Help spread awareness for build reproducibility
Please help us spread the word, asking HODL Wallet : Bitcoin 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.
The Analysis ¶
Update: The developer closed the issue where we asked for help to verify the app build. There appears to be no interest in scrutiny.
The description sounds a bit scary:
Your Bitcoin are stored on your device and backed up to a Backup Recovery Key when you create a wallet. This means HODL Wallet can never stop you from accessing or sending your funds.
So they can’t stop me from sending my funds but can I stop them from sending my funds if they have a backup? Or what is this “Backup Recovery Key” again? I guess that’s just me being paranoid but this could be worded more clearly.
HODL Wallet is free, open source, and doesn’t require you to create an account.
That at least sounds great! :)
Choose to connect to your own node in advance settings
That’s great, especially if it doesn’t talk to a company server after that.
The website is more reassuring:
HODL Wallet does not collect any information at any point in time and all your Bitcoin exist exclusively on your device.
Also do we learn about it supporting the industry standard BIP39, menmonic backups.
Apparently hodl-wallet-android is their repository. It is MIT licensed, which is one of the most permissive licenses.
There, the build instructions are very minimal and involve Android Studio. Let’s see how it goes:
Go to github.co/hodlwallet/breadwallet-android and clone or download the project
Breadwallet? Ok, good to know where the code comes from but this alone lets us doubt a bit how dedicated the team is working on the project. Also: more guessing on our part:
$ git clone email@example.com:hodlwallet/hodl-wallet-android.git Cloning into 'hodl-wallet-android'... ... $ cd hodl-wallet-android/ $ git tag v2 $ git branch * develop
Not good. In the history we find no mention of
3.3.2 which would be the version name mentioned on Google.
Looking at the recent history though:
$ tig 2019-04-22 15:49 -0400 Igor Guerrero o [HEAD] Bump version to `3.3.3 2019-04-22 15:47 -0400 Igor Guerrero M─┐ Merge pull request #42 from 2019-04-19 16:33 -0400 Igor Guerrero │ o Bump version 2019-04-19 16:33 -0400 Igor Guerrero │ o Add hodlTestnet to the igno 2019-04-18 13:17 -0400 Igor Guerrero │ o Add error message when we d 2019-04-17 17:13 -0400 Igor Guerrero │ o Fix issue with Java not kno 2019-04-17 13:08 -0400 Igor Guerrero │ o Fix problem with regular pa 2019-04-02 11:28 -0400 Igor Guerrero o │ Add hodlTestnet to the igno 2019-04-02 11:27 -0400 Igor Guerrero o │ Bump version 2019-03-15 11:18 -0400 Igor Guerrero M─┤ Merge pull request #41 from [main] 475dc72f34fe410f567482a13fc0bd9784d2f2e8 - commit 3 of 2119 0% + versionCode 10 + versionName "3.3.2" multiDexEnabled true
we find 2 commits labled “Bump version” that both set the version name to “3.3.2”.
By the way, the wallet did not see an update since a long time. Those changes are from April 2019.
Anyway, the two “3.3.2” branches get merged on April 22nd, the day of the Google Play release. We’ll try that one:
394f23041b. We will raise the bar in the future and refuse to search for commits like that though. Have a tag or we can’t verify the build.
Anyway … we’ll try the same we tried with BRD:
$ git checkout 394f23041b $ git submodule update --init --recursive $ docker run -v $PWD:/mnt -it beevelop/cordova bash root@7d56c86f8fae:/# cd /mnt/ root@7d56c86f8fae:/mnt# yes | $ANDROID_HOME/tools/bin/sdkmanager "platforms;android-28" root@7d56c86f8fae:/mnt# /opt/android/tools/bin/sdkmanager ndk-bundle root@7d56c86f8fae:/mnt# ./gradlew :app:assemble ... BUILD SUCCESSFUL in 4m 7s
So lets compare it with the version from the Play Store:
$ apktool d -o fromBuild app/build/outputs/apk/hodl/release/app-hodl-release-unsigned.apk $ apktool d -o fromPlay ./appFromPlay.apk $ diff --brief --recursive fromBuild fromPlay Files fromBuild/AndroidManifest.xml and fromPlay/AndroidManifest.xml differ Files fromBuild/apktool.yml and fromPlay/apktool.yml differ Files fromBuild/lib/arm64-v8a/libcore-lib.so and fromPlay/lib/arm64-v8a/libcore-lib.so differ Files fromBuild/lib/armeabi-v7a/libcore-lib.so and fromPlay/lib/armeabi-v7a/libcore-lib.so differ Files fromBuild/lib/x86/libcore-lib.so and fromPlay/lib/x86/libcore-lib.so differ Files fromBuild/lib/x86_64/libcore-lib.so and fromPlay/lib/x86_64/libcore-lib.so differ Files fromBuild/original/AndroidManifest.xml and fromPlay/original/AndroidManifest.xml differ Only in fromPlay/original/META-INF: CERT.RSA Only in fromPlay/original/META-INF: CERT.SF Files fromBuild/original/META-INF/MANIFEST.MF and fromPlay/original/META-INF/MANIFEST.MF differ Files fromBuild/smali/co/hodlwallet/BuildConfig.smali and fromPlay/smali/co/hodlwallet/BuildConfig.smali differ Files fromBuild/smali/co/hodlwallet/presenter/activities/camera/CameraActivity.smali and fromPlay/smali/co/hodlwallet/presenter/activities/camera/CameraActivity.smali differ Files fromBuild/smali/co/hodlwallet/presenter/activities/settings/NodesActivity$1.smali and fromPlay/smali/co/hodlwallet/presenter/activities/settings/NodesActivity$1.smali differ Files fromBuild/smali/co/hodlwallet/tools/animation/BRAnimator.smali and fromPlay/smali/co/hodlwallet/tools/animation/BRAnimator.smali differ Files fromBuild/smali/co/hodlwallet/tools/manager/BRApiManager.smali and fromPlay/smali/co/hodlwallet/tools/manager/BRApiManager.smali differ Files fromBuild/smali/co/hodlwallet/tools/manager/BREventManager.smali and fromPlay/smali/co/hodlwallet/tools/manager/BREventManager.smali differ Files fromBuild/smali/co/hodlwallet/tools/manager/SyncManager$SyncProgressTask.smali and fromPlay/smali/co/hodlwallet/tools/manager/SyncManager$SyncProgressTask.smali differ Files fromBuild/smali/co/hodlwallet/tools/qrcode/QRCodeReaderView$DecodeFrameTask.smali and fromPlay/smali/co/hodlwallet/tools/qrcode/QRCodeReaderView$DecodeFrameTask.smali differ Files fromBuild/smali/co/hodlwallet/tools/qrcode/QRUtils.smali and fromPlay/smali/co/hodlwallet/tools/qrcode/QRUtils.smali differ Files fromBuild/smali/co/hodlwallet/tools/security/BRKeyStore.smali and fromPlay/smali/co/hodlwallet/tools/security/BRKeyStore.smali differ Files fromBuild/smali/co/hodlwallet/tools/security/BRSender$1.smali and fromPlay/smali/co/hodlwallet/tools/security/BRSender$1.smali differ Files fromBuild/smali/co/hodlwallet/tools/security/PostAuth$7.smali and fromPlay/smali/co/hodlwallet/tools/security/PostAuth$7.smali differ Files fromBuild/smali/co/hodlwallet/tools/security/PostAuth.smali and fromPlay/smali/co/hodlwallet/tools/security/PostAuth.smali differ Files fromBuild/smali/co/hodlwallet/tools/security/RootHelper.smali and fromPlay/smali/co/hodlwallet/tools/security/RootHelper.smali differ Files fromBuild/smali/co/hodlwallet/tools/sqlite/CurrencyDataSource.smali and fromPlay/smali/co/hodlwallet/tools/sqlite/CurrencyDataSource.smali differ Files fromBuild/smali/co/hodlwallet/tools/sqlite/MerkleBlockDataSource.smali and fromPlay/smali/co/hodlwallet/tools/sqlite/MerkleBlockDataSource.smali differ Files fromBuild/smali/co/hodlwallet/tools/sqlite/PeerDataSource.smali and fromPlay/smali/co/hodlwallet/tools/sqlite/PeerDataSource.smali differ Files fromBuild/smali/co/hodlwallet/tools/sqlite/TransactionDataSource.smali and fromPlay/smali/co/hodlwallet/tools/sqlite/TransactionDataSource.smali differ Files fromBuild/smali/co/hodlwallet/tools/threads/PaymentProtocolPostPaymentTask.smali and fromPlay/smali/co/hodlwallet/tools/threads/PaymentProtocolPostPaymentTask.smali differ Files fromBuild/smali/co/hodlwallet/tools/threads/PaymentProtocolTask.smali and fromPlay/smali/co/hodlwallet/tools/threads/PaymentProtocolTask.smali differ Files fromBuild/smali/co/hodlwallet/tools/util/Bip39Reader.smali and fromPlay/smali/co/hodlwallet/tools/util/Bip39Reader.smali differ Files fromBuild/smali/co/hodlwallet/tools/util/BRCompressor.smali and fromPlay/smali/co/hodlwallet/tools/util/BRCompressor.smali differ Files fromBuild/smali/co/hodlwallet/tools/util/BytesUtil.smali and fromPlay/smali/co/hodlwallet/tools/util/BytesUtil.smali differ Files fromBuild/smali/co/hodlwallet/wallet/BRWalletManager.smali and fromPlay/smali/co/hodlwallet/wallet/BRWalletManager.smali differ Files fromBuild/smali/co/platform/APIClient.smali and fromPlay/smali/co/platform/APIClient.smali differ Files fromBuild/smali/co/platform/kvstore/RemoteKVStore.smali and fromPlay/smali/co/platform/kvstore/RemoteKVStore.smali differ Files fromBuild/smali/co/platform/kvstore/ReplicatedKVStore.smali and fromPlay/smali/co/platform/kvstore/ReplicatedKVStore.smali differ Files fromBuild/smali/co/platform/middlewares/APIProxy.smali and fromPlay/smali/co/platform/middlewares/APIProxy.smali differ Files fromBuild/smali/co/platform/middlewares/HTTPFileMiddleware.smali and fromPlay/smali/co/platform/middlewares/HTTPFileMiddleware.smali differ Files fromBuild/smali/co/platform/middlewares/plugins/CameraPlugin$2.smali and fromPlay/smali/co/platform/middlewares/plugins/CameraPlugin$2.smali differ Files fromBuild/smali/co/platform/middlewares/plugins/CameraPlugin.smali and fromPlay/smali/co/platform/middlewares/plugins/CameraPlugin.smali differ Files fromBuild/smali/co/platform/middlewares/plugins/WalletPlugin$1.smali and fromPlay/smali/co/platform/middlewares/plugins/WalletPlugin$1.smali differ Files fromBuild/smali/co/platform/tools/BRBitId$2.smali and fromPlay/smali/co/platform/tools/BRBitId$2.smali differ Files fromBuild/smali/co/platform/tools/BRBitId.smali and fromPlay/smali/co/platform/tools/BRBitId.smali differ
Using diffoscope which also takes a deeper look at binaries we find:
├── AndroidManifest.xml (decoded) │ ├── AndroidManifest.xml │ │ @@ -1,9 +1,9 @@ │ │ <?xml version="1.0" encoding="utf-8"?> │ │ -<manifest android:versionCode="10" android:versionName="3.3.2" package="co.hodlwallet" platformBuildVersionCode="10" platformBuildVersionName="3.3.2" xmlns:android="http://schemas.android.com/apk/res/android"> │ │ +<manifest android:versionCode="11" android:versionName="3.3.2" package="co.hodlwallet" platformBuildVersionCode="11" platformBuildVersionName="3.3.2" xmlns:android="http://schemas.android.com/apk/res/android">
that the version differs, which tells us with certainty that the version in Google Play is not in GitHub:
We tried the last revision before the versionName was set to 3.3.3 which uses the versionCode 10. Google rejects updates with equal versionCodes, so this is kind of understandable and happened to all of us release managers but not committing a new revision and not tagging stuff is at least sloppy and as we hope will soon be unacceptable.
Which is a grave issue with verification though, are the differences in
lib/x86/libcore-lib.so. Those are 50MB in the diffoscope decompiled form and beyond human review.
That is not good enough.
Our verdict for now: not verifiable.
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
Published code doesn’t help much if it is not what the published app 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 app we can create and the app we can find on the app store 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.
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