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. All advertising materials mentioning features or use of this software 15.\" must display the following acknowledgement: 16.\" This product includes software developed by the University of 17.\" California, Berkeley and its contributors. 18.\" 4. Neither the name of the University nor the names of its contributors 19.\" may be used to endorse or promote products derived from this software 20.\" without specific prior written permission. 21.\" 22.\" THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND 23.\" ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE 24.\" IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE 25.\" ARE DISCLAIMED. IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE 26.\" FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL 27.\" DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS 28.\" OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) 29.\" HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT 30.\" LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY 31.\" OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF 32.\" SUCH DAMAGE. 33.\" 34.\" $FreeBSD: src/lib/libc/sys/issetugid.2,v 1.7.2.4 2001/12/14 18:34:01 ru Exp $ 35.\" $DragonFly: src/lib/libc/sys/issetugid.2,v 1.2 2003/06/17 04:26:47 dillon Exp $ 36.\" 37.Dd August 25, 1996 38.Dt ISSETUGID 2 39.Os 40.Sh NAME 41.Nm issetugid 42.Nd is current process tainted by uid or gid changes 43.Sh LIBRARY 44.Lb libc 45.Sh SYNOPSIS 46.In unistd.h 47.Ft int 48.Fn issetugid void 49.Sh DESCRIPTION 50The 51.Fn issetugid 52function returns 1 if the process environment or memory address space 53is considered 54.Dq tainted , 55and returns 0 otherwise. 56.Pp 57A process is tainted if it was created as a result of an 58.Xr execve 2 59system call which had either of the setuid or setgid bits set (and extra 60privileges were given as a result) or if it has changed any of its real, 61effective or saved user or group ID's since it began execution. 62.Pp 63This system call exists so that library routines (eg: libc, libtermcap) 64can reliably determine if it is safe to use information 65that was obtained from the user, in particular the results from 66.Xr getenv 3 67should be viewed with suspicion if it is used to control operation. 68.Pp 69A 70.Dq tainted 71status is inherited by child processes as a result of the 72.Xr fork 2 73system call (or other library code that calls fork, such as 74.Xr popen 3 ) . 75.Pp 76It is assumed that a program that clears all privileges as it prepares 77to execute another will also reset the environment, hence the 78.Dq tainted 79status will not be passed on. This is important for programs such as 80.Xr su 1 81which begin setuid but need to be able to create an untainted process. 82.Sh ERRORS 83The 84.Fn issetugid 85function is always successful, and no return value is reserved to 86indicate an error. 87.Sh SEE ALSO 88.Xr execve 2 , 89.Xr fork 2 , 90.Xr setegid 2 , 91.Xr seteuid 2 , 92.Xr setgid 2 , 93.Xr setregid 2 , 94.Xr setreuid 2 , 95.Xr setuid 2 96.Sh HISTORY 97A 98.Fn issetugid 99function call first appeared in 100.Ox 2.0 101and was also implemented in 102.Fx 3.0 . 103