Amazon S3 - Token Vending Machines/IAM

Question

I have the following policy configured in a IAM user and in one TVM because I need acces from S3 in an Android app but, whenever I try to save my credentials i get the same "500 - Server error". I dont have idea about the problem but i guess that the policy is bad configured:

{
  "Statement": [
    {
      "Effect": "Allow",
      "Action": "sts:GetFederationToken",
      "Resource": "*"
    },
    {
      "Effect": "Allow",
      "Action": "iam:GetUser",
      "Resource": "*"
    },
    {
      "Effect": "Allow",
      "Action": "s3:*",
      "Resource": "*"
    }
  ]
}

Answer 1

Disclamer: this answer was moved from the question to a community wiki here.

---

Solution: The problem was that I also needed to add permissions for sdb, where the credentials are stored.