stscreds_policy.json

{
    "Version": "2012-10-17",
    "Statement": [
        {
            "Sid": ...,
            "Effect": "Allow",
            "Action": [
                "sts:GetSessionToken",
                "iam:GetUser",
                "iam:ListMFADevices"
            ],
            "Resource": [
                "arn:aws:iam::*:user/${aws:username}"
            ]
        },
        {
            "Sid": ...,
            "Effect": "Allow",
            "Action": [
                "*"
            ],
            "Condition": {
                "Bool": {
                    "aws:MultiFactorAuthPresent": "true"
                }
            },
            "Resource": [
                "*"
            ]
        }
    ]
}