Month: August 2014

Anatomy of an LDAP Filter

LDAP filters are searches. Equality tests are supported for any attribute — attribute=value. Most attributes are case insensitive (but check your schema definition to verify!), and you can perform both exact matches (attribute=value) and sub-string matches (attribute=value*). While you will see * used in substring searches, LDAP filters do not support regex pattern matching. Some attributes support greater than and less than comparisons as well. A filter like (modifyTimestamp>=20140811000000Z) finds any object modified since 11 August 2014. This is useful when you are processing directory records and don’t want to look at any that haven’t changed since the last time your batch ran.

Tests are combined using Boolean operators. The three operators — AND (&), OR (|), and NOT (|) can be grouped and nested within parenthesis to from complex queries.

Your directory may support extensible matching — Active Directory does not. You may be able to find objects in the OUName OU using “ou:dn:=OUName”.

Your directory may support approximate matching — find close matches using “givenName=~Tim” where Tim and Timmy are returned.

To better understand an LDAP filter, decompose it into its sub-components. An example filter is:


This filter becomes


The three sub-groups are AND’d — for an object to match the filter, it must meet all three sets of criterion.

Then decompose the first of the three sub-groups.


This group uses an OR operator — the value of the uid attribute needs starts with e0 OR the value of the uid attribute starts with n9. You don’t need to use the same attribute in with the OR operator. I could use (|(st=OH)(title=Engineer)) to find all records where st is OH or title is Engineer.

The second sub-group has a single sub-component. The filter (homeDirectory=*) means “the value of homeDirectory is not NULL”. There is a NOT operator around the comparison — so we have the value of homeDirectory is NULL.

Decomposing the third sub-group:


This group uses an OR operator — the value of memberOf is cn=group1,ou=groups,o=example OR the value of memberOf is cn=group2,ou=groups,o=example

The complete filter, then, finds records where

the value of the uid attribute needs starts with e0 OR the value of the uid attribute starts with n9


the value of homeDirectory is NULL


the value of memberOf is cn=group1,ou=groups,o=example OR the value of memberOf is cn=group2,ou=groups,o=example


Bulk LDAP Operations

LDIF – Directory Import and Export using LDIFDE.EXE and LDAPMODIFY


You can obtain ldifde.exe from any existing domain controller – copy \\dcname\c$\winnt\system32\ldifde.exe  to your SYSTEM32 folder. The ldapmodify command is part of the openldap-clients package on Linux. Windows builds of the openldap clients are available. The data being imported is essentially the same, just the command line to invoke the program differs.

Using LDIF files to update LDAP data is facilitated if you know the directory schema attributes, especially those associated to the user object class.  Active Directory schema is well documented on MSDN – base Active Directory schema can be found at and the extensions made by Exchange are documented at

LDIFDE is a command line program which runs with currently logged on user’s credentials – this means that your ID can write changes to AD using LDIFDE.  Please do not play with this program in the production Active Directory domain but rather test writing to a test domain.


LDIF Export

Exporting directory information is fairly straight forward:


ldifde –f filename.txt –d “ou=base,DC=windstream,DC=com” –p subtree –r “(&(attribute=value)(otherattribute=othervalue))” –s –l “attribute1, attribute2, attribute3 …”


-f File to contain exported data
-d Search base
-p Search scope
-r RFC-2254 compliant filter
-s Domain controller from which to obtain data
-l Attributes to be returned (eliding this command will return values for all attributes)


This will create a file named ljlexport.txt of all e####### users with email addresses whose accounts are located under WINDSTREAM.COM\WINDSTREAM\IT.  The file will contain, for each user, their logon ID (sAMAccountName), email address (mail), account status (userAccountControl), display name, and telephone number.

ldifde –f ljlexport.txt –d “ou=IT,ou=windstream,DC=windstream,DC=com” –r “(&(sAMAccountName=e*)(mail=*))” –s –l “sAMAccountName, mail, userAccountControl, displayName, telephoneNumber”


-r specifies the search filter and can become a rather complex query depending on what you are looking for — & is an AND filter, | is an OR filter.  ! can be used to find unmatched values and * works as a wildcard

“(&(mail=*)(!sAMAccountName=n99*))”        find all mail enabled accounts which are not N99’s for instance.

“(&(sAMAccountName=e0*)(!(employeeID=*)))”      Find all employee accounts with no employee ID specified

“(&(mail=*)(|(sAMAccountName=n99*)(sAMAccountName=g99*)))”            mail enabled accounts which are either n99’s or g99’s

“(&(objectClass=user)(objectCategory=person))”        Real user accounts, objectClass=user alone will return a lot of things you don’t believe are users J

“(&(objectClass=user)(objectCategory=person)(telephoneNumber=813*))”     Real user accounts with phone numbers in the 813 area code

“(&(objectClass=user)(objectCategory=person)(msExchHomeServerName=*SCARLITNT841))”       Real user with mailboxes on SCARLITNT841


-d specifies the search base (subtree search by default) – you can use “DC=windstream,DC=com” to get the entire directory or something like “ou=Central,ou=windstream,DC=windstream,DC=com” to just get users within the Central OU.


LDIF Import

Importing Directory Information is not so straight forward and again do not play with this program in the production Active Directory domain.  You need to create an ldif import file to make changes to objects.  A sample file content:

dn: cn=Landers\, Lisa,ou=GPOTest,ou=IT,ou=windstream,dc=windstreamtest,dc=com
changetype: modify
add: proxyAddresses
replace: telephoneNumber
telephoneNumber: 501-905-4305
delete: mobile
mobile: 501-607-3750
delete: facsimileTelephoneNumber
dn: cn=Ahrend\, Sam,ou=IT,ou=windstream,dc=windstreamtest,dc=com
changetype: modify
replace: mDBUseDefaults
mDBUseDefaults: FALSE
replace: mDBStorageQuota
mDBStorageQuota: 190000
replace: mDBOverQuotaLimit
mDBOverQuotaLimit: 200000

Provided you have an import file, the syntax of the command is ldifde –i –v –k –y –f filename.txt  


-i LDIFDE import operation
-v Produce verbose output
-k Ignore constraint violations (and entry exists errors on add)
-y Lazy commit
-f File name to be imported



Changetype Add

A changetype of add is used when the entire object does not currently exist – this ldap operation creates a new object with the attributes specified in the stanza.


dn: cn=TestingGroup 10001,ou=testing,ou=it,DC=windstream,DC=com
changetype: add
cn: TestingGroup 10001
distinguishedName: cn= TestingGroup 10001,ou=testing,ou=it,DC=windstream,DC=com
name: TestingGroup10001
sAMAccountName: TestingGroup10001
objectClass: group
objectCategory: CN=Group,CN=Schema,CN=Configuration,DC=windstream,DC=com
groupType: -2147483646
managedBy: cn=Landers\, Lisa,OU=GPOTest,ou=IT,OU=WINDSTREAM,DC=windstream,DC=com
member: cn=Landers\, Lisa,OU=GPOTest,ou=IT,OU=WINDSTREAM,DC=windstream,DC=com
member: cn=Ahrend\, Sam, ou=IT,OU=WINDSTREAM,DC=windstream,DC=com
legacyExchangeDN: /o=WINDSTREAMEXCH/ou=First Administrative Group/cn=Recipients/cn=TestingGroup10001
mailNickname: TestingGroup10001
reportToOriginator: TRUE


This example will create an e-mail enabled global security group named “TestingGroup 10001” under – it – testing.  Both Sam and I will be listed as members of  the group and I will be listed as the group owner.  Add operations can be chained together with just a blank line between them should you need to add multiple objects in batch.


Any mandatory attributes for the schema classes need to be included (handled by ldifde works too) or the add operation will fail.  Attributes not valid for the object classes will cause the operation to fail as well.  If an object already exists, no change will be made even if some of the attributes specified differ from the values within AD.


Changetype Delete

Delete is used to delete the entire object – so be extra careful here.  The syntax is quite simple – the DN of the object to be removed and a line that says “changetype: delete”.  Again, multiple operations can be chained together with just a blank line.


dn: cn=TestingGroup 10002,ou=testing,ou=it,DC=windstream,DC=com
changetype: delete
dn: cn=TestingGroup 10003,ou=testing,ou=it,DC=windstream,DC=com
changetype: delete
dn: cn=TestingGroup 10004,ou=testing,ou=it,DC=windstream,DC=com
changetype: delete
dn: cn=TestingGroup 10005,ou=testing,ou=it,DC=windstream,DC=com
changetype: delete

Changetype Modify

Modify is used to change attributes on an existing object.  Modify can be used to add, replace, or delete an attribute.  The example above has two different stanza’s (separated by a blank line).  Within each stanza several operations are made:


First to add another email address to the secondary email addresses.  For a multi-value attribute (member, proxyAddresses …) changetype: modify\nadd: attribute adds another value to the attribute.  For single-valued attributes modify/add will fail if a value is present.

dn: cn=Landers\, Lisa,ou=GPOTest,ou=IT,ou=windstream,DC=windstream,DC=com
changetype: modify
add: proxyAddresses

The next operation replaces the telephone number with the value specified – this will overwrite the existing value.  Be careful not to replace multi-value attributes

replace: telephoneNumber
telephoneNumber: 501-905-4305

The next operation deletes the mobile phone number with the value specified – if the value does not match, a change is not made.  This can be used as a failsafe, in this case only delete my mobile telephone number if the value is what I expect it to be, or to remove entries from multi-value attributes.  Delete the member of the group which is the specific member listed without changing the other group members, for instance.

delete: mobile
mobile: 501-607-3750

The next operation deletes the fax number – regardless of content the value is removed.

delete: facsimileTelephoneNumber

A blank line separates the two stanzas and a new object is specified.  Again the modify/replace option is used which will change the attributes to the values specified.

dn: cn=Ahrend\, Sam,ou=IT,ou=windstream,DC=windstream,DC=com
changetype: modify
replace: mDBUseDefaults
mDBUseDefaults: FALSE
replace: mDBStorageQuota
mDBStorageQuota: 190000
replace: mDBOverQuotaLimit
mDBOverQuotaLimit: 200000
dn: cn=Landers\, Lisa,ou=IT,ou=windstream,DC=windstream,DC=com
changetype: modify
replace: mDBUseDefaults
mDBUseDefaults: TRUE

Changetype ModDN
ModDN changes the object’s distinguishedName.  This is interesting as it can be used to move users – this example would move my account into the Central OU under ACI

dn: CN=Landers\, Lisa,OU=GPOTest,OU=IT,OU=WINDSTREAM,,DC=windstream,DC=com
changetype: moddn
newrdn: CN= Landers \, Lisa,OU=Central,OU=WINDSTREAM,DC=windstream,DC=com
deleteoldrdn: 1


ModDN can also be used to rename the object’s display in administrative listings:

dn: CN=Landers\, Lisa,OU=GPOTest,OU=IT,OU=WINDSTREAM,,DC=windstream,DC=com
changetype: moddn
newrdn: CN= Landers\, Jane, OU=GPOTest,OU=IT,OU=WINDSTREAM,,DC=windstream,DC=com
deleteoldrdn: 1

You would of course want to modify/replace at least givenName and displayName on the object dn to avoid confusion – otherwise my middle name would appear in active directory users and computers but my first name in Outlook.  I would modify the attributes first – if you modify the DN first, you need to remember to use the new DN for subsequent attribute value changes.

dn: CN=Landers\, Lisa,OU=GPOTest,OU=IT,OU=WINDSTREAM,,DC=windstream,DC=com
changetype: modify
replace: givenName
givenName: Jane
replace: displayName
displayName: Landers, Jane
dn: CN=Landers\, Lisa,OU=GPOTest,OU=IT,OU=WINDSTREAM,,DC=windstream,DC=com
changetype: moddn
newrdn: CN= Landers\, Jane, OU=GPOTest,OU=IT,OU=WINDSTREAM,,DC=windstream,DC=com
deleteoldrdn: 1

Microsoft Directories – NT and Windows 2000/2003/2008/2012

Windows NT provided a limited repository for user id’s and passwords.  NT domain credentials had the advantage of providing single-sign-on access to other Microsoft resources such as file shares and Exchange.  Exchange itself housed a secondary directory, used for the “global address list” type details for Exchange accounts.  Address, phone number, manager, email addresses … basically anything other than the user’s ID and password were stored within the Exchange directory.  The Exchange directory then linked each account into an NT4 domain user account for logon credentials.

With Windows 2000, Microsoft integrated the two directories into Active Directory.  This allowed a more robust set of user details to be provided – and moved the LDAP compliant directory off the Exchange server onto the domain controllers.  Major changes were introduced in Active Directory – an increased maximum object count (from 40,000 to ten million in a single domain with a billions of objects in an AD forest), multi-master architecture, and attribute level replication being some of the key changes.

Data Store

Active Directory data is stored in ntds.dit.  ESE (extensible storage engine) is used to access the data within the database.  In addition to ntds.dit, there are several peripheral database files – edb.log is the current in-use transaction log file.  EDB#####.log may be present if the edb.log file has been filled.  EDB.CHK is the checkpoint file – this keeps track of which transactions have been committed to ntds.dit and a crash of the system will cause the transaction logs to be replayed from the pointer referenced in the chk file.  Res1.log and res2.log, ten meg in total, are placeholder files just in case should the server run out of disk space the files are removed to allow continued operation.

Within NTDS.DIT there are two main tables:

  • The link table – metadata for calculating linked values
  • The data table – actual domain data

There are four other tables about which no additional information will be provided here-in

  • System Table – metadata for the DSA-defined tables and indices
  • HiddenTable – DSA metadata
  • SDPropTable – Transiently stores Security Descriptor propagation, records are removed from table as propagation completes
  • MSysDefrag1 – ESE database table, not specific to AD

For linked attributes, the backlinked attribute is not modified directly but rather determined when it is queried.  As an example – Active Directory generates a reporting structure.  An object has a manager, but the “reports” listing is calculated based on object’s managers.  The linkID of a forward link attribute is always even and it’s associated backlinked attribute is always the forward linkID plus one (consequently also always odd).  A full list of forward/back link pairs can be generated by looking at the linkID values.

The data table contains three different naming contexts – the schema, the configuration, and the domain data.  These correspond to the three partitions shown in REPLMON – “cn=schema,cn=configuration,dc=windstream,dc=com”, “cn=configuration,dc=windstream,dc=com”, and “dc=windstream,dc=com”.  The term partition in Active Directory is used to indicate a naming context – in no way related to Novell’s use of the term to indicate a replication boundry.

The schema and configuration partitions are replicated to all domain controllers in a forest – since we only have one tree in the forest rendering the point moot since all the domain controllers in the domain are also all the domain controllers in the forest.  The domain partition is replicated to all domain controllers in the domain.


Active Directory – Schema

Microsoft’s documentation on unmodified schema classes and attributes can be found at   The modifications Exchange makes to the AD schema can be found at

The schema management MMC is not automatically available on a Windows machine.  To enable the snap-in, run regsvr32 c:\winnt\system32\schmmgmt.dll – then “Active Directory Schema” will be an option when adding snap-ins to MMC

Active Directory’s schema is normally in a read-only mode and no user has rights to modify the schema.  Prior to enacting a schema change, then, you must enable schema writes and add your account to the “Schema Admins” group.  To enable schema writes, right click on the “Active Directory Schema” item in the MMC and select “Operation Master”.  Then check the box next to “The Schema may be modified on this domain controller”

When creating new schema classes or attributes, ensure you use the correct OID for our organisation.  Preferably, too, create auxiliary classes and associate the aux class with a structural class.  This prevents any vendor changes to the structural class from impacting your schema attributes.

In AD, schema changes cannot be deleted (well, it can but the process is unsupported).  An attribute can be deactivated, but it remains in the schema definition.

Active Directory – Configuration

The AD Configuration partition holds, as the name implies, configuration for the domain and some services within the domain.

  • Display Specifiers: Under the DisplaySpecifiers CN you will see multiple three digit hex number combinations.  These are codes for different languages – 409 being English. lists the codes used within the Windows internationalisation features.  Under each regional container you will find the actual display specifier for structural schema objects.  On, for instance, the user-Display object, is defined what appears when you right-click a user object in Active Directory Users and Computers.  Another attribute defines the pages which appear when you create a user and the order in which those pages appear.  The createDialog attribute is of particular interest – we modify this to automatically create the display name as lastname, firstname MI if you manually create a user within AD.  This is done by defining the createDialog value as “%<sn>, %<givenName> %<initials>”
  • Extended Rights:  On the controlRightsAccess object, appliesTo defines structural schema objects to which the controlRightsAccess object applies.  The controlRightsAccess objects themselves have several functions.
    • When validAccesses is set to 8, this is to validate writes – or check the attribute value beyond the schema definition.  Implementation is not widespread.
    • When validAccesses is 256, then the object defines an actual extended right – something not part of the normal ACL’s.  Recieve-as and Send-As, for instance, are a special operations for Exchange which can be found in the ExtendedRights container.
    • Other validAccesses codes define ACL groups which can be assigned through the “Delegate Control” function.  and validAccesses indicates what rights the ACL group permits – 16 for read, 32 for write, and the sum of 48 for read/write access.  The membership object in ExtendedRights, with appliesTo bf967aba-0de6-11d0-a285-00aa003049e2 and validAccess of 48 means this access group allows whomever is granted it to both read and write to user objects (bf967aba-0de6-11d0-a285-00aa003049e2 is the guid of the user schema object).  On the schema object “member”, then, the rightsGUID is entered as the attributeSecurityGUID.

An example of the rights grouping is the “Personal-Information” object, rightsGUID 77B5B886-944A-11d1-AEBD-0000F80367C1.  You will find the corresponding octet string, 0x86 0xb8 0xb5 0x77 0x4a 0x94 0xd1 0x11 0xae 0xbd 0x00 0x00 0xf8 0x03 0x67 0xc1, applied to several schema attributes – telephoneNumber, facsimileTelephoneNumber, streetAddress, telexNumber, and so on:

Thus using the “Delegation Of Control” wizard, it is possible to select “Read and write Personal Information” as a permission set rather than specifying each individual attribute you want editable. Note, too, in the ACL editor the listing of “Personal Information” is retained


Under ForestUpdates you will see an “Operations” CN.  Operations holds a listing of updates made to the forest (e.g. exchange /forestprep).  This allows the system to check that the requisite forest updates are in place prior to installation without requiring the changes to be re-run.


This is basically the same thing “LostAndFound” in the domain naming context is, but within the configuration partition.  All things being equal, it should be empty.  Should an object be created within the Configuration partition at the same time it’s parent is deleted, the object is moved to “LostAndFoundConfig” for holding.


Contains crossref objects to all partitions within the forest – again not as interesting here as it could be with just one tree and domain.

Physical Locations

This is intended for use with Directory Enabled Networking.  The DEN concept is maintained by DMTF ( and is not at present implemented at Windstream


Forest-wide application settings – objects within this container correspond directly to the “Services” listed within the “Active Directory Sites And Services” snapin.  One of the services listed is Microsoft Exchange.  Should a server fail, running setup /disasterrecovery will recover most of the Exchange settings for the server from within this container.


The “Sites” of “Active Directory Sites and Services”.  IP subnets and their associated sites are defined in this container, as well as the replication partnerships between domain controllers.

WellKnown Security Principals

What I call the “virtual credentials” – system security credentials like Everyone and Self are defined herein.

Active Directory – Domain Data

Objects specific to just one domain within the forest – the obvious users, computers, printers, file shares, groups, and contacts.  Less obvious items too are stored within the domain data.  If Windows DNS zones are configured as “Active Directory Integrated”, the DNS entries will appear under “cn=MicrosoftDNS,cn=System,dc=…”.  File replication service (FRS) shares (including the domain SYSVOL), some information on Group Polices, Oracle database connections … any of the structural schema objects … can also be found within this partition.

An object named Infrastructure is in the root of the domain naming context, this object holds the NTDS settings for the domain infrastructure operations master.

Flexible Single Master Operations (FSMO) Roles

FSMO roles are assigned for functions which cannot practically be performed by any domain controller – functionality which cannot subscribe to the multi-master principal.

There are two forest-wide FSMO roles, the Domain Naming Master and the Schema Master.

  • The Schema Master is the server on which writes can be made to the schema.  All domain controllers will have a read-only copy of the schema, but only the schema master can write changes.
  • The Domain Naming Master is used when a new domain is created within a forest – it verifies the new domain has a unique name.

Three additional FSMO roles exist in each domain within a forest.  The Infrastructure Master, RID Master, and PDC Emulator.

  • The Infrastructure Master, in a multi-domain environment, handles cleanup of phantom objects created as members are added to groups via a trust.  The cleanup process is detailed by Microsoft at;EN-US;Q248047    As we have a single domain, this is somewhat immaterial.  Should we begin implementing other domains, the Infrastructure Master will need to be moved to a non-global catalogue (GC) server.  The GC functionality precludes the phantom objects from being created (and hence from being purged).
  • The RID master allocates blocks of relative ID’s, RID’s, to the domain controllers within the domain to ensure unique GUID’s.  Should the RID master be offline for a short interval, new objects can still be created until the already-allocated RID block has been exhausted.
  • The PDC emulator is multi-function.  Were the domain to be in mixed-mode and therefore support NT4 BDC’s, the PDC emulator is required by the NT4 domain controllers for backwards compatibility.  Our domain is in native-mode and cannot have NT4 BDC’s.  This does not preclude NT4 member servers, just domain controllers.  The PDC Emulator server is authoritative for the user’s password.  Any failed logons are re-checked against the PDC emulator.  In the NT4 environment this was because a BDC was a read-only directory copy to which password changes could not be made.  If you changed your password and attempted to authenticate prior to the domain replicating the change completely, you could receive an invalid password error using your correct new password.  To prevent this issue, a password failure on the BDC was re-checked with the PDC before the logon attempt was failed.  This is how we can allow CSO password changes into AD without requiring the user to wait for domain synchronisation.  The DirXML AD driver is installed to the PDC emulator server to allow immediate use of the user’s new CSO password.  Group Policy Objects are created and edited on the PDC Emulator’s SYSVOL share.  The PDC emulator is also the time source for the domain.  Our PDC emulator is configured to use as its time source with a time sync period of eight hours.

Normally you can move the FSMO roles between domain controllers using MMC’s.  For the three per-domain roles the change is made in Active Directory Users and Computers.  The Domain Naming Operation Master is changed from Active Directory Domains and Trusts”; the Schema master is changed within Active Directory Schema Manager.

Within Active Directory Users and Computers, right click the domain and select “Connect To Domain Controller” – select the domain controller which will receive the new role.  Then right click the domain and select “Operation Masters”.  You just click the “Change” button to move the role.

In the event of a catastrophic server failure complete with no system state backups you can forcibly transfer the FSMO roles from a non-operational source.  We have done this once in production, the ICM domain, but there is additional peripheral cleanup required to remove the failed domain controller from operation. contains instructions for seizing FSMO roles.  Microsoft mostly documents the domain cleanup process at   If you want to try it for the experience, build two servers, create a fake domain with the two of them, turn one off and seize all the roles onto the remaining machine.  This is effectively what happened in the ICM domain, they had three domain controllers but the first which held all roles was destroyed.  Be careful in production as the post-seizure cleanup is not fully documented.  DNS entries will still exist in BIND.  It is possible for your domain controller machine password to be out of sync with the domain.  I’m sure there are other situations which could arise as well which we didn’t happen across.

Domain Registration – WINS

The WINS entries of your domain should only be used by ‘legacy’ clients, NT4 workstations and servers.  If you configure your domain controllers TCP/IP properties to use your WINS servers, the registration for the domain will be created automatically.  Alternately you can create an LMHOST file for import into a foreign WINS server.  The only reason we do this is to establish a trust with an NT4 domain.  There are two records needed – and for our domain the text is included here-in.       SCARLITNT631         #DOM:ALLTEL          #PRE       "ALLTEL         \0x1b"  #PRE

If you are attempting to create the LMHOST file for an alternate domain, you can just change the values except the “ALLTEL         \0x1b” entry.  There is a quotation mark, sixteen characters only (insert holy hand grenade like joke here) followed by the \0x1b then the closing quotation mark.  If your domain name is BOB you cannot replace ALLTEL with BOB, you need to replace it with BOB and three trailing space characters.

Domain Registration – DNS

There are four “underscore zones” – new DNS zones used to store the SRV records relevant to the domain. Active Directory works fine with BIND DNS servers – you need to allow dynamic updates from the domain controller IP addresses. Since I do not allow dynamic updates on the root zone, I manually add the domain controller A records.

  • _sites.domain.tld.   Service records advertise servers providing global catalogue, Kerberos, and LDAP services within each site.  The sites are differentiated within the record name – _service._tcp.SITENAME._sites.domain.tld.    The following lines are the _sites records for the TWNUserAuth site
_gc                               SRV     0 100   3268
_kerberos                         SRV     0 100   88
_ldap                             SRV     0 100   389
_gc                               SRV     0 100   3268
_kerberos                         SRV     0 100   88
_ldap                            SRV      0 100   389
  • _tcp.domain.tld. Service records advertise all domain controllers within the domain providing global catalogue, Kerberos, LDAP, and kpasswd services.  The following lines are the _tcp records for the NEOHTWNNT630 server
_gc                           SRV     0 100   3268
_kerberos                     SRV     0 100   88
_kpasswd                      SRV     0 100   464
_ldap                         SRV     0 100   389
  • _udp.domain.tld. Used for UDP kerberos connections to get tickets and change passwords.  Service records in this zone advertise the UDP Kerberos and kpasswd services for the domain.  The following lines are the _udp records for the NEOHTWNNT630 server
_kerberos                   SRV     0 100   88
_kpasswd                    SRV     0 100   464
  • _msdcs.domain.tld.  Kerberos, ldap, and global catalogue records by site and not.  In addition each domain controller’s GUID used for replication is registered here.  Again the example provides the service records for NEOHTWNNT630
47c1965e-87e8-4445-8552-fd20892c08c2    CNAME           SRV 0 100 389   
gc                      A
_kerberos                                 SRV     0 100   88
_ldap                                     SRV     0 100   389
_kerberos                                 SRV     0 100   88
_ldap                                     SRV     0 100   389
_ldap._tcp                                SRV     0 100   3268
_ldap._tcp.TWNUserAuth                    SRV     0 100   3268

The PDC emulator is also advertised here

_ldap._tcp.pdc                         SRV     0 100   389


Client Authentication

A client which has already authenticated to the domain will have a registry entry which retains the client’s site.


When a client attempts to authenticate to Active Directory, the service records for the kerberos service are used to determine an appropriate authentication source.  In the case of the PC above, this would be a query for service records is made.  An LDAP connection is initiated over udp/389 to every domain controller returned by the DNS query.  Each connection is initiated in 1/10th intervals second.  The receiving servers compare the client’s IP address to the subnet configuration to verify the client is reaching the correct site for it’s current subnet.  The first LDAP response received is then used as the kerberosauthentication server.  If the client’s site is incorrect a referral is returned for the correct site – which then prompt the client to re-query DNS for the correct new site.

Save The Humans

I am continually astounded by people who think industry should have the right to spew whatever cocktail of toxic chemicals. Bully for you, you’ve got a load of cash and can just move somewhere else. Empathy for others aside, unless you are preparing your own biodome , eventually you are going to run out of “elsewhere”.

I remember reading an article from the American South-East coast somewhere – maybe a Carolina. A local law enforcement officer was discussing how voluntary evacuations work (or don’t), and he said the most effective tool he’d found was an indelible marker. Asked anyone who wanted to remain on site when a hurricane was headed their way to use his pen and write their name on their arm. So their bloated, floating corpse could be identified. Just writing your name is morbid, and a lot of people would start packing. But the mark served as a constant reminder of your poor decision, and people would clear out a few hours later too.

We need to adapt the same idea to environmental protection. Because, let’s be honest, the planet will still be here. A lifeless rock orbiting around the sun maybe, but short of vaporizing a good chunk of the planet … it will be here. I’m not sure what the equivalent of floater ID markings would be for creating un-breathable air or caustic water, but I suspect that type of save *you* approach would be far more successful than trying to engender concern for animals, plants, or grandchildren in people who obviously have no such concern.

LDAP Directories


The International Telecommunication Union, ITU, is an organisation of the United Nations (sorry, Carra, now I guess all directories are on par with poodles) which submits recommendations for the coordination of global telecom and radio systems.  The Telecommunication Standardisation Sector, ITU-T, is the branch submits recommendations for telecommunication standards.  ITU-T was formerly known as Comité Consultatif International Téléphonique et Télégraphique, CCITT.

Published in volume eight of the 1988 CCITT Blue Book, X.500 is the recommendation for “The Directory”.  Additional recommendations X. 501, 509, 512, 518, 519, 520, 521, 525, and 530 farther defined ITU’s idea for directory service functionality.  Once ITU-T put forth the recommendation, several international standards bodies got involved, and eventually yielding the 9594-1 standard from ISO (from isos, name used by the International Organisation for Standardisation) and IEC (International Electro-technical Commission).   I’ve got the 1993 version (./ but never bothered to get the updates.

X.500 Components

Some of the terminology used within the X.500 recommendation is used in non-X.500 directories.  If you want to more about these or what they do, read the ISO/IEC standard

  • Directory Information Base (DIB) is used to store the directory data
  • Directory Information Tree (DIT) is a hierarchy within the DIB
  • Directory Service Agent (DSA) is a server which stores the DIB
  • Directory User Agent (DUA) is an application interface over which queries are made to the DSA
  • Directory Access Protocol (DAP) is the method used by the DUA to communicate with the DSA
  • Directory System Protocol (DSP) is used for communication between DSA’s
  • Directory Management Domain (DMD) contains DSA’s within an organisation
  • Directory Management Organization (DMO) is the actual organisation of the DMD
  • Directory Information Shadowing Protocol (DISP) is used to replicate information between DSA’s in a DMD
  • Directory Operational Binding Management Protocol (DOP) is policies which define the administrative information exchanged between DSA’s


X.500 directory access protocol in its actual form involves a lot of overhead we just don’t want to incur to keep a guy, his password, his address, and his phone number all available somewhere.  Lightweight Directory Access Protocol, LDAP, retains the directory structure of X.500 with a simplified TCP/IP based access protocol.  Referrals were simplified and the replication protocol generalized.

The LDAP Technical Specification Roadmap is maintained by the Internet Engineering Task Force, IETF, as RFC 4510 (  The multiple RFC’s encompassed by LDAP are included in section 1, “The LDAP Technical Specification”.

Directory Components – Schema:

Every directory has a schema set which defines its components.  The schema defines what type of objects exist in the directory and what attributes are valid for those objects.  Schema “attributes” are types of values which can be on an object – anything from an asset ID number to a vendor ID.  Schema “classes” are categories of entries which can be made – and a group of attributes that category means the object can have.  An attribute can be “mandatory” within a class – for example a user account may need a cn value, an objectClass, and an objectCategory.  You cannot make a user account without these values.  The remaining values in a class are “optional” – you may or may not have facsimileTelephoneNumber on your account.

There are three types of classes: abstract, auxiliary, and structural.  Abstract classes are classes which an object cannot directly be – cannot be the object’s objectClass – but are used through subordinate classes to define valid and required attributes..  Auxiliary classes are somewhat like abstract classes in that an object cannot be an auxclass – auxclass’s are instead ‘attached’ to structural classes to create additional valid attributes for the class.  Structural classes are the objectClass “things” you can make within the directory – a user account, a print queue, or even a replication partnership.  The semantics may vary between directory services, but the idea remains.

If you wish to add additional attributes to your objects, you need to extend the directory schema.  I will note here that Novell seems to allow undefined schema extensions.  Normally an organisation is issued an OID number (Object Identifier).  A private enterprise would normally request an OID assignment from IANA (existing assignments are published to or ANSI.  ANSI’s cost money whereas IANA’s don’t.  Guess which we use! has been issued to Alltel, has been issued to Windstream.  Additional decimal number groups past the organisation’s enterprise number can be sub-allocated within the organisation.  .5 within Alltel is used within the AD schema extensions, and 5.1 is specific to the test domain where 5.0 is specific to the production domain.  The breakout an OID number within Alltel’s production AD is:

1                              iso
1.3                            org
1.3.6                          dod                        internet                      private                    enterprise              Alltel            Alltel Active Directory          Production AD      Production AD Classes      Production AD Attributes

So (cSOBESPolicy) is an attribute within the test domain – the seventh one at that – and (alltelPerson) is a class in the production domain (the first and only one).  A different numbering scheme off the “” base should be used for other directories.

Once you have created new attributes and appended an aux-class to an existing class, you may (iPlanet, IBM LDAP) need to restart the LDAP service or you may (Active Directory) need to wait for the change to propagate.  Our customized attributes are associated to an aux-class of user called alltelPerson. 

Please do not randomly modify the schema – especially in Active Directory.  In AD you cannot remove the entries.  You can deactivate an attribute but it cannot be deleted.

Directory Components – Structure:

A directory structure will begin at its root – an “O”, organisation name, in iPlanet/NDS/IBM LDAP, or “DC”, domain component, in Active Directory.  OU’s, Organisational Units may be contained under the directory root to provide some organisation to the objects housed within the directory.  You may also see CN’s under the domain root –common name with an objectClass of container.  There may be several layers of OU’s or containers before you find the “leaf” objects – users, contacts, printers, servers, whatever.  The fully qualified LDAP syntax of an object begins at the object and ‘walks’ up the tree – “cn=e0082643,ou=core1,ou=lit,ou=ar,ou=sc,o=alltel” for my ID in the ALLTEL-TREE for example.  “Special” characters are encoded or escaped as required – “cn=Landers\, Lisa,ou=GPOTest,ou=IT,ou=ACI,dc=alltel,dc=com”

LDAP Operations

Connections to LDAP are normally made on port 389 for clear text and 636 for encrypted. (iplanet), (CSO metatree), (active directory ldap), and any NetWare 6.0+ server within the alltel-tree use these standard ports, but alternate ports can be assigned within most directory servers.

Once a connection is made, it may be possible to query the directory.  A limited set of data should be returned as any directory enumeration at this point is done under an anonymous credential.  To specify the user with which you wish to perform directory operations, a BIND must be made.

Search operations include a base and scope (where to begin the search and how deep to traverse the directory under the base), and usually a filter (what to search for) and attributes requested.  Ldapsearch.exe (Win32 available from \\\NDSSupport\softlib\misc\ldaputils\) can be used to search an LDAP compliant directory.  Ldapsearch options: -h  -b “ou=search,ou=base,dc=alltel,dc=com” –s “scope” –D “cn=user,ou=location,dc=alltel,dc=com” –W “RFC-2254 compliant filter” attributes to return go here

The search scope can be base (just the object defined as the search base), one (the search base and one level under), or sub (everything subordinate to the search base).  Eg:

ldapsearch -h -b “ou=GPOTest,ou=IT,ou=ACI,dc=alltel,dc=com” -s “one” -LLL -D “cn=Landers\, Lisa,ou=GPOTest,ou=IT,ou=ACI,dc=alltel,dc=com” -W “(&(objectClass=user)(mail=*))” displayName mail

The –W option prompts for a password, alternately -w “PasswordGoesHere” can be used.  Once a password has been supplied in this example, the display name and email address for users who have an email address will be returned:

dn: CN=ACI WWC LDS Undeliverables,OU=GPOTest,OU=IT,OU=ACI,DC=alltel,DC=com
displayName: ACI WWC LDS Undeliverables
dn: CN=bob,OU=GPOTest,OU=IT,OU=ACI,DC=alltel,DC=com
displayName: bob
dn: CN=Landers\, Lisa,OU=GPOTest,OU=IT,OU=ACI,DC=alltel,DC=com
displayName: Landers, Lisa

Additional operations to add objects, delete objects, modify objects, and modify the distinguished name of the object can be done.  More information on this will be provided later.