Pi(e) Holing Facebook

It all started with a click. While reading the newspaper i clicked on a link to Facebook and was shocked when it opened.

The reason for my surprise was that in my /etc/hosts i had the following entry:

# Block Facebook
127.0.0.1   www.facebook.com
127.0.0.1   facebook.com

a rather blunt instrument, but one that until now had been effective at shitcanning any links. So why had it stopped working? After some confused poking around it became obvious that my new ISP provided way more IPv6 routing than the old ISP, and macOS was now favouring IPv6 traffic. As a consequence the hack in my /etc/hosts grew to include entries for IPv6:

fe80::1%lo0 www.facebook.com
fe80::1%lo0 facebook.com

And once more Facebook was back in the shitcan.

Note: adding hosts to /etc/hosts is obviously tedious – you can’t wildcard and blocking the root domain doesn’t block sub-domains. In order to get rid of all Facebook servers (just the obvious ones) takes over ten entries, all of which need to now be repeated for IPv6.

At this point any rational person would conclude that this is not a sane thing to be doing. Obviously it’s time to be running my own DNS server and sinkhole and shitcanning domains with wildcards!

Fortunately there are still plenty of people on the internet who haven’t given up, for example, Pi-hole. By installing Pi-hole on a Raspberry PI hanging off the back of my router, and updating clients to use it as a DNS, i have a place where it is possible to wildcard block entire domains.

As a well as providing DNS Pi-hole also maintains a (partial) list of domains that serve ads. This means that devices on your home network that aren’t running ad blocking now has a good chance of not being served ads. This was a partially solved problem, as the Raspberry PI also runs Privoxy  which also blocks a good percentage of ads.

As an aside, the war between ad blockers and ad pushers has been quietly escalating and i’ve been starting to notice that a few news sites are managing to execute Javascript that blocks uBlock Origin. Sites that employ such measures are still blocked from displaying ads by Pi-hole and / or Privoxy.

While installing Pi-hole it was necessary to make some decisions about what to use as a DNS authority. There are some obvious answers like 8.8.8.8 (Google), 9.9.9.9 (IBM and some shady law enforcement types), OpenDNS, OpenNIC, etc. None of which seem ideal.

You probably won’t be surprised to hear that all your DNS queries are sent, unencrypted, over port 53. Which initially sounds like a really bad thing – it would provide your ISP with an easy way to know every site that you looked up. However, in all likelihood they aren’t doing that… mostly because they have stronger, government mandated, requirements to meet, such as tracking every site that you actually visit and when you visited it, not just the ones that you happen to lookup, and then subsequently visit via a cached lookup. If all you had to do was run your own DNS to avoid tracking… yeah, not going to happen.

Despite the above rational, there exists a parallel DNS infrastructure called DNSCrypt, mostly volunteer run, that proxies encrypted access to DNS. Assuming that you can trust that they aren’t logging (something you’re already doing with the DNS providers listed above…) then you can effectively block any visibility of your DNS activity to your ISP… not that they’ll care. If your traffic isn’t leaving your machine via an encrypted tunnel (think VPN, Tor, etc) then you can assume that it is being inspected and logged at the packet level.

In terms of increasing privacy DNSCrypt doesn’t seem to offer very much. It does offer some other protections against DNS spoofing attacks, but i’m not sure how widespread those are in the wild. I’d also guess that the other major providers of DNS are taking countermeasures as they are needed… and are maybe more effective than the volunteer force behind DNSCrypt.

I’ll probably end up installing the dnscrypt-proxy on the Raspberry PI and using it as the resolver for Pi-hole. In the end it’s just going to be an encrypted proxy for OpenNIC, which if given a choice is where i’d want my DNS to be resolved.

I’d recommend looking into Pi-hole it’s a really nice of tools to have a better understanding and control of what devices on your network are actually doing. Oh, and keep in mind that IPv6 is now a thing, running in parallel to the IPv4 internet for which you probably had some reasonable mental model… learning about RA, SLAAC and it’s Privacy Extensions) DAD, etc. was an eye opener for me!

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