NAME
issetugid —
is current executable running setuid or
setgid
SYNOPSIS
#include
<unistd.h>
int
issetugid(void);
DESCRIPTION
The
issetugid()
function returns 1 if the process was made setuid or setgid as the result of
the last or other previous
execve()
system calls. Otherwise it returns 0.
This system call exists so that library routines (inside libtermlib, libc, or other libraries) can guarantee safe behavior when used inside setuid or setgid programs. Some library routines may be passed insufficient information and hence not know whether the current program was started setuid or setgid because higher level calling code may have made changes to the uid, euid, gid, or egid. Hence these low-level library routines are unable to determine if they are being run with elevated or normal privileges.
In particular, it is wise to use this call to
determine if a pathname returned from a
getenv()
call may safely be used to
open()
the specified file. Quite often this is not wise because the status of the
effective uid is not known.
The
issetugid()
system call's result is unaffected by calls to
setuid(),
setgid(),
or other such calls. In case of a
fork(),
the child process inherits the same status.
The status of
issetugid()
is only affected by
execve().
If a child process executes a new executable file, a new issetugid status
will be determined. This status is based on the existing process's uid,
euid, gid, and egid permissions and on the modes of the executable file. If
the new executable file modes are setuid or setgid, or if the existing
process is executing the new image with uid != euid or gid != egid, the new
process will be considered issetugid.
ERRORS
The issetugid() function is always
successful, and no return value is reserved to indicate an error.
SEE ALSO
execve(2), setegid(2), seteuid(2), setgid(2), setuid(2), getenv(3)
HISTORY
The issetugid() function call first
appeared in OpenBSD 2.0.