Troubleshooting DirectAccess IP-HTTPS Error Code 0x90320

A Windows 7 or Windows 8.x/10 client may fail to establish a DirectAccess connection using the IP-HTTPS IPv6 transition technology. When troubleshooting this issue, running ipconfig.exe shows that the media state for the tunnel adapter iphttpsinterface is Media disconnected.

Troubleshooting DirectAccess IP-HTTPS Error Code 0x90320

Running the Get-NetIPHttpsState PowerShell command on Windows 8.x/10 clients or the netsh interface httpstunnel show interface command on Windows 7 clients returns an error code of 0x90320, with an interface status Failed to connect to the IPHTTPS server; waiting to reconnect.

Troubleshooting DirectAccess IP-HTTPS Error Code 0x90320

Error code 0x90320 translates to SEC_I_INCOMPLETE_CREDENTIALS, indicating the client was unable to authenticate to the DirectAccess server during the TLS handshake when establishing the IP-HTTPS IPv6 transition tunnel. This occurs when the DirectAccess server or an Application Delivery Controller (ADC) is configured to perform client certificate authentication for IP-HTTPS connections. The client may fail to authenticate if it does not have a valid certificate issued by the organization’s internal certification authority (CA) or if the DirectAccess server or ADC is configured to perform IP-HTTPS client authentication incorrectly.

To resolve this issue, ensure that a valid certificate is installed on the DirectAccess client. In addition, ensure that the DirectAccess server or ADC is configured to use the correct CA when authenticating clients establishing IP-HTTPS connections.

Additional Information

DirectAccess IP-HTTPS Preauthentication 

DirectAccess IP-HTTPS Preauthentication using Citrix NetScaler

DirectAccess SSL Offload and IP-HTTPS preauthentication using Citrix NetScaler 

DirectAccess IP-HTTPS preauthentication using F5 BIG-IP 

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 Training at TechMentor Conference Orlando 2016

Live! 360 Orlando 2016I am pleased to announce that I’ll be participating in the upcoming TechMentor conference in Orlando, FL in December. The TechMentor conference is part of the larger Live!360 event and offers a compelling agenda of training for IT professionals. I’ll be delivering the following sessions that are focused on providing secure remote access using Windows Server 2016.

TMT01 – Implementing DirectAccess in Windows Server 2016
TMT04 – DirectAccess Troubleshooting Deep Dive
TMT11 – Client-based VPN in Azure with Windows Server 2016

Don’t miss out on this outstanding conference. Register today and save $500.00!

Deploying DirectAccess in Microsoft Azure

Introduction

DirectAccess Now a Supported Workload in Microsoft AzureMany organizations are preparing to implement DirectAccess on Microsoft’s public cloud infrastructure. Deploying DirectAccess in Azure is fundamentally no different than implementing it on premises, with a few important exceptions (see below). This article provides essential guidance for administrators to configure this unique workload in Azure.

Important Note: There has been much confusion regarding the supportability of DirectAccess in Azure. Historically it has not been supported. Recently, it appeared briefly that Microsoft reversed their earlier decision and was in fact going to support it. However, the Microsoft Server Software Suport for Microsoft Azure Virtual Machines document has once again been revised to indicate that DirectAccess is indeed no longer formally supported on Azure. More details can be found here.

Azure Configuration

The following is guidance for configuring network interfaces, IP address assignments, public DNS, and network security groups for deploying DirectAccess in Azure.

Virtual Machine

Deploy a virtual machine in Azure with sufficient resources to meet expected demand. A minimum of two CPU cores should be provisioned. A VM with 4 cores is recommended. Premium storage on SSD is optional, as DirectAccess is not a disk intensive workload.

Network Interfaces

It is recommended that an Azure VM with a single network interface be provisioned for the DirectAccess role. This differs from on-premises deployments where two network interfaces are preferred because deploying VMs in Azure with two NICs is prohibitively difficult. At the time of this writing, Azure VMs with multiple network interfaces can only be provisioned using PowerShell, Azure CLI, or resource manager templates. In addition, Azure VMs with multiple NICs cannot belong to the same resource group as other VMs. Finally, and perhaps most importantly, not all Azure VMs support multiple NICs.

Internal IP Address

Static IP address assignment is recommended for the DirectAccess VM in Azure. By default, Azure VMs are initially provisioned using dynamic IP addresses, so this change must be made after the VM has been provisioned. To assign a static internal IP address to an Azure VM, open the Azure management portal and perform the following steps:

  1. Click Virtual machines.
  2. Select the DirectAccess server VM.
  3. Click Network Interfaces.
  4. Click on the network interface assigned to the VM.
  5. Under Settings click IP configurations.
  6. Click Ipconfig1.
  7. In the Private IP address settings section choose Static for the assignment method.
  8. Enter an IP address for the VM.
  9. Click Save.

Deploying DirectAccess in Microsoft Azure

Public IP Address

The DirectAccess VM in Azure must have a public IP address assigned to it to allow remote client connectivity. To assign a public IP address to an Azure VM, open the Azure management portal and perform the following steps:

  1. Click Virtual machines.
  2. Select the DirectAccess server VM.
  3. Click Network Interfaces.
  4. Click on the network interface assigned to the VM.
  5. Under Settings click IP configurations.
  6. Click Ipconfig1.
  7. In the Public IP address settings section click Enabled.
  8. Click Configure required settings.
  9. Click Create New and provide a descriptive name for the public IP address.
  10. Choose an address assignment method.
  11. Click Ok and Save.

Deploying DirectAccess in Microsoft Azure

Deploying DirectAccess in Microsoft Azure

Public DNS

If the static IP address assignment method was chosen for the public IP address, create an A resource record in public DNS that resolves to this address. If the dynamic IP address assignment method was chosen, create a CNAME record in public DNS that maps to the public hostname for the DirectAccess server. To assign a public hostname to the VM in Azure, open the Azure management portal and perform the following steps:

  1. Click Virtual machines.
  2. Select the DirectAccess server VM.
  3. Click Overview.
  4. Click Public IP address/DNS name label.Deploying DirectAccess in Microsoft Azure
  5. Under Settings click Configuration.
  6. Choose an assignment method (static or dynamic).
  7. Enter a DNS name label.
  8. Click Save.

Deploying DirectAccess in Microsoft Azure

Note: The subject of the SSL certificate used for the DirectAccess IP-HTTPS listener must match the name of the public DNS record (A or CNAME) entered previously. The SSL certificate does not need to match the Azure DNS name label entered here.

Network Security Group

A network security group must be configured to allow IP-HTTPS traffic inbound to the DirectAccess server on the public IP address. To make the required changes to the network security group, open the Azure management portal and perform the following steps:

  1. Click Virtual machines.
  2. Select the DirectAccess server VM.
  3. Click Network interfaces.
  4. Click on the network interface assigned to the VM.
  5. Under Settings click Network security group.
  6. Click the network security group assigned to the network interface.
  7. Click Inbound security rules.
  8. Click Add and provide a descriptive name for the new rule.
  9. Click Any for Source.
  10. From the Service drop-down list choose HTTPS.
  11. Click Allow for Action.
  12. Click Ok.

Deploying DirectAccess in Microsoft Azure

Note: It is recommended that the default-allow-rdp rule be removed if it is not needed. At a minimum, scope the rule to allow RDP only from trusted hosts and/or networks.

DirectAccess Configuration

When performing the initial configuration of DirectAccess using the Remote Access Management console, the administrator will encounter the following warning message.

“One or more network adapters should be configured with a static IP address. Obtain a static address and assign it to the adapter.”

Deploying DirectAccess in Microsoft Azure

This message can safely be ignored because Azure infrastructure handles all IP address assignment for hosted VMs.

The public name of the DirectAccess server entered in the Remote Access Management console must resolve to the public IP address assigned to the Azure VM, as described previously.

Deploying DirectAccess in Microsoft Azure

Additional Considerations

When deploying DirectAccess in Azure, the following limitations should be considered.

Load Balancing

It is not possible to enable load balancing using Windows Network Load Balancing (NLB) or an external load balancer. Enabling load balancing for DirectAccess requires changing static IP address assignments in the Windows operating system directly, which is not supported in Azure. This is because IP addresses are assigned dynamically in Azure, even when the option to use static IP address assignment is chosen in the Azure management portal. Static IP address assignment for Azure virtual machines are functionally similar to using DHCP reservations on premises.

Deploying DirectAccess in Microsoft Azure

Note: Technically speaking, the DirectAccess server in Azure could be placed behind a third-party external load balancer for the purposes of performing SSL offload or IP-HTTPS preauthentication, as outlined here and here. However, load balancing cannot be enabled in the Remote Access Management console and only a single DirectAccess server per entry point can be deployed.

Manage Out

DirectAccess manage out using native IPv6 or ISATAP is not supported in Azure. At the time of this writing, Azure does not support IPv6 addressing for Azure VMs. In addition, ISATAP does not work due to limitations imposed by the underlying Azure network infrastructure.

Summary

For organizations moving infrastructure to Microsoft’s public cloud, formal support for the DirectAccess workload in Azure is welcome news. Implementing DirectAccess in Azure is similar to on-premises with a few crucial limitations. By following the guidelines outlined in this article, administrators can configure DirectAccess in Azure to meet their secure remote access needs with a minimum of trouble.

Additional Resources

Implementing DirectAccess in Windows Server 2016
Fundamentals of Microsoft Azure 2nd Edition
Microsoft Azure Security Infrastructure
DirectAccess Multisite with Azure Traffic Manager
DirectAccess Consulting Services

DirectAccess and Windows 10 in Education

DirectAccess and Windows 10 in EducationIntroduction

DirectAccess provides seamless and transparent, always on remote network connectivity for managed Windows clients. It is commonly installed in large enterprises to provide better management for field-based assets, and to streamline the remote access experience for end users. Today, DirectAccess is a mature technology that is widely deployed across many verticals, but education is one that is often overlooked.

Benefits of DirectAccess

For commercial enterprises, the benefits of DirectAccess are many. Windows 10 DirectAccess clients have ubiquitous access to on-premises applications and data without requiring user interaction. This streamlined user access improves productivity and reduces helpdesk costs. DirectAccess is always on, allowing client machines to stay in contact with domain controllers and systems management servers, ensuring they are always managed.

DirectAccess in Education

Many of the same benefits DirectAccess provides for the enterprise are also important in the education sector. Often administrators for schools and colleges have many Windows-based machines that they must both manage and provide secure remote access for. In addition, they struggle with the same issues that enterprises do, such as maintaining configuration and security posture for devices that are predominantly remote.

Windows 10 and Education

Windows 10 November Update Available TodayThe Windows 10 Education SKU is a supported client operating system for DirectAccess, enabling educational institutions using this license to implement a remote access solution with DirectAccess using Windows Server 2012 R2 or Windows Server 2016. Implementing a DirectAccess remote access solution can result in significant cost savings, as DirectAccess requires no investments in proprietary hardware and has no associated per-user licensing.

Windows 10 Anniversary Update

Microsoft is making a concerted effort to address the education sector with new and compelling features to be included in the Windows 10 Anniversary Update, released earlier this week. For example, they have introduced apps that simplify the setup of school PCs. App discovery and purchasing are easier, and stylus support is improved. Native integration with Office 365 is another important factor. There are also a number of significant new security features that will make migrating to Windows 10 a worthy investment.

DirectAccess and Windows 10 in Education

Summary

If you are an administrator working for any educational institution and are struggling with maintaining and supporting your field-based Windows devices, consider a DirectAccess remote access solution today. With DirectAccess implemented, users will be more productive and remote machines better managed. DirectAccess can also be deployed using existing infrastructure, and it supports flexible network deployment along with many scalability features that will ensure the highest levels of availability.

Additional Resources

Video: DirectAccess and Windows 10 in Action
3 Important Things about Windows 10 and DirectAccess
DirectAccess and Windows 10 Better Together
DirectAccess Consulting Services
Book: Implementing DirectAccess with Windows Server 2016

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


Introduction

DirectAccess IP-HTTPS PreauthenticationRecently I’ve written about the security challenges with DirectAccess, specifically around the use of the IP-HTTPS IPv6 transition technology. In its default configuration, the DirectAccess server does not authenticate the client when an IP-HTTPS transition tunnel is established. This opens up the possibility of an unauthorized user launching Denial-of-Service (DoS) attacks and potentially performing network reconnaissance using ICMPv6. More details on this can be found here.

Mitigation

The best way to mitigate these security risks is to implement an Application Delivery Controller (ADC) such as the F5 BIG-IP Local Traffic Manager or the Citrix NetScaler. I’ve documented how to configure those platforms here and here.

No ADC?

For those organizations that do not have a capable ADC deployed, it is possible to configure the IP-HTTPS listener on the Windows Server 2012 R2 server itself to perform preauthentication.

Important Note: Making the following changes on the DirectAccess server is not formally supported. Also, this change is incompatible with one-time passwords (OTP)  and should not be performed if strong user authentication is enabled. In addition, null cipher suites will be disabled, resulting in reduced scalability and degraded performance for Windows 8.x and Windows 10 clients. Making this change should only be done if a suitable ADC is not available.

Configure IP-HTTPS Preauthentication

To configure the DirectAccess server to perform preauthentication for IP-HTTPS connections, open an elevated PowerShell command window and enter the following command.

ls Cert:\LocalMachine\My

DirectAccess IP-HTTPS Preauthentication

Copy the thumbprint that belongs to the SSL certificate assigned to the IP-HTTPS listener. Open an elevated command prompt window (not a PowerShell window!) and enter the following commands.

netsh http delete sslcert ipport=0.0.0.0:443
netsh http add sslcert ipport=0.0.0.0:443 certhash=[thumbprint]
appid={5d8e2743-ef20-4d38-8751-7e400f200e65}
dsmapperusage=enable clientcertnegotiation=enable

DirectAccess IP-HTTPS Preauthentication

For load-balanced clusters and multisite deployments, repeat these steps on each DirectAccess server in the cluster and/or enterprise.

Summary

Once these changes have been made, only DirectAccess clients that have a computer certificate with a subject name that matches the name of its computer account in Active Directory will be allowed to establish an IP-HTTPS transition tunnel connection.

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.

DirectAccess IP-HTTPS Preauthentication using Citrix NetScaler

Note: For information about configuring the F5 BIG-IP to perform IP-HTTPS preauthentication, click hereFor information about configuring Windows Server 2012 R2 or Windows Server 2016 to perform IP-HTTPS preauthentication natively, click here.

Introduction

DirectAccess IP-HTTPS Preauthentication using Citrix NetScalerIP-HTTPS is an IPv6 transition technology used by DirectAccess. It enables DirectAccess clients to communicate with the DirectAccess server using IPv6 over the public IPv4 Internet by encapsulating IPv6 packets in HTTP and authenticating (and optionally encrypting) them using SSL/TLS. IP-HTTPS is supported for all DirectAccess network deployment configurations and is enabled by default.

When a DirectAccess client connection is established, only the server is authenticated by the client. The client is not authenticated by the server. The DirectAccess server will thus accept IP-HTTPS connections from any client, valid or not.

IP-HTTPS Connection

Once a client has established an IP-HTTPS transition tunnel, it will go through the standard IPv6 neighbor discovery process to identify routers and obtain an IPv6 prefix for the link. It will use this information to build its own IPv6 address, which it uses to communicate with the DirectAccess server and begin establishing IPsec security associations for DirectAccess.

ICMP and IPsec

By design, ICMP is exempt from DirectAccess IPsec policy processing. If an unauthorized client were to establish an IP-HTTPS transition tunnel, even without authentication (Kerberos Proxy or certificate) it would be able to ping the DirectAccess server tunnel endpoint IPv6 addresses, the DNS64 IPv6 address, and any intranet hosts (assuming host firewalls allow this access).

Security Risk

This default posture opens up the DirectAccess server and intranet to unauthorized remote network reconnaissance and some IPv6-related Denial-of-Service (DoS) attacks. These were demonstrated by security researcher Ali Hardudi at the recent Troopers16 security conference. You can view his very informative session here.

Note: DirectAccess IPsec data connections are unaffected and are completely secure. Data is never exposed at any time with the default configuration.

IP-HTTPS Preauthentication

DirectAccess IP-HTTPS Preauthentication using Citrix NetScalerTo mitigate these risks, it is recommended that an Application Delivery Controller (ADC) such as the Citrix NetScaler be configured to preauthenticate DirectAccess clients prior to establishing the IP-HTTPS transition tunnel.

Note: To configure the F5 BIG-IP to perform IP-HTTPS preauthentication, click here.

Citrix NetScaler Configuration

To perform DirectAccess preauthentication, it will be necessary to configure the Citrix NetScaler to perform SSL termination for IP-HTTPS. The virtual server on the NetScaler must use the SSL protocol. In addition, a CA certificate must be bound to the virtual server. Also, Client Authentication must be enabled under SSL Parameters and be set to Mandatory.

DirectAccess IP-HTTPS Preauthentication using Citrix NetScaler

Once configured, the NetScaler appliance will ensure that the DirectAccess IPsec certificate is present on the client before establishing the IP-HTTPS IPv6 transition tunnel. This will prevent unauthorized connections to the DirectAccess server.

Important Considerations

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

Summary

The default security posture of DirectAccess leaves the internal network open to unauthorized network reconnaissance, and exposes the DirectAccess infrastructure to potential denial-of-service (DoS) attacks. To mitigate these security risks, implement the Citrix NetScaler ADC and enable client certificate authentication.

References

Security Assessment of Microsoft DirectAccess [Overview] – https://www.insinuator.net/2016/04/security-assessment-of-microsoft-directaccess/

Security Assessment of Microsoft DirectAccess [Full Document] – https://www.ernw.de/newsfeed/newsletter-53-may-2016-security-assessment-of-microsoft-directaccess/index.html

Security Assessment of Microsoft DirectAccess Troopers16 Presentation by Ali Hardudi [Video] – https://www.youtube.com/watch?v=wW1x7ow0V9w

Chiron IPv6 Penetration Testing Framework – https://www.insinuator.net/2014/10/chiron-an-all-in-one-ipv6-penetration-testing-framework/

IP-HTTPS specification on MSDN – https://msdn.microsoft.com/en-us/library/dd358571.aspx

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

Configure Windows Server 2012 R2  and Windows Server 2016 to Perform IP-HTTPS Preauthentication – https://directaccess.richardhicks.com/2016/06/13/directaccess-ip-https-preauthentication/

DirectAccess vs. VPN

Introduction

DirectAccess vs. VPNMany IT professionals mistakenly believe that DirectAccess is just another VPN solution. While there are some similarities between these technologies, both in terms of the underlying technology and function, there are some significant differences between the two. If you’re comparing DirectAccess to VPN, here are some essential points to consider.

VPN

Virtual Private Networking (VPN) has been around for ages. VPN is a mature, well understood technology that has been widely deployed, and today remains the de facto standard for providing secure remote access. VPN has broad client support, on both traditional computing platforms and mobile operating systems. VPNs today include support for modern protocols and integrate with numerous multifactor authentication platforms.

VPN Challenges

There are some serious drawbacks to implementing traditional client-based VPN. VPN connections are user initiated and therefore optional. It is up to the user to decide if and when they connect to the corporate network. Many VPNs require additional software to work, which must be deployed and maintained. Establishing connections is potentially problematic too, as some VPN protocols aren’t firewall friendly and don’t work in many locations.

DirectAccess vs. VPNFrom a security perspective, because anyone can attempt a connection to the VPN from any client, strong authentication becomes an essential requirement. Integrating multifactor authentication makes the implementation more complex and difficult to support. It often requires additional hardware, licensing, and support costs.

VPNs can be costly to implement and support. They typically require expensive proprietary hardware and dedicated management skill sets. Many VPN solutions also have additional licensing costs associated with them. Scaling a VPN solution requires additional investments in hardware devices, adding to the overall cost of the solution.

DirectAccess

DirectAccess is a relative newcomer to the world of secure remote access. First introduced with Windows Server 2008 R2, DirectAccess differs fundamentally from VPN by virtue of its seamless and transparent, always-on connection. DirectAccess connections are established by the machine, not the user. They are secure and authenticated, and are established automatically whenever the DirectAccess client has an active Internet connection. DirectAccess connections are also bidirectional, which is an important distinction. The ability to “manage out” to remote connected DirectAccess clients enables compelling new uses cases for IT administrators.

Addressing VPN Pain Points with DirectAccess

DirectAccess vs. VPNDirectAccess connections are inherently more secure than VPN. Unlike VPN, DirectAccess clients must be joined to the domain and, in most configurations, they must also have a certificate issued by the organization’s private, internal Public Key Infrastructure (PKI). This essentially serves as a type of multifactor authentication for the connecting device, resulting in a much higher level of assurance for remote connections. DirectAccess can also support integration with many existing multifactor authentication providers to provide strong authentication for the user, if desired.

DirectAccess is very firewall friendly and works anywhere the user has an active Internet connection. It requires no additional software to be installed, and the seamless and transparent nature of DirectAccess makes it much easier to use than VPN. All of this improves end user productivity and reduces associated management overhead for the solution.

DirectAccess is a more cost-effective alternative to VPN. DirectAccess can be deployed on existing infrastructure (physical or virtual) and does not require proprietary hardware. This makes it much easier and far less expensive to add additional capacity, if required. DirectAccess can also be managed using existing systems management tools and Windows administration skills and does not have any per-user licensing requirements, which results in additional cost savings over VPN.

DirectAccess Limitations and Drawbacks

DirectAccess is not a comprehensive remote access solution. It is designed for managed (domain-joined) Windows clients only. In addition, DirectAccess clients must be provisioned with the Enterprise edition SKU. Also, there are a few cases in which applications may not be compatible with DirectAccess. In addition, there is no support for DirectAccess on non-managed Windows machines, non-Enterprise SKUs, or any devices using non-Windows operating systems, so a VPN might still be required.

DirectAccess vs. VPN

DirectAccess or VPN?

You might be asking yourself, “DirectAccess or VPN?” Why not both? After all, DirectAccess and VPN aren’t mutually exclusive. They are, in fact, quite complimentary. DirectAccess can be used to provide secure remote access and enhanced management for Windows laptops managed by IT, while VPN can be deployed for non-managed devices. While you may not be able to entirely eliminate VPN with DirectAccess, it will certainly allow you to decrease the number of existing VPN licenses and reduce your investment in proprietary hardware, management tools, and dedicated administrators, all of which translates in to reduced capital investment and operational costs.

Summary

DirectAccess is not simply another VPN solution. While it does provide secure remote corporate network connectivity, it does so more securely and more cost effectively than traditional VPN does. DirectAccess is unrivaled in its security and ease of use, dramatically improving end user productivity and reducing associated infrastructure and support costs. DirectAccess can be deployed on current physical and virtual infrastructure, and can be managed using existing Windows systems management tools and skill sets.

DirectAccess Consulting ServicesIf you’d like to learn more about how DirectAccess can benefit your organization, or you would like some assistance with a DirectAccess proof of concept implementation, consider a DirectAccess consulting engagement today. I’m here to help plan, design, implement, and support DirectAccess and ensure the best chance of success for your deployment.

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