DirectAccess and Azure Multifactor Authentication

Introduction

DirectAccess and Azure Multifactor AuthenticationDirectAccess can be configured to enforce strong user authentication using smart cards or one-time passwords (OTP). This provides the highest level of assurance for remote users connecting to the internal network via DirectAccess. OTP solutions are commonly used because they require less administration and are more cost effective than typical smart card implementations. Most OTP solutions will integrate with DirectAccess as long as they support Remote Access Dial-In User Service (RADIUS).

DirectAccess and Azure Multifactor Authentication

Azure Authentication-as-a-Service

Azure Multifactor Authentication (MFA) is a popular OTP provider used to enable strong user authentication for a variety of platforms, including web sites and client-based VPN. Unfortunately, it doesn’t work with DirectAccess. This is because Azure MFA uses a challenge/response method for which DirectAccess does not support. To use OTP with DirectAccess, the user must be able to enter their PIN and OTP immediately when prompted. There is no provision to begin the authentication process and wait for a response from the OTP provider.

PointSharp ID Multifactor Authentication

An excellent alternative to Azure MFA is PointSharp ID. PointSharp is a powerful OTP platform that integrates easily with DirectAccess. It is also very flexible, allowing for more complex authentication schemes for those workloads that support it, such as Exchange and Skype for Business.

DirectAccess and Azure Multifactor AuthenticationEvaluate PointSharp

You can download a fully-functional trial version of PointSharp ID here (registration required). The PointSharp ID and DirectAccess integration guide with detailed step-by-step instructions for configuring DirectAccess and PointSharp ID can be downloaded here. Consulting services are also available to assist with integrating PointSharp ID with DirectAccess, VPN, Exchange, Skype for Business, Remote Desktop Services, or any other solution that requires strong user authentication. More information about consulting services can be found here.

Additional Information

PointSharp Multifactor Authentication
Configure DirectAccess with OTP Authentication
DirectAccess Consulting Services
Implementing DirectAccess with Windows Server 2016

DirectAccess SSL Offload and IP-HTTPS Preauthentication with Citrix NetScaler

Introduction

Communication between the DirectAccess client and server takes place exclusively over IPv6. When DirectAccess servers and/or clients are on the IPv4 Internet, an IPv6 transition technology must be employed to allow those clients to connect to the DirectAccess server. DirectAccess deployment best practices dictate that only the IP-HTTPS IPv6 transition technology be used. IP-HTTPS uses SSL/TLS for server authentication and optionally encryption. To improve security and performance for IP-HTTPS, an Application Delivery Controller (ADC) like the Citrix NetScaler can be configured to perform SSL offloading and client preauthentication for DirectAccess IP-HTTPS connections.

Please note that the following caveats apply when enabling SSL offload for DirectAccess clients:

  • Enabling SSL offload and IP-HTTPS preauthentication on an ADC for DirectAccess is formally unsupported by Microsoft.
  • SSL offload should not be enabled with DirectAccess is configured to use one-time password (OTP) authentication. Offloading SSL will break OTP functionality.

IP-HTTPS Challenges

The IP-HTTPS IPv6 transition technology is a simple and effective way to allow DirectAccess clients and servers to communicate by encapsulating IPv6 traffic in HTTP and routing it over the public IPv4 Internet. However, there are two critical issues with the default implementation of IP-HTTPS in DirectAccess. One is a security issue, the other affects performance.

Security

The DirectAccess server does not authenticate clients establishing IP-HTTPS connections. This could allow an unauthorized client to obtain an IPv6 address from the DirectAccess server using the IPv6 Neighbor Discovery (ND) process. With a valid IPv6 address, the unauthorized user could perform internal network reconnaissance or launch a variety of Denial of Service (DoS) attacks on the DirectAccess infrastructure and connected clients. More details here.

Performance

Windows 7 DirectAccess clients use encrypted cipher suites when establishing IP-HTTPS connections. However, the payload being transported is already encrypted using IPsec. This double encryption increases resource utilization on the DirectAccess server, reducing performance and limiting scalability. More details here.


Note: Beginning with Windows Server 2012 and Windows 8, Microsoft introduced support for null encryption for IP-HTTPS connections. This eliminates the needless double encryption, greatly improving scalability and performance for DirectAccess clients using IP-HTTPS.


SSL Offload for DirectAccess IP-HTTPS

The Citrix NetScaler can be configured to perform SSL offload to improve performance for Windows 7 DirectAccess clients using IP-HTTPS. Since DirectAccess does not natively support SSL offload, the NetScaler must be configured in a non-traditional way. While the NetScaler will be configured to terminate incoming IP-HTTPS SSL connections, it must also use SSL for the back-end connection to the DirectAccess server. However, the NetScaler will be configured only to use null cipher suites when connecting to the DirectAccess server. Even though Windows 7 clients will still perform double encryption to the NetScaler, this configuration effectively offloads from the server the heavy burden of double encrypting every IP-HTTPS connection for all connected DirectAccess clients. This results in reduced CPU utilization on the DirectAccess server, yielding better scalability and performance.

SSL Offload and Windows 8.x/10 Clients

Offloading SSL for Windows 8.x/10 clients will not improve performance because they already use null cipher suites for IP-HTTPS when connecting to a Windows Server 2012 or later DirectAccess server. However, terminating SSL on the NetScaler is still required to perform IP-HTTPS preauthentication.

Supported NetScaler Platforms for DirectAccess SSL Offloading

The following configuration for Citrix NetScaler can be performed on any release of the VPX virtual ADC platform. However, be advised that there is a known issue with older releases on the MDX and SDX hardware platforms that will prevent this from working. For MDX and SDX deployments, upgrading to release 11.1 build 50.10 or later will be required.

Configure Citrix NetScaler for IP-HTTPS SSL Offload

To enable SSL offloading for DirectAccess IP-HTTPS on the Citrix NetScaler, open the NetScaler management console, expand Traffic Management and Load Balancing, and then perform the following procedures in order.

Add Servers

  1. Click Servers.
  2. Click Add.
  3. In the Name field enter a descriptive name for the first DirectAccess server.
  4. Select IP Address.
  5. In the IP Address field enter the IP address of the first DirectAccess server.
  6. Click Create.
  7. Repeat these steps for any additional servers in the load-balanced cluster.

DirectAccess SSL Offload and IP-HTTPS Preauthentication with Citrix NetScaler

Add Services

  1. Click Services.
  2. Click Add.
  3. In the Service Name field enter a descriptive name for the service.
  4. Select Existing Server from the Server drop-down list.
  5. Choose the first DirectAccess server in the cluster.
  6. Choose SSL from the Protocol drop-down list.
  7. Click Ok.DirectAccess SSL Offload and IP-HTTPS Preauthentication with Citrix NetScaler
  8. Edit SSL Parameters.
    1. In the Protocol section uncheck SSLv3.
    2. Click Ok.
  9. Edit SSL Ciphers.
    1. Click Remove All.
    2. Click Add.
    3. Type NULL in the Search Ciphers box.
    4. Check the box next to the first entry for SSL3-NULL-SHA.
    5.  Click the right arrow to add the cipher to the list.
    6. Click Ok.
    7. Click Done.
    8. Repeat these steps for any additional servers in the load-balanced cluster.DirectAccess SSL Offload and IP-HTTPS Preauthentication with Citrix NetScaler

A warning message may be displayed indicating that no usable ciphers are configured on the SSL vserver/service. This message can be safely ignored.

DirectAccess SSL Offload and IP-HTTPS Preauthentication with Citrix NetScaler

Add Virtual Server

  1. Click Virtual Servers.
    1. Click Add.
    2. In the Name field enter a descriptive name for the virtual server.
    3. Choose SSL from the Protocol drop-down list.
    4. In the IP Address field enter the IP address for the virtual server.
    5. Click Ok.DirectAccess SSL Offload and IP-HTTPS Preauthentication with Citrix NetScaler

      Note: When enabling load balancing in DirectAccess, the IP address assigned to the first DirectAccess server is reallocated for use as the load balancing Virtual IP Address (VIP). Ideally this IP address will be assigned to the load balancing virtual server on the NetScaler. However, this is not a hard requirement. It is possible to configure the VIP on the NetScaler to reside on any subnet that the load balancer has an interface to. More details here.


  2. In the Services and Groups section click No Load Balancing Virtual Server Service Binding.
    1. Click on the Select Service field.
    2. Check all DirectAccess server services and click Select.
    3. Click Bind.
    4. Click Continue.
  3. In the Certificate section click No Server Certificate.
    1. Click on the Select Server Certificate field.
    2. Choose the certificate to be used for DirectAccess IP-HTTPS.
    3. Click Select.
    4. Click Bind.
    5. Click Continue.
  4. Edit SSL Ciphers.
    1. Click Remove All.
    2. Click Add.
    3. Type ECDHE in to the Search Ciphers box.
    4. Check the box next to TLS1-ECDHE-RSA-AES128-SHA.
    5. Click the right arrow to add the cipher to the list.
    6. Type NULL in to the Search Ciphers box.
    7. Check the box next to SSL3-NULL-SHA.
    8. Click the right arrow to add the cipher to the list.
    9. Click Ok.
    10. Click Done.DirectAccess SSL Offload and IP-HTTPS Preauthentication with Citrix NetScaler

      Note: If Windows 8.x/10 clients are supported exclusively, SSL3-NULL-SHA is the only cipher suite required to be configured on the virtual server. If Windows 7 client support is required, the TLS1-ECDHE-RSA-AES128-SHA cipher suite should also be configured on the virtual server.


  5. Edit SSL Parameters.
    1. Uncheck SSLv3.
    2. Click Ok.

      Note: If Windows 8.x/10 clients are supported exclusively, TLSv1 can also be unchecked on the virtual server. If Windows 7 client support is required, TLSv1 must be enabled.


  6. In the Advanced Settings section click Persistence.
    1. Choose SSLSESSION.
    2. Enter 10 minutes for the Time-out (mins) value.
    3. Click Ok.
    4. Click Done.

Optional IP-HTTPS Preauthentication

To enable IP-HTTPS preauthentication to prevent unauthorized network access, perform the following procedures on the Citrix NetScaler appliance.

  1. Expand Traffic Management, Load Balancing, and then click Virtual Servers.
  2. Select the DirectAccess virtual server and click Edit.
    1. In the Certificate section click No CA Certificate.
    2. Click the Select CA Certificate field.
    3. Choose the certificate for the CA that issues certificates to DirectAccess clients and servers.

      Note: The CA certificate used for DirectAccess can be found by opening the Remote Access Management console, clicking Edit on Step 2, and then clicking Authentication. Alternatively, the CA certificate can be found by running the following PowerShell command.

      (Get-RemoteAccess).IPsecRootCertificate | Format-Table Thumbprint


    4. Click Select.
    5. Choose CRL Optional from the CRL and OCSP Check drop-down list.
    6. Click Bind.
  3. Edit SSL Parameters.
    1. Check the box next to Client Authentication.
    2. Choose Mandatory from the Client Certificate drop-down list.
    3. Click Ok.
    4. Click Done.
      DirectAccess SSL Offload and IP-HTTPS Preauthentication with Citrix NetScaler

Summary

Leveraging the advanced capabilities of the Citrix NetScaler ADC can improve performance when supporting Windows 7 clients and enhance security for all DirectAccess clients using IP-HTTPS. In terms of supportability, all of the changes described in this article are completely transparent and do not alter the native DirectAccess client or server configuration. If a Microsoft support engineer declines support due to this configuration, switching from SSL offload to SSL bridge is all that’s required to restore full supportability.

Additional Resources

NetScaler release 11.1 build 50.10 (requires login) – https://www.citrix.com/downloads/netscaler-adc/firmware/release-111-build-5010

Release notes for build 50.10 of NetScaler 11.1 release – https://www.citrix.com/content/dam/citrix/en_us/documents/downloads/netscaler-adc/NS_11_1_50_10.html

VIDEO: Enable Load Balancing for DirectAccess – https://www.youtube.com/watch?v=3tdqgY9Y-uo

DirectAccess IP-HTTPS preauthentication using F5 BIG-IP – https://directaccess.richardhicks.com/2016/05/23/directaccess-ip-https-preauthentication-using-f5-big-ip/

DirectAccess SSL offload for IP-HTTPS using F5 BIG-IP – https://directaccess.richardhicks.com/2013/07/10/ssl-offload-for-ip-https-directaccess-traffic-from-windows-7-clients-using-f5-big-ip/

Implementing DirectAccess with Windows Server 2016 book – http://directaccessbook.com/

DirectAccess and OTP with PointSharp ID Webinar

Integrating multifactor authentication is essential for providing the highest level of security and assurance for DirectAccess clients. Smart cards work well for this, but they impose a heavy burden in terms of expense and administrative overhead. A more effective alternative is to use a One-Time Password (OTP) solution such as PointSharp ID.

DirectAccess and PointSharp ID Webinar

To learn more about the PointSharp ID OTP solution and how it integrates with DirectAccess, join me for a live webinar on Tuesday, July 27, 2106 at 10:00AM PDT where I’ll discuss the following topics.

  • What DirectAccess security risks can be mitigated with OTP?
  • What are the supporting infrastructure requirements for OTP authentication?
  • How to integrate the PointSharp IP solution with DirectAccess

You can register for this free live webinar here.

DirectAccess IP-HTTPS Preauthentication using F5 BIG-IP

Note: For information about configuring the Citrix NetScaler to perform IP-HTTPS preauthentication, click here. For information about configuring Windows Server 2012 R2 to perform IP-HTTPS preauthentication natively, click here.

Introduction

DirectAccess IP-HTTPS Preauthentication using F5 BIG-IPRecently I wrote about security challenges with DirectAccess and the IP-HTTPS IPv6 transition technology. Specifically, IP-HTTPS transition tunnel connections are not authenticated by the DirectAccess server, only the client. This allows an unauthorized device to obtain an IPv6 address on the DirectAccess client network. With it, an attacker can perform network reconnaissance using ICMPv6 and potentially launch a variety of Denial-of-Service (DoS) attacks. For more details, click here.

Note: DirectAccess IPsec data connections not at risk. Data is never exposed at any time with the default configuration.

Mitigation

To mitigate these issues, it is recommended that an Application Delivery Controller (ADC) be used to terminate SSL connections and enforce client certificate authentication. Doing this will ensure that only authorized connections will be accepted by the DirectAccess server. In addition, there are some scalability and performance benefits to implementing this configuration when supporting Windows 7 clients.

Important Considerations

Performing IP-HTTPS preauthentication on the F5 BIG-IP is formally unsupported by Microsoft. In addition, terminating IP-HTTPS on the F5 appliance breaks OTP authentication.

F5 BIG-IP Configuration

To configure the F5 BIG-IP to perform SSL offload for DirectAccess IP-HTTPS, follow the guidance documented here. In addition, to configure the F5 BIG-IP to perform preauthentication for DirectAccess clients, when creating the client SSL profile, click Custom above the Client Authentication section and choose Require from the Client Certificate drop-down list and Always from the Frequency drop-down list. In addition, choose your internal PKI’s root Certification Authority (CA) certificate from the Trusted Certificate Authorities drop-down list and from the Advertised Certificate Authorities drop-down list.

DirectAccess IP-HTTPS Preauthentication using F5 BIG-IP

Summary

Enabling client certificate authentication for IP-HTTPS connections ensures that only authorized DirectAccess clients can establish a connection to the DirectAccess server and obtain an IPv6 address. It also prevents an unauthorized user from performing network reconnaissance or launching IPv6 Denial-of-Service (DoS) attacks.

Configuring Multiple Windows Server 2012 R2 DirectAccess Instances

DirectAccess in Windows Server 2012 R2 supports many different deployment configurations. It can be deployed with a single server, multiple servers in a single location, multiple servers in multiple locations, edge facing, in a perimeter or DMZ network, etc.

Global Settings

There are a number of important DirectAccess settings that are global in scope and apply to all DirectAccess clients, such as certificate authentication, force tunneling, one-time password, and many more. For example, if you configure DirectAccess to use Kerberos Proxy instead of certificates for authentication, Windows 7 clients are not supported. In this scenario it is advantageous to have a second parallel DirectAccess deployment configured specifically for Windows 7 clients. This allows Windows 8 clients to take advantage of the performance gains afforded by Kerberos Proxy, while at the same time providing an avenue of support for Windows 7 clients.

Parallel Deployments

To the surprise of many, it is indeed possible to deploy DirectAccess more than once in an organization. I’ve been helping customers deploy DirectAccess for nearly five years now, and I’ve done this on more than a few occasions. In fact, there are some additional important uses cases that having more than one DirectAccess deployment can address.

Common Use Cases

QA and Testing – Having a separate DirectAccess deployment to perform testing and quality assurance can be quite helpful. Here you can validate configuration changes and verify updates without potential negative impact on the production deployment.

Delegated Administration – DirectAccess provides support for geographic redundancy, allowing administrators to create DirectAccess entry points in many different locations. DirectAccess in Windows Server 2012 R2 lacks support for delegated administration though, and in some cases it may make more sense to have multiple separate deployments as opposed to a single, multisite deployment. For example, many organizations are divided in to different business units internally and may operate autonomously. They may also have different configuration requirements, which can be better addressed using individual DirectAccess implementations.

Migration – If you have currently deployed DirectAccess using Windows Server 2008 R2 with or without Forefront UAG 2010, migrating to Windows Server 2012 R2 can be challenging because a direct, in-place upgrade is not supported. You can, however, deploy DirectAccess using Windows Server 2012 R2 in parallel to your existing deployment and simply migrate users to the new solution by moving the DirectAccess client computer accounts to a new security group assigned to the new deployment.

Major Configuration Changes – This strategy is also useful for scenarios where implementing changes to the DirectAccess configuration would be disruptive for remote users. For example, changing from a single site to a multisite configuration would typically require that all DirectAccess clients be on the LAN or connect remotely out-of-band to receive group policy settings changes after multisite is first configured. In addition, parallel deployments can significantly ease the pain of transitioning to a new root CA if required.

Unique Client Requirements – Having a separate deployment may be required to take advantage of the unique capabilities of each client operating system. For example, Windows 10 clients do not support Microsoft Network Access Protection (NAP) integration. NAP is a global setting in DirectAccess and applies to all clients. If you still require NAP integration and endpoint validation using NAP for Windows 7 and Windows 8.x, another DirectAccess deployment will be required to support Windows 10 clients.

Requirements

To support multiple Windows Server 2012 R2 DirectAccess deployments in the same organization, the following is required:

Unique IP Addresses – It probably goes without saying, but each DirectAccess deployment must have unique internal and external IPv4 addresses.

Distinct Public Hostname – The public hostname used for each deployment must also be unique. Multi-SAN certificates have limited support for DirectAccess IP-HTTPS (public hostname must be the first entry in the list), so consider using a wildcard certificate or obtain certificates individually for each deployment.

Group Policy Objects – You must use unique Active Directory Group Policy Objects (GPOs) to support multiple DirectAccess deployments in a single organization. You have the option to specify a unique GPO when you configure DirectAccess for the first time by clicking the Change link next to GPO Settings on the Remote Access Review screen.

Configuring Multiple Windows Server 2012 R2 DirectAccess Instances

Enter a distinct name for both the client and server GPOs. Click Ok and then click Apply to apply the DirectAccess settings for this deployment.

Configuring Multiple Windows Server 2012 R2 DirectAccess Instances

Windows 7 DirectAccess Connectivity Assistant (DCA) GPOs – If the DirectAccess Connectivity Assistant (DCA) v2.0 has been deployed for Windows 7 clients, separate GPOs containing the DCA client settings for each individual deployment will have to be configured. Each DirectAccess deployment will have unique Dynamic Tunnel Endpoint (DTE) IPv6 addresses which are used by the DCA to confirm corporate network connectivity. The rest of the DCA settings can be the same, if desired.

Supporting Infrastructure

The rest of the supporting infrastructure (AD DS, PKI, NLS, etc.) can be shared between the individual DirectAccess deployments without issue. Once you’ve deployed multiple DirectAccess deployments, make sure that DirectAccess clients DO NOT belong to more than one DirectAccess client security group to prevent connectivity issues.

Migration Process

Moving DirectAccess client computers from the old security group to the new one is all that’s required to migrate clients from one DirectAccess deployment to another. Client machines will need to be restarted to pick up the new security group membership, at which time they will also get the DirectAccess client settings for the new deployment. This works seamlessly when clients are on the internal network. It works well for clients that are outside the network too, for the most part. Because clients must be restarted to get the new settings, it can take some time before all clients finally moved over. To speed up this process it is recommended that DirectAccess client settings GPOs be targeted at a specific OUs created for the migration process. A staging OU is created for clients in the old deployment and a production OU is created for clients to be assigned to the new deployment. DirectAccess client settings GPOs are then targeted at those OUs accordingly. Migrating then only requires moving a DirectAccess client from the old OU to the new one. Since OU assignment does not require a reboot, clients can be migrated much more quickly using this method.

Summary

DirectAccess with Windows Server 2012 R2 supports many different deployment models. For a given DirectAccess deployment model, some settings are global in scope and may not provide the flexibility required by some organizations. To address these challenges, consider a parallel deployment of DirectAccess. This will enable you to take advantage of the unique capabilities of each client operating system, or allow you to meet the often disparate configuration requirements that a single deployment cannot support.

Hotfix Available for DirectAccess OTP Configuration Issues

If you’ve ever tried configuring DirectAccess to use One-Time Password (OTP) authentication, you’ve no doubt discovered that the native Microsoft Remote Access Management console would return the following error when trying to detect and locate Certificate Authority (CA) servers.

No CA servers can be detected, and OTP cannot be configured. Ensure that
servers added to the list are available on each domain controller in the
corporate network.

Configure DirectAccess with OTP Authentication

The workaround for this issue required dropping to the command line and executing PowerShell commands to complete this configuration as I outlined here.

Thankfully Microsoft has made available a hotfix to address this issue, returning full GUI functionality for configuring DirectAccess and OTP authentication. For additional details about this hotfix and to request the update itself, click here.

Configure DirectAccess with OTP Authentication

Updated 6/10/2015: This post was revised to include instructions for enabling OTP support for Windows 7 clients and for configuring OTP on the DirectAccess server using the Remote Access Management console.

Introduction

DirectAccess in Windows Server 2012 R2 provides significantly improved authentication over traditional client-based VPN solutions. When configured to use certificate authentication (a recommended best practice) the DirectAccess client is authenticated using its machine certificate and its Active Directory computer account. Once the client machine has been authenticated, the user is also authenticated via Kerberos against a live domain controller over the existing DirectAccess connection. These multiple authentication steps provide a high level of assurance for DirectAccess-connected clients. If that’s not enough to meet your needs, additional strong user authentication is supported using dynamic One-Time Passwords (OTP).

Drawbacks for DirectAccess with OTP

While OTP provides an additional level of assurance, it does come with a few drawbacks. OTP adds additional complexity and makes troubleshooting more difficult. OTP cannot be configured with force tunneling; the two security features are mutually exclusive. DirectAccess OTP does not support RADIUS challenge-response. For Windows 7 clients, the DirectAccess Connectivity Assistant (DCA) v2.0 must be deployed. In addition, enabling OTP with DirectAccess disables the use of null cipher suites for IP-HTTPS. This can potentially have a negative effect on performance and scalability (more details here). Also, OTP fundamentally breaks the seamless and transparent nature of DirectAccess.

Configuring DirectAccess OTP

OTP for DirectAccess makes use of short-lived certificates for user authentication. Thus, enabling OTP for DirectAccess requires making changes to the internal Public Key Infrastructure (PKI). DirectAccess in Windows Server 2012 R2 can be configured to use the same Certificate Authority (CA) that is used to issue computer certificates to the DirectAccess clients and servers. This differs from DirectAccess with Forefront Unified Access Gateway (UAG) 2010, where a separate, dedicated CA was required.

To configure DirectAccess OTP, follow the instructions below.

OTP Certificate Request Signing Template

Open the Certification Authority management console, right-click Certificate Templates, and then choose Manage. Alternatively you can enter certtmpl.msc in the Start/Run box or search from the Windows Start menu. Right-click the Computer template and choose Duplicate Template. On a Windows Server 2008 or 2008 R2 CA, select Windows Server 2008 Enterprise when prompted for the duplicate certificate template version.

Configure DirectAccess with OTP Authentication

On a Windows Server 2012 or 2012 R2 CA, select Compatibility tab and then select Windows Server 2008 R2 for the Certification Authority and Windows 7/Windows Server 2008 R2 for the Certificate recipient.

Configure DirectAccess with OTP Authentication

Select the General tab and provide a descriptive name for the Template Display Name. Specify a validity period of 2 days and a renewal period of 1 day.

Configure DirectAccess with OTP Authentication

Select the Security tab and click Add. Click Object Types and then select Computers and click Ok. Enter the names of each DirectAccess server separated by semicolons and click Check Names. Click Ok when finished. For each DirectAccess server, grant Read, Enroll, and Autoenroll permissions. Select Authenticated Users and remove any permissions other than Read. Select Domain Computers and remove the Enroll permission. Select Domain Admins and grant Full Control permission. Do the same for Enterprise Admins.

Configure DirectAccess with OTP Authentication

Select the Subject Name tab and choose the option to Build from this Active Directory information. Select DNS name in the Subject name format drop-down list and confirm that DNS name is checked under Include this information in alternate subject name.

Configure DirectAccess with OTP Authentication

Select the Extensions tab, highlight Application Policies and click Edit.

Configure DirectAccess with OTP Authentication

Remove all existing application policies and then click Add and then New. Provide a descriptive name for the new application policy and enter 1.3.6.1.4.1.311.81.1.1 for the Object Identifier. Click Ok for all remaining dialog boxes.

Configure DirectAccess with OTP Authentication

OTP Certificate Template

In the Certificate Templates Console, right-click the Smartcard Logon certificate template and choose Duplicate Template. On a Windows Server 2008 or 2008 R2 CA, select Windows Server 2008 Enterprise when prompted for the duplicate certificate template version.

Configure DirectAccess with OTP Authentication

On a Windows Server 2012 or 2012 R2 CA, select the Compatibility tab and then select Windows Server 2008 R2 for the Certification Authority and Windows 7/Windows Server 2008 R2 for the Certificate recipient.

Configure DirectAccess with OTP Authentication

Select the General tab and provide a descriptive name for the Template Display Name. Specify a validity period of 1 hour and a renewal period of 0 hours.

Configure DirectAccess with OTP Authentication

Note: It is not possible to set the validity period to hours on a Windows Server 2003 Certificate Authority (CA). As a workaround, use the Certificate Templates snap-in on another system running Windows 7/Windows Server 2008 R2 or later. Also, if the CA is running Windows Server 2008 R2, the template must be configured to use a Renewal Period of 1 or 2 hours and a Validity Period that is longer but no more than 4 hours.

Select the Security tab, then highlight Authenticated Users and grant Read and Enroll permissions. Select Domain Admins and grant Full Control permission. Do the same for Enterprise Admins.

Configure DirectAccess with OTP Authentication

Select the Subject Name tab and choose the option to Build from this Active Directory information. Select Fully distinguished name in the Subject name format drop-down list and confirm that User principal name (UPN) is checked under Include this information in alternate subject name.

Configure DirectAccess with OTP Authentication

Select the Server tab and choose the option Do not store certificates and requests in the CA database. Clear the checkbox next to Do not include revocation information issued in certificates.

Configure DirectAccess with OTP Authentication

Select the Issuance Requirements tab and set the value for This number of authorized signatures to 1. Confirm that Application Policy is selected from the Policy type required in signature drop-down list and choose the OTP certificate request signing template created previously.

Configure DirectAccess with OTP Authentication

Select the Extensions tab, highlight Application Policies and click Edit. Highlight Client Authentication and click Remove. Ensure that the only application policy listed is Smart Card Logon.

Configure DirectAccess with OTP Authentication

Certificate Authority Configuration

In the Certificate Authority management console, right-click Certificate Templates, choose New, and then Certificate Template to Issue. Highlight both of the certificate templates created previously and click Ok.

Configure DirectAccess with OTP Authentication

Open an elevated command prompt and enter the following command:

certutil.exe -setreg dbflags +DBFLAGS_ENABLEVOLATILEREQUESTS

Configure DirectAccess with OTP Authentication

Restart the Certificate Authority service by right-clicking the CA in the Certificate Authority management console and choosing All Tasks and then Stop Service. Once complete, repeat these steps and choose Start Service.

DirectAccess Server Configuration

In the Remote Access Management console, select DirectAccess and VPN under Configuration in the navigate pane and then click Edit on Step 2 – Remote Access Server. Select Authentication, choose Two-factor authentication (smart card or one-time password (OTP)), and then check the option to Use OTP.

Configure DirectAccess with OTP Authentication

Click Next and then add the RADIUS servers that will be used for OTP authentication. Provide the hostname, FQDN, or IP address of the server, the shared secret, and specify the service port.

Configure DirectAccess with OTP Authentication

Click Next, select the CA server that will be used to issue certificates to DirectAccess clients for OTP authentication, and then click Add.

Click Next, select the CA server that will be used to issue certificates to DirectAccess clients for OTP authentication, and then click Add.

Note: When performing this step you may receive the following error.

No CA servers can be detected, and OTP cannot be configured. Ensure that
servers added to the list are available on each domain controller in the
corporate network.

Configure DirectAccess with OTP Authentication

If this occurs, close out of the Remote Access Management console and install this hotfix.

Click Next and select the certificate templates to be used for the enrollment of certificates that are issued for OTP authentication. Also select a certificate template used to enroll the certificate used by the DirectAccess server to sign OTP certificate enrollment requests.

Configure DirectAccess with OTP Authentication

Click Next and specify whether selected DirectAccess users can authenticate with a user name and password when OTP authentication is disabled. If some users need to be exempted from using OTP, specify the security group as required and click Finish.

Configure DirectAccess with OTP Authentication

Click Edit on Step 3 – Infrastructure Servers. Select Management and add the CA server used for OTP authentication to the list of management servers.

Configure DirectAccess with OTP Authentication

Click Ok and then Finish. Click Finish once more and then apply the changes.

DirectAccess OTP Client Experience

When a DirectAccess client is outside of the corporate network and has established DirectAccess connectivity, users can log on to their machine and access their desktop, but they will not be able to access corporate resources without first providing their OTP.

For Windows 8 clients, swipe in from the right side of the screen or press Window Key + I and click on the active network connection. The DirectAccess Workplace Connection will indicate that action is needed. Clicking on the Workplace Connection will indicate that credentials are needed. Clicking Continue will prompt the user to press Ctrl+Alt+Delete and provide their OTP.

Configure DirectAccess with OTP Authentication

For Windows 7 clients, an alert from the DirectAccess Connectivity Assistant (DCA) in the system tray will indicate that Windows needs your smart card credentials. Clicking on the notification Window will prompt the user to provide their OTP.

Configure DirectAccess with OTP Authentication

Alternatively the user can click on the DCA icon in the system tray and then click Lock and unlock your computer with a smartcard or a one-time password. The user will then press CTRL+ALT+DELETE, choose Other Credentials, select One-time password (OTP), and then provide their OTP.

Configure DirectAccess with OTP Authentication

Summary

Using dynamic, one-time passwords is an effective way to provide the highest level of assurance for remote DirectAccess clients. It does come with some potential drawbacks, so be sure to consider those before implementing OTP.

Forefront UAG 2010 DirectAccess Clients and Repeated OTP Prompts

In a very specific DirectAccess deployment scenario it is possible that users may be prompted repeatedly for One-Time Password (OTP) credentials. Specifically this may occur when you have Windows 7 clients accessing a Forefront UAG 2010 DirectAccess server with two-factor authentication enabled with OTP, along with forced tunneling required and the client configured to use a corporate web proxy server. The root cause of the issue has to do with Network Connectivity Status Indicator (NCSI) probes and security permissions on the private key of the certificate used for OTP authentication. To resolve the issue will require creating a custom certificate template for use with two-factor authentication and setting key permissions for the NETWORK SERVICE on the certificate template. You can also workaround this issue by disabling forced tunneling or disabling the 6to4 and Teredo adapters, which will stop the NCSI probes from occurring. For more detailed information read Microsoft KB article 2797301.

Microsoft DirectAccess Connectivity Assistant 2.0 Now Available

Recently Microsoft announced the availability of the DirectAccess Connectivity Assistant (DCA) v2.0. DCA v2.0 is required to be installed on Windows 7 DirectAccess clients when they are connecting to a DirectAccess Server running Windows Server 2012. It is important to note that DCA v2.0 is not required (and should not be installed) on Windows 8 DirectAccess clients. In addition, DCA v2.0 should not be installed on Windows 7 DirectAccess clients when they are connecting to a Windows Server 2008 R2/Forefront UAG 2010 DirectAccess server. For Windows 7 DirectAccess clients accessing corporate network resources over Windows Server 2008 R2/Forefront UAG 2010, install DCA v1.5. DCA v1.5 can be found on the Forefront UAG server at C:\Program Files\Microsoft Forefront Unified Access Gateway\common\bin\da\dca.

The DCA provides DirectAccess users with connectivity status information, detailed diagnostics and troubleshooting, and is required to support One-Time Password (OTP) authentication. You can download DCA v2.0 here.

%d bloggers like this: