Friday, February 13, 2015

Mac OS X Extras: Using Centrify and your Windows Infrastructure to provide 802.1x EAP-TLS to Mac OS X Systems


Secure access to Wifi or Ethernet networks is a goal of any security conscious IT infrastructure team, however diversity of platforms makes this goal very hard to achieve, especially when organizations are looking to standardize but have diverse client platforms.

In a Windows world, capabilities such as Active Directory Certificate Services, Group Policies, the Network Policy Service and Windows clients make this goal relatively simple.  The popularity of Mac Workstations has forced many organizations to face this challenge.

The good news is that Centrify has worked very hard to make sure that IT Infrastructure folks can leverage their existing Windows infrastructure to solve this challenge on the macs.
The challenge for any technical lead is that the expertise required just to meet the prerequisites is going to be scattered all over the organization; this means that it's time to flex the ability to coordinate and get people to work together.  Hopefully this post provides a lot of clarity.

How easy is it to implement?

It is as easy as enabling one of the Centrify-provided GPOs for Mac OS X.  Specifically the "Computer Configuration > Policies > Centrify Settings > Mac OS X Settings > 802.1x Settings" and you can pick your flavor:
  • Enable Machine Ethernet Profile
  • Enable Machine Wi-Fi Profile
  • Enable User Ethernet Profile
  • Enable User Wi-Fi Profile
However, this entry would not be useful if I just show you that you can enable the GPO, perform a policy refresh and just like magic: network access.

What I've noticed from prospects or customers that are looking to test these capabilities is that they don't understand all the moving pieces that need to be in place in order for this to work. 

In this post we'll use a checklist to make sure that you understand what needs to be in place to be successful.  

Note:  If you already have 802.1x EAP-TLS running with your Windows infrastructure today, you are very well-positioned for success.


Building Blocks

Active Directory and Windows Services:  There are several ways to accomplish this goal, but in this particular instance, because our goal is to consolidate processes, knowledge and infrastructure, we are leveraging Windows capabilities like Active Directory, AD Certificate Services and the Network Policy Service.  AD Groups will be key to provide access controls;  OUs will determine the scope of GPOs to be used.

Public Key Infrastructure:  PKI is needed to provide the encryption, non-repudiation and authentication between the back-end infrastructure (Active Directory) and the client (Ethernet or Wifi).  The key here is the certificate life-cycle management, this is where Windows PKI uses Group Policy.
PKI Disclaimer:  PKI is not joke.  Any proper implementation needs to provide the assurances that PKI is aligned with your security policy.  If your organization does not have a policy for PKI (general assurances, handling of private keys, policies, templates,  Root and SubCAs) consult an expert.

A Policy/Configuration Management Engine:  Group Policy provides the rules and the enforcement for configuration items and even provides certificate auto-enrollment - a way to manage the certificate lifecycle (issuance, renewal, revocation, etc); in addition, GPOs will be the way that Centrify will provide the Apple profile information.

Network Policy Service: The NPS service on Windows provides the services like Remote Authentication Dial-in User Service (RADIUS) and the policy rules to enable 802.1x.  The NPS Service interacts with Active Directory to leverage groups and attributes.

802.1x-Capable Network Devices:  Any modern switch or access point supports 802.1x EAP and RADIUS.

Centrify Agent for Mac OS X:  This use case showcases the power of the Centrify agent.  Not only it leverages its ability to integrate with AD, but to use advanced services and perform this cohesively within the MacOS platform.  Key capabilities:  Certificate Auto-Enrollment, System Profiles, GPO Engine.

The Lab

  • For AD and PKI:  Modified Microsoft Test Lab Guide:  Provides the domain with a running Microsoft CA.  The RootCA (corp-DC1-CA) certificates are deployed using GPOs.
    Translation:  A common Certificate Authorithy with the proper Certificate Revocation publication methods needs to be provisioned. I did not set APP1 as a SubCA.
  • For RADIUS and Policies:  I'm piggybacking on my APP2 Windows 2012 server
  • Network Devices:  I'm using Cisco small business (300 series) switch and a TPLink (TL-WA90x) Wireless Access Point.
  • Mac Client:  Old Macbook running 10.7 and Centrify 5.2.1

Basic Checklist
OS X System is Centrified
Centrify agent is connected  (run adinfo -m)

PKI Checklist
All Systems have a Root CA in their trust chain?
The Network Policy Server has a computer certificate?
A proper 802.1x certificate template was set up for Mac Systems?
The Mac Auto-Enrollment GPO has been properly deployed?
Was the computer Certificate on the Mac based on the proper template?

You may need to look in the CA's Issued Certificates.
With PKI it's all about consistency.  All systems trust the Enterprise CA; All Certs are Issued by the CA or SubCAs and Programs (like NPS) are using the same trust chain.

NPS/Network Device Checklist
RADIUS clients have been set up properly on the NPS Server
RADIUS servers are properly configured on the network devices
Is there connectivity between RADIUS clients and servers?

Connection Request Policies are set up appropriately (Conditions/Settings)
Network Policies are set up to Allow access based on Conditions
Clients Meet the Conditions
Any conditions added (like AD group membership) must be met in order to have successful connections.
For example, if you're using a condition in which your Mac has to belong to a group called "Mac Workstations 802.1x" you can use the 'adquery user -A computername$ | grep MemberOf'  command to enumerate the AD groups that the computer belongs to

$ adquery user rpmacbook$ -A | grep memberOf Workstations 802.1x, Computers

802.1x Mac Group Policy
Is the Mac System Wifi-capable?
Wifi SSID is correct?
Template Name is correct?
The template Display Name may be different than the template Name
Has the policy been refreshed?  (adgpupdate - remember replication!)
System Preferences > System > Profiles contains payload?


Video Playlist


  1. Do I have to create two certificates for Ethernet and WiFi. I only created one for both but it seems that it gets confused with the profiles downloaded to the MAC

    1. I'm not sure why Centrify Engineer is telling me to create 2 Computer certificates one for WiFi an another for Ethernet. I never seen that.

  2. I'm the author of this article and I'd like you to point out where you read (or saw) that you need two certificates. The whole idea is that you can use the machine certificate for this.

    I have several environments and generate certs for other use cases (e.g. User Cert vs. Computer Cert) and you possible got confused by that.

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