Important considerations and restrictions for federated identity credentials

This article describes important considerations, restrictions, and limitations for federated identity credentials on Microsoft Entra apps and user-assigned managed identities.

For more information on the scenarios enabled by federated identity credentials, see workload identity federation overview.

General federated identity credential considerations

Applies to: applications and user-assigned managed identities

Anyone with permissions to create an app registration and add a secret or certificate can add a federated identity credential to an app. If the Users can register applications switch is set to No in the Users->User Settings blade in the Microsoft Entra admin center, however, you won't be able to create an app registration or configure the federated identity credential. Find an admin to configure the federated identity credential on your behalf, someone in the Application Administrator or Application Owner roles.

Federated identity credentials don't consume the Microsoft Entra tenant service principal object quota.

A maximum of 20 federated identity credentials can be added to an application or user-assigned managed identity.

When you configure a federated identity credential, there are several important pieces of information to provide:

• issuer and subject are the key pieces of information needed to set up the trust relationship. The combination of issuer and subject must be unique on the app. When the external software workload requests Microsoft identity platform to exchange the external token for an access token, the issuer and subject values of the federated identity credential are checked against the issuer and subject claims provided in the external token. If that validation check passes, Microsoft identity platform issues an access token to the external software workload.

• issuer is the URL of the external identity provider and must match the issuer claim of the external token being exchanged. Required. If the issuer claim has leading or trailing whitespace in the value, the token exchange is blocked. This field has a character limit of 600 characters.

• subject is the identifier of the external software workload and must match the sub (subject) claim of the external token being exchanged. subject has no fixed format, as each IdP uses their own - sometimes a GUID, sometimes a colon delimited identifier, sometimes arbitrary strings. This field has a character limit of 600 characters.

  Important

  The subject setting values must exactly match the configuration on the GitHub workflow configuration. Otherwise, Microsoft identity platform will look at the incoming external token and reject the exchange for an access token. You won't get an error, the exchange fails without error.

  Important

  If you accidentally add the incorrect external workload information in the subject setting the federated identity credential is created successfully without error. The error does not become apparent until the token exchange fails.

• audiences lists the audiences that can appear in the external token. Required. You must add a single audience value, which has a limit of 600 characters. The recommended value is "api://AzureADTokenExchange". It says what Microsoft identity platform must accept in the aud claim in the incoming token.

• name is the unique identifier for the federated identity credential. Required. This field has a character limit of 3-120 characters and must be URL friendly. Alphanumeric, dash, or underscore characters are supported, the first character must be alphanumeric only. It's immutable once created.

• description is the user-provided description of the federated identity credential. Optional. The description isn't validated or checked by Microsoft Entra ID. This field has a limit of 600 characters.

Wildcard characters aren't supported in any federated identity credential property value.

Unsupported regions (user-assigned managed identities)

Applies to: user-assigned managed identities

Creation of federated identity credentials is currently not supported on user-assigned managed identities created in the following regions:

• Malaysia South
• Spain Central
• Taiwan North
• Taiwan Northwest

Support for creating federated identity credentials on user assigned identities in these regions will be gradually rolled out. Resources in this region which need to use federated identity credentials, can do so by leveraging a user assigned managed identity created in a supported region.

Supported signing algorithms and issuers

Applies to: applications and user-assigned managed identities

Only issuers that provide tokens signed using the RS256 algorithm are supported for token exchange using workload identity federation. Exchanging tokens signed with other algorithms may work, but haven't been tested.

Time for federated credential changes to propagate

Applies to: applications and user-assigned managed identities

It takes time for the federated identity credential to be propagated throughout a region after being initially configured. A token request made several minutes after configuring the federated identity credential may fail because the cache is populated in the directory with old data. During this time window, an authorization request might fail with error message: AADSTS70021: No matching federated identity record found for presented assertion.

To avoid this issue, wait a short time after adding the federated identity credential before requesting a token to ensure replication completes across all nodes of the authorization service. We also recommend adding retry logic for token requests. Retries should be done for every request even after a token was successfully obtained. Eventually after the data is fully replicated the percentage of failures will drop.

Concurrent updates aren't supported (user-assigned managed identities)

Applies to: user-assigned managed identities

Creating multiple federated identity credentials under the same user-assigned managed identity concurrently triggers concurrency detection logic, which causes requests to fail with 409-conflict HTTP status code.

Terraform Provider for Azure (Resource Manager) version 3.40.0 introduces an update which creates multiple federated identity credentials sequentially instead of concurrently. Versions earlier than 3.40.0 can cause failures in pipelines when multiple federated identities are created. We recommend you use Terraform Provider for Azure (Resource Manager) v3.40.0 or later so that multiple federated identity credentials are created sequentially.

When you use automation or Azure Resource Manager templates (ARM templates) to create federated identity credentials under the same parent identity, create the federated credentials sequentially. Federated identity credentials under different managed identities can be created in parallel without any restrictions.

If federated identity credentials are provisioned in a loop, you can provision them serially by setting "mode": "serial".

You can also provision multiple new federated identity credentials sequentially using the dependsOn property. The following Azure Resource Manager template (ARM template) example creates three new federated identity credentials sequentially on a user-assigned managed identity by using the dependsOn property:

{ 
    "$schema": "https://schema.management.azure.com/schemas/2019-04-01/deploymentTemplate.json#", 
    "contentVersion": "1.0.0.0", 
    "parameters": { 
        "userAssignedIdentities_parent_uami_name": { 
            "defaultValue": "parent_uami", 
            "type": "String" 
        } 
    }, 
    "variables": {}, 
    "resources": [ 
        { 
            "type": "Microsoft.ManagedIdentity/userAssignedIdentities", 
            "apiVersion": "2022-01-31-preview", 
            "name": "[parameters('userAssignedIdentities_parent_uami_name')]", 
            "location": "eastus" 
        }, 
        { 
            "type": "Microsoft.ManagedIdentity/userAssignedIdentities/federatedIdentityCredentials", 
            "apiVersion": "2022-01-31-preview", 
            "name": "[concat(parameters('userAssignedIdentities_parent_uami_name'), '/fic01')]", 
            "dependsOn": [ 
                "[resourceId('Microsoft.ManagedIdentity/userAssignedIdentities', parameters('userAssignedIdentities_parent_uami_name'))]" 
            ], 
            "properties": { 
                "issuer": "https://kubernetes-oauth.azure.com", 
                "subject": "fic01", 
                "audiences": [ 
                    "api://AzureADTokenExchange" 
                ] 
            } 
        }, 
        { 
            "type": "Microsoft.ManagedIdentity/userAssignedIdentities/federatedIdentityCredentials", 
            "apiVersion": "2022-01-31-preview", 
            "name": "[concat(parameters('userAssignedIdentities_parent_uami_name'), '/fic02')]", 
            "dependsOn": [ 
                "[resourceId('Microsoft.ManagedIdentity/userAssignedIdentities', parameters('userAssignedIdentities_parent_uami_name'))]", 
                "[resourceId('Microsoft.ManagedIdentity/userAssignedIdentities/federatedIdentityCredentials', parameters('userAssignedIdentities_parent_uami_name'), 'fic01')]" 
            ], 
            "properties": { 
                "issuer": "https://kubernetes-oauth.azure.com", 
                "subject": "fic02", 
                "audiences": [ 
                    "api://AzureADTokenExchange" 
                ] 
            } 
        }, 
        { 
            "type": "Microsoft.ManagedIdentity/userAssignedIdentities/federatedIdentityCredentials", 
            "apiVersion": "2022-01-31-preview", 
            "name": "[concat(parameters('userAssignedIdentities_parent_uami_name'), '/fic03')]", 
            "dependsOn": [ 
                "[resourceId('Microsoft.ManagedIdentity/userAssignedIdentities', parameters('userAssignedIdentities_parent_uami_name'))]", 
                "[resourceId('Microsoft.ManagedIdentity/userAssignedIdentities/federatedIdentityCredentials', parameters('userAssignedIdentities_parent_uami_name'), 'fic02')]" 
            ], 
            "properties": { 
                "issuer": "https://kubernetes-oauth.azure.com", 
                "subject": "fic03", 
                "audiences": [ 
                    "api://AzureADTokenExchange" 
                ] 
            } 
        } 
    ] 
} 

Azure policy

Applies to: applications and user-assigned managed identities

It's possible to use a deny Azure Policy as in the following ARM template example:

{ 
"policyRule": { 
            "if": { 
                "field": "type", 
                "equals": "Microsoft.ManagedIdentity/userAssignedIdentities/federatedIdentityCredentials" 
            }, 
            "then": { 
                "effect": "deny" 
            } 
        } 
}

Throttling limits

Applies to: user-assigned managed identities

The following table describes limits on requests to the user-assigned managed identities REST APIS. If you exceed a throttling limit, you receive an HTTP 429 error.

Operation	Requests-per-second per Microsoft Entra tenant	Requests-per-second per subscription	Requests-per-second per resource
Create or update requests	10	2	0.25
Get requests	30	10	0.5
List by resource group or List by subscription requests	15	5	0.25
Delete requests	10	2	0.25

Errors

Applies to: applications and user-assigned managed identities

The following error codes may be returned when creating, updating, getting, listing, or deleting federated identity credentials.

HTTP code	Error message	Comments
405	The request format was unexpected: Support for federated identity credentials not enabled.	Federated identity credentials aren't enabled in this region. Refer to “Currently Supported regions”.
400	Federated identity credentials must have exactly one audience.	Currently, federated identity credentials support a single audience “api://AzureADTokenExchange”.
400	Federated Identity Credential from HTTP body has empty properties	All federated identity credential properties are mandatory.
400	Federated Identity Credential name '{ficName}' is invalid.	Alphanumeric, dash, underscore, no more than 3-120 symbols. First symbol is alphanumeric.
404	The parent user-assigned identity doesn't exist.	Check user assigned identity name in federated identity credentials resource path.
400	Issuer and subject combination already exists for this Managed Identity.	This is a constraint. List all federated identity credentials associated with the user-assigned identity to find existing federated identity credential.
409	Conflict	Concurrent write request to federated identity credential resources under the same user-assigned identity has been denied.