#
#####################################
##           Gherkin               ##
#####################################
# Rule Identifier:
#   OPENSEARCH_AUDIT_LOGGING_ENABLED
#
# Description:
#   OpenSearchService domains are are configured to send audit logs to Amazon CloudWatch Logs
#
# Reports on:
#   AWS::OpenSearchService::Domain
#
# Evaluates:
#   AWS CloudFormation
#
# Rule Parameters:
#   NA
#
# Scenarios:
# a) SKIP: when there are no OpenSearchService Domain Resources 
# b) SKIP: when metadata has rule suppression for OPENSEARCH_AUDIT_LOGGING_ENABLED
# c) FAIL: when OpenSearchService Domain Resources are missing LogPublishingOptions.AUDIT_LOGS.Enabled or LogPublishingOptions.AUDIT_LOGS.CloudWatchLogsLogGroupArn
# d) FAIL: when OpenSearchService Domain Resources have LogPublishingOptions.AUDIT_LOGS.Enabled set to a value other than true 
# e) FAIL: when OpenSearchService Domain Resources have LogPublishingOptions.AUDIT_LOGS.CloudWatchLogsLogGroupArn set to a value other than a string or struct  
# f) PASS: when OpenSearchService Domain Resources have LogPublishingOptions.AUDIT_LOGS.Enabled set to true and 
#          LogPublishingOptions.AUDIT_LOGS.CloudWatchLogsLogGroupArn set to a string or struct value  

#
# Select all OpenSearchService domains from incoming template
#
let opensearch_audit_logging_enabled = Resources.*[ Type == "AWS::OpenSearchService::Domain"
  Metadata.guard.SuppressedRules not exists or
  Metadata.guard.SuppressedRules.* != "OPENSEARCH_AUDIT_LOGGING_ENABLED"
]

rule OPENSEARCH_AUDIT_LOGGING_ENABLED when %opensearch_audit_logging_enabled !empty {
    %opensearch_audit_logging_enabled.Properties { 
        LogPublishingOptions exists
        LogPublishingOptions is_struct

        LogPublishingOptions {
            AUDIT_LOGS exists
            AUDIT_LOGS is_struct

            AUDIT_LOGS {
                Enabled exists
                Enabled == true
                    <<
                        Violation: OpenSearchService domains are are configured to send audit logs to Amazon CloudWatch Logs
                        Fix: In LogPublishingOptions.AUDIT_LOGS, set Enabled to true and CloudWatchLogsLogGroupArn to the ARN of a Amazon CloudWatch Logs log group.
                    >>
                CloudWatchLogsLogGroupArn exists
                CloudWatchLogsLogGroupArn is_string or
                CloudWatchLogsLogGroupArn is_struct
                    <<
                        Violation: OpenSearchService domains are are configured to send audit logs to Amazon CloudWatch Logs
                        Fix: In LogPublishingOptions.AUDIT_LOGS, set Enabled to true and CloudWatchLogsLogGroupArn to the ARN of a Amazon CloudWatch Logs log group.
                    >>
            }
        }
    }
}