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.\" (Royal Institute of Technology, Stockholm, Sweden).
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.\"	$Id$
.\"
.Dd February 20, 2004
.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 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 Fl krb5
.Xc
The
.Fl 5
option requests Kerberos 5 authentication. This is analogous to the
.Fl 4
option.
.It Xo
.Fl K ,
.Fl Fl broken
.Xc
The
.Fl K
option turns off all Kerberos authentication. The security in this
mode relies on reserved ports. The long name is an indication of how
good this is.
.It Xo
.Fl n ,
.Fl 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 Fl d
Enable
.Xr setsockopt 2
socket debugging.
.It Xo
.Fl e ,
.Fl 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 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, and is mainly useful if encryption has been
enabled by default, for instance in the
.Li appdefaults
section of
.Pa /etc/krb5.conf
when using Kerberos 5.
.It Xo
.Fl f ,
.Fl Fl forward
.Xc
Forward Kerberos 5 credentials to the remote host.
Also settable via
.Li appdefaults
(see
.Xr krb5.conf ) .
.It Xo
.Fl F ,
.Fl Fl forwardable
.Xc
Make the forwarded credentials re-forwardable.
Also settable via
.Li appdefaults
(see
.Xr krb5.conf ) .
.It Xo
.Fl l Ar string ,
.Fl 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 n ,
.Fl Fl no-input
.Xc
Direct input from
.Pa /dev/null
(see the
.Sx BUGS
section).
.It Xo
.Fl p Ar number-or-service ,
.Fl 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 encrypted Kerberos 4; subject of course to
the contents of
.Pa /etc/services ) .
.It Xo
.Fl P Ar N|O|1|2 ,
.Fl Fl protocol= Ns Ar N|O|1|2
.Xc
Specifies the protocol version to use with Kerberos 5.
.Ar N
and
.Ar 2
select protocol version 2, while
.Ar O
and
.Ar 1
select 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.
.It Xo
.Fl u ,
.Fl 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 Fl tkfile= Ns Pa string
.Xc
Name of the remote credentials cache. Mutually exclusive to
.Fl u .
.It Xo
.Fl x ,
.Fl 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 Fl z
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 .
.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 \*[Gt] localfile
.Pp
will write the contents of the remote
.Pa remotefile
to the local
.Pa localfile ,
but:
.Pp
.Dl rsh otherhost 'cat remotefile \*[Gt] 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 ) .
Furthermore in Kerberos 4 the command is not even integrity
protected, so anyone with the right tools can modify the command.