Is it permissible to work in an IT department at a conventional bank?

Assalamu-alaikum, I want to clarify whether doing a job in the Information Technology department at a conventional bank is right or not. Being an IT professional, our duties and responsibilities are only fixing, installing, configuring, and maintaining IT tools like computers, software, ATM machines, and day to day operational engineering activities. As far as financial matters are concerned we have an expense budget to purchase expensive equipments but we do not know the source of these funds; whether they are riba based or profit based. In fact we don’t know the source of our salaries either. My senior in bank has told me that he has verbal permission from Darul Uloom Karachi that an IT department job in a bank is permissible. Please clarify if this is permissible or not according to above stated job responsibilities.