ProxyBySsh

To get Web access to the I-MATH intranet webserver it is possible to set up a SOCKS SSH proxy channel. This setting is not persistent, start it when you need it.

The proxy configuration can be done:

• on the OS - not described here.
• via commandline - described here for Google Chrome and Opera.
• inside the browser via GUI - described here for Firefox.

SSH Proxy

• Use SSH
  • Linux & Mac OS X: preinstalled.
  • Windows: https://www.howtogeek.com/336775/how-to-enable-and-use-windows-10s-built-in-ssh-commands/
• Open a terminal and start the SSH Socks connection (I-MATH password):

ssh -C -D 1080 -N -q <I-MATH account>@ssh.math.uzh.ch &

* Define an alias to use it as a onliner (kill's stale ssh proxy connections first)

alias google-chrome-math='OLD=`ps -ef  | grep  "ssh -C -D 1080 -N" | grep -v grep | awk "{ print \\$2 }"`; for II in $OLD; do kill $II; done; (ssh -C -D 1080 -N -q ssh.math.uzh.ch & ); google-chrome --proxy-server="socks5://localhost:1080"'

Browser

To use the I-MATH internal DNS Server (necessary to get access to hostnames that are only known inside of I-MATH), use the SOCKS5 protocol incl. DNS forward.

For Google Chrome or Opera, open a second terminal and type the following command.

Browser	Command
Google Chrome (see also advanced)	Linux: google-chrome --proxy-server="socks5://localhost:1080" Mac OS X: /Applications/Google\ Chrome.app/Contents/MacOS/Google\ Chrome --proxy-server="socks5://localhost:1080"
Opera	Linux: opera --proxy-server="socks5://localhost:1080" Mac OS X: /Applications/Opera.app/Contents/MacOS/Opera --proxy-server="socks5://localhost:1080"

• Firefox
  • There is no official option '-proxy-server' for the command line
  • Start firefox, open 'settings', navigate to 'network' > see screenshot

[image: ff-proxy.png]

FAQ

• Q: Can I configure Google Chrome / Opera via GUI like Firefox
  • A: yes - just check the 'network' seetings.
• Q: Why should I start Google Chrome / Opera via command line?
  • A: This is a very quick way to use the proxy. If you do not need it, start the browser via mouse.
• Q: Can I automate the steps?
  • A: yes. A small bash script should do the trick:

{{{#!sh

#!/bin/bash

nohup google-chrome --proxy-server="socks5://localhost:1080" & ssh -C -D 1080 @ssh.math.uzh.ch

}}}

• Check SSH Keys to setup password less SSH login.
• Q: in Firefox I don't like to toggle the proxy on/off all the time - is there a better way?
  • A: Create an additional profile 'proxy'. Start Firefox via Terminal firefox -P, create the profile, use it and do the proxy config there.

Advanced Setup: Google Chrome Proxy Switch

Install and configure the Google Chrome extension SwitchyOmega to automatically switch proxy for certain URLs.

Configurations: [image: switchyOmega_proxy.png] [image: switchyOmega_autoswitch.png]