More net pipes

autarch on 2007-04-20T20:36:06

I figured out to make it work with a behind-NAT connection.

I have to connect to the server with ssh like this - ssh -A -R 9999:localhost:22 urth.org

Now I've updated my script to assume that there's a reverse tunnel on port 9999:

#!/usr/bin/perl

use strict;
use warnings;

use File::Temp qw(tempfile);


my ( $fh, $filename ) = tempfile();

print $fh $_ while <>;

seek $fh, 0, 0;

system( 'scp', '-P', 9999, '-o', 'StrictHostKeyChecking=no', $filename, 'localhost:' . $filename );
system( 'ssh', '-p', 9999, '-o', 'StrictHostKeyChecking=no', 'localhost', 'DISPLAY=:0.0 gnome-open ' . $filename );

I was getting lots of host key warnings, presumably because localhost is not really localhost here, it's my client machine.

This spits out some warnings, but it does the job just fine.

BTW, I love how scp uses "-P" for port and ssh uses "-p". Doh!

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As good as it gets…?

Aristotle on 2007-04-20T21:44:39

I think the warnings are because the keys on your machine are for localhost:22 whereas you are connecting to localhost:9999. You should be able to retain host key checks by telling ssh that it’s connecting through a proxy. Here I used netcat.

Try this for extra evil (untested):

#!/usr/bin/perl
use strict;
use warnings;

open my $pipe, '|-', 'ssh', '-o', 'ProxyCommand=nc localhost 9999', 'localhost', 'perl';

die "Can't fork: $!\n" unless defined $pipe;

print $pipe <<'END_PERL';
use strict;
use warnings;
use File::Temp qw( tempfile );

my ( $fh, $filename ) = tempfile();

local $/ = \65536;
print $fh $_ while <DATA>;

$ENV{DISPLAY}=':0.0';
system 'gnome-open', $filename;
__DATA__
END_PERL

local $/ = \65536;
print $fh $_ while <>;

SSH over SSH is not very efficient though. You could write a script that forks and runs ssh then stays around while that process is running, accepting connections on some port (bound to localhost only for security reasons) and writing the data to a file which it invokes gnome-open on it. Then on the remote side all you’d need to do is pipe the file to nc localhost 9999.