336 lines
8.6 KiB
Groff
336 lines
8.6 KiB
Groff
.\" $NetBSD: rcmd.3,v 1.25 2003/08/07 16:43:12 agc Exp $
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.\"
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.\" Copyright (c) 1983, 1991, 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. 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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.\" @(#)rcmd.3 8.1 (Berkeley) 6/4/93
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.\"
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.Dd June 4, 1993
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.Dt RCMD 3
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.Os
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.Sh NAME
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.Nm rcmd ,
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.Nm orcmd ,
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.Nm rcmd_af ,
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.Nm orcmd_af ,
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.Nm rresvport ,
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.Nm rresvport_af ,
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.Nm iruserok ,
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.Nm ruserok ,
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.Nm iruserok_sa
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.Nd routines for returning a stream to a remote command
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.Sh LIBRARY
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.Lb libc
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.Sh SYNOPSIS
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.In unistd.h
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.Ft int
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.Fn rcmd "char **ahost" "int inport" "const char *locuser" "const char *remuser" "const char *cmd" "int *fd2p"
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.Ft int
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.Fn orcmd "char **ahost" "int inport" "const char *locuser" "const char *remuser" "const char *cmd" "int *fd2p"
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.Ft int
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.Fn rcmd_af "char **ahost" "int inport" "const char *locuser" "const char *remuser" "const char *cmd" "int *fd2p" "int af"
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.Ft int
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.Fn orcmd_af "char **ahost" "int inport" "const char *locuser" "const char *remuser" "const char *cmd" "int *fd2p" "int af"
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.Ft int
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.Fn rresvport "int *port"
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.Ft int
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.Fn rresvport_af "int *port" "int family"
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.Ft int
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.Fn iruserok "u_int32_t raddr" "int superuser" "const char *ruser" "const char *luser"
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.Ft int
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.Fn ruserok "const char *rhost" "int superuser" "const char *ruser" "const char *luser"
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.Ft int
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.Fn iruserok_sa "const void *raddr" "int rlen" "int superuser" "const char *ruser" "const char *luser"
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.Sh DESCRIPTION
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The
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.Fn rcmd
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function is available for use by anyone to run commands on a
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remote system. It acts like the
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.Fn orcmd
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command, with the exception that it makes a call out to the
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.Xr rcmd 1
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command, or any other user-specified command, to perform the
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actual connection (thus not requiring
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that the caller be running as the super-user), and is only
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available for the
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.Dq shell/tcp
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port.
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The
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.Fn orcmd
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function
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is used by the super-user to execute a command on
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a remote machine using an authentication scheme based
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on reserved port numbers.
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While
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.Fn rcmd
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and
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.Fn orcmd
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can only handle IPv4 address in the first argument,
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.Fn rcmd_af
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and
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.Fn orcmd_af
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can handle other cases as well.
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The
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.Fn rresvport
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function
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returns a descriptor to a socket
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with an address in the privileged port space.
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The
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.Fn rresvport_af
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function is similar to
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.Fn rresvport ,
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but you can explicitly specify the address family to use.
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Calling
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.Fn rresvport_af
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with
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.Dv AF_INET
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has the same effect as
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.Fn rresvport .
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The
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.Fn iruserok
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and
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.Fn ruserok
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functions are used by servers
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to authenticate clients requesting service with
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.Fn rcmd .
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All six functions are present in the same file and are used
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by the
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.Xr rshd 8
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server (among others).
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.Fn iruserok_sa
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is an address family independent variant of
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.Fn iruserok .
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.Pp
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The
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.Fn rcmd
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function
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looks up the host
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.Fa *ahost
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using
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.Xr gethostbyname 3 ,
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returning \-1 if the host does not exist.
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Otherwise
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.Fa *ahost
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is set to the standard name of the host
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and a connection is established to a server
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residing at the well-known Internet port
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.Fa inport .
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.Pp
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If the connection succeeds,
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a socket in the Internet domain of type
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.Dv SOCK_STREAM
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is returned to the caller, and given to the remote
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command as
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.Em stdin
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and
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.Em stdout .
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If
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.Fa fd2p
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is non-zero, then an auxiliary channel to a control
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process will be set up, and a descriptor for it will be placed
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in
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.Fa *fd2p .
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The control process will return diagnostic
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output from the command (unit 2) on this channel, and will also
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accept bytes on this channel as being
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.Ux
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signal numbers, to be
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forwarded to the process group of the command.
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If
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.Fa fd2p
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is 0, then the
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.Em stderr
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(unit 2 of the remote
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command) will be made the same as the
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.Em stdout
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and no
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provision is made for sending arbitrary signals to the remote process,
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although you may be able to get its attention by using out-of-band data.
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.Pp
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.Fn rcmd_af
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and
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.Fn orcmd_af
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take address family in the last argument.
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If the last argument is
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.Dv PF_UNSPEC ,
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interpretation of
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.Fa *ahost
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will obey the underlying address resolution like DNS.
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.Pp
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The protocol is described in detail in
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.Xr rshd 8 .
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.Pp
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The
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.Fn rresvport
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and
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.Fn rresvport_af
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functions are used to obtain a socket with a privileged
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address bound to it. This socket is suitable for use
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by
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.Fn rcmd
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and several other functions. Privileged Internet ports are those
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in the range 0 to 1023. Only the super-user
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is allowed to bind an address of this sort to a socket.
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.Pp
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The
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.Fn iruserok
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and
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.Fn ruserok
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functions take a remote host's IP address or name, respectively,
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two user names and a flag indicating whether the local user's
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name is that of the super-user.
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Then, if the user is
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.Em NOT
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the super-user, it checks the
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.Pa /etc/hosts.equiv
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file.
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If that lookup is not done, or is unsuccessful, the
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.Pa .rhosts
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in the local user's home directory is checked to see if the request for
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service is allowed.
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.Pp
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If this file does not exist, is not a regular file, is owned by anyone
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other than the user or the super-user, or is writable by anyone other
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than the owner, the check automatically fails.
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Zero is returned if the machine name is listed in the
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.Dq Pa hosts.equiv
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file, or the host and remote user name are found in the
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.Dq Pa .rhosts
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file; otherwise
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.Fn iruserok
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and
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.Fn ruserok
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return \-1.
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If the local domain (as obtained from
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.Xr gethostname 3 )
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is the same as the remote domain, only the machine name need be specified.
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.Pp
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If the IP address of the remote host is known,
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.Fn iruserok
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should be used in preference to
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.Fn ruserok ,
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as it does not require trusting the DNS server for the remote host's domain.
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.Pp
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While
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.Fn iruserok
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can handle IPv4 addresses only,
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.Fn iruserok_sa
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and
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.Fn ruserok
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can handle other address families as well, like IPv6.
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The first argument of
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.Fn iruserok_sa
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is typed as
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.Fa "void *"
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to avoid dependency between
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.Aq Li unistd.h
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and
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.Aq Li sys/socket.h .
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.Sh ENVIRONMENT
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.Bl -tag -width RCMD_CMDxx -compact
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.It Ev RCMD_CMD
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When using the
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.Fn rcmd
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function, this variable is used as the program to run instead of
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.Xr rcmd 1 .
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.El
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.Sh DIAGNOSTICS
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The
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.Fn rcmd
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function
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returns a valid socket descriptor on success.
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It returns \-1 on error and prints a diagnostic message on the standard error.
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.Pp
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The
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.Fn rresvport
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and
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.Fn rresvport_af
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function
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return a valid, bound socket descriptor on success.
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They return \-1 on error with the global value
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.Va errno
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set according to the reason for failure.
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The error code
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.Dv EAGAIN
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is overloaded to mean ``All network ports in use.''
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.Sh SEE ALSO
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.Xr rcmd 1 ,
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.Xr rlogin 1 ,
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.Xr rsh 1 ,
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.Xr intro 2 ,
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.Xr rexec 3 ,
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.Xr hosts.equiv 5 ,
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.Xr rhosts 5 ,
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.Xr rexecd 8 ,
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.Xr rlogind 8 ,
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.Xr rshd 8
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.Sh HISTORY
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The
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.Fn orcmd ,
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.Fn rresvport ,
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.Fn iruserok
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and
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.Fn ruserok
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functions appeared in
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.Bx 4.2 ,
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where the
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.Fn orcmd
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function was called
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.Fn rcmd .
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The (newer)
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.Fn rcmd
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function appeared in
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.Nx 1.3 .
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.Fn rcmd_af
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and
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.Fn rresvport_af
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were defined in RFC2292.
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.Sh BUGS
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As the
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.Nm
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function uses
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.Xr getpwent 3
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functions,
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passing in a previous value from one of this family of functions
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can result in unpredictable results. Do not write code like the
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following:
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.Bd -literal -offset indent
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struct passwd *pw;
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pw = getpwuid(getuid());
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...
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if (rcmd(host, port, pw-\*[Gt]pw_name, pw-\*[Gt]pw_name, cmd, fd2p) \*[Lt] 0)
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err(1, "rcmd");
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.Ed
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.Pp
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When a reentrant version of
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.Xr getpwent 3
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is available,
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.Nm
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should be changed to use this instead.
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