Is this income permissible if the company takes labor supply contracts for a specific salary, then pays the workers less than what was agreed upon, with the worker's knowledge of that, and if the employer pays bribes to ensure the continuity of his work?

The issue can be summarized in the following scenarios: 1. If the agreement between your company and the second party is to provide workers, and the worker receives 2700 instead of 4000, with the difference going to the company as a commission, then there is no objection to that. 2. If your company brings the workers and agrees with them on 2700, then leases them to the second party for 4000, this is permissible with the workers' consent, and the difference goes to your company. If the worker refuses to work for anyone other than his original hirer unless he receives the difference in wages, then he has the right to this. 3. If the agreement was to give the worker 4000, then the company is not permitted to reduce the wage, because the company acts as an agent for the second party, and an agent is bound by the authorization.

As for the employer paying a bribe: if you do not assist in it by depositing or accounting, then there is no objection for you. However, if you assist in it, then repentance is obligatory, and you should seek another permissible job.