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Muun - Bitcoin and Lightning Wallet

latest release: 46.10 ( 19th October 2021 ) last analysed  9th October 2021 Not reproducible from source provided 
4.6 ★★★★★
399 ratings
10 thousand
25th April 2017

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Older reviews (show 0 of 2 reproducible)

Help spread awareness for build reproducibility

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

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.

The Analysis 

Update 2021-10-09: We were approached about this verdict being wrong and while the provider hasn’t claimed a fix, we noticed we haven’t filed an issue about the tiny diff in the crashlytics.android.build_id neither. To see if this diff remains, we checked the latest version - 46.10.

As Muun - Bitcoin and Lightning Wallet was almost reproducible before, we want to keep track of their progress as new versions get released now, too. We had a look at their verification script. It builds the app from source and unzips both the file from Google and the built app to diff them.

Surprising is the actual check:

# Remove the signature since OSS users won't have Muuns private signing key
rm -r "$tmp"/{to_verify,baseline}/{META-INF,resources.arsc}

diff -r "$tmp/to_verify" "$tmp/baseline" && echo "Verification success!" || echo "Verification failed :("
  1. The first line is a comment, justifying the removal of the signature, which is valid.
  2. The second line deletes the META-INF folders which does indeed contain the signature but it may contain other stuff, too. In fact it does.
  3. It also deletes the files resources.arsc which has nothing to do with the signature. There is no justification for doing so.

We built our own verification script which gives us these results:

appId:          io.muun.apollo
signer:         026ae0ac859cc32adf2d4e7aa909daf902f40db0b4fe6138358026fd62836ad1
apkVersionName: 46.10
apkVersionCode: 610
appHash:        e7504467c314b576f5f0c45eeb135396f4d771f976e886bc9b0e1111f1172ff8
commit:         bf4fa4ced4a6d3f73f806a5a4b05a089aba92cb1

Only in /tmp/fromPlay_io.muun.apollo_610/META-INF: APOLLORE.RSA
Only in /tmp/fromPlay_io.muun.apollo_610/META-INF: APOLLORE.SF
Files /tmp/fromPlay_io.muun.apollo_610/META-INF/MANIFEST.MF and /tmp/fromBuild_io.muun.apollo_610/META-INF/MANIFEST.MF differ
Files /tmp/fromPlay_io.muun.apollo_610/resources.arsc and /tmp/fromBuild_io.muun.apollo_610/resources.arsc differ

Revision, tag (and its signature):
object bf4fa4ced4a6d3f73f806a5a4b05a089aba92cb1
type commit
tag v46.10
tagger acrespo <alvaro.andres.crespo@gmail.com> 1632343796 -0300


For our reproducible verdict the first three lines of the diff are fine. The last line though, the resources.arsc that their verification script explicitly ignores is not ok. This file contains resources and altering resources can significantly change the app, too. This app is not verifiable.

Upon closer inspection, the diff again is just the crashlytics.android.build_id:

$ apktool d -o apkGoogle Muun\ 46.10\ \(io.muun.apollo\).apk 
$ apktool d -o apkBuild apolloui-prod-release-unsigned.apk
$ diff --brief --recursive apkBuild apkGoogle
Files apkBuild/apktool.yml and apkGoogle/apktool.yml differ
Only in apkGoogle/original/META-INF: APOLLORE.RSA
Only in apkGoogle/original/META-INF: APOLLORE.SF
Files apkBuild/original/META-INF/MANIFEST.MF and apkGoogle/original/META-INF/MANIFEST.MF differ
Files apkBuild/res/values/strings.xml and apkGoogle/res/values/strings.xml differ
$ diff apkBuild/res/values/strings.xml apkGoogle/res/values/strings.xml
<     <string name="com.crashlytics.android.build_id">e0c37a103082460fbf95f3c097222e61</string>
>     <string name="com.crashlytics.android.build_id">95a3152a98594e8ca1324bdefd26a5b9</string>


Verdict Explained

We could not verify that the provided code matches the binary!

As part of our Methodology, we ask:

Is the published binary matching the published source code? If not, we tag it Unreproducible! 

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

  1. obtain the binary from the provider
  2. compile the published source code using the published build instructions into a binary
  3. compare the two binaries
  4. 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.