|
setreuid, setregid — set real and/or effective user or group ID
#include <sys/types.h> #include <unistd.h>
int
setreuid( |
uid_t ruid, |
uid_t euid) ; |
int
setregid( |
gid_t rgid, |
gid_t egid) ; |
Note | |||
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|
setreuid
() sets real and
effective user IDs of the calling process.
Supplying a value of −1 for either the real or effective user ID forces the system to leave that ID unchanged.
Unprivileged processes may only set the effective user ID to the real user ID, the effective user ID, or the saved set-user-ID.
Unprivileged users may only set the real user ID to the real user ID or the effective user ID.
If the real user ID is set or the effective user ID is set to a value not equal to the previous real user ID, the saved set-user-ID will be set to the new effective user ID.
Completely analogously, setregid
() sets real and effective group
ID's of the calling process, and all of the above holds with
"group" instead of "user".
On success, zero is returned. On error, −1 is
returned, and errno
is set
appropriately.
The calling process is not privileged (Linux: does
not have the CAP_SETUID
capability in the case of setreuid
(), or the CAP_SETGID
capability in the case of
setregid
()) and a change
other than (i) swapping the effective user (group) ID
with the real user (group) ID, or (ii) setting one to
the value of the other or (iii) setting the effective
user (group) ID to the value of the saved set-user-ID
(saved set-group-ID) was specified.
POSIX.1-2001, 4.3BSD (the setreuid
() and setregid
() function calls first appeared in
4.2BSD).
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).
POSIX.1 does not specify all of possible ID changes that
are permitted on Linux for an unprivileged process. For
setreuid
(), the effective user
ID can be made the same as the real user ID or the save
set-user-ID, and it is unspecified whether unprivileged
processes may set the real user ID to the real user ID, the
effective user ID, or the saved set-user-ID. For setregid
(), the real group ID can be
changed to the value of the saved set-group-ID, and the
effective group ID can be changed to the value of the real
group ID or the saved set-group-ID. The precise details of
what ID changes are permitted vary across
implementations.
POSIX.1 makes no specification about the effect of these calls on the saved set-user-ID and saved set-group-ID.
The original Linux setreuid
() and setregid
() system calls supported only
16-bit user and group IDs. Subsequently, Linux 2.4 added
setreuid32
() and setregid32
(), supporting 32-bit IDs. The
glibc setreuid
() and
setregid
() wrapper functions
transparently deal with the variations across kernel
versions.