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.\" $OpenBSD: rlogind.8,v 1.9 2001/06/23 23:15:38 hin Exp $
.\" Copyright (c) 1983, 1989, 1991, 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.
.\"
.\" from: @(#)rlogind.8 8.1 (Berkeley) 6/4/93
.\"
.Dd June 4, 1993
.Dt RLOGIND 8
.Os
.Sh NAME
.Nm rlogind
.Nd remote login server
.Sh SYNOPSIS
.Nm rlogind
.Op Fl alnk
.Sh DESCRIPTION
.Nm
is the server for the
.Xr rlogin 1
program.
The server provides a remote login facility
with authentication based on privileged port numbers from trusted hosts.
.Pp
The options are as follows:
.Bl -tag -width Ds
.It Fl a
Ask hostname for verification.
This flag is ignored; this feature is always enabled.
.It Fl k
Use Kerberos authentication
.It Fl l
Prevent any authentication based on the user's
.Pa .rhosts
file, unless the user is logging in as the superuser.
.It Fl n
Disable keep-alive messages.
.El
.Pp
.Nm
listens for service requests at the port indicated in the
.Dq login
service specification; see
.Xr services 5 .
When a service request is received the following protocol
is initiated:
.Bl -enum
.It
The server checks the client's source port.
If the port is not in the range 512-1023, the server
aborts the connection.
.It
The server checks the client's source address
and requests the corresponding host name (see
.Xr gethostbyaddr 3 ,
.Xr hosts 5
and
.Xr named 8 ) .
If the hostname cannot be determined,
the dot-notation representation of the host address is used.
If the hostname is in the same domain as the server (according to
the last two components of the domain name),
or if the
.Fl a
option is given,
the addresses for the hostname are requested,
verifying that the name and address correspond.
Normal authentication is bypassed if the address verification fails.
.El
.Pp
Once the source port and address have been checked,
.Nm
proceeds with the authentication process described in
.Xr rshd 8 .
It then allocates a pseudo terminal (see
.Xr pty 4 ) ,
and manipulates file descriptors so that the slave
half of the pseudo terminal becomes the
.Em stdin ,
.Em stdout ,
and
.Em stderr
for a login process.
The login process is an instance of the
.Xr login 1
program, invoked with the
.Fl f
option if authentication has succeeded.
If automatic authentication fails, the user is
prompted to log in as if on a standard terminal line.
.Pp
The parent of the login process manipulates the master side of
the pseudo terminal, operating as an intermediary
between the login process and the client instance of the
.Xr rlogin
program.
In normal operation, the packet protocol described in
.Xr pty 4
is invoked to provide
.Ql ^S/^Q
type facilities and propagate
interrupt signals to the remote programs.
The login process propagates the client terminal's baud rate and terminal type,
as found in the environment variable,
.Ql Ev TERM ;
see
.Xr environ 7 .
The screen or window size of the terminal is requested from the client,
and window size changes from the client are propagated to the pseudo terminal.
.Pp
Transport-level keepalive messages are enabled unless the
.Fl n
option is present.
The use of keepalive messages allows sessions to be timed out
if the client crashes or becomes unreachable.
.Sh DIAGNOSTICS
All initial diagnostic messages are indicated
by a leading byte with a value of 1,
after which any network connections are closed.
If there are no errors before
.Xr login
is invoked, a null byte is returned as in indication of success.
.Bl -tag -width Ds
.It Sy Try again.
A
.Xr fork
by the server failed.
.El
.Sh SEE ALSO
.Xr login 1 ,
.Xr ruserok 3 ,
.Xr rshd 8
.Sh HISTORY
The
.Nm
command appeared in
.Bx 4.2 .
.Sh BUGS
The authentication procedure used here assumes the integrity
of each client machine and the connecting medium.
.Pp
A more extensible protocol should be used.
.Pp
.Nm
does not currently support encryption of the datastream when Kerberos
authentication is used.
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