# ###################################
##       Rule Specification        ##
#####################################
# 
# Rule Identifier:
#   autoscaling_launch_config_public_ip_disabled_check
# 
# Description:
#   This control checks whether Amazon EC2 Auto Scaling groups have public IP addresses configured through launch configurations.
# 
# Reports on:
#   AWS::AutoScaling::LaunchConfiguration
# 
# Evaluates:
#   AWS CloudFormation, AWS CloudFormation hook
# 
# Rule Parameters:
#   None
# 
# Scenarios:
#   Scenario: 1
#     Given: The input document is an AWS CloudFormation or CloudFormation hook document
#       And: The input document does not contain any Auto Scaling Launch Configuration resources
#      Then: SKIP
#   Scenario: 2
#     Given: The input document is an AWS CloudFormation or CloudFormation hook document
#       And: The input document contains an Auto Scaling Launch Configuration Resource
#       And: 'AssociatePublicIpAddress' is not present on the Auto Scaling Launch Configuration resource
#      Then: FAIL
#   Scenario: 3
#     Given: The input document is an AWS CloudFormation or CloudFormation hook document
#       And: The input document contains an Auto Scaling Launch Configuration Resource
#       And: 'AssociatePublicIpAddress' is present on the Auto Scaling Launch Configuration resource
#            and is set to bool(true)
#      Then: FAIL
#   Scenario: 4
#     Given: The input document is an AWS CloudFormation or CloudFormation hook document
#       And: The input document contains an Auto Scaling Launch Configuration Resource
#       And: 'AssociatePublicIpAddress' is present on the Auto Scaling Launch Configuration resource
#            and is set to bool(false)
#      Then: PASS

#
# Constants
#
let AUTOSCALING_LAUNCH_CONFIGURATION_TYPE = 'AWS::AutoScaling::LaunchConfiguration'
let INPUT_DOCUMENT = this

#
# Assignments
#
let autoscaling_launch_configurations = Resources.*[ Type == %AUTOSCALING_LAUNCH_CONFIGURATION_TYPE ]

#
# Primary Rules
#
rule autoscaling_launch_config_public_ip_disabled_check when is_cfn_template(%INPUT_DOCUMENT)
                                                             %autoscaling_launch_configurations not empty {

    check(%autoscaling_launch_configurations.Properties)
        <<
        [CT.AUTOSCALING.PR.5]: Require that an Amazon EC2 Auto Scaling group launch configuration does not have Amazon EC2 instances with public IP addresses
        [FIX]: Set the value of 'AssociatePublicIpAddress' to false on Auto Scaling Launch Configurations.
        >>

}

rule autoscaling_launch_config_public_ip_disabled_check when is_cfn_hook(%INPUT_DOCUMENT, %AUTOSCALING_LAUNCH_CONFIGURATION_TYPE) {

    check(%INPUT_DOCUMENT.%AUTOSCALING_LAUNCH_CONFIGURATION_TYPE.resourceProperties)
        <<
        [CT.AUTOSCALING.PR.5]: Require that an Amazon EC2 Auto Scaling group launch configuration does not have Amazon EC2 instances with public IP addresses
        [FIX]: Set the value of 'AssociatePublicIpAddress' to false on Auto Scaling Launch Configurations.
        >>
}

#
# Parameterized Rules
#
rule check(launch_configuration) {
    %launch_configuration {
        # Scenario 2
        AssociatePublicIpAddress exists
        # Scenarios 3 and 4
        AssociatePublicIpAddress == false
    }
}

#
# Utility Rules
#
rule is_cfn_template(doc) {
    %doc {
        AWSTemplateFormatVersion exists or
        Resources exists
    }
}

rule is_cfn_hook(doc, RESOURCE_TYPE) {
    %doc.%RESOURCE_TYPE.resourceProperties exists
}