# ###################################
##       Rule Specification        ##
#####################################
# 
# Rule Identifier:
#   ecs_service_assign_public_ip_disabled_check
# 
# Description:
#   This control checks whether your Amazon ECS services are configured to assign public IP addresses automatically.
# 
# Reports on:
#   AWS::ECS::Service
# 
# 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 an ECS service resource
#      Then: SKIP
#   Scenario: 2
#     Given: The input document is an AWS CloudFormation or CloudFormation hook document
#       And: The input document contains an ECS service resource
#       And: 'NetworkConfiguration' property is not present
#      Then: SKIP
#   Scenario: 3
#     Given: The input document is an AWS CloudFormation or CloudFormation hook document
#       And: The input document contains an ECS service resource
#       And: 'NetworkConfiguration.AwsvpcConfiguration' property is not present
#      Then: SKIP
#   Scenario: 4
#     Given: The input document is an AWS CloudFormation or CloudFormation hook document
#       And: The input document contains an ECS service resource
#       And: 'NetworkConfiguration.AwsvpcConfiguration' property is present
#       And: 'AssignPublicIp' property is present and set to 'ENABLED'
#      Then: FAIL
#   Scenario: 5
#     Given: The input document is an AWS CloudFormation or CloudFormation hook document
#       And: The input document contains an ECS service resource
#       And: 'NetworkConfiguration.AwsvpcConfiguration' property is present
#       And: 'AssignPublicIp' property is not present
#      Then: PASS
#   Scenario: 6
#     Given: The input document is an AWS CloudFormation or CloudFormation hook document
#       And: The input document contains an ECS service resource
#       And: 'NetworkConfiguration.AwsvpcConfiguration' property is present
#       And: 'AssignPublicIp' property is present and set to 'DISABLED'
#      Then: PASS

#
# Constants
#
let ECS_SERVICE_TYPE = "AWS::ECS::Service"
let INPUT_DOCUMENT = this

#
# Assignments
#
let ecs_services = Resources.*[ Type == %ECS_SERVICE_TYPE ]

#
# Primary Rules
#
rule ecs_service_assign_public_ip_disabled_check when is_cfn_template(%INPUT_DOCUMENT)
                                                      %ecs_services not empty {
    check(%ecs_services.Properties)
        <<
        [CT.ECS.PR.9]: Require Amazon ECS services not to assign public IP addresses automatically
        [FIX]: Set 'AssignPublicIp' in 'NetworkConfiguration.AwsvpcConfiguration' to 'DISABLED'.
        >>
}

rule ecs_service_assign_public_ip_disabled_check when is_cfn_hook(%INPUT_DOCUMENT, %ECS_SERVICE_TYPE) {
    check(%INPUT_DOCUMENT.%ECS_SERVICE_TYPE.resourceProperties)
        <<
        [CT.ECS.PR.9]: Require Amazon ECS services not to assign public IP addresses automatically
        [FIX]: Set 'AssignPublicIp' in 'NetworkConfiguration.AwsvpcConfiguration' to 'DISABLED'.
        >>
}

#
# Parameterized Rules
#
rule check(ecs_service) {
    %ecs_service [filter_ecs_service_with_vpc_configuration(this)] {
        NetworkConfiguration {
            AwsvpcConfiguration {
                # Scenario 5
                AssignPublicIp not exists or

                # Scenario 6
                check_assign_public_ip_property(AssignPublicIp)
            }
        }
    }
}

rule check_assign_public_ip_property(public_ip) {
    %public_ip {
        this is_string
        this == "DISABLED"
    }
}

rule filter_ecs_service_with_vpc_configuration(ecs_service) {
    %ecs_service {
        # Scenario 2
        NetworkConfiguration exists
        NetworkConfiguration is_struct

        # Scenarion 3 and 4
        NetworkConfiguration {
            AwsvpcConfiguration exists
            AwsvpcConfiguration is_struct
        }
    }
}

#
# 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
}