Nunchuk Bitcoin WalletAs part of our Methodology, we ask:
Published code doesn’t help much if it is not what the published binary was built from. That is why we try to reproduce the binary. We
- obtain the binary from the provider
- compile the published source code using the published build instructions into a binary
- compare the two binaries
- we might spend some time working around issues that are easy to work around
If this fails, we might search if other revisions match or if we can deduct the source of the mismatch but generally consider it on the provider to provide the correct source code and build instructions to reproduce the build, so we usually open a ticket in their code repository.
In any case, the result is a discrepancy between the binary we can create and the binary we can find for download 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 binary 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 product 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 product 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.Show Older Reviews
The Analysis ¶
This does not represent a full code review.
The app’s version for Android was released as open source under the GPLv3 here.
It’s build instructions are:
- Follow the build instructions for Nunchuk Android Native SDK.
- Publish the SDK to the local maven. Note the SDK version number.
- Open dependencies.gradle and update nativeSdkVersion to the SDK version you just published.
- Build and run the app on your device.
So, what are the “build instructions for Nunchuk Android Native SDK”? First of all, Xcode is required. That’s a bit of an issue for us, as all contributors who do builds do not have a Mac and Xcode only works on Mac. It’s not immediately clear if it really is required, so lets look further …
git submodule add --force -b main https://gitlab.com/nunchuck/libnunchuk.git
but the user nunchuck doesn’t exist on gitlab.com.
As Nunchuk Android’s code is on GitHub, we can guess the right repo might be nunchuk-io/libnunchuk.
Which is weird is that the repo’s git submodule also still points to GitLab, so the error is not only in the documentation.
Let’s try:
$ git clone https://github.com/nunchuk-io/nunchuk-android-nativesdk.git
$ cd nunchuk-android-nativesdk/
$ cat .gitmodules
[submodule "src/main/native/libnunchuk"]
path = src/main/native/libnunchuk
url = https://gitlab.com/nunchuck/libnunchuk.git
branch = main
$ git submodule update --init --recursive
Submodule 'src/main/native/libnunchuk' (https://gitlab.com/nunchuck/libnunchuk.git) registered for path 'src/main/native/libnunchuk'
Cloning into '/home/leo/tmp/nunchuk-android-nativesdk/src/main/native/libnunchuk'...
Username for 'https://gitlab.com':
This repo isn’t a public repo but as it might be private, git asks for a login. As discussed above, we’ll use libnunchuk from GitHub:
$ git submodule set-url src/main/native/libnunchuk https://github.com/nunchuk-io/libnunchuk.git
$ git submodule update --init --recursive
Cloning into '/home/leo/tmp/nunchuk-android-nativesdk/src/main/native/libnunchuk'...
Submodule path 'src/main/native/libnunchuk': checked out 'c168cf715cbe768b5cd5004609f2db6d0ebfe254'
...
error: object e35e28f52d20df27561b2780f6b9c86669a9de21: zeroPaddedFilemode: contains zero-padded file modes
fatal: fsck error in packed object
fatal: index-pack failed
fatal: clone of 'https://github.com/sqlcipher/sqlcipher' into submodule path '/home/leo/tmp/nunchuk-android-nativesdk/src/main/native/libnunchuk/contrib/sqlcipher' failed
Failed to clone 'contrib/sqlcipher'. Retry scheduled
So … we can’t clone that dependency. Seriously?
$ git clone https://github.com/sqlcipher/sqlcipher
Cloning into 'sqlcipher'...
remote: Enumerating objects: 15498, done.
remote: Counting objects: 100% (1910/1910), done.
remote: Compressing objects: 100% (816/816), done.
error: object e35e28f52d20df27561b2780f6b9c86669a9de21: zeroPaddedFilemode: contains zero-padded file modes
fatal: fsck error in packed object
fatal: index-pack failed
So for now we give up at this point and file this product as not verifiable.
Update 2023-01-06: As laid out in this issue, we managed to compile the app but with substantial differences:
Files ./GooglePlay/classes2.dex and ./LocalBuild/classes2.dex differ
Files ./GooglePlay/classes3.dex and ./LocalBuild/classes3.dex differ
Files ./GooglePlay/classes4.dex and ./LocalBuild/classes4.dex differ
Files ./GooglePlay/classes5.dex and ./LocalBuild/classes5.dex differ
Files ./GooglePlay/classes.dex and ./LocalBuild/classes.dex differ
Files ./GooglePlay/lib/arm64-v8a/libnunchuk-android.so and ./LocalBuild/lib/arm64-v8a/libnunchuk-android.so differ
Until these issues are resolved, the app is not verifiable.
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.
If you find something we should include, you can create an issue or edit this analysis yourself and create a merge request for your changes.