LDAPviewer Schema/Schemax Files

LDAPviewer provides a number of features to handle .schema files.

LDAPviewer's normal behaviour is to interrogate the LDAP server (if using LDAPv3) and to display (under the Schema tab) the currently connected LDAP server's list of available objects (ldapSyntaxes, objectClasses, attributeTypes and matchingRules) from the collections available in the subSchema entry. These collections are constructed by the LDAP server from its configured schemas. LDAPviewer uses this data to provide information about LDAP objects and to control varius aspects of its behaviour.

Schema data is not always available from the LDAP server.

Some LDAP servers limit access to subSchema information meaning this useful information may not always be available (and never in the case of LDAPv2 servers). Note: Access information including credentials may be supplied using the More DITs feature of Connection Profiles.

Not all attributes or features are available in schemas read from an LDAP server. Attributes and objectClasses may be constructed by the user and the resulting schema configured for the LDAP server. These schema files may be regarded as self documenting (even though many have raised tersness to an art form). However, many objects used or supported by the LDAP server are defined internally and are neither visible in user schemas nor are they available through the various collections maintained in subSchema (and interrogated by LDAPviewer).

In order to overcome these limitations LDAPviewer will read and parse any standard LDAP .schema file found in the Users/username/AppData/Roaming/LV/schemas/ (Windows), /home/username/LV/schemas/ (for Linux/BSD) directory or /schemas/ in the Apple bundle with a file suffix of .schema. LDAPviewer is release with a standard set of .schema files obtained from a number of distributions. The results of schema file parsing are maintained permanently and updated when a new LDAP server is connected (assuming it has or allows access to the subSchema)

In addition is can be useful to extend the avaailable descriptions with context specific information and to add descriptions about standard objects that do not appear in normals schemas, such as supportedFeatures. LDAPviewer distbutes an extended schema with the name objects.schemax to allow for this capability.

.schemax files are intended simply to supply information to the LDAPviewer user and for no other purpose. They do not, in any way, affect the operation of the LDAP server or LDAPviewer's processing of results obtained from the LDAP server. The .schemax format and syntax rules are exactly the same as those for .schema files but .schemax files support a number of additional object types and an extended DESC (X-DESC) description field and an X-NOT-CLEAR-TEXT field.

X-NOT-CLEAR-TEXT field This field allows the user to indicate that any attribute with this parameter should not be displayed in clear text (password attributes such as userPassword are already handled in this manner but the user may elect to obscure other sensitive fields from casual observation. The field uses the standard extension format defined by RFC4512 Section 4.1 and has the form:
```
X-NOT-CLEAR-TEXT 'TRUE'
```
Note: The definition of any attributetype in a .schemax file will replace that read by LDAPviewer either from a .schema file or by interrogation of the LDAP server, it is vital for the sake of completeness and accuracy that the standard object (as it appears in a .schema file) is reproduced in its entirety in the .schemax file with X-NOT-CLEAR-TEXT 'TRUE' added.
Extended X-DESC field This field is intended to provide additional descriptive material about an object or its use and/or limitation in a particular user context. The field uses the standard extension format defined by RFC4512 Section 4.1 and has the form:
```
X-DESC 'extended text or description'
```
This field may be added anywhere to any object type supported by .schema or .schemax files. Thus, if the user wishes to add descriptive material about the precise usage or limitations of an object in a specific DIT, for example, the use of the 'l' ('localityName') attribute, then that definition, in its entirety, would be added to a .schemax file and the additional X-DESC field added as shown below:
```
# standard definition of the l or locality name attribute in the core.schema file
attributetype ( 2.5.4.7 NAME ( 'l' 'localityName' ) SUP name )

# extended definition as it may appear in a .schemax file with X-DESC added
# X-DESC is position idendependent
attributetype ( 2.5.4.7 NAME ( 'l' 'localityName' ) SUP name X-DESC 'town or city of client')
```
Note: The definition of any object in a .schemax file will replace that read by LDAPviewer either from a .schema file or by interrogation of the LDAP server, it is vital for the sake of completeness and accuracy that the standard object (as it appears in a .schema file) is reproduced in its entirety in the .schemax file with X-DESC added.
ldapSyntax Designed to supply textual information about LDAP syntax objects. This definition extends the RFC4512 section 4.1.5 ldapSyntax defintion to allow the X-DESC field:
```
ldapSyntax ( OID DESC 'text' X-DESC 'extended text' )
```
Note: ldapSyntaxes are uniquely merged with those from the LDAP server since they may contain a number of X- extension fields denoting binary attributes or other special constraints. Standard ldapSyntaxes do not pemrmit a NAME field only a DESC field.
supportedExtension Designed to supply textual information about an OID that appears in a multi-valued supportedExtension attribute in the rootDSE. The format is:
```
supportedExtension ( OID X-DESC 'textual description' )
```
supportedFeature Designed to supply textual information about an OID that appears in a multi-valued supportedFeatures attribute in the rootDSE. The format is:
```
supportedFeature ( OID X-DESC 'textual description' )
```
supportedControl Designed to supply information about an OID that appears in a multi-valued supportedControl attribute in the rootDSE. The format is:
```
supportedExtension ( OID X-DESC 'textual description' )
```

The standard distribution of LDAPviewer includes a single commented objects.schemax file containing many hidden attributes used by a number of LDAP servers as well as textual information about most supportedControl, supportedFeatures and supportedExtensions attributes. This file may be either extended by the user or used as a template for additional user specific .schemax files.

The following shows a snippet from this file:

ldapSyntax ( 1.3.6.1.4.1.1466.115.121.1.4 DESC 'Audio' X-NOT-HUMAN-READABLE 'TRUE' X-DESC 'Unspecified format audio file LDAPviewer supports AIFF, AIFC, WAV, SND and AU files' )
supportedExtension (1.3.6.1.4.1.4203.1.11.1 X-DESC 'Modify Password Extended Control (RFC 3062)')
supportedFeature ( 1.3.6.1.1.14 DESC 'Modify-Increment (RFC 4525) Applies to Integer and other numeric LDAP Syntaxes' )
supportedControl ( 1.3.6.1.1.12 X-DESC 'Assertion Control (RFC4528)' )
attributetype( 1.3.6.1.4.1.4203.1.12.2.1 NAME 'configContext' DESC 'config context' X-DESC 'Defines the equivalent to namingContexts for OLC control of OpenLDAP cn=config' SYNTAX 1.3.6.1.4.1.1466.115.121.1.12
 EQUALITY distinguishedNameMatch SINGLE-VALUE NO-USER-MODIFICATION USAGE dSAOperation )
attributeType ( 1.3.6.1.4.1.4203.666.1.7 NAME 'entryCSN' DESC 'change sequence number of the entry content' EQUALITY CSNMatch ORDERING CSNOrderingMatch SYNTAX 1.3.6.1.4.1.4203.666.11.2.1{64} SINGLE-VALUE NO-USER-MODIFICATION USAGE directoryOperation )