#
#####################################
##           Gherkin               ##
#####################################
# Rule Identifier:
#    DB_INSTANCE_BACKUP_ENABLED
#
# Description:
#    Checks if RDS DB instances have backups enabled.
#
# Reports on:
#    AWS::RDS::DBInstance
#
# Evaluates:
#    AWS CloudFormation
#
# Rule Parameters:
#    NA
#
# Scenarios:
# a) SKIP: when there are no RDS instances present
# b) PASS: when all RDS instances have BackupRetentionPeriod set to a positive number
# c) FAIL: when all RDS instances have BackupRetentionPeriod set to 0
# d) FAIL: when there are RDS instances with BackupRetentionPeriod property is not present
# e) SKIP: when metadata includes the suppression for rule DB_INSTANCE_BACKUP_ENABLED

#
# Select all RDS instance resources from incoming template (payload)
#

let aws_rds_instances_db_instance_backup_enabled = Resources.*[ Type == 'AWS::RDS::DBInstance'
  Metadata.guard.SuppressedRules not exists or
  Metadata.guard.SuppressedRules.* != "DB_INSTANCE_BACKUP_ENABLED"
]


rule DB_INSTANCE_BACKUP_ENABLED when %aws_rds_instances_db_instance_backup_enabled !empty {
  %aws_rds_instances_db_instance_backup_enabled.Properties.BackupRetentionPeriod EXISTS
  %aws_rds_instances_db_instance_backup_enabled.Properties.BackupRetentionPeriod >= 1
  <<
    Violation: All RDS instances must have automated backup enabled.
    Fix: Set the BackupRetentionPeriod to values of 1 to 35 to enable backups.
  >>
}