NAME¶
setresuid, setresgid - set real, effective and saved user or group ID
SYNOPSIS¶
#define _GNU_SOURCE /* See
feature_test_macros(7) */
#include <unistd.h>
int setresuid(uid_t ruid, uid_t euid, uid_t
suid);
int setresgid(gid_t rgid, gid_t egid, gid_t
sgid);
DESCRIPTION¶
setresuid() sets the real user ID, the effective user ID, and the saved
set-user-ID of the calling process.
Unprivileged user processes may change the real UID, effective UID, and saved
set-user-ID, each to one of: the current real UID, the current effective UID
or the current saved set-user-ID.
Privileged processes (on Linux, those having the
CAP_SETUID capability)
may set the real UID, effective UID, and saved set-user-ID to arbitrary
values.
If one of the arguments equals -1, the corresponding value is not changed.
Regardless of what changes are made to the real UID, effective UID, and saved
set-user-ID, the filesystem UID is always set to the same value as the
(possibly new) effective UID.
Completely analogously,
setresgid() sets the real GID, effective GID, and
saved set-group-ID of the calling process (and always modifies the filesystem
GID to be the same as the effective GID), with the same restrictions for
unprivileged processes.
RETURN VALUE¶
On success, zero is returned. On error, -1 is returned, and
errno is set
appropriately.
Note: there are cases where
setresuid() can fail even when the
caller is UID 0; it is a grave security error to omit checking for a failure
return from
setresuid().
ERRORS¶
- EAGAIN
- The call would change the caller's real UID (i.e., ruid does not
match the caller's real UID), but there was a temporary failure allocating
the necessary kernel data structures.
- EAGAIN
- ruid does not match the caller's real UID and this call would bring
the number of processes belonging to the real user ID ruid over the
caller's RLIMIT_NPROC resource limit. Since Linux 3.1, this error
case no longer occurs (but robust applications should check for this
error); see the description of EAGAIN in execve(2).
- EINVAL
- One or more of the target user or group IDs is not valid in this user
namespace.
- EPERM
- The calling process is not privileged (did not have the CAP_SETUID
capability) and tried to change the IDs to values that are not
permitted.
VERSIONS¶
These calls are available under Linux since Linux 2.1.44.
These calls are nonstandard; they also appear on HP-UX and some of the BSDs.
NOTES¶
Under HP-UX and FreeBSD, the prototype is found in
<unistd.h>.
Under Linux, the prototype is provided by glibc since version 2.3.2.
The original Linux
setresuid() and
setresgid() system calls
supported only 16-bit user and group IDs. Subsequently, Linux 2.4 added
setresuid32() and
setresgid32(), supporting 32-bit IDs. The
glibc
setresuid() and
setresgid() wrapper functions
transparently deal with the variations across kernel versions.
SEE ALSO¶
getresuid(2),
getuid(2),
setfsgid(2),
setfsuid(2),
setreuid(2),
setuid(2),
capabilities(7),
credentials(7),
user_namespaces(7)
COLOPHON¶
This page is part of release 3.74 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
http://www.kernel.org/doc/man-pages/.
