# ###################################
##       Rule Specification        ##
#####################################
# 
# Rule Identifier:
#   redshift_default_admin_check
# 
# Description:
#   This control checks whether an Amazon Redshift cluster has changed the administrator username from its default value.
# 
# Reports on:
#   AWS::Redshift::Cluster
# 
# 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 Redshift cluster resources
#      Then: SKIP
#   Scenario: 2
#     Given: The input document is an AWS CloudFormation or CloudFormation hook document
#       And: The input document contains a Redshift cluster resource
#       And: 'MasterUsername' has not been specified
#      Then: FAIL
#   Scenario: 3
#     Given: The input document is an AWS CloudFormation or CloudFormation hook document
#       And: The input document contains a Redshift cluster resource
#       And: 'MasterUsername' has been specified
#       And: 'MasterUsername' has been set to 'awsuser'
#      Then: FAIL
#   Scenario: 4
#     Given: The input document is an AWS CloudFormation or CloudFormation hook document
#       And: The input document contains a Redshift cluster resource
#       And: 'MasterUsername' has been specified
#       And: 'MasterUsername' has been set to a value not equal to 'awsuser'
#      Then: PASS

#
# Constants
#
let REDSHIFT_CLUSTER_TYPE = "AWS::Redshift::Cluster"
let INPUT_DOCUMENT = this

#
# Assignments
#
let redshift_clusters = Resources.*[ Type == %REDSHIFT_CLUSTER_TYPE ]

#
# Primary Rules
#
rule redshift_default_admin_check when is_cfn_template(%INPUT_DOCUMENT)
                                       %redshift_clusters not empty  {
    check(%redshift_clusters.Properties)
        <<
        [CT.REDSHIFT.PR.6]: Require an Amazon Redshift cluster to have a unique administrator username
        [FIX]: Set 'MasterUsername' to a value other than 'awsuser'.
        >>
}

rule redshift_default_admin_check when is_cfn_hook(%INPUT_DOCUMENT, %REDSHIFT_CLUSTER_TYPE) {
    check(%INPUT_DOCUMENT.%REDSHIFT_CLUSTER_TYPE.resourceProperties)
        <<
        [CT.REDSHIFT.PR.6]: Require an Amazon Redshift cluster to have a unique administrator username
        [FIX]: Set 'MasterUsername' to a value other than 'awsuser'.
        >>
}

#
# Parameterized Rules
#
rule check(redshift_cluster) {
    %redshift_cluster {
        # Scenario 2
        MasterUsername exists
        check_is_string_and_not_empty(MasterUsername)

        # Scenario 3 & 4
        MasterUsername != "awsuser"
    }
}

#
# Utility Rules
#
rule check_is_string_and_not_empty(value) {
    %value {
        this is_string
        this != /\A\s*\z/
    }
}

rule is_cfn_template(doc) {
    %doc {
        AWSTemplateFormatVersion exists  or
        Resources exists
    }
}

rule is_cfn_hook(doc, RESOURCE_TYPE) {
    %doc.%RESOURCE_TYPE.resourceProperties exists
}