Muun - Bitcoin and Lightning Wallet

3 minute read

Published:

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This app was first launched on 25th April 2017 and currently has more than 1000 downloads, a 4.4 stars rating from 51 users and the latest APK (version beta-37.4) was from 23rd January 2020.

Our analysis was done on 29th December 2019 based on data found in their Playstore description and their website and their source repository. We discuss the issue with verification with the provider here. In our GitLab this app is discussed in Issue #77.

We found these ways of contacting the developers:

Help spread awareness for build verifiability

Please help us spread the word, asking Muun - Bitcoin and Lightning Wallet to support verifiable builds via their Twitter!

Disclaimer

The following Analysis is not a full code review! We plan to make code reviews available in the future but even then it will never be a stamp of approval but rather a list of incidents and bad coding practice. We cannot find and tell you all the dark secrets the wallet providers might have.

Do your own research!

Try out searching for "lost bitcoins", "stole my money" or "scammers" together with the wallet's name, even if you think the wallet is generally trustworthy. For all the bigger wallets you will find accusations. Make sure you understand why they were made and if you are comfortable with the provider's reaction.

The Analysis

Update: The provider made clear that this app will remain non-reproducible:

esneider 16 hours ago: We have updated the instructions for building, and we won’t be producing reproducible builds for the time being.


The description starts out very clearly:

Muun is a non-custodial wallet: this means you are in full control of your money. You remain in control of your private keys, which are stored only on your device using your phone’s secure enclave. We never have access to your funds.

So it is non-custodial.

Also:

Our code is in an open source repository and can be audited by anyone on the Internet.

So … let’s see if we can find this open source because it is not referenced in the description itself.

Their link to GitHub on their website has the label “Audit us”. Perfect. That’s us!

This project “apollo” has the most promising description: “Muun android wallet”.

Ok, but where are the build instructions?

Let’s see …

$ git clone https://github.com/muun/apollo.git
$ cd apollo/
$ git submodule status 
$ git tag
$ git log --pretty=oneline --abbrev-commit
491d4d5 (HEAD -> master, origin/master, origin/HEAD) Release source code for beta-36.2
6facf35 Release source code for beta-36.1
5530b6e Release source code beta-34
f476a6f Release source code beta-33
c9a3697 Release source code beta-32
377b045 Release source code beta-29
7f3bd57 Release source code beta-28
cd3b46b Release source code for beta-26
548af69 Release source code for beta-25
913f517 Release source code for beta-24.1
bc2f4db Add license
8030bab Add readme
8f78e5f Apollo beta-16
a5d8782 Add .gitignore

That’s all their commits. No submodule. No tags. We need beta-36.2 which is the commit message of the final commit. That is good although not enough for the future.

root@288e8088ff9f:/mnt# yes | /opt/android/tools/bin/sdkmanager "build-tools;28.0.3"
root@288e8088ff9f:/mnt# ./gradlew bundleRelease
Configuration on demand is an incubating feature.
> Task :apollo:libwallet FAILED

FAILURE: Build failed with an exception.

* What went wrong:
Execution failed for task ':apollo:libwallet'.
> A problem occurred starting process 'command 'gomobile''

* Try:
Run with --stacktrace option to get the stack trace. Run with --info or --debug option to get more log output. Run with --scan to get full insights.

* Get more help at https://help.gradle.org

BUILD FAILED in 4s
1 actionable task: 1 executed

That’s all for now. Build fails with obscure error. No build instructions provided.

Our verdict: not verifiable.

Verdict Explained

Not verifiable: The provided Open Source Code could not be verified to match the app released on Google Play

This verdict means that the provider did share some source code but that we could not verify that this source code matches the released app. This might be due to the source being released later than the app or due to the provided instructions on how to compile the app not being sufficient or due to the provider excluding parts from the public source code. In any case, the result is a discrepancy between the app we can create and the app we can find on GooglePlay and any discrepancy might leak your backup to the server on purpose or by accident.

As we cannot verify that the source provided is the source the app was compiled from, this category is only slightly better than closed source but for now we have hope projects come around and fix verifiability issues.

The app cannot be independently verified. If the provider puts your funds at risk on purpose or by accident, you will probably not know about the issue before people start losing money. If the provider is more criminally inclined he might have collected all the backups of all the wallets, ready to be emptied at the press of a button. The app might have a formidable track record but out of distress or change in management turns out to be evil from some point on, with nobody outside ever knowing before it is too late.