rfc2275.txt

著名的RFC文档,其中有一些文档是已经翻译成中文的的.

             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
             )



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   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.






















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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:



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                                  - 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.





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   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 "9711200000Z"            -- 20 Nov 1997, midnight
    ORGANIZATION "SNMPv3 Working Group"
    CONTACT-INFO "WG-email:   [e-mail]
                  Subscribe:  [e-mail]
                              In message body:  subscribe snmpv3



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                  Chair:      Russ Mundy
                              Trusted Information Systems
                  postal:     3060 Washington Rd
                              Glenwood MD 21738
                              USA
                  email:      [e-mail]
                  phone:      [phone]

                  Co-editor:  Bert Wijnen
                              IBM T.J. Watson Research
                  postal:     Schagen 33
                              3461 GL Linschoten
                              Netherlands
                  email:      [e-mail]
                  phone:      [phone]

                  Co-editor:  Randy Presuhn
                              BMC Software, Inc
                  postal:     1190 Saratoga Avenue, Suite 130
                              San Jose, CA  95129-3433
                              USA
                  email:      [e-mail]
                  phone:      [phone]

                  Co-editor:  Keith McCloghrie
                              Cisco Systems, Inc.
                  postal:     170 West Tasman Drive
                              San Jose, CA  95134-1706
                              USA
                  email:      [e-mail]
                  phone:      [phone]
                 "
    DESCRIPTION  "The management information definitions for the
                  View-based Access Control Model for SNMP.
                 "
    ::= { 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



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    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