Securing DNS Traffic in China


DNS poisoning is one of the most common cause of nuisance when accessing websites
that are outside this 1.4 billion-people Oriental country. So far, the best way to protect yourself from this trouble is to route all your DNS traffic through an encrypted channel, and the method I am going to introduce is DNSCrypt. There is not yet a standard for encrypted DNS, DNSCrypt is a project done by OpenDNS. According my experience, DNSCrypt is very reliable and robust, the cryptography of the protocol is called DNSCurve, which is a public-key crypto that employes an extremely strong elliptic-curve cryptography called Curve25519.

If you have read my previous writing, you should know my setup is a Raspberry Pi, and so the rest of this article is based on that, running Raspbian. Dnsmasq will be used as the first DNS caching proxy to serve incoming DNS queries from machines on the network. If the queried domain name is a China one, the request will be served by a China DNS. This is necessary because for some domains, answers from DNS servers in China and global ones could be different. If the requested domain does not belong to any known China domains, the request will be forwarded to dnscrypt-proxy, which will ask a DNSCrypt server for an answer.

After DNSCrypt is used, your DNS traffic will look like this:

Setting up DNSCrypt

As illustrated in the above diagram, dnscrypt-proxy is the piece of software that handles DNSCrypt, but it is not available in Raspbian’s Wheezy and Jessie releases, only in testing (currently Stretch). You can either compile it yourself, or grab the debian package I built and install it. You can find the package here. It is based on the Raspbian package in testing repo, with some modification to debian packaging files, since the one in testing depends on systemd, which had not yet been adopted when Wheezy was released.

If you really want to build the package yourself, first install the libsodium packages. The package are also not available in Wheezy repo but the ones from testing, libsodium13_1.0.3-1_armhf.deb and libsodium-dev_1.0.3-1_armhf.deb, can be installed without any problem. Download and install them, then follow these steps to build your dnscrypt-proxy package:

After dnscrypt-proxy is installed, you have to update the port it uses. Change DNSCRYPT_PROXY_LOCAL_ADDRESS in /etc/default/dnscrypt-proxy to another port other than 53 (as it will be used by dnsmasq later), like this:

You can also change the remote DNSCrypt server, but since the default (cisco) works well for me, I left it unchanged.

Now test it to make sure it works as expected:

Setting up dnsmasq

Dnsmasq is very common and is available in Raspbian, installing it is easy:

Now we have to do some configuration in /etc/dnsmasq.conf. These are my recommended settings. Please note that the interface option is the network interface that dnsmasq will serve, and in my case that is wlan0. You have to change it to the one that applies to your case.

Now comes the interesting part. We are going to tell dnsmasq to use a China DNS server ( in my example) for China domains and DNSCrypt server for all others. This is done by using the server option in /etc/dnsmasq.conf. Here is an example:

This is pretty straightforward. The last line tells dnsmasq to use your dnscrypt proxy if the domain you query does not match any China domains. In my config file there are 12238 lines for China domains so I’m not going to post them all here, you can get the snippet of my dnsmasq.conf here, and put it into your own dnsmasq.conf. The problem is to maintain the list for all China hosts. I am now using the list from the fqrouter project, it has been serving me well, since most common domains are already there. What’s worrying is due to the abandon of the project by it’s author, the list is now unmaintained. If you know a more updated list, please let me know!

Debian 哀悼 Ian Murdock 離世 上發佈了 Ian Murdock 的死訊,由於對 Ian 十分敬佩,看到之後立馬把它翻譯過來,本來已經在上月31號翻好並發到 debian-publicity 郵件列表,可是不知什麼原因那邊一直沒收到(已經用了兩個不同的 email)。由於剛好那段時間在日本旅遊,也就沒太注意。今天打算再看看什麼問題的時候,發現 Anthony Fok 已經把另一篇由 Bootingman 翻譯的中文版放上網站,既然如此我也不好把它換掉。可是翻譯畢竟已經完成,而且還花了點心血,結果還算滿意,因此就在這公佈一下。


Ian Murdock 是一位自由/開源軟件的忠實擁護者、一名父親、兒子、以及 Debian 中的 ‘ian’,我們懷著沉重的心情,對 Ian 的離世致以深切哀悼。

Ian 於 1993 年 8 月啓動 Debian 計劃,並於同年不久推出首個版本。之後,Debian 逐漸成爲世界上的一個通用作業系統,無論從嵌入式設備,乃至國際太空站,皆能尋到它的蹤跡。

Ian 在創造 Debian 發行版與發展社羣文化時,無不專注於確保在道德層面,抑或技術層面,所做的事情都是正確的。譬如每個版本只會在最终完備時發佈,而 Debian 計劃對自由軟件的堅定立場,現已被視爲自由與開源領域的標準。

Ian 對於做正確事情的執著,使得他在 Debian 及往後的日子裏,一直朝向最美好的未來邁進。

Ian 的夢想猶在,Debian 社羣仍然非常活躍,上千的開發人員奉獻數不盡的日日夜夜,帶給世界一個穩定及安全的作業系統。

在這個傷痛的時刻,Debian 社羣眾人與 Ian 的家人心繫一起。他的家人亦請求各位,在這段艱難時期重視他們的私隱,我們對此表示尊重。各位來自 Debian 以及廣大 Linux 社羣的朋友,請將您們的慰問發送至,所有唁函將被永遠保存。

譯者:黃彥邦 (Anthony Wong)

Obfuscated SSH tunnel

VPN providers were cracked down, open source anti-censorship tools were eliminated. This is what’s happening in China and has become even more severe than ever. Shadowsocks alone is no longer reliable due to more powerful deep packet inspection implemented at the GFW.

I am now replacing shadowsocks on my gateway with obfuscated SSH tunnel, based on Tor‘s obfsproxy. To the impatient ones, I will first give a concise summary of the necessary steps of my set up. You can follow it without drilling down the details. I will explain in more details later. But please note that you have to follow the other instructions in this blog post to complete the whole set up.

Quick Set up

On your server

Assume your server runs Debian 8 (jessie) or Ubuntu, and its IP is, run these commands:

On Raspberry Pi gateway

Edit ~/.ssh/config:

Run these commands:

Boost WIFI Speed by Forcing 40 MHz Channels in hostapd on RPi

802.11n can double the channel bandwidth of 802.11g from 20 MHz to 40 MHz, but this operation mode is not recommended in areas that the spectrums are congested and likely interfere with existing WIFI and bluetooth devices. As a result, hostapd will not enable 40 MHz when it finds other channels are being used, like what is seen from the hostapd log below:

However, this is unrealistic in modern cities. You should be grateful the primary channel you choose has not been used already, let alone the additional one for 40 MHz. What can we do? We have to force hostapd to turn on 40 MHz anyway. But since hostapd does not have any configuration options for that, we have to recompile hostapd from source. Actually, this has been done in other distros. For example, OpenWRT and Arch has patched their hostapd with the noscan patch, which adds an option to force 40MHz mode regardless of the environment.

Before turning on 40 MHz, the iwconfig on my laptop is like this, notice the bit rate is only 54 Mb/s:

Now let us start. First you need to add a deb-src source to apt so that we can download source packages. Note that I am still using Raspbian Wheezy. If you use Jessie, change the deb-src line according to your original deb line.

Save the following patch into a file:

Because we are going to create a new hostapd package, it’d be a good practice to increment the version number by adding a new section at the top of debian/changelog, like this:

Now we are ready to compile the packages:

If it succeeds, install the new package with dpkg -i.

Restart hostapd, it should now force 40 MHz mode:

And my iwconfig output now shows Bit Rate is 150 Mb/s, yay!

Deploy Shadowsocks on Raspberry Pi with ChinaDNS and Redsocks

Assume you already have a Raspberry Pi configured as a WIFI router like mine shown below, but you live in China and have to deal with the fact that many websites can’t be accessed due to GFW. Don’t be despair and with some hacking you can get your Internet freedom back.


The mechanism is to use shadowsocks on your router which directs any traffic to a shadowsocks server in the free world. It’s simple to get it up and running on a local machine, but on a router you need to use redsocks to redirect traffic to the shadowsocks client running on your Raspberry Pi. DNS traffic has to be routed by redsocks as well otherwise your DNS replies will be contaminated. To remain as fast as normal when accessing China websites you also need to skip routing traffic to Redsocks for anything within the China IP ranges. Even if you don’t care about performance, this is still necessary in some circumstances like geoip restriction such as does not deliver contents if you live outside of China.

Finally, we want to improve the performance even further by using ChinaDNS. To avoid DNS poisoning, we can always resolve DNS over our secured shadowsocks connection, but this is not optimal if a China website have CDNs outside China. ChinaDNS queries local DNS servers to resolve Chinese domains and queries foreign DNS servers to resolve foreign domains, and from my testing it is useful to avoid DNS poisoning with the “DNS compression pointer mutation” option. (Update: I have switched from ChinaDNS to dnsmasq+dnscrypt, please read Securing DNS Traffic in China to see how it works.)


I assume that you have shadowsocks server running on a public server, so I will skip that part and only talk about the client side.

Installing shadowsocks is very simple, note that it will be installed under /usr/local/.

Start up shadowsocks while listening on local port 1080:


Install redsocks, simply apt-get from the archive:

Then you need to change the START option in /etc/default/redsocks from NO to YES, so that redsocks will start automatically at boot time and also can be started by sudo /etc/init.d/redsocks start:

Then update /etc/redsocks.conf. Most of the default settings work fine, just need to change local_ip in the redsocks section to your address of the network interface that accepts traffic from your local network. The default is, but that does not work well if you want to re-route traffic from other machines on your network, so change it to something like:

But we want traffic from other hosts in your network to be redirected by redsocks to your local shadowsocks client, which in turn sent to the the remote shadowsocks server. We need to pay special attention to DNS traffic, as DNS poisoning is prevalent in China. We need to take special care to redirect DNS traffic through redsocks/shadowsocks.

We also want all China traffic NOT to go through shadowsocks for performance. This can be easily done by looking at the destination IP, if it is in the China IP range we skip going through the REDSOCKS china. First we need to get all network segments allocated to China and save it to a file called chnroute.txt:

These all can be accomplished by iptables. You need to run the following iptables commands, or put them in a local script and run it with sudo.

Run iptables -t nat -L -n to make sure the rules have been added correctly. Now start up redsocks by sudo /etc/init.d/redsocks start and let’s test it out by doing some web browsing on another computer in your local network. If that works fine, congratulations and you have set up everything correctly! If not, look at shadowsocks output and also turn on redsock’s log_debug and check if there is anything useful in /var/log/daemon.log.


ChinaDNS is not absolutely necessary, but as explained at the beginning it is desirable. There is no pre-built package so we need to compile it. It is simple to do:

After it is successfully compiled, test it out:

If it goes well, run src/chinadns -m -c chnroute.txt when your router boots.

That’s it! I hope these are useful to you.

Update: I have switched from ChinaDNS to dnsmasq+dnscrypt, please read Securing DNS Traffic in China to see how to set it up.