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NAME | SYNOPSIS | DESCRIPTION | RETURN VALUE | ERRORS | CONFORMING TO | NOTES | SEE ALSO | COLOPHON |
SETEUID(2) Linux Programmer's Manual SETEUID(2)
seteuid, setegid - set effective user or group ID
#include <sys/types.h>
#include <unistd.h>
int seteuid(uid_t euid);
int setegid(gid_t egid);
Feature Test Macro Requirements for glibc (see feature_test_macros(7)):
seteuid(), setegid():
_POSIX_C_SOURCE >= 200112L
|| /* Glibc versions <= 2.19: */ _BSD_SOURCE
seteuid() sets the effective user ID of the calling process.
Unprivileged processes may only set the effective user ID to the real
user ID, the effective user ID or the saved set-user-ID.
Precisely the same holds for setegid() with "group" instead of
"user".
On success, zero is returned. On error, -1 is returned, and errno is
set appropriately.
Note: there are cases where seteuid() can fail even when the caller
is UID 0; it is a grave security error to omit checking for a failure
return from seteuid().
EINVAL The target user or group ID is not valid in this user
namespace.
EPERM In the case of seteuid(): the calling process is not
privileged (does not have the CAP_SETUID capability in its
user namespace) and euid does not match the current real user
ID, current effective user ID, or current saved set-user-ID.
In the case of setegid(): the calling process is not
privileged (does not have the CAP_SETGID capability in its
user namespace) and egid does not match the current real group
ID, current effective group ID, or current saved set-group-ID.
POSIX.1-2001, POSIX.1-2008, 4.3BSD.
Setting the effective user (group) ID to the saved set-user-ID (saved
set-group-ID) is possible since Linux 1.1.37 (1.1.38). On an
arbitrary system one should check _POSIX_SAVED_IDS.
Under glibc 2.0 seteuid(euid) is equivalent to setreuid(-1, euid) and
hence may change the saved set-user-ID. Under glibc 2.1 and later it
is equivalent to setresuid(-1, euid, -1) and hence does not change
the saved set-user-ID. Analogous remarks hold for setegid(), with
the difference that the change in implementation from setregid(-1,
egid) to setresgid(-1, egid, -1) occurred in glibc 2.2 or 2.3
(depending on the hardware architecture).
According to POSIX.1, seteuid() (setegid()) need not permit euid
(egid) to be the same value as the current effective user (group) ID,
and some implementations do not permit this.
C library/kernel differences
On Linux, seteuid() and setegid() are implemented as library
functions that call, respectively, setreuid(2) and setregid(2).
geteuid(2), setresuid(2), setreuid(2), setuid(2), capabilities(7),
credentials(7), user_namespaces(7)
This page is part of release 4.12 of the Linux man-pages project. A
description of the project, information about reporting bugs, and the
latest version of this page, can be found at
https://www.kernel.org/doc/man-pages/.
Linux 2016-10-08 SETEUID(2)
Pages that refer to this page: pmdaproc(1), setgid(2), setreuid(2), setuid(2), proc(5), credentials(7), nptl(7), pthreads(7)