Using Federated Identity Credentials to connect AEMaaCS to Azure services?

To connect Adobe Experience Manager as a Cloud Service (AEMaaCS) to Azure services-such as Azure Key Vault-using a user-assigned managed identity and federated identity credentials, you can avoid using client secrets or pinned client certificates by leveraging Azure's workload identity federation features.
Try the below steps - 

1. Create a User-Assigned Managed Identity

az identity create --name aem-identity --resource-group my-rg --location eastus

2. Assign the Managed Identity Required Permissions - Give it access to KeyVault for example
az keyvault set-policy --name my-keyvault --object-id <object-id> --secret-permissions get

3. Configure a Federated Identity Credential

• In the Azure portal, navigate to your user-assigned managed identity.

• Add Credential under Federated credentials in Settings
• Choose Other Issuer - Issuer, Subject, Audience, Name

4.  Configure AEMaaCS to Issue Tokens

But please note IdP guest users (external users on a different domain to the main enterprise) are not supported as IMS federated ID users. Thus, guest/external users cannot be used to authenticate from AEMaaCS to Azure via federated identity credentials.

If you need to allow external users or systems to access Azure resources, you must:

• Issue them identities on your claimed domain or

• Use a different authentication mechanism (such as service principals with client secrets/certificates, or Azure AD app registrations).

Please go through the below documentation links too - 

• Adobe IMS Documentation – Identity Types

• Azure Federated Identity Credentials

• Adobe IMS Survival Guide (Medium)

Hope this helps!

Regards,
Rohan Garg