to allow the client to authenticate the server to which it is
communicating, or to perform "challenge-response" authentication. If
the client bound with the password choice, or the SASL mechanism does
not require the server to return information to the client, then this
field is not to be included in the result.
4.3. Unbind Operation
The function of the Unbind Operation is to terminate a protocol
session. The Unbind Operation is defined as follows:
UnbindRequest ::= [APPLICATION 2] NULL
The Unbind Operation has no response defined. Upon transmission of an
UnbindRequest, a protocol client may assume that the protocol session
is terminated. Upon receipt of an UnbindRequest, a protocol server
may assume that the requesting client has terminated the session and
that all outstanding requests may be discarded, and may close the
connection.
4.4. Unsolicited Notification
An unsolicited notification is an LDAPMessage sent from the server to
the client which is not in response to any LDAPMessage received by
the server. It is used to signal an extraordinary condition in the
server or in the connection between the client and the server. The
notification is of an advisory nature, and the server will not expect
any response to be returned from the client.
The unsolicited notification is structured as an LDAPMessage in which
the messageID is 0 and protocolOp is of the extendedResp form. The
responseName field of the ExtendedResponse is present. The LDAPOID
value MUST be unique for this notification, and not be used in any
other situation.
One unsolicited notification is defined in this document.
4.4.1. Notice of Disconnection
This notification may be used by the server to advise the client that
the server is about to close the connection due to an error
condition. Note that this notification is NOT a response to an
unbind requested by the client: the server MUST follow the procedures
of section 4.3. This notification is intended to assist clients in
distinguishing between an error condition and a transient network
failure. As with a connection close due to network failure, the
client MUST NOT assume that any outstanding requests which modified
the directory have succeeded or failed.
The responseName is 1.3.6.1.4.1.1466.20036, the response field is
absent, and the resultCode is used to indicate the reason for the
disconnection.
The following resultCode values are to be used in this notification:
- protocolError: The server has received data from the client in
which
the LDAPMessage structure could not be parsed.
- strongAuthRequired: The server has detected that an established
underlying security association protecting communication between
the client and server has unexpectedly failed or been compromised.
- unavailable: This server will stop accepting new connections and
operations on all existing connections, and be unavailable for an
extended period of time. The client may make use of an alternative
server.
After sending this notice, the server MUST close the connection.
After receiving this notice, the client MUST NOT transmit any further
on the connection, and may abruptly close the connection.
4.5. Search Operation
The Search Operation allows a client to request that a search be
performed on its behalf by a server. This can be used to read
attributes from a single entry, from entries immediately below a
particular entry, or a whole subtree of entries.
4.5.1. Search Request
The Search Request is defined as follows:
SearchRequest ::= [APPLICATION 3] SEQUENCE {
baseObject LDAPDN,
scope ENUMERATED {
baseObject (0),
singleLevel (1),
wholeSubtree (2) },
derefAliases ENUMERATED {
neverDerefAliases (0),
derefInSearching (1),
derefFindingBaseObj (2),
derefAlways (3) },
sizeLimit INTEGER (0 .. maxInt),
timeLimit INTEGER (0 .. maxInt),
typesOnly BOOLEAN,
filter Filter,
attributes AttributeDescriptionList }
Filter ::= CHOICE {
and [0] SET OF Filter,
or [1] SET OF Filter,
not [2] Filter,
equalityMatch [3] AttributeValueAssertion,
substrings [4] SubstringFilter,
greaterOrEqual [5] AttributeValueAssertion,
lessOrEqual [6] AttributeValueAssertion,
present [7] AttributeDescription,
approxMatch [8] AttributeValueAssertion,
extensibleMatch [9] MatchingRuleAssertion }
SubstringFilter ::= SEQUENCE {
type AttributeDescription,
-- at least one must be present
substrings SEQUENCE OF CHOICE {
initial [0] LDAPString,
any [1] LDAPString,
final [2] LDAPString } }
MatchingRuleAssertion ::= SEQUENCE {
matchingRule [1] MatchingRuleId OPTIONAL,
type [2] AttributeDescription OPTIONAL,
matchValue [3] AssertionValue,
dnAttributes [4] BOOLEAN DEFAULT FALSE }
Parameters of the Search Request are:
- baseObject: An LDAPDN that is the base object entry relative to
which the search is to be performed.
- scope: An indicator of the scope of the search to be performed. The
semantics of the possible values of this field are identical to the
semantics of the scope field in the X.511 Search Operation.
- derefAliases: An indicator as to how alias objects (as defined in
X.501) are to be handled in searching. The semantics of the
possible values of this field are:
neverDerefAliases: do not dereference aliases in searching
or in locating the base object of the search;
derefInSearching: dereference aliases in subordinates of
the base object in searching, but not in locating the
base object of the search;
derefFindingBaseObj: dereference aliases in locating
the base object of the search, but not when searching
subordinates of the base object;
derefAlways: dereference aliases both in searching and in
locating the base object of the search.
- sizelimit: A sizelimit that restricts the maximum number of entries
to be returned as a result of the search. A value of 0 in this
field indicates that no client-requested sizelimit restrictions are
in effect for the search. Servers may enforce a maximum number of
entries to return.
- timelimit: A timelimit that restricts the maximum time (in seconds)
allowed for a search. A value of 0 in this field indicates that no
client-requested timelimit restrictions are in effect for the
search.
- typesOnly: An indicator as to whether search results will contain
both attribute types and values, or just attribute types. Setting
this field to TRUE causes only attribute types (no values) to be
returned. Setting this field to FALSE causes both attribute types
and values to be returned.
- filter: A filter that defines the conditions that must be fulfilled
in order for the search to match a given entry.
The 'and', 'or' and 'not' choices can be used to form combinations of
filters. At least one filter element MUST be present in an 'and' or
'or' choice. The others match against individual attribute values of
entries in the scope of the search. (Implementor's note: the 'not'
filter is an example of a tagged choice in an implicitly-tagged
module. In BER this is treated as if the tag was explicit.)
A server MUST evaluate filters according to the three-valued logic
of X.511(93) section 7.8.1. In summary, a filter is evaluated to
either "TRUE", "FALSE" or "Undefined". If the filter evaluates
to TRUE for a particular entry, then the attributes of that entry
are returned as part of the search result (subject to any applicable
access control restrictions). If the filter evaluates to FALSE or
Undefined, then the entry is ignored for the search.
A filter of the "and" choice is TRUE if all the filters in the SET
OF evaluate to TRUE, FALSE if at least one filter is FALSE, and
otherwise Undefined. A filter of the "or" choice is FALSE if all
of the filters in the SET OF evaluate to FALSE, TRUE if at least
one filter is TRUE, and Undefined otherwise. A filter of the "not"
choice is TRUE if the filter being negated is FALSE, FALSE if it is
TRUE, and Undefined if it is Undefined.
The present match evaluates to TRUE where there is an attribute or
subtype of the specified attribute description present in an entry,
and FALSE otherwise (including a presence test with an unrecognized
attribute description.)
The extensibleMatch is new in this version of LDAP. If the
matchingRule field is absent, the type field MUST be present, and
the equality match is performed for that type. If the type field is
absent and matchingRule is present, the matchValue is compared
against all attributes in an entry which support that matchingRule,
and the matchingRule determines the syntax for the assertion value
(the filter item evaluates to TRUE if it matches with at least
one attribute in the entry, FALSE if it does not match any attribute
in the entry, and Undefined if the matchingRule is not recognized
or the assertionValue cannot be parsed.) If the type field is
present and matchingRule is present, the matchingRule MUST be one
permitted for use with that type, otherwise the filter item is
undefined. If the dnAttributes field is set to TRUE, the match is
applied against all the attributes in an entry's distinguished name
as well, and also evaluates to TRUE if there is at least one
attribute in the distinguished name for which the filter item
evaluates to TRUE. (Editors note: The dnAttributes field is present
so that there does not need to be multiple versions of generic
matching rules such as for word matching, one to apply to entries
and another to apply to entries and dn attributes as well).
A filter item evaluates to Undefined when the server would not
be able to determine whether the assertion value matches an
entry. If an attribute description in an equalityMatch, substrings,
greaterOrEqual, lessOrEqual, approxMatch or extensibleMatch
filter is not recognized by the server, a matching rule id in the
extensibleMatch is not recognized by the server, the assertion
value cannot be parsed, or the type of filtering requested is not
implemented, then the filter is Undefined. Thus for example if a
server did not recognize the attribute type shoeSize, a filter of
(shoeSize=*) would evaluate to FALSE, and the filters (shoeSize=12),
(shoeSize>=12) and (shoeSize<=12) would evaluate to Undefined.
Servers MUST NOT return errors if attribute descriptions or matching
rule ids are not recognized, or assertion values cannot be parsed.
More details of filter processing are given in section 7.8 of X.511
[8].
- attributes: A list of the attributes to be returned from each entry
which matches the search filter. There are two special values which
may be used: an empty list with no attributes, and the attribute
description string "*". Both of these signify that all user
attributes are to be returned. (The "*" allows the client to
request all user attributes in addition to specific operational
attributes).
Attributes MUST be named at most once in the list, and are returned
at most once in an entry. If there are attribute descriptions in
the list which are not recognized, they are ignored by the server.
If the client does not want any attributes returned, it can specify
a list containing only the attribute with OID "1.1". This OID was
chosen arbitrarily and does not correspond to any attribute in use.
Client implementors should note that even if all user attributes are
requested, some attributes of the entry may not be included in
search results due to access control or other restrictions.
Furthermore, servers will not return operational attributes, such
as objectClasses or attributeTypes, unless they are listed by name,
since there may be extremely large number of values for certain
operational attributes. (A list of operational attributes for use
in LDAP is given in [5].)
Note that an X.500 "list"-like operation can be emulated by the client
requesting a one-level LDAP search operation with a filter checking
for the existence of the objectClass attribute, and that an X.500
"read"-like operation can be emulated by a base object LDAP search
operation with the same filter. A server which provides a gateway to
X.500 is not required to use the Read or List operations, although it
may choose to do so, and if it does must provide the same semantics
as the X.500 search operation.
4.5.2. Search Result
The results of the search attempted by the server upon receipt of a
Search Request are returned in Search Responses, which are LDAP
messages containing either SearchResultEntry, SearchResultReference,
ExtendedResponse or SearchResultDone data types.
SearchResultEntry ::= [APPLICATION 4] SEQUENCE {
objectName LDAPDN,
attributes PartialAttributeList }
PartialAttributeList ::= SEQUENCE OF SEQUENCE {
type AttributeDescription,
vals SET OF AttributeValue }
-- implementors should note that the PartialAttributeList may
-- have zero elements (if none of the attributes of that entry
-- were requested, or could be returned), and that the vals set
-- may also have zero elements (if types only was requested, or
-- all values were excluded from the result.)
SearchResultReference ::= [APPLICATION 19] SEQUENCE OF LDAPURL
-- at least one LDAPURL element must be present
SearchResultDone ::= [APPLICATION 5] LDAPResult
Upon receipt of a Search Request, a server will perform the necessary
search of the DIT.
If the LDAP session is operating over a connection-oriented transport
such as TCP, the server will return to the client a sequence of
responses in separate LDAP messages. There may be zero or more
responses containing SearchResultEntry, one for each entry found
during the search. There may also be zero or more responses
containing SearchResultReference, one for each area not explored by
this server during the search. The SearchResultEntry and
SearchResultReference PDUs may come in any order. Following all the
SearchResultReference responses and all SearchResultEntry responses
to be returned by the server, the server will return a response
containing the SearchResultDone, which contains an indication of
success, or detailing any errors that have occurred.
Each entry returned in a SearchResultEntry will contain all
attributes, complete with associated values if necessary, as
specified in the attributes field of the Search Request. Return of
attributes is subject to access control and other administrative
policy. Some attributes may be returned in binary format (indicated
by the AttributeDescription in the response having the binary option
present).
Some attributes may be constructed by the server and appear in a
SearchResultEntry attribute list, although they are not stored
attributes of an entry. Clients MUST NOT assume that all attributes
can be modified, even if permitted by access control.
LDAPMessage responses of the ExtendedResponse form are reserved for
returning information associated with a control requested by the
client. These may be defined in future versions of this document.
4.5.3. Continuation References in the Search Result
If the server was able to locate the entry referred to by the
baseObject but was unable to search all the entries in the scope at
and under the baseObject, the server may return one or more
SearchResultReference, each containing a reference to another set of
servers for continuing the operation. A server MUST NOT return any
SearchResultReference if it has not located the baseObject and
thus has not searched any entries; in this case it would return a
SearchResultDone containing a referral resultCode.
In the absence of indexing information provided to a server from
servers holding subordinate naming contexts, SearchResultReference
responses are not affected by search filters and are always returned
when in scope.
The SearchResultReference is of the same data type as the Referral.
URLs for servers implementing the LDAP protocol are written according
to [9]. The <dn> part MUST be present in the URL, with the new target
object name. The client MUST use this name in its next request.
Some servers (e.g. part of a distributed index exchange system) may
provide a different filter in the URLs of the SearchResultReference.
If the filter part of the URL is present in an LDAP URL, the client
MUST use the new filter in its next request to progress the search,
and if the filter part is absent the client will use again the same
filter. Other aspects of the new search request may be the same or
different as the search which generated the continuation references.
Other kinds of URLs may be returned so long as the operation could be
performed using that protocol.
The name of an unexplored subtree in a SearchResultReference need not
be subordinate to the base object.
In order to complete the search, the client MUST issue a new search
operation for each SearchResultReference that is returned. Note that
the abandon operation described in section 4.11 applies only to a
particular operation sent on a connection between a client and server,
and if the client has multiple outstanding search operations to
different servers, it MUST abandon each operation individually.
4.5.3.1. Example
For example, suppose the contacted server (hosta) holds the entry
"O=MNN,C=WW" and the entry "CN=Manager,O=MNN,C=WW". It knows that
either LDAP-capable servers (hostb) or (hostc) hold
"OU=People,O=MNN,C=WW" (one is the master and the other server a
shadow), and that LDAP-capable server (hostd) holds the subtree
"OU=Roles,O=MNN,C=WW". If a subtree search of "O=MNN,C=WW" is
requested to the contacted server, it may return the following:
SearchResultEntry for O=MNN,C=WW
SearchResultEntry for CN=Manager,O=MNN,C=WW
SearchResultReference {
ldap://hostb/OU=People,O=MNN,C=WW
ldap://hostc/OU=People,O=MNN,C=WW
}
SearchResultReference {
ldap://hostd/OU=Roles,O=MNN,C=WW
}
SearchResultDone (success)
Client implementors should note that when following a
SearchResultReference, additional SearchResultReference may be
generated. Continuing the example, if the client contacted the
server (hostb) and issued the search for the subtree
"OU=People,O=MNN,C=WW", the server might respond as follows:
SearchResultEntry for OU=People,O=MNN,C=WW
SearchResultReference {
ldap://hoste/OU=Managers,OU=People,O=MNN,C=WW
}
SearchResultReference {
ldap://hostf/OU=Consultants,OU=People,O=MNN,C=WW
}
SearchResultDone (success)
If the contacted server does not hold the base object for the search,
then it will return a referral to the client. For example, if the
client requests a subtree search of "O=XYZ,C=US" to hosta, the server
may return only a SearchResultDone containing a referral.
SearchResultDone (referral) {
ldap://hostg/
}
4.6. Modify Operation
The Modify Operation allows a client to request that a modification
of an entry be performed on its behalf by a server. The Modify
Request is defined as follows:
ModifyRequest ::= [APPLICATION 6] SEQUENCE {
object LDAPDN,
modification SEQUENCE OF SEQUENCE {
operation ENUMERATED {
add (0),
delete (1),
replace (2) },
modification AttributeTypeAndValues } }
AttributeTypeAndValues ::= SEQUENCE {
type AttributeDescription,
vals SET OF AttributeValue }
Parameters of the Modify Request are:
- object: The object to be modified. The value of this field contains
the DN of the entry to be modified. The server will not perform
any alias dereferencing in determining the object to be modified.
- modification: A list of modifications to be performed on the entry.
The entire list of entry modifications MUST be performed
in the order they are listed, as a single atomic operation. While
individual modifications may violate the directory schema, the
resulting entry after the entire list of modifications is performed
MUST conform to the requirements of the directory schema. The
values that may be taken on by the 'operation' field in each
modification construct have the following semantics respectively:
add: add values listed to the given attribute, creating
the attribute if necessary;
delete: delete values listed from the given attribute,
removing the entire attribute if no values are listed, or
if all current values of the attribute are listed for
deletion;
replace: replace all existing values of the given attribute
with the new values listed, creating the attribute if it
did not already exist. A replace with no value will delete
the entire attribute if it exists, and is ignored if the
attribute does not exist.
The result of the modify attempted by the server upon receipt of a
Modify Request is returned in a Modify Response, defined as follows:
ModifyResponse ::= [APPLICATION 7] LDAPResult
Upon receipt of a Modify Request, a server will perform the necessary
modifications to the DIT.
The server will return to the client a single Modify Response
indicating either the successful completion of the DIT modification,
or the reason that the modification failed. Note that due to the
requirement for atomicity in applying the list of modifications in
the Modify Request, the client may expect that no modifications of
the DIT have been performed if the Modify Response received indicates
any sort of error, and that all requested modifications have been
performed if the Modify Response indicates successful completion of
the Modify Operation. If the connection fails, whether the
modification occurred or not is indeterminate.
The Modify Operation cannot be used to remove from an entry any of
its distinguished values, those values which form the entry's
relative distinguished name. An attempt to do so will result in the
server returning the error notAllowedOnRDN. The Modify DN Operation
described in section 4.9 is used to rename an entry.
If an equality match filter has not been defined for an attribute type,
clients MUST NOT attempt to delete individual values of that attribute
from an entry using the "delete" form of a modification, and MUST
instead use the "replace" form.
Note that due to the simplifications made in LDAP, there is not a
direct mapping of the modifications in an LDAP ModifyRequest onto the
EntryModifications of a DAP ModifyEntry operation, and different
implementations of LDAP-DAP gateways may use different means of
representing the change. If successful, the final effect of the
operations on the entry MUST be identical.
4.7. Add Operation
The Add Operation allows a client to request the addition of an entry
into the directory. The Add Request is defined as follows:
AddRequest ::= [APPLICATION 8] SEQUENCE {
entry LDAPDN,
attributes AttributeList }
AttributeList ::= SEQUENCE OF SEQUENCE {
type AttributeDescription,
vals SET OF AttributeValue }
Parameters of the Add Request are:
- entry: the Distinguished Name of the entry to be added. Note that
the server will not dereference any aliases in locating the entry
to be added.
- attributes: the list of attributes that make up the content of the
entry being added. Clients MUST include distinguished values
(those forming the entry's own RDN) in this list, the objectClass
attribute, and values of any mandatory attributes of the listed
object classes. Clients MUST NOT supply the createTimestamp or
creatorsName attributes, since these will be generated
automatically by the server.
The entry named in the entry field of the AddRequest MUST NOT exist
for the AddRequest to succeed. The parent of the entry to be added
MUST exist. For example, if the client attempted to add
"CN=JS,O=Foo,C=US", the "O=Foo,C=US" entry did not exist, and the
"C=US" entry did exist, then the server would return the error
noSuchObject with the matchedDN field containing "C=US". If the
parent entry exists but is not in a naming context held by the
server, the server SHOULD return a referral to the server holding the
parent entry.
Servers implementations SHOULD NOT restrict where entries can be
located in the directory. Some servers MAY allow the administrator
to restrict the classes of entries which can be added to the
directory.
Upon receipt of an Add Request, a server will attempt to perform the
add requested. The result of the add attempt will be returned to the
client in the Add Response, defined as follows:
AddResponse ::= [APPLICATION 9] LDAPResult
A response of success indicates that the new entry is present in the
directory.
4.8. Delete Operation
The Delete Operation allows a client to request the removal of an
entry from the directory. The Delete Request is defined as follows:
DelRequest ::= [APPLICATION 10] LDAPDN
The Delete Request consists of the Distinguished Name of the entry to
be deleted. Note that the server will not dereference aliases while
resolving the name of the target entry to be removed, and that only
leaf entries (those with no subordinate entries) can be deleted with
this operation.
The result of the delete attempted by the server upon receipt of a
Delete Request is returned in the Delete Response, defined as
follows:
DelResponse ::= [APPLICATION 11] LDAPResult
Upon receipt of a Delete Request, a server will attempt to perform
the entry removal requested. The result of the delete attempt will be
returned to the client in the Delete Response.
4.9. Modify DN Operation
The Modify DN Operation allows a client to change the leftmost (least
significant) component of the name of an entry in the directory, or
to move a subtree of entries to a new location in the directory. The
Modify DN Request is defined as follows:
ModifyDNRequest ::= [APPLICATION 12] SEQUENCE {
entry LDAPDN,
newrdn RelativeLDAPDN,
deleteoldrdn BOOLEAN,
newSuperior [0] LDAPDN OPTIONAL }
Parameters of the Modify DN Request are:
- entry: the Distinguished Name of the entry to be changed. This
entry may or may not have subordinate entries.
- newrdn: the RDN that will form the leftmost component of the new
name of the entry.
- deleteoldrdn: a boolean parameter that controls whether the old RDN
attribute values are to be retained as attributes of the entry, or
deleted from the entry.
- newSuperior: if present, this is the Distinguished Name of the entry
which becomes the immediate superior of the existing entry.
The result of the name change attempted by the server upon receipt of
a Modify DN Request is returned in the Modify DN Response, defined
as follows:
ModifyDNResponse ::= [APPLICATION 13] LDAPResult
Upon receipt of a ModifyDNRequest, a server will attempt to
perform the name change. The result of the name change attempt will
be returned to the client in the Modify DN Response.
For example, if the entry named in the "entry" parameter was
"cn=John Smith,c=US", the newrdn parameter was "cn=John Cougar Smith",
and the newSuperior parameter was absent, then this operation would
attempt to rename the entry to be "cn=John Cougar Smith,c=US". If
there was already an entry with that name, the operation would fail
with error code entryAlreadyExists.
If the deleteoldrdn parameter is TRUE, the values forming the old
RDN are deleted from the entry. If the deleteoldrdn parameter is
FALSE, the values forming the old RDN will be retained as
non-distinguished attribute values of the entry. The server may
not perform the operation and return an error code if the setting of
the deleteoldrdn parameter would cause a schema inconsistency in the
entry.
Note that X.500 restricts the ModifyDN operation to only affect
entries that are contained within a single server. If the LDAP
server is mapped onto DAP, then this restriction will apply, and the
resultCode affectsMultipleDSAs will be returned if this error
occurred. In general clients MUST NOT expect to be able to perform
arbitrary movements of entries and subtrees between servers.
4.10. Compare Operation
The Compare Operation allows a client to compare an assertion
provided with an entry in the directory. The Compare Request is
defined as follows:
CompareRequest ::= [APPLICATION 14] SEQUENCE {
entry LDAPDN,
ava AttributeValueAssertion }
Parameters of the Compare Request are:
- entry: the name of the entry to be compared with.
- ava: the assertion with which an attribute in the entry is to be
compared.
The result of the compare attempted by the server upon receipt of a
Compare Request is returned in the Compare Response, defined as
follows:
CompareResponse ::= [APPLICATION 15] LDAPResult
Upon receipt of a Compare Request, a server will attempt to perform
the requested comparison. The result of the comparison will be
returned to the client in the Compare Response. Note that errors and
the result of comparison are all returned in the same construct.
Note that some directory systems may establish access controls which
permit the values of certain attributes (such as userPassword) to be
compared but not read. In a search result, it may be that an
attribute of that type would be returned, but with an empty set of
values.
4.11. Abandon Operation
The function of the Abandon Operation is to allow a client to request
that the server abandon an outstanding operation. The Abandon
Request is defined as follows:
AbandonRequest ::= [APPLICATION 16] MessageID
The MessageID MUST be that of a an operation which was requested
earlier in this connection.
(The abandon request itself has its own message id. This is distinct
from the id of the earlier operation being abandoned.)
There is no response defined in the Abandon Operation. Upon
transmission of an Abandon Operation, a client may expect that the
operation identified by the Message ID in the Abandon Request has
been abandoned. In the event that a server receives an Abandon
Request on a Search Operation in the midst of transmitting responses
to the search, that server MUST cease transmitting entry responses to
the abandoned request immediately, and MUST NOT send the
SearchResponseDone. Of course, the server MUST ensure that only
properly encoded LDAPMessage PDUs are transmitted.
Clients MUST NOT send abandon requests for the same operation
multiple times, and MUST also be prepared to receive results from
operations it has abandoned (since these may have been in transit
when the abandon was requested).
Servers MUST discard abandon requests for message IDs they do not
recognize, for operations which cannot be abandoned, and for
operations which have already been abandoned.
4.12. Extended Operation
An extension mechanism has been added in this version of LDAP, in
order to allow additional operations to be defined for services not
available elsewhere in this protocol, for instance digitally signed
operations and results.
The extended operation allows clients to make requests and receive
responses with predefined syntaxes and semantics. These may be
defined in RFCs or be private to particular implementations. Each
request MUST have a unique OBJECT IDENTIFIER assigned to it.
ExtendedRequest ::= [APPLICATION 23] SEQUENCE {
requestName [0] LDAPOID,
requestValue [1] OCTET STRING OPTIONAL }
The requestName is a dotted-decimal representation of the OBJECT
IDENTIFIER corresponding to the request. The requestValue is
information in a form defined by that request, encapsulated inside an
OCTET STRING.
The server will respond to this with an LDAPMessage containing the
ExtendedResponse.
ExtendedResponse ::= [APPLICATION 24] SEQUENCE {
COMPONENTS OF LDAPResult,
responseName [10] LDAPOID OPTIONAL,
response [11] OCTET STRING OPTIONAL }
If the server does not recognize the request name, it MUST return
only the response fields from LDAPResult, containing the
protocolError result code.
5. Protocol Element Encodings and Transfer
One underlying service is defined here. Clients and servers SHOULD
implement the mapping of LDAP over TCP described in 5.2.1.
5.1. Mapping Onto BER-based Transport Services
The protocol elements of LDAP are encoded for exchange using the
Basic Encoding Rules (BER) [11] of ASN.1 [3]. However, due to the
high overhead involved in using certain elements of the BER, the
following additional restrictions are placed on BER-encodings of LDAP
protocol elements:
(1) Only the definite form of length encoding will be used.
(2) OCTET STRING values will be encoded in the primitive form only.
(3) If the value of a BOOLEAN type is true, the encoding MUST have
its contents octets set to hex "FF".
(4) If a value of a type is its default value, it MUST be absent.
Only some BOOLEAN and INTEGER types have default values in this
protocol definition.
These restrictions do not apply to ASN.1 types encapsulated inside of
OCTET STRING values, such as attribute values, unless otherwise
noted.
5.2. Transfer Protocols
This protocol is designed to run over connection-oriented, reliable
transports, with all 8 bits in an octet being significant in the data
stream.
5.2.1. Transmission Control Protocol (TCP)
The LDAPMessage PDUs are mapped directly onto the TCP bytestream. It
is recommended that server implementations running over the TCP MAY
provide a protocol listener on the assigned port, 389. Servers may
instead provide a listener on a different port number. Clients MUST
support contacting servers on any valid TCP port.
6. Implementation Guidelines
This document describes an Internet protocol.
6.1. Server Implementations
The server MUST be capable of recognizing all the mandatory attribute
type names and implement the syntaxes specified in [5]. Servers MAY
also recognize additional attribute type names.
6.2. Client Implementations
Clients which request referrals MUST ensure that they do not loop
between servers. They MUST NOT repeatedly contact the same server for
the same request with the same target entry name, scope and filter.
Some clients may be using a counter that is incremented each time
referral handling occurs for an operation, and these kinds of clients
MUST be able to handle a DIT with at least ten layers of naming
contexts between the root and a leaf entry.
In the absence of prior agreements with servers, clients SHOULD NOT
assume that servers support any particular schemas beyond those
referenced in section 6.1. Different schemas can have different
attribute types with the same names. The client can retrieve the
subschema entries referenced by the subschemaSubentry attribute in
the server's root DSE or in entries held by the server.
7. Security Considerations
When used with a connection-oriented transport, this version of the
protocol provides facilities for the LDAP v2 authentication
mechanism, simple authentication using a cleartext password, as well
as any SASL mechanism [12]. SASL allows for integrity and privacy
services to be negotiated.
It is also permitted that the server can return its credentials to
the client, if it chooses to do so.
Use of cleartext password is strongly discouraged where the
underlying transport service cannot guarantee confidentiality and may
result in disclosure of the password to unauthorized parties.
When used with SASL, it should be noted that the name field of the
BindRequest is not protected against modification. Thus if the
distinguished name of the client (an LDAPDN) is agreed through the
negotiation of the credentials, it takes precedence over any value in
the unprotected name field.
Implementations which cache attributes and entries obtained via LDAP
MUST ensure that access controls are maintained if that information
is to be provided to multiple clients, since servers may have access
control policies which prevent the return of entries or attributes in
search results except to particular authenticated clients. For
example, caches could serve result information only to the client
whose request caused it to be cache.
8. Acknowledgements
This document is an update to RFC1777, by Wengyik Yeong, Tim Howes,
and Steve Kille. Design ideas included in this document are based on
those discussed in ASID and other IETF Working Groups. The
contributions of individuals in these working groups is gratefully
acknowledged.
9. Bibliography
[1] ITU-T Rec. X.500, "The Directory: Overview of Concepts, Models
and Service", 1993.
[2] Yeong, W., Howes, T., and S. Kille, "Lightweight Directory Access
Protocol", RFC1777, March 1995.
[3] ITU-T Rec. X.680, "Abstract Syntax Notation One (ASN.1) -
Specification of Basic Notation", 1994.
[4] Kille, S., Wahl, M., and T. Howes, "Lightweight Directory Access
Protocol (v3): UTF-8 String Representation of Distinguished
Names", RFC2253, December 1997.
[5] Wahl, M., Coulbeck, A., Howes, T., and S. Kille, "Lightweight
Directory Access Protocol (v3): Attribute Syntax Definitions",
RFC2252, December 1997.
[6] ITU-T Rec. X.501, "The Directory: Models", 1993.
[7] Berners-Lee, T., Masinter, L., and M. McCahill, "Uniform
Resource Locators (URL)", RFC1738, December 1994.
[8] ITU-T Rec. X.511, "The Directory: Abstract Service Definition",
1993.
[9] Howes, T., and M. Smith, "The LDAP URL Format", RFC2255,
December 1997.
[10] Bradner, S., "Key words for use in RFCs to Indicate Requirement
Levels", RFC2119, March 1997.
[11] ITU-T Rec. X.690, "Specification of ASN.1 encoding rules: Basic,
Canonical, and Distinguished Encoding Rules", 1994.
[12] Meyers, J., "Simple Authentication and Security Layer",
RFC2222, October 1997.
[13] Universal Multiple-Octet Coded Character Set (UCS) -
Architecture and Basic Multilingual Plane, ISO/IEC 10646-1 :
1993.
[14] Yergeau, F., "UTF-8, a transformation format of Unicode and ISO
10646", RFC2044, October 1996.
10. Authors' Addresses
Mark Wahl
Critical Angle Inc.
4815 W Braker Lane #502-385
Austin, TX 78759
USA
Phone: +1 512 372-3160
EMail: M.Wahl@critical-angle.com
Tim Howes
Netscape Communications Corp.
501 E. Middlefield Rd., MS MV068
Mountain View, CA 94043
USA
Phone: +1 650 937-3419
EMail: howes@netscape.com
Steve Kille
Isode Limited
The Dome, The Square
Richmond
TW9 1DT
UK
Phone: +44-181-332-9091
EMail: S.Kille@isode.com
Appendix A - Complete ASN.1 Definition
Lightweight-Directory-Access-Protocol-V3 DEFINITIONS
IMPLICIT TAGS ::=
BEGIN
LDAPMessage ::= SEQUENCE {
messageID MessageID,
protocolOp CHOICE {
bindRequest BindRequest,
bindResponse BindResponse,
unbindRequest UnbindRequest,
searchRequest SearchRequest,
searchResEntry SearchResultEntry,
searchResDone SearchResultDone,
searchResRef SearchResultReference,
modifyRequest ModifyRequest,
modifyResponse ModifyResponse,
addRequest AddRequest,
addResponse AddResponse,
delRequest DelRequest,
delResponse DelResponse,
modDNRequest ModifyDNRequest,
modDNResponse ModifyDNResponse,
compareRequest CompareRequest,
compareResponse CompareResponse,
abandonRequest AbandonRequest,
extendedReq ExtendedRequest,
extendedResp ExtendedResponse },
controls [0] Controls OPTIONAL }
MessageID ::= INTEGER (0 .. maxInt)
maxInt INTEGER ::= 2147483647 -- (2^^31 - 1) --
LDAPString ::= OCTET STRING
LDAPOID ::= OCTET STRING
LDAPDN ::= LDAPString
RelativeLDAPDN ::= LDAPString
AttributeType ::= LDAPString
AttributeDescription ::= LDAPString
AttributeDescriptionList ::= SEQUENCE OF
AttributeDescription
AttributeValue ::= OCTET STRING
AttributeValueAssertion ::= SEQUENCE {
attributeDesc AttributeDescription,
assertionValue AssertionValue }
AssertionValue ::= OCTET STRING
Attribute ::= SEQUENCE {
type AttributeDescription,
vals SET OF AttributeValue }
MatchingRuleId ::= LDAPString
LDAPResult ::= SEQUENCE {
resultCode ENUMERATED {
success (0),
operationsError (1),
protocolError (2),
timeLimitExceeded (3),
sizeLimitExceeded (4),
compareFalse (5),
compareTrue (6),
authMethodNotSupported (7),
strongAuthRequired (8),
-- 9 reserved --
referral (10), -- new
adminLimitExceeded (11), -- new
unavailableCriticalExtension (12), -- new
confidentialityRequired (13), -- new
saslBindInProgress (14), -- new
noSuchAttribute (16),
undefinedAttributeType (17),
inappropriateMatching (18),
constraintViolation (19),
attributeOrValueExists (20),
invalidAttributeSyntax (21),
-- 22-31 unused --
noSuchObject (32),
aliasProblem (33),
invalidDNSyntax (34),
-- 35 reserved for undefined isLeaf --
aliasDereferencingProblem (36),
-- 37-47 unused --
inappropriateAuthentication (48),
invalidCredentials (49),
insufficientAccessRights (50),
busy (51),
unavailable (52),
unwillingToPerform (53),
loopDetect (54),
-- 55-63 unused --
namingViolation (64),
objectClassViolation (65),
notAllowedOnNonLeaf (66),
notAllowedOnRDN (67),
entryAlreadyExists (68),
objectClassModsProhibited (69),
-- 70 reserved for CLDAP --
affectsMultipleDSAs (71), -- new
-- 72-79 unused --
other (80) },
-- 81-90 reserved for APIs --
matchedDN LDAPDN,
errorMessage LDAPString,
referral [3] Referral OPTIONAL }
Referral ::= SEQUENCE OF LDAPURL
LDAPURL ::= LDAPString -- limited to characters permitted in URLs
Controls ::= SEQUENCE OF Control
Control ::= SEQUENCE {
controlType LDAPOID,
criticality BOOLEAN DEFAULT FALSE,
controlValue OCTET STRING OPTIONAL }
BindRequest ::= [APPLICATION 0] SEQUENCE {
version INTEGER (1 .. 127),
name LDAPDN,
authentication AuthenticationChoice }
AuthenticationChoice ::= CHOICE {
simple [0] OCTET STRING,
-- 1 and 2 reserved
sasl [3] SaslCredentials }
SaslCredentials ::= SEQUENCE {
mechanism LDAPString,
credentials OCTET STRING OPTIONAL }
BindResponse ::= [APPLICATION 1] SEQUENCE {
COMPONENTS OF LDAPResult,
serverSaslCreds [7] OCTET STRING OPTIONAL }
UnbindRequest ::= [APPLICATION 2] NULL
SearchRequest ::= [APPLICATION 3] SEQUENCE {
baseObject LDAPDN,
scope ENUMERATED {
baseObject (0),
singleLevel (1),
wholeSubtree (2) },
derefAliases ENUMERATED {
neverDerefAliases (0),
derefInSearching (1),
derefFindingBaseObj (2),
derefAlways (3) },
sizeLimit INTEGER (0 .. maxInt),
timeLimit INTEGER (0 .. maxInt),
typesOnly BOOLEAN,
filter Filter,
attributes AttributeDescriptionList }
Filter ::= CHOICE {
and [0] SET OF Filter,
or [1] SET OF Filter,
not [2] Filter,
equalityMatch [3] AttributeValueAssertion,
substrings [4] SubstringFilter,
greaterOrEqual [5] AttributeValueAssertion,
lessOrEqual [6] AttributeValueAssertion,
present [7] AttributeDescription,
approxMatch [8] AttributeValueAssertion,
extensibleMatch [9] MatchingRuleAssertion }
SubstringFilter ::= SEQUENCE {
type AttributeDescription,
-- at least one must be present
substrings SEQUENCE OF CHOICE {
initial [0] LDAPString,
any [1] LDAPString,
final [2] LDAPString } }
MatchingRuleAssertion ::= SEQUENCE {
matchingRule [1] MatchingRuleId OPTIONAL,
type [2] AttributeDescription OPTIONAL,
matchValue [3] AssertionValue,
dnAttributes [4] BOOLEAN DEFAULT FALSE }
SearchResultEntry ::= [APPLICATION 4] SEQUENCE {
objectName LDAPDN,
attributes PartialAttributeList }
PartialAttributeList ::= SEQUENCE OF SEQUENCE {
type AttributeDescription,
vals SET OF AttributeValue }
SearchResultReference ::= [APPLICATION 19] SEQUENCE OF LDAPURL
SearchResultDone ::= [APPLICATION 5] LDAPResult
ModifyRequest ::= [APPLICATION 6] SEQUENCE {
object LDAPDN,
modification SEQUENCE OF SEQUENCE {
operation ENUMERATED {
add (0),
delete (1),
replace (2) },
modification AttributeTypeAndValues } }
AttributeTypeAndValues ::= SEQUENCE {
type AttributeDescription,
vals SET OF AttributeValue }
ModifyResponse ::= [APPLICATION 7] LDAPResult
AddRequest ::= [APPLICATION 8] SEQUENCE {
entry LDAPDN,
attributes AttributeList }
AttributeList ::= SEQUENCE OF SEQUENCE {
type AttributeDescription,
vals SET OF AttributeValue }
AddResponse ::= [APPLICATION 9] LDAPResult
DelRequest ::= [APPLICATION 10] LDAPDN
DelResponse ::= [APPLICATION 11] LDAPResult
ModifyDNRequest ::= [APPLICATION 12] SEQUENCE {
entry LDAPDN,
newrdn RelativeLDAPDN,
deleteoldrdn BOOLEAN,
newSuperior [0] LDAPDN OPTIONAL }
ModifyDNResponse ::= [APPLICATION 13] LDAPResult
CompareRequest ::= [APPLICATION 14] SEQUENCE {
entry LDAPDN,
ava AttributeValueAssertion }
CompareResponse ::= [APPLICATION 15] LDAPResult
AbandonRequest ::= [APPLICATION 16] MessageID
ExtendedRequest ::= [APPLICATION 23] SEQUENCE {
requestName [0] LDAPOID,
requestValue [1] OCTET STRING OPTIONAL }
ExtendedResponse ::= [APPLICATION 24] SEQUENCE {
COMPONENTS OF LDAPResult,
responseName [10] LDAPOID OPTIONAL,
response [11] OCTET STRING OPTIONAL }
END
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