module Nexpose
  # This class represents each of the /NexposeReport[@version='1.0']/VulnerabilityDefinitions/vulnerability
  # elements in the Nexpose Full XML document.
  #
  # It provides a convenient way to access the information scattered all over
  # the XML in attributes and nested tags.
  #
  # Instead of providing separate methods for each supported property we rely
  # on Ruby's #method_missing to do most of the work.
  class Vulnerability
    SSL_CIPHER_VULN_IDS = %w[ssl-anon-ciphers ssl-des-ciphers ssl-3des-ciphers ssl-export-ciphers ssl-null-ciphers ssl-only-weak-ciphers ssl-static-key-ciphers rc4-cve-2013-2566 ssl-cve-2016-2183-sweet32 tls-dhe-export-ciphers-cve-2015-4000].freeze

    # Accepts an XML node from Nokogiri::XML.
    def initialize(xml_node)
      @xml = xml_node
    end

    # List of supported tags. They can be attributes, simple descendans or
    # collections (e.g. <references/>, <tags/>)
    def supported_tags
      [
        # attributes
        :nexpose_id, :title, :severity, :pci_severity, :cvss_score, :cvss_vector,
        :published, :added, :modified,

        # simple tags
        :description, :solution,

        # multiple tags
        :references, :tags,

        # evidence tag
        :details
      ]
    end


    # This allows external callers (and specs) to check for implemented
    # properties
    def respond_to?(method, include_private=false)
      return true if supported_tags.include?(method.to_sym)
      super
    end

    # This method is invoked by Ruby when a method that is not defined in this
    # instance is called.
    #
    # In our case we inspect the @method@ parameter and try to find the
    # attribute, simple descendent or collection that it maps to in the XML
    # tree.
    def method_missing(method, *args)

      # We could remove this check and return nil for any non-recognized tag.
      # The problem would be that it would make tricky to debug problems with
      # typos. For instance: <>.potr would return nil instead of raising an
      # exception
      unless supported_tags.include?(method)
        super
        return
      end

      # First we try the attributes. In Ruby we use snake_case, but in XML
      # CamelCase is used for some attributes
      translations_table = {
        :nexpose_id => 'id',
        :pci_severity => 'pciSeverity',
        :cvss_score => 'cvssScore',
        :cvss_vector =>'cvssVector'
      }

      method_name = translations_table.fetch(method, method.to_s)
      return @xml.attributes[method_name].value if @xml.attributes.key?(method_name)

      # Then we try simple children tags: description, solution
      tag = @xml.xpath("./#{method_name}/ContainerBlockElement").first
      # Then we try the tags with nested content
      nest = @xml.xpath("./#{method_name}").first

      # We need to clean up tags that have HTML content in them
      if tags_with_html_content.include?(method)
        result = cleanup_html(tag)
        result = add_bc_to_ssl_cipher_list(result) if SSL_CIPHER_VULN_IDS.include?(@xml.attributes['id'].value)
        return result
      # And we need to clean up the tags with nested content in them
      elsif tags_with_nested_content.include?(method)
        return cleanup_nested(nest)
      else
        return tag
      end

      # Handle evidence creation
      if method_name == 'details'
        vuln_id = @xml.attributes['id'].value

        return @xml.xpath("//test[@id='#{vuln_id}']/Paragraph").
          text.split("\n").
          collect(&:strip).
          reject{|line| line.empty?}.join("\n")
      end

      nil
    end

    private

    def add_bc_to_ssl_cipher_list(source)
      result = source.to_s
      result.gsub!(/\n(.*?)!(.*?)/){"\nbc. #{ $1 }!#{ $2 }\n"}
      result
    end

    def cleanup_html(source)
      result = source.to_s
      result.gsub!(/<ContainerBlockElement>(.*?)<\/ContainerBlockElement>/m){|m| "#{ $1 }"}
      result.gsub!(/<Paragraph preformat=\"true\">(\s*)<Paragraph preformat=\"true\">(.*?)<\/Paragraph>(\s*)<\/Paragraph>/mi){|m| "\nbc. #{ $2 }\n\n"}
      result.gsub!(/<Paragraph preformat=\"true\">(.*?)<\/Paragraph>/mi){|m| "\nbc. #{ $1 }\n\n"}
      result.gsub!(/<Paragraph>(.*?)<\/Paragraph>/m){|m| "#{ $1 }\n"}
      result.gsub!(/<Paragraph>|<\/Paragraph>/, '')
      result.gsub!(/<UnorderedList(.*?)>(.*?)<\/UnorderedList>/m){|m| "#{ $2 }"}
      result.gsub!(/<OrderedList(.*?)>(.*?)<\/OrderedList>/m){|m| "#{ $2 }"}
      result.gsub!(/<ListItem>|<\/ListItem>/, '')
      result.gsub!(/          /, '')
      result.gsub!(/   /, '')
      result.gsub!(/\t\t/, '')
      result.gsub!(/<URLLink(.*)LinkURL=\"(.*?)\"(.*?)>(.*?)<\/URLLink>/im) { "\"#{$4.strip}\":#{$2.strip} " }
      result.gsub!(/<URLLink LinkTitle=\"(.*?)\"(.*?)LinkURL=\"(.*?)\"\/>/i) { "\"#{$1.strip}\":#{$3.strip} " }
      result.gsub!(/<URLLink LinkURL=\"(.*?)\"(.*?)LinkTitle=\"(.*?)\"\/>/i) { "\"#{$3.strip}\":#{$1.strip} " }
      result.gsub!(/&gt;/, '>')
      result.gsub!(/&lt;/, '<')
      result
    end

    def cleanup_nested(source)
      result = source.to_s
      result.gsub!(/<references>/, '')
      result.gsub!(/<\/references>/, '')
      result.gsub!(/<reference source=\"(.*?)\">(.*?)<\/reference>/i) {"#{$1.strip}: #{$2.strip}\n"}
      result.gsub!(/<tags>/, '')
      result.gsub!(/<\/tags>/, '')
      result.gsub!(/<tag>(.*?)<\/tag>/) {"#{$1}\n"}
      result.gsub!(/        /, '')
      result
    end

    def tags_with_html_content
      [:description, :solution]
    end

    def tags_with_nested_content
      [:references, :tags]
    end

  end
end