





INTERNET-DRAFT                                                   S. Legg
draft-legg-ldap-acm-bac-02.txt                       Adacel Technologies
Intended Category: Standards Track                     February 25, 2003
Updates: RFC 2252


              Basic and Simplified Access Control in LDAP

    Copyright (C) The Internet Society (2003). All Rights Reserved.

   Status of this Memo


   This document is an Internet-Draft and is in full conformance with
   all provisions of Section 10 of RFC2026.

   Internet-Drafts are working documents of the Internet Engineering
   Task Force (IETF), its areas, and its working groups.  Note that
   other groups may also distribute working documents as
   Internet-Drafts.

   Internet-Drafts are draft documents valid for a maximum of six months
   and may be updated, replaced, or obsoleted by other documents at any
   time.  It is inappropriate to use Internet-Drafts as reference
   material or to cite them other than as "work in progress".

   The list of current Internet-Drafts can be accessed at
   http://www.ietf.org/ietf/1id-abstracts.txt

   The list of Internet-Draft Shadow Directories can be accessed at
   http://www.ietf.org/shadow.html.

   Distribution of this document is unlimited.  Comments should be sent
   to the LDUP working group mailing list <ietf-ldup@imc.org> or to the
   author.

   This Internet-Draft expires on 25 August 2003.


1. Abstract

   An access control scheme describes the means by which access to
   directory information and potentially to access rights themselves may
   be controlled.  This document adapts the X.500 directory Basic Access
   Control and Simplied Access Control schemes for use by the
   Lightweight Directory Access Protocol.





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2. Table of Contents

   1. Abstract ......................................................  1
   2. Table of Contents .............................................  2
   3. Introduction ..................................................  3
   4. Conventions ...................................................  3
   5. Basic Access Control ..........................................  4
      5.1 Permissions ...............................................  5
         5.1.1 Read .................................................  5
         5.1.2 Compare ..............................................  6
         5.1.3 Browse ...............................................  6
         5.1.4 ReturnDN .............................................  6
         5.1.5 FilterMatch ..........................................  6
         5.1.6 Modify ...............................................  6
         5.1.7 Add ..................................................  7
         5.1.8 Remove ...............................................  7
         5.1.9 DiscloseOnError ......................................  7
         5.1.10 Rename ..............................................  7
         5.1.11 Export ..............................................  8
         5.1.12 Import ..............................................  8
         5.1.13 Invoke ..............................................  8
      5.2 Representation of Access Control Information ..............  8
         5.2.1 Identification Tag ................................... 11
         5.2.2 Precedence ........................................... 11
         5.2.3 Authentication Level ................................. 12
         5.2.4 itemFirst and userFirst Components ................... 13
         5.2.5 Determining Group Membership ......................... 16
      5.3 ACI Operational Attributes ................................ 17
         5.3.1 Prescriptive ACI ..................................... 17
         5.3.2 Entry ACI ............................................ 18
         5.3.3 Subentry ACI ......................................... 18
         5.3.4 Protecting the ACI ................................... 18
      5.4 Access Control Decision Points for LDAP Operations ........ 19
         5.4.1 Common Elements of Procedure ......................... 19
            5.4.1.1 Alias Dereferencing ............................. 19
            5.4.1.2 Return of Names in Errors ....................... 20
            5.4.1.3 Non-disclosure of the Existence of an Entry ..... 20
         5.4.2 Compare Operation Decision Points .................... 21
         5.4.3 Search Operation Decision Points ..................... 21
         5.4.4 Add Operation Decision Points ........................ 24
         5.4.5 Delete Operation Decision Points ..................... 25
         5.4.6 Modify Operation Decision Points ..................... 25
         5.4.7 Modify DN Operation Decision Points .................. 26
      5.5 Access Control Decision Function .......................... 27
         5.5.1 Inputs ............................................... 27
         5.5.2 Tuples ............................................... 27
         5.5.3 Discarding Irrelevant Tuples ......................... 28
         5.5.4 Highest Precedence and Specificity ................... 29



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   6. Simplified Access Control ..................................... 29
   7. Security Considerations ....................................... 30
   8. Acknowledgements .............................................. 30
   9. IANA Considerations ........................................... 30
   10. Normative References ......................................... 31
   11. Informative References ....................................... 32
   12. Copyright Notice ............................................. 33
   13. Author's Address ............................................. 33
   Appendix A. LDAP Specific Encoding for the ACI Item Syntax ....... 33


3. Introduction

   An access control scheme describes the means by which access to
   directory information and potentially to access rights themselves may
   be controlled.  Control of access to information means the prevention
   of unauthorized detection, disclosure, or modification of that
   information.  The definition of an access control scheme in the
   context of a Lightweight Directory Access Protocol (LDAP) [RFC3371]
   directory includes methods to specify Access Control Information
   (ACI), and to enforce access rights defined by that ACI.

   This document adapts the X.500 Basic Access Control and Simplied
   Access Control schemes [X501] for use in LDAP.  Both schemes conform
   to, and make use of, the access control administrative framework
   described in [ACA].

   Section 5 describes the Basic Access Control scheme and defines how
   it applies to LDAP operations [RFC2251].

   Simplified Access Control is a functional subset of the Basic Access
   Control scheme.  This subset is described in Section 6.

   As a matter of security policy, an implementation supporting Basic
   Access Control or Simplified Access Control is permitted to grant or
   deny any form of access to particular attributes (e.g. password
   attributes) irrespective of access controls which may otherwise
   apply.  However, since such security policy has no standardized
   representation, it cannot be propagated in replicated information.

   This document is derived from, and duplicates substantial portions
   of, Section 8 of [X501], and selected extracts from [X511].

4. Conventions

   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 RFC 2119 [RFC2119].



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   Schema definitions are provided using LDAP description formats
   [RFC2252].  Note that the LDAP descriptions have been rendered with
   additional white-space and line breaks for the sake of readability.


5. Basic Access Control

   This section describes the functionality of the Basic Access Control
   scheme.

   When Basic Access Control is used, the accessControlScheme
   operational attribute [ACA] SHALL have the value basic-access-control
   (2.5.28.1).

   This LDAP profile for Basic Access Control defines, for every LDAP
   operation, one or more points at which access control decisions take
   place.  An access control decision will involve a requestor,
   protected items, and permissions.

   A requestor is the user requesting the operation.  Basic Access
   Control requires a user's authorization identity to be represented as
   a distinguished name (with an optional unique identifier).  The
   mapping of the authentication identity to an authorization identity,
   and the mapping of the authorization identity to a distinguished name
   and optional unique identifier, are outside the scope of this
   document.

   A protected item is the element of directory information being
   accessed.  The protected items are entries, attributes, attribute
   values and distinguished names.  Access to each protected item can be
   separately controlled through ACI.

   A permission is a particular right necessary to complete a portion of
   the operation.

   The Access Control Information, which is used to make access control
   decisions, associates protected items and user classes with
   permissions.  ACI is represented in the directory as values of
   operational attributes with the ACI Item syntax [RFC2252].  Each such
   value is referred to as an ACI item.

   The scope of access controls can be a single entry or a collection of
   entries that are logically related by being within the scope of an
   access control subentry of an administrative point (see [ACA]).

   The Access Control Decision Function (ACDF) (Section 5.5) is used to
   decide whether a particular requestor has a particular access right
   by virtue of applicable ACI items.



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   Access to DSEs and operational attributes is controlled in the same
   way as for entries and user attributes.

   For query purposes, collective attributes [COLLECT] that are
   associated with an entry are protected precisely as if they were
   attributes actually stored in that entry.

   For the purposes of modification, collective attributes are
   associated with the subentry that holds them, not with entries within
   the scope of the subentry.  Modify-related access controls are
   therefore not relevant to collective attributes, except when they
   apply to the collective attribute and its values within the subentry.


5.1 Permissions

   Access is controlled by granting or denying permissions.  Access is
   allowed only when there is an explicitly provided grant present in
   the ACI used to make the access control decision.  The only default
   access decision provided in the model is to deny access in the
   absence of explicit ACI that grants access.  All other factors being
   equal, a denial specified in ACI always overrides a grant.

   Certain combinations of grants or denials are illogical, but it is
   the responsibility of directory clients, rather than the directory
   server, to ensure that such combinations are absent.

   The decision whether or not to permit access to an entry or its
   contents is strictly determined by the position of the entry in the
   Directory Information Tree (DIT), in terms of its distinguished name,
   and is independent of how the directory server locates that entry.

   The following sections introduce the permissions by indicating the
   intent associated with the granting of each.  The actual influence of
   a particular granted permission on access control decisions are,
   however, determined by the ACDF and the access control decision
   points for each LDAP operation, described in detail in Section 5.4.


5.1.1 Read

   If granted for an entry, Read permits the entry to be accessed using
   LDAP Compare and baseObject Search operations, but does not imply
   access to all the attributes and values.

   If granted for an attribute type, Read permits the attribute type to
   be returned as entry information in a Search result.  Read or Browse
   permission for the entry is a prerequisite.



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   If granted for an attribute value, Read permits the attribute value
   to be returned as entry information in a Search result.  Read or
   Browse permission for the entry and Read permission for the attribute
   type are prerequisites.


5.1.2 Compare

   If granted for an attribute type, Compare permits the attribute type
   to be tested by the assertion in an LDAP Compare operation.  Read
   permission for the entry is a prerequisite.

   If granted for an attribute value, Compare permits the value to be
   tested by the assertion in an LDAP Compare operation.  Read
   permission for the entry and Compare permission for the attribute
   type are prerequisites.


5.1.3 Browse

   If granted for an entry, Browse permits the entry to be accessed by
   the LDAP Search operation, including baseObject searches, but does
   not imply access to all the attributes and values.


5.1.4 ReturnDN

   If granted for an entry, ReturnDN allows the distinguished name of
   the entry to be disclosed in a search result.


5.1.5 FilterMatch

   If granted for an attribute type, Filtermatch permits the attribute
   type to satisfy a Filter item.

   If granted for an attribute value, Filtermatch permits the attribute
   value to satisfy a Filter item.  FilterMatch permission for the
   attribute type is a prerequisite.


5.1.6 Modify

   If granted for an entry, Modify permits the information contained
   within an entry to be modified by the LDAP Modify operation, subject
   to controls on the attribute types and values.





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5.1.7 Add

   If granted for an entry, Add permits creation of an entry in the DIT,
   subject to being able to add all specified attributes and attribute
   values.  Add permission granted for an entry is ineffective if Add
   permission is not also granted for at least the mandatory attributes
   and their values.  There is no specific "add subordinate permission".
   Permission to add an entry is controlled using prescriptive ACI.

   If granted for an attribute type, Add permits adding a new attribute,
   subject to being able to add all specified attribute values.  Add or
   Modify permission for the entry is a prerequisite.

   If granted for an attribute value, Add permits adding that value to
   an existing attribute.  Add or Modify permission for the entry is a
   prerequisite.


5.1.8 Remove

   If granted for an entry, Remove permits the entry to be removed from
   the DIT regardless of controls on attributes or attribute values
   within the entry.

   If granted for an attribute, Remove permits removing an attribute,
   subject to being able to remove any explicitly specified attribute
   values.  Remove permission for values not explicitly specified is not
   required.

   If granted for an attribute value, Remove permits the attribute value
   to be removed from an existing attribute.


5.1.9 DiscloseOnError

   If granted for an entry, DiscloseOnError permits the name of an entry
   to be disclosed in an error result.

   If granted for an attribute, DiscloseOnError permits the presence of
   the attribute to be disclosed by an error.

   If granted for an attribute value, DiscloseOnError permits the
   presence of the attribute value to be disclosed by an error.


5.1.10 Rename

   If granted for an entry, Rename permits an entry to be renamed with a



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   new RDN.  No permissions are required for the attributes and values
   altered by the operation, even if they are added or removed as a
   result of the changes to the RDN.


5.1.11 Export

   If granted for an entry, Export permits the entry and its
   subordinates, if any, to be removed from the current location and
   placed in a new location, subject to the granting of Import
   permission at the destination.

   If the last RDN is changed, Rename permission at the current location
   is also required


5.1.12 Import

   If granted for an entry, Import permits an entry and its
   subordinates, if any, to be placed at the location to which the
   permission applies, subject to the granting of Export permission at
   the source location.


5.1.13 Invoke

   Invoke, if granted for an operational attribute, or value thereof,
   permits the directory server to carry out some function associated
   with the operational attribute on behalf of the user.  The specific
   function carried out by invocation depends on the attribute.  No
   other permissions are required by user for the operational attribute,
   or on the entry/subentry that holds it, in order for it to be
   "invoked".


5.2 Representation of Access Control Information

   Access Control Information is represented as a set of ACI items,
   where each ACI item grants or denies permissions in regard to certain
   specified users and protected items.

   An ACI item is represented as a value of an operational attribute
   with the ACI Item syntax (1.3.6.1.4.1.1466.115.121.1.1) [RFC2252].

   This document updates [RFC2252] by specifying a human-readable
   LDAP-specific encoding for ACI items.  The LDAP-specific encoding of
   values of the ACI Item syntax is defined by the Generic String
   Encoding Rules described in [GSER].  Appendix A provides an



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   equivalent ABNF for this syntax.

   For convenience in specifying access control policies, the ACI Item
   syntax provides the means to identify collections of related items,
   such as attributes in an entry or all attribute values of a given
   attribute, and to specify a common protection for them.

   The ACI Item syntax corresponds to the ACIItem ASN.1 type defined in
   [X501].  It is reproduced here for convenience:

   ACIItem ::= SEQUENCE {
       identificationTag   DirectoryString { ub-tag },
       precedence          Precedence,
       authenticationLevel AuthenticationLevel,
       itemOrUserFirst     CHOICE {
           itemFirst   [0] SEQUENCE {
               protectedItems  ProtectedItems,
               itemPermissions SET OF ItemPermission },
           userFirst   [1] SEQUENCE {
               userClasses     UserClasses,
               userPermissions SET OF UserPermission } } }

   Precedence ::= INTEGER (0..255)

   ProtectedItems ::= SEQUENCE {
       entry                   [0] NULL OPTIONAL,
       allUserAttributeTypes   [1] NULL OPTIONAL,
       attributeType           [2] SET SIZE (1..MAX) OF
                                       AttributeType OPTIONAL,
       allAttributeValues      [3] SET SIZE (1..MAX) OF
                                       AttributeType OPTIONAL,
       allUserAttributeTypesAndValues  [4] NULL OPTIONAL,
       attributeValue          [5] SET SIZE (1..MAX) OF
                                       AttributeTypeAndValue OPTIONAL,
       selfValue               [6] SET SIZE (1..MAX) OF
                                       AttributeType OPTIONAL,
       rangeOfValues           [7] Filter OPTIONAL,
       maxValueCount           [8] SET SIZE (1..MAX) OF
                                       MaxValueCount OPTIONAL,
       maxImmSub               [9] INTEGER OPTIONAL,
       restrictedBy           [10] SET SIZE (1..MAX) OF
                                       RestrictedValue OPTIONAL,
       contexts               [11] SET SIZE (1..MAX) OF
                                       ContextAssertion OPTIONAL,
       classes                [12] Refinement OPTIONAL }

   MaxValueCount ::= SEQUENCE {
       type        AttributeType,



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       maxCount    INTEGER }

   RestrictedValue ::= SEQUENCE {
       type        AttributeType,
       valuesIn    AttributeType }

   UserClasses ::= SEQUENCE {
       allUsers    [0] NULL OPTIONAL,
       thisEntry   [1] NULL OPTIONAL,
       name        [2] SET SIZE (1..MAX) OF NameAndOptionalUID OPTIONAL,
       userGroup   [3] SET SIZE (1..MAX) OF NameAndOptionalUID OPTIONAL,
           -- dn component shall be the name of an
           -- entry of GroupOfUniqueNames
       subtree     [4] SET SIZE (1..MAX) OF
                           SubtreeSpecification OPTIONAL }

   NameAndOptionalUID ::= SEQUENCE {
       dn      DistinguishedName,
       uid     UniqueIdentifier OPTIONAL }

   UniqueIdentifier ::= BIT STRING

   ItemPermission ::= SEQUENCE {
       precedence          Precedence OPTIONAL,
           -- defaults to precedence in ACIItem
       userClasses         UserClasses,
       grantsAndDenials    GrantsAndDenials }

   UserPermission ::= SEQUENCE {
       precedence Precedence OPTIONAL,
           -- defaults to precedence in ACIItem
       protectedItems ProtectedItems,
       grantsAndDenials GrantsAndDenials }

   AuthenticationLevel ::= CHOICE {
       basicLevels     SEQUENCE {
           level           ENUMERATED { none(0), simple(1), strong(2) },
           localQualifier  INTEGER OPTIONAL,
           signed          BOOLEAN DEFAULT FALSE },
       other           EXTERNAL }

   GrantsAndDenials ::= BIT STRING {
       -- permissions that may be used in conjunction
       -- with any component of ProtectedItems
       grantAdd             (0),
       denyAdd              (1),
       grantDiscloseOnError (2),
       denyDiscloseOnError  (3),



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       grantRead            (4),
       denyRead             (5),
       grantRemove          (6),
       denyRemove           (7),
       -- permissions that may be used only in conjunction
       -- with the entry component
       grantBrowse          (8),
       denyBrowse           (9),
       grantExport         (10),
       denyExport          (11),
       grantImport         (12),
       denyImport          (13),
       grantModify         (14),
       denyModify          (15),
       grantRename         (16),
       denyRename          (17),
       grantReturnDN       (18),
       denyReturnDN        (19),
       -- permissions that may be used in conjunction
       -- with any component, except entry, of ProtectedItems
       grantCompare        (20),
       denyCompare         (21),
       grantFilterMatch    (22),
       denyFilterMatch     (23),
       grantInvoke         (24),
       denyInvoke          (25) }

   AttributeTypeAndValue ::= SEQUENCE {
       type    ATTRIBUTE.&id ({SupportedAttributes}),
       value   ATTRIBUTE.&Type ({SupportedAttributes}{@type}) }

   The SubtreeSpecification and Refinement ASN.1 types are defined in
   [X501], and separately described in [SUBENTRY].

   The following sections describe the components of ACIItem.


5.2.1 Identification Tag

   identificationTag is used to identify a particular ACI item.  This is
   used to discriminate among individual ACI items for the purposes of
   protection and administration.


5.2.2 Precedence

   Precedence is used to control the relative order in which ACI items
   are considered during the course of making an access control decision



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   using the ACDF.  ACI items having higher precedence values prevail
   over others with lower precedence values, other factors being equal.
   Precedence values are integers and are compared as such.


5.2.3 Authentication Level

   AuthenticationLevel defines the minimum requestor authentication
   level required for this ACI item.  It has two forms:

   1) basicLevels: which indicates the level of authentication,
      optionally qualified by positive or negative integer
      localQualifier.

   2) other: an externally defined measure.

   When basicLevels is used, an AuthenticationLevel consisting of a
   level and optional localQualifier SHALL be assigned to the requestor
   by the directory server according to local policy.  For a requestor's
   authentication level to meet or exceed the minimum requirement, the
   requestor's level must meet or exceed that specified in the ACI item,
   and in addition the requestor's localQualifier must be arithmetically
   greater than or equal to that of the ACI item.  Strong authentication
   of the requestor is considered to exceed a requirement for simple or
   no authentication, and simple authentication exceeds a requirement
   for no authentication.  For access control purposes, the "simple"
   authentication level requires at least a password; the case of
   identification only, with no password supplied, is considered "none".
   If a localQualifier is not specified in the ACI item, then the
   requestor need not have a corresponding value (if such a value is
   present it is ignored).

   The signed component of basicLevels is ignored for LDAP.

   When other is used, an appropriate AuthenticationLevel shall be
   assigned to the requestor by the directory server according to local
   policy.  The form of this AuthenticationLevel and the method by which
   it is compared with the AuthenticationLevel in the ACI is a local
   matter.

   An authentication level associated with an explicit grant indicates
   the minimum level to which a requestor shall be authenticated in
   order to be granted access.

   An authentication level associated with an explicit deny indicates
   the minimum level to which a requestor shall be authenticated in
   order not to be denied access.  For example, an ACI item that denies
   access to a particular user class and requires strong authentication



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   will deny access to all requestors who cannot prove, by means of a
   strongly authenticated identity, that they are not in that user
   class.

   The directory server may base authentication level on factors other
   than values received in protocol exchanges.


5.2.4 itemFirst and userFirst Components

   Each ACI item contains a choice of itemFirst or userFirst.  The
   choice allows grouping of permissions depending on whether they are
   most conveniently grouped by user classes or by protected items.  The
   itemFirst and userFirst components are equivalent in the sense that
   they capture the same access control information; however, they
   organize that information differently.  The choice between them is
   based on administrative convenience.  The subcomponents of itemFirst
   and userFirst are described below.

   a) ProtectedItems defines the items to which the specified access
      controls apply.  It is defined as a set selected from the
      following:

      - entry means the entry contents as a whole.  It does not
        necessarily include the information in these entries.  This
        element SHALL be ignored if the classes component is present,
        since this latter element selects protected entries on the basis
        of their object class.

      - allUserAttributeTypes means all user attribute type information
        associated with the entry, but not values associated with those
        attributes.

      - allUserAttributeTypesAndValues means all user attribute
        information associated with the entry, including all values of
        all user attributes.

        The allUserAttributeTypes and allUserAttributeTypesAndValues
        components do not include operational attributes, which MUST be
        specified on a per attribute basis, using attributeType,
        allAttributeValues or attributeValue.

      - attributeType means attribute type information pertaining to
        specific attributes but not values associated with the type.

      - allAttributeValues means all attribute value information
        pertaining to specific attributes.




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      - attributeValue means specific values of specific attribute
        types.

      - selfValue means the attribute values of the specified attribute
        types that match the distinguished name (and unique identifier)
        of the requestor.  It can only apply in the specific case where
        the attribute specified is of DN syntax
        (1.3.6.1.4.1.1466.115.121.1.12) or Name And Optional UID syntax
        (1.3.6.1.4.1.1466.115.121.1.34) [RFC2252].

      - rangeOfValues means any attribute value which matches the
        specified filter, i.e. for which the specified filter evaluated
        on that attribute value would return TRUE.  The filter is not
        evaluated on any entries in the DIB, rather it is evaluated
        using the semantics defined in 7.8 of [X511], operating on a
        fictitious entry that contains only the single attribute value
        which is the protected item.  Note that the filter is an X.500
        search Filter.  It has a different syntax from the LDAP search
        Filter, but the same semantics.

      The following items provide constraints that may disable the
      granting of certain permissions to protected items in the same
      value of ProtectedItems:

      - maxValueCount restricts the maximum number of attribute values
        allowed for a specified attribute type.  It is examined if the
        protected item is an attribute value of the specified type and
        the permission sought is Add.  Values of that attribute in the
        entry are counted, without regard to attribute options and
        access control, as though the operation which is attempting to
        add the values is successful.  If the number of values in the
        attribute exceeds maxCount, the ACI item is treated as not
        granting Add permission.

      - maxImmSub restricts the maximum number of immediate subordinates
        of the superior entry to an entry being added or imported.  It
        is examined if the protected item is an entry, the permission
        sought is Add or Import, and the immediate superior entry is in
        the same server as the entry being added or imported.  Immediate
        subordinates of the superior entry are counted, without regard
        to access control, as though the entry addition or importing is
        successful.  If the number of subordinates exceeds maxImmSub,
        the ACI item is treated as not granting Add or Import
        permission.

      - restrictedBy restricts values added to the attribute type to
        being values that are already present in the same entry as
        values of the attribute identified by the valuesIn component.



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        It is examined if the protected item is an attribute value of
        the specified type and the permission sought is Add.  Values of
        the valuesIn attribute are checked, without regard to attribute
        options and access control, as though the operation which adds
        the values is successful.  If the value to be added is not
        present in valuesIn the ACI item is treated as not granting Add
        permission.

      - contexts is not used in this version of the LDAP profile for
        Basic Access Control.

      - classes means the contents of entries that have object class
        values that satisfy the predicate defined by Refinement (see
        [SUBENTRY]).

   b) UserClasses defines a set of zero or more users the permissions
      apply to.  The set of users is selected from the following:

      - allUsers means every directory user (with possible requirements
        for AuthenticationLevel).

      - thisEntry means the user with the same distinguished name as the
        entry being accessed.

      - name is the set of users with the specified distinguished names
        (each with an optional unique identifier).

      - userGroup is the set of users who are members of the groups
        (i.e. groupOfNames or groupOfUniqueNames entries [RFC2256])
        identified by the specified distinguished names (each with an
        optional unique identifier).  Members of a group of unique names
        are treated as individual user distinguished names, and not as
        the names of other groups of unique names.  How group membership
        is determined is described in 5.2.5.

      - subtree is the set of users whose distinguished names fall
        within the scope of the unrefined subtrees (specificationFilter
        components SHOULD NOT be used - they SHALL be ignored if
        present).

   c) SubtreeSpecification is used to specify a subtree relative to the
      root DSE, and is not constrained by administrative areas.  The
      specificationFilter component SHOULD NOT be used.  It SHALL be
      ignored if present.

      A subtree refinement is not allowed because membership in a
      subtree whose specification includes only base and/or a
      ChopSpecification can be evaluated in isolation, whereas



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      membership in a subtree definition using specificationFilter can
      only be evaluated by obtaining information from the user's entry,
      which is potentially in another directory server.  Basic Access
      Control is designed to avoid remote operations in the course of
      making an access control decision.

   d) ItemPermission contains a collection of users and their
      permissions with respect to ProtectedItems within an itemFirst
      specification.  The permissions are specified in grantsAndDenials
      as discussed in item f).  Each of the permissions specified in
      grantsAndDenials is considered to have the precedence level
      specified in precedence for the purpose of the ACDF.  If
      precedence is omitted within ItemPermission, then precedence is
      taken from the precedence specified for ACIItem.

   e) UserPermission contains a collection of protected items and the
      associated permissions with respect to userClasses within a
      userFirst specification.  The associated permissions are specified
      in grantsAndDenials as discussed in item f).  Each of the
      permissions specified in grantsAndDenials is considered to have
      the precedence level specified in precedence for the purpose of
      the ACDF.  If precedence is omitted within UserPermission, the
      precedence is taken from the precedence specified for ACIItem.

   f) GrantsAndDenials specify the access rights that are granted or
      denied by the ACI item.

   g) UniqueIdentifier may be used by the authentication mechanism to
      distinguish between instances of distinguished name reuse.  If
      this component is present, then for a requestor's name to match
      the UserClasses of an ACIItem that grants permissions, in addition
      to the requirement that the requestor's distinguished name match
      the specified distinguished name, the authentication of the
      requestor shall yield an associated unique identifier, and that
      value shall match for equality with the specified value.


5.2.5 Determining Group Membership

   Determining whether a given requestor is a group member requires
   checking two criteria.  The determination may also be constrained if
   the group definition is not known locally.  The criteria for
   membership and the treatment of non-local groups are discussed below.

   a) A directory server is NOT REQUIRED to perform a remote operation
      to determine whether the requestor belongs to a particular group
      for the purposes of Basic Access Control.  If membership in the
      group cannot be evaluated, the server shall assume that the



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      requestor does not belong to the group if the ACI item grants the
      permission sought, and does belong to the group if it denies the
      permission sought.

      Access control administrators should beware of basing access
      controls on membership of non-locally available groups or groups
      which are available only through replication (and which may,
      therefore, be out of date).

   b) In order to determine whether the requestor is a member of a
      userGroup user class, the following criteria apply:

      - The entry named by the userGroup specification is an instance of
        the object class groupOfNames or groupOfUniqueNames.

      - The name of the requestor is a value of the member or
        uniqueMember attribute of that entry.

      Values of the member or uniqueMember attribute that do not match
      the name of the requestor are ignored, even if they represent the
      names of groups of which the originator could be found to be a
      member.  Hence, nested groups are not supported when evaluating
      access controls.


5.3 ACI Operational Attributes

   ACI is stored as values of operational attributes of entries and
   subentries.  The operational attributes are multi-valued, which
   allows ACI to be represented as a set of ACI items.


5.3.1 Prescriptive ACI

   The prescriptiveACI attribute is defined as an operational attribute
   of an access control subentry.  It contains prescriptive ACI
   applicable to entries within that subentry's scope.

   The LDAP description [RFC2252] for the prescriptiveACI operational
   attribute is:

      ( 2.5.24.4 NAME 'prescriptiveACI'
          EQUALITY directoryStringFirstComponentMatch
          SYNTAX 1.3.6.1.4.1.1466.115.121.1.1
          USAGE directoryOperation )

   The directoryStringFirstComponentMatch matching rule is described in
   [SCHEMA].



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   Prescriptive ACI within the subentries of a particular administrative
   point never applies to the same or any other subentry of that
   administrative point, but can be applicable to the subentries of
   subordinate administrative points.

   Note that prescriptiveACI attributes are not collective attributes.
   Although the values of a prescriptiveACI attribute contribute to
   access control decisions for each entry within the scope of the
   subentry that holds the attribute, the prescriptiveACI attribute does
   not appear as part of those entries.


5.3.2 Entry ACI

   The entryACI attribute is defined as an operational attribute of an
   entry or subentry (not just access control subentries).  It contains
   entry ACI applicable to the entry or subentry in which it appears,
   and that (sub)entry's contents.

   The LDAP description [RFC2252] for the entryACI operational attribute
   is:

      ( 2.5.24.5 NAME 'entryACI'
          EQUALITY directoryStringFirstComponentMatch
          SYNTAX 1.3.6.1.4.1.1466.115.121.1.1
          USAGE directoryOperation )


5.3.3 Subentry ACI

   The subentryACI attribute is defined as an operational attribute of
   administrative entries [ADMIN] (for any aspect of administration).
   It contains subentry ACI that applies to each of the subentries of
   the administrative entry in which it appears.  Only administrative
   entries are permitted to contain a subentryACI attribute.

   The LDAP description [RFC2252] for the subentryACI operational
   attribute is:

      ( 2.5.24.6 NAME 'subentryACI'
          EQUALITY directoryStringFirstComponentMatch
          SYNTAX 1.3.6.1.4.1.1466.115.121.1.1
          USAGE directoryOperation )


5.3.4 Protecting the ACI

   ACI operational attributes are subject to the same protection



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   mechanisms as other attributes.

   The identificationTag provides an identifier for each ACI item.  This
   tag can be used to remove a specific ACI item value, or to protect it
   by prescriptive ACI, entry ACI or subentry ACI.  Directory rules
   ensure that only one ACI item per access control operational
   attribute possesses any specific identificationTag value.

   The creation of subentries for an administrative entry may be
   controlled by means of the subentryACI operational attribute in the
   administrative entry.  The right to create prescriptive access
   controls may also be governed directly by security policy; this
   provision is required to create access controls in new autonomous
   administrative areas [ADMIN].


5.4 Access Control Decision Points for LDAP Operations

   Each LDAP operation involves making a series of access control
   decisions on the various protected items that the operation accesses.

   For some operations (e.g. the Modify operation), each such access
   control decision must grant access for the operation to succeed; if
   access is denied to any protected item, the whole operation fails.
   For other operations (e.g. the Search operation), protected items to
   which access is denied are simply omitted from the operation result
   and processing continues.

   If the requested access is denied, further access control decisions
   may be needed to determine if the user has DiscloseOnError
   permissions to the protected item.  Only if DiscloseOnError
   permission is granted may the server respond with an error that
   reveals the existence of the protected item.  In all other cases, the
   server MUST act so as to conceal the existence of the protected item.

   The permissions required to access each protected item, are specified
   for each operation in the following sections.  The algorithm by which
   a permission is determined to be granted or not granted is specified
   in Section 5.5.


5.4.1 Common Elements of Procedure

   This section defines the elements of procedure that are common to all
   LDAP operations when Basic Access Control is in effect.


5.4.1.1 Alias Dereferencing



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   If, in the process of locating a target object entry (nominated in an
   LDAP request), alias dereferencing is required, no specific
   permissions are necessary for alias dereferencing to take place.
   However, if alias dereferencing would result in a referral being
   returned, the following sequence of access controls applies.

   1) Read permission is required to the alias entry.  If permission is
      not granted, the operation fails in accordance to the procedure
      described in 5.4.1.3.

   2) Read permission is required to the aliasedEntryName attribute and
      to the single value that it contains.  If permission is not
      granted, the operation fails and the resultCode
      aliasDereferencingProblem SHALL be returned.  The matchedDN field
      of the LDAPResult SHALL contain the name of the alias entry.

   In addition to the access controls described above, security policy
   may prevent the disclosure of knowledge of other servers which would
   otherwise be conveyed in a referral.  If such a policy is in effect
   the resultCode insufficientAccessRights SHALL be returned.


5.4.1.2 Return of Names in Errors

   Certain LDAP result codes, i.e. noSuchObject, aliasProblem,
   invalidDNSyntax and aliasDereferencingProblem, provide the name of an
   entry in the matchedDN field of an LDAPResult.  The DN of an entry
   SHALL only be provided in the matchedDN field if DiscloseOnError
   permission is granted to that entry, otherwise, the matchedDN field
   of the LDAPResult SHALL either contain the name of the next superior
   entry to which DiscloseOnError permission is granted, or, if
   DiscloseOnError permission is not granted to any superior entry, the
   name of the root DSE (i.e. a zero-length LDAPDN).


5.4.1.3 Non-disclosure of the Existence of an Entry

   If, while performing an LDAP operation, the necessary entry level
   permission is not granted to the specified target object entry - e.g.
   the entry to be modified - the operation fails; if DiscloseOnError
   permission is granted to the target entry, the resultCode
   insufficientAccessRights SHALL be returned, otherwise, the resultCode
   noSuchObject SHALL be returned.  The matchedDN field of the
   LDAPResult SHALL either contain the name of the next superior entry
   to which DiscloseOnError permission is granted, or, if
   DiscloseOnError permission is not granted to any superior entry, the
   name of the root DSE (i.e. a zero-length LDAPDN).




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   Additionally, whenever the server detects an operational error
   (including a referral resultCode), it shall ensure that in returning
   that error it does not compromise the existence of the named target
   entry and any of its superiors.  For example, before returning a
   resultCode of timeLimitExceeded or notAllowedOnNonLeaf, the server
   verifies that DiscloseOnError permission is granted to the target
   entry.  If it is not, the procedure described in the paragraph above
   SHALL be followed.


5.4.2 Compare Operation Decision Points

   The following sequence of access controls applies for an entry being
   compared.

   1) Read permission for the entry to be compared is required.  If
      permission is not granted, the operation fails in accordance with
      5.4.1.3.

   2) Compare permission for the attribute to be compared is required.
      If permission is not granted, the operation fails: if
      DiscloseOnError permission is granted to the attribute being
      compared, a resultCode of insufficientAccessRight SHALL be
      returned, otherwise, the resultCode noSuchAttribute SHALL be
      returned.

   3) If there exists a value within the attribute being compared that
      matches the purported argument and for which Compare permission is
      granted, the operation returns the resultCode compareTrue,
      otherwise the operation returns the resultCode compareFalse.


5.4.3 Search Operation Decision Points

   The following sequence of access controls applies for a portion of
   the DIT being searched.

   1) No specific permission is required to the entry identified by the
      baseObject argument in order to initiate a search.  However, if
      the baseObject is within the scope of the SearchArgument (i.e.
      when the subset argument specifies baseObject or wholeSubtree) the
      access controls specified in 2) through 5) will apply.

   2) Browse or Read permission is required for the single entry within
      the scope of a baseObject search.  An entry for which neither of
      these permissions is granted is ignored.

      This differs from the X.500 DAP Search operation where the Browse



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      permission alone is required.  An entry with Read permission but
      not Browse permission cannot be searched but can still be examined
      with an X.500 DAP Read operation.  LDAP relies on baseObject
      search operations to provide the functionality of the DAP Read
      operation.  Accepting Read permission for the target entry in a
      baseObject search gives an LDAP baseObject search the same access
      rights to the entry as the DAP Read operation.

   3) Browse permission is required for an entry within the scope of a
      singleLevel or wholeSubtree search to be a candidate for
      consideration.  Entries for which this permission is not granted
      are ignored.

   4) The filter argument is applied to each entry left to be considered
      after taking 2) and 3) into account, in accordance with the
      following:

      a) For a present Filter item, if there exists an attribute value
         such that the attribute type of the value (possibly a subtype
         of the attribute type in the FilterItem) satisfies the Filter
         item and FilterMatch permission is granted for the value and
         for the attribute type then the FilterItem evaluates to TRUE,
         otherwise, it evaluates to FALSE.

         If a directory server does not support True/False filters
         [FILTER] on LDAP searches, or if directory clients do not
         exploit this capability, then access control administrators
         SHOULD grant FilterMatch permission for the objectClass
         attribute over entries where Read permission is also granted so
         that an LDAP baseObject search with a filter testing for the
         presence of the objectClass attribute will have the same access
         rights to the target entry as the DAP Read operation.  An LDAP
         baseObject search with a True filter does not require
         FilterMatch permission for any particular attribute type.

      b) For an equalityMatch, substrings, greaterOrEqual, lessOrEqual,
         approxMatch or extensibleMatch Filter item, if there exists an
         attribute value such that the value satisfies the Filter item
         and FilterMatch permission is granted for the value and for its
         attribute type (possibly a subtype of the attribute type in the
         FilterItem) then the FilterItem evaluates to TRUE, otherwise,
         it evaluates to FALSE.

   Once the access controls defined in 2) through 4) have been applied,
   an entry is either selected or discarded.

   5) For each selected entry the information returned is as follows:




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      a) ReturnDN permission for an entry is required in order to return
         its distinguished name in a SearchResultEntry response.  If
         this permission is not granted, the server SHALL either, return
         the name of a valid alias to the entry, or, omit the entry from
         the search result.

         If the base entry of the search was located using an alias,
         then that alias is known to be a valid alias.  Otherwise, how
         it is ensured that the alias is valid is outside the scope of
         this specification.

         Where a server has a choice of alias names available to it for
         return, it is RECOMMENDED that where possible it choose the
         same alias name for repeated requests by the same client, in
         order to provide a consistent service.

      b) If the typesOnly field of the SearchRequest is TRUE then, for
         each attribute type that is to be returned, Read permission for
         the attribute type and Read permission for at least one value
         of the attribute is required.  If permission is not granted,
         the attribute type is omitted from the attribute list in the
         SearchResultEntry.  If as a consequence of applying these
         controls no attribute type information is selected, the
         SearchResultEntry is returned but no attribute type information
         is conveyed with it (i.e. the attribute list is empty).

      c) If the typesOnly field of the SearchRequest is FALSE then Read
         permission is required for each attribute type and for each
         attribute value that is to be returned.  If permission to an
         attribute type is not granted, the attribute is omitted from
         the SearchResultEntry.  If permission to an attribute value is
         not granted, the value is omitted from its corresponding
         attribute.  If all values of an attribute are omitted then the
         attribute type is omitted from the attribute list in the
         SearchResultEntry.  If as a consequence of applying these
         controls no attribute information is selected, the
         SearchResultEntry is returned but no attribute information is
         conveyed with it (i.e. the attribute list is empty).

   6) If as a consequence of applying the above controls to the entire
      scoped subtree the search result contains no entries (excluding
      any SearchResultReferences) and if DiscloseOnError permission is
      not granted to the entry identified by the baseObject argument,
      the operation fails and the resultCode noSuchObject SHALL be
      returned.  The matchedDN field of the LDAPResult SHALL either
      contain the name of the next superior entry to which
      DiscloseOnError permission is granted, or the name of the root DSE
      (i.e. a zero-length LDAPDN).  Otherwise, the operation succeeds



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      but no subordinate information is conveyed with it.

   Security policy may prevent the disclosure of knowledge of other
   servers which would otherwise be conveyed as SearchResultReferences.
   If such a policy is in effect SearchResultReferences are omitted from
   the search result.

   No specific permissions are necessary to allow alias dereferencing to
   take place in the course of a search operation.  However, for each
   alias entry encountered, if alias dereferencing would result in a
   SearchResultReference being returned, the following access controls
   apply: Read permission is required to the alias entry, the
   aliasedEntryName attribute and to the single value that it contains.
   If any of these permissions is not granted, the SearchResultReference
   SHALL be omitted from the search result.


5.4.4 Add Operation Decision Points

   The following sequence of access controls apply for an entry being
   added.

   1) No specific permission is required for the immediate superior of
      the entry identified by the entry field of the AddRequest.

   2) If an entry already exists with a distinguished name equal to the
      entry field the operation fails; if DiscloseOnError or Add
      permission is granted to the existing entry, the resultCode
      entryAlreadyExists SHALL be returned, otherwise, the procedure
      described in 5.4.1.3 is followed with respect to the entry being
      added.

   3) Add permission is required for the new entry being added.  If this
      permission is not granted, the operation fails; the procedure
      described in 5.4.1.3 is followed with respect to the entry being
      added.

      The Add permission is provided as prescriptive ACI when attempting
      to add an entry and as prescriptive ACI or subentry ACI when
      attempting to add a subentry.  Any values of the entryACI
      attribute in the entry being added SHALL be ignored.

   4) Add permission is required for each attribute type and for each
      value that is to be added.  If any permission is absent, the
      operation fails and the resultCode insufficientAccessRights SHALL
      be returned.





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5.4.5 Delete Operation Decision Points

   The following sequence of access controls apply for an entry being
   removed.

   1) Remove permission is required for the entry being removed.  If
      this permission is not granted, the operation fails in accordance
      with 5.4.1.3.

   2) No specific permissions are required for any of the attributes and
      attribute values present within the entry being removed.


5.4.6 Modify Operation Decision Points

   The following sequence of access controls apply for an entry being
   modified.

   1) Modify permission is required for the entry being modified.  If
      this permission is not granted, the operation fails in accordance
      with 5.4.1.3.

   2) For each of the specified modification arguments applied in
      sequence, the following permissions are required:

      a) Add permission is required for each of the attribute values
         specified in an add modification.  If the attribute does not
         currently exist then Add permission for the attribute type is
         also required.  If these permissions are not granted, or any of
         the attribute values already exist, the operation fails; if an
         attribute value already exists and DiscloseOnError or Add is
         granted to that attribute value, the resultCode
         attributeOrValueExists SHALL be returned, otherwise, the
         resultCode insufficientAccessRights SHALL be returned.

      b) Remove permission is required for the attribute type specified
         in a delete modification with no listed attribute values.  If
         this permission is not granted, the operation fails; if
         DiscloseOnError permission is granted to the attribute being
         removed and the attribute exists, the resultCode
         insufficientAccessRights SHALL be returned, otherwise, the
         resultCode noSuchAttribute SHALL be returned.

         No specific permissions are required for any of the attribute
         values present within the attribute being removed.

      c) Remove permission is required for each of the values in a
         delete modification with listed attribute values.  If all



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         current values of the attribute are specified to be removed
         (which causes the attribute itself to be removed), then Remove
         permission for the attribute type is also required.  If these
         permissions are not granted, the operation fails; if
         DiscloseOnError permission is granted to any of the attribute
         values being removed, the resultCode insufficientAccessRights
         SHALL be returned, otherwise, the resultCode noSuchAttribute
         SHALL be returned.

      d) Remove and Add permission is required for the attribute type,
         and Add permission is required for each of the specified
         attribute values, in a replace modification.  If these
         permissions are not granted the operation fails and the
         resultCode insufficientAccessRights SHALL be returned.

         No specific permissions are required to remove any existing
         attribute values of the attribute being replaced.


5.4.7 Modify DN Operation Decision Points

   The following sequence of access controls apply for an entry having
   its DN modified.

   1) If the effect of the operation is to change the RDN of the entry
      then Rename permission (determined with respect to its original
      name) is required for the entry.  If this permission is not
      granted, the operation fails; the procedure described in 5.4.1.3
      is followed with respect to the entry being renamed (considered
      with its original name).

      No additional permissions are required even if, as a result of
      modifying the RDN of the entry, a new distinguished value needs to
      be added, or an old one removed.  No specific permissions are
      required for the subordinates of the renamed entry.

   2) If the effect of the operation is to move an entry to a new
      superior in the DIT then Export permission (determined with
      respect to its original name) and Import permission (determined
      with respect to its new name) are required for the entry.  If
      either of these permissions is not granted, the operation fails;
      the procedure described in 5.4.1.3 is followed with respect to the
      entry being moved (considered with its original name).

      The Import permission is provided as prescriptive ACI when
      attempting to move an entry and as prescriptive ACI or subentry
      ACI when attempting to move a subentry.  Any values of the
      entryACI attribute in the entry or subentry being moved SHALL be



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      ignored.

      No specific permissions are required for the subordinates of the
      moved entry.

   Note that a single Modify DN Operation may simultaneously rename and
   move an entry.


5.5 Access Control Decision Function

   This section describes how ACI items are processed in order to decide
   whether to grant or deny a particular requestor a specified
   permission to a given protected item.

   Section 5.5.1 describes the inputs to the ACDF.  Sections 5.5.2
   through 5.5.4 describe the steps in the ACDF.  The output is a
   decision to grant or deny access to the protected item.


5.5.1 Inputs

   For each invocation of the ACDF, the inputs are:

   a) the requestor's Distinguished Name, unique identifier, and
      authentication level, or as many of these as are available;

   b) the protected item (an entry, an attribute, or an attribute value)
      being considered at the current decision point for which the ACDF
      was invoked;

   c) the requested permission specified for the current decision point;

   d) the ACI items applicable to the entry containing (or which is) the
      protected item.

   In addition, if the ACI items include any of the protected item
   constraints described in 5.2.1.4, the whole entry and the number of
   immediate subordinates of its superior entry may also be required as
   inputs.


5.5.2 Tuples

   For each ACI item, expand the item into a set of tuples, one tuple
   for each element of the itemPermissions and userPermissions sets,
   containing the following elements:




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      ( userClasses, authenticationLevel, protectedItems,
         grantsAndDenials, precedence )

   Collect all tuples from all ACI items into a single set.

   For any tuple whose grantsAndDenials specify both grants and denials,
   replace the tuple with two tuples - one specifying only grants and
   the other specifying only denials.


5.5.3 Discarding Irrelevant Tuples

   Perform the following steps to discard all irrelevant tuples:

   1) Discard all tuples that do not include the requestor in the
      tuple's userClasses as follows:

      a) For tuples that grant access, discard all tuples that do not
         include the requestor's identity in the tuples's userClasses
         element, taking into account UniqueIdentifier elements if
         relevant.  Where a tuple's userClasses specifies a
         UniqueIdentifier, a matching value shall be present in the
         requestor's identity if the tuple is not to be discarded.
         Discard tuples that specify an authentication level higher than
         that associated with the requestor.

      b) For tuples that deny access, retain all tuples that include the
         requestor in the tuple's userClasses element, taking into
         account uniqueIdentifier elements if relevant.  Also retain all
         tuples that deny access and which specify an authentication
         level higher than that associated with the requestor.  This
         reflects the fact that the requestor has not adequately proved
         non-membership in the user class for which the denial is
         specified.  All other tuples that deny access are discarded.

   2) Discard all tuples that do not include the protected item in
      protectedItems.

   3) Examine all tuples that include maxValueCount, maxImmSub or
      restrictedBy.  Discard all such tuples which grant access and
      which do not satisfy any of these constraints.

   4) Discard all tuples that do not include the requested permission as
      one of the set bits in grantsAndDenials.

   The order in which tuples are discarded does not change the output of
   the ACDF.




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5.5.4 Highest Precedence and Specificity

   Perform the following steps to select those tuples of highest
   precedence and specificity:

   1) Discard all tuples having a precedence less than the highest
      precedence among the remaining tuples.

   2) If more than one tuple remains, choose the tuples with the most
      specific user class.  If there are any tuples matching the
      requestor with UserClasses element name or thisEntry, discard all
      other tuples.  Otherwise if there are any tuples matching
      UserGroup, discard all other tuples.  Otherwise if there are any
      tuples matching subtree, discard all other tuples.

   3) If more than one tuple remains, choose the tuples with the most
      specific protected item.  If the protected item is an attribute
      and there are tuples that specify the attribute type explicitly,
      discard all other tuples.  If the protected item is an attribute
      value, and there are tuples that specify the attribute value
      explicitly, discard all other tuples.  A protected item which is a
      rangeOfValues is to be treated as specifying an attribute value
      explicitly.

   Grant access if and only if one or more tuples remain and all grant
   access.  Otherwise deny access.


6. Simplified Access Control

   This section describes the functionality of the Simplified Access
   Control scheme.  It provides a subset of the functionality found in
   Basic Access Control.

   When Simplified Access Control is used, the accessControlScheme
   operational attribute [ACA] SHALL have the value
   simplified-access-control (2.5.28.2).

   The functionality of Simplified Access Control is the same as Basic
   Access Control except that:

   1) Access control decisions shall be made only on the basis of values
      of prescriptiveACI and subentryACI operational attributes.  Values
      of the entryACI attribute, if present, SHALL NOT be used to make
      access control decisions.

   2) Access Control Inner Areas are not used.  Values of
      prescriptiveACI attributes appearing in subentries of ACIPs SHALL



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      NOT be used to make access control decisions.

   All other provisions SHALL be as defined for Basic Access Control.


7. Security Considerations

   Access control administrators should beware of basing access controls
   on membership of non-locally available groups or groups which are
   available only through replication (and which may, therefore, be out
   of date).

   A particular DSA might not have the ACI governing any data that it
   caches.  Administrators should be aware that a directory server with
   the capability of caching may pose a significant security risk to
   other directory servers, in that it may reveal information to
   unauthorized users.


8. Acknowledgements

   This document is derived from, and duplicates substantial portions
   of, Section 8 of [X501], and selected extracts from [X511].


9. IANA Considerations

   The Internet Assigned Numbers Authority (IANA) is requested to update
   the LDAP descriptors registry as indicated by the following
   templates:

      Subject: Request for LDAP Descriptor Registration
      Descriptor (short name): basic-access-control
      Object Identifier: 2.5.28.1
      Person & email address to contact for further information:
        Steven Legg <steven.legg@adacel.com.au>
      Usage: other (access control scheme)
      Specification: RFC XXXX
      Author/Change Controller: IESG

      Subject: Request for LDAP Descriptor Registration
      Descriptor (short name): simplified-access-control
      Object Identifier: 2.5.28.2
      Person & email address to contact for further information:
        Steven Legg <steven.legg@adacel.com.au>
      Usage: other (access control scheme)
      Specification: RFC XXXX
      Author/Change Controller: IESG



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      Subject: Request for LDAP Descriptor Registration
      Descriptor (short name): prescriptiveACI
      Object Identifier: 2.5.24.4
      Person & email address to contact for further information:
        Steven Legg <steven.legg@adacel.com.au>
      Usage: attribute type
      Specification: RFC XXXX
      Author/Change Controller: IESG

      Subject: Request for LDAP Descriptor Registration
      Descriptor (short name): entryACI
      Object Identifier: 2.5.24.5
      Person & email address to contact for further information:
        Steven Legg <steven.legg@adacel.com.au>
      Usage: attribute type
      Specification: RFC XXXX
      Author/Change Controller: IESG

      Subject: Request for LDAP Descriptor Registration
      Descriptor (short name): subentryACI
      Object Identifier: 2.5.24.6
      Person & email address to contact for further information:
        Steven Legg <steven.legg@adacel.com.au>
      Usage: attribute type
      Specification: RFC XXXX
      Author/Change Controller: IESG


10. Normative References

   [RFC2119]  Bradner, S., "Key words for use in RFCs to Indicate
              Requirement Levels", BCP 14, RFC 2119, March 1997.

   [RFC2251]  Wahl, M., Howes, T. and S. Kille, "Lightweight Directory
              Access Protocol (v3)", RFC 2251, December 1997.

   [RFC2252]  Wahl, M., Coulbeck, A., Howes, T. and S. Kille,
              "Lightweight Directory Access Protocol (v3): Attribute
              Syntax Definitions", RFC 2252, December 1997.

   [RFC2256]  Wahl, M., "A Summary of the X.500(96) User Schema for use
              with LDAPv3", RFC 2256, December 1997.

   [RFC3377]  Hodges, J. and R. Morgan, "Lightweight Directory Access
              Protocol (v3): Technical Specification", RFC 3377,
              September 2002.

   [GSER]     Legg, S., "Generic String Encoding Rules for ASN.1 Types",



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              draft-legg-ldap-gser-xx.txt, a work in progress, October
              2002.

   [SUBENTRY] Zeilenga, K. and S. Legg, "Subentries in LDAP",
              draft-zeilenga-ldap-subentry-xx.txt, a work in progress,
              August 2002.

   [COLLECT]  Zeilenga, K., "Collective Attributes in LDAP",
              draft-zeilenga-ldap-collective-xx.txt, a work in progress,
              August 2002.

   [ADMIN]    Legg, S., "Directory Administrative Model in LDAP",
              draft-legg-ldap-admin-xx.txt, a work in progress, February
              2003.

   [ACA]      Legg, S., "Access Control Administration in LDAP",
              draft-legg-ldap-acm-admin-xx.txt, a work in progress,
              February 2003.

   [SCHEMA]   Zeilenga, K., "LDAPv3: A Collection of User Schema",
              draft-zeilenga-ldap-user-schema-xx.txt, a work in
              progress, May 2002.

   [FILTER]   Zeilenga, K., "LDAP Absolute True/False Filters",
              draft-zeilenga-ldap-t-f-xx.txt, a work in progress,
              November 2002.

   [X680]     ITU-T Recommendation X.680 (1997) | ISO/IEC 8824-1:1998
              Information Technology - Abstract Syntax Notation One
              (ASN.1): Specification of basic notation


11. Informative References

   [RFC2234]  Crocker, D. and P. Overell, "Augmented BNF for Syntax
              Specifications: ABNF", RFC 2234, November 1997.

   [GCE]      Legg, S., "Common Elements of GSER Encodings",
              draft-legg-ldap-gser-abnf-xx.txt, a work in progress,
              October 2002.

   [X501]     ITU-T Recommendation X.501 (02/2001), Information
              technology - Open Systems Interconnection - The Directory:
              Models

   [X511]     ITU-T Recommendation X.511 (02/2001), Information
              technology - Open Systems Interconnection - The Directory:
              Abstract service definition



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12. Copyright Notice

      Copyright (C) The Internet Society (2003). All Rights Reserved.

   This document and translations of it may be copied and furnished to
   others, and derivative works that comment on or otherwise explain it
   or assist in its implementation may be prepared, copied, published
   and distributed, in whole or in part, without restriction of any
   kind, provided that the above copyright notice and this paragraph are
   included on all such copies and derivative works.  However, this
   document itself may not be modified in any way, such as by removing
   the copyright notice or references to the Internet Society or other
   Internet organizations, except as needed for the purpose of
   developing Internet standards in which case the procedures for
   copyrights defined in the Internet Standards process must be
   followed, or as required to translate it into languages other than
   English.

   The limited permissions granted above are perpetual and will not be
   revoked by the Internet Society or its successors or assigns.

   This document and the information contained herein is provided on an
   "AS IS" basis and THE INTERNET SOCIETY AND THE INTERNET ENGINEERING
   TASK FORCE DISCLAIMS ALL WARRANTIES, EXPRESS OR IMPLIED, INCLUDING
   BUT NOT LIMITED TO ANY WARRANTY THAT THE USE OF THE INFORMATION
   HEREIN WILL NOT INFRINGE ANY RIGHTS OR ANY IMPLIED WARRANTIES OF
   MERCHANTABILITY OR FITNESS FOR A PARTICULAR PURPOSE.


13. Author's Address

   Steven Legg
   Adacel Technologies Ltd.
   250 Bay Street
   Brighton, Victoria 3186
   AUSTRALIA

   Phone: +61 3 8530 7710
     Fax: +61 3 8530 7888
   EMail: steven.legg@adacel.com.au


Appendix A. LDAP Specific Encoding for the ACI Item Syntax

   This appendix is non-normative.

   The LDAP-specific encoding for the ACI Item syntax is specified by
   the Generic String Encoding Rules in [GSER].  The ABNF [RFC2234] in



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   this appendix for this syntax is provided only as a convenience and
   is equivalent to the encoding specified by the application of [GSER].
   Since the ACI Item ASN.1 type may be extended in future editions of
   [X501], the provided ABNF should be regarded as a snapshot in time.
   The LDAP-specific encoding for any extension to the ACI Item ASN.1
   type can be determined from [GSER].

   In the event that there is a discrepancy between this ABNF and the
   encoding determined by [GSER], [GSER] is to be taken as definitive.

   ACIItem = "{" sp aci-identificationTag ","
                 sp aci-precedence ","
                 sp aci-authenticationLevel ","
                 sp aci-itemOrUserFirst
                 sp "}"

   aci-identificationTag   = id-identificationTag   msp
                                DirectoryString
   aci-precedence          = id-precedence          msp Precedence
   aci-authenticationLevel = id-authenticationLevel msp
                                AuthenticationLevel
   aci-itemOrUserFirst     = id-itemOrUserFirst     msp
                                ItemOrUserFirst
   id-identificationTag    = %x69.64.65.6E.74.69.66.69.63.61.74.69.6F
                                %x6E.54.61.67 ; "identificationTag"
   id-precedence           = %x70.72.65.63.65.64.65.6E.63.65
                                ; "precedence"
   id-authenticationLevel  = %x61.75.74.68.65.6E.74.69.63.61.74.69.6F
                                %x6E.4C.65.76.65.6C
                                ; "authenticationLevel"
   id-itemOrUserFirst      = %x69.74.65.6D.4F.72.55.73.65.72.46.69.72
                                %x73.74 ; "itemOrUserFirst"

   Precedence = INTEGER-0-MAX ; MUST be less than 256

   AuthenticationLevel = al-basicLevels / al-other
   al-basicLevels      = id-basicLevels ":" BasicLevels
   al-other            = id-other       ":" EXTERNAL
   id-basicLevels      = %x62.61.73.69.63.4C.65.76.65.6C.73
                            ; "basicLevels"
   id-other            = %x6F.74.68.65.72 ; "other"

   BasicLevels = "{"      sp bl-level
                    [ "," sp bl-localQualifier ]
                    [ "," sp bl-signed         ]
                          sp "}"

   bl-level          = id-level          msp Level



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   bl-localQualifier = id-localQualifier msp INTEGER
   bl-signed         = id-signed         msp BOOLEAN
   Level             = id-none / id-simple / id-strong
   id-level          = %x6C.65.76.65.6C ; "level"
   id-localQualifier = %x6C.6F.63.61.6C.51.75.61.6C.69.66.69.65.72
                          ; "localQualifier"
   id-signed         = %x73.69.67.6E.65.64 ; "signed"
   id-none           = %x6E.6F.6E.65       ; "none"
   id-simple         = %x73.69.6D.70.6C.65 ; "simple"
   id-strong         = %x73.74.72.6F.6E.67 ; "strong"

   ItemOrUserFirst    = ( id-itemFirst ":" ItemFirst ) /
                        ( id-userFirst ":" UserFirst )
   id-itemFirst       = %x69.74.65.6D.46.69.72.73.74 ; "itemFirst"
   id-userFirst       = %x75.73.65.72.46.69.72.73.74 ; "userFirst"

   ItemFirst          = "{" sp if-protectedItems ","
                            sp if-itemPermissions
                            sp "}"
   if-protectedItems  = id-protectedItems  msp ProtectedItems
   if-itemPermissions = id-itemPermissions msp ItemPermissions
   id-protectedItems  = %x70.72.6F.74.65.63.74.65.64.49.74.65.6D.73
                           ; "protectedItems"
   id-itemPermissions = %x69.74.65.6D.50.65.72.6D.69.73.73.69.6F.6E
                           %x73 ; "itemPermissions"

   UserFirst          = "{" sp uf-userClasses ","
                            sp uf-userPermissions
                            sp "}"
   uf-userClasses     = id-userClasses     msp UserClasses
   uf-userPermissions = id-userPermissions msp UserPermissions
   id-userClasses     = %x75.73.65.72.43.6C.61.73.73.65.73
                           ; "userClasses"
   id-userPermissions = %x75.73.65.72.50.65.72.6D.69.73.73.69.6F.6E
                           %x73 ; "userPermissions"

   ItemPermissions     = "{" [ sp ItemPermission
                            *( "," sp ItemPermission ) ] sp "}"
   ItemPermission      = "{" [ sp ip-precedence "," ]
                               sp ip-userClasses ","
                               sp ip-grantsAndDenials
                               sp "}"
   ip-precedence       = id-precedence       msp Precedence
   ip-userClasses      = id-userClasses      msp UserClasses
   ip-grantsAndDenials = id-grantsAndDenials msp GrantsAndDenials
   id-grantsAndDenials = %x67.72.61.6E.74.73.41.6E.64.44.65.6E.69.61
                            %x6C.73 ; "grantsAndDenials"




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   UserClasses  = "{"     [ sp uc-allUsers ]
                      [ sep sp uc-thisEntry ]
                      [ sep sp uc-name ]
                      [ sep sp uc-userGroup ]
                      [ sep sp uc-subtree ]
                            sp "}"
   uc-allUsers  = id-allUsers  msp NULL
   uc-thisEntry = id-thisEntry msp NULL
   uc-name      = id-name      msp NameAndOptionalUIDs
   uc-userGroup = id-userGroup msp NameAndOptionalUIDs
   uc-subtree   = id-subtree   msp SubtreeSpecifications
   id-allUsers  = %x61.6C.6C.55.73.65.72.73    ; "allUsers"
   id-thisEntry = %x74.68.69.73.45.6E.74.72.79 ; "thisEntry"
   id-name      = %x6E.61.6D.65                ; "name"
   id-userGroup = %x75.73.65.72.47.72.6F.75.70 ; "userGroup"
   id-subtree   = %x73.75.62.74.72.65.65       ; "subtree"

   NameAndOptionalUIDs = "{" sp NameAndOptionalUID
                            *( "," sp NameAndOptionalUID ) sp "}"
   NameAndOptionalUID  = "{"      sp nu-dn
                            [ "," sp nu-uid ]
                                  sp "}"
   nu-dn               = id-dn  msp DistinguishedName
   nu-uid              = id-uid msp UniqueIdentifier
   UniqueIdentifier    = BIT-STRING
   id-dn               = %x64.6E    ; "dn"
   id-uid              = %x75.69.64 ; "uid"

   SubtreeSpecifications = "{" sp SubtreeSpecification
                              *( "," sp SubtreeSpecification ) sp "}"

   UserPermissions     = "{" [ sp UserPermission
                            *( "," sp UserPermission ) ] sp "}"
   UserPermission      = "{" [ sp up-precedence "," ]
                               sp up-protectedItems ","
                               sp up-grantsAndDenials
                               sp "}"
   up-precedence       = id-precedence       msp Precedence
   up-protectedItems   = id-protectedItems   msp ProtectedItems
   up-grantsAndDenials = id-grantsAndDenials msp GrantsAndDenials

   ProtectedItems = "{"     [ sp pi-entry ]
                        [ sep sp pi-allUserAttributeTypes ]
                        [ sep sp pi-attributeType ]
                        [ sep sp pi-allAttributeValues ]
                        [ sep sp pi-allUserTypesAndValues ]
                        [ sep sp pi-attributeValue ]
                        [ sep sp pi-selfValue ]



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                        [ sep sp pi-rangeOfValues ]
                        [ sep sp pi-maxValueCount ]
                        [ sep sp pi-maxImmSub ]
                        [ sep sp pi-restrictedBy ]
                        ; contexts omitted
                        [ sep sp pi-classes ]
                              sp "}"

   pi-entry                 = id-entry msp NULL
   pi-allUserAttributeTypes = id-allUserAttributeTypes msp NULL
   pi-attributeType         = id-attributeType msp AttributeTypes
   pi-allAttributeValues    = id-allAttributeValues msp
                                 AttributeTypes
   pi-allUserTypesAndValues = id-allUserAttributeTypesAndValues msp
                                 NULL
   pi-attributeValue        = id-attributeValue msp
                                 AttributeTypeAndValues
   pi-selfValue             = id-selfValue msp AttributeTypes
   pi-rangeOfValues         = id-rangeOfValues msp Filter
   pi-maxValueCount         = id-maxValueCount msp MaxValueCounts
   pi-maxImmSub             = id-maxImmSub msp INTEGER
   pi-restrictedBy          = id-restrictedBy msp RestrictedValues
   pi-classes               = id-classes msp Refinement
   id-entry                 = %x65.6E.74.72.79 ; "entry"
   id-allUserAttributeTypes = %x61.6C.6C.55.73.65.72.41.74.74.72.69
                                 %x62.75.74.65.54.79.70.65.73
                                 ; "allUserAttributeTypes"
   id-attributeType         = %x61.74.74.72.69.62.75.74.65.54.79.70
                                 %x65 ; "attributeType"
   id-allAttributeValues    = %x61.6C.6C.41.74.74.72.69.62.75.74.65
                                 %x56.61.6C.75.65.73
                                 ; "allAttributeValues"
   id-attributeValue        = %x61.74.74.72.69.62.75.74.65.56.61.6C
                                 %x75.65 ; "attributeValue"
   id-selfValue             = %x73.65.6C.66.56.61.6C.75.65
                                 ; "selfValue"
   id-rangeOfValues         = %x72.61.6E.67.65.4F.66.56.61.6C.75.65
                                 %x73 ; "rangeOfValues"
   id-maxValueCount         = %x6D.61.78.56.61.6C.75.65.43.6F.75.6E
                                 %x74 ; "maxValueCount"
   id-maxImmSub             = %x6D.61.78.49.6D.6D.53.75.62
                                 ; "maxImmSub"
   id-restrictedBy          = %x72.65.73.74.72.69.63.74.65.64.42.79
                                 ; "restrictedBy"
   id-classes               = %x63.6C.61.73.73.65.73 ; "classes"

   id-allUserAttributeTypesAndValues = %x61.6C.6C.55.73.65.72.41.74
                              %x74.72.69.62.75.74.65.54.79.70.65.73



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                              %x41.6E.64.56.61.6C.75.65.73
                              ; "allUserAttributeTypesAndValues"

   AttributeTypes = "{" sp AttributeType
                       *( "," sp AttributeType ) sp "}"

   AttributeTypeAndValues = "{" sp AttributeTypeAndValue
                               *( "," sp AttributeTypeAndValue )
                               sp "}"

   AttributeTypeAndValue = "{" sp atav-type ","
                               sp atav-value
                               sp "}"
   atav-type  = id-type  msp AttributeType
   atav-value = id-value msp Value
   id-type    = %x74.79.70.65    ; "type"
   id-value   = %x76.61.6C.75.65 ; "value"

   MaxValueCounts = "{" sp MaxValueCount
                       *( "," sp MaxValueCount ) sp "}"
   MaxValueCount  = "{" sp mvc-type ","
                        sp mvc-maxCount
                        sp "}"
   mvc-type       = id-type msp AttributeType
   mvc-maxCount   = id-maxCount msp INTEGER
   id-maxCount    = %x6D.61.78.43.6F.75.6E.74 ; "maxCount"

   RestrictedValues = "{" sp RestrictedValue
                         *( "," sp RestrictedValue ) sp "}"
   RestrictedValue  = "{" sp rv-type ","
                          sp rv-valuesin
                          sp "}"
   rv-type          = id-type     msp AttributeType
   rv-valuesin      = id-valuesin msp AttributeType
   id-valuesin      = %x76.61.6C.75.65.73.69.6E ; "valuesin"

   GrantsAndDenials = "{" [ sp grantOrDeny
                         *( "," sp grantOrDeny ) ] sp "}"
   grantOrDeny = id-grantAdd
                 / id-denyAdd
                 / id-grantDiscloseOnError
                 / id-denyDiscloseOnError
                 / id-grantRead
                 / id-denyRead
                 / id-grantRemove
                 / id-denyRemove
                 / id-grantBrowse
                 / id-denyBrowse



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                 / id-grantExport
                 / id-denyExport
                 / id-grantImport
                 / id-denyImport
                 / id-grantModify
                 / id-denyModify
                 / id-grantRename
                 / id-denyRename
                 / id-grantReturnDN
                 / id-denyReturnDN
                 / id-grantCompare
                 / id-denyCompare
                 / id-grantFilterMatch
                 / id-denyFilterMatch
                 ; grantInvoke omitted
                 ; denyInvoke omitted

   id-grantAdd     = %x67.72.61.6E.74.41.64.64 ; "grantAdd"
   id-denyAdd      = %x64.65.6E.79.41.64.64 ; "denyAdd"
   id-grantBrowse  = %x67.72.61.6E.74.42.72.6F.77.73.65
                        ; "grantBrowse"
   id-denyBrowse   = %x64.65.6E.79.42.72.6F.77.73.65 ; "denyBrowse"
   id-grantCompare = %x67.72.61.6E.74.43.6F.6D.70.61.72.65
                        ; "grantCompare"
   id-denyCompare  = %x64.65.6E.79.43.6F.6D.70.61.72.65
                        ; "denyCompare"

   id-grantDiscloseOnError = %x67.72.61.6E.74.44.69.73.63.6C.6F.73.65
                                %x4F.6E.45.72.72.6F.72
                                ; "grantDiscloseOnError"
   id-denyDiscloseOnError  = %x64.65.6E.79.44.69.73.63.6C.6F.73.65.4F
                                %x6E.45.72.72.6F.72
                                ; "denyDiscloseOnError"

   id-grantExport      = %x67.72.61.6E.74.45.78.70.6F.72.74
                            ; "grantExport"
   id-denyExport       = %x64.65.6E.79.45.78.70.6F.72.74
                            ; "denyExport"
   id-grantFilterMatch = %x67.72.61.6E.74.46.69.6C.74.65.72.4D.61.74
                            %x63.68 ; "grantFilterMatch"
   id-denyFilterMatch  = %x64.65.6E.79.46.69.6C.74.65.72.4D.61.74.63
                            %x68 ; "denyFilterMatch"
   id-grantImport      = %x67.72.61.6E.74.49.6D.70.6F.72.74
                            ; "grantImport"
   id-denyImport       = %x64.65.6E.79.49.6D.70.6F.72.74
                            ; "denyImport"
   id-grantModify      = %x67.72.61.6E.74.4D.6F.64.69.66.79
                            ; "grantModify"



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   id-denyModify       = %x64.65.6E.79.4D.6F.64.69.66.79
                            ; "denyModify"
   id-grantRead        = %x67.72.61.6E.74.52.65.61.64 ; "grantRead"
   id-denyRead         = %x64.65.6E.79.52.65.61.64 ; "denyRead"
   id-grantRemove      = %x67.72.61.6E.74.52.65.6D.6F.76.65
                            ; "grantRemove"
   id-denyRemove       = %x64.65.6E.79.52.65.6D.6F.76.65
                            ; "denyRemove"
   id-grantRename      = %x67.72.61.6E.74.52.65.6E.61.6D.65
                            ; "grantRename"
   id-denyRename       = %x64.65.6E.79.52.65.6E.61.6D.65
                            ; "denyRename"
   id-grantReturnDN    = %x67.72.61.6E.74.52.65.74.75.72.6E.44.4E
                            ; "grantReturnDN"
   id-denyReturnDN     = %x64.65.6E.79.52.65.74.75.72.6E.44.4E
                            ; "denyReturnDN"

   The <sp>, <msp>, <sep>, <AttributeType>, <BIT-STRING>, <BOOLEAN>,
   <DirectoryString>, <DistinguishedName>, <EXTERNAL>, <INTEGER>,
   <INTEGER-0-MAX> and <NULL> rules are described in [GCE].

   The <SubtreeSpecification> and <Refinement> rules are described in
   [SUBENTRY].

   The <Value> rule is described in [GSER].

   Filter      = filter-item / filter-and / filter-or / filter-not
   filter-item = id-item ":" FilterItem
   filter-and  = id-and  ":" SetOfFilter
   filter-or   = id-or   ":" SetOfFilter
   filter-not  = id-not  ":" Filter
   id-and      = %x61.6E.64    ; "and"
   id-item     = %x69.74.65.6D ; "item"
   id-not      = %x6E.6F.74    ; "not"
   id-or       = %x6F.72       ; "or"

   SetOfFilter = "{" [ sp Filter *( "," sp Filter ) ] sp "}"

   FilterItem = fi-equality
                / fi-substrings
                / fi-greaterOrEqual
                / fi-lessOrEqual
                / fi-present
                / fi-approximateMatch
                / fi-extensibleMatch
                ; contextPresent omitted

   fi-equality         = id-equality ":" AttributeValueAssertion



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   fi-substrings       = id-substrings ":" SubstringsAssertion
   fi-greaterOrEqual   = id-greaterOrEqual ":"
                            AttributeValueAssertion
   fi-lessOrEqual      = id-lessOrEqual ":" AttributeValueAssertion
   fi-present          = id-present ":" AttributeType
   fi-approximateMatch = id-approximateMatch ":"
                            AttributeValueAssertion
   fi-extensibleMatch  = id-extensibleMatch ":" MatchingRuleAssertion
   id-equality         = %x65.71.75.61.6C.69.74.79 ; "equality"
   id-substrings       = %x73.75.62.73.74.72.69.6E.67.73
                            ; "substrings"
   id-greaterOrEqual   = %x67.72.65.61.74.65.72.4F.72.45.71.75.61.6C
                            ; "greaterOrEqual"
   id-lessOrEqual      = %x6C.65.73.73.4F.72.45.71.75.61.6C
                            ; "lessOrEqual"
   id-present          = %x70.72.65.73.65.6E.74 ; "present"
   id-approximateMatch = %x61.70.70.72.6F.78.69.6D.61.74.65.4D.61.74
                            %x63.68 ; "approximateMatch"
   id-extensibleMatch  = %x65.78.74.65.6E.73.69.62.6C.65.4D.61.74.63
                            %x68 ; "extensibleMatch"

   AttributeValueAssertion = "{" sp ava-type ","
                                 sp ava-assertion
                                 ; assertedContexts omitted
                                 sp "}"

   ava-type      = id-type      msp AttributeType
   ava-assertion = id-assertion msp Value
   id-assertion  = %x61.73.73.65.72.74.69.6F.6E ; "assertion"

   SubstringsAssertion = "{" sp sa-type ","
                             sp sa-strings
                             sp "}"

   sa-type    = id-type    msp AttributeType
   sa-strings = id-strings msp Substrings
   id-strings = %x73.74.72.69.6E.67.73 ; "strings"

   Substrings = "{" [ sp Substring *( "," sp Substring ) ] sp "}"
   Substring  = ss-initial
                / ss-any
                / ss-final
                ; control omitted
   ss-initial = id-initial ":" Value
   ss-any     = id-any     ":" Value
   ss-final   = id-final   ":" Value
   id-initial = %x69.6E.69.74.69.61.6C ; "initial"
   id-any     = %x61.6E.79             ; "any"



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   id-final   = %x66.69.6E.61.6C       ; "final"

   MatchingRuleAssertion = "{"      sp mra-matchingRule
                              [ "," sp mra-type ]
                                "," sp mra-matchValue
                              [ "," sp mra-dnAttributes ]
                                    sp "}"

   mra-matchingRule = id-matchingRule msp MatchingRuleIds
   mra-type         = id-type         msp AttributeType
   mra-matchValue   = id-matchValue   msp Value
   mra-dnAttributes = id-dnAttributes msp BOOLEAN
   id-matchingRule  = %x6D.61.74.63.68.69.6E.67.52.75.6C.65
                         ; "matchingRule"
   id-matchValue    = %x6D.61.74.63.68.56.61.6C.75.65 ; "matchValue"
   id-dnAttributes  = %x64.6E.41.74.74.72.69.62.75.74.65.73
                         ; "dnAttributes"

   MatchingRuleIds = "{" sp MatchingRuleId *( "," sp MatchingRuleId ) sp "}"
   MatchingRuleId  = OBJECT-IDENTIFIER

   The <OBJECT-IDENTIFIER> rule is described in [GCE].


Appendix B. Changes From Previous Drafts

B.1 Changes in Draft 01

   The Internet draft draft-legg-ldap-acm-admin-00.txt has been split
   into two drafts, draft-legg-ldap-admin-00.txt and
   draft-legg-ldap-acm-admin-01.txt.  Section 8 of
   draft-legg-ldapext-component-matching-06.txt has been extracted to
   become a separate Internet draft, draft-legg-ldap-gser-xx.txt.  The
   references in this document have been updated accordingly.

   The term "native LDAP encoding" has been replaced by the term
   "LDAP-specific encoding" to align with terminology anticipated to be
   used in the revision of RFC 2252.

   Changes have been made to the Search Operation Decision Points
   (Section 5.4.3):

   In 4) a), the assumed FilterMatch permission for a present match of
   the objectClass attribute has been removed. An LDAP search with a
   True filter [FILTER] is the best analogue of the DAP read operation.
   A True filter does not filter any attribute type and therefore does
   not require FilterMatch permissions to succeed.




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   In 5) b) and c), there is an additional requirement for Read
   permission for at least one attribute value before an attribute type
   can be returned in a search result.  Without this change a search
   result could, in some circumstances, disclose the existence of
   particular hidden attribute values.

B.2 Changes in Draft 02

   RFC 3377 replaces RFC 2251 as the reference for LDAP.

   An IANA Considerations section has been added.








































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