# ###################################
##       Rule Specification        ##
#####################################
# 
# Rule Identifier:
#   netfw_stateless_rule_group_not_empty_check
# 
# Description:
#   This control checks whether an AWS Network Firewall stateless rule group contains rules.
# 
# Reports on:
#   AWS::NetworkFirewall::RuleGroup
# 
# 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 NetworkFirewall rule group resources
#      Then: SKIP
#   Scenario: 2
#     Given: The input document is an AWS CloudFormation or CloudFormation hook document
#       And: The input document contains a NetworkFirewall rule group resource
#       And: 'Type' is not equal to 'STATELESS'
#      Then: SKIP
#   Scenario: 3
#     Given: The input document is an AWS CloudFormation or CloudFormation hook document
#       And: The input document contains a NetworkFirewall rule group resource
#       And: 'Type' is 'STATELESS'
#       And: 'RuleGroup.RulesSource.StatelessRulesAndCustomActions' has not been provided
#      Then: FAIL
#   Scenario: 4
#     Given: The input document is an AWS CloudFormation or CloudFormation hook document
#       And: The input document contains a NetworkFirewall rule group resource
#       And: 'Type' is 'STATELESS'
#       And: 'RuleGroup.RulesSource.StatelessRulesAndCustomActions' has been provided
#       And: 'StatelessRules' has not been provided within 'StatelessRulesAndCustomActions' or has been provided with
#            an empty list value
#      Then: FAIL
#   Scenario: 5
#     Given: The input document is an AWS CloudFormation or CloudFormation hook document
#       And: The input document contains a NetworkFirewall rule group resource
#       And: 'Type' is 'STATELESS'
#       And: 'RuleGroup.RulesSource.StatelessRulesAndCustomActions' has been provided
#       And: 'StatelessRules' has been provided within 'StatelessRulesAndCustomActions' as a non-empty list value
#      Then: PASS

#
# Constants
#
let NETFW_RULE_GROUP_TYPE = "AWS::NetworkFirewall::RuleGroup"
let INPUT_DOCUMENT = this

#
# Assignments
#
let netfw_rule_group = Resources.*[ Type == %NETFW_RULE_GROUP_TYPE ]

#
# Primary Rules
#
rule netfw_stateless_rule_group_not_empty_check when is_cfn_template(%INPUT_DOCUMENT)
                                               %netfw_rule_group not empty {
    check(%netfw_rule_group.Properties)
        <<
        [CT.NETWORK-FIREWALL.PR.4]: Require any AWS Network Firewall rule group to contain at least one rule
        [FIX]: Provide one or more AWS Network Firewall stateless rules within the 'RuleGroup.RulesSource.StatelessRulesAndCustomActions.StatelessRules' property.
        >>
}

rule netfw_stateless_rule_group_not_empty_check when is_cfn_hook(%INPUT_DOCUMENT, %NETFW_RULE_GROUP_TYPE) {
    check(%INPUT_DOCUMENT.%NETFW_RULE_GROUP_TYPE.resourceProperties)
        <<
        [CT.NETWORK-FIREWALL.PR.4]: Require any AWS Network Firewall rule group to contain at least one rule
        [FIX]: Provide one or more AWS Network Firewall stateless rules within the 'RuleGroup.RulesSource.StatelessRulesAndCustomActions.StatelessRules' property.
        >>
}

#
# Parameterized Rules
#
rule check(netfw_rule_group) {
    %netfw_rule_group[
        # Scenario 2
        Type exists
        Type == "STATELESS"
    ] {
        # Scenario 3
        RuleGroup exists
        RuleGroup is_struct
        RuleGroup {
            RulesSource exists
            RulesSource is_struct
            RulesSource {
                StatelessRulesAndCustomActions exists
                StatelessRulesAndCustomActions is_struct
                StatelessRulesAndCustomActions {
                    # Scenarios 4 and 5
                    StatelessRules exists
                    StatelessRules is_list
                    StatelessRules not empty
                }
            }
        }
    }
}

#
# 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
}