# ###################################
##       Rule Specification        ##
#####################################
# 
# Rule Identifier:
#   rds_cluster_logging_enabled_check
# 
# Description:
#   This control checks whether Amazon RDS database clusters have all available log types enabled for export to Amazon CloudWatch Logs.
# 
# Reports on:
#   AWS::RDS::DBCluster
# 
# 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 RDS DB cluster resources
#      Then: SKIP
#   Scenario: 2
#     Given: The input document is an AWS CloudFormation or CloudFormation hook document
#       And: The input document contains an RDS DB cluster Resource
#       And: 'Engine' is not one of 'aurora', 'aurora-mysql', 'aurora-postgresql', 'mysql' or 'postgres'
#      Then: SKIP
#   Scenario: 3
#     Given: The input document is an AWS CloudFormation or CloudFormation hook document
#       And: The input document contains an RDS DB cluster resource
#       And: 'Engine' is one of 'aurora', 'aurora-mysql', 'aurora-postgresql', 'mysql' or 'postgres'
#       And: 'EnableCloudwatchLogsExports' has not been specified or has been specified as an empty list
#      Then: FAIL
#   Scenario: 4
#     Given: The input document is an AWS CloudFormation or CloudFormation hook document
#       And: The input document contains an RDS DB cluster resource
#       And: 'Engine' is one of 'aurora', 'aurora-mysql', 'aurora-postgresql', 'mysql' or 'postgres'
#       And: 'EnableCloudwatchLogsExports' has been specified and is a non-empty list
#       And: One or more log types in 'EnableCloudwatchLogsExports' are not supported by the specified 'Engine'
#      Then: FAIL
#   Scenario: 5
#     Given: The input document is an AWS CloudFormation or CloudFormation hook document
#       And: The input document contains an RDS DB cluster resource
#       And: 'Engine' is one of 'aurora', 'aurora-mysql', 'aurora-postgresql', 'mysql' or 'postgres'
#       And: 'EnableCloudwatchLogsExports' has been specified and is a non-empty list
#       And: 'EnableCloudwatchLogsExports' does not contain all log types supported by the specified 'Engine'
#      Then: FAIL
#   Scenario: 6
#     Given: The input document is an AWS CloudFormation or CloudFormation hook document
#       And: The input document contains an RDS DB cluster resource
#       And: 'Engine' is one of 'aurora', 'aurora-mysql' or 'mysql'
#       And: 'EnableCloudwatchLogsExports' has been specified as a list with all supported log types
#             for the 'Engine' ('audit', 'error', 'general' and 'slowquery')
#      Then: PASS
#   Scenario: 7
#     Given: The input document is an AWS CloudFormation or CloudFormation hook document
#       And: The input document contains an RDS DB cluster resource
#       And: 'Engine' is 'aurora-postgresql'
#       And: 'EnableCloudwatchLogsExports' has been specified as a list with all supported log types
#             for the 'Engine' ('postgresql')
#      Then: PASS
#   Scenario: 8
#     Given: The input document is an AWS CloudFormation or CloudFormation hook document
#       And: The input document contains an RDS DB cluster resource
#       And: 'Engine' is 'postgres'
#       And: 'EnableCloudwatchLogsExports' has been specified as a list with all supported log types
#             for the 'Engine' ('postgresql', 'upgrade')
#      Then: PASS

#
# Constants
#
let RDS_DB_CLUSTER_TYPE = "AWS::RDS::DBCluster"
let INPUT_DOCUMENT = this

let SUPPORTED_RDS_CLUSTER_ENGINES = [
    "aurora", "aurora-mysql", "aurora-postgresql", "mysql", "postgres"
]

let MYSQL_ENGINE_SUBTYPES = [ "aurora", "aurora-mysql", "mysql" ]
let AURORA_POSTGRES_ENGINE_SUBTYPES = [ "aurora-postgresql" ]
let POSTGRES_ENGINE_SUBTYPES = [ "postgres" ]

let MYSQL_SUPPORTED_LOG_TYPES = [ "audit", "error", "general", "slowquery" ]
let AURORA_POSTGRES_SUPPORTED_LOG_TYPES  = [ "postgresql" ]
let POSTGRES_SUPPORTED_LOG_TYPES = [ "postgresql", "upgrade" ]

#
# Assignments
#
let rds_db_clusters = Resources.*[ Type == %RDS_DB_CLUSTER_TYPE ]

#
# Primary Rules
#
rule rds_cluster_logging_enabled_check when is_cfn_template(%INPUT_DOCUMENT)
                                             %rds_db_clusters not empty {
    check(%rds_db_clusters.Properties)
        <<
        [CT.RDS.PR.25]: Require an Amazon RDS database cluster to have logging configured
        [FIX]: Specify 'EnableCloudwatchLogsExports' with a list of all supported log types for the Amazon RDS database cluster engine.
        >>
}

rule rds_cluster_logging_enabled_check when is_cfn_hook(%INPUT_DOCUMENT, %RDS_DB_CLUSTER_TYPE) {
    check(%INPUT_DOCUMENT.%RDS_DB_CLUSTER_TYPE.resourceProperties)
        <<
        [CT.RDS.PR.25]: Require an Amazon RDS database cluster to have logging configured
        [FIX]: Specify 'EnableCloudwatchLogsExports' with a list of all supported log types for the Amazon RDS database cluster engine.
        >>
}

#
# Parameterized Rules
#
rule check(rds_db_cluster) {
    %rds_db_cluster [
        filter_engine(this)
    ] {
        # Scenario 3
        EnableCloudwatchLogsExports exists
        check_is_list_and_not_empty(EnableCloudwatchLogsExports)

        # Scenario 4 and 6
        when Engine IN %MYSQL_ENGINE_SUBTYPES {
            %MYSQL_SUPPORTED_LOG_TYPES.* IN EnableCloudwatchLogsExports[*]
            EnableCloudwatchLogsExports.* IN %MYSQL_SUPPORTED_LOG_TYPES[*]
        }

        # Scenario 4 and 7
        when Engine IN %AURORA_POSTGRES_ENGINE_SUBTYPES {
            %AURORA_POSTGRES_SUPPORTED_LOG_TYPES.* IN EnableCloudwatchLogsExports[*]
            EnableCloudwatchLogsExports.* IN %AURORA_POSTGRES_SUPPORTED_LOG_TYPES[*]
        }

        # Scenario 4 and 8
        when Engine IN %POSTGRES_ENGINE_SUBTYPES {
            %POSTGRES_SUPPORTED_LOG_TYPES.* in EnableCloudwatchLogsExports[*]
            EnableCloudwatchLogsExports.* IN %POSTGRES_SUPPORTED_LOG_TYPES[*]
        }
    }
}

rule filter_engine(db_properties) {
    %db_properties {
        # Scenario 2
        Engine exists
        Engine in %SUPPORTED_RDS_CLUSTER_ENGINES
    }
}

#
# Utility Rules
#
rule check_is_list_and_not_empty(value) {
    %value {
        this is_list
        this not empty
    }
}

rule is_cfn_template(doc) {
    %doc {
        AWSTemplateFormatVersion exists  or
        Resources exists
    }
}

rule is_cfn_hook(doc, RESOURCE_TYPE) {
    %doc.%RESOURCE_TYPE.resourceProperties exists
}