I’m excited to announce that I’ll be speaking at the Arizona Systems Management User Group (AZSMUG) at their next user group meeting on Friday, March 7, at 9:00 AM MST. I am presenting on the topic of Certificate Deployment Strategies with Microsoft Intune.
Intune and Certificates
My session at AZSMUG will provide an overview of issuing and managing certificates with Microsoft Intune. We’ll begin by examining common scenarios for certificate authentication and explore various delivery methods, including PKCS and SCEP. Additionally, we’ll discuss supporting technologies such as the Network Device Enrollment Service (NDES) and review deployment strategies and high availability options for the Intune Certificate Connector. The session will also cover Cloud PKI for Intune, integration with on-premises Active Directory, and best practices for securing certificate lifecycles and key management in enterprise environments.
Register Now
If you are in the Phoenix area and would like to attend the user group meeting on Friday, March 7, you will find the registration link here. Hope to see you there!
Always On VPN error 13801 is common when establishing an IKEv2 VPN connection. Typically, the issue is related to a configuration error or a problem with certificate deployment. However, administrators may encounter the 13801, an IKE authentication error, intermittently. Configuration errors are binary. If there is a misconfiguration, IKEv2 never works at all. However, a configuration error seems unlikely since the connection works occasionally yet fails at other times.
Client Authentication
The minimum application policy (Enhanced Key Usage, or EKU) requirement for the device authentication certificate for IKEv2 is Client Authentication (1.3.6.1.5.5.7.3.2). When intermittent 13801 errors occur, administrators may find multiple certificates in the local computer certificate store with the Client Authentication EKU issued by different certificate authorities. Commonly, Intune-managed Windows devices may include several certificates with Client Authentication.
Certificate Selection
When Windows attempts to establish an Always On VPN IKEv2 connection, and there are multiple certificates in the local computer certificate with Client Authentication defined, Windows must choose one certificate to use for the connection. If Windows chooses incorrectly, you will receive the 13801 IKE authentication failure error. If Windows selects the right one, the connection succeeds.
Resolution
There are several ways to resolve this issue. The best way is to update the Always On VPN device authentication certificate to include the IP security IKE intermediate application policy (EKU). When Windows encounters multiple client authentication certificates in the local computer certificate store, it will prefer any certificate with the IP security IKE intermediate application policy for IKEv2 VPN connections. Including the IP security IKE intermediate application policy on the Always On VPN device authentication certificate ensures proper certificate selection when multiple client authentication certificates are present.
Note: This change must be made to the Intune certificate enrollment template when using Intune with PKCS or SCEP.
Certificate Template
To update an existing Always On VPN device authentication certificate to include the IP security IKE intermediate application policy, open the certificate templates management console (certtmpl.msc) and perform the following steps.
Right-click the VPN device authentication certificate template and choose Properties.
Select the Extensions tab.
Click on Application Policies.
Click Edit.
Click Add.
Select the IP security IKE intermediate application policy.
Click Ok.
Click Ok.
Click Ok.
Once complete, any certificates issued after this change is applied will now include the IP security Ike intermediate application policy.
Force Renewal
Administrators may wish to update all certificates immediately rather than wait until they renew to receive the new setting. The course of action depends on how certificates are issued.
On-Premises
When issuing certificates using Active Directory Certificate Services (AD CS) on-premises, right-click the Always On VPN device authentication certificate template and choose Reenroll All Certificate Holders. This will force all domain-joined clients with Autoenroll permissions on the template to renew their certificate on their next enrollment cycle, regardless of the certificate’s lifetime.
Intune
Follow the steps below to force re-enrollment for all certificate holders when deploying certificates using Intune.
SCEP – Add the IP Security IKE Intermediate application policy to the Intune VPN policy. After this change is applied, Intune will reenroll all endpoints.
PKCS– A new Intune device configuration policy must be created that includes the IP security IKE intermediate application policy. Assign the new policy and remove the old one to replace all certificates.
PowerShell
It’s also possible to resolve this issue using PowerShell. Administrators can use the Set-VpnConnection PowerShell cmdlet to select a certificate based on the root certification authority (CA) or a specific custom application policy defined on the Always On VPN device authentication certificate. Be sure to add the -AllUserConnection switch when working with the device tunnel.
Root CA
Open a PowerShell command window and run the following command.
$RootCA = Get-Child-Item -Path Cert:\LocalMachine\My\<thumbprint of root CA certificate> Set-VpnConnection -Name <name of VPN profile> -MachineCertificateIssuerFilter $RootCA
Application Policy
Open a PowerShell command window and run the following command.
Set-VpnConnection -Name <name of VPN profile> -MachineCertificateEKUFilter <OID>
Note: When using a custom application policy Windows will return a warning message stating the EKU could not be validated. You can safely disregard this warning.
Intune Remediation
While running PowerShell commands locally might be helpful for troubleshooting and targeted evaluation testing, deploying settings via PowerShell at scale is challenging. For those organizations managing their devices using Microsoft Intune, I’ve published a few detection and remediation scripts on GitHub to perform these tasks.
The intermittent Always On VPN 13801 IKE authentication credentials are unacceptable error message is best resolved by updating the Always On VPN device authentication certificate to include the IP security IKE intermediate application policy (EKU). Although using PowerShell also works, it doesn’t scale effectively. SCCM or Intune remediations can help, but I’d encourage you to update the certificate template as best practice instead.
Are you ready? In just a few short weeks(!) Microsoft will release the February 2025 security updates. This is a critical update because Microsoft plans to enable full enforcement of strong certificate mapping on Active Directory Domain Controllers (DCs) with this release. Administrators unprepared for this may incur outages for workloads using certificate-based authentication such as Always On VPN, Wi-Fi, and others.
Microsoft introduced strong certificate mapping with the May 2022 update KB5014754 to address vulnerabilities identified with certificate-based authentication. The update makes changes to Active Directory Certificate Services (AD CS) certification authorities (CAs) to embed the principal’s Security Identifier (SID) on issued certificates with a new certificate extension. The update also changes domain controller behavior to monitor and optionally enforce strong certificate mapping for authentication.
Enforcement Mode
When first introduced, the update is configured in compatibility mode. If a certificate that isn’t strongly mapped is presented for authentication, an event is recorded in the event log indicating that. Microsoft has been planning for years to enable full enforcement. After many delays, that time is now upon us. Specifically, full enforcement for strong certificate mapping will be enabled by default on DCs after applying the February 2025 security updates.
Note: Administrators can switch back to compatibility mode for now. See below for more details.
Limitations
Initially, the strong certificate mapping update was applied only to online certificate templates. Specifically, those templates are configured to build the subject name from Active Directory information. However, offline templates, where the subject name is supplied in the request, do not include this information by default. Crucially, any certificate issued with Microsoft Intune with PKCS or SCEP uses offline templates and is not strongly mapped. The lack of strong certificate mapping options for Intune-issued certificates forced Microsoft to delay its full enforcement deadline until these limitations were resolved.
Updates
In October 2024, Microsoft Intune announced support for strong certificate mapping for PKCS and SCEP certificates. Administrators can now configure these certificates to include strong certificate mapping. However, administrators must take action to affect this change.
PKCS
To enable strong certificate mapping for PKCS certificates, administrators must ensure that the certificate connector is running at least version 6.2406.0.1001. In addition, the following registry key must be configured on the connector server.
The Intune Certificate Connector server must be restarted for this change to take effect. No changes are required on the PKCS certificate policy in Intune.
SCEP
To enable strong certificate mapping for SCEP certificates, administrators must add the following attribute/value pair to the Subject alternative name settings on their existing Intune SCEP certificate policy.
Attribute: URI Value: {{OnPremisesSecurityIdentifier}}
Preparation
Administrators using certificate-based authentication against on-premises Active Directory should ensure all user and device authentication certificates include embedded SID information. For certificates issued on-premises, with Intune using PKCS or certificates issued by Entra Conditional Access, the certificate should now have the extension 1.3.6.1.4.1.311.25.2, including the principal’s SID.
SCEP certificates issued using Intune will include the following information in the Subject Alternative Name field.
URL=tag:microsoft.com,2022-09-24:sid:<sid>
Note: This applies to certificates issued using Cloud PKI for Microsoft Intune as those certificates are deployed using a SCEP device configuration policy.
Opt-Out
With the February 2025 security update, all domain controllers will be switched to full enforcement mode. Authentication requests using certificates without strong mapping will be denied in this configuration.
If your organization is not prepared to move to full enforcement mode, the February 2025 update allows administrators to opt out and switch back to compatibility mode by enabling the following registry key on all domain controllers.
Administrators are strongly encouraged to update all user and device authentication certificates before September 2025. With the September 2025 security update, Microsoft will no longer honor the opt-out registry settings and strictly enforce strong certificate mapping for all certificate-based authentication requests.
Troubleshooting
Certificate authentication is commonly used for Always On VPN and Wi-Fi authentication. If full enforcement mode is enabled on domain controllers and a certificate is presented for authentication that is not strongly mapped, administrators may see the following event log information recorded on the Network Policy Server (NPS).
Network Policy Server denied access to a user.
The details of the event include the following.
Reason Code: 16 Reason: Authentication failed due to a user credentials mismatch. Either the user name provided does not map to an existing user account or the password was incorrect.
Obviously, the user does not enter their password when using certificates for authentication. However, the indication of a credential mismatch can be caused by missing strong certificate mapping information when the DC is in full enforcement mode.
Note: There are other causes for reason code 16 failures on NPS. Further investigation may be required to determine the root cause.
Microsoft has released the October 2024 security updates, and numerous issues may impact Always On VPN administrators. Although many CVEs affect Always On VPN-related services that are Remote Code Execution (RCE) vulnerabilities, none are critical this cycle.
RRAS Updates
This month, Microsoft has provided 12 updates for the Windows Server Routing and Remote Access Service (RRAS), commonly deployed to support Always On VPN deployments. Most of these CVEs involve overflow vulnerabilities (heap and stack), input validation weaknesses, and buffer over-read and overflow vulnerabilities. All are rated important, and there are no known exploits currently.
In addition to the updates above, Microsoft also released fixes for security vulnerabilities in various related services that are important to Always On VPN administrators.
Windows Network Address Translation (NAT)
The following CVEs address denial of service vulnerabilities in the Network Address Translation (NAT) service.
CVE-2024-43541 – Simple Certificate Enrollment Protocol (SCEP) Denial of Service Vulnerability
CVE-2024-43544 – Simple Certificate Enrollment Protocol (SCEP) Denial of Service Vulnerability
Recommendations
Always On VPN administrators are encouraged to update systems as soon as possible. However, since none of the CVEs is rated Critical, updates can be applied during standard update windows.
Microsoft recently announced the general availability of its new PKI-as-a-Service platform called Microsoft Intune Cloud PKI. With Intune Cloud PKI, administrators create certification authorities (CAs) to issue and manage user and device authentication certificates for Intune-managed endpoints. Cloud PKI also provides hosted Authority Information Access (AIA) and Certificate Revocation List (CRL) Distribution Point (CDP) services, in addition to Simple Certificate Enrollment Protocol (SCEP) service, so administrators do not have to deploy on-premises infrastructure to take advantage of certificate-based authentication.
Certificate Templates
After deploying your Intune Cloud PKI root and issuing CAs, you may wonder where to find the associated certificate templates. If you are familiar with traditional on-premises Active Directory Certificate Services (AD CS) implementations, this is how you define the purpose, key policy, security parameters, and lifetime of the certificate issued using that template. However, Intune Cloud PKI does not use certificate templates in the traditional way many administrators are familiar with.
Note: Microsoft may introduce support for certificate templates for Intune Cloud PKI in the future. However, it is not supported at the time of this writing.
SCEP Profile
Administrators define certificate policies and security parameters using Intune’s SCEP device configuration profile instead of certificate templates. In essence, the SCEP profile functions as the certificate template. With the Intune device configuration profile, administrators can define the following settings.
Certificate Type
The certificate type can be either a user or a device. Intune Cloud PKI can issue certificates for either or both, as required.
Subject Name (User)
The subject name is unimportant for user authentication certificates because the User Principal Name (UPN) defined in the Subject Alternative Name field is used to authenticate the user. In this field, the administrator can use whatever they like. However, it’s common to use the username here. Avoid using the email attribute here because there’s no guarantee that every user will have this defined on the Active Directory (AD) user object.
Subject Name (Device)
Administrators should supply the device’s fully qualified domain name (FQDN) for device authentication certificates in the subject name field. For hybrid Entra joined devices, administrators can use the {{FullyQualifiedDomainName}} variable. For native Entra-joined devices, you can use {{DeviceName}} and append your DNS suffix, for example, {{DeviceName}}.corp.example.net.
Note: Intune supports numerous variables to populate fields for certificates. You can find a list of supported variables in the following locations.
The Subject Alternative Name (SAN) field for user authentication certificates should be populated with the User Principal Name (UPN) value. Ensure this value is appropriately configured internally and supports sign-in to AD.
Subject Alternative Name (Device)
The SAN field for device authentication certificates should be populated with the device’s FQDN. Follow the guidance for device subject names covered previously.
Certificate Validity Period
This field allows the administrator to define the certificate’s validity period. The best practice is to limit the lifetime to no more than one year. A shorter lifetime is recommended for certificates not backed by a Trusted Platform Module (TPM).
Key Storage Provider
This value is critical to ensuring integrity for issued user and device authentication certificates. The best practice is to select Enroll to Trusted Platform Module (TPM) KSP, otherwise fail. However, if you must issue certificates to endpoints without a TPM (e.g., legacy devices, virtual machines, etc.), consider a separate profile with a shorter certificate lifetime to limit exposure.
Key Usage
Digital signature and Key encipherment are required for user and device authentication certificates.
Key Size
The 2048-bit key size is the minimum recommended value for certificates with RSA keys. Using 4096-bit is not recommended for end-entity certificates and can potentially cause conflicts in some cases. Intune Cloud PKI does not support the 1024-bit key size.
Hash Algorithm
SHA-2 is the best practice for the hash algorithm. SHA-1 has been deprecated and should not be used.
Root Certificate
Select the Cloud PKI root CA certificate.
Extended Key Usage
The minimum requirement for user and device authentication certificates is Client Authentication (1.3.6.1.5.5.7.3.2).
Renewal Threshold
This value specifies at what point the certificate can be renewed. 20% is commonly used for certificates with a one-year lifetime.
SCEP Server URLs
This value can be found on the configuration properties page of your Cloud PKI issuing CA. The URI will include a variable in the URL. The variable is there by design. Copy and paste this URL exactly as displayed in the SCEP URL field.
Training
Are you interested in learning more about issuing and managing certificates with Microsoft Intune? Would you like to know how to securely and optimally implement PKCS and SCEP infrastructure on-premises? Do you want more details about deploying and managing Microsoft Intune Cloud PKI? Register now for my upcoming three-day live Certificates and Intune Masterclass training event at the ViaMonstra online training academy. We’ll deep-dive into all aspects of certificate management using Intune with on-premises AD CS and Intune Cloud PKI. I’ll be sharing many advanced techniques for adequately securing your certificate infrastructure. Space is limited, so register now!
Recently, Microsoft introduced a new PKI-as-a-Service offering called Cloud PKI. This cloud-based PKI can issue and manage certificates to Intune-managed endpoints. Administrators can now deploy user and device authentication certificates using Intune Cloud PKI without deploying Active Directory Certificate Services (AD CS) on-premises. Numerous blog posts and YouTube videos show how to configure and deploy Intune Cloud PKI, so I won’t reinvent the wheel with a complete configuration guide here. This article will focus instead on integrating Microsoft Intune Cloud PKI with on-premises Active Directory (AD).
Note: Administrators must deploy certificates to all enterprise domain controllers and RADIUS servers to support certificate-based authentication with AD. However, Cloud PKI for Intune can only issue certificates to Intune-managed endpoints today. It cannot issue certificates to servers. Administrators must use another CA (AD CS or another Cloud PKI solution) to issue and manage domain controller and RADIUS server certificates on-premises to support this scenario.
AD Integration
While Intune Cloud PKI eliminates the need for on-premises AD CS infrastructure, there will be times when Cloud PKI-issued certificates will be used to authenticate to on-premises AD, either through a RADIUS server such as Windows Network Policy Server (NPS), which is common for VPN and Wi-Fi deployments, or other methods. Additional configuration is required to support this scenario.
Publish Root/Issuing CA Certificates
The Intune Cloud PKI root and issuing CA certificates must be published in AD to support on-premises AD authentication using Intune Cloud PKI-issued certificates. Follow the steps below to complete this task.
Note: Arguably, you could skip publishing the Intune Cloud PKI root and issuing CA certificates in on-premises AD because Cloud-PKI certificates can only be issued to Intune-managed endpoints, in which case you are likely already deploying the Cloud PKI root and issuing CA certificates using Intune. I’m including these steps for completeness. However, publishing the Intune Cloud PKI issuing CA certificate in the NtAuthCA certificate store in AD is required to support on-premises AD authentication using Intune Cloud PKI-issued certificates, so that step is mandatory.
RootCA Store
On a domain-joined computer on-premises, open an elevated PowerShell or command window and run the following command to publish the Intune Cloud PKI root CA certificate to the RootCA certificate store in AD.
certutil.exe -dspublish -f <path to Cloud PKI root CA certificate> RootCA
SubCA Store
Next, run the following command to publish the Cloud PKI issuing CA certificate to the SubCA certificate store in AD.
certutil.exe -dspublish -f <path to Cloud PKI issuing CA certificate> SubCA
NtAuthCA Store
Finally, run the following command to publish the Intune Cloud PKI issuing CA certificate to the NtAuthCA certificate store in AD. Publishing the Intune Cloud PKI issuing CA certificate in the NtAuthCA store in AD allows certificates issued by Intune Cloud PKI to be used to authenticate on-premises AD if required. Be sure to run this command even if you did not run the previous commands to publish the Intune Cloud PKI root and issuing CA certificates in AD.
certutil.exe -dspublish -f <path to Cloud PKI issuing CA certificate> NtAuthCa
GUI
If you have an existing on-premises AD CS deployment, you can use the Enterprise PKI management console to publish the Intune Cloud PKI certificates in AD as an alternative to the command line. First, open the Enterprise PKI tool (pkiview.msc) on an existing on-premises Certification Authority (CA) server. Right-click the Enterprise PKI root node and choose Manage AD Containers. Add the Intune Cloud PKI root CA certificate to the Certification Authorities container. Next, add the Intune Cloud PKI issuing CA certificate to the Enrollment Services container. Finally, add the Intune Cloud PKI issuing CA certificate to the NTAuthCertificatesContainer.
Summary
Administrators can use the Microsoft Intune Cloud PKI solution to issue and manage user and device authentication certificates for their Intune-managed endpoints. Using the commands above, administrators can also integrate their Intune Cloud PKI with on-premises Active Directory to support user and device authentication for common workloads such as Wi-Fi and VPN. Critically, when integrating Cloud PKI with on-premises Active Directory, your Intune administrators should be considered Tier-0 administrators, and appropriate security controls should be enforced.
I want to remind you of a critical upcoming milestone that may affect your business. In just 60 days, we will reach the end of support for Windows Server 2012 and Windows Server 2012 R2. As of October 10, 2023, these operating systems will no longer receive security updates or technical support from Microsoft.
End of Support
End of support means your servers will be more vulnerable to security risks and potential threats. It is essential to take action now to ensure your IT infrastructure’s continued security and stability. Upgrading to newer, supported operating systems will protect your data and systems from potential cyber threats and provide access to enhanced features and performance improvements.
Don’t Wait
Now is the time to migrate those remaining workloads for those still running Windows Server 2012 and 2012 R2! Consider the following commonly deployed services that may still be running on Windows Server 2012 or 2012 R2 in your organization.
Remote Access – Windows Server Routing and Remote Access Service (RRAS) is commonly deployed to provide secure remote access for field-based workers. In addition, Absolute Secure Access (formerly NetMotion Mobility) is a widely implemented premium alternative to RRAS. Organizations may be hesitant to migrate these workloads because disrupting remote workers is painful.
DirectAccess – This remote access technology is widely deployed and extremely difficult to migrate. In addition, the complex nature of DirectAccess, with its many intricate interdependencies, poses a significant challenge to organizations migrating this role.
PKI – This is likely the most common enterprise service to be found running on Windows Server 2012 and 2012R2. Most organizations relying on Windows Active Directory Certificate Services (AD CS) to issue and manage enterprise certificates are reluctant to move this workload once it is deployed. This service is much easier to migrate than you might think! It can be done without disruption as well.
Consulting Services
We understand that upgrading might require careful planning and coordination, and our team is here to support you throughout the transition process. Don’t delay – take this opportunity to safeguard your organization’s data and systems by upgrading to the latest Windows Server version or exploring cloud-based solutions.
Get In Touch
Please don’t hesitate to contact us for further assistance or any questions regarding the upgrade process. Together, let’s ensure your business remains secure and productive. You can get started today by booking a free one-hour consultation to discuss your migration strategy. Just fill out the form below and I’ll provide more information.
I recently wrote about changes to certificate-based authentication affecting Always On VPN implementations. These changes were introduced by Microsoft’s security update KB5014754. When the update is installed on domain controllers and enterprise Certification Authorities (CAs), administrators can perform strong user mapping for certificates used for Active Directory authentication. However, when first introduced, the update came with some serious limitations that prevented administrators from enabling full enforcement mode for certificate mapping.
Limitations
When KB5014754 is installed on an enterprise issuing CA, a new certificate extension (1.3.6.1.4.1.311.25.2) is added to the issued certificate that includes the principal’s (user or device) Security Identifier (SID). However, this only occurs when an online template is used. An online template is one with the subject name built from Active Directory information. The SID is not embedded in certificates issued using an offline template. Offline templates are templates where the subject name is supplied in the request. There are two scenarios where this causes problems for Always On VPN.
Microsoft Intune
Certificates delivered with Microsoft Intune via the Intune Certificate Connector use an offline template. This applies to certificates using PKCS or SCEP. Today, the SID is not embedded by issuing CAs using offline templates.
Azure Conditional Access
The short-lived certificate issued by Azure when Conditional Access is configured for Always On VPN did not include the SID. However, that recently changed.
Recent Updates
Today we can scratch Azure Conditional Access off the list of limitations for Always On VPN. Microsoft recently introduced support for the new SID extension in Azure Conditional Access certificates, as shown here.
Now when an Azure Conditional Access certificate is issued to an on-premises user or device account that is synced with Azure Active Directory, Azure Conditional Access will include the SID information in the issued short-lived certificate.
Intune
Unfortunately, we’re still waiting for Microsoft to address the limitation with certificates delivered using Microsoft Intune. Hopefully we’ll see an update for that later this year.
I’m excited to announce that I’ll be presenting at this year’s TechMentor IT training conference! The event takes place July 17-21, 2023, at the Microsoft headquarters in Redmond, Washington.
My Sessions
I will be delivering two talks at this year’s event.
In this talk, I’ll describe in detail how to deliver on-premises enterprise PKI certificates using Intune. We’ll cover all aspects of certificate delivery, including the Intune Certificate Connector configuration, device configuration profile options, advantages of PKCS over SCEP, and certificate template security best practices.
During this session, I’ll share many tips, tricks, and best practices for deploying and managing Always On VPN client configuration settings using Intune. I’ll explain the limitations of the Intune VPN profile template and how to work around them using custom XML. I will also describe how to use Intune Proactive Remediation to optimize Always On VPN client configuration settings post deployment.
Discount Code
Use the discount code Hicks and receive $400.00 off the standard pricing for the event. Don’t miss out on this opportunity to learn from some of the best IT pros in the business. Register today!
Let’s Connect!
If you’re attending TechMentor 2023 this year, let’s connect! I’ll be at the conference all week. Attend one of my sessions, join me on Thursday for a Table Topic lunch, or let’s grab a beer somewhere. Reach out to me and arrange some time!
Deploying user or device authentication certificates to support Always On VPN requires installing the Certificate Connector for Microsoft Intune. The same connector can link Intune to on-premises public key infrastructure (PKI) using PKCS or SCEP certificates. The connector can be configured to run in the SYSTEM context or a domain service account.
Configuration Failure
Administrators may encounter the following error message when installing the certificate connector and selecting the option to use a domain service account.
“Configuration failed. Configuring Microsoft Intune Certificate Connector failed. No changes were made to Feature or Proxy settings. Please try again.”
Root Cause
This error occurs because the service account does not have the correct permissions assigned on the server where the connector is being installed. Specifically, the service account must have the Logon as a service right assigned. To do this, open the local group policy editor (gpedit.msc) and perform the following steps.
Expand Computer Configuration > Windows Settings > Security Settings > Local Policies > User Rights Assignment.
Double-click Log on as a service.
Click Add User or Group.
Add the service account.
Click OK.
Once complete, remove the Certificate Connector for Intune and re-run the installation again.
