# ###################################
##       Rule Specification        ##
#####################################
# 
# Rule Identifier:
#   api_gw_v1_execution_logging_enabled_check
# 
# Description:
#   This control checks whether all methods in Amazon API Gateway stage have execution logging configured.
# 
# Reports on:
#   AWS::ApiGateway::Stage
# 
# 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 API Gateway stage resources
#      Then: SKIP
#   Scenario: 2
#     Given: The input document is an AWS CloudFormation or CloudFormation hook document
#       And: The input document contains an API Gateway stage resource
#       And: In the stage resource, 'MethodSettings' is not present or is provided and is an empty list.
#      Then: FAIL
#   Scenario: 3
#     Given: The input document is an AWS CloudFormation or CloudFormation hook document
#       And: The input document contains an API Gateway stage resource
#       And: In the stage resource, Execution Logging is not configured for all HTTP Methods and API resources (In
#            'MethodSettings', 'LoggingLevel' is omitted, or not set to 'ERROR' or 'INFO', for 'HttpMethod' of '*' and
#            'ResourcePath' of '/*' )
#      Then: FAIL
#   Scenario: 4
#     Given: The input document is an AWS CloudFormation or CloudFormation hook document
#       And: The input document contains an API Gateway stage resource
#       And: In the stage resource, Execution Logging is configured for all HTTP Methods and API resources (In
#            'MethodSettings', 'LoggingLevel' is set to 'ERROR' or 'INFO', for 'HttpMethod' of '*' and
#            'ResourcePath' of '/*' )
#       And: 'LoggingLevel' has been set to 'OFF' for any other Method Setting
#      Then: FAIL
#   Scenario: 5
#     Given: The input document is an AWS CloudFormation or CloudFormation hook document
#       And: The input document contains an API Gateway stage resource
#       And: In the stage resource, Execution Logging is configured for all HTTP Methods and API resources (In
#            'MethodSettings', 'LoggingLevel' is set to 'ERROR' or 'INFO', for 'HttpMethod' of '*' and
#            'ResourcePath' of '/*' )
#       And: 'LoggingLevel' has not been provided or set to 'ERROR' or 'INFO' for all other Method Settings
#      Then: PASS

#
# Constants
#
let API_GW_STAGE_TYPE = "AWS::ApiGateway::Stage"
let INPUT_DOCUMENT = this
let VALID_LOG_LEVELS = [ "ERROR", "INFO" ]

#
# Assignments
#
let api_gateway_stages = Resources.*[ Type == %API_GW_STAGE_TYPE ]

#
# Primary Rules
#
rule api_gw_v1_execution_logging_enabled_check when is_cfn_template(%INPUT_DOCUMENT)
                                                    %api_gateway_stages not empty {
    check(%api_gateway_stages.Properties)
        <<
        [CT.APIGATEWAY.PR.1]: Require an Amazon API Gateway REST and WebSocket API to have logging activated
        [FIX]: Configure execution logging on Amazon API Gateway stages with a 'MethodSetting' that sets 'LoggingLevel' to 'ERROR' or 'INFO' for all methods ('HttpMethod' of '*' and 'ResourcePath' of '/*'). Ensure that you do not set 'LoggingLevel' to 'OFF' for any method setting.
        >>
}

rule api_gw_v1_execution_logging_enabled_check when is_cfn_hook(%INPUT_DOCUMENT, %API_GW_STAGE_TYPE) {
    check(%INPUT_DOCUMENT.%API_GW_STAGE_TYPE.resourceProperties)
        <<
        [CT.APIGATEWAY.PR.1]: Require an Amazon API Gateway REST and WebSocket API to have logging activated
        [FIX]: Configure execution logging on Amazon API Gateway stages with a 'MethodSetting' that sets 'LoggingLevel' to 'ERROR' or 'INFO' for all methods ('HttpMethod' of '*' and 'ResourcePath' of '/*'). Ensure that you do not set 'LoggingLevel' to 'OFF' for any method setting.
        >>
}

#
# Parameterized Rules
#
rule check(api_gateway_stage) {
    %api_gateway_stage {
        # Scenario 2
        MethodSettings exists
        MethodSettings is_list
        MethodSettings not empty

        # Scenario 3
        # At least one wildcard entry exists with valid logging enabled
        some MethodSettings[*] {
            HttpMethod exists
            ResourcePath exists
            LoggingLevel exists

            HttpMethod == "*"
            ResourcePath == "/*"
            LoggingLevel in %VALID_LOG_LEVELS
        }

        # Scenario 4, 5
        # When other methods explictly set/override logging settings, ensure that logging is not disabled
        MethodSettings[*] {
            when LoggingLevel exists {
                LoggingLevel in %VALID_LOG_LEVELS
            }
        }
    }
}

#
# 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
}