Chisel is an HTTP client and server which acts as a TCP proxy. Chisel useful in situations where you only have access to HTTP, for example – a corporate firewall. Chisel is similar to crowbar though achieves much higher performance. Warning This is beta software.

Server

$ go get -v github.com/jpillora/chisel/chiseld

Forwarder

$ go get -v github.com/jpillora/chisel/chisel-forward

• Simple
• Reasonably performant
• Client Auto-reconnects with backoff
• Server fallback proxy

A Heroku app is running chiseld on the public HTTP port. This app is also running a file server on 3000 (which is normally inaccessible due to Heroku's firewall). However, if we tunnel in with:

$ chisel-forward --auth foobar https://chisel-demo.herokuapp.com/ 3000

Then open http://localhost:3000/, we should see a directory listing of this app's root.

Both command-line programs have useful help text, see chiseld --help and chisel-forward --help.

Eventually, a programmatic API will be documented and available, if you're keen see the main.go files in each sub-package.

Currently, secure communications are attained by hosting your HTTP server behind a TLS proxy. Thereby upgrading your server to HTTPS. In the future, the server will allow your to pass in TLS credentials and make use of Go's TLS (HTTPS) server.

With crowbar, a connection is tunnelled by repeatedly querying the server with updates. This results in a large amount of HTTP and TCP connection overhead. Chisel overcomes this using WebSockets combined with Yamux to create SDPY/HTTP2 like logical connections, therefore, each client will only need 1 TCP connection.

In this test, we have:

curl -> http tunnel client -> http tunnel server -> file server

Tab 1 (local file server)

$ npm i -g serve
$ serve -p 4000

Tab 2 (tunnel server)

$ echo -ne "foo:bar" > userfile
$ crowbard -listen="0.0.0.0:8080" -userfile=./userfile

Tab 3 (tunnel client)

$ crowbar-forward -local=0.0.0.0:3000 -server http://localhost:8080 -remote localhost:4000 -username foo -password bar

Tab 4 (transfer test)

$ time curl -s "127.0.0.1:3000/largefile.bin" > /dev/null
       74.74 real         2.37 user         6.74 sys

Here, we see largefile.bin (~200MB) is transferred in 1m14s (along with high CPU utilisation).

Enter chisel, lets swap in chiseld and chisel-forward

Tab 2 (tunnel server)

$ chiseld --auth foo

Tab 3 (tunnel client)

$ chisel-forward --auth foo http://localhost:8080 3000:4000
2015/02/27 16:13:43 Connected to http://localhost:8080
2015/02/27 16:13:43 Proxy 0.0.0.0:3000 => 0.0.0.0:4000 enabled

And now we'll run the test again

$ time curl -s "127.0.0.1:3000/largefile.bin" > /dev/null
       0.60 real         0.05 user         0.14 sys

Here, the same file was transferred in 0.6s

• http://golang.org/doc/code.html
• http://golang.org/doc/effective_go.html
• github.com/jpillora/chisel contains the shared package
• github.com/jpillora/chisel/chiseld contains the server package
• github.com/jpillora/chisel/chisel-forward contains the client package

• Add tests (Bonus: Add benchmarks)
• User file with list of whitelisted remotes
• TLS server configuration
• Encrypt data with auth as the secret (Poor man's TLS)
• Expose a stats page for proxy throughput
• Configurable connection retry times

Copyright © 2014 Jaime Pillora <[email protected]>

Permission is hereby granted, free of charge, to any person obtaining a copy of this software and associated documentation files (the 'Software'), to deal in the Software without restriction, including without limitation the rights to use, copy, modify, merge, publish, distribute, sublicense, and/or sell copies of the Software, and to permit persons to whom the Software is furnished to do so, subject to the following conditions:

The above copyright notice and this permission notice shall be included in all copies or substantial portions of the Software.

THE SOFTWARE IS PROVIDED 'AS IS', WITHOUT WARRANTY OF ANY KIND, EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE SOFTWARE.