Joachim Breitner's Homepage

I am a incorrigibly in picking non-mainstream, open smartphones, and then struggling hard. Back then in 2008, I tried to use the OpenMoko FreeRunner, but eventually gave up because of hardware glitches and reverted to my good old Siemens S35. It was not that I would not be willing to put up with inconveniences, but as soon as it makes live more difficult for the people I communicate with, it becomes hard to sustain.

Two years ago I tried again, and got myself a Jolla phone, running Sailfish OS. Things are much nicer now: The hardware is mature, battery live is good, and the Android compatibility layer enables me to run many important apps that are hard to replace, especially the Deutsche Bahn Navigator and various messengers, namely Telegram, Facebook Messenger, Threema and GroupMe.

Some apps that require Google Play Services, which provides a bunch of common tasks and usually comes with the Google Play store would not run on my phone, as Google Play is not supported on Sailfish OS. So far, the most annoying ones of that sort were Uber and Lyft, making me pay for expensive taxis when others would ride cheaper, but I can live with that. I tried to install Google Play Services from shady sources, but it would regularly crash.

Signal on Jolla

Now in Philadelphia, people urged me to use the Signal messenger, and I was convinced by its support for good end-to-end crypto, while still supporting offline messages and allowing me to switch from my phone to my desktop and back during a conversation. The official Signal app uses Google Cloud Messaging (GCM, part of Google Play Services) to get push updates about new posts, and while I do not oppose this use of Google services (it really is just a ping without any metadata), this is a problem on Sailfish OS.

Luckily, the Signal client is open source, and someone created a “LibreSignal” edition that replaced the use of GCM with websockets, and indeed, this worked on my phone, and I could communicate.

Things were not ideal, though: I would often have to restart the app to get newly received messages; messages that I send via Signal Desktop would often not show up on the phone and, most severe, basically after every three messages, sending more messages from Desktop would stop working for my correspondents, which freaked them out. (Strangely it continued working from their phone app, so we coped for a while.)

So again, my choice of non-standard devices causes inconveniences to others. This, and the fact that the original authors of Signal and the maintainers of LibreSignal got into a fight that ended LibreSignal discontinued, meant that I have to change something about this situation. I was almost ready to give in and get myself a Samsung S7 or something boring of the sort, but then I decided to tackle this issue once more, following some of the more obscure instructions out there, trying to get vanilla Signal working on my phone. About a day later, I got it, and this is how I did it.

microG

So I need Google Play Services somehow, but installing the “real thing” did not seem to be very promising (I tried, and regularly got pop-ups telling me that Play Services has crashed.) But I found some references to a project called “microG”, which is an independent re-implementation of (some of) of the play services, in particular including GCM.

Installing microG itself was easy, as you can add their repository to F-Droid. I installed the core services, the services framework and the fake store apps. If this had been all that was to do, things would be easy!

Play Store detection work arounds

But Signal would still complain about the lack of Google Play Services. It asks Android if an app with a certain name is installed, and would refuse to work if this app does not exist. For some reason, the microG apps cannot just have the names of the “real” Google apps.

There seem to be two ways of working around this: Patching Signal, or enabling Signature Spoofing.

The initially most promising instructions (which are in a README in a tarball on a fishy file hoster linked from an answer on the Jolla support forum…) suggested patching Signal, and actually came both with a version of an app called “Lucky Patcher” as well as a patched Android package, but both about two years old. I tried a recent version of the Lucky Patcher, but it failed to patch the current version of Signal.

Signature Spoofing

So on to Signature Spoofing. This is a feature of some non-standard Android builds that allow apps (such as microG) to fake the existence of other apps (the Play Store), and is recommended by the microG project. Sailfish OS’s Android compatibility layer “Alien Dalvik” does not support it out of the box, but there is a tool “tingle” that adds this feature to existing Android systems. One just has to get the /system/framework/framework.jar file, put it into the input folder of this project, run python main.py, select 2, and copy the framework.jar from output/ back. Great.

Deodexing Alien Dalvik

Only that it only works on “deodexed” files. I did not know anything about odexed Android Java classes (and did not really want to know), but there was not way around. Following this explanation I gathered that one finds files foo.odex in the Android system folder, runs some tool on them to create a classes.dex file, and adds that to the corresponding foo.jar or foo.apk file, copies this back to the phone and deletes the foo.odex file.

The annoying this is that one does not only have to do it for framework.jar in order to please tingle, because if one does it to one odex file, one has to do to all! It seems that for people using Windows, the Universal Deodexer V5 seems to be a convenient tool, but I had to go more manually.

So I first fetched “smali”, compiled it using ./gradlew build. Then I fetched the folders /opt/alien/system/framework and /opt/alien/system/app from the phone (e.g. using scp). Keep a backup of these in case something breaks. Then I ran these commands (disclaimer: I fetched these from my bash history and slightly cleaned them up. This is not a fire-and-forget script! Use it when you know what it and you are doing):

cd framework
for file in *.odex
do
  java -jar ~/build/smali/baksmali/build/libs/baksmali.jar deodex $file -o out
  java -jar ~/build/smali/smali/build/libs/smali.jar a out -o classes.dex
  zip -u $(basename $file .odex).jar classes.dex
  rm -rf out classes.dex $file
done
cd ..

cd app
for file in *.odex
do
  java -jar ~/build/smali/baksmali/build/libs/baksmali.jar deodex -d ../framework $file -o out
  java -jar ~/build/smali/smali/build/libs/smali.jar a out -o classes.dex
  zip -u $(basename $file .odex).apk classes.dex
  rm -rf out classes.dex $file
done
cd ..

The resulting framework.jar can now be patched with tingle:

mv framework/framework.jar ~/build/tingle/input
cd ~/build/tingle
./main.py
# select 2
cd -
mv ~/build/tingle/output/framework.jar framework/framework.jar

Now I copy these framework and app folders back on my phone, and restart Dalvik:

devel-su systemctl restart aliendalvik.service

It might start a bit slower than usually, but eventually, all the Android apps should work as before.

The final bit that was missing in my case was that I had to reinstall Signal: If it is installed before microG is installed, it does not get permission to use GCM, and when it tries (while registering: After generating the keys) it just crashes. I copied /data/data/org.thoughtcrime.secretsms/ before removing Signal and moved it back after (with cp -a to preserve permissions) so that I could keep my history.

And now, it seems, vanilla Signal is working just fine on my Jolla phone!

What’s missing

Am I completely happy with Signal? No! An important feature that it is lacking is a way to get out all data (message history including media files) in a file format that can be read without Signal; e.g. YAML files or clean HTML code. I do want to be able to re-read some of the more interesting conversations when I am 74 or 75, and I doubt that there will be a Signal App, or even Android, then. I hope that this becomes available in time, maybe in the Desktop version.

I would also hope that pidgin gets support to the Signal protocol, so that I conveniently use one program for all my messaging needs on the desktop.

Finally it would be nice if my Signal identity was less tied to one phone number. I have a German and a US phone number, and would want to be reachable under both on all my clients. (If you want to contact me on Signal, use my US phone number.)

Alternatives

Could I have avoided this hassle by simply convincing people to use something other than Signal? Tricky, at the moment. Telegram (which works super reliable for me, and has a pidgin plugin) has dubious crypto and does not support crypto while using multiple clients. Threema has no desktop client that I know of. OTR on top of Jabber does not support offline messages. So nothing great seems to exist right now.

In the long run, the best bet seems to be OMEMO (which is, in essence, the Signal protocol) on top of Jabber. It is currently supported by one Android Jabber client (Conversations) and one Desktop application (gajim, via a plugin). I should keep an eye on pidgin support for OMEMO and other development around this.