AWS IoT
Developer Guide

AWS IoT Policy Variables

AWS IoT defines policy variables that can be used in AWS IoT policies within the resource or condition block. When a policy is evaluated, the policy variables are replaced by actual values. For example, if a device connected to the AWS IoT message broker with a client ID of "100-234-3456," the iot:ClientId policy variable would be replaced in the policy document by "100-234-3456." For more information about policy variables, see IAM Policy Variables and Multi-Value Conditions.