SETEUID
Section: Linux Programmer's Manual (2)
Updated: 2014-08-19
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NAME
seteuid, setegid - set effective user or group ID
SYNOPSIS
#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():
-
_BSD_SOURCE || _POSIX_C_SOURCE >= 200112L || _XOPEN_SOURCE >= 600
DESCRIPTION
seteuid()
sets the effective user ID of the calling process.
Unprivileged user 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".
RETURN VALUE
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().
ERRORS
- EPERM
-
The calling process is not privileged (Linux: does not have the
CAP_SETUID
capability in the case of
seteuid(),
or the
CAP_SETGID
capability in the case of
setegid())
and
euid
(respectively,
egid)
is not the real user (group) ID, the effective user (group) ID,
or the saved set-user-ID (saved set-group-ID).
CONFORMING TO
4.3BSD, POSIX.1-2001.
NOTES
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 ABI differences
On Linux,
seteuid()
and
setegid()
are implemented as library functions that call, respectively,
setreuid(2)
and
setresgid(2).
SEE ALSO
geteuid(2),
setresuid(2),
setreuid(2),
setuid(2),
capabilities(7),
credentials(7)
Index
- NAME
-
- SYNOPSIS
-
- DESCRIPTION
-
- RETURN VALUE
-
- ERRORS
-
- CONFORMING TO
-
- NOTES
-
- C library/kernel ABI differences
-
- SEE ALSO
-
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Time: 02:54:47 GMT, September 18, 2014