Is it permissible to take a commission from a contracting company in exchange for bringing it a project, without the knowledge of the owner of the engineering consulting office for whom I work? And is this lawful (halal) or unlawful (haram)?

If an engineer works as a broker for a contracting company by bringing in projects, while being employed by a consulting office:

If he pursues this during his working hours, it is not permissible unless with the permission of the office owner or by sharing the commission with him. However, if he pursues this outside of working hours, there is no harm.

If he is assigned by the office to supervise a project, it is not permissible for him to give it to a contracting company in exchange for a commission, due to the suspicion of favoritism and betrayal involved. And if he is an agent for the project owners to bring in a contractor and supervise him, it is not lawful for him to take a commission from the contractor.