All posts tagged certificate

Azure Conditional Access Certificates with SID Information Now Available

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.

Additional Information

Certificate-Based Authentication Changes and Always On VPN

Microsoft KB5014754

Digital Certificates and TPM

Microsoft Intune Certificate Connector Service Account and PKCS

2 Comments

by Richard M. Hicks on July 11, 2023 • Permalink

Posted in AADJ, Active Directory, administration, Always On VPN, AOVPN, authentication, Azure, Azure Active Directory, Azure AD, Azure AD Join, Azure Conditional Access, Azure MFA, Azure VPN, Certificate Connector for Intune, certificates, cloud, Conditional Access, Deployment, Device Management, Endpoint Manager, Enterprise, enterprise mobility, HAADJ, Hybrid Azure AD Join, Infrastructure, InTune, Intune Certificate Connector, Intune PFX Connector, MDM, MEM, MEMCM, MFA, Microsoft, Microsoft Endpoint Manager, Microsoft Intune, Mobile Device Management, Mobility, Multifactor Authentiction, NDES, Network Device Enrollment Service, Network Device Enrollment Services, NPS, Operational Support, PFX Connector, PKCS, PKI, public cloud, public key infrastructure, Remote Access, SCEP, Security, Simple Certificate Enrollment Protocol, systems management, Update, user tunnel, VPN, Windows 10, Windows 11

Posted by Richard M. Hicks on July 11, 2023

https://directaccess.richardhicks.com/2023/07/11/azure-conditional-access-certificates-with-sid-information-now-available/

Always On VPN and the PSPKI PowerShell Module

Certificates are a crucial part of a secure Always On VPN implementation. Certificates are phishing-resistant forms of authentication that, when configured correctly, provide robust and multifactor authentication for remote access users and devices.

AD CS

Most commonly, certificates are issued by an on-premises Microsoft Active Directory Certificate Services (AD CS) server. Administrators configure and deploy a Certification Authority infrastructure to issue and manage user and device authentication certificates in their organization. CA certificates are also required on the VPN server to support Always On VPN device tunnel connections and IKEv2 user tunnel connections. The NPS server also requires an enterprise CA certificate. Of course, the CA can issue certificates for other purposes, including Wi-Fi authentication, document signing, and code signing, just to name a few.

PSPKI

PSPKI is a PowerShell module available in the PowerShell Gallery for configuring, managing, and troubleshooting Microsoft AD CS. Created by Vadims Podans of PKI Solutions, PSPKI includes over 100 functions for various AD CS and certificate-related tasks. Always On VPN administrators will find this PowerShell module helpful when configuring and troubleshooting certificate-related issues for their Always On VPN deployments.

Note: The AD CS remote server administration tools (RSAT) must be installed to access all of the PSPKI module’s functionality.

Installation

Run the following PowerShell command to install the PSPKI PowerShell module.

Install-Module -Name PSPKI

Always On VPN and PSPKI

Always On VPN Administrators will immediately find a few PSPKI functions helpful when implementing and supporting Always On VPN.

Test-WebServerSSL – This function will connect to a remote web server and display details about the TLS certificate included in the response. This can be especially helpful when troubleshooting SSTP VPN connections.

Convert-PfxToPem – This is a handy utility for converting a PFX file to the PEM format. This is commonly required when importing CA certificates on non-Microsoft platforms, security devices, and load balancers.

Convert-PemToPfx – Occasionally, administrators must convert a certificate and private key in PEM format to PFX to install on a Windows server. This tool allows administrators to perform this task easily.

Get-CertificationAuthority – This function quickly enumerates all enterprise CA servers and displays information about their hostname, accessibility, service status, and type.

Ping-ICertInterface – This function helps troubleshoot CA connectivity issues. Administrators can quickly determine if a CA is reachable and capable of issuing a certificate using this command.

Get-CaTemplate – This command displays a list of certificate templates published on the specified target CA server. The certificate template’s display name and the minimum support CA version are provided. In addition, the output indicates if certificate autoenrollment is enabled on the template.

Much More

The PSPKI PowerShell module for AD CS has many tools for configuring and managing AD CS. PSPKI recently received a major update to version 4.0. Download and install PSPKI today. It will make your life easier, I can assure you!

Additional Information

PSPKI PowerShell Module – PowerShell Gallery

PSPKI PowerShell Module – GitHub

AOVPNTools PowerShell Module – PowerShell Gallery

AOVPNTools PowerShell Module – GitHub

InboxAccountingDatabaseManagement PowerShell Module

InboxAccontingDatabaseManagement – PowerShell Gallery

InboxAccountingDatabaseManagement – GitHub

4 Comments

by Richard M. Hicks on June 20, 2023 • Permalink

Tagged AD CS, administration, Always On VPN, AOVPN, CA, certificate, certificates, Certification Authority, gallery, GitHub, MFA, Microsoft, module, multifactor authentication, pem, pfx, PKI, PowerShell, PowerShell gallery, pspki, RSAT, SSL, template, TLS, troubleshooting, VPN

Posted by Richard M. Hicks on June 20, 2023

https://directaccess.richardhicks.com/2023/06/20/always-on-vpn-and-the-pspki-powershell-module/

Intune Certificate Connector Service Account and PKCS

Microsoft Always On VPN administrators have two choices when deploying enterprise PKI certificates using Intune; PKCS and SCEP. I prefer using PKCS because it is easier to configure and manage. Also, PKCS requires no inbound connectivity, simplifying the deployment and reducing the organization’s public attack surface. Provisioning certificates using Intune is inherently risky. However, there are some steps administrators can take to mitigate much of this risk.

PKCS Security

The service account is the most critical aspect of configuring the Intune Certificate Connector for PKCS securely. The service account has permission to enroll for an exceedingly dangerous published certificate template. Specifically, the PKCS certificate template has the deadly combination of supplying the subject information in the request, and the Client Authentication enhanced key usage (EKU). Further, the scenario does not allow administrative approval to be enabled on the certificate template. If an attacker were to gain access to this certificate template, they could enroll as any principal they chose, including a domain administrator, and their request would be processed automatically. Subsequently, they could authenticate to Active Directory using only the certificate without knowing the account’s password.

Service Account

Using a Group Managed Service Account (GMSA) would be ideal in this scenario. However, the Intune Certificate Connector does not support using GMSA when using PKCS. With that, administrators must use a regular domain service account instead, which introduces additional risk. To enhance the overall security of the solution, consider performing the following PKCS service account hardening tasks when using the Intune Certificate Connector to issue PKCS certificates with Intune.

Standard User

The service account should be a standard domain user with no special privileges. The service should be dedicated to PKCS and not shared with other services in the enterprise. Create the account from scratch (do not duplicate another account!), and use a long, complex password. Document this password securely. In addition, ensure the PKCS service account is not a member of any other security groups. It does not require local administrator access, either.

Account Hardening

After creating the service account, click the Log On To button on the Account tab and ensure the account can only log on to the server(s) where you have installed the Intune Certificate Connector.

Next, check the box next to Account is sensitive and cannot be delegated in the Account options section.

In addition, select the option Deny access in the Network Access Permission section of the Dial-In properties page.

Finally, uncheck Enable remote control on the Remote control properties page.

Local Access Rights

Open the Local Group Policy Editor (gpedit.msc) on each server where you installed the Intune Certificate Connector. Navigate to Computer Configuration > Windows Settings > Security Settings > Local Policies > User Rights Assignment. Enable the following policy settings for the PKCS service account.

Deny access to this computer from the network
Deny log on as a batch job
Deny log on locally
Deny log on through Remote Desktop Services

Optionally these settings can be enforced on the Intune Certificate Connector server using Active Directory group policy.

Disclaimer

I am not an Active Directory security expert! The guidance provided here is based on my many years of Windows administrative experience, conversations with Identity and Access security professionals, and published guidance found on the Internet. If you have suggestions to further improve service account security, don’t hesitate to let me know! Please share in the comments, below.

Additional Information

Overview of the Certificate Connector for Microsoft Intune

Configure and use PKCS Certificates with Microsoft Intune

Microsoft Intune Certificate Connector Service Account Requirements

9 Tips for Preventing Active Directory Servie Accounts Misuse

How to Manage and Secure Service Accounts

4 Comments

by Richard M. Hicks on January 30, 2023 • Permalink

Posted by Richard M. Hicks on January 30, 2023

https://directaccess.richardhicks.com/2023/01/30/intune-certificate-connector-service-account-and-pkcs/

Richard M. Hicks Consulting, Inc.

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All posts tagged certificate

Azure Conditional Access Certificates with SID Information Now Available