cfn-ec2.json

"Parameters": {
  "KeyName": {
    "Description" : "The name of an existing EC2 keypair for this instance",
    "Type": "AWS::EC2::KeyPair::KeyName",
    "MinLength": "1",
    "MaxLength": "255",
    "AllowedPattern" : "[\\x20-\\x7E]*",
    "ConstraintDescription" : "can contain only ASCII characters.",
    "Default": "First_EC2"
  },

  "SSHLocation" : {
    "Description" : "The IP address range that can be used to SSH to the EC2 instances",
    "Type": "String",
    "MinLength": "9",
    "MaxLength": "18",
    "Default": "0.0.0.0/0",
    "AllowedPattern": "(\\d{1,3})\\.(\\d{1,3})\\.(\\d{1,3})\\.(\\d{1,3})/(\\d{1,2})",
    "ConstraintDescription": "must be a valid IP CIDR range of the form x.x.x.x/x."
 }
}