Tor part 1: how-to use Tor

Author: Solène

Date: 10 October 2018

Tags: openbsd unix tor security

NILTor is a network service allowing to hide your traffic. People

sniffing your network will not be able to know what server you reach

and people on the remote side (like the administrator of a web

service) will not know where you are from. Tor helps keeping your

anonymity and privacy.

To make it quick, tor make use of an entry point that you reach

directly, then servers acting as relay not able to decrypt the data

relayed, and up to an exit node which will do the real request for

you, and the network response will do the opposite way.

You can find more details on the

[Tor project homepage](https://www.torproject.org).

Installing tor is __really__ easy on OpenBSD. We need to install it,

and start its daemon. The daemon will listen by default on localhost

on port 9050. On others systems, it may be quite similar, install the

tor package and enable the daemon if not enabled by default.

pkg_add tor

rcctl enable tor

rcctl start tor

Now, you can use your favorite program, look at the proxy settings and

choose "SOCKS" proxy, v5 if possible (it manage the DNS queries) and

use the default address: `127.0.0.1` with port `9050`.

If you need to use tor with a program that doesn't support setting a

SOCKS proxy, it's still possible to use **torsocks** to wrap it, that

will work with most programs. It is very easy to use.

pkg_add torsocks

$ torsocks ssh remoteserver

This will make ssh going through tor network.

Using tor won't make you relaying anything, and is legal in most

countries. Tor is like a VPN, some countries has laws about VPN, check

for your country laws if you plan to use tor. Also, note that using

tor may be forbidden in some networks (companies, schools etc..)

because this allows to escape filtering which may be against some kind

of "Agreement usage" of the network.

I will cover later the relaying part, which can lead to legal

uncertainty.

Note: as torsocks is a bit of a hack, because it uses LD_PRELOAD to

wrap network system calls, there is a way to do it more cleanly with

ssh (or any program supporting a custom command for initialize the

connection) using netcat.

ssh -o ProxyCommand='/usr/bin/nc -X 5 -x 127.0.0.1:9050 %h %p' address.onion

This can be simplified by adding the following lines to your

**~/.ssh/config** file, in order to automatically use the proxy

command when you connect to a .onion hostname:

Host *.onion

ProxyCommand='/usr/bin/nc -X 5 -x 127.0.0.1:9050 %h %p'

This netcat command is tested under OpenBSD, there are differents

netcat implementations, the flags may be differents or may not even

exist.