# ###################################
##       Rule Specification        ##
#####################################
# 
# Rule Identifier:
#   cloud_trail_log_file_validation_enabled_check
# 
# Description:
#   This control checks whether log file integrity validation is enabled on an AWS CloudTrail trail.
# 
# Reports on:
#   AWS::CloudTrail::Trail
# 
# Evaluates:
#   AWS CloudFormation, AWS CloudFormation hook
# 
# Rule Parameters:
#   None
# 
# Scenarios:
#   Scenario: 1
#     Given: The input document is an AWS CloudFormation document or CloudFormation hook document
#       And: The input document does not contain any CloudTrail trails
#      Then: SKIP
#   Scenario: 2
#     Given: The input document is an AWS CloudFormation document or CloudFormation hook document
#       And: The input document contains a CloudTrail trail resource
#       And: 'EnableLogFileValidation' is not present
#      Then: FAIL
#   Scenario: 3
#     Given: The input document is an AWS CloudFormation document or CloudFormation hook document
#       And: The input document contains a CloudTrail trail resource
#       And: 'EnableLogFileValidation' is present and and is set to a value other than bool(true)
#      Then: FAIL
#   Scenario: 4
#     Given: The input document is an AWS CloudFormation document or CloudFormation hook document
#       And: The input document contains a CloudTrail trail resource
#       And: 'EnableLogFileValidation' is present and set to bool(true)
#      Then: PASS

#
# Constants
#
let CLOUDTRAIL_TRAIL_TYPE = "AWS::CloudTrail::Trail"
let INPUT_DOCUMENT = this

#
# Assignments
#
let cloudtrail_trails = Resources.*[ Type == %CLOUDTRAIL_TRAIL_TYPE ]

#
# Primary Rules
#
rule cloud_trail_log_file_validation_enabled_check when is_cfn_template(%INPUT_DOCUMENT)
                                                        %cloudtrail_trails not empty {
    check(%cloudtrail_trails.Properties)
        <<
        [CT.CLOUDTRAIL.PR.2]: Require an AWS CloudTrail trail to have log file validation activated
        [FIX]: Set the CloudTrail resource 'EnableLogFileValidation' property to true.
        >>
}

rule cloud_trail_log_file_validation_enabled_check when is_cfn_hook(%INPUT_DOCUMENT, %CLOUDTRAIL_TRAIL_TYPE) {
    check(%INPUT_DOCUMENT.%CLOUDTRAIL_TRAIL_TYPE.resourceProperties)
        <<
        [CT.CLOUDTRAIL.PR.2]: Require an AWS CloudTrail trail to have log file validation activated
        [FIX]: Set the CloudTrail resource 'EnableLogFileValidation' property to true.
        >>
}

#
# Parameterized Rules
#
rule check(cloudtrail_trail){
    %cloudtrail_trail {
        # Scenario 2
        EnableLogFileValidation exists
        # Scenario 3 and 4
        EnableLogFileValidation == true
    }
}

#
# 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
}