#
# Copyright (c) 2006-2024 Wade Alcorn - wade@bindshell.net
# Browser Exploitation Framework (BeEF) - https://beefproject.com
# See the file 'doc/COPYING' for copying permission
#
module BeEF
  module Extension
    module Dns
      # This class handles the routing of RESTful API requests that query BeEF's DNS server
      class DnsRest < BeEF::Core::Router::Router
        # Filters out bad requests before performing any routing
        before do
          @dns ||= BeEF::Extension::Dns::Server.instance
          config = BeEF::Core::Configuration.instance

          # Require a valid API token from a valid IP address
          halt 401 unless params[:token] == config.get('beef.api_token')
          halt 403 unless BeEF::Core::Rest.permitted_source?(request.ip)

          headers 'Content-Type' => 'application/json; charset=UTF-8',
                  'Pragma' => 'no-cache',
                  'Cache-Control' => 'no-cache',
                  'Expires' => '0'
        end

        # Returns the entire current DNS ruleset
        get '/ruleset' do
          ruleset = @dns.get_ruleset
          count = ruleset.length

          result = {}
          result[:count] = count
          result[:ruleset] = ruleset
          result.to_json
        rescue StandardError => e
          print_error "Internal error while retrieving DNS ruleset (#{e.message})"
          halt 500
        end

        # Returns a specific rule given its id
        get '/rule/:id' do
          id = params[:id]

          rule = @dns.get_rule(id)
          raise InvalidParamError, 'id' if rule.nil?

          halt 404 if rule.empty?

          rule.to_json
        rescue InvalidParamError => e
          print_error e.message
          halt 400
        rescue StandardError => e
          print_error "Internal error while retrieving DNS rule with id #{id} (#{e.message})"
          halt 500
        end

        # Adds a new DNS rule
        post '/rule' do
          body = JSON.parse(request.body.read)

          pattern = body['pattern']
          resource = body['resource']
          response = body['response']

          # Validate required JSON keys
          raise InvalidJsonError, 'Empty "pattern" key passed to endpoint /api/dns/rule' if pattern.nil? || pattern.eql?('')
          raise InvalidJsonError, 'Invalid "resource" key passed to endpoint /api/dns/rule' if resource !~ /\A[A-Z]+\Z/
          raise InvalidJsonError, 'Non-array "response" key passed to endpoint /api/dns/rule' unless response.is_a?(Array)
          raise InvalidJsonError, 'Empty "response" array passed to endpoint /api/dns/rule' if response.empty?

          # Validate resource
          case resource
          when 'A'
            dns_resource = Resolv::DNS::Resource::IN::A
          when 'AAAA'
            dns_resource = Resolv::DNS::Resource::IN::AAAA
          when 'CNAME'
            dns_resource = Resolv::DNS::Resource::IN::CNAME
          when 'HINFO'
            dns_resource = Resolv::DNS::Resource::IN::HINFO
          when 'MINFO'
            dns_resource = Resolv::DNS::Resource::IN::MINFO
          when 'MX'
            dns_resource = Resolv::DNS::Resource::IN::MX
          when 'NS'
            dns_resource = Resolv::DNS::Resource::IN::NS
          when 'PTR'
            dns_resource = Resolv::DNS::Resource::IN::PTR
          when 'SOA'
            dns_resource = Resolv::DNS::Resource::IN::SOA
          when 'TXT'
            dns_resource = Resolv::DNS::Resource::IN::TXT
          when 'WKS'
            dns_resource = Resolv::DNS::Resource::IN::WKS
          else
            raise InvalidJsonError, 'Invalid "resource" key passed to endpoint /api/dns/rule'
          end

          # Add rule
          id = @dns.add_rule(
            pattern: pattern,
            resource: dns_resource,
            response: response
          )

          # Return result
          result = {}
          result['success'] = true
          result['id'] = id
          result.to_json
        rescue InvalidJsonError => e
          print_error e.message
          halt 400
        rescue StandardError => e
          print_error "Internal error while adding DNS rule (#{e.message})"
          halt 500
        end

        # Removes a rule given its id
        delete '/rule/:id' do
          id = params[:id]

          removed = @dns.remove_rule!(id)
          raise InvalidParamError, 'id' if removed.nil?

          result = {}
          result['success'] = removed
          result.to_json
        rescue InvalidParamError => e
          print_error e.message
          halt 400
        rescue StandardError => e
          print_error "Internal error while removing DNS rule with id #{id} (#{e.message})"
          halt 500
        end

        # Raised when invalid JSON input is passed to an /api/dns handler.
        class InvalidJsonError < StandardError
          DEFAULT_MESSAGE = 'Invalid JSON input passed to /api/dns handler'

          def initialize(message = nil)
            super(message || DEFAULT_MESSAGE)
          end
        end

        # Raised when an invalid named parameter is passed to an /api/dns handler.
        class InvalidParamError < StandardError
          DEFAULT_MESSAGE = 'Invalid parameter passed to /api/dns handler'

          def initialize(message = nil)
            str = 'Invalid "%s" parameter passed to /api/dns handler'
            message = format str, message unless message.nil?
            super(message)
          end
        end
      end
    end
  end
end