Help with user information

I have two things that I need to do in a custom module.  Can you help me with these?

1.  Given a username and password, how can I re-verify that those correspond to a legitimate user.  This is not necessarily the user who is logged in.

2. Given a username, how can I determine the security roles assigned to the user.

First you would want to get the user object with UserController.GetUserByName method.

Then use the UserController.ValidateUser to authenticate a User.  You will see it in the SignIn.ascx control ( or the Login.ascx which is new in DNN 4.6)

For getting all the security Roles of a given User you use the GetUserRoles method of the RoleController.