Dear Source developers.

I would like to create a mod with Source SDK that allows to connect users only with an individual password and username to my server. This data (u_name; password) are stored in an SQL database. So, in short: players register on my website. They recieve a unique Username and a unique Password. THese records are input to my SQL database. Whenever a player attempts to connect to my server he is asked for the username and the password in texbox fields. After these details are entered the game checks them in the sql database and if they are present the player is allowed to join the server.
Can this be done, and if it can, could you please point me to the right direction on how to go about doing so?

Thank you for your time,