Abhay Rana aka Nemo

Migrating DNSCrypt Server to Docker

I’ve been running a personal DNSCrypt server in Bangalore for the last 2 years. When I set it up, it was just a compiled version of dnscrypt-wrapper, which was the bare minimum setup I could do.

Since then, I’ve upgraded it to a distribution supported version, but recent changes in dnscrypt key rotation, I’ve been wanting to setup something automated as well.

The easiest way was to switch to the official DNSCrypt Docker image, which does both key generation and certificate rotation. Since my public key was already present in the DNSCrypt Server lists, I was not too keen to regenerate a new key.

The primary challenge was ensuring that the docker container picks up my existing keys without trying to generate new ones from scratch. It was basically 2 steps:

  1. Match the directory structure that the container expects.
  2. Invoke the container directly into start mode while passing existing keys.

Directory Structure

I copied my keys (public.key, secret.key) to /etc/dnscrypt-keys and ran the following:

echo 2.dnscrypt-cert.captnemo.in > provider_name
touch provider_info.txt # I couldn't figure out how to output the same info, so kept it blank
hexdump -ve '1/1 "%.2x"' < public.key > public.key.txt

Then I ensured that the file permissions are matching what the container expects:

chmod 640 secret.key
chmod 644 public.key
chown root:1002 public.key secret.key
chmod 644 provider_name

This is how the final permissions looked for the directory (/etc/dnscrypt-keys)

-rw-r-----   1 root 1002    64 May 18 07:15 secret.key
-rw-r--r--   1 root 1002    32 May 18 07:15 public.key
-rw-r--r--   1 root root    28 May 18 07:19 provider_name
-rw-r--r--   1 root root     0 May 18 07:23 provider_info.txt
-rw-r--r--   1 root root    64 May 18 07:25 public.key.txt
drwxr-xr-x   2 root root  4096 May 18 07:26 .

Running the Container

Then, I directly ran dnscrypt-wrapper container:

docker run --detatched --restart=unless-stopped --volume /etc/dnscrypt-keys:/opt/dnscrypt-wrapper/etc/keys --publish --publish jedisct1/dnscrypt-server start

I pass a host path mount instead of creating a Docker Volume, since they can get deleted in regular docker prune.

Here, is the “Anchor IP”, which Digital Ocean internally maps to my Floating IP.

The container comes up, generates new short-term keys and goes live:

Starting DNSCrypt service for provider:
Starting pre-service scripts in /etc/runit_init.d
setup in directory /opt/unbound/etc/unbound
generating unbound_server.key
Generating RSA private key, 3072 bit long modulus (2 primes)
e is 65537 (0x010001)
generating unbound_control.key
Generating RSA private key, 3072 bit long modulus (2 primes)
e is 65537 (0x010001)
create unbound_server.pem (self signed certificate)
create unbound_control.pem (signed client certificate)
Signature ok
subject=CN = unbound-control
Getting CA Private Key
Setup success. Certificates created. Enable in unbound.conf file to use
ok: run: unbound: (pid 28) 300s
ok: run: dnscrypt-wrapper: (pid 31) 300s
ok: run: unbound: (pid 28) 600s
ok: run: dnscrypt-wrapper: (pid 31) 600s

Once the server was up, I verified connectivity with dnscrypt-proxy and it worked perfectly.

Stripping Audible DRM

Self-Guide for stripping the Audible DRM, in similar vain as my Kindle Self-Guide.

  1. Download the aax file from Audible website.
  2. Run the inAudible-NG Rainbrow crack table against the AAX file.

Easiest way is via docker:

cd ~/Music/Audiobooks
docker run -v $(pwd):/data ryanfb/inaudible

The cool part about this is that the entire activation is done offline, and runs a Rainbow Table attack against the Audible DRM.

The docker image checksum is sha256:2f8dd34cdc3c97e85b0acfe98cb777df2db6046d0c796ae6ec982af95c51aae1 as of my last use.


Kindle Hacks, A Self-guide

I run a non-standard Kindle configuration:

  1. Jailbroken (because I want to own the device, not rent it)
  2. Runs KOReader (because I want to read EPUBs and PDFs with reflow.)
  3. DRM Stripping (because I want to own the book, not rent it)

Since I don’t do any of these often enough to automate it, this is a self guide to help me follow these steps the next time I have to do any of this. No guarantees of this being helpful to anyone else but me.


The lifehacker guide on how to jailbreak your kindle is a good starting point [archived]. The mobileread forums have the definitive guides. Also see this FAQ on the mobileread wiki.

(Most of these only cover modern paperwhite kindles)

Maintaining the Jailbreak

Sometimes, Kindle firmware updates will stop the Jailbreak. Search for your firmware on mobileread forums. See this link for the 5.8 series.

Copy the .bin file to your kindle root directory and trigger a manual firmware update. That should reboot and re-affirm the jailbreak. To trigger a manual firmware update, go to the Kindle Menu and click “Update”. If it is greyed out, check if the file was copied correctly, and try rebooting.


Once you have a jailbreak, the rest is mostly installing packages via MRPI. I keep a ready directory of packages I can copy as-is to my Kindle. The current listing is at https://paste.ubuntu.com/p/CXS5hYZdqc/ with most of it just being koreader.

koreader is a FOSS document viewer for E Ink devices that supports Kindle, Kobo, PocketBook, Ubuntu Touch and Android devices.

The primary 2 packages are:

  • Update_KUALBooklet_v2.7_install.bin
  • update_kpvbooklet_0.6.6_install.bin

Run ;log mrpi via search after copying them to re-install them if needed.


Download the latest release from GitHub.

You should download the kindle5-linux-gnueabi package for modern Paperwhites. Unzip it to the copy directory mentioned above.

Aside: koreader has a linux appimage version for desktops, which I package for AUR.

DRM Related Stuff

DRM is inherently bad for users. If I switch my Ebook reader from Kindle (which are great as of today) to a Kobo tomorrow, I want my content to stay with me.

There are much better websites that explain the issues with DRM, so go visit: fckdrm.com, DefectiveByDesign.org, or EFF/drm.

The primary tool for stripping DRM from Kindle books is apprenticeharper’s DeDRM Repo which works as a Calibre Plugin.

Getting the Key

My current key is saved in pass:

pass show Keys/Kindle.k4i |jq

Save it in a file, which you can import to Calibre.

If you don’t have the key or if the above isn’t valid, see this comment on r/ebooks [archived].

Importing the Key

At the bottom-left of the plugin’s customization dialog, you will see a button labeled “Import Existing Keyfiles”. Use this button to import existing ‘.k4i’ key files. Key files might come from being exported from this plugin, or may have been generated using the kindlekey.pyw script running under Wine on Linux systems.

I once did some trickery on the kindlekey.pyw application to get it working on my system, but I didn’t take notes. If I ever do this again - AUTOMATE THIS.

Stripping DRM

Stripping DRM for any medium is always a cat-and-mouse game. Amazon keeps changing the DRM format in every Kindle firmware update, which is why the recommended method is to use a known/older version of the Kindle for Mac/PC Application as your source.

Note: The 1.24.3 release does not work on Linux. If you’re on Linux, you must instead download the 1.17.0 release instead (sha256=14e0f0053f1276c0c7c446892dc170344f707fbfe99b6951762c120144163200).

  1. Install Kindle for PC. It does work on Wine. Make sure you download 1.24.3 (51068). I trust filehippo for this. The sha256sum for the installer is c7a1a93763d102bca0fed9c16799789ae18c3322b1b3bdfbe8c00422c32f83d7.
  2. Install then launch it, and download the book.
  3. Go to ~/Documents/My Kindle Content
  4. Find book by Last Modified Date.
  5. Run calibredb add book.azw. If all goes well, the book should show up in your library, and you should be able to convert it.

Reference Files

I have a backup of my current Kindle files at http://ge.tt/75zk4Dv2 in case you need any of the files mentioned above. Checksums for the files are below, since ge.tt doesn’t believe in HTTPS:

e3b05193ed9d0b482f01dfb550eba67f3b113b5165aae5632379cf35fec2f59d  copy.tar.gz
14e0f0053f1276c0c7c446892dc170344f707fbfe99b6951762c120144163200  KindleForPC-installer-1.17.44170.exe
c7a1a93763d102bca0fed9c16799789ae18c3322b1b3bdfbe8c00422c32f83d7  KindleForPC-installer-1.24.51068.exe
50bb0e5d9c03bcb79b17c1b7063cefd2c947a9d1c4392814e6ec05225296472a  kual-helper-0.5.N.zip
39352b4b68993680f06d5ecc57ce7ec4c271b6b5f2386ea998027420c45f2acd  KUAL-KDK-1.0.azw2
ceb207ee4c8d3674f308ff91432aeabf213b203571e270f70b8ae218df6ded7d  KUAL-KDK-2.0.azw2
fce02f0e104e846f1e4cc0e029500c5a722614d63a47035d78ea4cf59f67a448  kual-mrinstaller-1.6.N.zip
4a6de1fafe47ec0e3bfb529edead401c92e66b00697d507abe945679b3b7bc65  KUAL-v2.7.zip
253d0b00b31d62ef9dadb7ca88b98e2718cb35246816b3c50dd63c0a7ef28a52  Update_jailbreak_hotfix_1.14_5.8.10_install.bin
cc63ba1b454d1f32492c835f108ee04aaa80e6e7a95f12b7216c2c015daa2fbc  Update_jailbreak_hotfix_1.14_nomax_install.bin