For the system to be secure, the system must assure that only authorized users can log in and that they log in only as they are authorized to log in. Identification is the mechanism by which, via the login name, the system recognizes a user as legitimate for UnixWare. Authentication is the mechanism by which, via the password, the system verifies the identity of a user. Together, these mechanisms are known as Identification and Authentication (I & A).
The algorithm for I&A checks the expiration date associated with the user ID. In addition, you are strongly encouraged to assign unique user logins, rather than permit the use of "group" logins or the sharing of a login by more than one user.
When a user is identified and authenticated by the system, certain information about the user's access to information is also revealed, namely the access attributes of the user. Only if the user's access attributes meet the requirements for accessing an object can the user access the object.
The I & A mechanisms prevent unauthorized users from logging in to your system, and they ensure that users log in only to areas for which they are authorized. These mechanisms supply the ``who'' information to the system so that the system can make decisions about and enforce the ``who can access what'' parts of the security policy. (See ``Discretionary access control (DAC)'' for information on how the system uses this information to supply security.)
The programs that enforce I&A are
The command that lets users find out about other users is
The library routines for managing I&A are
The login(1) program identifies and authenticates users. It asks for a login name and password and validates these and any other inputs given at the login prompt.
Login information is listed in the file /etc/passwd - see passwd(4). Note that group information is given in the file /etc/group, but this information is not relevant to security in terms of identification and authentication.
The login command checks the password entered against the encrypted passwords in the file /etc/shadow - see shadow(4). The passwd file is usually readable by everyone; the shadow password file is readable only by privileged processes.
If a valid login name and its password is entered, login executes the program specified in the passwd file. Typically this is the user's shell or command interpreter, but any command may be executed on login. The administrator controls what gets executed.
The simplest way for an administrator to limit what a user can do is to give that user a restricted program in the /etc/passwd file. Such a program might, for example, prevent the user from starting other programs or creating files. The program might also be a special-purpose application rather than a general command interpreter.