setregid(3p) — Linux manual page

SETREGID(3P)            POSIX Programmer's Manual           SETREGID(3P)

PROLOG

       This manual page is part of the POSIX Programmer's Manual.  The
       Linux implementation of this interface may differ (consult the
       corresponding Linux manual page for details of Linux behavior),
       or the interface may not be implemented on Linux.

NAME

       setregid — set real and effective group IDs

SYNOPSIS

       #include <unistd.h>

       int setregid(gid_t rgid, gid_t egid);

DESCRIPTION

       The setregid() function shall set the real and effective group
       IDs of the calling process.

       If rgid is -1, the real group ID shall not be changed; if egid is
       -1, the effective group ID shall not be changed.

       The real and effective group IDs may be set to different values
       in the same call.

       Only a process with appropriate privileges can set the real group
       ID and the effective group ID to any valid value.

       A non-privileged process can set either the real group ID to the
       saved set-group-ID from one of the exec family of functions, or
       the effective group ID to the saved set-group-ID or the real
       group ID.

       If the real group ID is being set (rgid is not -1), or the
       effective group ID is being set to a value not equal to the real
       group ID, then the saved set-group-ID of the current process
       shall be set equal to the new effective group ID.

       Any supplementary group IDs of the calling process remain
       unchanged.

RETURN VALUE

       Upon successful completion, 0 shall be returned. Otherwise, -1
       shall be returned and errno set to indicate the error, and
       neither of the group IDs are changed.

ERRORS

       The setregid() function shall fail if:

       EINVAL The value of the rgid or egid argument is invalid or out-
              of-range.

       EPERM  The process does not have appropriate privileges and a
              change other than changing the real group ID to the saved
              set-group-ID, or changing the effective group ID to the
              real group ID or the saved set-group-ID, was requested.

       The following sections are informative.

EXAMPLES

       None.

APPLICATION USAGE

       If a non-privileged set-group-ID process sets its effective group
       ID to its real group ID, it can only set its effective group ID
       back to the previous value if rgid was -1 in the setregid() call,
       since the saved-group-ID is not changed in that case. If rgid was
       equal to the real group ID in the setregid() call, then the saved
       set-group-ID will also have been changed to the real user ID.

RATIONALE

       Earlier versions of this standard did not specify whether the
       saved set-group-ID was affected by setregid() calls. This version
       specifies common existing practice that constitutes an important
       security feature. The ability to set both the effective group ID
       and saved set-group-ID to be the same as the real group ID means
       that any security weakness in code that is executed after that
       point cannot result in malicious code being executed with the
       previous effective group ID. Privileged applications could
       already do this using just setgid(), but for non-privileged
       applications the only standard method available is to use this
       feature of setregid().

FUTURE DIRECTIONS

       None.

SEE ALSO

       exec(1p), getegid(3p), geteuid(3p), getgid(3p), getuid(3p),
       setegid(3p), seteuid(3p), setgid(3p), setreuid(3p), setuid(3p)

       The Base Definitions volume of POSIX.1‐2017, unistd.h(0p)

COPYRIGHT

       Portions of this text are reprinted and reproduced in electronic
       form from IEEE Std 1003.1-2017, Standard for Information
       Technology -- Portable Operating System Interface (POSIX), The
       Open Group Base Specifications Issue 7, 2018 Edition, Copyright
       (C) 2018 by the Institute of Electrical and Electronics
       Engineers, Inc and The Open Group.  In the event of any
       discrepancy between this version and the original IEEE and The
       Open Group Standard, the original IEEE and The Open Group
       Standard is the referee document. The original Standard can be
       obtained online at http://www.opengroup.org/unix/online.html .

       Any typographical or formatting errors that appear in this page
       are most likely to have been introduced during the conversion of
       the source files to man page format. To report such errors, see
       https://www.kernel.org/doc/man-pages/reporting_bugs.html .

IEEE/The Open Group               2017                      SETREGID(3P)

Pages that refer to this page: unistd.h(0p), getegid(3p), geteuid(3p), getgid(3p), getuid(3p), setegid(3p), seteuid(3p), setgid(3p), setreuid(3p), setuid(3p)

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