Windows 8.1: Changes Illustrate Attention to Detail

After spending a bit of time with the Windows 8.1 preview, I've been impressed by some of the "little things". While there are large overhauls to address community feedback, this was expected; what I didn't expect is a series of minor tweaks and fixes to make the OS more user friendly for everyone from the entry level user to the longtime power user.

Modern UI with a wallpaper background, substantially more straightforward PC settings, and Windows Update improvements are all very welcome, but my favorite is demonstrated in this screenshot easy to interpret comparison:

Ctrl + X menu comparison; 8.0 on left, 8.1 on right

This means someone in the Win 8.1 dev team is evaluating power user tools for improvement as well, and I'm very happy to see this sort of improvement. I was initially skeptical, but after seeing these sorts of enhancements I'm definitely looking forward to the final release.

This month has been a bit slow because I'm working on a couple large articles. Stay tuned for some Hadoop and DirectAccess!

Update 10/11/2013: Microsoft removed this from RTM, so.... yeah.

Manage the Windows Firewall with Powershell

With the release of Windows Server 2012 and Windows 8, Microsoft has begun issuing the following warning when using NETSH to manage the firewall:

In future versions of Windows, Microsoft might remove the Netsh functionality
for Windows Firewall with Advanced Security.

    

Sounds like a good enough reason to learn how to manage the firewall with Powershell to me. Fortunately Microsoft has made welcome improvements to firewall management in Powershell for version 3. Let's do it.

Assumptions

• Windows 2012 or Windows 8
• Administrator access to the machine in question
• Powershell ran as administrator on the machine in question

CMDLets Involved

Powershell provides the following commands for firewall management:

Get-Command -Noun "*Firewall*"


Copy-NetFirewallRule
Disable-NetFirewallRule
Enable-NetFirewallRule
Get-NetFirewallAddressFilter
Get-NetFirewallApplicationFilter
Get-NetFirewallInterfaceFilter
Get-NetFirewallInterfaceTypeFilter
Get-NetFirewallPortFilter
Get-NetFirewallProfile
Get-NetFirewallRule
Get-NetFirewallSecurityFilter
Get-NetFirewallServiceFilter
Get-NetFirewallSetting
New-NetFirewallRule
Remove-NetFirewallRule
Rename-NetFirewallRule
Set-NetFirewallAddressFilter
Set-NetFirewallApplicationFilter
Set-NetFirewallInterfaceFilter
Set-NetFirewallInterfaceTypeFilter
Set-NetFirewallPortFilter
Set-NetFirewallProfile
Set-NetFirewallRule
Set-NetFirewallSecurityFilter
Set-NetFirewallServiceFilter
Set-NetFirewallSetting
Show-NetFirewallRule

As per normal, type get-help followed by the CMDLet name in question to get more information.

Common Examples

Below are some examples of common tasks you may wish to perform with Powershell:

Enable or Disable the Firewall

Disable the firewall on the DOMAIN profile:

Set-NetFirewallProfile -Profile Domain -Enabled True

Note the -Enabled parameter does not accept typical $True but rather True. Obviously False is an option and the other valid profiles are "Public" and "Private".

Enable a Group of Pre-Made Rules

Groups are sets of rules for a specific purpose. Windows ships with several; are a few you may find useful:

Set-NetFirewallRule -DisplayGroup "Remote Event Log Management" -Enabled True
Set-NetFirewallRule -DisplayGroup "Windows Firewall Remote Management" -Enabled True
Set-NetFirewallRule -DisplayGroup "Windows Management Instrumentation(WMI)" -Enabled True
Set-NetFirewallRule -DisplayGroup "Remote Desktop" -Enabled True
Set-NetFirewallRule -DisplayGroup "Windows Remote Management" -Enabled True
Set-NetFirewallRule -DisplayGroup "Remote Administration" -Enabled True

To list all groups, see the item below.

List all current Rule Groups

$rules=Get-NetFirewallRule
$DisplayGroups=foreach ($rule in $rules){$rule.displaygroup}
$DisplayGroups|Select-Object -Unique

Make a New Rule

New-NetFirewallRule -DisplayName "Allow Inbound OpenVPN Client Requests" -Direction Inbound -LocalPort 1194 -Protocol UDP -Action Allow
New-NetFirewallRule -DisplayName "Block Outbound itunes.exe" -Direction Outbound -Program "C:\Program Files\apple\itunes\itunes.exe" -Action Block

Enable or Disable an Existing Rule

Set-NetfirewallRule -DisplayName "Allow Inbound OpenVPN Client Requests" -Enabled True
Set-NetfirewallRule -DisplayName "Allow Inbound OpenVPN Client Requests" -Enabled False

Delete a Rule

This will permanently delete a rule. To disable use the set-netfirewallrule command from the previous section.

Remove-NetfirewallRule -DisplayName "Allow Inbound OpenVPN Client Requests"

Get Firewall Profile Information

Get-NetFirewallProfile -name Domain

Manage Rules Remotely

Any of the commands can be used remotely by using the New-CimSession cmdlet. This also assumes you have already enabled the firewall rule group "Windows Firewall Remote Management" as listed above.

$TargetComputer=New-CIMSession -Computername MYCOMPUTER
Set-NetFirewallRule -DisplayGroup "Remote Event Log Management" -Enabled True -CimSession $TargetComputer

What About Windows Server 2008/7?

Unfortunately, this will only work in 2012, 8, or newer even if you install Powershell 3.0 on  previous versions. The NetSecurity module was newly introduced in 2012/8. If you want to manage the FW on older versions you'll need to use NETSH.

Tip 'o The Iceberg!

So that's just a start to all the things we can do with powershell to manage the firewall. This article focuses on controlling one machine at a time so you'll most likely want to investigate controlling rules via group policy. Server 2012 introduces some very interesting tools for that as well. (Open-NetGPO!) For more information, see the links below and as always feel free to interact using the comments!

Further Reading

Technet: Windows Firewall with Advanced Security Administration with Windows Powershell
Let IT Know Blog: Manage Windows Firewall With Powershell 3
Microsoft Networking Blog: Deployment: Windows Firewall and Group Policy

Safely Demote a Windows 2008/r2 Core Domain Controller

Have you installed shiny new 2012 domain controllers? Do you have old, musty 2008r2 domain controllers laying around? Do you want some french fries?

Me too. Let's take a holistic look at decommissioning a domain controller. This article will not only walk through the actual demotion process but also list important pre and post steps to any successful domain controller removal. Most of the steps outlined here should actually work on 2000 up, but I've focused on 2008r2. Note that doing this in a production environment is something you may want to do over the course of a couple weeks due to reasons that will shortly become apparent. That said, let's go.

Assumptions

• New domain controllers are installed and ready to go
• Domain Admin Privs
• A backup of the server should something go wrong. Note a snapshot will not suffice; as a general practice one should never use snaps on a DC.

Ensure Replication is Working Correctly

Removing a domain controller can be dangerous if your replication isn't appropriately healthy.Check the following event logs on EACH Domain Controller for issues regarding replication/DNS:

• Application
• Applications and Services Logs->DFS Replication
• Applications and Services Logs->Directory Service
• Applications and Services Logs->DNS Server

If there are any issues, sort them out prior to continuing.

Re-Point Clients

Next we need to ensure all clients are pointing to DNS servers other than the one you intend on taking down. Do the following:

• Update your DHCP scopes with the addresses of the DNS servers you intend on carrying forward
• Update static "clients" (probably servers) with the appropriate DNS settings
• Update devices on your network appropriately as well. 

Your DHCP lease duration will determine how long you need to wait for the next step. The DHCP RFC tells us that clients will attempt to re-up their lease at the halfway point of the lease. Therefore, if your lease is 7 days you'll need to wait 3.5 days from when you make the change (Assuming the DHCP is fully available). Once you think all the clients have been moved, then move to the next step.

Enable DNS Logging on the DNS Controller to be Decommissioned

Now that we think the DNS server isn't used, we enable debug logging to ensure that nobody is referencing this server for DNS look-ups. Avoiding outages is more fun than fixing them. :)

1. Edit the DNS server properties for the server to be decommissioned.
2. Click the "Debug Logging" tab. 
3. Check the "Log packets for debugging" and set a location for the log. Generally the defaults for this application will be sufficient. Click "OK"
4. Restart the DNS server service or reboot the server when your environment permits to start logging.

Wait however long you would like before continuing; the longer you wait the more opportunity you give for devices still pointing to this server to issue a query. You make the call here depending on your environment.

After that wait period: Open the log you specified above; here we'll be reviewing the log for clients that still need their DNS server settings updated. At the top of the log you'll see a couple pages of initialization information that can be safely ignored. After that there will be a log of the DNS queries that the server has received. The first IP address listed in each entry is the IP of the requesting client. You may see some requests from other domain controllers; so long as the other DCs have their "client" settings configured correctly you can ignore these entries as some DC->DC DNS traffic is normal. Taking that into account, look for machines querying this DNS server and re-mediate them prior to moving on.

Transfer FSMO roles off of the DC

Before demoting the DC you need to ensure there are no FSMO roles served by it. I won't cover this in a step by step at this time to keep the article focused. To do this, refer to one of the two following links:

• Microsoft KB: Transfer FSMO roles using the command line
• Technet Wiki: Transfer FSMO roles using the GUI

Demote the DC

We'll use an unattended answer file with dcpromo. You can do this on the command line but it makes it a bit easier to prepare and review the file.

1. Create a new text file. 
2. On the top line, enter

   [DCINSTALL]

3. Enter the following lines after [DCINSTALL]:
   

   
   administratorpassword=NewLocalAdminPassword(required)
   removeapplicationpartitions=yes
   removeDNSDelegation=yes

   You may need to add other options as well, especially if this is the last DC in the domain, your Domain Admin privs are associated with a different account, or similar for the DNS service. Also, this assumes you have a DNSDelegation to remove. If you do not you should take that line out. Refer to this technet article for a full guide.
   
4. Save the file to the domain controller to be demoted.
5. Log on to the DC to be demoted. 
6. At an elevated command prompt (default on core) execute:

   dcpromo /unattend:"(path to file)"

   where path to file=the file you just saved, i.e. dcpromo /unattend:c:\temp\demote.txt
7. After successful execution the machine will successfully reboot. If you intend on re-using the machine for other operations you can log back in and execute dcpromo /uninstallbinaries to remove unnecessary files. If taking the server down don't bother.

Note: If you cancel a demote operation using this file the administratorpassword field will be intentionally blanked out by the installer. You'll need to reset if if you start again.

After the demotion, open up %SystemRoot%\debug\DCPROMO.LOG on the old DC and ensure the operation didn't have any major errors. After confirming the demotion was successful...

Clean Up DNS

After waiting for a replication cycle (should be 15 minutes, but wait an hour to be safe) it's time to ensure AD DNS was cleaned up successfully. Open the DNS manager and point it to one of your new domain controllers. Browse through your zones, including your _msdcs.domain.ext zone. Pay particular attention to the listed NS records in each zone. Those can also be manipulated by right clicking the zone->properties->Name Servers. Ensure only the new DNS servers are listed. Fix any other records that are incorrect; common clean up items are the _msdcs delegation in the primary zone and the sites container under the _msdcs zone. Before making changes to anything other than the the NS records (Name Servers GUI) make sure you fully understand what function the records serve. If you're unsure, this will take some study; here's a good place to start.

It should also be safe to remove the machine from the domain now should you choose to do so. To remove the machine, execute the following on a command prompt:

netdom remove /d:%USERDOMAIN% %COMPUTERNAME%

Also, be mindful that if you were using the old DC in your Windows Time infrastructure you may want to revisit that. Here is an article on how to setup an authoritative time source.

Test

Now that the machine is gone and DNS has been cleaned up, it's time to test your domain. To do so, perform the following tasks:

• Run DCDiag on a new DC with the following command line: dcdiag /e /c and review the output for any issues. 
• Review the event log on each domain controller. Refer to the "Ensure Replication is Working Correctly" section above for the log locations. 

That's it! You've successfully removed a DC and made sure nothing will come back to bite you. If you have questions/comments please feel free to leave the below. 

Additional Reading

 

Technet: Demote a Domain Controller
Technet: DCDiag

Upgrade Windows Server Core 2008r2 to 2012 In Place..Unless it's a Domain Controller

I would never recommend an in place upgrade of any Windows version, but sometimes it may be required in certain situations. Should this be necessary I figured we could take a few minutes to walk through it. Note that doing this on a Domain Controller presents additional challenges listed at the end of this article. (TLDR: Don't do an in-place upgrade of a core 2k8r2 DC to 2012)

Let's do a core upgrade from 2008r2 to 2012:

Assumptions

• Your 2008r2 Filesystem is healthy and you don't have any major issues with the services on the node. 
• Local Admin Access
• A valid license

Upgrade

1. Insert the 2012 disk in the physical machine or VM you intend to upgrade. 
2. Change directory to the disk and execute setup.exe, i.e. "j:" (ENTER) "setup.exe"





3. When prompted, choose "go online and install updates now" if you've got internet access on this machine. If not, more forward without updating. 





4. Enter your product key for this install. Most enterprise customers will either use a volume license key or datacenter key. 
5. Here you can select to either stick with the core install or install the GUI as part of the upgrade. I'm assuming that because you are upgrading the core version you'll want to stick with core. 





6. Accept the license terms. 
7. Select "Upgrade" unless you want to do a custom install. I won't cover that here since the options would be specific to your implementation.





8. At the next screen you will be warned if there are any compatibility issues; often times virtualization components will be flagged. Oft times you can ignore this warning, but be sure you read it in full and consider how easy it would be to double back now and correct the issue. 





9. The upgrade process will now proceed; there will be a few reboots. 





10. After the upgrade is complete, ensure you update virtualization components if applicable and run Windows Update. 

Upgrading a domain controller on a core installation of 2008r2 to 2012 doesn't really work without relatively major workarounds. See this Microsoft support article for more information. This fix took quite awhile to be developed, and leaves a bit to be desired. It's probably easier to do the right thing anyhow; stand up new 2012 DCs and decommission the old 2008r2 servers. After you decommission the old ones, make sure you ensure the AD sites as well as the _msdcs and primary DNS zones are cleaned up correctly. (that's an article in and of itself) There is a long discussion thread regarding this workaround on the Technet forums.

The Dreaded Black Screen of Life!

It should also be noted that the Win2012 certification exams (70-41x) are not aware of this issue. Until next time!

Windows 2012 NAP (NPS) with DHCP

After my last article on DHCP I decided to flesh out the Microsoft offerings and expand into Network Policy Server. NPS is actually a set of different features from Microsoft including RADIUS and what the rest of the industry knows as NAC, (Network Access Control) which Microsoft calls NAP (Network Access Protection). This allows you to grant or deny network access to clients based on criteria such as:

• Domain/Group Membership
• Client source network
• Time of day
• Client health (as determined by an SHV, see below for more)

3 out of 4 Doctors are very serious about Microsoft NAP.

These rules must be introduced to the clients at an insertion point (think of it as an entry gate). The supported insertion points include:

• IPSec
• 802.1X
• VPN
• DHCP
• RDGateway

I'll be covering integration with DHCP since it is by far the most cost effective method considering the required role of Microsoft based services in the environment. For information on the others, see Technet: NAP Enforcement Points.First, let's set up NAP:

Assumptions

• At least one Windows 2012 server ready to go. Note that NPS is not supported on server core. Most of these instructions are applicable to 2008/r2 as well.
• DHCP installed and ready to go.
• Sufficient Privileges (Domain Admin generally)
• I assume you'll be installing NAP on the DHCP server itself. You can have these roles on separate servers should you desire, but you'll need to install the NAP piece on the DHCP server as a RADIUS proxy. I won't be covering that piece here. For more on that, see this Technet article.

Installing NAP

1. Using server manager, select "Manage"->"Add Roles or Features"
2. Navigate through the Add Roles and Features Wizard, selecting the target server and "Network Policy and Access Services".





3. When prompted to select role services, you need keep only the default "Network Policy Server" selected and continue through the wizard.

Repeat this step for the DHCP server as well if it's a different server than the one you installed NAP on.

Configuring NAP

The NAC portion of NAP is actually a collection of several different elements. The following elements make up a NAP policy that can be used by DHCP; numbers in front represent the default number of that item for one overall policy:

• Connection Request Policy (Created by Wizard)
• (3) Network Policies (Created by Wizard)
• (2) Health Policies (Created by Wizard)
• Windows Security Health Validator
• At least one Remediation Server Group

There is a (seemingly hidden) wizard to guide you through the process of creating most of these elements, but we're going to create the unguided ones first and then circle back and use the Wizard since we'll want to point to those during the Wizard portion. For all these sections save the DHCP and client sections we'll be working in the Network Policy Server management tool.

Windows Security Health Validator

The Security Health Validator is the policy for defining what a healthy windows client is. The built-in Windows SHV gives the NAP server the capability to interact with the Network Access Protection Agent service on Windows clients (XP SP3 and newer) to determine the health status of that given client. The Security Health Validator determines what criteria the client must pass for the client to be considered healthy. There is a default configuration that can be utilized but for the sake of experience we'll configure the Windows SHV. To do so:

1. First, open the NAP management tool by selecting "Tools"->"Network Policy Server" from Server Manager.
2. Expand "Network Access Protection"->"System Health Validators"->"Windows Security Health Validator"->"Settings"
3. Right click "Settings"->"New"
4. Give the SHV a name; make it something meaningful to describe the target client base, i.e. "Standard Client Set"
5. Set your settings as desired; they're split into settings for Windows XP and Vista or higher. The settings are quite straightforward though it should be noted that if you would like to utilize WSUS to update out of compliance clients (assuming you select being out of date makes for a failed check) you'll need to check the box on the very bottom of the options dialog. Click "OK" when complete.





6. Click on the "Error Codes" under "Settings" and take note of the Error Code Configurations. Generally the default state of "Noncompliant" for each setting is desirable, but depending on your clients and equipment there may be situations where you would want to change some of these SHV check failures to compliant.

Note that third parties can also create SHVs to plugin to the NAP architecture for use with other products. (Old list of some others here)

Remediation Server Groups

The remediation server groups are the servers that will be made accessible to non-compliant clients if you choose to do so. These servers can be used to patch clients to a compliant status. Note that any services needed to contact the remediation services (WSUS, Antivir FTP, etc.) need to be available for the clients to update properly. (DNS, etc.) Under the DHCP enforcement model, these servers are made available via static routes. Also note that you can provide a help URL to a website instructing access-limited clients on how to repair their machines. The server that hosts this URL and all resources required to resolve it must be part of the remediation server group as well. For more information about RSGs, see Technet: Planning the Placement of a NAP Remediation Server. Assuming you have determined which servers need be part of the remediation group, let's set them up:

1. Expand "Network Access Protection"->"Remediation Server Groups"
2. Right Click->"New" (Note that these can be stored as templates for use elsewhere as well)
3. Give the group a meaningful name; note that each health policy can use only one group, so everything for that client base will need be in that group. Something like "Sitename Remediation Group"
4. Click the "Add" button to add a server.
5. Enter a friendly name for this server, i.e. "Minneapolis WSUS 01" or just the server name and then enter the DNS name and click "Resolve". Hit "OK" when complete.
6. Repeat steps 4 and 5 for each server in this group. Then hit "OK" on the "New Remediation Server Group" page.

Setup Remaining Items with The Whiz

1. Click "NPS" on the top of the Network Policy Server management tool.
2. Click "Configure NAP" to launch the secret hidden Wizard.





3. Select "Dynamic Host Configuration Protocol (DHCP)" under "Network Connection Method". Note this is where you would select a different option should you want to use a different insertion point. If you wish to enable this policy on only specific scopes then give the policy a name, I.E. "Minneapolis NAP DHCP".  If you wish this policy to be effective on all scopes do not change it from the default name. Click "Next".
4. On the next screen, click add if the DHCP server is not on the same server as the main NAP server. If that is the case, enter a Friendly Name, Address, and Shared Secret and click "OK". If not, no action is necessary. After this is complete, click "Next".
5. On the next screen, "Specify DHCP Scopes", we need only add scopes if we want this policy to apply to a specific set of scopes. If we do not specify any scopes it will apply to all NAP enabled scopes. Either add the name of all specific scopes to which this policy will apply or just click "Next" with the scopes empty to have it apply to all.





6. The "Configure Machine Groups" screen, like the previous DHCP Scopes screen, is only for limiting access to a set of computers. Should you choose, specify the group(s) of computers you would like to receive IP addresses. In most cases you should leave this blank, but in the event you would restrict via group click "Add" and enter the groups you would like to have access. Click "Next" when you are done with this screen.





7. On the next "Specify a NAP Remediation Server Group and URL" screen select the server remediation group we created earlier. If you would like the clients to have access to a web site describing how to re-mediate their machines enter that under "Troubleshooting URL". Note you must setup this site, it is not included with NAP since the instructions will be different depending on your software selection. After entering the required information, click "Next".





8.  "Define NAP Health Policy" is the final screen. You should see the "Windows Security Health Validator" selected and you can go ahead and enable auto-remediation of client computers with the applicable check box. I'll address this a bit more in closing.
9. As for "Network access restrictions for NAP-ineligible client computers", select whichever you prefer. In most cases if you've bothered to come this far you'll be selecting to deny full network access since that's usually the point. Click "Next".





10. You will be presented with a summary screen; review the information and click "Finish".

Configure Clients

We need to configure two important elements to make the clients functional: Enable the service and configure it to enforce via DHCP. To accomplish that, we'll use group policy. You will need to ensure your group policy objects are targeted appropriately via something like OU linking or security filtering. If you need more information on how to target group policy objects, see this link. Also note that according to some Microsoft documentation, the Wired and/or Wireless Autoconfig services need to be set to automatic, but in my testing they worked when set to manual. Keep that in mind if you have issues.

1. Edit the group policy object you plan to use for NAP client enforcement using the Group Policy Management tool.
2. Navigate to Computer Configuration->Policies->Windows Settings->Security Settings->System Services
3. Double click "Network Access Protection Agent" and check "Define this policy setting" and select "Automatic". Click "OK" to save the setting.





4. Navigate to Computer Configuration->Policies->Windows Settings->Security Settings->Network Access Protection->NAP Client Configuration->Enforcement Clients
5. Double click "DHCP Quarantine Enforcement Client", check "Enable this enforcement client" and click "OK" to save the setting.





6. Provided you're ready, take any steps necessary to apply the GPO to the desired clients. (Link, etc.)

Enable in DHCP

You can either enable globally or on a per-scope basis. I will give the instructions on how to enable globally. If you want to enable on a per-scope basis substitute right-clicking on the "IPv4" below with the scope(s) you desire instead. In that case, you'll need to specify the custom name of the policy you created in step 3 above.

1. Open the DHCP Manager and point it at the server in question.
2. Right click "IPv4" and click "Properties"
3. Click "Network Access Protection"
4. Select what you would like to happen should the NAP server become unavailable, then click "Enable on all scopes".





5. You will be notified that your NAP settings will be overridden on all scopes. Assuming this is what you would like to do, click "Yes".
6. Click "OK".

If you're using a 2012 failover/loadbalance configuration the NAP settings will replicate for each scope, but make sure communication to the NAP server is configured correctly for each DHCP server. That connection information is not replicated. Here is additional info should you need it: Technet: Configure a DHCP Server for NAP. No restart of anything is needed; you should be using NAP now!

Usage Notes/Troubleshooting

• If using a custom profile name for a specific scope, you'll need to provide the custom profile name. This name is the name of the connection request policy you would like to use. For more info see: Configuring Custom NPS Policies Per DHCP scope





• The event log location relevant to NPS authentication is in the security log with the task category of "Network Policy Server". A filtered view of this can be found under "Custom Views->Server Roles->Network Policy and Access Server".
• Know that this solution won't keep out anyone trying to infiltrate your network; anyone with a moderate amount of savvy can take steps to determine what IP to assign themselves should they have physical access to your network.
• What references what?
• * Compliant and * Non-Compliant Network Policies reference Health Policies
• Health Policies reference Security Health Validators
• DHCP scopes reference Connection Request Policies
• You can add several other types of criteria to your policy should you desire. Take a look at your policies under NPS->Policies->Network Policies for more options.
  





• If you enabled auto-remediation, clients will try to repair themselves for simple issues. For example: if a client's firewall is off and the policy requires it, the client will re-enable the firewall and attempt to pass the health check again. Should this fail manual intervention will be necessary. For more information on how to troubleshoot the client, see "Configure NAP Tracing" on Technet.
• Make sure you monitor the load on your NPS servers; the last thing you want is for them to get overwhelmed and prevent proper servicing of DHCP requests. There are some performance counters that can help you with this task; for more info see Technet: Load Balancing with NPS Proxy. Also, be sure to read up on Technet: Best Practices for NPS which covers performance as well as other important info.
• For some information regarding how to use Powershell to configure/manipulate NPS, see my post here.

Prologue

Obviously we're just scratching the surface here; there is quite a bit more that we could dig into but I'm going to stop here in the interest of time. NAC solutions aren't particularly popular right now in a regular office scenario, but as issues continue to arise with malware, etc. more companies may determine these sorts of solutions are necessary. If you already have a Microsoft based infrastructure you probably have nearly everything you need to implement this solution. If you have questions/concerns/comments please feel free to comment. Thanks!

References

Network Policy Server

Network Policy and Access Services Overview

Network Access Protection in NPS

Checklist: Implementing a DHCP Enforcement Design

Networking and Access Technologies: Network Policy and Access Services

Planning the Placement of a NAP Health Requirement Server

NAP Client and Server-side Component Communication

Windows Server 2012 SuperFeature: DHCP App-Level Failover/Loadbalance

Foreward

One of my favorite additions to Windows Server for the 2012 version is application level load balancing and fail-over. This all new implementation does away with the previous solutions: "scope-splitting" and Windows clustering, neither of which I have ever felt comfortable recommending to a client. Splitting scopes doesn't do enough to prevent outages, and clustering is too complex to be a DHCP solution.

Fortunately, Microsoft recognized this gap in their product and released this new app level failover solution that aims to be as simple and straightforward as possible. I've deployed this a couple of times now and I'm blown away. Here's a high level overview of the implementation:

• A single implementation can have two servers, no more. 
• Servers can be configured in load-balancing or hot standby mode. 
• Servers can reside across routing boundaries. (Enables unified management as well!)
• Failover/Loadbalance Limited to IPv4
• DHCP supported on server core
• (Optional) Replication encryption 
• Limit of one replication relationship type between two partners

And best of all,

• Easy to set up and maintain.  (With a couple caveats I'll list below)

Hot Standby vs. Load Balancing

The hot standby option utilizes one DHCP server to service requests while the other waits to step in should the primary fail. A percentage (generally single digit) of the scope in question needs to be dedicated to the passive standby server for slack address space to allocate in a failover event where the backup hasn't yet asserted primary status. Microsoft states that hot standby is useful for multiple multi-site deployments wherein the primary would be onsite and a secondary would be located offsite should the primary fail. Here are a couple scenarios well suited to hot standby:

Multi-Site, Single Backup

Two sites backing each other up

The load balancing strategy splits client servicing based off of a MAC address hashing algorithm and will still respond to client requests that the other member in the pair should service in a situation where the client has gone unanswered. Provided you're using a datacenter licensing model and virtualization, most folks will want to utilize load balancing with two DHCP servers per site, generally on different hosts connected to different switches. If needed, load distribution mechanisms like F5s will work with this tech.

Two Sites Each Independently Load Balanced

Now let's set up DHCP failover or load balancing:

Assumptions

• Basic knowledge re: Windows server 2012 and DHCP
• Two 2012 servers ready to go and fully patched

Since we need to set up at least two servers, we'll do this twice, once with the GUI and once with Powershell.

DHCP Server Setup (GUI)

1. Install the DHCP server role by using server manager and selecting Manage->Add Roles and Features





2. After bypassing the intro screen, select "Role Based or Feature Based Installation" and select your server.





3. Select the "DHCP Server" role. Admin tools will be auto-selected as needed. 





4. Click "Next" through the rest of the Wizard. Once it completes, you'll be notified that DHCP configuration needs to be completed.





5. Launch the DHCP Post-Install configuration wizard and complete the DHCP setup by authorizing the DHCP server. 

 

DHCP Server Setup (Powershell)

Where (Servername) is the FQDN of the server you wish to install, execute the following on a domain connected computer with proper rights on the target machine:

1. Load the servermanager module:

   Import-Module Servermanager

2. Install DHCP:

   install-windowsfeature -ComputerName servername.domain.lan -name dhcp -IncludeManagementTools

3. When complete, authorize in AD:

   Add-DhcpServerInDC -DnsName servername.domainname.lan

Note that in step #3 you must specify the -ipaddress parameter (i.e. -ipaddress 10.0.0.10) if your server has either multiple NICs or has messed up registration in DNS. See here for more info.

Prep for Server Pairing

After authorization, the DHCP services need be restarted due to group add/creates. Do that or reboot the servers in question, whichever is easier. Set up your DHCP scopes as you normally would on one of the two servers. (More info, ignore the 80/20 part) 

Configure DHCP Server Pair (GUI)

1. Open up the DHCP management GUI and right click on the scope you would like to load balance and select "Configure Failover..."





2. On the "Introduction to DHCP Failover" screen, select all scopes you would like to configure (or "Select all" for all) and click "Next".





3. On the "Specify the partner server to use for failover" screen select the other DHCP server. This can be looked up provided the server has been registered in Active Directory. 





4. On the "Create a new failover relationship" page configure the following:
1. Relationship name: Configure a name for this partnership; you may want to manipulate this via Powershell so take that into account when considering a very complex name. 
2. Maximum Client Lead Time: This determines two three things: A) The lease time for a new client request if the server responsible for that client is down and the other answers the request and B) The amount of time one server will wait for a dead partner server before it takes control of the entire IP address block. C) (added 8/5/13) The amount of time one server that had been down must be available to the other before "Partner Down" status will automatically be changed to "Normal" status. (See comments for an example of this) The default of 1 hour is generally good but you may want to tweak depending on your setup. 
3. Mode= Load Balance / Load Balance Percentage: This determines how much of the total load each server will take. 
4. Mode= Hot Standby / Role of Partner Server/Addresses reserved for standby server: This determines if the partner sever is the primary or the standby and how much of each scope is reserved for distribution should the primary go down. Be careful that you have enough reserved here so that you won't run out of IP addresses prior to switching to "Partner Down" mode while also ensuring you won't run out of IPs on the primary server due to reserved addresses on the standby.
5. State Switchover Interval: Selecting this enables either server to enter "Partner Down" state should communication be interrupted for the number of minutes specified after the option (default 60) resulting in the remaining server taking full responsibility for the scope(s). If this is not selected, an admin must manually choose to put the server into partner down state.
6. Enable Message Authentication and Shared Secret: I highly recommend checking this box and specifying a long (14+ character) shared secret. This will encrypt messages between the two servers by using SHA-256. Should you wish to change the crypto, navigate to "HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\Services\DHCPServer\Parameters\" in the registry and add/change "FailoverCryptoAlgorithm".





5. You'll then be met with a failover summary screen. Verify the info and click "Finish". 





6. You will be shown the failover setup process. 

Configure DHCP Server Pair (Powershell) 

This time around you don't need to do configuration twice, so this section would be in lieu of the previous. Refer to the section above for full descriptions, I'll just do mappings here:

Load Balanced

Add-DhcpServerv4Failover [-Name] (String) [-ScopeId] (IPAddress[]) [-PartnerServer] (String) [-AutoStateTransition (Boolean)] [-ComputerName (String)] [-LoadBalancePercent (UInt32)] [-MaxClientLeadTime (TimeSpan)] [-SharedSecret (String)] [-StateSwitchInterval (TimeSpan)]

Where:

-Name = Name above
-ScopeID = The IP of the scope to be partnered
-PartnerServer = DHCP Server 2
-AutoStateTransition = "State Switchover Interval" above. Note that if the "StateSwitchInterval" argument is used in the powershell command then this value is assumed TRUE, otherwise the default is FALSE
-ComputerName = DHCP Server 1
-Load Balance Percent = The % to be serviced by DHCP Server 1
-Max Client Lead Time = Same as outlined in the GUI section
-SharedSecret = Same as outlined in the GUI section
-StateSwitchInterval = Int; specifies how long to wait until auto transition to Partner Down. Makes AutoStateTransition assumed to be true.

Failover

Add-DhcpServerv4Failover [-Name] (String) [-ScopeId] (IPAddress[]) [-PartnerServer] (String) [-AutoStateTransition (Boolean)] [-ComputerName (String)] [-MaxClientLeadTime (TimeSpan)] [-ReservePercent (UInt32)] [-ServerRole (String)] [-SharedSecret (String)] [-StateSwitchInterval (TimeSpan)]

Where:
-ReservePercent = Same as outlined in the GUI section
-ServerRole = Active or Standby

Important Usage Notes!

• Server Options are NOT replicated! Take this into account when setting up replication; you may want to specify options at a scope level so that if they are changed you don't need to manually do it on each server. 





• There have been some reports of replication breaking custom options. See here for more info. 
• How do "Communication Interrupted" and "Partner Down" states get initiated and what effect do they have? Refer to this handy flowchart I whipped up for reference:  

References: 

MSFT DHCP Team Blog: Hot-Standby
MSFT DHCP Team Blog: Failover Load Balance
Technet: Step by Step Configure DHCP for Failover
MSFT Doco: Understand and Troubleshoot DHCP Failover in Win8 Beta (Still Relevant)

Closing

Thanks for taking the time to read; should you have any questions leave them in the comments!

OpenVPN on CentOS Running on Hyper-V Using Windows PKI

I have a knack for titles eh? (Just smile and nod) I've been very impressed by the scalability demonstrated by OpenVPN in applications such as proXPN. Because of this I decided to implement OpenVPN on my favorite Hyper-V friendly distro, CentOS (6.4) and utilize a Windows PKI infrastructure for issuing certificates. Wanna do that? Let's:

Assumptions

• You're familiar with the basics of PKI and how to process certificate requests. For more information on how to setup Windows PKI, see my article here.
• You're familiar with the basics of Linux administration including editing config files, etc. 
• You'll use sudo where applicable. I don't put it on command references to keep them cleaner. 

VM Creation

Create a VM with the following minimal virtual hardware: 

• 384MB RAM
• 1 Virtual Proc
• 10GB HD
• 2 NICs, (native) one either public/DMZ and one on your internal network (or inside the same DMZ if you desire)

It's possible to setup OpenVPN with 1 NIC, but in most configurations it's less secure and I won't be covering it here.

CentOS Setup

1. Download from here; minimal is all you'll need.
2. Insert the ISO to the virtual optical drive on the VM and start it up.
3. Install CentOS to the VM with desired settings; no special configuration is necessary.
4. Setup the NICs with static IP addresses. ("/etc/sysconfig/network-scripts/ifcfg-eth0" and "eth1", more instructions here) The following combinations for connectivity are possible: External/Internal, DMZ/Internal, External/DMZ, DMZ/DMZ. While different options have different pros and cons I'm not going to say what you should use because your circumstances will dictate your direction. I am using DMZ/Internal.
5. Enable ipv4 forwarding by editing "/etc/sysctl.conf" and setting the following value

   net.ipv4.ip_forward = 1

   (It's there and 0 by default)
6. Enable the EPEL so we can grab OpenVPN from it. Ensure you get the correct version, it was 6.8 as of this writing.

   rpm -Uvh http://download.fedoraproject.org/pub/epel/6/i386/epel-release-6-8.noarch.rpm

7. Make the directory for the keys:(We'll copy keys into this dir before install)

   mkdir /etc/openvpn/keys  

8. Make sure SSH is installed; if not:

   yum -y install openssh-server

9. Perform any other tasks you should find applicable to a OpenVPN server such as configuring auto-update (yum install vixie-cron -y needed on CentOS 5 minimal install) or installing any other supporting apps you should want. Just remember that any application you add is a potential security liability.

Create Certificate Templates

I won't be covering the basics of setting up certificate templates; for that see my article.We'll just cover the specifics of this implementation here.

Server Template

1. Open the certificate template manager for you enterprise PKI, and duplicate the Computer template. 
2. When prompted, select the "Windows 2003 Server, Enterprise Edition" and hit "OK". (The version of the OS determines the template version) 
3. Change the template display and name to something sufficiently descriptive such as "Computer (CompanyName OpenVPN Server)"
4. Up the Validity period should you desire. 
5. On the "Request Handling" tab set the private key to be exportable. (We're putting this on a Linux server afterall)





6. On the "Subject Name" tab change the option to "Supply in the request". 
7. On the "Issuance Requirements" tab check that the template requires CA certificate manager approval should you desire. 
8. Change to the "Extensions" tab, select "Application Policies" and click "Edit". Change it so that the "Server Authentication" is the only listed policy. Do not mark the extension critical. 
9. Everything else can be left the same unless you should want to change the permissions under security. 

Client Template

Repeat the steps for the Server template except change the name in 3: to a client name and 8: to "Client Authentication".

After creating your templates publish them to your issuing CA. Again, see my article for instructions.

Enroll For Server Certificate

Since this step is virtually the same for the client I'll be redirecting you here for that step as well. There are a few modifications listed to these steps to accommodate that; don't pay any attention to "For Clients:" on the first go-around.

1. Open the MMC (mmc.exe) and add the certificates snap-in for the local computer.  This can be done on any machine since we'll be exporting it.
2. Enroll in the server certificate template we created earlier. We need to specify a few options, so click "More information is required to enroll for this certificate.  Click here to configure settings." For Clients: use the client template
3. On the subject tab under Subject name, set the "common name" to the FQDN of the OpenVPN server. If you're using split DNS, make sure you set this to the external FQDN. For Clients: use your domain FQDN and set the OU to something consistent for all certs so that you can use the tls-verify option down the road should you choose. I use "vpn.company.com ClientCert"





4. On the "General" tab set the friendly name and the description to whatever you desire. I copy the common name and append "OpenVPN server"
5. On the "Extensions" tab change "Key Usage" to include only "Key agreement" and "Key encipherment". "Make these key usages critical" can be checked. Based on the template it should already have "Extended Key Usage" set to "Server Authentication". For Clients: Use "Client Authentication" rather than server authentication.





6. Under "Basic Constraints" click "Enable this extension" and "Make the basic constraints extension critical"
7. Under the "Private Key" tab select "Allow the private key to be archived" should you desire.
8. Click "OK" and then "Enroll". After the enrollment finishes you will need to click "Finish"
9. Go to your CA and complete the enrollment process, then export the public key and import it back on the requesting computer to complete the certificate request process. 

Export and Split the Certificate

Like the section above, this will be used for the client as well. See For Clients: for that.

1. Using the MMC or command line/powershell, export the newly created certificate WITH the private key to a pkcs12 format. Do not include all certificates in the certification path. Make sure you remember the password.
2. Use OpenSSL (you'll need to download/install from here) to convert the pfx file to standard text, then cut and split the file into a cert file and a key file. I'd walk you through this, but how about I give you a Powershell script to do it instead. :)  Make sure to set the variables at the top of the file to what suits you. If you don't want to use powershell, just follow the comments and the commands to convert and split the file. For Clients: You may want to change the variable definitions at the top of the file to reference client file names.

#set the output files, working file, and password for the PFX
$inputFile="c:\temp\server.pfx" 
$outputPublicKey="c:\temp\serverCert.cer"
$outputPrivateKey="c:\temp\serverCert.key"
$tempFile="c:\temp\temp.txt"
$password="password"


#Set the location to the Openssl.exe file
$openSSLLoc="C:\Program Files\OpenSSL-Win32\bin"


#Execute OpenSSL to convert the PFX file to standard text
& $openSSLLoc\OpenSSL.exe pkcs12 -in $inputFile -nodes -out $tempFile -passin pass:$password


#Now we need to find where the key and cert start and end. 
#For non-script users the point here is that we chop this one text file into two files,
# one the public key and one the private key. The two of those are denoted by the patterns listed below. 
$beginKey=get-content $tempFile |select-string -Pattern "-----BEGIN PRIVATE KEY-----"
$beginKey=$beginKey.LineNumber
$endKey=get-content $tempFile |select-string -Pattern "-----END PRIVATE KEY-----"
$endKey=$endKey.LineNumber
$beginCert=get-content $tempFile |select-string -Pattern "-----BEGIN CERTIFICATE-----"
$beginCert=$beginCert.LineNumber
$endCert=get-content $tempFile |select-string -Pattern "-----END CERTIFICATE-----"
$endCert=$endCert.LineNumber
$length=Get-Content $tempFile |Measure-Object
$length=$length.Count


$key=Get-Content $tempFile |Select-String "-----BEGIN PRIVATE KEY-----" -Context 0,($endKey-$beginKey)
$cert=Get-Content $tempFile |Select-String "-----BEGIN CERTIFICATE-----" -Context 0,($endCert-$beginCert)


#Write out the files. Make sure they're ASCII encoded!
$key.line| Out-File $outputPrivateKey -Encoding ASCII
$key.Context.DisplayPostContext | Out-File $outputPrivateKey -Encoding ASCII -Append
$cert.line| Out-File $outputPublicKey -Encoding ASCII
$cert.Context.DisplayPostContext | Out-File $outputPublicKey -Encoding ASCII -Append


#Get rid of the temporary working file. Not needed for those not using the script. 
Remove-Item $tempFile -Force

Even if you can't run that hopefully you can decipher what's going on. Let me know if you would like any help.

Export The CA Certs and Copy to Server

For Clients: You can use the CA cert you created earlier for the server on the client as well. Just include it in the keys directory with the other certs. 

1. Using the MMC or cmdline/powershell, export the root and (if applicable) intermediate certs to base-64 encoded x.509. For specifics, see here.
2. If using 2 or more tier PKI: You can only specify one CA cert so if you have more than one CA in your chain you need to "stack" them. To do so, pipe both into one file with the simple command from a command prompt: "type RootCA.cer IntermediateCA.cer > CAs.cer" where rootca.cer and intermediateca.cer are the exported certificates. Substitute cat for type if you're doing this on a Linux platform. This will join any listed certs into one chain for use with OpenVPN. 
3. (For Clients: This step is not necessary.) Generate Diffe-Helman by executing

   openssl genpkey -genparam -algorithm DH -out dh.pem 1024

   This can be done on either the Windows machine you are on or directly on the OpenVPN server. Either way, just make sure you copy the dh.pem to /etc/openvpn/keys/ on the OpenVPN server. (see step below)
4. Copy the server private key, public key (both created earlier) and (stacked) ca public key to "/etc/openvpn/keys" on the OpenVPN server. These keys will be referred to as server.cer, server.key, and ca.cer in the future. In order to do security correctly, make sure permissions are cranked down on these files as much as possible, especially the server.key file. (private key) On Windows I use pscp.exe which ships with Putty. For Clients: Just copy the certs/keys into a temp directory for now, we'll move them to the final location later.

Install/Configure OpenVPN on Server

1. Make sure you enabled EPEL above and then execute the following to to install OpenVPN and LZO:

   yum install openvpn lzo -y

2. Copy the sample configs as a starting point:

   cp /usr/share/doc/openvpn-2.2.2/server.conf /etc/openvpn/

   (Make sure the version number in the /usr/share/doc path hasn't changed since I wrote this) 


3. Edit /etc/openvpn/server.conf and pay attention to the following lines: 
1. Set the ipaddress to the address of the NIC you intend to bind to. This should be the NIC closest to the internet, be it an external or DMZ NIC. 

   local 10.1.0.1

2. Set the port to have OpenVPN listen on. 1194 is default and a firewall rule below assumes that, so be aware if you change it.

   port 1194

3. Protocol, UDP vs. TCP. UDP is faster and the client machine will already be managing TCP retrans should they be needed. 

   proto UDP

4. A bit on the the difference between tun and tap: tun is a layer 3 IP routing based solution, whereas tap is a level 2 based solution. Tap can shoot non-routable protocols over the tunnel, so if you're going to play Descent II this is the one you want. The problem (or not) with using tap for standard client connectivity is besides being more complex to setup it also routes broadcast traffic. This won't scale well. Generally tap is used for site-to-site connections. If you want to use tap, you'll need to setup Ethernet bridging. This guide assumes dev tun.

   dev tun

5. Specify the keys we copied over earlier:

   ca /etc/openvpn/keys/ca.cer
   cert /etc/openvpn/keys/server.cer
   key /etc/openvpn/keys/server.key

6. Specify Diffe-Helman copied over earlier:

   dh /etc/openvpn/keys/dh.pem

7. Set the subnet you want to route clients to. This makes that network route through the OpenVPN connection. Note that if your IP range is the same on the close end you'll have problems. Feel free to add multiple lines for multiple subnets.

   push "route 192.168.1.0 255.255.255.0"

8. Set the internal DNS servers you want to push to the clients to facilitate looking up servers on the other side of the VPN. Add one line for each DNS server you would like in the search order of the client. 

   push "dhcp-option DNS 192.168.1.30"

9. If you uncomment client-to-client OpenVPN will allow clients to talk to each other. You'll also need to config firewall rules appropriately should you wish to do this.

   client-to-client

10. Set the maximum number of simultaneous clients.

    max-clients 100

11. Uncomment the following lines to increase security on 'nix systems by lowering privilege level after program launch.

    user nobody
    group nobody

4. Set OpenVPN to start on boot:

   chkconfig openvpn on

5. Configure the IPTables firewall; assuming eth0 is your internal NIC and eth1 is your external NIC. Change the listed NICs in each rule if that assumption is not correct!
1. Edit the IPTables rule by editing /etc/sysconfig/iptables . There are other ways to accomplish IPTables editing, but since I make few changes I would rather just work directly on the config.
2. First, change your SSH rule to allow port 22 on the internal NIC only; you should already have a rule listing --dport 22. Find it and change it to:

   -A INPUT -i eth0 -m state --state NEW -m tcp -p tcp --dport 22 -j ACCEPT"

3. Allow VPN connections on the external interface. If you have changed from the default port make sure to change the port 1194 reference listed here: " -A INPUT -i eth1 -m state --state NEW -m udp -p udp --dport 1194 -j ACCEPT"
4. Setup forwarding rules for this network:

   -A FORWARD -m state --state RELATED,ESTABLISHED -j ACCEPT"
   -A FORWARD -s 10.8.0.0/24 -j ACCEPT

5. Make sure the rules from 2 and 3 are listed before the -A INPUT -j REJECT and the rules from 4 are listed before the -A FORWARD -j REJECT default rejection rules or they'll be ignored. 
6. Reboot the box and ensure that OpenVPN starts successfully. Logs will be written to /var/log/messages. If you have problems and need to troubleshoot you can up the "verb" value in /etc/openvpn/server.conf.

Alternatively, you may see rules listed such as iptables -A INPUT -i tun0 -j ACCEPT and iptables -A FORWARD -i tun0 -j ACCEPT listed elsewhere; these would work in lieu of the 10.8.0.0 rule, but there are security tradeoffs. Feel free to try either if it suits you. For more information about iptables, see this.

Enroll for Client Certificate

For this section you can follow the same instructions as the section "Enroll for Server Ceritificate" with the modifications listed within those points. (Mods in point 2, 3, and 5)

After doing this refer to the Export and Split the Certificate section and use that logic to do the same task to the client cert as well.

Export the CA Certs and Copy to Client

You can use the CA cert you created earlier for the server on the client as well. Just include it in the keys directory with the other certs.

Install/Configure OpenVPN on Windows Clients

1. Download and install from here. 
2. In the install directory, copy the client.ovpn file from the sample-config folder to the config folder for a starting point.
3. Copy the keys we created earlier to a folder on the client; I use (OpenVPN Install Directory)\Keys.
4. Edit ".\config\client.ovpn" and pay attention to the following lines: 
1. Again, we're going to cover tun here. More work will be necessary if you want to do tap. See the server section for an explanation of what these options are. 

   dev tun

2. Enter the external FQDN and port for your OpenVPN server.

   remote vpn.company.com 1194

3. List your certs copied over earlier. Make sure you set the directory correctly and protect that directory relative to the fact that a private key resides within it. On windows you need to use double backslashes because "\" is an escape character. 

   ca C:\\InstallDirectory\\Keys\\ca.cer
   cert C:\\InstallDirectory\\Keys\\clientcert.cer
   key C:\\InstallDirectory\\Keys\\clientcert.key

4. Remark out ns-cert-type server and add remote-cert-tls server in its place. ns-cert-type is deprecated and the template wasn't updated. See here for more info.

   # ns-cert-type server
   remote-cert-tls server

5. After saving the file, launch OpenVPN GUI as Administrator.





6. Connect and enjoy!

Closing

Obviously given the scope of this article there is substantially more depth one could go into; if you have any questions please hit me up in the comments. I'm sure you can see the possibilities of this combination as there is much more automation that could be done. Thus far I've been very impressed by the performance of OpenVPN and I look forward to scaling it out in the future.

References/Additional Reading

• Official OpenVPN HowTo
• CentOS IPTables HowTo
• SafeSrv: OpenVPN on CentOS
• Serverfault question: OpenVPN/Correct IPTables setup
• Jay Libove: Using Windows AD CS to Create Certificates for OpenVPN
• Christoph's OpenVPN Mini-FAQ
• Topdog.za.net: Setup a OpenVPN server on Centos 6
• OpenVPN Forums: Using a Windows CA
• MSFT Ask the Directory Services Team:Enabling CEP and CES for enrolling non-domain joined computers for certificates
• Serverfault question: OpenVPN + iptables/NAT routing
• Bitcube.co.uk: OpenVPN HowTo