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Resolves: #149
Resolves: #145

It felt natural to me to merge these two posts in the end.
Mikaela Suomalainen 10 months ago
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layout: post
comments: true
title: "Android 9 Private DNS behaviour with 853 blocked & DoT server comparsion"
category: [english]
tags: [english, Android, DNS-over-TLS, DNS, security, privacy]

*Since I first heard of Android 9 Private DNS I wondered how it will work
when the port is blocked or there is a captive portal. I didn't find this
information anywhere and now that I have gotten the Android 9 Go update on
my Nokia 1, I am able to type my own blog post about it.*

* Phone: Nokia 1 (TA-1047) running Android 9 (Go Edition)
* I think I got the update on 9th of July
* Language: Finnish (and as I am typing in English
* In all tests mobile data was disabled to not cause confusing results.
* As Private DNS is technically DNS over TLS I am calling it as DoT.
* Enabled from Settings, Network & Internet, Advanced settings, Private DNS
* I am using []( as hostname.
* Automatic mode connects to the DNS server port 853 without validating
certificate, "Hostname of private DNS provider" (which I call as the
manual mode) also validates the certificate and disallows downgrading.
* [Google's documentation](
* [Intra]( detects when private DNS is enabled and
says that it doesn't have to be enabled at those times. However it gets
confused easily as between the metro and DHCP offering Quad9 it claimed
secure DNS was disabled. Later before the captive portal test Intra again
claimed DoT was disabled when there was no connectivity to DoT server, so
I guess it's only able to detect when Android is actually connected to the
DoT server.
* [My messy notes for making this post](

* * * * *

Test: automatic mode without DoT capable server from DHCP; the setting
says "automatic".

* * * * *

Test: DoT with port 853 blocked; Android reports that the WLAN network has
no internet connectivity until I disable private DNS and toggle WLAN. I
tested this in Helsinki metro.

* * * * *

Test: automatic mode with DoT capable server from DHCP; Android says that
DoT is "enabled". For this test I configured a WLAN AP to use [Quad9](
DNS servers `` and ``.

I would also have configured
the IPv6 addresses `2620:fe::9` and `2620:fe::fe` as the network was dualstack,
but naturally the router was missing ability to configure IPv6 DNS servers
and forced using the ISP ones. At least the Android 9 was happy with the IPv4

I didn't do this at home as my main network connectivity is a MiFi
"box" that doesn't allow me to specify a DNS server and I tend to avoid it anyway
by using [dnscrypt-proxy]( with [this config]( and Intra. Sadly I have some
little used devices that have no way to encrypt DNS and they either use the
ISP DNS or in case of Chromecasts I am under impression that they are
hardcoded to use Google DNS. I don't use them much though.

Why do I care about encrypted DNS so much? Encrypt everything! And to quote
my index:

> The only traffic I am not encrypting is probably my WLAN. For some reason my router requires a reboot once per hour with WPA2 encryption while on open network I only have to reboot it once per day (I have asked about this confusing behaviour from wiser people on IRC and they weren't able to explain it either). I support the <a href="">Open Wireless Movement</a> and think that if someone really wanted to cause me harm, they could break into the network anyway and that would be more difficult to prove on consumer grade device than the network being open. There are firewalls on all networks and while a passerby would be able to observe unencrypted SNIs, isn't that also <a href="">being done by international security agencies already</a> while even <a href="">Finland has given permission to monitor traffic crossing our borders</a> ((TODO: better link in English as the situation develops)and how much of traffic doesn't do that?). I also don't like being somewhere where the only available WLANs are printers and smart thermostats :)

* * * * *

Bonus test: DoT + DoH via the [Intra app](!/)
configured to use server `` in Helsinki
metro; Android claims that the network has no connectivity and shows the x
on the WLAN symbol in the statusbar, but everything works regardless.
My hypothesis that I am not enough interested in confirming is that if I was
using `` nothing would work as the Intra app
would have been unable to resolve that name due to DoT being blocked.

* * * * *

Test: DoT + Captive Portal; I get the captive portal prompt asking me to
login to the network as usual, so I guess Android handles captive portal
separately from DoT which is a good thing in my opinion as otherwise that
feature would likely be too confusing or difficult for many people to use.

I performed this test next to a closed Espresso House, which luckily hadn't
turned off their WLAN AP, but I treat SSIDs as free advertising anyway.

* * * * *

## Why I use Quad9?

I had an idea of blogging about this separately long before I got Android 9
and was able to perform this testing, but as I mention it so much I guess
it's better to merge the posts.

What I wish from a DNS server is privacy/security (including DoT), [DNSSEC],
being stable (or unlikely to go
away without warning in near future) and thus being able to recommend it to
my family members (read as: configure it on their routers while being tech


The options [judging by]( are the following:

* Quad9 (I am only talking about the secure variant as the insecure disables
* non-profit
* [privacy policy]( (I seem to have too much
problems with the others to even look at their policies)
* same malicious domain filtering for everyone (I was going to compare it
to Cisco/OpenDNS without realizing that the DoT requirement dropped them out
already) that I haven't yet encountered
* [FAQ](
* supports DNS over HTTPS (for Firefox which at the time of typing requires
DoH for ESNI support)
* has a node in Finland
* I have heard that they plan a network map (Adguard on the bottom has it)
* Cloudflare
* for-profit company
* too big for my taste and possibly getting even bigger if Firefox starts
sending DNS over HTTPS queries to them by default
* [PTIO discussion](
* [ critique](
* Google Public DNS
* same as Cloudflare, they are on my phone and many say Google to know you
better than you know yourself, so they areally don't need to know my DNS
queries too.
* CleanBrowsing
* I never looked it before, but it appears to be for-profit
* allows custom filters? What prevents filters from another user from
being applied to me? This was a problem with Cisco OpenDNS.
* Adguard
* I never looked at them before either, but they look surprisingly good
and I could consider using them with the short reading I did for this
* for-profit (even though they claim to make money by their other products
than DNS, but so do Cloudflare and Google?)
* I worry they could block something more than ads/malware by accident
* and I think they are more likely to do that than Quad9 due to blocking
so much more.
* and this could be painful to start troubleshooting over the phone
with family members.
* [privacy policy](
* based in Cyprus (EU)
* [Adguard DNS page including FAQ](
* no server in Finland

Then there are regional providers like:

* [TREX recursive name service]( for Finnish users
* "Our resolvers do not support DNS over TLS, DNS over HTTPS or dnscrypt. But TREX hosts a Quad9 node, which offers a secure service with those features."
* this can be confirmed by running a [DNS leak test](
which in Finland replies "TREX Regional Exchanges Oy" and being hosted
by TREX is a plus for Quad9 in my eyes as it's
* often recommended for Finnish users instead of Google DNS by people in
my circles
* [CZ.NIC Otevřené DNSSEC Validující Resolvery]( for Czech users
* has DNSSEC, DoT & DoH
* probably wouldn't make much sense to use from Finland
* (thus I promote centralization, but) a regional not-anycasted DNS server
may be impractical while traveling as your DNS would always go through
home and possibly be slower than it could be

And the golden option of hosting your own DNS. (It's actually easy with
Unbound, I haven't tried DoH/DoT hosting though!)

* Hosting where?
* Hosting with what money?
* On my laptop? What about when it goes down?
* On three of my active devices separately? I don't think the root
nameserver admins would be very happy if everyone did that.
* On my VPS? What if it went down due to being so cheap? What to say when
my family called that "the internet is broken"? How to provide the additional
line of defence against malware and phishing as well as Quad9 does it with
all their information sources and partners?

To me Quad9 seems the least bad (or the least scary?) option with all these
things considered, but some other provider may seem better to you.