# ###################################
##       Rule Specification        ##
#####################################
# 
# Rule Identifier:
#   s3_bucket_acl_prohibited_check
# 
# Description:
#   This control checks whether your Amazon Simple Storage Service (Amazon S3) bucket allows user permissions through access control lists.
# 
# Reports on:
#   AWS::S3::Bucket
# 
# Evaluates:
#   AWS CloudFormation, AWS CloudFormation hook
# 
# Rule Parameters:
#   None
# 
# Scenarios:
#   Scenario: 1
#     Given: The input document is an AWS CloudFormation or CloudFormation hook document
#       And: The input document does not contain any Amazon S3 bucket resources
#      Then: SKIP
#   Scenario: 2
#     Given: The input document is an AWS CloudFormation or CloudFormation hook document
#       And: The input document contains an Amazon S3 bucket resource
#       And: 'AccessControl' has been provided on the S3 bucket resource
#      Then: FAIL
#   Scenario: 3
#     Given: The input document is an AWS CloudFormation or CloudFormation hook document
#       And: The input document contains an Amazon S3 bucket resource
#       And: 'AccessControl' has not been provided on the S3 bucket resource
#      Then: PASS

#
# Constants
#
let S3_BUCKET_TYPE = "AWS::S3::Bucket"
let INPUT_DOCUMENT = this

#
# Assignments
#
let s3_buckets = Resources.*[ Type == %S3_BUCKET_TYPE ]

#
# Primary Rules
#
rule s3_bucket_acl_prohibited_check when is_cfn_template(%INPUT_DOCUMENT)
                                         %s3_buckets not empty {
    check(%s3_buckets.Properties)
        <<
        [CT.S3.PR.5]: Require that an Amazon S3 bucket does not manage user access with an access control list (ACL)
        [FIX]: Manage access to Amazon S3 buckets with bucket resource policies and IAM identity policies instead.
        >>
}

rule s3_bucket_acl_prohibited_check when is_cfn_hook(%INPUT_DOCUMENT, %S3_BUCKET_TYPE) {
    check(this.%S3_BUCKET_TYPE.resourceProperties)
        <<
        [CT.S3.PR.5]: Require that an Amazon S3 bucket does not manage user access with an access control list (ACL)
        [FIX]: Manage access to Amazon S3 buckets with bucket resource policies and IAM identity policies instead.
        >>
}

#
# Parameterized Rules
#
rule check(s3_bucket) {
    %s3_bucket {
       # Scenario 2 and 3
       AccessControl not exists
    }
}

#
# 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
}