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.\" $FreeBSD: release/9.1.0/lib/libc/sys/issetugid.2 165903 2007-01-09 00:28:16Z imp $
.\"
.Dd August 25, 1996
.Dt ISSETUGID 2
.Os
.Sh NAME
.Nm issetugid
.Nd is current process tainted by uid or gid changes
.Sh LIBRARY
.Lb libc
.Sh SYNOPSIS
.In unistd.h
.Ft int
.Fn issetugid void
.Sh DESCRIPTION
The
.Fn issetugid
system call returns 1 if the process environment or memory address space
is considered
.Dq tainted ,
and returns 0 otherwise.
.Pp
A process is tainted if it was created as a result of an
.Xr execve 2
system call which had either of the setuid or setgid bits set (and extra
privileges were given as a result) or if it has changed any of its real,
effective or saved user or group ID's since it began execution.
.Pp
This system call exists so that library routines (eg: libc, libtermcap)
can reliably determine if it is safe to use information
that was obtained from the user, in particular the results from
.Xr getenv 3
should be viewed with suspicion if it is used to control operation.
.Pp
A
.Dq tainted
status is inherited by child processes as a result of the
.Xr fork 2
system call (or other library code that calls fork, such as
.Xr popen 3 ) .
.Pp
It is assumed that a program that clears all privileges as it prepares
to execute another will also reset the environment, hence the
.Dq tainted
status will not be passed on.
This is important for programs such as
.Xr su 1
which begin setuid but need to be able to create an untainted process.
.Sh ERRORS
The
.Fn issetugid
system call is always successful, and no return value is reserved to
indicate an error.
.Sh SEE ALSO
.Xr execve 2 ,
.Xr fork 2 ,
.Xr setegid 2 ,
.Xr seteuid 2 ,
.Xr setgid 2 ,
.Xr setregid 2 ,
.Xr setreuid 2 ,
.Xr setuid 2
.Sh HISTORY
The
.Fn issetugid
system call first appeared in
.Ox 2.0
and was also implemented in
.Fx 3.0 .