Richard Jones, Esq.

ssh hack: connect directly to machine via a firewall box

UPDATED 23/03/2009: added “-q0″ option to clean up netcat after session terminates, and left another useful ssh tip in the comments.

It’s common to have to ssh to firewall / gateway machine, then ssh to the machine you want to work on within a server network.
Typically you’d do this from your local machine:
$ ssh firewall.example.com
Password:
$ ssh my-private-host

I finally got bored of doing this, and created the following file, /usr/bin/sssh

#!/bin/bash
ssh -oproxycommand="ssh -q firewall.example.com nc -q0 %h %p" $*

Now I can use the sssh command to connect to hosts using the firewall machine as a proxy. Like most good hacks, this uses netcat.

Eg:
$ sssh 10.1.2.3
Will connect me directly to a machine on the server network, via the firewall box. Seeing as it passes all parameters to ssh (the $* bit) you can do port forwards and X-forwarding as usual too:

$ sssh -L 5432:localhost:5432 my-vm

This lets me tunnel the port for a PostgreSQL running on my development vm (my-vm) in a single command. I have all my keys installed, so no passwords needed – I estimate this will save me about 60 seconds every day.

Tags: hack, ssh

Transcoding HTTP mp3 streaming proxy in bash

Here’s how to make a proxy for streaming mp3s. It transcodes on-the-fly to 64kpbs MP3 using lame. When transcoding is finished, it calls the ./posthandler.sh script, which can either just delete the file, or potentially archive it so you don’t need to transcode it again.

One interesting limitation seems to be the buffer size of a fifo pipe in linux. Even though the transcoding step is pretty quick, if a client is connected the transcoding only manages to fill the pipe a couple of hundred k ahead of what is being read.

The -i flag to `tee` means it ignores interrupts, and will finish transcoding the file and call the posthandler even if the client disconnects.

Run is like this:

while [ 1 ]; do nc -vlp 8080 -c './transstreamer.sh' ; done

Then hit up a url of your choice using your awesome new proxy:

mpg321 "http://localhost:8080/http://freedownloads.last.fm/download/105468518/Letters%2BFrom%2BThe%2BBoatman.mp3"

Not the most scalable solution, but a mildly amusing quick hack.

Tags: bash, hack, netcat, streaming