# ###################################
##       Rule Specification        ##
#####################################
# 
# Rule Identifier:
#   redshift_cluster_public_access_check
# 
# Description:
#   This control checks whether Amazon Redshift clusters are configured to not be publicly accessible.
# 
# Reports on:
#   AWS::Redshift::Cluster
# 
# Evaluates:
#   AWS CloudFormation, AWS CloudFormation hook
# 
# Rule Parameters:
#   None
# 
# Scenarios:
#   Scenario: 1
#     Given: The input document is an AWS CloudFormation document or CloudFormation hook document
#       And: The input document does not contain any Redshift cluster resources
#      Then: SKIP
#   Scenario: 2
#     Given: The input document is an AWS CloudFormation document or CloudFormation hook document
#       And: The input document contains a Redshift cluster resource
#       And: 'PubliclyAccessible' has not been specified
#      Then: FAIL
#   Scenario: 3
#     Given: The input document is an AWS CloudFormation document or CloudFormation hook document
#       And: The input document contains a Redshift cluster resource
#       And: 'PubliclyAccessible' has been specified
#       And: 'PubliclyAccessible' has been set to bool(true)
#      Then: FAIL
#   Scenario: 4
#     Given: The input document is an AWS CloudFormation document or CloudFormation hook document
#       And: The input document contains a Redshift cluster resource
#       And: 'PubliclyAccessible' has been specified
#       And: 'PubliclyAccessible' has been set to bool(false)
#      Then: PASS

#
# Constants
#
let REDSHIFT_CLUSTER_TYPE = "AWS::Redshift::Cluster"
let INPUT_DOCUMENT = this

#
# Assignments
#
let redshift_clusters = Resources.*[ Type == %REDSHIFT_CLUSTER_TYPE ]

#
# Primary Rules
#
rule redshift_cluster_public_access_check when is_cfn_template(%INPUT_DOCUMENT)
                                               %redshift_clusters not empty  {
    check(%redshift_clusters.Properties)
         <<
        [CT.REDSHIFT.PR.1]: Require an Amazon Redshift cluster to prohibit public access
        [FIX]: Set 'PubliclyAccessible' to 'false'.
        >>
}

rule redshift_cluster_public_access_check when is_cfn_hook(%INPUT_DOCUMENT, %REDSHIFT_CLUSTER_TYPE) {
    check(%INPUT_DOCUMENT.%REDSHIFT_CLUSTER_TYPE.resourceProperties)
         <<
        [CT.REDSHIFT.PR.1]: Require an Amazon Redshift cluster to prohibit public access
        [FIX]: Set 'PubliclyAccessible' to 'false'.
        >>
}

#
# Parameterized Rules
#
rule check(redshift_cluster) {
    %redshift_cluster {
        # Scenario 2
        PubliclyAccessible exists
        # Scenario 3 & 4
        PubliclyAccessible == 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
}