setuid(2) - NetBSD Manual Pages

SETUID(2)                 NetBSD Programmer's Manual                 SETUID(2)


NAME

     setuid, seteuid, setgid, setegid - set user and group ID


SYNOPSIS

     #include <sys/types.h>
     #include <unistd.h>

     int
     setuid(uid_t uid);

     int
     seteuid(uid_t euid);

     int
     setgid(gid_t gid);

     int
     setegid(gid_t egid);


DESCRIPTION

     The setuid() function sets the real and effective user IDs and the saved
     set-user-ID of the current process to the specified value.  The setuid()
     function is permitted if the specified ID is equal to the real user ID of
     the process, or if the effective user ID is that of the super user.

     The setgid() function sets the real and effective group IDs and the saved
     set-group-ID of the current process to the specified value.  The setgid()
     function is permitted if the specified ID is equal to the real group ID
     of the process, or if the effective user ID is that of the super user.

     The seteuid() function (setegid()) sets the effective user ID (group ID)
     of the current process.  The effective user ID may be set to the value of
     the real user ID or the saved set-user-ID (see intro(2) and execve(2));
     in this way, the effective user ID of a set-user-ID executable may be
     toggled by switching to the real user ID, then re-enabled by reverting to
     the set-user-ID value.  Similarly, the effective group ID may be set to
     the value of the real group ID or the saved set-user-ID.


RETURN VALUES

     Upon success, these functions return 0; otherwise -1 is returned.

     If the user is not the super user, or the uid specified is not the real,
     effective ID, or saved ID, these functions return -1.


SEE ALSO

     getuid(2), getgid(2)


STANDARDS

     The setuid() and setgid() functions are compliant with the IEEE
     Std1003.1-1990 (``POSIX'') specification with _POSIX_SAVED_IDS not de-
     fined.  We do not implement the _POSIX_SAVED_IDS option as specified in
     the standard because this would make it impossible for a set-user-ID exe-
     cutable owned by a user other than the super-user to permanently revoke
     its privileges.

     The seteuid() and setegid() functions are extensions based on the POSIX
     concept of _POSIX_SAVED_IDS, and have been proposed for a future revision
     of the standard.  They provide the same feature of toggling effective IDs
     as _POSIX_SAVED_IDS, but do so independent of the current effective ID,
     rather than requiring the super-user to permanently revoke its privi-
     leges.

NetBSD 1.4                       June 4, 1993                                1