328 lines
11 KiB
Groff
328 lines
11 KiB
Groff
.\" Copyright (c) 1995, 1996
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.\" Bill Paul <wpaul@ctr.columbia.edu>. 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 Bill Paul.
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.\" 4. Neither the name of the author nor the names of 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 Bill Paul 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 Bill Paul 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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.\" $Id: rpc.yppasswdd.8,v 1.7 1997/02/22 16:12:53 peter Exp $
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.\"
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.Dd February 8, 1996
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.Dt RPC.YPPASSWDD 8
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.Os
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.Sh NAME
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.Nm rpc.yppasswdd
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.Nd "server for updating NIS passwords"
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.Sh SYNOPSIS
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.Nm rpc.yppasswdd
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.Op Fl t Ar master.passwd template file
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.Op Fl d Ar default domain
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.Op Fl p Ar path
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.Op Fl s
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.Op Fl f
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.Op Fl a
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.Op Fl m
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.Op Fl i
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.Op Fl v
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.Op Fl u
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.Op Fl h
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.Sh DESCRIPTION
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The
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.Nm
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daemon allows users to change their NIS passwords and certain
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other information using the
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.Xr yppasswd 1
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and
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.Xr ypchpass 1
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commands.
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.Nm Rpc.yppasswdd
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is an RPC-based server that accepts incoming password change requests,
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authenticates them, places the updated information in the
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.Pa /var/yp/master.passwd
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template file and then updates the NIS
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.Pa master.passwd
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and
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.Pa passwd
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maps.
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.Pp
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The
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.Nm
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server allows a normal NIS user to change
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his or her NIS password, full name (also
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known as 'GECOS' field) or shell. These updates are typically done using
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the
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.Xr yppasswd 1 ,
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.Xr ypchfn 1 ,
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.Xr ypchsh 1 ,
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or
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.Xr ypchpass 1
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commands. (Some administrators don't want users to be able to change their
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full name information or shells; the server can be invoked with option flags
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that disallow such changes.) When the server receives an update request,
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it compares the address of the client making the request against the
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.Pa securenets
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rules outlined in
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.Pa /var/yp/securenets .
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(See the
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.Xr ypserv 8
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manual page for more information on securenets; the
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.Nm
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server uses the same access control mechanism as
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.Xr ypserv 8 .)
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.Pp
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The server then
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checks the 'old' password supplied by the user to make sure it's
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valid, then performs some sanity checks on the updated information (these
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include checking for embedded control characters, colons or invalid shells).
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Once it is satisfied that the update request is valid, the server modifies
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the template password file (the default is
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.Pa /var/yp/master.passwd )
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and then runs the
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.Pa /usr/libexec/yppwupdate
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script to rebuild the NIS maps. (This script has two arguments passed
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to it: the absolute pathname of the password template that was modified
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and the name of the domain that is to be updated. These in turn are
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passed to
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.Pa /var/yp/Makefile ) .
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.Pp
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The
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.Bx Free
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version of
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.Nm
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also allows the super-user on the NIS master server to perform more
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sophisticated updates on the NIS passwd maps. The super-user can modify
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any field in any user's master.passwd entry in any domain, and can
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do so without knowing the user's existing NIS password (when the server
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receives a request from the super-user, the password authentication
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check is bypassed). Furthermore, if the server is invoked with the
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.Fl a
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flag, the super-user can even add new entries to the maps using
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.Xr ypchpass 1 .
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Again, this only applies to the super-user on the NIS
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master server: none of these special functions can be peformed over
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the network.
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.Pp
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The
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.Nm
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daemon can only be run on a machine that is an NIS master server.
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.Sh OPTIONS
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The following options are available:
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.Bl -tag -width indent
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.It Fl t Ar master.passwd template file
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By default,
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.Nm
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assumes that the template file used to generates the
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.Pa master.passwd
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and
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.Pa passwd
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maps for the default domain is called
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.Pa /var/yp/master.passwd .
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This default can be overridden by specifying an alternate file name
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with the
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.Fl t
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flag.
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.Pp
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Note: if the template file specified with this flag is
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.Pa /etc/master.passwd ,
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.Nm
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will also automatically invoke
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.Xr pwd_mkdb 8
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to rebuild the local password databases in addition to the NIS
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maps.
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.It Fl d Ar domain
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The
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.Nm
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server can support multiple domains, however it must
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choose one domain as a default.
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It will try to use the system default domain name as set by the
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.Xr domainname 1
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command for this default. However,
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if the system domain name is not
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set, a default domain must be specified on
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the command line. If the system default domain is set,
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then this option can be used to override it.
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.It Fl p Ar path
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This option can be used to override the default path to
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the location of the NIS
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map databases. The compiled-in default path is
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.Pa /var/yp .
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.It Fl s
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Disallow changing of shell information.
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.It Fl f
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Disallow changing of full name ('GECOS') information.
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.It Fl a
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Allow additions to be made to the NIS passwd databases. The super-user on the
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NIS master server is permitted to use the
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.Xr ypchpass 1
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command to perform unrestricted modifications to any field in a user's
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.Pa master.passwd
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map entry. When
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.Nm
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is started with this flag, it will also allow the super-user to add new
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records to the NIS passwd maps, just as is possible when using
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.Xr chpass 1
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to modify the local password database.
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.It Fl m
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Turn on multi-domain mode. Even though
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.Xr ypserv 8
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can handle several simultaneous domains, most implementations of
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.Nm
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can only operate on a single NIS domain, which is generally the same as
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the system default domain of the NIS master server. The
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.Bx Free
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.Nm
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attempts to overcome this problem in spite of the inherent limitations
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of the
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.Pa yppasswd
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protocol, which does not allow for a
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.Pa domain
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argument in client requests. In multi-domain mode,
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.Nm
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will search through all the passwd maps of all the domains it
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can find under
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.Pa /var/yp
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until it finds an entry that matches the user information specified in
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a given update request. (Matches are determined by checking the username,
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UID and GID fields.) The matched entry and corresponding domain are then
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used for the update.
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.Pp
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Note that in order for multi-domain mode to work, there have to be
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seperate template files for each domain. For example, if a server
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supports three domains,
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.Pa foo ,
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.Pa bar ,
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and
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.Pa baz ,
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there should be three seperate master.passwd template files called
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.Pa /var/yp/foo/master.passwd ,
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.Pa /var/yp/bar/master.passwd ,
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and
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.Pa /var/yp/baz/master.passwd .
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If
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.Pa foo
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happens to be the system default domain, then its template file can
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be either
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.Pa /var/yp/foo/master.passwd
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or
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.Pa /var/yp/master.passwd .
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The server will check for the latter file first and then use the former
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if it can't find it.
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.Pp
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Multi-domain mode is off by default since it can fail if there are
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duplicate or near-duplicate user entries in different domains. The server
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will abort an update request if it finds more than one user entry that
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matches its search criteria. Even so, paranoid administrators
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may wish to leave multi-domain mode disabled.
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.It Fl i
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If
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.Nm
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is invoked with this flag, it will perform map updates in place. This
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means that instead of just modifying the password template file and
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starting a map update, the server will modify the map databases
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directly. This is useful when the password maps are large: if, for
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example, the password database has tens of thousands of entries, it
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can take several minutes for a map update to complete. Updating the
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maps in place reduces this time to a few seconds.
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.It Fl v
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Turn on verbose logging mode. The server normally only logs messages
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using the
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.Xr syslog 3
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facility when it encounters an error condition, or when processing
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updates for the super-user on the NIS master server. Running the server
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with the
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.Fl v
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flag will cause it to log informational messages for all updates.
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.It Fl u
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Many commercial
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.Xr yppasswd 1
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clients do not use a reserved port when sending requests to
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.Nm rpc.yppasswdd .
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This is either because the
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.Xr yppasswd 1
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program is not installed set-uid root, or because the RPC
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implementation does not place any emphasis on binding to reserved
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ports when establishing client connections for the super-user.
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By default,
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.Nm
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expects to receive requests from clients using reserved ports; requests
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received from non-privileged ports are rejected. Unfortunately, this
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behavior prevents any client systems that to not use privileged
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ports from sucessfully submitting password updates. Specifying
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the
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.Fl u
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flag to
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.Nm
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disables the privileged port check so that it will work with
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.Xr yppasswd 1
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clients that don't use privileged ports. This reduces security to
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a certain small degree, but it might be necessary in cases where it
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is not possible to change the client behavior.
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.It Fl h
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Display the list of flags and options understood by
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.Nm rpc.yppasswdd .
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.El
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.Sh FILES
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.Bl -tag -width Pa -compact
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.It Pa /usr/libexec/yppwupdate
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The script invoked by
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.Nm
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to update and push the NIS maps after
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an update.
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.It Pa /var/yp/master.passwd
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The template password file for the default domain.
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.It Pa /var/yp/[domainname]/[maps]
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The NIS maps for a particular NIS domain.
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.It Pa /var/yp/[domainname]/master.passwd
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The template password file(s) for non-default domains
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(used only in multi-domain mode).
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.El
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.Sh SEE ALSO
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.Xr yp 4 ,
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.Xr yppush 8 ,
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.Xr ypserv 8 ,
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.Xr ypxfr 8
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.Sh BUGS
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As listed in the yppasswd.x protocol definition, the YPPASSWDPROC_UPDATE
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procedure takes two arguments: a V7-style passwd structure containing
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updated user information and the user's existing unencrypted (cleartext)
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password. Since
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.Nm
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is supposed to handle update requests from remote NIS client machines,
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this means that
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.Xr yppasswd 1
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and similar client programs will in fact be transmitting users' cleartext
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passwords over the network.
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.Pp
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This is not a problem for password updates since the plaintext password
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sent with the update will no longer be valid once the new encrypted password
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is put into place, but if the user is only updating his or her 'GECOS'
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information or shell, then the cleartext password sent with the update
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will still be valid once the update is completed. If the network is
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insecure, this cleartext password could be intercepted and used to
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gain unauthorized access to the user's account.
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.Sh AUTHOR
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.An Bill Paul Aq wpaul@ctr.columbia.edu
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