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SETREUID(2) Linux Programmer's Manual SETREUID(2) NAME setreuid, setregid - set real and/or effective user or group ID SYNOPSIS #include <sys/types.h> #include <unistd.h> int setreuid(uid_t ruid, uid_t euid); int setregid(gid_t rgid, gid_t egid); Feature Test Macro Requirements for glibc (see feature_test_macros(7)): setreuid(), setregid(): _BSD_SOURCE || _XOPEN_SOURCE >= 500 || _XOPEN_SOURCE && _XOPEN_SOURCE_EXTENDED DESCRIPTION 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 (i.e., ruid is not -1) 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". RETURN VALUE On success, zero is returned. On error, -1 is returned, and errno is set appropriately. Note: there are cases where setreuid() can fail even when the caller is UID 0; it is a grave security error to omit checking for a failure re- turn from setreuid(). 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 ex- ecve(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 (Linux: does not have the CAP_SETUID capability in the case of setreuid(), or the CAP_SET- GID 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. CONFORMING TO POSIX.1-2001, 4.3BSD (the setreuid() and setregid() function calls first appeared in 4.2BSD). 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). 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 imple- mentations. 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 se- treuid32() and setregid32(), supporting 32-bit IDs. The glibc se- treuid() and setregid() wrapper functions transparently deal with the variations across kernel versions. SEE ALSO getgid(2), getuid(2), seteuid(2), setgid(2), setresuid(2), setuid(2), capabilities(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/. Linux 2014-09-21 SETREUID(2)
NAME | SYNOPSIS | DESCRIPTION | RETURN VALUE | ERRORS | CONFORMING TO | NOTES | SEE ALSO | COLOPHON
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