.\" Copyright (c) 2002 - 2003 Kungliga Tekniska Högskolan
.\" (Royal Institute of Technology, Stockholm, Sweden). 
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.\"	$Id: rsh.1,v 1.6 2003/04/16 19:57:25 lha Exp $
.\"
.Dd September 4, 2002
.Dt RSH 1
.Os HEIMDAL
.Sh NAME
.Nm rsh
.Nd
remote shell
.Sh SYNOPSIS
.Nm
.Op Fl 45FGKdefnuxz
.Op Fl U Pa string
.Op Fl p Ar port
.Op Fl l Ar username
.Op Fl P Ar N|O
.Ar host [command]
.Sh DESCRIPTION
.Nm
authenticates to the
.Xr rshd 8
daemon on the remote
.Ar host ,
and then executes the specified
.Ar command .
.Pp
.Nm
copies its standard input to the remote command, and the standard
output and error of the remote command to its own.
.Pp
Valid options are:
.Bl -tag -width Ds
.It Xo
.Fl 4 ,
.Fl -krb4
.Xc
The
.Fl 4
option requests Kerberos 4 authentication. Normally all supported
authentication mechanisms will be tried, but in some cases more
explicit control is desired.
.It Xo
.Fl 5 ,
.Fl -krb5
.Xc
The
.Fl 5
option requests Kerberos 5 authentication. This is analogous to the
.Fl 4
option.
.It Xo
.Fl K ,
.Fl -broken
.Xc
The
.Fl K
option turns off all Kerberos authentication. The long name implies
that this is more or less totally unsecure. The security in this mode
relies on reserved ports, which is not very secure.
.It Xo
.Fl n ,
.Fl -no-input
.Xc
The
.Fl n
option directs the input from the
.Pa /dev/null
device (see the
.Sx BUGS
section of this manual page).
.It Xo
.Fl e ,
.Fl -no-stderr
.Xc
Don't use a separate socket for the stderr stream. This can be
necessary if rsh-ing through a NAT bridge.
.It Xo
.Fl x ,
.Fl -encrypt
.Xc
The
.Fl x
option enables encryption for all data exchange. This is only valid
for Kerberos authenticated connections (see the
.Sx BUGS
section for limitations).
.It Xo
.Fl z
.Xc
The opposite of
.Fl x .
This is the default, but encryption can be enabled when using
Kerberos 5, by setting the
.Li libdefaults/encrypt
option in
.Xr krb5.conf 5 .
.It Xo
.Fl f ,
.Fl -forward
.Xc
Forward Kerberos 5 credentials to the remote host. Also controlled by
.Li libdefaults/forward
in
.Xr krb5.conf 5 .
.It Xo
.Fl G
.Xc
The opposite of
.Fl f .
.It Xo
.Fl F ,
.Fl -forwardable
.Xc
Make the forwarded credentials re-forwardable. Also controlled by
.Li libdefaults/forwardable
in
.Xr krb5.conf 5 .
.It Xo
.Fl u ,
.Fl -unique
.Xc
Make sure the remote credentials cache is unique, that is, don't reuse
any existing cache. Mutually exclusive to
.Fl U .
.It Xo
.Fl U Pa string ,
.Fl -tkfile= Ns Pa string
.Xc
Name of the remote credentials cache. Mutually exclusive to
.Fl u .
.It Xo
.Fl p Ar number-or-service ,
.Fl -port= Ns Ar number-or-service
.Xc
Connect to this port instead of the default (which is 514 when using
old port based authentication, 544 for Kerberos 5 and non-encrypted
Kerberos 4, and 545 for encrytpted Kerberos 4; subject of course to
the contents of
.Pa /etc/services ) .
.It Xo
.Fl l Ar string ,
.Fl -user= Ns Ar string
.Xc
By default the remote username is the same as the local. The
.Fl l
option or the
.Pa username@host
format allow the remote name to be specified.
.It Xo
.Fl P Ar N|O|1|2 ,
.Fl -protocol= Ns Ar N|O|1|2
.Xc
Specifies which protocol version to use with Kerberos 5.
.Ar N
and
.Ar 2
selects protocol version 2, while 
.Ar O
and
.Ar 1
selects version 1. Version 2 is believed to be more secure, and is the
default. Unless asked for a specific version,
.Nm
will try both.  This behaviour may change in the future.
.El
.\".Pp
.\"Without a
.\".Ar command
.\".Nm
.\"will just exec
.\".Xr rlogin 1
.\"with the same arguments.
.Sh EXAMPLES
Care should be taken when issuing commands containing shell meta
characters. Without quoting, these will be expanded on the local
machine.
.Pp
The following command:
.Pp
.Dl rsh otherhost cat remotefile > localfile
.Pp
will write the contents of the remote
.Pa remotefile
to the local
.Pa localfile ,
but:
.Pp
.Dl rsh otherhost 'cat remotefile > remotefile2'
.Pp
will write it to the remote
.Pa remotefile2 .
.\".Sh ENVIRONMENT
.Sh FILES
.Bl -tag -width /etc/hosts -compact
.It Pa /etc/hosts
.El
.\".Sh DIAGNOSTICS
.Sh SEE ALSO
.Xr rlogin 1 ,
.Xr krb_realmofhost 3 ,
.Xr krb_sendauth 3 ,
.Xr hosts.equiv 5 ,
.Xr krb5.conf 5 ,
.Xr rhosts 5 ,
.Xr kerberos 8
.Xr rshd 8
.\".Sh STANDARDS
.Sh HISTORY
The
.Nm
command appeared in
.Bx 4.2 .
.Sh AUTHORS
This implementation of
.Nm
was written as part of the Heimdal Kerberos 5 implementation.
.Sh BUGS
Some shells (notably
.Xr csh 1 )
will cause
.Nm
to block if run in the background, unless the standard input is directed away from the terminal. This is what the
.Fl n
option is for.
.Pp
The
.Fl x
options enables encryption for the session, but for both Kerberos 4
and 5 the actual command is sent unencrypted, so you should not send
any secret information in the command line (which is probably a bad
idea anyway, since the command line can usually be read with tools
like
.Xr ps 1 ) .
Forthermore in Kerberos 4 the command is not even integrity
protected, so anyone with the right tools can modify the command.