[COLUG] How Does Linux Security Work?

[Brett Stauffer]

On Thu, 2007-08-02 at 20:15 -0400, Brian Miller wrote:

> If you really want all the gory details, you could look at the source code 
> for "su" and see what calls that program makes, since the whole purpose 
> of "su" is to assume the user ID and permissions of another user.

It's really not all that gory.  Gaining privileges of another user
requires a setuid() system call.  The "guts" of the "su" command is
here:

          if (setuid (pw->pw_uid))
            error (EXIT_FAIL, errno, _("cannot set user id"));
        
The remainder of the code simply ensures that you have permission to
make this system call.

Apart from validating permission in a different manner, "sudo" probably
operates in a similar fashion.


--brett