# -*- coding: binary -*-

module Rex
  module Proto
    module Kerberos
      module Model
        module Message
          class KdcRequest < Element
            # @!attribute pvno
            #   @return [Fixnum] The protocol version number
            attr_accessor :pvno
            # @!attribute msg_type
            #   @return [Fixnum] The type of a protocol message
            attr_accessor :msg_type
            # @!attribute pa_data
            #   @return [Array<Rex::Proto::Kerberos::Model::Field::PreAuthData>] Authentication information which may
            #   be needed before credentials can be issued or decrypted
            attr_accessor :pa_data
            # @!attribute req_body
            #   @return [Rex::Proto::Kerberos::Model::Field::KdcRequestBody] The request body
            attr_accessor :req_body

            # Decodes the Rex::Proto::Kerberos::Model::Message::KdcRequest from an input
            #
            # @param input [String, OpenSSL::ASN1::ASN1Data] the input to decode from
            # @return [self] if decoding succeeds
            # @raise [RuntimeError] if decoding doesn't succeed
            def decode(input)
              case input
              when String
                decode_string(input)
              when OpenSSL::ASN1::ASN1Data
                decode_asn1(input)
              else
                raise ::RuntimeError, 'Failed to decode KDC Request, invalid input'
              end

              self
            end

            # Encodes the Rex::Proto::Kerberos::Model::Message::KdcRequest into an ASN.1 String
            #
            # @return [String]
            def encode
              pvno_asn1 = OpenSSL::ASN1::ASN1Data.new([encode_pvno], 1, :CONTEXT_SPECIFIC)
              msg_type_asn1 = OpenSSL::ASN1::ASN1Data.new([encode_msg_type], 2, :CONTEXT_SPECIFIC)
              pa_data_asn1 = OpenSSL::ASN1::ASN1Data.new([encode_pa_data], 3, :CONTEXT_SPECIFIC)
              req_body_asn1 = OpenSSL::ASN1::ASN1Data.new([encode_req_body], 4, :CONTEXT_SPECIFIC)
              seq = OpenSSL::ASN1::Sequence.new([pvno_asn1, msg_type_asn1, pa_data_asn1, req_body_asn1])
              seq_asn1 = OpenSSL::ASN1::ASN1Data.new([seq], msg_type, :APPLICATION)
              seq_asn1.to_der
            end

            private

            # Encodes the etype field
            #
            # @return [OpenSSL::ASN1::Integer]
            def encode_pvno
              bn = OpenSSL::BN.new(pvno)
              int = OpenSSL::ASN1::Integer(bn)

              int
            end

            # Encodes the msg_type field
            #
            # @return [OpenSSL::ASN1::Integer]
            def encode_msg_type
              bn = OpenSSL::BN.new(msg_type)
              int = OpenSSL::ASN1::Integer(bn)

              int
            end

            # Encodes the pa_data field
            #
            # @return [String]
            def encode_pa_data
              elems = []
              pa_data.each do |data|
                elems << data.encode
              end

              OpenSSL::ASN1::Sequence.new(elems)
            end

            # Encodes the req_body field
            #
            # @return [String]
            def encode_req_body
              req_body.encode
            end

            # Decodes a Rex::Proto::Kerberos::Model::Message::KdcRequest from an String
            #
            # @param input [String] the input to decode from
            def decode_string(input)
              asn1 = OpenSSL::ASN1.decode(input)

              decode_asn1(asn1)
            end

            # Decodes a Rex::Proto::Kerberos::Model::Message::KdcRequest
            #
            # @param input [OpenSSL::ASN1::ASN1Data] the input to decode from
            # @raise [RuntimeError] if decoding doesn't succeed
            def decode_asn1(input)
              input.value[0].value.each do |val|
                case val.tag
                when 1
                  self.pvno = decode_asn1_pvno(val)
                when 2
                  self.msg_type = decode_asn1_msg_type(val)
                when 3
                  self.pa_data  = decode_asn1_pa_data(val)
                when 4
                  self.req_body = decode_asn1_req_body(val)
                else
                  raise ::RuntimeError, 'Filed to decode KdcRequest SEQUENCE'
                end
              end
            end

            # Decodes the pvno from an OpenSSL::ASN1::ASN1Data
            #
            # @param input [OpenSSL::ASN1::ASN1Data] the input to decode from
            # @return [Fixnum]
            def decode_asn1_pvno(input)
              input.value[0].value.to_i
            end

            # Decodes the msg_type from an OpenSSL::ASN1::ASN1Data
            #
            # @param input [OpenSSL::ASN1::ASN1Data] the input to decode from
            # @return [Fixnum]
            def decode_asn1_msg_type(input)
              input.value[0].value.to_i
            end

            # Decodes the pa_data from an OpenSSL::ASN1::ASN1Data
            #
            # @param input [OpenSSL::ASN1::ASN1Data] the input to decode from
            # @return [Array<Rex::Proto::Kerberos::Model::Field::PreAuthData>]
            def decode_asn1_pa_data(input)
              pre_auth = []
              input.value[0].value.each do |pre_auth_data|
                pre_auth << Rex::Proto::Kerberos::Model::Field::PreAuthData.decode(pre_auth_data)
              end

              pre_auth
            end

            # Decodes the req_body from an OpenSSL::ASN1::ASN1Data
            #
            # @param input [OpenSSL::ASN1::ASN1Data] the input to decode from
            # @return [Rex::Proto::Kerberos::Model::Field::KdcRequestBody]
            def decode_asn1_req_body(input)
              Rex::Proto::Kerberos::Model::Field::KdcRequestBody.decode(input.value[0])
            end
          end
        end
      end
    end
  end
end