# ###################################
##       Rule Specification        ##
#####################################
# 
# Rule Identifier:
#   eks_endpoint_no_public_access_check
# 
# Description:
#   This control checks whether an Amazon Elastic Kubernetes Service (EKS) cluster endpoint disallows public access to the cluster Kubernetes API server endpoint.
# 
# Reports on:
#   AWS::EKS::Cluster
# 
# 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 Amazon EKS cluster resources
#      Then: SKIP
#   Scenario: 2
#     Given: The input document is an AWS CloudFormation or CloudFormation hook document
#       And: The input document contains an Amazon EKS cluster resource
#       And: 'EndpointPublicAccess' in 'ResourcesVpcConfig' has not been provided
#       And: 'EndpointPrivateAccess' in 'ResourcesVpcConfig' has not been provided
#      Then: FAIL
#   Scenario: 3
#     Given: The input document is an AWS CloudFormation or CloudFormation hook document
#       And: The input document contains an Amazon EKS cluster resource
#       And: 'EndpointPrivateAccess' in 'ResourcesVpcConfig' has not been provided
#       And: 'EndpointPublicAccess' in 'ResourcesVpcConfig' has not been provided or has been provided and set to a
#            value other than bool(false)
#      Then: FAIL
#   Scenario: 4
#     Given: The input document is an AWS CloudFormation or CloudFormation hook document
#       And: The input document contains an Amazon EKS cluster resource
#       And: 'EndpointPublicAccess' in 'ResourcesVpcConfig' has not been provided or has been provided and set to a
#            value other than bool(false)
#       And: 'EndpointPrivateAccess' in 'ResourcesVpcConfig' has been provided and set a value other than bool(true)
#      Then: FAIL
#   Scenario: 5
#     Given: The input document is an AWS CloudFormation or CloudFormation hook document
#       And: The input document contains an Amazon EKS cluster resource
#       And: 'EndpointPublicAccess' in 'ResourcesVpcConfig' has been provided and set to bool(false)
#       And: 'EndpointPrivateAccess' in 'ResourcesVpcConfig' has been provided and set to bool(true)
#      Then: PASS

#
# Constants
#
let EKS_CLUSTER_TYPE = "AWS::EKS::Cluster"
let INPUT_DOCUMENT = this

#
# Assignments
#
let eks_clusters = Resources.*[ Type == %EKS_CLUSTER_TYPE ]

#
# Primary Rules
#
rule eks_endpoint_no_public_access_check when is_cfn_template(%INPUT_DOCUMENT)
                                              %eks_clusters not empty {
    check(%eks_clusters.Properties)
        <<
        [CT.EKS.PR.1]: Require an Amazon EKS cluster to be configured with public access disabled to the cluster Kubernetes API server endpoint.
        [FIX]: Set the value of the 'EndpointPublicAccess' parameter to false and the value of the 'EndpointPrivateAccess' parameter to true.
        >>
}

rule eks_endpoint_no_public_access_check when is_cfn_hook(%INPUT_DOCUMENT, %EKS_CLUSTER_TYPE) {
    check(%INPUT_DOCUMENT.%EKS_CLUSTER_TYPE.resourceProperties)
        <<
        [CT.EKS.PR.1]: Require an Amazon EKS cluster to be configured with public access disabled to the cluster Kubernetes API server endpoint.
        [FIX]: Set the value of the 'EndpointPublicAccess' parameter to false and the value of the 'EndpointPrivateAccess' parameter to true.
        >>
}

#
# Parameterized Rules
#
rule check(eks_cluster) {
    %eks_cluster {
        ResourcesVpcConfig exists
        ResourcesVpcConfig is_struct
        ResourcesVpcConfig {
            # Scenarios 2, 3, 4 and 5
            EndpointPublicAccess exists
            EndpointPublicAccess == false

            EndpointPrivateAccess exists
            EndpointPrivateAccess == true
        }
    }
}

#
# 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
}