Setting up a temporary HTTP/HTTPS proxy via SSH

Currently I’m working on a project where I have the staging environment running on a virtual machine in a vlan. However, the virtual machine cannot directly access the internet for security reasons. This is inconvenient when I want to e.g. run a buildout to update the project.

A colleague told me to use micro_proxy and micro_inetd to proxy traffic via my laptop. This is a description of how you can set things up.

Ad hoc

Obviously the first step is to install the relevant packages on the local machine (Ubuntu in my case):

$ sudo apt-get install micro-proxy micro-inetd

The next step is to run the proxy (again: on my laptop) and make sure it accepts connections on port 3128:

$ micro-inetd 3128 /usr/sbin/micro_proxy

Then, when you SSH into the remote machine you will have to forward the right port:

$ ssh box.example.com -R 3128:localhost:3128

Whenever you want to access the internet, you’ll have to use the proxy listening on port 3128. For instance to run wget and buildout, you can set the following environment variables:

$ export http_proxy=http://localhost:3128
$ export https_proxy=http://localhost:3128

(Note that I’m also proxying HTTPS traffic here, which is supported by micro_proxy.)

The following wget command should now succeed:

$ wget http://www.google.com/

Repeatable

Assuming the ad hoc setup works, you may want to configure things so things are a little bit easier the next time you want to use it. This is what I did.

So I don’t have to remember how to start the proxy, I added this line to the ~/.bashrc file on my local machine:

alias start_proxy='echo Running proxy on port 3128 && micro-inetd 3128 /usr/sbin/micro_proxy'

The SSH command is also too much typing for my liking. So I added this to my ~/.ssh/config file:

Host box
    HostName box.example.com
    RemoteForward 3128 localhost:3128

To make sure that the HTTP(S) proxy is used on the remote machine, I added this to my ~/.bashrc file on the remote:

export http_proxy=http://localhost:3128
export https_proxy=http://localhost:3128

End result

So whenever I want to work on the staging environment, I open a terminal and run:

$ start_proxy

In another terminal I type:

$ ssh box

And I’m good to go.

Now, there may be better solutions (especially if you want to permanently setup a proxy), but for my purposes this works great.

Docker

When I originally wrote this article, I was not yet (or only just) using Docker. But when I was setting up a new laptop a while ago, I wanted to run a proxy in a Docker container.

As a result, I now run the following to start a proxy:

$ docker run --name squid -d -p 3128:3128 datadog/squid

This way I don’t have to install micro_proxy and micro_inetd on my machine.