# ###################################
##       Rule Specification        ##
#####################################
# 
# Rule Identifier:
#   ecs_containers_nonprivileged_check
# 
# Description:
#   This control checks whether container definitions in Amazon Elastic Container Service (ECS) task definitions are configured with elevated privileges.
# 
# Reports on:
#   AWS::ECS::TaskDefinition
# 
# 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 task definition resource
#      Then: SKIP
#   Scenario: 2
#     Given: The input document is an AWS CloudFormation or CloudFormation hook document
#       And: The input document contains an ECS task definition resource
#       And: 'ContainerDefinitions' property is not present or is an empty list
#      Then: SKIP
#   Scenario: 3
#     Given: The input document is an AWS CloudFormation or CloudFormation hook document
#       And: The input document contains an ECS task definition resource
#       And: 'ContainerDefinitions' property is present
#       And: One or more containers defined  in 'ContainerDefinitions' have 'Privileged' 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 ECS task definition resource
#       And: 'ContainerDefinitions' property is present
#       And: All containers defined in 'ContainerDefinitions' either do not have the 'Privileged' property present or
#            'Privileged' is present and set to bool(false)
#      Then: PASS

#
# Constants
#
let ECS_TASK_DEFINITION_TYPE = "AWS::ECS::TaskDefinition"
let INPUT_DOCUMENT = this

#
# Assignments
#
let ecs_task_definitions = Resources.*[ Type == %ECS_TASK_DEFINITION_TYPE ]

#
# Primary Rules
#
rule ecs_containers_nonprivileged_check when is_cfn_template(%INPUT_DOCUMENT)
                                             %ecs_task_definitions not empty {
    check(%ecs_task_definitions.Properties)
        <<
        [CT.ECS.PR.11]: Require an Amazon ECS container to run as non-privileged
        [FIX]: Be sure that all containers defined in 'ContainerDefinitions' either omit the 'Privileged' property, or that they set 'Privileged' to 'false'.
        >>
}

rule ecs_containers_nonprivileged_check when is_cfn_hook(%INPUT_DOCUMENT, %ECS_TASK_DEFINITION_TYPE) {
    check(%INPUT_DOCUMENT.%ECS_TASK_DEFINITION_TYPE.resourceProperties)
        <<
        [CT.ECS.PR.11]: Require an Amazon ECS container to run as non-privileged
        [FIX]: Be sure that all containers defined in 'ContainerDefinitions' either omit the 'Privileged' property, or that they set 'Privileged' to 'false'.
        >>
}

#
# Parameterized Rules
#
rule check(ecs_task_definition) {
    %ecs_task_definition [
        filter_container_definitions_is_present(this)
    ]{
        ContainerDefinitions[*] {
            # Scenario 3
            Privileged not exists or

            # Scenario 4
            Privileged == false
        }
    }
}

rule filter_container_definitions_is_present(ecs_task_definition) {
    %ecs_task_definition {
        # Scenario 2
        ContainerDefinitions exists
        ContainerDefinitions is_list
        ContainerDefinitions not empty
    }
}

#
# 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
}