AWS::SNS::TopicPolicy:

Properties:
  PolicyDocument: |
    {
       "Id"      => "MyTopicPolicy",
       "Version" => "2012-10-17",
       "Statement" => [ {
          "Sid"       => "My-statement-id",
          "Effect"    => "Allow",
          "Principal" => {
             "AWS" => FnGetAtt("myuser", "Arn") 
          },
          "Action"   => "sns:Publish",
          "Resource" => "*"
       } ]
    }
  Topics: |
    [ "List of SNS topic ARNs" ]