74 lines
3.5 KiB
Perl
74 lines
3.5 KiB
Perl
.\" Copyright (c) 1983, 1993
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.\" The Regents of the University of California. All rights reserved.
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.\"
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.\" Redistribution and use in source and binary forms, with or without
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.\" modification, are permitted provided that the following conditions
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.\" are met:
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.\" 1. Redistributions of source code must retain the above copyright
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.\" notice, this list of conditions and the following disclaimer.
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.\" 2. Redistributions in binary form must reproduce the above copyright
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.\" notice, this list of conditions and the following disclaimer in the
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.\" documentation and/or other materials provided with the distribution.
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.\" 3. All advertising materials mentioning features or use of this software
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.\" must display the following acknowledgement:
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.\" This product includes software developed by the University of
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.\" California, Berkeley and its contributors.
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.\" 4. Neither the name of the University nor the names of its contributors
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.\" may be used to endorse or promote products derived from this software
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.\" without specific prior written permission.
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.\"
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.\" THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND
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.\" ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
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.\" IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
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.\" ARE DISCLAIMED. IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE
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.\" FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
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.\" DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
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.\" OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
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.\" HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
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.\" LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
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.\" OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
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.\" SUCH DAMAGE.
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.\"
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.\" @(#)3.t 8.1 (Berkeley) 6/8/93
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.\"
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.NH 1
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Access control
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.PP
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The printer system maintains protected spooling areas so that
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users cannot circumvent printer accounting or
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remove files other than their own.
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The strategy used to maintain protected
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spooling areas is as follows:
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.IP \(bu 3
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The spooling area is writable only by a \fIdaemon\fP user
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and \fIdaemon\fP group.
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.IP \(bu 3
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The \fIlpr\fP program runs set-user-id to \fIroot\fP and
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set-group-id to group \fIdaemon\fP. The \fIroot\fP access permits
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reading any file required. Accessibility is verified
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with an \fIaccess\fP\|(2) call. The group ID
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is used in setting up proper ownership of files
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in the spooling area for \fIlprm\fP.
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.IP \(bu 3
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Control files in a spooling area are made with \fIdaemon\fP
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ownership and group ownership \fIdaemon\fP. Their mode is 0660.
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This insures control files are not modified by a user
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and that no user can remove files except through \fIlprm\fP.
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.IP \(bu 3
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The spooling programs,
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\fIlpd\fP, \fIlpq\fP, and \fIlprm\fP run set-user-id to \fIroot\fP
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and set-group-id to group \fIdaemon\fP to access spool files and printers.
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.IP \(bu 3
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The printer server, \fIlpd\fP,
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uses the same verification procedures as \fIrshd\fP\|(8C)
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in authenticating remote clients. The host on which a client
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resides must be present in the file /etc/hosts.equiv or /etc/hosts.lpd and
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the request message must come from a reserved port number.
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.PP
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In practice, none of \fIlpd\fP, \fIlpq\fP, or
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\fIlprm\fP would have to run as user \fIroot\fP if remote
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spooling were not supported. In previous incarnations of
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the printer system \fIlpd\fP ran set-user-id to \fIdaemon\fP,
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set-group-id to group \fIspooling\fP, and \fIlpq\fP and \fIlprm\fP ran
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set-group-id to group \fIspooling\fP.
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