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+.\" Copyright (c) 1983, 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.
+.\" 3. All advertising materials mentioning features or use of this software
+.\"    must display the following acknowledgement:
+.\"	This product includes software developed by the University of
+.\"	California, Berkeley and its contributors.
+.\" 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.
+.\"
+.\"	@(#)3.t	8.1 (Berkeley) 6/8/93
+.\"
+.NH 1
+Access control
+.PP
+The printer system maintains protected spooling areas so that
+users cannot circumvent printer accounting or
+remove files other than their own.
+The strategy used to maintain protected
+spooling areas is as follows:
+.IP \(bu 3
+The spooling area is writable only by a \fIdaemon\fP user
+and \fIdaemon\fP group.
+.IP \(bu 3
+The \fIlpr\fP program runs set-user-id to \fIroot\fP and
+set-group-id to group \fIdaemon\fP.  The \fIroot\fP access permits
+reading any file required. Accessibility is verified
+with an \fIaccess\fP\|(2) call.  The group ID
+is used in setting up proper ownership of files
+in the spooling area for \fIlprm\fP.
+.IP \(bu 3
+Control files in a spooling area are made with \fIdaemon\fP
+ownership and group ownership \fIdaemon\fP.  Their mode is 0660.
+This insures control files are not modified by a user
+and that no user can remove files except through \fIlprm\fP.
+.IP \(bu 3
+The spooling programs,
+\fIlpd\fP, \fIlpq\fP, and \fIlprm\fP run set-user-id to \fIroot\fP
+and set-group-id to group \fIdaemon\fP to access spool files and printers.
+.IP \(bu 3
+The printer server, \fIlpd\fP,
+uses the same verification procedures as \fIrshd\fP\|(8C)
+in authenticating remote clients.  The host on which a client
+resides must be present in the file /etc/hosts.equiv or /etc/hosts.lpd and
+the request message must come from a reserved port number.
+.PP
+In practice, none of \fIlpd\fP, \fIlpq\fP, or
+\fIlprm\fP would have to run as user \fIroot\fP if remote
+spooling were not supported.  In previous incarnations of
+the printer system \fIlpd\fP ran set-user-id to \fIdaemon\fP,
+set-group-id to group \fIspooling\fP, and \fIlpq\fP and \fIlprm\fP ran
+set-group-id to group \fIspooling\fP.