SETUID(2) System Calls SETUID(2)
NAME
setuid, setegid, seteuid, setgid - set user and group IDs
SYNOPSIS
#include <sys/types.h>
#include <unistd.h>
int setuid(
uid_t uid);
int setgid(
gid_t gid);
int seteuid(
uid_t euid);
int setegid(
gid_t egid);
DESCRIPTION
The
setuid() function sets the real user ID, effective user ID, and
saved user ID of the calling process. The
setgid() function sets the
real group ID, effective group ID, and saved group ID of the calling
process. The
setegid() and
seteuid() functions set the effective
group and user IDs respectively for the calling process. See
Intro(2) for more information on real, effective, and saved user and group
IDs.
At login time, the real user ID, effective user ID, and saved user ID
of the login process are set to the login ID of the user responsible
for the creation of the process. The same is true for the real,
effective, and saved group IDs; they are set to the group ID of the
user responsible for the creation of the process.
When a process calls one of the
exec(2) family of functions to
execute a file (program), the user and/or group identifiers
associated with the process can change. If the file executed is a
set-user-ID file, the effective and saved user IDs of the process are
set to the owner of the file executed. If the file executed is a set-
group-ID file, the effective and saved group IDs of the process are
set to the group of the file executed. If the file executed is not a
set-user-ID or set-group-ID file, the effective user
ID, saved user
ID, effective group ID, and saved group ID are not changed.
If the {
PRIV_PROC_SETID} privilege is asserted in the effective set
of the process calling
setuid(), the real, effective, and saved user
IDs are set to the
uid argument. If the
uid argument is 0 and none
of the saved, effective or real UID is 0, additional restrictions
apply. See
privileges(7).
If the {
PRIV_PROC_SETID} privilege is not asserted in the effective
set, but
uid is either the real user ID or the saved user ID of the
calling process, the effective user ID is set to
uid.
If the {
PRIV_PROC_SETID} privilege is asserted in the effective set
of the process calling
setgid(), the real, effective, and saved group
IDs are set to the
gid argument.
If the {
PRIV_PROC_SETID} privilege is not asserted in the effective
set, but
gid is either the real group ID or the saved group ID of the
calling process, the effective group ID is set to
gid.
RETURN VALUES
Upon successful completion,
0 is returned. Otherwise,
-1 is returned
and
errno is set to indicate the error.
ERRORS
The
setuid() and
setgid() functions will fail if:
EINVAL The value of
uid or
gid is out of range.
EPERM For
setuid() and
seteuid(), the {
PRIV_PROC_SETID} privilege
is not asserted in the effective set of the calling process
and the
uid argument does not match either the real or
saved user IDs, or an attempt is made to change to UID 0
and none of the existing UIDs is 0, in which case
additional privileges are required.
For
setgid() and
setegid(), the {
PRIV_PROC_SETID} privilege
is not asserted in the effective set and the
gid argument
does not match either the real or saved group IDs.
ATTRIBUTES
See
attributes(7) for descriptions of the following attributes:
+--------------------+-------------------+
| ATTRIBUTE TYPE | ATTRIBUTE VALUE |
+--------------------+-------------------+
|Interface Stability | Standard |
+--------------------+-------------------+
|MT-Level | Async-Signal-Safe |
+--------------------+-------------------+
SEE ALSO
Intro(2),
exec(2),
getgroups(2),
getuid(2),
stat.h(3HEAD),
attributes(7),
privileges(7),
standards(7) January 20, 2003 SETUID(2)
