Microsoft has published an in-depth guide detailing how to implement certificate-based authentication for Windows Admin Center (WAC) gateway servers by leveraging Active Directory Certificate Services (AD CS).
This enhancement enables organizations to enforce smart card or virtual smart card logon for administrators, ensuring that access to WAC is granted only when a valid client certificate is presented.
By integrating Authentication Mechanism Assurance (AMA) and AD security groups, the solution adds a strong second factor to Windows Integrated Authentication, significantly reducing the risk of credential-based attacks.
Leveraging AD CS and AMA for Smart Card Logons
The core of the solution is the use of AD CS to issue smart card logon certificates to administrators.
Organizations first deploy an enterprise certification authority within their Active Directory domain and configure a certificate template, either the built-in Smartcard Logon template or a custom “IT Admin Smartcard Logon” template.
This template is duplicated and tailored with stringent cryptographic settings, UPN-based subject names, and the Smart Card Logon extended key usage.
Administrators enroll for these certificates via physical smart cards or TPM-backed virtual smart cards, which are then trusted by domain controllers through the NTAuthCertificates store.
Once certificates are issued, the template’s unique OID is mapped to a dedicated universal security group (e.g., “WAC-CertAuth-Required”) using the msDS-OIDToGroupLink attribute in the Configuration partition’s Public Key Services container.
AMA dynamically adds this group to a user’s Kerberos token when they authenticate with a smart card certificate, while omission of the certificate leaves the group out of the token.
With AMA in place, WAC gateway settings are modified to require membership in both an allowed administrative group and the AMA-linked smartcard group.
Administrators navigate to the WAC Access panel, enable Active Directory authentication, and designate their IT Admins group as Gateway users.
They then specify the “WAC-CertAuth-Required” group as the Smartcard-required group.
This dual membership check ensures that WAC only authorizes sessions where the user logged on interactively with a valid smart card certificate.
The guide also describes the PowerShell cmdlets Get-SMEAuthorization and Set-SMEAuthorization for scripting these configurations, enabling automation in large-scale environments.
Testing, Validation, and Troubleshooting
Microsoft’s guide emphasizes comprehensive testing: attempts to access WAC after password-only logons should fail with HTTP 401 or repeated credential prompts, while smart card logons yield seamless access.
Administrators can verify group membership using whoami /groups and review WAC’s event logs under Microsoft-ServerManagementExperience.
Common troubleshooting scenarios are covered, including missing group assignments due to incorrect OID mappings, certificate revocation and CRL issues, and browser configuration for Integrated Windows Authentication.
The guide also advises on domain controller certificate requirements for Kerberos PKINIT and Group Policy settings to enforce smart card logon and workstation lock on card removal.
By following this guide, organizations can strengthen their Windows Admin Center deployments with a robust certificate-based second factor, aligning with zero trust principles and mitigating risks associated with password-only authentication.
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