Modern Authentication for Entra Connect Sync Now Available

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Microsoft has introduced modern authentication for Entra Connect Sync, replacing the traditional username/password method with a more secure Service Principal authentication using certificates. This enhancement eliminates issues caused by Conditional Access (CA) policy misconfigurations that previously disrupted synchronization.

Key Features:

  • Certificate-based authentication instead of password-based.
  • Three deployment options:
  • Let Entra Connect Sync manage certificates automatically.
  • Bring your own app and certificate.
  • Bring your own certificate (TPM storage recommended).
  • Improved security by removing dependency on user accounts vulnerable to MFA disruptions.

Documentation: Modern Auth for Entra Connect Sync
Helper Script: GitHub Helper Script

You Should Know:

How to Configure Modern Auth for Entra Connect Sync

Step 1: Verify Prerequisites

  • Ensure Entra Connect Sync version 2.2.0.0 or later.
  • Permissions to register applications in Entra ID.

Step 2: Generate a Self-Signed Certificate (Optional)

If not using auto-certificate management, generate a certificate:

 Generate a self-signed certificate 
$cert = New-SelfSignedCertificate -CertStoreLocation "Cert:\LocalMachine\My" -Subject "CN=EntraSyncCert" -KeySpec KeyExchange -NotAfter (Get-Date).AddYears(2) 
Export-Certificate -Cert $cert -FilePath "C:\Temp\EntraSyncCert.cer"

Step 3: Register a Service Principal in Entra ID 

 Connect to Entra ID 
Connect-MgGraph -Scopes "Application.ReadWrite.All"

Register a new application 
$app = New-MgApplication -DisplayName "EntraConnectSync_SPN" 
New-MgServicePrincipal -AppId $app.AppId

Step 4: Assign Certificate to the Service Principal

 Upload the certificate 
$certBytes = [System.IO.File]::ReadAllBytes("C:\Temp\EntraSyncCert.cer") 
$base64Cert = [System.Convert]::ToBase64String($certBytes) 
Update-MgApplication -ApplicationId $app.Id -KeyCredentials @( 
@{ 
Type = "AsymmetricX509Cert" 
Usage = "Verify" 
Key = $base64Cert 
} 
)

Step 5: Configure Entra Connect Sync

1. Open Entra Connect Wizard.

2. Select Configure > Customize Synchronization Options.

3. Choose Use Service Principal Authentication.

4. Provide the Application ID and Certificate Thumbprint.

Step 6: Verify Synchronization

 Check synchronization status 
Get-ADSyncScheduler

What Undercode Say

This update is a significant security improvement, reducing risks associated with password-based authentication. However, organizations must ensure proper certificate management (TPM storage recommended) to prevent theft.

Additional Security Commands

  • Check Certificate Validity: 
    Get-ChildItem -Path Cert:\LocalMachine\My | Where-Object { $_.Subject -like "EntraSync" }
  • Revoke a Compromised Certificate: 
    Remove-MgApplicationKey -ApplicationId $app.Id -KeyId $cert.Thumbprint
  • Monitor Entra Sync Logs: 
    tail -f /var/log/azure-ad-connect.log

Expected Output:

A secure, MFA-resistant synchronization process with reduced attack surface.

Prediction

Future updates may include deeper integration with Azure Key Vault for automated certificate rotation and enhanced hybrid identity protections.

IT/Security Reporter URL:

Reported By: Nathanmcnulty Its – Hackers Feeds
Extra Hub: Undercode MoN
Basic Verification: Pass ✅

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