Standard Windows Active Directory AuthN/AuthZ isn't LDAP. It is Kerberos (and NTLM). It uses the LDAP Directory in the backend for its database to store credentials and group mapping as well as any other relevant data for the users and other objects as LDAP/DAP Directories were intended to be used.

While LDAP protocol can be used for authentication, Kerberos is the expected to be the safer authentication mechanism as no passwords are transferred in the requests as they are with LDAP authentication. When you log on with Windows to Active Directory, a Kerberos authentication occurs and the ticket is then passed with any/all LDAP requests after that to access data in AD, or on other servers.

That being said, some applications (generally *NIX apps) will authenticate to Active Directory with LDAP. If this is done, the Domain Controllers should have PKI certs on them and LDAPS or TLS should be used to secure the LDAP traffic otherwise the passwords are going across the network in clear text.Better is to use Kerberos which is possible via the open source kerb packages as well as there are several third party vendors now producing products to do it properly (and easily) including Dell (via Vintela/Quest product), Centrify, and BeyondTrust.

For the OpenLDAP/Kerberos bits... See

To get started.


O'Reilly Active Directory Fifth Edition -  

On Mon, Aug 10, 2015 at 11:53 AM, Chris Jacobs <> wrote:

I can be used for any of it.


Here, we use OpenLDAP for authentication (login) and authorization (who can login via sshd allowed groups, who can sudo) on our group's systems – this requires the information being available as well as configuring the clients to USE that information. We also use it to store inventory data which is neither authn or authz (hey, OpenLDAP is a decent hammer and the problem at the time looked like a nail).


Corporate uses Microsoft Active Directory (based on LDAP) – which is used for authn, authz, and a plethora of other uses (mail settings, location info, managing host 'members', etc).


Perhaps googling "what is LDAP for" would be a good place to start with your questions.


- chris


From: openldap-technical [] On Behalf Of Kaushal Shriyan
Sent: Monday, August 10, 2015 5:16 AM
To: Nick Milas <>;
Subject: Re: Is Openldap a Authorization or Authentication system?


Hi Nick,


Thanks for the explanation. Does AAI mean Authentication Authorization Identity and SSO mean Single Sign On? 

As per your example of  OpenLDAP + Kerberos or Radius. is Openldap used for Authentication and Kerberos or Radius server for Authorization? Please clarify. 






On Mon, 10 Aug 2015 at 17:37 Nick Milas <> wrote:

On 10/8/2015 2:16 μμ, Kaushal Shriyan wrote:

> I am not sure if i understand the difference between Authorization and
> Authentication. Does Openldap support both or it supports or
> configured as Authorization or Authentication server? I will
> appreciate if somebody can help me understand with some examples.

 From Wikipedia: "Authentication is the act of confirming the truth of
an attribute of a datum or entity. This might involve confirming the
identity of a person or software program, tracing the origins of an
artifact, or ensuring that a product is what its packaging and labeling
claims to be." That's how we know who an application talks to.

 From Wikipedia: "Authorization is the function of specifying access
rights to resources." After authentication we know the person, but we
still unsure whether it's supposed to access a given resource and hence
the need for authorization.

To get to know Openldap, read:

Everything depends on what you are trying to do, your project needs.

An example for AAI services would be something like OpenLDAP + Kerberos
or Radius. Google for AAI / SSO systems.

Best regards,

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