Shellbar

Shellbar relays websocket streams for secure point-to-point communications

Why?

Remote laboratory experiments are often located behind firewalls without the prospect of installing a conventional jumpserver to aid administration. While there are a number of *nix tools that could do this job on a one-off basis with just a bit of script-glue (various combinations of socat and websocat), there is no existing solution that

• is well-suited to management of large numbers remote experiments
• can handle fully interactive shells without some gremlins, such as fatal connection loss on Ctrl+C
• supports multiple simultaneous independent client connections to the same service
• allows all clients and servers to simultaneously connect to the relay on the same port yet keep traffic separate

Features

• binary and text websockets
• separate treatment for servers and clients
• servers requires custom client to multiplex the individual client streams (in development at timdrysdale/sa)
• clients can use any websocket client they like
• multiple 1:1 streams
  • organised by topics
  • topics set by routing
  • multiple clients can connect to the same topic for 1:1 connection with server
  • when multiple clients connect to the same topic, they can not see each other's traffic
  • only servers can see the traffic from clients
• statistics are recorded, and available via
  • websocket API in JSON format
  • human-readable webpage with 5sec update at <host>/stats

What's with the name?

It's a variation on a websocket relay called timdrysdale/crossbar. Shellbar is mainly intended for relaying shell commands, e.g. via ssh for interactive sessions and remote administration e.g. via ansible. The two projects address different parts of the practable™ ecosystem, so it make senses to keep their development separate.

Getting started

Binaries will be available in the future, but for now it is straightforward to compile.

It's quick and easy to create a working go system, following the advice here.

Get the code, test, and install

$ go get github.com/timdrysdale/crossbar
$ cd `go list -f '{{.Dir}}' github.com/timdrysdale/shellbar`
$ go test ./cmd
$ go install

To run the relay

$export SHELLBAR_LISTEN=:8888
$ shellbar

Navigate to the stats page, e.g. http://localhost:8888/stats

You won't see any connections, yet.

You can connect using any of the other tools in the practable ecosystem, e.g. timdrysdale/vw or if you already have the useful websocat installed, then

websocat --text ws://127.0.0.1:8888/expt - 

If you type some messages, you will see the contents of the row change to reflect that you have sent messages.

Applications

Relaying shell access

ssh is a server-speaks-first protocol, which has influenced the design toward using a custom websocket client at the server, which works with the relay to the keep the data streams separate for each client.

Usage

connect with a suitable shellbar client to the server routing, <yourhost>/serve/some/routing. Connect with clients to <yourhost>/some/routing. Each client will have a separate 1:1 stream with the server. The shellbar client at the server end is required to make a new connection to the service every time a new client connects to the shellbar relay, so that server-speaks-first protocols like ssh work.

Support / Contributions

Get in touch! My efforts are going into system development at present so support for alpha-stage users is by personal arrangement/consultancy at present. If you wish to contribute, or have development resource available to do so, I'd be more than delighted to discuss with you the possibilities.