Can you secure the database connections file and still have the connections public for use?

Is there an ability to secure the database connections that are for public use so users may access them, but not have the option to change the password? We are in the process of securing all access points in our environment. I would like to have the ability to allow users to use the connections, be able to read and write to the database, but they would not be able to have access to the credentials of the database.