Implement certificate-based authentication in Azure AD

Certificate-based authentication (CBA) in Azure Active Directory (Azure AD) is a solution that augments the security of your applications by providing an additional layer for a user to confirm their identity. This form of authentication relies on digital certificates, and it comes in handy in the fight against issues like phishing and brute force attacks. For individuals preparing for the SC-300 Microsoft Identity and Access Administrator exam, understanding how to implement certificate-based authentication in Azure AD is vital.

Requirements for Certificate-based Authentication

Before implementing CBA, ensure you meet the following prerequisites:

• Azure AD with at least one verified domain. A ‘verified domain’ here means that Azure has confirmed you are the owner.
• Azure AD Connect version 1.1.819.0 (or later) to synchronize on-premises attributes.
• Each user that needs CBA must have a userPrincipalName (UPN) that matches the subject or subject alternative name (SAN) on their certificate.
• Public key infrastructure (PKI) to issue certificates to users.
• Each user’s Azure AD object must contain the certificate’s public key.
• Public trusted certificates for each user.

Steps for Implementation

1. Configuration of Azure AD

Azure AD Connect integrates your on-premises directories with Azure AD. You must have at least version 1.1.819.0 or later to integrate CBA. To validate the version:

Import-Module "C:\Program Files\Microsoft Azure Active Directory Connect\AzureADSSO.psd1"
Get-ADSyncGlobalSettingsParameter

Ensure that ‘IsDeviceWritebackEnabled’ value is True.

2. Enable certificate-based authentication

To enable CBA, use the Azure portal:

1. Sign in to the Azure portal as an Azure AD global administrator.
2. Browse to Azure Active Directory > Security > Authentication methods > Certificate-based Authentication.
3. Click ‘Yes’ to enable CBA and save your setting.

3. Adding the certificates to Azure AD

To add a certificate to a user’s object, you need to format it as a base64 string and add it to the user’s ‘userCertificate’ attribute.

Here is a PowerShell script to achieve that:

$certFilePath = "C:\certificates\usercert.cer"
$cert = New-Object System.Security.Cryptography.X509Certificates.X509Certificate
$cert.Import($certFilePath)
$binCert = $cert.GetRawCertData()
$credValue = [System.Convert]::ToBase64String($binCert)
Set-AzureADUserExtension -ObjectId "" -ExtensionName "userCertificate" -ExtensionValue "$credValue"


Always confirm and carefully manage the certificates issued to users to avoid potential risks.

4. Validation of the configuration

Testing is key after applying these changes to ensure your configuration works as expected. Use a device that trusts your root certificate to test the configuration. You must have Azure AD Connect running with password hash synchronization for password authentication fall back in case CBA fails.

In summary, implementing certificate-based authentication in Azure AD enhances the security of your systems by adding an extra layer of identity verification. It helps to tackle various potential threats and is thus an essential topic in the SC-300 Microsoft Identity and Access Administrator exam. You must ensure to understand the requirements for implementing CBA and confirm a successful implementation by testing your configuration appropriately.

Remember, in this digital world, securing your systems is essential. Certificate-based authentication, when implemented correctly in Azure AD, will go a long way in ensuring the safety of your system.

So, delve deeper into this topic, and good luck with your SC-300 Microsoft Identity and Access Administrator exam! Stay safe!

Practice Test

True or False: Certificate-based authentication enables you to be authenticated by Azure Active Directory with a client certificate on a Windows, Android or iOS device when connecting to resources.

• True
• False

Answer: True

Explanation: When utilized, certificate-based authentication allows you to use a client certificate to authenticate. This method is often used as an alternative to entering a password.

Which of the following protocols support certificate-based authentication in Azure AD?

• A. OAuth 0
• B. OpenID connect
• C. SSL/TLS
• D. SAML

Answer: A, B, D

Explanation: The OAuth 0, OpenID connect and SAML protocols all support certificate-based authentication in Azure AD.

True or False: You can only use self-signed certificates for client certificate-based authentication in Azure AD.

• True
• False

Answer: False

Explanation: Azure AD allows for the use of both self-signed certificates and those from a trusted certificate authority for client certificate-based authentication.

To implement certificate-based authentication in Azure AD, which of the following are required?

• A. A client certificate
• B. An Azure AD premium account
• C. A client with a device that supports TLS
• D. All of the above

Answer: D. All of the above

Explanation: All of the mentioned elements are necessary for setting up certificate-based authentication in Azure AD.

True or False: It is not possible to use certificate-based authentication for web applications and services running on Azure.

• True
• False

Answer: False

Explanation: Azure Active Directory does allow for certificate-based authentication for web applications and services. Such a setup improves security with a secondary proof of user identity.

True or False: Certificate-based authentication in Azure AD does not support Microsoft’s Intune device enrollment for mobile devices.

• True
• False

Answer: False

Explanation: Certificate-based authentication in Azure AD does support Intune device enrollment for both Android and iOS devices.

Which of these devices can you utilize certificate-based authentication with Azure AD?

• A. Windows
• B. Android
• C. iOS
• D. All of the above

Answer: D. All of the above

Explanation: Azure Active Directory certificate-based authentication supports all of these devices.

True or False: Certificate lifecycle management features are provided by Azure AD for client certificate-based authentication.

• True
• False

Answer: False

Explanation: Azure AD does not manage the client certificate lifecycles. However, it is the responsibility of the certificate’s issuer to manage its lifecycle.

True or False: Even after enabling certificate-based authentication in Azure AD, users can still use password authentication if they wish to.

• True
• False

Answer: True

Explanation: Enabling certificate-based authentication does not stop users from choosing to authenticate with a username and password if they prefer.

Is it necessary to install a user certificate in Azure Key Vault to enable certificate-based authentication?

• A. Yes
• B. No

Answer: B. No

Explanation: It is not necessary to store user certificates in Azure Key Vault to enable certificate-based authentication in Azure AD.

Interview Questions

What is certificate-based authentication in Azure AD?

Certificate-based authentication is a process that allows users to authenticate to applications, Microsoft 365, SaaS, and other third-party applications using client certificates. It’s a feature of Azure Active Directory that increases security.

Can a client certificate be used for Azure AD authentication?

Yes, Azure AD supports client certificate-based authentication for apps that are configured to use it.

What type of certificates does Azure AD support for certificate-based authentication?

Azure AD supports either Self-Signed and Enterprise CA issued certificates for certificate-based authentication.

Which type of account can use certificate-based authentication?

Both user accounts and service principals can use certificate-based authentication in Azure AD.

Can Certificate-Based Authentication (CBA) be used with Microsoft 365 Apps?

Yes, you can use Certificate-based authentication with Microsoft 365 apps in your organization.

How does Azure AD verify the certificates for authentication?

Azure AD verifies certificates based on the certificate’s issuer and thumbprint.

Is it necessary to register the public key of the client certificate with Azure AD?

Yes, the public key of the client certificate must be registered with Azure AD to allow it to authenticate the client.

What is the role of Azure AD Connect in implementing certificate-based authentication?

Azure AD Connect can be used to configure federation with Active Directory Federation Services (AD FS), enabling certificate-based authentication.

Is Azure AD’s certificate-based authentication limited to any specific platforms?

No, Azure AD’s certificate-based authentication is not limited to any specific platforms. It supports Windows, MacOS, iOS, Android, and other platforms.

How do I revoke a certificate in Azure AD?

To revoke a certificate in Azure AD, you must revoke it from the issuing Certificate Authority (CA). Azure AD will stop trusting the certificate the next time it tries to authenticate.

How does the client communicate and present the certificate to Azure AD during authentication?

During authentication, the client presents the certificate to Azure AD over a secure HTTPS connection.

Can both Work accounts and Microsoft accounts used certificate-based authentication in Azure AD?

Only Work accounts can leverage certificate-based authentication; Microsoft accounts cannot.

What happens if the certificate used for authentication is expired?

If the certificate is expired, Azure AD will reject the authentication request because it will no longer trust the certificate.

Can a client certificate be used for multi-factor authentication?

Yes, a client certificate can be one part of a multi-factor authentication process.

Can I choose which applications will use certificate-based authentication?

Yes, in Azure AD administrators have to specify which applications should use certificate-based authentication, it is not enabled by default.