How I hacked modern Vending Machines13th October 2018
“Hitting and kicking” the bundled App of their widest European distribution company.
Indisputably, Vending Machines are objects of cult. Delicious morsels of Hackers, always. In the beginning they worked offline with coins only, then, NFC- keys/cards models started spreading. If I say “COGES” I’m sure that better times will come to someone’s mind. But… In a bunch of years things changed radically. You distract and a moment after, find the world superseded by things connected to the internet…
One day I decided to interrupt seasoning myself in the bat-cave and direct to my hometown to get some sunlight, so I went to the University to salute an old professor.
“Go to have a coffee!” — he said— and we started chit-chatting while walking through the main corridor.
Me: “let me pay, I have coins!”.
Him: “wait wait! let me use the Vending Machine’s App to pay, the coffee will be cheaper”.
BLE + NFC
Brain: “Mmm… Virtual wallets are cool stuff. Well…”.
Soul: “I dare you to Hack into that!”
~$ White Hat inner voice: “just pats on the shoulder if no bug bounty reward”.
~$ Grey Hat inner voice: “ok, I’ll do that for educational purposes only”.
~$ Black Hat inner voice: “c’mon man, let’s screw that HEAP, great Jupiter!”.
Later in that day…
Needless to say that I picked up my dirty rooted Android smartphone, installed the targeted App from the Play Store and dumped the original *.apk to my laptop via adb.
# adb pull /data/app/com.sitael.vending-1/base.apk ./Argenta.apk
I decompiled the *.apk with apktool
# apktool d ./Argenta.apk ./Argenta
and extracted Java sources with jadx
# jadx ./Argenta.apk
Firstly, I made the *.apk debuggable by editing the AndroidManifest.xml file by adding android:debuggable=”true” property to the application
Then, I rebuilt the *.apk
# apktool b ./Argenta
created a new key with keytool
# keytool -genkey -v -keystore Argenta.keystore -alias Argenta -keyalg RSA -keysize 2048 -validity 10000
signed the *.apk with jarsigner using the generated key
# jarsigner -verbose -sigalg SHA1withRSA -digestalg SHA1 -keystore Argenta.keystore Argenta.apk Argenta
lastly, I zip-aligned it to make it runnable
# zipalign -v 4 Argenta.apk Argenta-signed.apk
and I installed the final *.apk
# adb install ./Argenta-signed.apk
I ran the App on the smartphone and I started looking at logs with logcat by filtering them via its package name
# adb logcat --pid=`adb shell pidof -s com.sitael.vending`
Nothing special found, so I started to comb through the source codes seeking for juicy informations.
Looking better at AndroidManifest.xml file, I found references to RushOrm
So, first keyword search was db_name
Cool. I booted the Root Explorer on the phone seeking for argenta.db
Found. So I pulled if to my laptop with adb
# adb pull /data/data/com.sitael.vending/databases/argenta.db ./db
and tried to open it with a DB Browser for SQLite
obviously, it was password protected
Step back to the source codes, looked at RushAndroidConfig.java
where I found the methods used to configure the database.
My attention was caught by this.encryptionKey = getDeviceId(context);
I moved to its definition and…
Found that the targeted App used the phone’s IMEI (*#06#)as encryption key for the SQLite database.
After a couple of seconds of inspection, I opened to the UserWallets table
and edited the walletCredit field writing changes
then I pushed the database with pumped credit back to the phone
# adb pull ./argenta.db /data/data/com.sitael.vending/databases/argenta.db
In the meantime, while I felt like “Robin Hood” (nostalgic and explicit reference to Age Of Empires cheat code for +1000 gold) I developed an Android utility to quickly dump/restore/tamper the targeted App’s database on the fly.
then I went back to my University again to finally test the Hack
From zero-credit account, I could:
> Inflate the App’s credit.
> Buy stuff.
> Get the remaining credit updated.
> Go back to zero-credit state.
> Inflate the credit again.
> Start over.
With a macro inspection of all the reversed sources I found huge portion of clean code — without obfuscation — that meant no great counter-measures adopted to protect user data and make the App secure at all.
A month ago…
The White Hat inner voice of me picked up the phone and called the company behind this shame to report the vulnerability. I gently suggested them to toss the current architecture and develop a better and secure one from scratch.
How I hacked modern Vending Machines was originally published in Hacker Noon on Medium, where people are continuing the conversation by highlighting and responding to this story.