ISSETUGID(2) System Calls ISSETUGID(2)
NAME
issetugid - determine if current executable is running setuid or setgid
SYNOPSIS
#include <unistd.h>
int issetugid(
void);
DESCRIPTION
The
issetugid() function enables library functions (in
libtermlib,
libc,
or other libraries) to guarantee safe behavior when used in
setuid or
setgid programs or programs that run with more privileges after a
successful
exec(2). Some library functions might be passed insufficient
information and not know whether the current program was started
setuid or
setgid because a higher level calling code might have made changes to
the
uid,
euid,
gid, or
egid. These low-level library functions are
therefore unable to determine if they are being run with elevated or
normal privileges.
The
issetugid() function should be used to determine if a path name
returned from a
getenv(3C) call can be used safely to open the specified
file. It is often not safe to open such a file because the status of the
effective
uid is not known.
The result of a call to
issetugid() is unaffected by calls to
setuid(),
setgid(), or other such calls. In case of a call to
fork(2), the child
process inherits the same status.
The status of
issetugid() is affected only by
execve() (see
exec(2)). If
a child process executes a new executable file, a new
issetugid() status
will be 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, or if the
permitted set before the call to the
exec function is not a superset of
the inheritable set at that time,
issetugid() returns 1 in the new
process.
RETURN VALUES
The
issetugid() function returns 1 if the process was made
setuid or
setgid as the result of the last or a previous call to
execve().
Otherwise it returns 0.
ERRORS
The
issetugid() function is always successful. No return value is
reserved to indicate an error.
ATTRIBUTES
See
attributes(7) for descriptions of the following attributes:
+--------------------+-------------------+
| ATTRIBUTE TYPE | ATTRIBUTE VALUE |
+--------------------+-------------------+
|Interface Stability | Evolving |
+--------------------+-------------------+
|MT-Level | Async-Signal-Safe |
+--------------------+-------------------+
SEE ALSO
exec(2),
fork(2),
setuid(2),
getenv(3C),
attributes(7),
privileges(7) April 9, 2016
ISSETUGID(2)