You need the AWS account alias for the credentials found by the SDK's default credential provider, and you don't want to/can't install the AWS CLI.
The AWS authentication backend in Hashicorp Vault requires the roles to be uniquely named. If you have multiple AWS accounts you wish to authenticate against identical roles, you have two options:
- Mount the AWS authentication backend multiple times, and duplicate the roles with changed AWS account IDs. This requires having a way to detect which account you're running in, and changing the API endpoint you use based off that.
- Mount the AWS authentication backend once, follow the cross account access guide, and prefix the Vault roles with a string depending on the account. This tool facilitates that.