important
 that the security administrator uses the securityLevel index in the
 vacmAccessTable to separate noAuthNoPriv from authPriv and/or
 authNoPriv access.
7.3. Conformance
 For an implementation of the View-based Access Control Model to be
 conformant, it MUST implement the SNMP-VIEW-BASED-ACM-MIB according
 to the vacmMIBCompliance. It also SHOULD implement the initial
 configuration, described in appendix A.
7.4. Access to the SNMP-VIEW-BASED-ACM-MIB
 The objects in this MIB control the access to all MIB data that is
 accessible via the SNMP engine and they may be considered sensitive
 in many environments. It is important to closely control (both read
 and write) access to these to these MIB objects by using
 appropriately configured Access Control models (for example the
 View-based Access Control Model as specified in this document).
8. References
8.1. Normative References
 [RFC2119] Bradner, S., "Key words for use in RFCs to Indicate
 Requirement Levels", BCP 14, RFC 2119, March 1997.
 [RFC2578] McCloghrie, K., Perkins, D., Schoenwaelder, J., Case, J.,
 Rose, M. and S. Waldbusser, "Structure of Management
 Information Version 2 (SMIv2)", STD 58, RFC 2578, April
 1999.
 [RFC2579] McCloghrie, K., Perkins, D., Schoenwaelder, J., Case, J.,
 Rose, M. and S. Waldbusser, "Textual Conventions for
 SMIv2", STD 58, RFC 2579, April 1999.
 [RFC2580] McCloghrie, K., Perkins, D., Schoenwaelder, J., Case, J.,
 Rose, M. and S. Waldbusser, "Conformance Statements for
 SMIv2", STD 58, RFC 2580, April 1999.
 [RFC3411] Harrington, D., Presuhn, R. and B. Wijnen, "An
 Architecture for describing Simple Network Management
 Protocol (SNMP) Management Frameworks", STD 62, RFC 3411,
 December 2002.
 [SNMP3412] Case, J., Harrington, D., Presuhn, R. and B. Wijnen,
 "Message Processing and Dispatching for the Simple
 Network Management Protocol (SNMP)", STD 62, RFC 3412,
 December 2002.
 [RFC3414] Blumenthal, U. and B. Wijnen, "User-based Security Model
 (USM) for version 3 of the Simple Network Management
 Protocol (SNMPv3)", STD 62, RFC 3414, December 2002.
8.2. Informative References
 [ISO-ASN.1] Information processing systems - Open Systems
 Interconnection - Specification of Abstract Syntax
 Notation One (ASN.1), International Organization for
 Standardization. International Standard 8824, (December,
 1987).
Appendix A - Installation
A.1. Installation Parameters
 During installation, an authoritative SNMP engine which supports this
 View-based Access Control Model SHOULD be configured with several
 initial parameters. These include for the View-based Access Control
 Model:
 1) A security configuration
 The choice of security configuration determines if initial
 configuration is implemented and if so how. One of three possible
 choices is selected:
 - initial-minimum-security-configuration
 - initial-semi-security-configuration
 - initial-no-access-configuration
 In the case of a initial-no-access-configuration, there is no
 initial configuration, and so the following steps are irrelevant.
 2) A default context
 One entry in the vacmContextTable with a contextName of "" (the
 empty string), representing the default context. Note that this
 table gets created automatically if a default context exists.
 vacmContextName ""
 3) An initial group
 One entry in the vacmSecurityToGroupTable to allow access to group
 "initial".
 vacmSecurityModel 3 (USM)
 vacmSecurityName "initial"
 vacmGroupName "initial"
 vacmSecurityToGroupStorageType anyValidStorageType
 vacmSecurityToGroupStatus active
 4) Initial access rights
 Three entries in the vacmAccessTable as follows:
 - read-notify access for securityModel USM, securityLevel
 "noAuthNoPriv" on behalf of securityNames that belong to the
 group "initial" to the <restricted> MIB view in the default
 context with contextName "".
 - read-write-notify access for securityModel USM, securityLevel
 "authNoPriv" on behalf of securityNames that belong to the
 group "initial" to the <internet> MIB view in the default
 context with contextName "".
 - if privacy is supported, read-write-notify access for
 securityModel USM, securityLevel "authPriv" on behalf of
 securityNames that belong to the group "initial" to the
 <internet> MIB view in the default context with contextName "".
 That translates into the following entries in the vacmAccessTable.
 - One entry to be used for unauthenticated access (noAuthNoPriv):
 vacmGroupName "initial"
 vacmAccessContextPrefix ""
 vacmAccessSecurityModel 3 (USM)
 vacmAccessSecurityLevel noAuthNoPriv
 vacmAccessContextMatch exact
 vacmAccessReadViewName "restricted"
 vacmAccessWriteViewName ""
 vacmAccessNotifyViewName "restricted"
 vacmAccessStorageType anyValidStorageType
 vacmAccessStatus active
 - One entry to be used for authenticated access (authNoPriv) with
 optional privacy (authPriv):
 vacmGroupName "initial"
 vacmAccessContextPrefix ""
 vacmAccessSecurityModel 3 (USM)
 vacmAccessSecurityLevel authNoPriv
 vacmAccessContextMatch exact
 vacmAccessReadViewName "internet"
 vacmAccessWriteViewName "internet"
 vacmAccessNotifyViewName "internet"
 vacmAccessStorageType anyValidStorageType
 vacmAccessStatus active
 5) Two MIB views, of which the second one depends on the security
 configuration.
 - One view, the <internet> view, for authenticated access:
 - the <internet> MIB view is the following subtree:
 "internet" (subtree 1.3.6.1)
 - A second view, the <restricted> view, for unauthenticated
 access. This view is configured according to the selected
 security configuration:
 - For the initial-no-access-configuration there is no default
 initial configuration, so no MIB views are pre-scribed.
 - For the initial-semi-secure-configuration:
 the <restricted> MIB view is the union of these subtrees:
 (a) "system" (subtree 1.3.6.1.2.1.1) [RFC3918]
 (b) "snmp" (subtree 1.3.6.1.2.1.11) [RFC3918]
 (c) "snmpEngine" (subtree 1.3.6.1.6.3.10.2.1) [RFC3411]
 (d) "snmpMPDStats" (subtree 1.3.6.1.6.3.11.2.1) [RFC3412]
 (e) "usmStats" (subtree 1.3.6.1.6.3.15.1.1) [RFC3414]
 - For the initial-minimum-secure-configuration:
 the <restricted> MIB view is the following subtree.
 "internet" (subtree 1.3.6.1)
 This translates into the following "internet" entry in the
 vacmViewTreeFamilyTable:
 minimum-secure semi-secure
 ---------------- ---------------
 vacmViewTreeFamilyViewName "internet" "internet"
 vacmViewTreeFamilySubtree 1.3.6.1 1.3.6.1
 vacmViewTreeFamilyMask "" ""
 vacmViewTreeFamilyType 1 (included) 1 (included)
 vacmViewTreeFamilyStorageType anyValidStorageType anyValidStorageType
 vacmViewTreeFamilyStatus active active
 In addition it translates into the following "restricted" entries in
 the vacmViewTreeFamilyTable:
 minimum-secure semi-secure
 ---------------- ---------------
 vacmViewTreeFamilyViewName "restricted" "restricted"
 vacmViewTreeFamilySubtree 1.3.6.1 1.3.6.1.2.1.1
 vacmViewTreeFamilyMask "" ""
 vacmViewTreeFamilyType 1 (included) 1 (included)
 vacmViewTreeFamilyStorageType anyValidStorageType anyValidStorageType
 vacmViewTreeFamilyStatus active active
 vacmViewTreeFamilyViewName "restricted"
 vacmViewTreeFamilySubtree 1.3.6.1.2.1.11
 vacmViewTreeFamilyMask ""
 vacmViewTreeFamilyType 1 (included)
 vacmViewTreeFamilyStorageType anyValidStorageType
 vacmViewTreeFamilyStatus active
 vacmViewTreeFamilyViewName "restricted"
 vacmViewTreeFamilySubtree 1.3.6.1.6.3.10.2.1
 vacmViewTreeFamilyMask ""
 vacmViewTreeFamilyType 1 (included)
 vacmViewTreeFamilyStorageType anyValidStorageType
 vacmViewTreeFamilyStatus active
 vacmViewTreeFamilyViewName "restricted"
 vacmViewTreeFamilySubtree 1.3.6.1.6.3.11.2.1
 vacmViewTreeFamilyMask ""
 vacmViewTreeFamilyType 1 (included)
 vacmViewTreeFamilyStorageType anyValidStorageType
 vacmViewTreeFamilyStatus active
 vacmViewTreeFamilyViewName "restricted"
 vacmViewTreeFamilySubtree 1.3.6.1.6.3.15.1.1
 vacmViewTreeFamilyMask ""
 vacmViewTreeFamilyType 1 (included)
 vacmViewTreeFamilyStorageType anyValidStorageType
 vacmViewTreeFamilyStatus active
B. Change Log
 Changes made since RFC 2575:
 - Removed reference from abstract as per RFC-Editor guidelines
 - Updated references
 Changes made since RFC 2275:
 - Added text to vacmSecurityToGroupStatus DESCRIPTION clause to
 clarify under which conditions an entry in the
 vacmSecurityToGroupTable can be made active.
 - Added REVISION clauses to MODULE-IDENTITY
 - Clarified text in vacmAccessTable DESCRIPTION clause.
 - Added a DEFVAL clause to vacmAccessContextMatch object.
 - Added missing columns in Appendix A and re-arranged for
 clarity.
 - Fixed oids in appendix A.
 - Use the PDU Class terminology instead of RFC1905 PDU types.
 - Added section 7.4 about access control to the MIB.
 - Fixed references to new/revised documents
 - Fix Editor contact information.
 - fixed spelling errors
 - removed one vacmAccesEntry from sample in appendix A.
 - made some more clarifications.
 - updated acknowledgement section.
Editors' Addresses
 Bert Wijnen
 Lucent Technologies
 Schagen 33
 3461 GL Linschoten
 Netherlands
 Phone: +31-348-480-685
 EMail: bwijnen@lucent.com
 Randy Presuhn
 BMC Software, Inc.
 2141 North First Street
 San Jose, CA 95131
 USA
 Phone: +1 408-546-1006
 EMail: randy_presuhn@bmc.com
 Keith McCloghrie
 Cisco Systems, Inc.
 170 West Tasman Drive
 San Jose, CA 95134-1706
 USA
 Phone: +1-408-526-5260
 EMail: kzm@cisco.com
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