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+.\"	$OpenBSD: issetugid.2,v 1.7 1997/02/18 00:16:09 deraadt Exp $
+.\"
+.\" Copyright (c) 1980, 1991, 1993
+.\"	The Regents of the University of California.  All rights reserved.
+.\"
+.\" Redistribution and use in source and binary forms, with or without
+.\" modification, are permitted provided that the following conditions
+.\" are met:
+.\" 1. Redistributions of source code must retain the above copyright
+.\"    notice, this list of conditions and the following disclaimer.
+.\" 2. Redistributions in binary form must reproduce the above copyright
+.\"    notice, this list of conditions and the following disclaimer in the
+.\"    documentation and/or other materials provided with the distribution.
+.\" 4. Neither the name of the University nor the names of its contributors
+.\"    may be used to endorse or promote products derived from this software
+.\"    without specific prior written permission.
+.\"
+.\" THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND
+.\" ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
+.\" IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
+.\" ARE DISCLAIMED.  IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE
+.\" FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
+.\" DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
+.\" OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
+.\" HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
+.\" LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
+.\" OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
+.\" SUCH DAMAGE.
+.\"
+.\" $FreeBSD$
+.\"
+.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 .