This is a very basic setup but I’m sharing mine in hopes of saving someone a bunch of googling.
<insert the usual drill about TOR and anonymity and why it’s important>
So my goal was not to anonymize my every move, but rather to be able to key in an *.onion website into the URL bar of any device on the local network and have that delivered transparently. I happen to own a fancy Asus router with AsusWRT-Merlin on board, but the approach should work on pretty much any Linux box that can route traffic.
Step 1: Get TOR installed. Use the package manager available for your router/Linux box. Here’s my config from the router:
SocksPort 9050 Log notice file /tmp/torlog VirtualAddrNetwork 10.192.0.0/10 AutomapHostsOnResolve 1 TransPort 9040 TransListenAddress 192.168.1.1 DNSPort 9053 DNSListenAddress 192.168.1.1 RunAsDaemon 1 DataDirectory /tmp/.tordb AvoidDiskWrites 1
A client must first request the domain to be resolved through TOR’s DNS (which in our case will be available at 192.168.1.1:9053). TOR will respond with an address from the 10.192.0.0/10 subnet. The browser will then attempt to connect to said IP address, which our router should intercept and redirect to 192.168.1.1:9040.
Step 2: Figure out DNS resolution. We want to resolve *.onion domains through TOR and resolve everything else through our regular DNS server. My router uses dnsmasq, so adding this line to the config file should do the trick:
Kill and restart dnsmasq for this to take effect.
Step 3: Intercept and redirect. Easy:
iptables -t nat -A PREROUTING -d 10.192.0.0/10 -i br0 -p tcp -m tcp -j REDIRECT --to-ports 9040
At this point you should be able to open an *.onion website in your browser and see it just work!
Step 4: Making the changes persistent. This one will depend on how your router firmware handles that. For mine, I created two new files in the persistent partition (a.k.a. JFFS).
#!/bin/sh iptables -t nat -A PREROUTING -d 10.192.0.0/10 -i br0 -p tcp -m tcp -j REDIRECT --to-ports 9040
chmod a+rx /jffs/scripts/*
That’s it. Read more on user scripts in AsusWRT-Merlin here if you feel like it.