Can an aws IAM policy dynamically refer to the logged in username?

Question

I am trying to write an IAM policy which will control access to EC2 instances. All EC2 instances will have a custom tag called username and only if the tag value matches the logged in user's user name, will that user have access to that EC2 instance. This is what I came up with:

{
    "Version": "2012-10-12",
    "Statement": [
        {
            "Effect": "Allow",
            "Action": "ec2:*",
            "Resource": "*",
            "Condition": {
                "StringEquals": {
                    "ec2:ResourceTag/username": "arn:aws:iam::account-number-without-hyphens:user/username1"
                }
            }
        }
    ]
}

I am sure you see the problem here. I don't want to hard code the username value on the right hand side. I want to be able to get that information at runtime or policy evaluation time.

Is it possible to do so?

Answer 1

The IAM user can be referred to in policy documents by ${aws:username}.

There is a list of other IAM policy variables and their uses here:

http://docs.aws.amazon.com/IAM/latest/UserGuide/PolicyVariables.html