# ###################################
##       Rule Specification        ##
#####################################
# 
# Rule Identifier:
#   dax_cluster_encryption_enabled_check
# 
# Description:
#   This control checks whether Amazon DynamoDB Accelerator (DAX) clusters are encrypted at rest.
# 
# Reports on:
#   AWS::DAX::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 DAX Cluster resources
#      Then: SKIP
#   Scenario: 2
#     Given: The input document is an AWS CloudFormation or CloudFormation hook document
#       And: The input document contains at least one DAX Cluster resource
#       And: 'SSESpecification' 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 at least one DAX Cluster resource
#       And: 'SSESpecification' has been provided and 'SSESpecification.SSEEnabled' is missing or has been set to a
#            value other than bool(true)
#      Then: FAIL
#   Scenario: 4
#     Given: The input document is an AWS CloudFormation or CloudFormation hook document
#       And: The input document contains at least one DAX Cluster resource
#       And: 'SSESpecification' has been provided and 'SSESpecification.SSEEnabled' is present and has been set to
#            bool(true)
#      Then: PASS

#
# Constants
#
let DAX_CLUSTER_TYPE = "AWS::DAX::Cluster"
let INPUT_DOCUMENT = this

#
# Assignments
#
let dax_clusters = Resources.*[ Type == %DAX_CLUSTER_TYPE ]

#
# Primary Rules
#
rule dax_cluster_encryption_enabled_check when is_cfn_template(%INPUT_DOCUMENT)
                                               %dax_clusters not empty {
    check(%dax_clusters.Properties)
        <<
        [CT.DAX.PR.1]: Require encryption at rest for all Amazon DynamoDB Accelerator (DAX) clusters
        [FIX]: Provide an 'SSESpecification' configuration with 'SSEEnabled' set to 'true'.
        >>
}

rule dax_cluster_encryption_enabled_check when is_cfn_hook(%INPUT_DOCUMENT, %DAX_CLUSTER_TYPE) {
    check(%INPUT_DOCUMENT.%DAX_CLUSTER_TYPE.resourceProperties)
        <<
        [CT.DAX.PR.1]: Require encryption at rest for all Amazon DynamoDB Accelerator (DAX) clusters
        [FIX]: Provide an 'SSESpecification' configuration with 'SSEEnabled' set to 'true'.
        >>
}

#
# Parameterized Rules
#
rule check(dax_cluster) {
    %dax_cluster {
        # Scenario 2
        SSESpecification exists
        SSESpecification is_struct

        # Scenario 3 and 4
        SSESpecification {
            SSEEnabled exists
            SSEEnabled == 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
}