#
#####################################
##           Gherkin               ##
#####################################
# Rule Identifier:
#    RDS_INSTANCE_PUBLIC_ACCESS_CHECK
#
# Description:
#    Checks if an RDS instances has Publicly Accessible not set.
#
# 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 PubliclyAccessible set to true
# c) FAIL: when all RDS instances have PubliclyAccessible set to false
# d) FAIL: when there are RDS instances with PubliclyAccessible property is not present
# e) SKIP: when metadata includes the suppression for rule RDS_INSTANCE_PUBLIC_ACCESS_CHECK

#
# Select all RDS instance resources from incoming template (payload)
#
let aws_rds_instances_not_public = Resources.*[ Type == 'AWS::RDS::DBInstance'
  Metadata.guard.SuppressedRules not exists or
  Metadata.guard.SuppressedRules.* != "RDS_INSTANCE_PUBLIC_ACCESS_CHECK"
]

rule RDS_INSTANCE_PUBLIC_ACCESS_CHECK when %aws_rds_instances_not_public !empty {
  # ALL RDS instances must have PubliclyAccessible set to false
  %aws_rds_instances_not_public.Properties.PubliclyAccessible == false
  <<
    Violation: All RDS instances must not be publicly accessible.
    Fix: Set the PubliclyAccessible to false.
  >>
}