# ###################################
##       Rule Specification        ##
#####################################
# 
# Rule Identifier:
#   ec2_launch_template_token_hop_limit_check
# 
# Description:
#   This control checks whether an Amazon EC2 launch template has a metadata token hop limit set to '1'.
# 
# Reports on:
#   AWS::EC2::LaunchTemplate
# 
# 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 EC2 launch template resources
#       Then: SKIP
#   Scenario: 2
#      Given: The input document is an AWS CloudFormation or CloudFormation hook document
#        And: The input document contains an EC2 launch template resource
#        And: 'LaunchTemplateData.MetadataOptions' has been provided
#        And: 'LaunchTemplateData.MetadataOptions.HttpEndpoint' has been provided and is equal to 'disabled'
#       Then: SKIP
#   Scenario: 3
#      Given: The input document is an AWS CloudFormation or CloudFormation hook document
#        And: The input document contains an EC2 launch template resource
#        And: 'LaunchTemplateData.MetadataOptions' has been provided
#        And: 'LaunchTemplateData.MetadataOptions.HttpEndpoint' has not been provided or has been provided and is
#             equal to 'enabled'
#        And: 'LaunchTemplateData.MetadataOptions.HttpPutResponseHopLimit' has been provided and is not equal to
#             an integer of 1.
#       Then: FAIL
#   Scenario: 4
#      Given: The input document is an AWS CloudFormation or CloudFormation hook document
#        And: The input document contains an EC2 launch template resource
#        And: 'LaunchTemplateData.MetadataOptions' has not been provided
#       Then: PASS
#   Scenario: 5
#      Given: The input document is an AWS CloudFormation or CloudFormation hook document
#        And: The input document contains an EC2 launch template resource
#        And: 'LaunchTemplateData.MetadataOptions' has been provided
#        And: 'LaunchTemplateData.MetadataOptions.HttpEndpoint' has not been provided or has been provided and is
#             equal to 'enabled'
#        And: 'LaunchTemplateData.MetadataOptions.HttpPutResponseHopLimit' has not been provided
#       Then: PASS
#   Scenario: 6
#      Given: The input document is an AWS CloudFormation or CloudFormation hook document
#        And: The input document contains an EC2 launch template resource
#        And: 'LaunchTemplateData.MetadataOptions' has been provided
#        And: 'LaunchTemplateData.MetadataOptions.HttpEndpoint' has not been provided or has been provided and is
#             equal to 'enabled'
#        And: 'LaunchTemplateData.MetadataOptions.HttpPutResponseHopLimit' has been provided and is equal to an
#             integer of 1.
#       Then: PASS

#
# Constants
#
let EC2_LAUNCH_TEMPLATE_TYPE = "AWS::EC2::LaunchTemplate"
let INPUT_DOCUMENT = this

#
# Assignments
#
let ec2_launch_templates = Resources.*[ Type == %EC2_LAUNCH_TEMPLATE_TYPE ]

#
# Primary Rules
#
rule ec2_launch_template_token_hop_limit_check when is_cfn_template(this)
                                                    %ec2_launch_templates not empty {
    check(%ec2_launch_templates.Properties)
        <<
        [CT.EC2.PR.2]: Require that Amazon EC2 launch templates restrict the token hop limit to a maximum of one
        [FIX]: Within the 'LaunchTemplateData' property, provide a 'MetadataOptions' configuration with the value of 'HttpPutResponseLimit' set to '1', or omit the 'HttpPutResponseLimit' property to adopt the AWS CloudFormation default value of '1'.
        >>
}

rule ec2_launch_template_token_hop_limit_check when is_cfn_hook(%INPUT_DOCUMENT, %EC2_LAUNCH_TEMPLATE_TYPE) {
    check(%INPUT_DOCUMENT.%EC2_LAUNCH_TEMPLATE_TYPE.resourceProperties)
        <<
        [CT.EC2.PR.2]: Require that Amazon EC2 launch templates restrict the token hop limit to a maximum of one
        [FIX]: Within the 'LaunchTemplateData' property, provide a 'MetadataOptions' configuration with the value of 'HttpPutResponseLimit' set to '1', or omit the 'HttpPutResponseLimit' property to adopt the AWS CloudFormation default value of '1'.
        >>
}

#
# Parameterized Rules
#
rule check(ec2_launch_template) {
  %ec2_launch_template[
      # Scenario 2, 3 and 4
      filter_launch_template(this)
  ] {
      # Scenario 5 and 6
      LaunchTemplateData {
          MetadataOptions not exists or
          MetadataOptions {
              HttpPutResponseHopLimit not exists or
              HttpPutResponseHopLimit == 1
          }
      }
  }
}

rule filter_launch_template(ec2_launch_template) {
  %ec2_launch_template {
      LaunchTemplateData exists
      LaunchTemplateData is_struct
      LaunchTemplateData {
          MetadataOptions not exists or
          filter_metadata_options_provided(this)
      }
  }
}

rule filter_metadata_options_provided(options) {
  %options {
      MetadataOptions is_struct
      MetadataOptions {
          HttpEndpoint not exists or
          HttpEndpoint == "enabled"
      }
  }
}

#
# 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
}