class Net::SSH::Transport::Kex::DiffieHellmanGroupExchangeSHA1

def build_signature_buffer(result)
  response = Net::SSH::Buffer.new
  response.write_string data[:client_version_string],
                        data[:server_version_string],
                        data[:client_algorithm_packet],
                        data[:server_algorithm_packet],
                        result[:key_blob]
  response.write_long MINIMUM_BITS,
                      data[:need_bits],
                      MAXIMUM_BITS
  response.write_bignum dh.p, dh.g, dh.pub_key,
                        result[:server_dh_pubkey],
                        result[:shared_secret]
  response
end

def compute_need_bits
  # for Compatibility: OpenSSH requires (need_bits * 2 + 1) length of parameter
  need_bits = data[:need_bytes] * 8 * 2 + 1
  data[:minimum_dh_bits] ||= MINIMUM_BITS
  if need_bits < data[:minimum_dh_bits]
    need_bits = data[:minimum_dh_bits]
  elsif need_bits > MAXIMUM_BITS
    need_bits = MAXIMUM_BITS
  end
  data[:need_bits] = need_bits
  data[:need_bytes] = need_bits / 8
end

def get_message_types
  [KEXDH_GEX_INIT, KEXDH_GEX_REPLY]
end

def get_parameters
  compute_need_bits
  # request the DH key parameters for the given number of bits.
  buffer = Net::SSH::Buffer.from(:byte, KEXDH_GEX_REQUEST, :long, data[:minimum_dh_bits],
                                 :long, data[:need_bits], :long, MAXIMUM_BITS)
  connection.send_message(buffer)
  buffer = connection.next_message
  raise Net::SSH::Exception, "expected KEXDH_GEX_GROUP, got #{buffer.type}" unless buffer.type == KEXDH_GEX_GROUP
  p = buffer.read_bignum
  g = buffer.read_bignum
  [p, g]
end