ABCore

Published:

Wallet Logo

This Android app currently has more than 1000 downloads and the latest release is version Varies with device.

Our last analysis was done on 2nd March 2020 based on data found in their Google Play description and their website and their source repository. Our verdict was Reproducible when tested (details below).

We found these ways of contacting the developers:

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 questionable coding practice. Nasa sends probes to space that crash due to software bugs despite a huge budget and stringent scrutiny.

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

This app is a full node for Android, so running it on your phone is probably not recommended unless you have unlimited data and don’t mind your phone down- and uploading GBs of data at a time.

The provider recommends not to use it as a wallet but to run it to back a wallet that allows setting custom full nodes.

On their Git repository there are no build instructions. Lets see how far we get:

The current version on Google Play is 0.76.

$ git clone https://github.com/greenaddress/abcore
$ cd abcore/
$ git checkout v0.76alphaPoC 
$ docker run -it --volume $PWD:/mnt --workdir /mnt --rm mycelium-wallet bash
root@455390a45b9d:/mnt# yes | /opt/android-sdk/tools/bin/sdkmanager "build-tools;29.0.2" # this might not be necessary
root@455390a45b9d:/mnt# ./gradlew -x test clean assembleRelease
root@455390a45b9d:/mnt# exit
$ mv app/build/outputs/apk/prod/release/app-prod-release-unsigned.apk .
$ sha256sum fromGPlay.apk # for future reference
c1ecc53c4d3ec880c57167b9e54cb81af3edf5c3088289a8d570f8c5f3717c44  fromGPlay.apk
$ apktool d -o fromBuild app-prod-release-unsigned.apk 
$ apktool d -o fromGoogle fromGPlay.apk 
$ diff --brief --recursive fromGoogle/ fromBuild/
Files fromGoogle/apktool.yml and fromBuild/apktool.yml differ
Only in fromGoogle/original/META-INF: ABCORE.RSA
Only in fromGoogle/original/META-INF: ABCORE.SF
Files fromGoogle/original/META-INF/MANIFEST.MF and fromBuild/original/META-INF/MANIFEST.MF differ

This looks good. This app is reproducible.

(As the provider doesn’t recommend using this app as a wallet and as it uses tons of resources, please investigate well if you want to use this as an actual wallet on your phone or maybe better only as a bitcoin full node on your Android TV.)

Verdict Explained

Reproducible when tested At the time of this analysis, the app on Google Play was reproducible from the code provided by the developers!

The app can be independently verified. If the provider puts your funds at risk on purpose or by accident, security researchers can see this if they care to look. It also means that inside the company engineers can verify that the release manager is releasing the app based on code known to all engineers on the team. A scammer would have to work under the potential eyes of security researchers. He would have to take more effort in hiding any exploit.

"Reproducible" does not mean "verified". There is good reason to believe that security researchers as of today would not detect very blatant backdoors in the public source code before it gets exploited, much less if the attacker takes moderate efforts to hide it.

To understand why some lines of difference are ok and others not one has to consider how app signing works. Android supports currently 3 signing schemes and in version 1 signing the signature is put inside the application file. As the tester must not have the release signing key, those files necessarily are missing or differ from the version on Google Play. The file "apktool.yml" was never part of the app and is generated by the analysis tool "apktool".