Is it permissible for an employee to purchase whatever he wishes from the shop, based on the general permission of its owner, without any specification of the type or value of the purchases?

If the shop owner permits an employee to take items without payment, and does not specify their quantity or type, then reference should be made to custom (urf). It is not permissible for the employee to exploit this permission by unjustly depleting the wealth. Rather, the employee should ask the owner about his intention or act according to what is customarily accepted.