LDAP BIND: Establishing a Connection to the Directory
Before accessing a directory service, we have to establish a technical connection with an object of the directory. This could be a directory container (e.g. an organizational unit) or a single object.
Given that the technical access is accomplished via the LDAP protocol, we use the according LDAP notation as well: Establishing a connection and logging on with respective logon information is called a Bind operation (has nothing to do with the well-known DNS server software). Many aspects of Binding are described in MSDN: MSDN Documentation of ADSI and BIND.
Unless otherwise mentioned, this topic describes bind operations always in Active Directory environments. The ADSI Interface also permits bind operations on other directory services. Corresponding examples can be found in the following topics.
Bind variations:
Bind using the user ID the script is run with
This is the easiest way of connecting. You 'grab' the object for access by using a simple GetObject-Function. At this, the ID of the user that runs the script is used automatically for authentication. This method can only be used for accesses within the own forest, if possessing sufficient permissions. In addition, the appropriate notation of the LDAP pathname needs to be considered (especially if commas or other special characters are used!)
After that, the object 'Philipp' of the OU 'Accounts' of the domain 'cerrotorre.de' can be accessed via the variable obj. However, access to all objects of a container is also possible:
Serverless Binding:
Please keep in mind that the server name can be left out in the LDAP
pathname - the station where the script runs discovers a domain controller
from the user's domain automatically (via DNS). A shortened LDAP pathname
can be used particularly when running the script directly on a domain controller:
Serverless Binding should not be used if you develop for other directory services such as Lotus Notes LDAP or eDirectory. You can not use serverless binding here.
Bind using special credentials
The common method of binding to the directory always works when a logged on user wants to access objects of his own domain respectively his own Active Directory forest. However, it might quite often be necessary to access a directory service where you are not an currently authenticated user. In that case, the bind variation OpenDSObject allows to pass the username and password and thus the logon to e.g. foreign forests is possible.
In this example the OU object of the domain company.com is accessed by logging on the server 'controller.domain.com' with the username 'administrator' and password 'P@ssw0rd'. The last parameter (1) acts as a logon-flag, ensuring a secure Kerberos logon.
ADSI
Reference in MSDN: OpenDSObject()
The username of an AD logon can be given in the following way:
| Pure logon name | e.g. 'administrator', for this, the logon-flag needs to be set to '1' (secure logon) |
| NetBIOS logon name | e.g. 'DOMAIN\administrator' |
| User principal name | e.g. 'administrator@domain.com' |
| Distinguished name | e.g. 'cn=administrator,cn=users,dc=domain,dc=com', for this, the logon-flag needs to be set to '0' (clear text logon). |
The logon flag determines the type of access. Important are the two values '0' (for encrypted logon in clear text) and '1' (for secure logon via Kerberos or NTLM). Of course, a secure logon should be preferred to clear text logon. However, situations may arise when an insecure clear text logon is needed. Especially when using a bind operation to logon to other directory services like Novell eDirectory or OpenLDAP systems, the logon-flag must be set to '0'. In order to avoid a disclosure of the password from the net, the use of LDAP-SSL is recommended - then the whole traffic of the LDAP protocol is encrypted.
Microsoft
explanations of the logon flag in MSDN
The server name can be left out in the LDAP pathname of Active Directory environments and it is automatically bind to an accessible domain controller of the own domain. Also, username and password can be provided as NULL string (''), then the logon data of the own user is used automatically. This possibility might be useless if using the bind option for the logon to another forest DC - thus, server and logon data have to be indicated accordingly.
Bind to the Global Catalog
When connecting to a domain controller by using ADSI, only data from the schema
partition, the configuration partition and
the own domain can be provided. However, if you want to request objects
of the whole forest from a single domain controller, then you have to
connect to a global catalog
(GC). Such special domain controllers provide objects from
other domains via LDAP using the special TCP port 3268.
However, these objects can only be read and simply show some (the most
important) attributes!
A technical option for the bind to a global catalog is to change the LDAP
pathname so that the TCP port number 3268 is used. This is possible
when using the function GetObject as well as OpenDSObject.
Prerequisite, of course, is that the regarding server 'server.cerrotorre.de' has been set up as a global catalog.
Here's an easier option that utilizes a special form of the pathname, where
the term 'LDAP' is simply replaced by 'GC'. So the special port number
3268 can be omitted:
A Serverless Binding can be run also when you are in Active Directory environments. Then a global catalog will automatically be searched by DNS:
Bind without knowing the own Domain / Forest name
In many cases you want to develop scripts that run in different Active Directory environments.
Think about a script that e.g. displays any information about certain objects
within the own domain or is responsible for specific changes. In order
that this script runs in any domains, you could let pass the domain name
as parameter. But it is more sophisticated to automatically identify the
current domain name by querying the Active Directory itself through severless
binding.
The relevant information can be read in a special directory entry, available
on every domain controller: the rootDSE (Root
Directory Service Entry).
You can read here the distinguished name of your own domain from the attribute
'defaultNamingContext' and make an LDAP
pathname right away with which the desired domain objects can be accessed.
This script lists all objects directly in the main name context of an Active Directory domain - it's the container where all 'normal' user and group objects are saved in. By the way, you can (given the relevant rights) access the configuration container of the forest without knowing the accurate notation, because the respective DN is documented as 'configurationNamingContext' attribute in the rootDSE.
Bind as Anonymous
LDAP generally offers the possibility to logon to a directory without any user credentials. This is the so called 'anonymous bind'. Whether this anonymous bind is allowed or not depends on the type of directory service and the current configuration. When an anonymous bind is possible, in most cases the access rights for anonymous LDAP users are quite restricted.
If you want to logon to an Active Directory directory as an anonymous user without user name and password, you have to distinguish between Windows 2000 forests and forests that operate on Windows 2003 or later.
|
AD under Windows 2000: The anonymous logon is allowed
by default. |
|
AD under Windows 2003 (and later): Initially, the anonymous access is limited to the rootDSE entry (Root Directory Service Entry). Thus, you can readout a list of naming contexts or the Active Directory version of the forest. But if trying an anonymous access to normal objects and attributes of the forest, it has to be allowed by a global switch first. This is the Active Directory attribute dsHeuristic. This value is stored as an attribute of an directory object in the configuration partition: CN=Directory Service,CN=Windows NT, CN=Services,CN=Configuration, DC=root, DC=com. The default value is 0000000, a value of 0000002 enables the anonymous access to the directory. |
Don't forget: Which objects and attributes you are allowed to access is also determined by access standards existing for the entries ANONYMOUS LOGON and Everyone in the relevant ACLs. The out-of-the-box setting these entries have absolutely no access right to domain objects - even if an anonymous logon is generally allowed by dsHeuristics.
There are some more things that need to be taken into consideration during a bind operation. An anonymous user is unable to see the content of container objects. It is inevitable to access single objects like user, groups or contacts by using the complete LDAP path. For this, the logon with the function OpenDSObject, but without user name and password, are used:
If you want to access several objects or if you don't know the precice LDAP paths, than you may run a directory search via ADO interface. The procedure of an ADO search is explained in the SelfADSI Tutorial in the topic 'Searching for objects in the directory'.
In order to run an anonymous ADO query within an Active Directory, some modifications need to be accomplished. First of all, the base DN string of the directory search is to be omitted - as an anonymous user you are unable to 'see' a directory container.
Secondly, you have to use the global catalog provider for the search, because it only allows a search without defined base string. The search starts directly with the following LDAP path:
<GC://Server>
Here is an example in which all user objects are displayed. To access other objects you just have to change the LDAP-Filter:
Please note that an ADO search to the Global Catalog returns the corresponding LDAP pathname of the whole forest (because we asked for the attribute 'ADSPath' ...). The returned LDAP pathnames of the Global Catalog are displayed with the protocol answer 'GC://', as you can see in the above script example:
You will neither be able to read all attributes nor to change / rewrite
them during a following connect to these pathnames - because you are accessing
the Global Catalog! Get more information about the handling of search results
of the Global Catalog under the topic 'The
Global Catalog' here in the SelfADSI Tutorial.
Bind to Novell eDirectory / NDS Server
If you want to bind to an Exchange 5.5 server in order to access mailbox
information or the set up of the mail organization, some things will need
to be considered.
First of all, it's important to bear in mind that a LDAP
pathname of a Novell eDirectory is different
to other Active Directories: Instead of a domain (e.g. ...,dc=cerrotorre,dc=de),
the superior hierarchy of such a directory is comprised of an organization
(...,o=...) or country object (...,c=...).
cn=PFoeckel,ou=Karlsruhe,o=CerroTorre
cn=BierSan,ou=Students,ou=Sydney,c=au
When binding, you always have to use the function OpenDSObject and
directly name the correspondent Novell server (and, if applicable, the
LDAP port number the server is set up with). Username is the complete LDAP
pathname of the user that is to be logged on. Logon
flag is always 0:
The logon via unencrypted password is quite unsecure, but if the server provides the appropriate SSL certificate settings, you could use LDAP-SSL on TCP-Port 636. Then, the whole LDAP Communication and thus username and password as well will be encrypted via a SSL tunnel.
If the logon to the eDirectory shall be anonymous, an empty string is passed over instead of username und password. Novell servers allow anonymous logon in general, but then you have got only access where the entry [Public] is existing as trustee:
Bind to an Exchange 5.5 Server
If you want to connect to an Exchange 5.5 server in order to access mailbox
information or configuration of the mail organization, you have to take
some things into consideration.
You need to keep in mind that LDAP pathnames of
Exchange 5.5 directories slightly differ from the 'normal' AD syntax: In
an organization with the notation 'Company-Mail', the receiving container
in the site 'Karlsruhe' would have the following pathname:
cn=Recipients,ou=Karlsruhe,o=Company-Mail
Moreover, you always have to work with OpenDSObject when
doing a bind operation and state the relevant Exchange server at the same
time (and, if applicable, the LDAP port number with which the server is
set up with, too). The best user name is the NetBIOS logon name of a user
with pertinent credentials in the Exchange directory. '1' has to be used
as logon flag:
Furthermore, Exchange 5.5 as LDAP server shows an annoying habit: It makes
it difficult to access objectswhich are not displayed in the address book. This
can be avoided by using a special version of the logon name in the operation
OpenDSObject:
cn=<username>, dc=<domain>, cn=admin
By the use of this administrative bind logon, it is possible to access
hidden or even deleted (still in the DIR data base) objects besides normal
ones.
Hidden objects are objects where the LDAP attribute Hide-From-Address-Book is
set TRUE.
Deleted objects are objects where the LDAP attribute Is-Deleted is
set TRUE.
An example for such an access:
Please note that the logon needs to be done with the authentication flag '0' (for simple auth with cleartext password).
Bind as Anonymous to Exchange 5.5 Server
If you want to connect to an Exchange 5.5 server as an anonymous user without user name and password, this needs to be allowed explicitly at the relevant server or the corresponding Exchange 5.5 site at first:
From now on, a client trying a bind operation with empty password and user name is logged on as an anonymous user and has access to directory information - however, only those that are enabled for an anonymous access. On which attributes an anonymous logged on LDAP client is allowed to access can be seen and changed in the DS site configuration of the accordant Exchange 5.5 location.
However, there are some things that need to be taken into consideration during bind operations. An anonymous user is unable to see the content of container objects. Thus, it is inevitable to access single objects like mailboxes, custom recipients or distribution list by the use of the complete LDAP path. For this, the logon with the operation OpenDSObject but without user name and password is used:
If you want to access several objects or if you don't know the precise LDAP paths, than you may run a directory search via ADO interface. The procedure of an ADO search is explained in the SelfADSI Tutorial under the paragraph, 'Searching objects in the directory'. But in order to run an anonymous ADO inquiry against an Exchange 5.5 server, some modifications need to be accomplished. They are explained in the Microsoft knowledge base article Q223049. First of all, the base string of the directory search is left out and secondly, the Global Catalog Provider with the LDAP port 389 (or the set up LDAP port of the relevant server) has to be stated in the LDAP pathname. Otherwise, this provider is useless for accesses to Exchange 5.5 directories, because only Active Directory directories do feature a Global Catalog operation. However, in this case here we use this trick in order to run an anonymous ADO search.
A third change compared to a common ADO search within the directory is the explicit creation of an ADODB.Command object, because its characteristic PageSize is needed for the anonymous query. In the following example all mailbox objects are indicated. For accessing other objects you just have to change the LDA filter: