Tor 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.
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.