#
#####################################
##           Gherkin               ##
#####################################
# Rule Identifier:
#    RDS_SNAPSHOT_ENCRYPTED
#
# Description:
#    Checks whether Amazon Relational Database Service (Amazon RDS) DB snapshots are encrypted.
#
#
# 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 StorageEncrypted set to true
# c) FAIL: when all RDS instances have StorageEncrypted set to false
# d) FAIL: when there are RDS instances with StorageEncrypted property is not present
# e) SKIP: when metadata includes the suppression for rule RDS_SNAPSHOT_ENCRYPTED

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


rule RDS_SNAPSHOT_ENCRYPTED when %aws_rds_instances_snapshot_encrypted !empty {
  %aws_rds_instances_snapshot_encrypted.Properties.StorageEncrypted EXISTS
  %aws_rds_instances_snapshot_encrypted.Properties.StorageEncrypted == true
  <<
    Violation: All RDS instances must have snapshots encrypted.
    Fix: Set the StorageEncrypted parameter to true so by default all snapshots are encrypted.
  >>
}