mikaela.github.io/blog/_posts/2018-10-21-dnscrypt-proxy-quick-dirty-debian.md

DNSCrypt-proxy encrypts DNS queries that would otherwise go in plaintext ensuring that they won’t be seen or modified by anyone in the middle. It works as a localhost DNS server sending queries to configured DNS resolvers.

I guess I should also say why you would want dnscrypt v1 vs v2. V1 which is in most of repos currently uses broken resolver by default and only supports one resolver at a time, while v2 can use multiple of them while comparing them for the best ones.

This post is on getting v2 to Debian Stable and Ubuntu pre 18.10 which contain v1 and I (sadly) don’t know a better way to do this.

In order to check which version your distro has available, check the dnscrypt-proxy search page for your distribution:

• Debian
  • 2018-11-03: the version in stretch (stable) is 1.9.4-1 which has the issues why I wrote this post.
• Ubuntu
  • 2018-11-03: I cannot find dnscrypt-proxy from Ubuntu at all, while I am sure it previously had the Debian version 1.

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1. Update your local apt cache sudo apt update and install curl that will be used for downloading the package from Debian sudo apt-get install curl

Check the version number at Debian’s dnscrypt-proxy package download page and fix it below:

2: download the packagecurl -LO https://deb.debian.org/debian/pool/main/d/dnscrypt-proxy/dnscrypt-proxy_2.0.16-2_amd64.deb

WARNING: This part is not supported by either Debian or Ubuntu, you are taking a package from another distribution and attempting to install it on another.

WARNING: Usually when you use apt, it will verify package signatures and ensure that the package hasn’t been tampered with. I have no idea how to do that with direct downloads (if it’s even possible) so you will be trusting the Debian repository mirror or CDN blindly.

3. install the package you downloaded: sudo dpkg -i dnscrypt-proxy<TAB> (TAB (above capslock) automatically completes rest of the filename for you).
   1. In case there was a problem, attmept sudo apt-get install -f to fix broken package depedencies. Remember to check that what it suggests looks reasonable! If it asks to remove dnscrypt-proxy, you are out of luck and should do that instead of attempting to replace important system components from another distribution (creating “Frankendebian”).

Hopefully dnscrypt-proxy is now running, check journalctl -u dnscrypt-proxy, there should be a line saying [NOTICE] Wiring systemd TCP socket #0, dnscrypt-proxy.socket, 127.0.2.1:53

Edit /etc/NetworkManager/NetworkManager.conf to avoid overlapping resolvers breaking each other, it should say say dns=none e.g.:

[main]
plugins=ifupdown,keyfile
dns=none

if it doesn’t say dns=none, fix it and restart it with: systemctl restart NetworkManager

Edit your /etc/resolv.conf, for example:

sudo su -
rm /etc/resolv.conf
nano /etc/resolv.conf && chattr +i /etc/resolv.conf

chattr +i will prevent modifying the file unless chattr -i is done first.

Example resolv.conf:

nameserver 127.0.2.1
options edns0 single-request-reopen
#search mikaela.info

Nameserver is the host where dnscrypt-proxy said to be listening on in journalctl, options are from dnscrypt-proxy documentation and search means domains that are automatically searched for if you don’t use fully qualified domain names, e.g. ssh machine in my (uncommented) config would turn into ssh machine.mikaela.info. Update: I find this a privacy leakage (whenever NXDOMAIN happens), which is why I nowadays have it commented.

You should also tell dhclient to not touch resolv.conf or you may get many files into /etc beginning with names resolv.conf.dhclient-new. according to Debian wiki which gives the following two commands and Debian bug 860928:

echo 'make_resolv_conf() { :; }' > /etc/dhcp/dhclient-enter-hooks.d/leave_my_resolv_conf_alone
chmod 755 /etc/dhcp/dhclient-enter-hooks.d/leave_my_resolv_conf_alone

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WARNING from 2018-10-21! It appears that the cache and log directories of dnscrypt-proxy don’t sometimes get created automatically (at least on Debian GNU/Linux 9.6 (stretch).

If this happens to you or you would like to be sure to get them:

sudo mkdir -p /var/cache/dnscrypt-proxy/ /var/log/dnscrypt-proxy/
sudo chown -R _dnscrypt-proxy:nogroup /var/cache/dnscrypt-proxy /var/log/dnscrypt-proxy

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For the curious my dnscrypt-proxy config is in my shell-things repository mirror.

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2019-07-22 update

I have also started performing local DNSSEC validation by running Unbound in front of DNSCrypt-proxy, so my queries go resolv.conf -> Unbound -> dnscrypt-proxy -> configured resolvers. This has the advantage that if the resolver didn’t perform DNSSEC validation or lied about performing it, the protection by DNSSEC would still be received.

The steps are simple:

1. sudo apt install unbound
   • You should see a file /etc/unbound/unbound.conf.d/root-auto-trust-anchor-file.conf which simply says server: and on another line after intending auto-trust-anchor-file: "/var/lib/unbound/root.key" (the path varies by distribution) which means it’s performing DNSSEC validation with those trust anchors.
2. sudo nano /etc/unbound/unbound.conf.d/dnscrypt-proxy.conf

do-not-query-localhost: no
forward-zone:
    name: "."
    forward-addr: 127.0.2.1@53

3. sudo systemctl restart unbound
4. Ensure /etc/resolv.conf points to 127.0.0.1 and optionally ::1 instead of 127.0.2.1 where dnscrypt-proxy runs by default. For more details, CTRL + F for resolv.conf or chattr.