Application Working Group M. Ansari
INTERNET-DRAFT Sun Microsystems, Inc.
Expires June 2002 L. Howard
PADL Software Pty. Ltd.
B. Joslin [ed.]
Hewlett-Packard Company
July 19, 2001
Intended Category: Informational
A Configuration Schema for LDAP Based
Directory User Agents
<draft-joslin-config-schema-03.txt>
Status of this Memo
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Abstract
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This document describes a mechanism for global configuration of
similar directory user agents. This document proposes a schema for
configuration of these DUAs that may be discovered using the Light-
weight Directory Access Protocol [RFC2251]. A set of attribute
types and an objectclass are proposed, along with specific guide-
lines for interpreting them. A significant feature of the global
configuration policy for DUAs, is a mechanism that allows DUAs to
re-configure their schema to that of the end user's environment.
This configuration is achieved through attribute and objectclass
mapping. This document is intended to be a skeleton for future
documents that describe configuration of specific DUA services.
1. Background & Motivation
The LDAP protocol has brought about a new and nearly ubiquitous
acceptance of the directory server. Many new client applications
(DUAs) are being created that use LDAP directories for many dif-
ferent services. And although the LDAP protocol has eased the
development of these applications, some challenges still exist for
both developers and directory administrators.
The authors of this document are implementors of DUAs described by
RFC 2307 [14]. In developing these agents, we felt there are
several issues that still need to be addressed to ease the deploy-
ment and configuration of a large network of these DUAs.
One of these challenges stems from the lack of a utopian schema. A
utopian schema would be one that every application developer could
agree upon and that would support every application. Unfortunately
today, many DUAs define their own schema (like RFC 2307 vs
Microsoft's Services for Unix [13]) containing similar attributes,
but with different attribute names. This can lead to data redun-
dancy within directory entries and give directory administrators
unwanted challenges, updating schemas and synchronizing data.
So, one goal of this document is to eliminate data redundancy by
having DUAs configure themselves to the schema of the deployed
directory, instead of forcing it's own schema on the directory.
Another goal of this document is to provide the DUA with enough
configuration information so that it can discover how to retrieve
its data in the directory, such as what locations to search in the
directory tree.
Finally, this document intends to describe a configuration method
for DUAs that can be shared among many DUAs, on various platforms,
providing as such, a configuration profile. The purpose being to
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centralize and simplify management of DUAs.
This document is intended to provide the skeleton framework for
future drafts, which will describe the individual implementation
details for the particular services provided by that DUA. The
authors of this document plan to develop such a document for the
Network Information Service DUA, described by RFC 2307 or it's suc-
cessor.
We expect that as DUAs take advantage of this configuration scheme,
each DUA will require additional configuration paramenters, not
specified by this document. Thus, we would expect that new auxili-
ary object classes, containing new configuration attributes will be
created, and then joined with the structural class defined by this
document to create a configuration profile for a particular DUA
service. And that by joining various auxiliary objectclasses for
different DUA services, that configuration of various DUA services
can be controlled by a single configuration profile entry.
2. General Issues
The schema defined by this document is defined under the "DUA Con-
figuration Schema." This schema is derived from the OID: iso (1)
org (3) dod (6) internet (1) private (4) enterprises (1) Hewlett-
Packard Company (11) directory (1) LDAP-UX Integration Project (3)
DUA Configuration Schema (1). This OID is represented in this
document by the keystring "DUAConfSchemaOID"
(1.3.6.1.4.1.11.1.3.1).
2.1 Terminology
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 [15].
2.2 Attributes
The attributes and classes defined in this document are summarized
below.
The following attributes are defined in this document:
preferredServerList
defaultServerList
defaultSearchBase
defaultSearchScope
authenticationMethod
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credentialLevel
serviceSearchDescriptor
serviceCredentialLevel
serviceAuthenticationMethod
attributeMap
objectclassMap
searchTimeLimit
bindTimeLimit
followReferrals
profileTTL
2.3 Object Classes
The following object class is defined in this document:
DUAConfigProfile
2.4 Syntax Definitions
The following syntax definitions are used throughout this document.
This document does not define new syntaxes that must be supported
by the directory server. The string encodings used by the attri-
butes defined in this document can be found section 5.
keystring as defined by RFC 2252 [2]
descr as defined by RFC 2252 section 4.1
a as defined by RFC 2252 section 4.1
d as defined by RFC 2252 section 4.1
space as defined by RFC 2252 section 4.1
whsp as defined by RFC 2252 section 4.1
base as defined by RFC 2253 [3]
DistinguishedName as defined by RFC 2253 section 2
RelativeDistinguishedName as defined by RFC 2253 section 2
scope as defined by RFC 2255 [5]
IPv4address as defined by RFC 2396 [9]
hostport as defined by RFC 2396 section 3.2.2
port as defined by RFC 2396 section 3.2.2
ipv6reference as defined by RFC 2732 [10]
host as defined by RFC 2732 section 3
serviceId = keystring
3. Attribute Definitions
This section contains attribute definitions to be used by DUAs when
discovering their configuration.
( DUAConfSchemaOID.1.0 NAME 'defaultServerList'
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DESC 'Default LDAP server host address used by a DUA'
EQUALITY caseIgnoreMatch
SYNTAX 1.3.6.1.4.1.1466.115.121.1.15
SINGLE-VALUE )
( DUAConfSchemaOID.1.1 NAME 'defaultSearchBase'
DESC 'Default LDAP base DN used by a DUA'
EQUALITY distinguishedNameMatch
SYNTAX 1.3.6.1.4.1.1466.115.121.1.12
SINGLE-VALUE )
( DUAConfSchemaOID.1.2 NAME 'preferredServerList'
DESC 'Preferred LDAP server host addresses to be used by a
DUA'
EQUALITY caseIgnoreMatch
SYNTAX 1.3.6.1.4.1.1466.115.121.1.15
SINGLE-VALUE )
( DUAConfSchemaOID.1.3 NAME 'searchTimeLimit'
DESC 'Maximum time in seconds a DUA should allow for a
search to complete'
EQUALITY integerMatch
SYNTAX 1.3.6.1.4.1.1466.115.121.1.27
SINGLE-VALUE )
( DUAConfSchemaOID.1.4 NAME 'bindTimeLimit'
DESC 'Maximum time in seconds a DUA should allow for the
bind operation to complete'
EQUALITY integerMatch
SYNTAX 1.3.6.1.4.1.1466.115.121.1.27
SINGLE-VALUE )
( DUAConfSchemaOID.1.5 NAME 'followReferrals'
DESC 'Tells DUA if it should follow referrals
returned by a DSA search result'
EQUALITY caseIgnoreIA5Match
SYNTAX 1.3.6.1.4.1.1466.115.121.1.7
SINGLE-VALUE )
( DUAConfSchemaOID.1.6 NAME 'authenticationMethod'
DESC 'A keystring which identifies the type of
authentication method used to contact the DSA'
EQUALITY caseIgnoreMatch
SYNTAX 1.3.6.1.4.1.1466.115.121.1.15
SINGLE-VALUE )
( DUAConfSchemaOID.1.7 NAME 'profileTTL'
DESC 'Time to live, in seconds, before a client DUA
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should re-read this configuration profile'
EQUALITY integerMatch
SYNTAX 1.3.6.1.4.1.1466.115.121.1.27
SINGLE-VALUE )
( DUAConfSchemaOID.1.14 NAME 'serviceSearchDescriptor'
DESC 'LDAP search descriptor list used by a DUA'
EQUALITY caseExactMatch
SYNTAX 1.3.6.1.4.1.1466.115.121.1.15 )
( DUAConfSchemaOID.1.9 NAME 'attributeMap'
DESC 'Attribute mappings used by a DUA'
EQUALITY caseIgnoreIA5Match
SYNTAX 1.3.6.1.4.1.1466.115.121.1.26 )
( DUAConfSchemaOID.1.10 NAME 'credentialLevel'
DESC 'Identifies type of credentials a DUA should
use when binding to the LDAP server'
EQUALITY caseIgnoreIA5Match
SYNTAX 1.3.6.1.4.1.1466.115.121.1.26
SINGLE-VALUE )
( DUAConfSchemaOID.1.11 NAME 'objectclassMap'
DESC 'Objectclass mappings used by a DUA'
EQUALITY caseIgnoreIA5Match
SYNTAX 1.3.6.1.4.1.1466.115.121.1.26 )
( DUAConfSchemaOID.1.12 NAME 'defaultSearchScope'
DESC 'Default search scope used by a DUA'
EQUALITY caseIgnoreIA5Match
SYNTAX 1.3.6.1.4.1.1466.115.121.1.26
SINGLE-VALUE )
( DUAConfSchemaOID.1.13 NAME 'serviceCredentialLevel'
DESC 'Identifies type of credentials a DUA
should use when binding to the LDAP server for a
specific service'
EQUALITY caseIgnoreIA5Match
SYNTAX 1.3.6.1.4.1.1466.115.121.1.26 )
( DUAConfSchemaOID.1.15 NAME 'serviceAuthenticationMethod'
DESC 'Authentication Method used by a service of the DUA'
EQUALITY caseIgnoreMatch
SYNTAX 1.3.6.1.4.1.1466.115.121.1.15 )
4. Class Definition
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The objectclass below is constructed from the attributes defined in
3, with the exception of the cn attribute, which is defined in RFC
2256 [8]. cn is used to represent the name of the DUA configura-
tion profile.
( DUAConfSchemaOID.2.4 NAME 'DUAConfigProfile'
SUP top STRUCTURAL
DESC 'Abstraction of a base configuration for a DUA'
MUST ( cn )
MAY ( defaultServerList $ preferredServerList $
defaultSearchBase $ defaultSearchScope $
searchTimeLimit $ bindTimeLimit $
credentialLevel $ authenticationMethod $
followReferrals $ serviceSearchDescriptor $
serviceCredentialLevel $ serviceAuthenticationMethod $
objectclassMap $ attributeMap $
profileTTL ) )
5. Implementation Details
5.1.1 Interpreting the preferredServerList attribute
Interpretation:
As described by the syntax, the preferredServerList parameter
is a white-space separated list of server addresses and asso-
ciated port numbers. When the DUA needs to contact a DSA, the
DUA MUST first attempt to contact one of the servers listed in
the preferredServerList attribute. The DUA should contact the
DSA specified by the first server address in the list. If
that DSA is unavailable, the remaining DSAs should be queried
in the order provided until a connection is established with a
DSA. Once a connection with a DSA is established, the DUA
SHOULD NOT attempt to establish a connection with the remain-
ing DSAs.
If the DUA is unable to contact any of the DSAs specified by
the preferredServerList, the defaultServerList attribute
should be examined, as described in 5.1.2. The servers iden-
tified by the preferredServerList MUST be contacted before
attempting to contact any of the servers specified by the
defaultServerList.
Syntax:
serverList = host *(space [host])
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Default Value:
The preferredServerList attribute does not have a default
value. Instead a DUA should examine the defaultServerList
attribute.
Other attribute notes:
This attribute is used in conjunction with the defaultServer-
List attribute. Please see section 5.1.2 for additional
implementation notes. Determining how the DUA should query
the DSAs also depends on the additional configuration attri-
butes, credentialLevel, serviceCredentialLevel, bindTimeLimit,
serviceAuthenticationMethod and authenticationMethod. Please
review section 5.2 for details on how a Posix DUA should prop-
erly bind to a DSA.
Example:
preferredServerList: 1.2.3.4 ldap1.mycorp.com ldap2:1389
[1080::8:800:200C:417A]:1389
5.1.2 Interpreting the defaultServerList attribute
Interpretation:
The defaultServerList attribute MUST only be examined if the
preferredServerList attribute is not provided, or the DUA is
unable to establish a connection with one of the DSAs speci-
fied by the preferredServerList.
If more than one address is provided, the DUA may choose to
either accept the order provided, or choose to create its own
order, based on what the DUA determines is the "best" order of
servers to query. For example, the DUA may choose to examine
the server list and choose to query the DSAs in order based on
the "closest" server or the server with the least amount of
"load." Interpretation of the "best" server order is entirely
up to the DUA, and not part of this document.
Once the order of server addresses is determined, the DUA
should contact the DSA specified by the first server address
in the list. If that DSA is unavailable, the remaining DSAs
should be queried until an available DSA is found or no more
DSAs are available. If a server address or port is invalid,
the DUA should proceed to the next server address as described
just above.
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Syntax:
serverList = host *(space [host])
Default Value:
If a defaultServerList attribute is not provided, the DUA
should attempt to contact the same DSA which provided the con-
figuration profile entry itself. The default DSA is contacted
only if the preferredServerList attribute is also not pro-
vided.
Other attribute notes:
This attribute is used in conjunction with the preferredSer-
verList attribute. Please see section 5.1.1 for additional
implementation notes. Determining how the DUA should query
the DSAs also depends on the additional configuration attri-
butes, credentialLevel, serviceCredentialLevel, bindTimeLimit,
serviceAuthenticationMethod and authenticationMethod. Please
review section 5.2 for details on how a DUA should properly
contact a DSA.
Example:
defaultServerList: 1.2.3.4 ldap1.mycorp.com ldap2:1389
[1080::8:800:200C:417A]:1389
5.1.3 Interpreting the defaultSearchBase attribute
Interpretation:
When a DUA needs to search the DSA for information, this
attribute provides the "base" for the search. This parameter
can be overridden or appended by the serviceSearchDescriptor
attribute. See section 5.1.6.
Syntax:
Defined by 1.3.6.1.4.1.1466.115.121.1.12
Default Value:
There is no default value for the defaultSearchBase.
Other attribute notes:
This attribute is used in conjunction with the
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serviceSearchDescriptor attribute. See section 5.1.6.
Example:
defaultSearchBase: dc=mycompany,dc=com
5.1.4 Interpreting the authenticationMethod attribute
Interpretation:
The authenticationMethod attribute defines an ordered list of
LDAP bind methods to be used when attempting to contact a DSA.
The serviceAuthenticationAtrribute overrides this value for a
particular service (see 5.1.14.) Each method MUST be
attempted in the order provided by the attribute, until a suc-
cessful LDAP bind is performed ("none" is assumed to always be
successful). See section 5.2 for more information.
none - The DUA does not perform an LDAP bind.
simple - The DUA performs an LDAP simple bind.
sasl - The DUA performs an LDAP SASL bind using the
specified SASL mechanism and options.
tls - The DUA performs an LDAP start_tls operation
followed by the specified bind method (for more
information refer to section 5.1 of RFC 2830).
Syntax:
authMethod = method *(";" method)
method = none | simple | sasl | tls
none = "none"
simple = "simple"
sasl = "sasl/" saslmech [ ":" sasloption ]
sasloption = "auth-conf" | "auth-int"
tls = "tls:" (none | simple | sasl)
saslmech = SASL mechanism name as defined in
RFC 2222, section 3
Note: Although multiple authentication methods may be speci-
fied in the syntax, at most one of each type is allowed.
Default Value:
If the authenticationMethod or serviceAutenticationMethod (for
that particular service) attributes are not provided, the DUA
may choose to bind to the DSA using any method. However, if
either authenticationMethod or serviceAuthenticationMethod are
provided, the DUA MUST only use the methods specified.
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Other attribute notes:
When using TLS, the string "tls:sasl/EXTERNAL" implies that
two way authentication is to be performed. Any other TLS
authentication method implies one way (DSA side credential)
authentication.
Determining how the DUA should bind to the DSAs also depends
on the additional configuration attributes, credentialLevel,
serviceCredentialLevel, serviceAuthenticationMethod and
bindTimeLimit. Please review section 5.2 for details on how
to properly bind to a DSA.
Example:
authenticationMethod: tls:simple;sasl/DIGEST-MD5
5.1.5 Interpreting the credentialLevel attribute
Interpretation:
The credentialLevel attribute defines what type(s) of
credential(s) the DUA should use when contacting the DSA. The
serviceCredentialLevel overrides this value for a particular
service (5.1.15.) The credentialLevel can contain more than
one credential type, separated by white space.
anonymous - The DUA should not use a credential when binding
to the DSA.
proxy - The DUA should use a known proxy identity when binding
to the DSA. A proxy identity is a specific credential that
was created to represent the DUA. This document does not
define how the proxy user should be created, or how the DUA
should determine what the proxy user's credential is. This
functionality is up to each implementation.
self - When the DUA is acting on behalf of a "real user" the
DUA should attempt to bind to the DSA as that user. The DUA
should map the user's identity to a credential used in the
directory.
If the DUA contains more than one credential type, the DUA
MUST use the credential types in the order specified. As soon
as the DUA is able to successfully bind to the DSA, the DUA
should not attempt to bind using the remaining credential
types. If the DUA discovers that the credentials specified
are invalid, it SHOULD NOT attempt further binds using any
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additional methods.
Syntax:
credentialLevel = level *(space level)
level = self | proxy | anonymous
self = "self"
proxy = "proxy"
anonymous = "anonymous"
Note: Although multiple credentialLevels may be specified in
the syntax, at most one of each type is allowed. Refer to
implementation notes in section 5.2 for additional syntax
requirements for the credentialLevel attribute.
Default Value:
If the credentialLevel attribute is not defined, the DUA
should not use a credential when binding to the DSA (also
known as anonymous.)
Other attribute notes:
Determining how the DUA should bind to the DSAs also depends
on the additional configuration attributes, authentication-
Method, serviceAuthenticationMethod, serviceCredentialLevel
and bindTimeLimit. Please review section 5.2 for details on
how to properly bind to a DSA.
Example:
credentialLevel: proxy anonymous
5.1.6 Interpreting the serviceSearchDescriptor attribute
Interpretation:
The serviceSearchDescriptor attribute defines how and where a
DUA should search for information for a particular service.
The serviceSearchDescriptor contains a serviceId, followed by
one or more base-scope-filter triples. These base-scope-
filter triples are used to define searches only for the
specific service. Multiple base-scope-filters allow the DUA
to search for data in multiple locations of the DIT.
In addition to the triples, serviceSearchDescriptor might also
contain the DN of an entry which will contain an alternate
profile. The DSA SHOULD re-evaluate the alternate profile an
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perform searches as specified by that profile.
If the base, as defined in the serviceSearchDescriptor, is
followed by the "," (ASCII 0x2C) character, this base is known
as a relative base. This relative base may be constructed of
one or more RDN components. The DUA MUST define the search
base by appending the relative base with the defaultSear-
chBase.
Syntax:
serviceSearchList = serviceId ":" serviceSearchDesc
*(";" serviceSearchDesc)
serviceSearchDesc = confReferral | searchDescriptor
searchDescriptor = [base] ["?" [scope] ["?" [filter]]]
confReferral = "ref:" DistinguishedName
base = DistinguishedName |
RelativeBaseName ","
RelativeBaseName = 1*(RelativeDistinguishedName)
filter = UTF-8 encoded string
If the base or filter contains the ";" (ASCII 0x3B) "?" (ASCII
0x3F) """ (ASCII 0x22) or "\" (ASCII 0x5C) characters, those
characters MUST be escaped (preceded with the "\" character.)
Alternately the DN may surrounded by quotes (ASCII 0x22.)
Refer to RFC 2253, section 4. If the base or filter are sur-
rounded by quotes, only the """ character needs to be escaped.
Any character that is preceded by the "\" character, which
does not need to be escaped results in both "\" character and
the character itself.
The filter string syntax can be more rigorously defined by the
DUA service. A suggested syntax would be that as defined by
RFC 2253.
If a DUA is performing a search for a particular service which has
a serviceSearchDescriptor defined, the DUA MUST set the base, scope
and filter as defined. Each base-scope-filter triple represents a
single LDAP search operation. If multiple base-scope-filter tri-
ples are provided, the DUA SHOULD perform the search requests in
the order specified by the serviceSearchDescriptor.
Default Values:
If a serviceSearchDescriptor or an element there-of is not defined
for a particular service, the DUA SHOULD create the base, scope and
filter as follows:
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base - Same as the defaultSearchBase
scope - Same as the defaultSearchScope
filter - Use defaults as defined by DUAs service.
If the defaultSearchBase is not defined, then the DUAs service may
use its own default.
Other attribute notes:
If a serviceSearchDescriptor exists for a given service, the ser-
vice MUST use at least one base-scope-filter triple in performing
searches. It MAY perform multiple searches per service if multiple
base-scope-filter triples are defined for that service.
The details of how the "filter" is interpreted by each DUAs service
is defined by each service. This means the filter is NOT REQUIRED
to be a legal LDAP filter [4]. Furthermore, whether attribute map-
ping or objectclass mapping applies to the filter or not should be
defined by each service.
It is assumed the serviceID is unique to a given service within the
scope of the DSA.
Example:
defaultSearchBase: dc=mycompany,dc=com
serviceSearchDescriptor: email:ou=people,ou=org1,?
one;ou=contractor,?one;
ref:cn=profile,dc=mycompany,dc=com
In this example, the DUA MUST search in
"ou=people,ou=org1,dc=mycompany,dc=com" first. The DUA then SHOULD
search in "ou=contractor,dc=mycompany,dc=com", and finally it
SHOULD search other locations as specified in the profile described
at "cn=profile,dc=mycompany,dc=com". For more examples, see sec-
tion
5.1.7 Interpreting the attributeMap attribute
Interpretation:
A DUA SHOULD perform attribute mapping for all LDAP operations
performed for a service which has an attributeMap entry.
Because attribute mapping is specific to each service within
the DUA, a "serviceId" is required as part of the attributeMap
syntax. I.E. not all DUA services should necessarily perform
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the same attribute mapping.
Attribute mapping SHOULD only be used to map attributes of
similar syntaxes as required by the service supported by the
DUA. However, a DUA is NOT REQUIRED to verify syntaxes of
mapped attributes. If the DUA does discover that the syntax
of the mapped attribute does not match that of the original
attribute, the DUA MAY perform translation between the origi-
nal syntax and the new syntax.
Syntax:
attributeMap = serviceId ":" origAttribute "="
attributes
origAttribute = attribute
attributes = wattribute *( space wattribute )
wattribute = whsp newAttribute whsp
newAttribute = descr | "*NULL*"
attribute = descr
Values of the origAttribute depend on the type of application
using the attribute mapping feature.
Default Value:
By default, attributes that are used by a DUA service are not
mapped unless mapped by the attributeMap attributes. The DUA
MUST NOT map an attribute unless it is explicitly defined by
an attributeMap attribute.
Other attribute notes:
When an attribute is mapped to the special keystring "*NULL*",
the DUA MUST NOT request that attribute from the DSA, when
performing a search or compare request. If the DUA is also
capable of performing modification on the DSA, the DUA MUST
NOT attempt to modify any attribute which has been mapped to
"*NULL*".
It is assumed the serviceID is unique to a given service
within the scope of the DSA.
A DUA SHOULD support attribute mapping. If it does, the fol-
lowing additional rules apply:
1) The list of attributes that are allowed to be mapped SHOULD
defined by the service.
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2) Any supported translation of mapping from attributes of
dis-similar syntax SHOULD also be defined.
3) If an attribute may be mapped to multiple attributes the
DSA SHOULD define a syntax or usage statement for how the new
attribute value will be evaluated. Furthermore, the resulting
syntax, through translation, of the combined attributes MUST
be the same as the attribute being mapped.
4) A DUA MUST support mapping of attributes using the attri-
bute OID. It SHOULD support attribute mapping based on the
attribute name.
5) The naming attribute SHOULD NOT be mapped using one to many
mapping.
6) Mapping should only be applied to the target entries being
searched. Attribute mapping should not be applied to parents
of the target entries.
7) Attribute mapping is not recursive. In other words, if an
attribute has been mapped to a target attribute, that new tar-
get attribute MUST NOT be mapped to a third attriubte.
Example:
Suppose a DUA is acting on behalf of an email service. By
default the "email" service uses the "mail", "cn" and "sn"
attributes to discover mail addresses. However, the email
service has been deployed in an environment that uses "employ-
eeName" instead of "cn." And also instead of using the "mail"
attribute for email addresses, the "email" attribute is used
for that purpose. In this case, the attribute "cn" can be
mapped to "employeeName," allowing the DUA to perform searches
using the "employeeName" attribute as part of the search
filter, instead of "cn". And "mail" can be mapped to "email"
when attempting to retreive the email address. This mapping
is performed by adding the attributeMap attributes to the con-
figuration profile entry as follows (represented in [LDIF]):
attributeMap: email:cn=employeeName
attributeMap: email:mail=email
DUAs MAY also map a single attribute to multiple attributes.
When mapping a single attribute to more than one attribute,
the new syntax or usage of the mapped attribute must be int-
rinsically defined by the DUAs service.
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attributeMap: email:cn=firstName lastName
In the above example, the DUA creates the new value by gen-
erating space separated string using the values of the mapped
attributes. In this case, a special mapping must be defined
so that a proper search filter can be created. For futher
information on this example, please refer to section 9.
Another possibility for multiple attribute mapping might come
in when constructing returned attributes. For example,
perhaps all email addresses are of a guarenteed syntax of
"uid@domain". And in this example, the uid and domain are
attributes in the directory. The email service may define
that if the "mail" attribute is mapped to two different attri-
butes, it will construct the email address as a contactination
of the uid and domain attributes, placing the "@" character
between them.
attributeMap: email:mail=uid domain
5.1.8 Interpreting the searchTimeLimit attribute
Interpretation:
The searchTimeLimit attribute defines the maximum time, in
seconds, that a DUA should spend performing a search request
request.
Syntax:
Defined by 1.3.6.1.4.1.1466.115.121.1.27.
Default Value:
If the searchTimeLimit attribute is not defined or is zero,
the search time limit is not enforced by the DUA.
Other attribute notes:
This timelimit only includes the amount of time required to
perform the LDAP search operation. If other operations are
required, those operations do not need to be considered part
of the search time. See bindTimeLimit for the LDAP bind
operation.
5.1.9 Interpreting the bindTimeLimit attribute
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Interpretation:
The bindTimeLimit attribute defines the maximum time, in
seconds, that a DUA should spend performing an LDAP bind
request against each server on the preferredServerList or
defaultServerList.
Syntax:
Defined by 1.3.6.1.4.1.1466.115.121.1.27.
Default Value:
If the bindTimeLimit attribute is not defined or is zero, the
bind time limit is not enforced by the DUA.
Other attribute notes:
This time limit only includes the amount of time required to
perform the LDAP bind operation. If other operations are
required, those operations do not need to be considered part
of the bind time. See searchTimeLimit for the LDAP search
operation.
5.1.10 Interpreting the followReferrals attribute
Interpretation:
If set to TRUE, the DUA SHOULD follow any referrals if
discovered.
If set to FALSE, the DUA MUST NOT follow referrals.
Syntax:
Defined by 1.3.6.1.4.1.1466.115.121.1.7.
Default Value:
If the followReferrals attribute is not set or set to an
invalid value the default value is TRUE.
5.1.11 Interpreting the profileTTL attribute
Interpretation:
The profileTTL attribute defines how often the DUA SHOULD re-
load and reconfigure itself with using the corresponding
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configuration profile entry. The value is represented in
seconds. Once a DUA reloads the profile entry, it SHOULD re-
configure itself with the new values.
Syntax:
Defined by 1.3.6.1.4.1.1466.115.121.1.27.
Default Value:
If not specified the DUA MAY use its own reconfiguration pol-
icy.
Other attribute notes:
If the profileTTL value is zero, the DUA SHOULD NOT automati-
cally re-load the configuration profile.
5.1.12 Interpreting the objectclassMap attribute
Interpretation:
A DUA MAY perform objectclass mapping for all LDAP operations
performed for a service which has an objectclassMap entry.
Because objectclass mapping is specific to each service within
the DUA, a "serviceId" is required as part of the
objectclassMap syntax. I.E. Not all DUA services should
necessarily perform the same objectclass mapping.
Objectclass mapping should be used in conjunction with attri-
bute mapping to map the required schema by the service to an
equivalent schema that is available in the directory.
Objectclass mapping may or may not be required by a DUA. In
general, the objectclass attribute is used primarily in search
filters. If a service search descriptor is provided, it is
expected that the search filter contains a "correct" search
filter, that does not need to be re-mapped. However, when the
service search descriptor is not provided, and the default
search filter for that service contains the objectclass attri-
bute, that search filter may be re-defined by the objectclass
mapping, if it applies to the default search filter. If a
default search filter is not used, it SHOULD be re-defined
through the serviceSearchDescriptor. If a serviceSear-
chDescriptor is defined for a particular service, it MUST NOT
be re-mapped by either the objectclassMap or attributeMap
values.
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One condition where the objectclassMap SHOULD be used is when
the DUA is providing gateway functionality. In this case, the
DUA is acting on behalf of another service, which may pass in
a search filter itself. In this type of DUA, the DUA may
alter the search filter according to the appropriate attribu-
teMap and objectclassMap values.
Syntax:
objectclassMap = serviceId ":" origObjectclass "="
objectclass
origObjectclass = objectclass
objectclass = keystring
Values of the origObjectclass depend on the type of DUA Ser-
vice using the objectclass mapping feature.
Default Value:
The DUA MUST NOT remap an objectclass unless it is explicitly
defined by an objectclassMap attribute.
Other attribute notes:
A DUA SHOULD support objectclass mapping. If it does, the DUA
MUST support mapping of objectclasses using the objectclass
OID. It SHOULD support objectclass mapping based on the
objectclass name.
It is assumed the serviceID is unique to a given service
within the scope of the DSA.
Example:
Suppose a DUA is acting on behalf of an email service. By
default the "email" service uses the "mail", "cn" and "sn"
attributes to discover mail addresses in entries created using
inetOrgPerson objectclass [16]. However, the email service
has been deployed in an environment that uses entries created
using "employee" objectclass. In this case, the attribute
"cn" can be mapped to "employeeName", and "inetOrgPerson" can
be mapped to "employee", allowing the DUA to perform LDAP
operations using the entries which exist in the directory.
This mapping is performed by adding attributeMap and
objectclassMap attributes to the configuration profile entry
as follows (represented in [LDIF]):
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attributeMap: email:cn=employeeName
objectclassMap: email:inetorgperson=employee
5.1.13 Interpreting the defaultSearchScope attribute
Interpretation:
When a DUA needs to search the DSA for information, this
attribute provides the "scope" for the search. This parameter
can be overridden by the serviceSearchDescriptor attribute.
See section 5.1.6.
Syntax:
scopeSyntax = "base" | "one" | "sub"
Refer to implementation notes in section 5.2 for additional
syntax requirements for the credentialLevel attribute.
Default Value:
The default value for the defaultSearchScope SHOULD be defined
by the DUA service. If the default search scope for a service
is not defined then the scope should be for the DUA to perform
a subtree search.
5.1.14 Interpreting the serviceAuthenticationMethod attribute
Interpretation:
The serviceAuthenticationMethod attribute defines an ordered
list of LDAP bind methods to be used when attempting to con-
tact a DSA for a particular service. Interpretation and used
of this attribute is the same as 5.1.4, but specific for each
service.
Syntax:
svAuthMethod = service ":" method *(";" method)
Note: Although multiple authentication methods may be speci-
fied in the syntax, at most one of each type is allowed.
Default Value:
If the serviceAuthenticationMethod attribute, or follow its
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default if not provided.
Other attribute notes:
Determining how the DUA should bind to the DSAs also depends
on the additional configuration attributes, credentialLevel,
serviceCredentialLevel and bindTimeLimit. Please review sec-
tion 5.2 for details on how to properly bind to a DSA.
Example:
authenticationMethod: email:tls:simple;sasl/DIGEST-MD5
5.1.15 Interpreting the serviceCredentialLevel attribute
Interpretation:
The serviceCrredentialLevel attribute defines what type(s) of
credential(s) the DUA should use when contacting the DSA for a
particular service. Interpretation and used of this attribute
are the same as 5.1.5.
Syntax:
svCredentialLevel = service ":" level *(space level)
Refer to implementation notes in section 5.2 for additional
syntax requirements for the credentialLevel attribute.
Note: Although multiple credentialLevels may be specified in
the syntax, at most one of each type is allowed.
Default Value:
If the serviceCredentialLevel attribute is not defined, the
DUA MUST examine the credentailLevel attribute, or follow its
default if not provided.
Other attribute notes:
Determining how the DUA should bind to the DSAs also depends
on the additional configuration attributes, serviceAuthentica-
tionMethod, authenticationMethod and bindTimeLimit. Please
review section 5.2 for details on how to properly bind to a
DSA.
Example:
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serviceCredentialLevel: email:proxy anonymous
5.2 Binding to the Directory Server
The DUA SHOULD use the following algorithm when binding to the
server:
[EDITORS NOTE: this section likely to change]
for (host in hostnames) [Note 1]
for (clevel in credentialLevel) {
if (clevel is anonymous)
return success [Note 2]
for (amethod in authMethod) {
if (amethod is none)
return success [Note 2]
authenticate to host, using amethod and clevel
if (authentication failed with bad credential)
try next clevel
if (authentication passed)
return success
}
}
Note 1: hostnames is the list of server to contact as defined
in 5.1.1 & 5.1.2.
Note 2: In case of anonymous or none, the DUA MAY try
contacting the server to ensure the directory server
is available and responding to requests.
6. Security Considerations
The profile entries MUST be protected against unauthorized modifi-
cation. Since the profile is most useful if its content is avail-
able broadly, it is recommended that the profile entries will be
readable anonymously. However, ultimately each service needs to
consider implications of providing its service configuration as
part of this profile and limit access to the profile entries
accordingly. Additionally, the management of the authentication
credentials for the DUA is outside the scope of this document and
needs to be handled by the DUA.
7. Acknowledgments
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There were several additional authors of this document. However we
chose to represent only one author per company in the heading.
From Sun we also would like to acknowledge Roberto Tam for his
design work on Sun's first LDAP name service product and his input
for this document. From Hewlett-Packard we'd like to acknowledge
Dave Binder for his work architecting Hewlett-Packard's LDAP name
service product as well as his design guidance on this document.
We'd also like to acknowledge Grace Lu from HP, for her input and
implementation of HP's configuration profile manager code.
8. References
[1]
M. Wahl, H. Alvestrand, J. Hodges, R. Morgan, "Authentication
Methods for LDAP", RFC 2828, May 2000
[2]
M. Wahl, A. Coulbeck, T. Howes, S. Kille, "Lightweight Directory
Access Protocol (v3): Attribute Syntax Definitions", RFC 2252,
December 1997.
[3]
M. Wahl, S. Kille, T. Howes, "Lightweight Directory Access Protocol
(v3): UTF-8 String Representation of Distinguished Names", RFC
2253, December 1997.
[4]
T. Howes, "The String Representation of LDAP Search Filters", RFC
2254, December 1997.
[5]
T. Howes, M. Smith, "The LDAP URL Format", RFC 2255, December 1997.
[6]
T. Berners-Lee, L. Masinter, M. McCahill, "Uniform Resource Loca-
tors (URL)", RFC 1738, December 1994.
[7]
J. Meyers, "Simple Authentication and Security Layer [SASL]", RFC
2222, October 1997
[8]
M. Wahl, "A Summary of the X.500(96) User Schema for use with
LDAPv3", RFC 2256, December 1997.
[9]
T. Berners-Lee, R. Fielding, R. Fielding, "Uniform Resource
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Identifiers (URI): Generic Syntax", RFC 2396, August 1998.
[10]
R. Hinden, B. Carpenter, L. Masinter, "Format for Literal IPv6
Addresses in URL's, RFC 2732, December 1999.
[11]
P. Leach, C. Newman, "Using Digest Authentication as a SASL Mechan-
ism", RFC 2831, May 2000
[12]
J. Hodges, R. Morgan, M. Wahl, "Lightweight Directory Access Proto-
col [v3]: Extension for Transport Layer Security", RFC 2830, May
2000
[13]
Microsoft Corporation, "Services for Unix 2.0",
http://www.microsoft.com/WINDOWS2000/sfu/default.asp
[14]
L. Howard, "An Approach for Using LDAP as a Network Information
Service", RFC 2307, March 1998.
[15]
S. Bradner, "Key Words for use in RFCs to Indicate Requirement Lev-
els", RFC 2119, March 1997.
[16]
M. Smith, "Definition of the inetOrgPerson LDAP Object Class", RFC
2789, April 2000
[RFC2251]
M. Wahl, T. Howes, S. Kille, "Lightweight Directory Access Protocol
(v3)", RFC 2251, December 1997.
[LDIF]
G. Good, "The LDAP Data Interchange Format (LDIF) - Technical
Specification", RFC 2849, June 2000.
9. Examples
In this section we will describe a fictional DUA which provides one
service, called the "email" service. This service would be similar
to an email client that uses an LDAP directory to discover email
addresses based on a textual representation of the recipient's col-
loquial name.
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This email service is defined by default to expect that users with
email addresses will be of the "inetOrgPerson" objectclass type
[16]. And by default, the "email" service expects the colloquial
name to be stored in the "cn" attribute, while it expects the email
address to be stored in the "mail" attribute (as one would expect
as defined by the inetOrgPerson objectclass.)
As a special feature, the "email" service will perform a special
type of attribute mapping, when performing searches. If the "cn"
attribute has been mapped to two or more attributes, the "email"
service will parse the requested search string and map each white-
space separated token into the mapped attributes, respectively.
The default search filter for the "email" service is
"(objectclass=inetOrgPerson)". The email service also defines that
when it performs a name to address discovery, it will wrap the
search filter inside a complex search filter as follows:
(&(<filter>)(cn~=<name string>)
or if "cn" has been mapped to multiple attributes, that wrapping
would appear as follows:
(&(<filter>)(attr1~=<token1>)(attr2~=<token2>)...)
The below examples show how the "email" service builds it search
requests, based on the defined profile. In all cases, the
defaultSearchBase is "o=airius.com" and the defaultSearchScope is
undefined.
In addition, for all examples, we assume that the "email" service
has been requested to discover the email address for "Jane Hernan-
dez."
Example 1:
serviceSearchDescriptor: email:"ou=marketing,"
base: ou=marketing,o=airius.com
scope: sub
filter: (&(objectclass=inetOrgPerson)(cn~=Jane Hernandez))
Example 2:
serviceSearchDescriptor: email:"ou=marketing,"?one?
(&(objectclass=inetOrgPerson)(c=us))
attributeMap: email:cn=2.5.4.42 sn
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Note: 2.5.4.42 is the OID that represents the "givenName"
attribute.
In this example, the email service performs <name string> parsing
as described above to generate a complex search filter. The above
example results in one search.
base: ou=marketing,o=airius.com
scope: one
filter: (&(&(objectclass=inetOrgPerson)(c=us))
(2.5.4.42~=Jane)(sn~=Hernandez))
Example 3:
serviceSearchDescriptor: email:ou=marketing,"?base
attributeMap: email:cn=name
This example is invalid, because either the quote should have been
escaped, or there should have been a leading quote.
Example 4:
serviceSearchDescriptor: email:ou=\mar\\keting,\"?base
attributeMap: email:cn=name
base: ou=\mar\keting,"
scope: base
filter (&(objectclass=inetOrgPerson)(name~=Jane Hernandez))
Example 5:
serviceSearchDescriptor: email:ou="marketing",o=supercom
This example is invalid, since the quote was not a leading quote,
and thus should have been escaped.
Example 6:
serviceSearchDescriptor: email:??(&(objectclass=person)
(ou=Org1 \\(temporary\\)))
base: o=airius.com
scope: sub
filter: (&((&(objectclass=person)(ou=Org1 \(Temporary\)))
(cn~=Jane Henderson)))
Example 7:
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serviceSearchDescriptor: email:"ou=funny?org,"
base: ou=funny?org,o=airius.com
scope: sub
filter (&(objectclass=inetOrgPerson)(cn~=Jane Hernandez))
10. Author's Addresses
Luke Howard
PADL Software Pty. Ltd.
PO Box 59
Central Park Vic 3145
Australia
EMail: lukeh@padl.com
Bob Joslin
Hewlett-Packard Company
19420 Homestead RD MS43-LF
Cupertino, CA 95014
USA
Phone: +1 408 447-3044
EMail: bob_joslin@hp.com
Morteza Ansari
Sun Microsystems, Inc.
901 San Antonio RD MS MPK17-203
Palo Alto, CA 94303
USA
Phone: +1 650 786-6178
EMail: morteza.ansari@sun.com
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