# ###################################
##       Rule Specification        ##
#####################################
# 
# Rule Identifier:
#   rds_instance_no_default_ports_check
# 
# Description:
#   This control checks whether Amazon Relational Database Service (RDS) database instances are configured for default database port for their specific engine types.
# 
# Reports on:
#   AWS::RDS::DBInstance
# 
# 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 instance 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 instance resource
#       And: 'Engine' is not one of  'mariadb', 'mysql',
#            'oracle-ee', 'oracle-se2', 'oracle-ee-cdb', 'oracle-se2-cdb',
#            'postgres', 'sqlserver-ee', 'sqlserver-se', 'sqlserver-ex', 'sqlserver-web'
#      Then: SKIP
#   Scenario: 3
#     Given: The input document is an AWS CloudFormation or CloudFormation hook document
#       And: The input document contains an RDS DB instance resource
#       And: 'Engine' is one of  'mariadb', 'mysql',
#            'oracle-ee', 'oracle-se2', 'oracle-ee-cdb', 'oracle-se2-cdb',
#            'postgres', 'sqlserver-ee', 'sqlserver-se', 'sqlserver-ex', 'sqlserver-web'
#       And: 'Port' has not been specified
#      Then: FAIL
#   Scenario: 4
#     Given: The input document is an AWS CloudFormation or CloudFormation hook document
#       And: The input document contains an RDS DB instance resource
#       And: 'Engine' is one of  'mariadb', 'mysql',
#            'oracle-ee', 'oracle-se2', 'oracle-ee-cdb', 'oracle-se2-cdb',
#            'postgres', 'sqlserver-ee', 'sqlserver-se', 'sqlserver-ex', 'sqlserver-web'
#       And: 'Port' has been specified
#       And: 'Port' value is default port (includes mysql/mariadb port '3306', sqlserver
#            port '1433', postgres port '5432', and oracle port '1521')
#      Then: FAIL
#   Scenario: 5
#     Given: The input document is an AWS CloudFormation or CloudFormation hook document
#       And: The input document contains an RDS DB instance resource
#       And: 'Engine'  is one of 'mariadb', 'mysql'
#       And: 'Port' has been specified
#       And: 'Port' value is not equal to '3306'
#      Then: PASS
#   Scenario: 6
#     Given: The input document is an AWS CloudFormation or CloudFormation hook document
#       And: The input document contains an RDS DB instance resource
#       And: 'Engine' is 'postgres'
#       And: 'Port' has been specified
#       And: 'Port' value is not equal to '5432'
#      Then: PASS
#   Scenario: 7
#     Given: The input document is an AWS CloudFormation or CloudFormation hook document
#       And: The input document contains an RDS DB instance resource
#       And: 'Engine' is one of 'sqlserver-ee', 'sqlserver-se', 'sqlserver-ex', 'sqlserver-web'
#       And: 'Port' has been specified
#       And: 'Port' value is not equal to '1433'
#      Then: PASS
#   Scenario: 8
#     Given: The input document is an AWS CloudFormation or CloudFormation hook document
#       And: The input document contains an RDS DB instance resource
#       And: 'Engine' is one of 'oracle-ee', 'oracle-se2', 'oracle-ee-cdb', 'oracle-se2-cdb',
#       And: 'Port' has been specified
#       And: 'Port' value is not equal to '1521'
#      Then: PASS

#
# Constants
#
let RDS_DB_INSTANCE_TYPE = "AWS::RDS::DBInstance"
let INPUT_DOCUMENT = this
let ORACLE_ENGINES = [ "oracle-ee", "oracle-se2", "oracle-se1", "oracle-se" ]
let SQLSERVER_ENGINES = [ "sqlserver-ee", "sqlserver-se", "sqlserver-ex", "sqlserver-web" ]
let MYSQL_OR_MARIA_ENGINES = [ "mariadb", "mysql" ]
let POSTGRES_ENGINES = [ "postgres" ]
let MYSQL_MARIA_DEFAULT_PORTS = [3306, "3306"]
let POSTGRES_DEFAULT_PORTS = [5432, "5432"]
let SQL_DEFAULT_PORTS = [1433, "1433"]
let ORACLE_DEFAULT_PORTS = [1521, "1521"]

#
# Assignments
#
let rds_db_instances = Resources.*[ Type == %RDS_DB_INSTANCE_TYPE ]

#
# Primary Rules
#
rule rds_instance_no_default_ports_check when is_cfn_template(%INPUT_DOCUMENT)
                                              %rds_db_instances not empty {
    check(%rds_db_instances.Properties)
        <<
        [CT.RDS.PR.20]: Require an Amazon RDS database instance not to use a database engine default port
        [FIX]: Set a value for 'Port' that is different than the default value for the Amazon RDS DB instance engine type.
        >>
}

rule rds_instance_no_default_ports_check when is_cfn_hook(%INPUT_DOCUMENT, %RDS_DB_INSTANCE_TYPE) {
    check(%INPUT_DOCUMENT.%RDS_DB_INSTANCE_TYPE.resourceProperties)
        <<
        [CT.RDS.PR.20]: Require an Amazon RDS database instance not to use a database engine default port
        [FIX]: Set a value for 'Port' that is different than the default value for the Amazon RDS DB instance engine type.
        >>
}

#
# Parameterized Rules
#
rule check(rds_db_instance) {
    # Scenario: 4 and 5
    %rds_db_instance[ filter_engine(this, %MYSQL_OR_MARIA_ENGINES) ] {
        check_port(Port, %MYSQL_MARIA_DEFAULT_PORTS)
    }
    # Scenario: 4 and 6
    %rds_db_instance[ filter_engine(this, %POSTGRES_ENGINES) ] {
        check_port(Port, %POSTGRES_DEFAULT_PORTS)
    }
    # Scenario: 4 and 7
    %rds_db_instance[ filter_engine(this, %SQLSERVER_ENGINES) ] {
        check_port(Port, %SQL_DEFAULT_PORTS)
    }
    # Scenario: 4 and 8
    %rds_db_instance[ filter_engine(this, %ORACLE_ENGINES) ] {
        check_port(Port, %ORACLE_DEFAULT_PORTS)
    }
}

rule filter_engine(db_properties, engine) {
    %db_properties {
        # Scenario: 2
        Engine exists
        Engine is_string
        Engine in %engine
    }
}

rule check_port(port, default_ports) {
    # Scenario: 3
    %port exists
    %port not in %default_ports
}

#
# 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
}