DoH no!

As was entirely predictable DNS-over-HTTPS has now been implicated in a spam campaign. Google DoH instance was used to access TXT records to control the spam campaign via a bit of javascript on web pages. This isn’t a weakness in DNS or for that matter in DoH, it’s just using Googles DoH as a side channel. They could have achieved the same thing by accessing a specific web page, but that would be more easily blocked or shut down. There are also mobile application, both IOS and android, that are using DoH by default without giving the user a choice in the matter*. At this point if you use DNS as part of your security posture – either via RPZ, pi-hole or some other mechanism ( and if you aren’t you really should ) then you need to be blocking DoH. At present there are over 70 advertised public DoH… Continue reading

RPZs a personal history

Ten years ago today at a “secure off site meeting” ( i.e. in the pub ) I asked a colleague if there was any reason why we couldn’t use DNS load balancers to “load balance” bad domains to an address of our choosing. After some thought there didn’t seem to be any reason why we couldn’t do it or why it wouldn’t work. So the next morning as it still seemed like a good idea we added load balancing rules for three choice domains with less than savoury reputation. This quickly proved to be quite a successful tactic so we dubbed it “the naughty step”, and assumed that as it was such an “obvious” thing to do loads of other people must also be doing it. After we’d been going on like this for a while Paul Vixie published his excellent article on taking back DNS, which gave us a… Continue reading

Cloudflare DoH!

This is a follow up to my previous article “Some problems with DoH!“. Given that Cloudflare are the preferred partner of Mozilla who are threatening to impose DNS-over-HTTPS on the majority of people I thought it worth while to have a look at what they have to say for themselves. All of this information is taken from https://developers.cloudflare.com/1.1.1.1/ as it was on 14th August 2018 ( archive.org link ). Some of my commentary may verge on the pedantic*, but given the nature of what is being proposed I think a little** pedantry and cynicism is called for. I may be mainly asking cynical and paranoid questions, given the weasel words and behaviour we’ve all seen from other companies I think this is justified for someone selling themselves on privacy. Continue reading