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DNSCrypt

DNSCrypt offers a way to protect clients against attacks related to the modification and manipulation of DNS traffic — The main objective of DNSCrypt is authentication of the communication channel between the client (you) and a resolver supporting the protocol — This will protect the client from man in the middle attacks. In addition, encryption of DNS communication improves the client's privacy. DNSCrypt is the client-side version of dnscrypt-wrapper.

The dnscrypt-proxy client project is maintained by Frank Denis jedisct1

DNSCrypt verifies that responses you get from a DNS provider have been actually sent by that provider, and haven't been tampered with.

This is not a VPN. It doesn't mask your IP address, and if you are using it with a public DNS service, be aware that it will (and has to) decrypt your queries.

If you are using it for privacy, it might do the opposite of what you are trying to achieve. If you are using it to prevent VPN "leaks", this isn't the right tool either: the proper way to prevent VPN "leaks" is to avoid sending data to yet another third party: use a VPN service that operates its own DNS resolvers.

Installation

dnscrypt-proxy and libsodium is in the official repository for Chaos Calmer 15.05-rc3 and up.

# opkg update # opkg install dnscrypt-proxy # opkg install libsodium

  • If installed skip to configuration.
  • If somehow you can't install it that way, proceed with the following instructions.

**OLD** Installation on ar71xx platforms

The OpenWrt package for ar71xx is maintained by black-roland

This will install dnscrypt-proxy as well as any dependent libraries such as libsodium

Add third-party source to your opkg configuration file /etc/opkg.conf according to your OpenWRT version:

Barrier Breaker:

src/gz exopenwrt http://exopenwrt.and.in.net/barrier_breaker/ar71xx/packages/exOpenWrt

Attitude Adjustment:

src/gz exopenwrt http://exopenwrt.and.in.net/attitude_adjustment/ar71xx/packages

trunk:

src/gz exopenwrt http://exopenwrt.and.in.net/trunk/ar71xx/packages/exOpenWrt

And proceed with the installation itself:

$ opkg update
$ opkg install dnscrypt-proxy

Forum thread

**OLD** <del>Installation on x86 platforms</del>

The OpenWrt package for x86 is maintained by damianorenfer

If not already done, install the CACert SSL certificates :

root@OpenWrt:~# mkdir -p /etc/ssl/certs/
root@OpenWrt:~# wget -P /etc/ssl/certs/ http://curl.haxx.se/ca/cacert.pem

As DNSCrypt depends on libsodium, install it :

root@OpenWrt:~# cd /tmp
root@OpenWrt:~# curl -OL --cacert /etc/ssl/certs/cacert.pem https://github.com/damianorenfer/libsodium-openwrt/raw/master/openwrt/bin/x86/libsodium_0.4.5-1_x86.ipk
root@OpenWrt:~# opkg install libsodium_0.4.5-1_x86.ipk
root@OpenWrt:~# rm -f libsodium*.ipk

Then get the dnscrypt-proxy package from GitHub :

root@OpenWrt:~# cd /tmp
root@OpenWrt:~# curl -OL --cacert /etc/ssl/certs/cacert.pem https://github.com/damianorenfer/dnscrypt-proxy-openwrt/raw/master/bin/x86/packages/dnscrypt-proxy_1.4.0-1_x86.ipk
root@OpenWrt:~# opkg install dnscrypt-proxy_1.4.0-1_x86.ipk
root@OpenWrt:~# rm -f dnscrypt-proxy*.ipk

You can then follow the configuration section below. But default port is 5353 and NOT 2053! Change it in /etc/config/dnscrypt-proxy if needed.

Note : this is only for x86 systems, but if you have some OpenWrt knowledge you can compile the packages for your platform. Procedure briefly described at https://github.com/damianorenfer/dnscrypt-proxy-openwrt

Configuration

DNSCrypt is listening on address and port: 127.0.0.1:2053. We need to set OpenWRT to send DNS request to that address.

Server configuration

dnscrypt-proxy

The config file /etc/config/dnscrypt-proxy is simple and should be edited according to your needs. Possible values for the 'resolver' option are the first column in the list of public DNSCrypt resolvers.

config dnscrypt-proxy option address '127.0.0.1' option port '2053' # option resolver 'opendns' # option resolvers_list '/usr/share/dnscrypt-proxy/dnscrypt-resolvers.csv' # option ephemeral_keys '1'

Description:

Name Type Required Default Description
address string yes 127.0.0.1 The IP address of the proxy server.
port string yes 2053 Listening port for DNS queries.
resolver string no opendns DNS service for resolving queries. You can't add more than one resolver.
resolvers_list string no /usr/share/dnscrypt-proxy/dnscrypt-resolvers.csv Location of CSV file containing list of resolvers.
ephemeral_keys boolean no 0 Improve privacy by using an ephemeral public key for each query. Recommended if you are not using your own server.

If you need to specify other options, you will have to edit the /etc/init.d/dnscrypt-proxy script.

Note: I've had a little bit of confusion at setup, so I want to remind you; address and port strings are for local proxy server, you just have to pick a dnscrypt server from the resolvers list, put its name in resolver string and comment out resolvers and resolvers list settings.

Now we will start DNSCrypt and enable auto boot for it:

/etc/init.d/dnscrypt-proxy enable
/etc/init.d/dnscrypt-proxy start

Note: If dnscrypt-proxy is not starting after a router reboot, it may be trying to start before the network interface is fully up. Add the following to /etc/rc.local, above the line "exit 0":

sleep 10
/etc/init.d/dnscrypt-proxy start

dnsmasq

Assuming you are using dnsmasq, edit the bold lines in /etc/config/dhcp

config dnsmasq option domainneeded 1 option boguspriv 1 option filterwin2k 0 option localise_queries 1 option rebind_protection 1 option rebind_localhost 1 option local '/lan/' option domain 'lan' option expandhosts 1 option nonegcache 0 option authoritative 1 option readethers 1 option leasefile '/tmp/dhcp.leases' # option resolvfile '/tmp/resolv.conf.auto' option noresolv 1 list server '127.0.0.1#2053' list server '/pool.ntp.org/208.67.222.222' # list server '208.67.222.222' # list server '208.67.220.220'
  • We have disabled /tmp/resolv.conf.auto file since it instruct dnsmasq to use your ISP's DNS.
  • noresolv option also disables /etc/resolv.conf file for similar reason.
  • 127.0.0.1#2053 is the DNSCrypt address.
  • /pool.ntp.org/208.67.222.222 adds an exception for pool.ntp.org, which will be resolved through the standard unencrypted DNS channel. DNSCrypt requires precise time, otherwise it will not resolve any domain, including pool.ntp.org. So if your device's time was incorrect, it could never update its time, and therefore DNSCrypt would never work. So we set this exception so that pool.ntp.org queries will always bypass DNSCrypt and resolve with the standard unencrypted OpenDNS method.

Reboot router or restart dnsmasq for the changes to take effect.

/etc/init.d/dnsmasq restart

Client configuration

Note: you may need admin privileges to run the commands below.

Linux

sudo /etc/init.d/nscd restart

or

sudo /etc/init.d/networking restart

Windows

ipconfig /flushdns

Mac OS X

  • Mac OSX 10.4 (Tiger)
    • lookupd -flushcache
  • Mac OSX 10.5/10.6 (Leopard/Snow Leopard)
    • dscacheutil -flushcache

Troubleshooting

How to check what features are supported by your resolver

  1. The DNS randomness test will show the actual IP of your DNS. You can check here if the IP is associated with the service you are using (put the IP in the search field).
  2. DNSSEC resolver test determines whether your DNS resolver validates DNSSEC signatures.
  3. If you can access DNSCrypt.bit, your resolver can resolve domain names using Namecoin.

How to check if your DNS queries are using dnscrypt

On the router:

pkill -STOP dnscrypt-proxy

DNS resolution should not work any more.

To restore service, unfreeze the client proxy:

pkill -CONT dnscrypt-proxy

How to check if dnscrypt-proxy is set up and running

The easy way is to look in the log.

  1. Check if dnsmasq is using only dnscrypt. Only the last block of logged nameservers is relevant.
    • logread | grep -n "using nameserver"
    • 132:Jan  1 01:01:00 openwrt daemon.info dnsmasq[1883]: using nameserver 208.67.222.222#53 for domain pool.ntp.org
      133:Jan  1 01:01:00 openwrt daemon.info dnsmasq[1883]: using nameserver 127.0.0.1#2053
  2. Check that dnscrypt-proxy is working.
    • logread | grep "Proxying from"
    • Jul 1 12:00:00 openwrt daemon.info dnscrypt-proxy[1831]: Proxying from 127.0.0.1:2053 to 208.67.220.220:443

Suspicious certificate received

A "suspicious" certificate can reported be reported:

root@OpenWrtRouter:/tmp# ./dnscrypt-proxy -R dnscrypt.eu-nl -a 127.0.0.1:2053 [INFO] Generating a new key pair [INFO] Done [ERROR] Suspicious certificate received [ERROR] No useable certificates found [INFO] Refetching server certificates [ERROR] Suspicious certificate received [ERROR] No useable certificates found

Check the date and time on your router: this kind of behavior is usually caused by a system clock that hasn't been set properly.

Notes

inbox/dnscrypt.txt · Last modified: 2015/08/18 18:39 by Artyom