1.\" $OpenBSD: issetugid.2,v 1.7 1997/02/18 00:16:09 deraadt Exp $ 2.\" 3.\" Copyright (c) 1980, 1991, 1993 4.\" The Regents of the University of California. All rights reserved. 5.\" 6.\" Redistribution and use in source and binary forms, with or without 7.\" modification, are permitted provided that the following conditions 8.\" are met: 9.\" 1. Redistributions of source code must retain the above copyright 10.\" notice, this list of conditions and the following disclaimer. 11.\" 2. Redistributions in binary form must reproduce the above copyright 12.\" notice, this list of conditions and the following disclaimer in the 13.\" documentation and/or other materials provided with the distribution. 14.\" 3. Neither the name of the University nor the names of its contributors 15.\" may be used to endorse or promote products derived from this software 16.\" without specific prior written permission. 17.\" 18.\" THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND 19.\" ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE 20.\" IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE 21.\" ARE DISCLAIMED. IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE 22.\" FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL 23.\" DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS 24.\" OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) 25.\" HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT 26.\" LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY 27.\" OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF 28.\" SUCH DAMAGE. 29.\" 30.\" $FreeBSD: src/lib/libc/sys/issetugid.2,v 1.7.2.4 2001/12/14 18:34:01 ru Exp $ 31.\" $DragonFly: src/lib/libc/sys/issetugid.2,v 1.2 2003/06/17 04:26:47 dillon Exp $ 32.\" 33.Dd August 25, 1996 34.Dt ISSETUGID 2 35.Os 36.Sh NAME 37.Nm issetugid 38.Nd is current process tainted by uid or gid changes 39.Sh LIBRARY 40.Lb libc 41.Sh SYNOPSIS 42.In unistd.h 43.Ft int 44.Fn issetugid void 45.Sh DESCRIPTION 46The 47.Fn issetugid 48function returns 1 if the process environment or memory address space 49is considered 50.Dq tainted , 51and returns 0 otherwise. 52.Pp 53A process is tainted if it was created as a result of an 54.Xr execve 2 55system call which had either of the setuid or setgid bits set (and extra 56privileges were given as a result) or if it has changed any of its real, 57effective or saved user or group ID's since it began execution. 58.Pp 59This system call exists so that library routines (eg: libc, libtermcap) 60can reliably determine if it is safe to use information 61that was obtained from the user, in particular the results from 62.Xr getenv 3 63should be viewed with suspicion if it is used to control operation. 64.Pp 65A 66.Dq tainted 67status is inherited by child processes as a result of the 68.Xr fork 2 69system call (or other library code that calls fork, such as 70.Xr popen 3 ) . 71.Pp 72It is assumed that a program that clears all privileges as it prepares 73to execute another will also reset the environment, hence the 74.Dq tainted 75status will not be passed on. This is important for programs such as 76.Xr su 1 77which begin setuid but need to be able to create an untainted process. 78.Sh ERRORS 79The 80.Fn issetugid 81function is always successful, and no return value is reserved to 82indicate an error. 83.Sh SEE ALSO 84.Xr execve 2 , 85.Xr fork 2 , 86.Xr setegid 2 , 87.Xr seteuid 2 , 88.Xr setgid 2 , 89.Xr setregid 2 , 90.Xr setreuid 2 , 91.Xr setuid 2 92.Sh HISTORY 93A 94.Fn issetugid 95function call first appeared in 96.Ox 2.0 97and was also implemented in 98.Fx 3.0 . 99