Mapping to the certificateUserIds attribute in Microsoft Entra ID

User objects in Microsoft Entra ID have an attribute named certificateUserIds.

  • The certificateUserIds attribute is multivalued and can hold up to 5 values.
  • Each value can be no more than 1024 characters.
  • Each value must be unique. Once a value is present on one user account, it can't be written to any other user account in the same Entra ID tenant.
  • The value doesn't need to be in email ID format. The certificateUserIds attribute can store nonroutable user principal names (UPNs) like bob@woodgrove or bob@local.

Note

Although each value must be unique in Entra ID, you can map a single certificate to multiple accounts by implementing multiple username bindings. For more information, see Multiple username bindings.

Supported patterns for certificate user IDs

The values stored in certificateUserIds should be in the format described in the following table. The X509:<Mapping> prefixes are case-sensitive.

Certificate mapping Field Examples of values in certificateUserIds
PrincipalName X509:<PN>bob@woodgrove.com
PrincipalName X509:<PN>bob@woodgrove
RFC822Name X509:<RFC822>user@woodgrove.com
IssuerAndSubject X509:<I>DC=com,DC=contoso,CN=CONTOSO-DC-CA<S>DC=com,DC=contoso,OU=UserAccounts,CN=mfatest
Subject X509:<S>DC=com,DC=contoso,OU=UserAccounts,CN=mfatest
SKI X509:<SKI>123456789abcdef
SHA1PublicKey X509:<SHA1-PUKEY>123456789abcdef
IssuerAndSerialNumber X509:<I>DC=com,DC=contoso,CN=CONTOSO-DC-CA<SR>b24134139f069b49997212a86ba0ef48
To get the correct value for serial number, run this command and store the value shown in certificateUserIds:
Syntax:
Certutil –dump –v [~certificate path~] >> [~dumpFile path~]
Example:
certutil -dump -v firstusercert.cer >> firstCertDump.txt

Roles to update certificateUserIds

Cloud-only users must have at least Privileged Authentication Administrator role to update certificateUserIds. Cloud-only users can use either the Microsoft Entra admin center or Microsoft Graph to update certificateUserIds.

Synchronized users must have at least Hybrid Identity Administrator role to update certificateUserIds. Only Microsoft Entra Connect can be used to update certificateUserIds by synchronizing the value from on-premises.

Note

Active Directory administrators can make changes that impact the certificateUserIds value in Microsoft Entra ID for any synchronized account. Administrators can include accounts with delegated administrative privilege over synchronized user accounts, or administrative rights over the Microsoft Entra Connect servers.

Update certificateUserIds

Use the following steps to update certificateUserIds for users:

  1. Sign in to the Microsoft Entra admin center as at least a Privileged Authentication Administrator for cloud-only users or as at least a Hybrid Identity Administrator for synchronized users.

  2. Search for and select All users.

    Screenshot of test user account.

  3. Click a user, and click Edit Properties.

  4. Next to Authorization info, click View.

    Screenshot of View authorization info.

  5. Click Edit certificate user IDs.

    Screenshot of Edit certificate user IDs.

  6. Click Add.

    Screenshot of how to add a certificateUserIds.

  7. Enter the value and click Save. You can add up to four values, each of 120 characters.

    Screenshot of a value to enter for certificateUserIds.

Update certificateUserIds using Microsoft Graph queries

The following examples show how to use Microsoft Graph to look up certificateUserIds and update them.

Look up certificateUserIds

Authorized callers can run Microsoft Graph queries to find all the users with a given certificateUserId value. On the Microsoft Graph user object, the collection of certificateUserIds is stored in the authorizationInfo property.

To retrieve certificateUserIds of all user objects:

GET https://graph.microsoft.com/v1.0/users?$select=authorizationinfo
ConsistencyLevel: eventual

To retrieve certificateUserIds for a given user by user's ObjectId:

GET https://graph.microsoft.com/v1.0/users/{user-object-id}?$select=authorizationinfo
ConsistencyLevel: eventual

To retrieve the user object with a specific value in certificateUserIds:

GET https://graph.microsoft.com/v1.0/users?$select=authorizationinfo&$filter=authorizationInfo/certificateUserIds/any(x:x eq 'X509:<PN>user@contoso.com')&$count=true
ConsistencyLevel: eventual

You can also use the not and startsWith operators to match the filter condition. To filter against the certificateUserIds object, the request must include the $count=true query string, and the ConsistencyLevel header must be set to eventual.

Update certificateUserIds

Run a PATCH request to update the certificateUserIds for a given user.

Request body

PATCH https://graph.microsoft.com/v1.0/users/{user-object-id}
Content-Type: application/json
{
    "authorizationInfo": {
        "certificateUserIds": [
            "X509:<PN>123456789098765@mil"
        ]
    }
}

Update certificateUserIds using PowerShell commands

For this configuration, you can use Microsoft Graph PowerShell.

  1. Start PowerShell with administrator privileges.

  2. Install and import the Microsoft Graph PowerShell SDK.

        Install-Module Microsoft.Graph -Scope AllUsers
        Import-Module Microsoft.Graph.Authentication
        Set-ExecutionPolicy -ExecutionPolicy RemoteSigned -Scope CurrentUser
    
  3. Connect to the tenant and accept all.

       Connect-MGGraph -Scopes "Directory.ReadWrite.All", "User.ReadWrite.All" -TenantId <tenantId>
    
  4. List certificateUserIds attribute of a given user.

      $results = Invoke-MGGraphRequest -Method get -Uri 'https://graph.microsoft.com/v1.0/users/<userId>?$select=authorizationinfo' -OutputType PSObject -Headers @{'ConsistencyLevel' = 'eventual' }
      #list certificateUserIds
      $results.authorizationInfo
    
  5. Create a variable with certificateUserIds values.

      #Create a new variable to prepare the change. Ensure that you list any existing values you want to keep as this operation will overwrite the existing value
      $params = @{
            authorizationInfo = @{
                  certificateUserIds = @(
                  "X509:<SKI>eec6b88788d2770a01e01775ce71f1125cd6ad0f", 
                  "X509:<PN>user@contoso.com"
                  )
            }
      }
    
  6. Update the certificateUserIds attribute.

       $results = Invoke-MGGraphRequest -Method patch -Uri 'https://graph.microsoft.com/v1.0/users/<UserId>/?$select=authorizationinfo' -OutputType PSObject -Headers @{'ConsistencyLevel' = 'eventual' } -Body $params
    

Update certificateUserIds using user object

  1. Get the user object.

      $userObjectId = "6b2d3bd3-b078-4f46-ac53-f862f35e10b6"
      $user = Get-MgUser -UserId $userObjectId -Property AuthorizationInfo
    
  2. Update the certificateUserIds attribute of the user object.

       $user.AuthorizationInfo.certificateUserIds = @("X509:<SKI>eec6b88788d2770a01e01775ce71f1125cd6ad0f", "X509:<PN>user1@contoso.com") 
       Update-MgUser -UserId $userObjectId -AuthorizationInfo $user.AuthorizationInfo
    

Update certificateUserIds using Microsoft Entra Connect

Microsoft Entra connect supports synchronizing values to certificateUserIds from an on-premises Active Directory environment. On-premises Active Directory supports certificate-based authentication and multiple username bindings. Make sure you use the latest version of Microsoft Entra Connect.

To use these mapping methods, you need to populate the altSecurityIdentities attribute of user objects in the on-premises Active Directory. In addition, after you apply certificate-based authentication changes on Windows domain controllers as described in KB5014754, you may have implemented some of the non-reusable mapping methods (Type=strong) mapping methods to meet the on-premise Active Directory strong certificate binding enforcement requirements.

To prevent synchronization errors, make sure the values being synchronized follow one of the supported formats for the certificateUserIds.

Before you begin, make sure all user accounts that are synchronized from on-premises Active Directory have:

  • 5 or fewer values in their altSecurityIdentities attributes

  • No value with more then 1024 characters

  • No duplicate values

    Carefully consider if a duplicate value is meant to map a single certificate to multiple on-premises Active Directory accounts. For more information, see Multiple username bindings.

    Note

    In specific scenarios, a subset of users might have a valid business justification to map a single certificate to more than one on-premises Active Directory account. Review these scenarios and where needed, implement separate mapping methods to map to more then one account in both the on-premises Active Directory and Entra ID.

Considerations for ongoing synchronization of certificateUserIds

  • Ensure that the provisioning process for populating the values in on-premises Active Directory implements proper hygiene. Only values associated with current valid certificates are populated.
  • Values are removed when the corresponding certificate is expired or revoked.
  • Values larger then 1024 characters aren't populated.
  • Duplicate values aren't provisioned.
  • Use Microsoft Entra Connect Health to monitor synchronization.

Follow these steps to configure Microsoft Entra Connect to synchronize userPrincipalName to certificateUserIds:

  1. On the Microsoft Entra Connect server, find and start the Synchronization Rules Editor.

    Screenshot of Synchronization Rules Editor.

  2. Click Direction, and click Outbound.

    Screenshot of outbound synchronization rule.

  3. Find the rule Out to Microsoft Entra ID – User Identity, click Edit, and click Yes to confirm.

    Screenshot of user identity.

  4. Enter a high number in the Precedence field, and then click Next.

    Screenshot of a precedence value.

  5. Click Transformations > Add transformation. You may need to scroll down the list of transformations before you can create a new one.

Synchronize X509:<PN>PrincipalNameValue

To synchronize X509:<PN>PrincipalNameValue, create an outbound synchronization rule, and choose Expression in the flow type. Choose the target attribute as certificateUserIds, and in the source field, add the following expression. If your source attribute isn't userPrincipalName, you can change the expression accordingly.

"X509:<PN>"&[userPrincipalName]

Screenshot of how to sync x509.

Synchronize X509:<RFC822>RFC822Name

To synchronize X509:<RFC822>RFC822Name, create an outbound synchronization rule and choose Expression in the flow type. Choose the target attribute as certificateUserIds, and in the source field, add the following expression. If your source attribute isn't userPrincipalName, you can change the expression accordingly.

"X509:<RFC822>"&[userPrincipalName]

Screenshot of how to sync RFC822Name.

  1. Click Target Attribute, select certificateUserIds, click Source, select userPrincipalName, and then click Save.

    Screenshot of how to save a rule.

  2. Click OK to confirm.

Important

The preceding examples use userPrincipalName atribute as a source attribute in the transform rule. You can use any available attribute with the appropriate value. For example, some organizations use the mail attribute. For more complex transform rules, see Microsoft Entra Connect Sync: Understanding Declarative Provisioning Expressions

For more information about declarative provisioning expressions, see Microsoft Entra Connect: Declarative Provisioning Expressions.

Synchronize altSecurityIdentities attribute from Active Directory to Microsoft Entra ID certificateUserIds

The altSecurityIdentities attribute isn't part of the default attributes set. An administrator needs to add a new attribute to the person object in the Metaverse, and then create the appropriate synchronization rules to relay this data to certificateUserIds in Entra ID.

  1. Open Metaverse Designer and select the person object. To create the alternativeSecurityId attribute, click New attribute. Select String (non-indexable) to create an attribute size up to 1024 characters, which is the maximum supported length for certificateUserIds. If you select String (indexable), the maximum size of an attribute value is 448 characters. Make sure you select Multi-valued.

    Screenshot of how to create a new attribute.

  2. Open Metaverse Designer, and select alternativeSecurityId to add it to the person object.

    Screenshot of how to add alternativeSecurityId to the person object.

  3. Create an inbound synchronization rule to transform from altSecurityIdentities to alternativeSecurityId attribute.

    In the inbound rule, use the following options.

    Option Value
    Name Descriptive name of the rule, such as: In from Active Directory - altSecurityIdentities
    Connected System Your on-premises Active Directory domain
    Connected System Object Type user
    Metaverse Object Type person
    Precedence Choose a number under 100 that isn't currently used

    Then click Transformations and create a direct mapping to the target attribute alternativeSecurityId from the source attribute altSecurityIdentities, as shown in the following screenshot.

    Screenshot of how to transform from altSecurityIdentities to alternateSecurityId attribute.

  4. Create an outbound synchronization rule to transform from the alternativeSecurityId attribute to the certificateUserIds attribute in Entra ID.

    Option Value
    Name Descriptive name of the rule, such as: Out to Microsoft Entra ID - certificateUserIds
    Connected System Your Microsoft Entra domain
    Connected System Object Type user
    Metaverse Object Type person
    Precedence Choose a high number not currently used above all default rules, such as 150

    Then click Transformations and create a direct mapping to the target attribute certificateUserIds from the source attribute alternativeSecurityId, as shown in the following screenshot.

    Screenshot of outbound synchronization rule to transform from alternateSecurityId attribute to certificateUserIds.

  5. Run the synchronization to populate data to the certificateUserIds attribute.

  6. To verify success, view the Authorization info of a user in Entra ID.

    Screenshot of successful synchronization.

To map a subset of values from the altSecurityIdentities attribute, replace the Transformation in step 4 with an Expression. To use an Expression, proceed to the Transformations tab and change your FlowType option to Expression, the target attribute to certificateUserIds, and then input the expression into the Source field. The following example filters only values that align to the SKI and SHA1PublicKey Certificate mapping fields:

Screenshot of an Expression.

Expression code:

IIF(IsPresent([alternativeSecurityId]),
                Where($item,[alternativeSecurityId],BitOr(InStr($item, "X509:<SKI>"),InStr($item, "X509:<SHA1-PUKEY>"))>0),[alternativeSecurityId]
)

Administrators can filter values from altSecurityIdentities that align with the supported patterns. Ensure that the CBA configuration has been updated to support the username bindings that are being synchronized to certificateUserIds to enable authentication using these values.

Next steps